ABSTRACT. We will present the design, measured performance and on-sky verification results of the production configuration Band 2 receivers for ALMA

ABSTRACT. We present the current design and performance of the ALMA Band 6v2 prototype receiver developed at NRAO as part of the Wideband Sensitivity Upgrade (WSU). The upgraded sideband-separating (2SB) SIS receiver extends RF coverage to 209–281 GHz and significantly expands the IF bandwidth. It increases from the legacy high-sensitivity range of 4 GHz to 14 GHz per sideband per polarization, covering a total IF range of 4–18 GHz. To meet the stringent Band 6v2 WSU requirements (e.g., single-sideband receiver noise temperature Trec,SSB<66 K max and image rejection IR > 15 dB over 90% of IF range), the receiver employs improved cryogenic optics, highly balanced 2SB mixer assemblies using Silicon-On-Insulator (SOI) Nb/Al-AlOx/Nb SIS junctions, and a new low-noise local oscillator system. Laboratory measurements of the key components demonstrate compliance with the Band 6v2 sensitivity and image-rejection requirements. To validate system compatibility, on-sky validation is planned on an ALMA antenna in Chile in April 2026.

ABSTRACT. We present the design and test results of a new 211- 275 GHz receiver for the LLAMA and AMT observatories. The receiver is built following the ALMA-style Cold Cartridge Assembly (CCA) architecture, allowing re-use of legacy com- ponents as well as test infrastructure. The frequency coverage corresponds to ALMA Band 6 which, apart from being an important astronomical band in itself, allows these observatories to participate in the Event Horizon Telescope (EHT) array, helping to fill existing gaps in the u-v plane.

ABSTRACT. Abstract--The Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences (CAS) is leading the construction of XSMT, a 15-m submillimeter-wave telescope to be deployed at a high-altitude site (4820 m) on the Qinghai–Tibet Plateau. XSMT is designed to operate over a frequency range of 80–500 GHz, with a possible extension to 690 GHz. Its primary science objectives include CII line-intensity mapping during the Epoch of Reionization, measurements of the kinematic Sunyaev–Zel’dovich effect in galaxy clusters, studies of the interstellar medium in the local Universe, and observations of transient events. The planned instrumentation comprises a 2 × 8 multibeam SIS receiver at 460 GHz, a three-band (230/345/460 GHz) MKID camera, and an imaging spectrometer covering the 230 and 345 GHz bands. XSMT is also expected to participate in the ngEHT in the future. This presentation will provide an overview of the telescope site, system design, and the current status of instrumentation development.

ABSTRACT. Terahertz technology plays a fundamental role in submillimeter astronomy. The use of the lowest noise detector technology allows for an efficient use of observing resources at any submillimeter observatory. Apart from terahertz detectors, high quality passive components as filters, polarizers, and optical components are required to process the sky signals with minimal information loss. In this talk we review the development of instrumentation for the APEX telescope, one of the best ground-based platforms for terahertz instrumentation.

ABSTRACT. Mini-CHAI is a single pixel, dual frequency, heterodyne receiver which will be installed at the CCAT obsevatory in the Atacama desert. It is a pathfinder for the 64-pixel instruments CCAT Heterodyne Array Instrument (CHAI) LFA and HFA [1] to study cryogenic and optical design concepts, tuning algorithms, control electronics, telescope interfaces and many other details. Mini-CHAI will cover the atmospheric windows around 490 and 810 GHz. It will undertake test observations in support of the large-scale mapping objectives of future multi-pixel array instrument and study point-like sources. It will also be used to verify the surface accuracy and mirror alignment of the telescope.

ABSTRACT. The Africa Millimetre Telescope (AMT) will be a sub-millimetre radio telescope in Nambia, observing in the frequency range 8 - 373 GHz. It will be able to observe both in a single dish mode, and as part of VLBI network such as the Event Horizon Telescope in multiple frequency bands simultaneously. Front-end will have low frequency part working in 8-22 GHz and high frequency part consisting of ALMA bands 1, 2, 6 and 7. The contribution describes the preliminary design of the AMT front-end, which includes optics in the cabin, and the cryostat with receivers. The requirement to simultaneously observe ALMA band 1 and 2, as well as band 2, 6 and 7, makes it a unique and complex optical design, consisting of several dichroic and mechanism and a challenging assembly integration and verification (AIV) program

ABSTRACT. The Submillimeter Array (SMA) has initiated on a new campaign of solar observations. A significant milestone has been reached with the successful detection of first fringes on a single baseline in December 2025. This paper outlines the preparatory steps undertaken to enable solar observing capabilities, including calibration strategies and system adjustments. Particular attention is given to the linearity of the SIS receivers, employing detuning techniques to accommodate the high brightness temperature of the sun. We conclude with a discussion on the prospects for solar science at millimeter and submillimeter wavelengths, highlighting the potential for high-resolution imaging and spectral diagnostics.

ABSTRACT. We demonstrate the equivalence between the thermal and electrical models describing the Hot-Electron Bolometric (HEB) mixer with negative differential resistance (NDR). Because of this, a practical approach to NDR device stability, developed for resonant-tunneling diodes (RTD), can be applied to superconducting HEBs (and other Transition-Edge Sensors - TES). As a result, the constraints on the mixer bias conditions are formulated in both analytic and graphical forms.

ABSTRACT. In this paper, we report on the characterisation of 3.4-THz In0.22Ga0.78As anti-parallel Schottky diode mixers. Mixers were characterized in two configurations: Fundamental, where both radio-frequency (RF) and local-oscillator (LO) signals are coupled to the diode through a pyramidal horn. And, as an 8th harmonic mixer pumped by a 600-GHz LO multiplier chain.

ABSTRACT. Waveguide structures for a sideband-separating receiver operating in the 211–275 GHz and 300–375 GHz bands were developed using finite element simulations. The main goals of the optimization were to ensure manufacturability with relatively large milling tool diameters (100–150 μm) and to achieve low reflection in the waveguide hybrid, not exceeding –25 dB over 90% of the operating bandwidth. We present the measurement results for a fabricated sideband-separating block covering the 211–275 GHz band, demonstrating an average sideband rejection of no less than 10 dB across the entire range. The results of this work can be applied directly in the development of the onboard instrumentation for the space observatory Millimetron. In addition, they will be utilized for future Russian submillimeter ground-based telescope.

ABSTRACT. In this work, the IF impedance of the superconductor-insulator-superconductor tunnel junction in 1.1-1.4 mm double sideband mixer was measured experimentally and calculated numerically. It was shown that the IF reflection can vary from -30 to -5 dB depending on the bias voltage and the pumping power. An experimental method for determining the impedance of the SIS mixer was proposed and tested.

ABSTRACT. Abstract— The SEPIA receiver at the APEX telescope provides a possibility to use ALMA cartridge receivers for single-dish observations. The SEPIA receiver (Swedish ESO PI Instrument for APEX) accommodates 3 receiver cartridges. Currently, it is ALMA Band 5 prototype receiver cartridge, SEPIA345 receiver cartridge (GARD designed receiver to cover ALMA Band 7 and having 4-12 GHz IF band) and NOVA developed ALMA Band 9 with 2SB receiver configuration. In this abstract, we present design of the cartridge receiver that will replace the current SEPIA345 and has all new optical and mechanical layout, featuring extra-wide IF 4-18.5(20) GHz with new 2SB mixers and OMT-based dual polarization capability. I. INTRODUCTION The SEPIA receiver (Swedish ESO PI Instrument for APEX) [1] was installed at APEX telescope in 2015 and opened up a possibility to observe in a single-dish mode with ALMA Band 5 receiver prototype cartridge. At a later time, NOVA instrumentation group provided a new receiver cartridge operating in ALMA Band 9 receiver band but equipped with 2SB mixers. In 2020, Group for Advanced Receiver Development, GARD, installed the third receiver cartridge that covered ALMA Band 7 RF band with 2SB mixers and provided 4-12 GHz IF band, dual-polarization performance via OMT [2]. All three receiver channels were used for routine single-dish observations at APEX while SEPIA345 receiver was used also for the EHT observations. The science requirements for the next generation of receivers for ALMA [3] and ngEHT demand a threefold to fourfold increase of the IF bandwidth leading to the IF band being effectively as wide as up to 4-20 GHz. With this work, we present the design of the ngSEPIA345 receiver cartridge that operates in 270-375 GHz RF band, employs the 2SB mixers [4] with extended IF bandwidth 4-18.5 GHz and uses OMT [5] to provide dual polarization capability. The ngSEPIA345 receiver cartridge is designed to keep full compatibility with ALMA Band 7 cartridge interfaces. II. THE RECEIVER CARTRIDGE DESIGN The ngSEPIA345 receiver cartridge uses the standard ALMA receiver cartridge body consisting of 300K flange plate and 110K, 15K and 4K temperature plates separated by fiberglass spacers. The 300K plate provides the mechanical interface to the ALMA cryostat and also interfaces to the ALMA Band 7 warm cartridge, which delivers the LO signal to the mixers and carries the warm part of IF chain, and DC bias unit (ALMA standard DC bias unit is used). The cartridge has three independent internal electrical transport chains: LO transport, IF signal transport chain and DC bias harness. The LO transport chain consists of WR8 vacuum feedthroughs, one for each polarization, and mounted at 300K plate, stainless steel WR8 waveguides connecting the feedthroughs and the x3 VDI Inc. multipliers mounted at the 110K; the multipliers’ WR2.8 output is connected to the straight WR10 oversized waveguides via adapters. The straight WR10 waveguides go directly to 4K plate where the adapter WR10-to-WR2.8 connects the LO to the final link made of copper WR2.8 waveguides [6] connected to the mixers’ LO inputs. The IF cables are made from two sections, with a split at the 15 K temperature stage, to allow for easier assembly of the cartridge. The DC cabling uses constantan wires and has integrated heat-sinks to control thermal flow. The cartridge optics is the same as in the previous generation of the SEPIA345 cartridge [2] with two offset elliptical mirrors and the corrugated horn [7] though with a modified mechanical layout that accommodates the new OMT- 2SB-mixers package. The 2SB mixers follow the design presented in [4]. The OMT has built-in twist and configuration with the two outputs in its opposite sides; this allows using two completely identical 2SB mixers. The IF amplifiers [8] are directly connected to the mixer IF outputs. In the design of the ngSEPIA345 receiver cartridge, we largely used experience of designing, constructing and producing ALMA Band 5 receiver cartridge [9] and ALMA Band 2(+3) receiver cartridge [10]. In particular, to facilitate the cartridge assembling and production, the IF cables are split in two sections allowing pre-assembling of the cartridge up to particular thermal stage, similar to ALMA Band 5 design. Likewise, the integration of the corrugated horn, OMT and two identical 2SB mixers largely follows the successful implementation of the ALMA Band 5 design and minimizes the length and insertion RF loss of the connecting waveguides. The magnetic coils are identical to those used for the ALMA Band 5 receiver. The LO transport employs straight WR10 waveguides, ALMA Band 2(+3), that simplifies assembling, reduces the risk of trapped modes by avoiding the oversized waveguide bends and optimizes the costs. The thermal links of the WR10 largely employ the design implemented in the ALMA Band 2(+3) receiver cartridge. During the Conference, we plan to present the further details of the ngSEPIA345 receiver cartridge design and show results of the initial performance tests that partly will be presented in [11]. III. ACKNOWLEDGEMENTS This work was initialized, supported and funded by Onsala Space Observatory, Chalmers University of Technology. We would like to acknowledge Yebes Observatory, Spain for providing the state-of-the-art 4-20 GHz cryogenic low-noise amplifiers. J. Adema and M. Bekema, NOVA NL, are sincerely acknowledged for their help in acquisition of the fiberglass spaces for the ALMA cartridge body. R. Ahlman and R. Hammargren, Onsala Observatory Technical Support Group, are acknowledged for fabricating parts for test setup and the ngSEPIA345 receiver cartridge. REFERENCES [1] V. Belitsky, et.al., “SEPIA – a new single pixel receiver at the APEX telescope”, A&A 612, A23 (2018), https://doi.org/10.1051/0004- 6361/201731458 [2] D. Meledin, et al., “SEPIA345: A 345 GHz dual polarization heterodyne receiver channel for SEPIA at the APEX telescope,” A&A, Volume 668, December 2022, https://doi.org/10.1051/0004-6361/202244211 . [3] J. Carpenter, D. Iono, L. Testi, N. Whyborn, A. Wootten, N. Evans, “THE ALMA DEVELOPMENT ROADMAP”, (AKA ALMA 2030), on-line https://www.almaobservatory.org/wpcontent/ uploads/2018/07/20180712-alma-development-roadmap.pdf [4] I. Lapkin et.al., “Development and Performance of the SIS 2SB Mixer for RF Band 210-375GHz”, to be presented at ISSTT2026. [5] I. Lapkin et al., "Wideband OMT for the 210–373 GHz Band With Built- In 90° Waveguide Twist," in IEEE Transactions on Terahertz Science and Technology, vol. 15, no. 2, pp. 151-157, March 2025, doi:10.1109/TTHZ.2024.3499734. [6] The copper WR2.8 waveguides were manufactured by Oshima Inc., Japan. [7] The corrugated horn was fabricated by Thomas Keating Ltd, UK [8] Isaac López-Fernández, et.al., “Ultra-wideband Cryogenic Low Noise Amplifiers: a Cool and Crucial Component for Future Submillimetre Radio Telescopes,” Telescopes and Instrumentation, ESO Messenger 191, 2023, DOI: 10.18727/0722-6691/5340 [9] V. Belitsky, et.al., “ALMA Band 5 Receiver Cartridge: Design, Performance and Commissioning”, A&A, Volume 611, March 2018, https://doi.org/10.1051/0004-6361/201731883 [10] V. Belitsky, et.al., “ALMA Band 2 Cold Cartridge Assembly Design”, in the Proceedings of the ISSTT2022, Baeza, Spain, October 16-20, 2022 https://www.nrao.edu/meetings/isstt/papers/2022/20220027.pdf [11] E. Sundin et.al., “A beam measurement system for cartridge-type cryogenic receivers”, to be presented at ISSTT2026.

ABSTRACT. The study of the origin and transport of water in the universe is an important part of the scientific program of the Millimetron space observatory. This will be made possible by observations conducted in single-dish mode using an onboard instrument - the High Resolution Spectrometer (HRS). This instrument incorporates heterodyne array receivers operating within the range 0.5 − 2.7 THz, comprising 3-pixel arrays of superconductor-insulator-superconductor (SIS) mixers operating at frequencies below 1.3 THz for V and H polarizations and 7-pixel matrix receivers based on NbN HEB mixers observing above 1.9 THz for single polarization. HRS The spectrometer will consist of seven main units. An optical unit for matching the receivers with the secondary Cassegrain mirror and frequency-separating the spectrometer channels. Two heterodyne units — for channels M1-M3, based on Schottky barrier diode multipliers, and for channels M5-M7, based on quantum cascade lasers. Two heterodyne detector units, M1-M3 and M5-M7. An IF signal formatter unit with an ADC and FPGA, and a control electronics unit with autonomous memory. The article will present of the current status overview of the development for the main units used in the HRS instrument of the Millimetron space observatory.

ABSTRACT. We report the development of a SPDT and SP3T set of Schottky-based voltage-controlled switches able to cover the 164 – 167 GHz and 174.8 – 191.8 GHz with > 40 dB isolation between the closed and the opened switch paths. An insertion loss between the receiver port and the alternative possible paths is better than 1.5 and 1.8 dB in SPDT and SP3T, respectively. The switches integrate a total of six and nine discrete Schottky diodes in a FinLine based chip structure. The return loss in all ports is better than 20 dB in the desired frequency bands, and the switching time is estimated below 1 ns.

ABSTRACT. We report the development of a Monolithic Microwave Integrated Circuit (MMIC) based on Schottky Barrier Diodes (SBD). This circuit defines a single-chip frequency tripler able to accommodate four SBD anodes to handle up to 75 mW RF input power in the 340 – 385 GHz frequency range. A conversion efficiency better than 4 % allows for > 2 mW RF power in the 1010 – 1160 GHz frequency range. Peak power above 3 mW is expected at ~1020 - 1080 GHz. The number of anodes, their dimensions and their electrical properties, are chosen to avoid electron speed saturation. The thermal modeling accounts for the thermal shift experienced by the electrical properties of diodes under high power operational conditions

ABSTRACT. We report the observation of discrete and reproducible suppression quanta of the Josephson supercurrent in superconductor-graphene-superconductor (SGS) Josephson junctions under near infrared (NIR) illumination. The stepwise supercurrent response is robust against variations in photon wavelength, illumination power, bath temperature, and dc bias current. Remarkably, nearly identical step spacing is observed in junctions with different graphene channel lengths, indicating that the characteristic suppression quantum is governed predominantly by the superconductor-graphene interfaces rather than by transport within the graphene channel. In contrast, the discrete steps disappear in the negative differential resistance regime, where dissipative quasiparticle transport dominates. These results reveal a quantized supercurrent response associated with effective Cooper pair tunneling cycles in SGS junctions and highlight the central role of interface limited dynamics in graphene based superconducting nanodevices.

ABSTRACT. This paper presents two planar components for integrated heterodyne receiver operating at 220 GHz, a directional coupler and a rat-racing type power divider. Both components are implemented basing on microstrip line (ML) and are highly desirable for constructing a large format multi-pixel array at mm and sub-mm wavelength. The details about the design of coupler and divider are described. Simulated and measured results based on the membrane technology are also shown and discussed.

ABSTRACT. This paper presents a ray-tracing and physical-optics (RT-PO) model for the efficient analysis and design of hybrid domes integrated with array antennas to achieve wide-angle multibeam coverage. The hybrid dome combines the dielectric lens and the metadome, leveraging their complementary advantages to extend the scanning range of array antenna while maintaining a relatively lightweight and wideband design. The proposed RT-PO model not only alleviates the high computational cost of such electrically large structures but also synthesizes the required array excitations for multibeam generation via a reverse RT technique. A hybrid dome targeting dual-beam radiation at 40° and 80° is designed to validate the proposed model. The results demonstrate its effectiveness for the efficient analysis and design of hybrid domes for wide-angle multibeam arrays.

ABSTRACT. Superconductor-insulator-superconductor (SIS) mixers are essential components in sub-mm heterodyne receivers, offering quantum-limited sensitivity. This work presents the numerical design and modeling of an SIS mixer array for a 125-211 GHz receiver, a candidate for future ALMA Band 4+5 receiver. Circuit-level analysis is performed to optimize the embedding impedance for wide RF as well as IF bandwidth up to 20 GHz. The mixer performance is evaluated with a tri-frequency approximation based on Tucker theory to estimate the conversion gain. Ongoing fabrication and experimental characterization are expected to further validate the proposed design.

ABSTRACT. In this work, we present a transmissive all-dielectric metasurface half-wave plate (HWP). The unit cell consists of three stacked elliptical dielectric pillars, for the 330–365 GHz band. Each elliptical pillar is modeled as an equivalent circular dielectric rod whose propagation constant is obtained from a characteristic equation. A cascaded transmission–line model then yields S-parameters and differential phase Δϕ for two orthogonal components. The model enables fast numerical evaluation prior to validation in full-wave simulation. The resulting 330–365 GHz design achieves ~180° phase retardance with |S_11 | < −10 dB and |S_21 | > −1.5 dB across the band. The framework can target arbitrary phase shifts for other polarization-control devices and frequency bands.

ABSTRACT. As satellite constellations continue to expand, specifically in low Earth orbit (LEO), with its inherently huge amount of satellites being deployed, the risk of radio frequency interference (RFI) with radio telescopes also arises. In this situation, filtering of unwanted signals becomes crucial. In this work, we propose an interdigital bandpass filter designed for future additive manufacturing as a monolithic piece. This type of filter provides a wider spurious-free range, allowing the mitigation of signals coming from downlink satellite communications. The filter has been designed for a passband between 31.8-39 GHz, as an example of frequencies used in radio astronomy.

ABSTRACT. AliCPT1 is a CMB telescope for B-mode search located at Xizang, China. The telescope focal plane is designed with 19 6-inch detector modules. The AliCPT1 IHEP group is developing these detector modules using both transition edge sensors (TES) and thermal kinetic inductance detectors (TKID) with identical architecture. Each module consists of 456 pixels and 1824 detectors covering 90/150GHz and two linear polarizations. The TES array has been successfully fabricated with a deep silicon etch release yield of 96%. The transition temperature uniformity is studied. The TKID pixel has been measured and the array is under fabrication.

ABSTRACT. A monolithic metal-only high-gain antenna comprised of a geodesic H-plane horn and an integrated metallic E-plane hyperbolic lens is designed to be manufactured with laser powder-bed fusion additive manufacturing (LPBF-AM). A truncated H-plane horn is used to create a focused beam in the H-plane, whereas the non-dispersive hyperbolic metallic E-plane lens creates a focused beam in the E-plane. The integration of these two allows for the generation of a high-gain pencil beam. Design considerations include an operation frequency from 50 to 70 GHz, with a realized gain above 30 dBi, a reflection coefficient below −10 dB, and an insertion loss of 1.5 dB. The use of a ray-tracing and physical-optics model allows for a time efficient design of the geodesic H-plane horn feed. Moreover, the use of the full wave solver CST for the modeling of the E-plane lens and the integrated design demonstrated that the simulated antenna achieves these design considerations, reaching a realized gain of 31 dBi at the center operating frequency of 60 GHz. The promising high gain and low loss of this design concept warrants further optimization and study for fabrication of a final prototype.

ABSTRACT. This work develops a reproducible workflow for the simulation and optimization of microwave components used in radioastronomy. Using iterative electromagnetic simulations coupled to a fitness-driven optimizer, the study focuses on designing a quadrature hybrid for the 80–110 GHz band, targeting an outgoing power near −3 dB and minimal amplitude imbalance between ports (ΔA). Preliminary results are consistent with prior commercial-solver designs, identify and mitigate artifacts such as spectral leakage, and demonstrate the feasibility of accelerating searches with multiprocessing. The project is ongoing and will extend to metamaterial modeling and antenna-filter optimization in future stages.

ABSTRACT. The ALMA observatory in Chile is an interferometer consisting of 66 antennas, with 10 frequency band specific receivers, that act together as a single telescope. Four series of up to 70 (66 and spares) high quality and reliable receivers are required, which can only be achieved when a special work attitude is adopted. Major implications are there for the design of the receivers, the ordering of the parts, the inspection of all components and for the optimization of the assembly and test procedures. This work will highlight some of the lessons learned on this topic, experienced during the production of CCA Band 9, Band 5, Band 2 and the WCA Band 2.

ABSTRACT. Receivers based on the superconductor-insulator-superconductor (SIS) tunnel junction are one of the most sensitive heterodyne systems for detecting submm and mm-band waves. In this work, we present numerical simulation results and preliminary SIS mixers designs at 345 GHz and 800 GHz. The mixers include a RF probe, filters, tuning structures, contact pads on a quartz substrate. The developed designs sensitivity to major technological deviations in dimensions and parameters is evaluated. The prototype receiving elements under development have the potential to be used in future astronomy projects like the Millimetron observatory.

ABSTRACT. We propose a spinning interferometer for radio astronomical applications. The antenna element positions are optimized to produce a point-like synthesized PSF with low side lobe levels. An example array design with 36 elements is presented obtaining the targeted PSF characteristics.

ABSTRACT. This work presents a compact CMOS antenna-coupled terahertz detector based on monolithic integration of a Planar Inverted-F Antenna (PIFA) and a source-coupled NMOS transistor. An antenna–detector co-design approach is employed, where the PIFA is engineered to efficiently couple incident radiation into the transistor channel. Operating in its fundamental quarter-wavelength resonance mode, the PIFA enables significant miniaturization of front-illuminated terahertz sensors compared to conventional half-wavelength patch-based designs. Full-wave electromagnetic and circuit-level simulations in 65-nm CMOS confirm effective conversion of incident radiation into a DC output for resonant detector designs between 400 GHz and 500 GHz.

ABSTRACT. We present a methodology to measure the complex permittivity of material slabs at D-band. The setup is based on a vector network analyzer with frequency extenders, and the permittivity estimation uses the Nicolson-Ross-Weir algorithm in combination with the multi-line through-reflect-line calibration method. The method is tested on the permittivity measurements of low-, medium- and high-contrast material slabs of various thicknesses, demonstrating good repeatability.

ABSTRACT. Photonic radiometers that upconvert RF signals to the optical domain offer an alternative to conventional microwave and terahertz receivers, particularly for small satellite platforms where size, weight, and power consumption (SWaP) are critical constraints. This paper presents the architecture and design of a photonic radiometer payload for CubeSat integration, realized using photonic integrated circuits (PICs). The RF-to-optical upconversion is performed on a Whispering Gallery-Mode Resonator (WGMR) fabricated in a Thin-Film Lithium Niobate (TFLN) PIC, enabling room-temperature operation without the need for cryogenic systems. The payload comprises three main functional blocks: an optical signal generation unit based on an indium phosphide (InP) PIC, a TFLN-based upconverter block containing the WGMR, and a control electronics block implemented on printed circuit boards (PCBs). This architecture substantially reduces the SWaP of the payload, making it wellsuited for next-generation nanosatellite missions.

ABSTRACT. We design a 2.7-THz dual-polarized antenna in a new configuration that feeds four hot-electron bolometers (HEBs) through coplanar-waveguide (CPW) transmission lines. The antenna performance is modeled using COMSOL Multiphysics, and its far-field beam pattern is analyzed when combined with an elliptical lens. The resulting dual-polarized, quasi-optical HEB mixer is suitable for supra-THz frequencies (>1 THz), as required for spaceborne heterodyne receivers to improve signal-to-noise ratio.

ABSTRACT. We present on the development of calibration strategies for the next generation Very Large Array (ngVLA). The ngVLA is the planned large scale interferometric array that will be primarily based in the American Southwest and will include outlying sites across the United States, Mexico and Canada. The continental sized baselines available to the array, combined with a densely populated core, will enable ngVLA to be an order of magnitude more sensitive than the current VLA, while being able to achieve sub-milliarcsecond-resolution. Temporally variable water vapor in the troposphere will introduce delay error to observations made with ngVLA. Calibration of this delay error is essential for the ngVLA to meet its science requirements.

ABSTRACT. Receiver requirements derived from science use cases for future sub-mm radio telescopes drive the need for novel receiver architectures. Increased receiver instantaneous bandwidth is one key requirement that can be delivered by using a Zero-IF receiver architecture. This receiver architecture is now becoming a suitable option for sub-mm radio telescopes due to the ongoing progress made in semiconductor technology. Advantages of Zero-IF architecture are compared to the traditional, SIS based, sideband-separating heterodyne scheme for this application and a strawman design concept is presented.

ABSTRACT. ALMA’s primary function is to observe and image the Universe at millimetre and sub-millimetre wavelengths with unprecedented sensitivity and angular resolution. ALMA is now approaching completion of all its originally planned receiver bands and has largely achieved its fundamental science goals. To define a consistent and future-oriented plan for maintaining ALMA at the forefront of astrophysical facilities, the project published the ALMA Development Roadmap. This document introduces three new fundamental science drivers: the origin of galaxies, the origins of chemical complexity, and the origin of planets. These drivers set a new long-term development strategy in which the main priorities for the coming decade are an increase of the receiver IF bandwidth by at least a factor of two and the associated upgrade of the electronics and correlator.

The Wideband Sensitivity Upgrade (WSU) consists of increasing the instantaneous spectral bandwidth by as much as a factor of four while retaining full spectral resolution over the entire bandwidth, leading to spectral scan-speed gains of up to a factor of 50 at the highest spectral resolution. In addition, an upgrade of the full signal chain of ALMA - from the receivers and digitizers to the correlated data - will result in sensitivity improvements for all observations. Achieving these upgrades while continuing operations with the legacy system introduces significant technical challenges.

The Laboratoire d’Astrophysique de Bordeaux (LAB), which made major contributions during the original ALMA construction through the delivery of the Back-End digitizers and the Tunable Filter Bank of the correlator, has since led ESO-funded development studies to identify technological and architectural solutions for a second-generation instrument. In this context, LAB has proposed a Wideband IF Processor (WIFP) for the ALMA 2030 instrument. The principal goals of the WIFP work package are to design, build, manufacture, assemble, and integrate with the ALMA Telescope the digitizers, supporting digital signal processing and clock generation, and total-power detection.

The main enhancements brought by the WIFP are direct digitization of the receiver IF bands, removing the second analog frequency conversion and simplifying the analog back end; an increase of instantaneous bandwidth through higher-frequency sampling; and improved sensitivity through higher digitization and quantization resolution. The signal-chain functions covered by the WIFP include analog signal conditioning, digitization, digital signal processing, and optical transmission.

ABSTRACT. This work presents a simulation-based analysis of the effect of mechanical defects on split-block waveguide assemblies and their mitigation using a holey Mirror Half-Turn metasurface. Our findings show an improvement of more than 13 um mechanical robustness for circular waveguide systems at room temperature, and more than 16 um when cryogenic temperatures are considered.

ABSTRACT. We have phase locked a 4.7 THz quantum cascade laser (QCL) to a microwave reference signal using a novel GaAs/AlAs super-lattice diode as a harmonic mixer operated at room temperature. The signal above the noise level is 20 dB, observed for a 0.4 GHz beat signal between the 24th harmonic of a 198.4 GHz reference source and the 4762 GHz signal of a QCL. A phase-locking loop with 10 MHz bandwidth allows locking of 80% QCL emission power to the reference source. Using the beat signal, we have also characterized both the power and frequency of the QCL versus the bias voltage with a high accuracy.

ABSTRACT. This work presents a hybrid MMIC receiver concept for a 3 mm spectropolarimetric camera, combining a dual-polarization optical front end with InP low-noise amplification and SiGe-based frequency conversion. The receiver is designed as a compact, scalable pixel, with expected performance including noise temperatures of 20–30 K at 100 GHz, total gain of 22–27 dB, and high polarization purity. Development and fabrication will be carried out at the CePIA-UdeC laboratory.

ABSTRACT. Millimeter-wave waveguide components underpin front-end instrumentation, yet conventional CNC machining becomes costly and slow as geometries grow more complex, or iteration cycles shorten. We present an advanced additive manufacturing (AM) workflow for fabricating metallic rectangular-waveguide circuitry with mmWave performance and rapid turn-around, based on laser powder bed fusion (LPBF). The approach targets compact, assembly-light waveguide architectures and enables features that are challenging to realise with subtractive methods (internal transitions, or polarization-control elements). We validate the process experimentally in Q-band and F-band by manufacturing representative waveguide test structures and benchmarking the S-parameters with simulations. As a functional demonstrator, we additionally fabricate and measure a waveguide iris polariser, showing that AM can reproduce polarisation-transforming circuitry with controlled phase behavior. These results indicate that high-resolution AM, combined with appropriate post-processing and metrology, is a viable route to scalable mmWave waveguide hardware and fast design iteration for receiver and subsystem development.

ABSTRACT. We give here an overview of the plans of the JAO spectrum management office for monitoring of RFI at the ALMA operations sites.

ABSTRACT. We report on the fabrication of SIS mixers using silicon-on-insulator (SOI) technology. The latter enables the implementation of substrates with arbitrary geometries, giving greater flexibility in mixer design in order to improve detection performance and/or enable the implementation of complex mixer configurations. We will present the fabrication process of high current density and sub-micron SIS Nb/Al-AlOx/Nb junctions using SOI substrates that we are currently optimizing.

ABSTRACT. We report on progress towards a 4-pixel focal plane array module to fit within the existing ALMA Band 4 cartridge using SIS MMICs. An initial, coarse optics investigation will be presented, along with a preliminary consideration to managing the IF stage.

ABSTRACT. Subterahertz electronics is a technological enabler for the further progress of wireless communications and remote sensing. The manipulations with amplitudes and/or phases of signals propagating in free space are of particular interest. In this paper, we report on a free-space signal modulator operating at 140 GHz. The modulator is designed as a GaAs monolithic device based on a unit cell utilizing log-periodic reflective antenna loaded with a varactor. Calculations and measurements are conducted to assess the impact of the material properties on the amplitude and phase control capabilities of the developed design.

ABSTRACT. Measuring the voltage-dependent receiver noise temperature (TrecDSB) of a hot-electron bolometer (HEB) is essential for characterizing the mixer, as it identifies not only the minimum TrecDSB but also the optimal bias voltage. Such measurements are particularly important for MgB₂ HEBs, which exhibit structure in their voltage-dependent IF-power characteristics. Obtaining reliable voltage-dependent TrecDSB requires a local oscillator (LO) with constant amplitude throughout the measurement. In this work, we demonstrate a new measurement method that enables accurate bias voltages scans while using only the HEB itself for LO stabilization with optional direct detection correction.

ABSTRACT. The TU Delft/SRON team has recently demonstrated a quasi-optical NbN HEB mixer at 1.63 THz, which uses for the first time a Si metalens to couple the THz radiation to the spiral antenna. The experiment shows a DSB receiver noise temperature of 1800 K and a power coupling efficiency of 25 % between the metalens and the spiral antenna. To understand the measurements, especially the efficiency, we present an analysis based on the metalens focusing efficiency, and several terms of different efficiencies describing power coupling between the lens aperture and the antenna. The latter aspects are based on COMSOL finite element simulations.

ABSTRACT. Kinetic inductance travelling-wave parametric amplifiers (KTWPAs) have been demonstrated in the microwave regime as effective candidates for applications requiring broadband, quantum-noise-limited performance. When extended to the millimetre-wave regime, KTWPAs have the potential to serve as first-stage amplifiers for astronomical heterodyne receivers. However, when operated in a four-wave mixing (4WM) configuration, the pump tone required for KTWPA amplification lies near the centre of the operational bandwidth. This leads to several undesirable effects: interaction with the local oscillator (LO) tone of the heterodyne receiver and the generation of spurious harmonics; degradation of the radio-frequency (RF) tunability of the heterodyne mixer; and practical difficulties in filtering out the pump tone prior to the receiver. By contrast, under DC biasing, a KTWPA can be operated in the three-wave mixing (3WM) regime, in which the pump frequency lies outside the signal band and can therefore be efficiently filtered. In this work, we present a preliminary design concept for a DC-biased 3WM KTWPA operating in the W-band, highlighting its suitability as a low-noise pre-amplifier for millimetre-wave heterodyne detection systems.

ABSTRACT. Successful production of NbTiN-Al/AlOx/NbTiN tunnel junctions by the standard fabrication method for Nb/AlOx/Nb junction does not seem possible as a consequence of the allegedly higher surface roughness of NbTiN, which would cause shorts or weak links through the thin (1nm) insulating layer. We report about NbTiN-Nb-Al/AlOx/Nb SIS junction where we use the Nb interlayer as a thin buffer layer and show that a uniform tunnel-barrier is formed. It is also shown that the gap voltage of the tunnel junctions decreases with decreasing buffer layer thickness. A possible increase of the gap for a thin buffer layer, by the underlying NbTiN layer by proximity effect, has not been observed

ABSTRACT. Based on the wideband waveguide diplexer design for combining signal almost seamlessly across E-band and W-band to cover 62 – 117 GHz, an alternative approach to realize ultra-broad dual-band receiver to cover >52% RF bandwidth is proposed. The approach is suitable for the band-combining upgrade for the existing heterodyne receivers of the millimeter-wave telescopes. Compared to the existing band-combining ultra-broad bandwidth receiver, this approach preserves most of the existing receiver components.

ABSTRACT. This poster presents the recent work of the THERA group at Paris Observatory. It will describe our work on Schottky technology for planetary or Earth observation missions, as well as work on different aspects of heterodyne array receivers with superconducting mixers for astronomical instruments.

ABSTRACT. Large, lightweight primary optics are a key enabler for space-based observatories where space, weight, power, and cost (SwaP-C) are critical. Previous work has investigated the creation of passive metamaterial lenses that operate in the 100s of GHz range that are lightweight as a result of being very thin, and are reflection-coated, allowing for high efficiency. It is important, however, to understand the interplay between various specifications of such lenses, such as: the diameter, the focal length, the operation frequency, the bandwidth, the thickness, and the metamaterial layer count. In order to study these, we have create a mathematical model for GRIN lenses that is able to relate these characteristics and allows for the investigation of trade-offs between them.

ABSTRACT. We present an automated tuning algorithm that simultaneously optimises magnetic field and SIS bias voltages for the 455 - 495 GHz balanced and 800 - 820 GHz single-ended mixers of the CCAT Heterodyne Array Instrument Precursor (mini-CHAI) to provide stable, low noise performance, which enables remote operation on the Fred Young Submillimeter Telescope (FYST).

ABSTRACT. We present a study on the feasibility of diagnosing reflector surface errors in crossed-Dragone (CD) telescopes using amplitude-only holography based on multiple intensity beam maps. The method is developed within the framework of the full phase ‘multi-map’ holography technique [1] for FYST [2], with the phase information omitted and only intensity beam measurements retained for the surface inference. Using the near-field measurements of a 400-mm CD antenna and corresponding simulations, we show that large- and medium-scale surface deformations of both reflectors can be reconstructed from sets of on-axis and off-axis beams. In this approach, the surface errors of the two reflectors of CD telescope are parameterized using circular Zernike polynomials. We assess parameter correlations and study the optimal measurement configurations using a sampling-based inference procedure, finding that increasing the number of beam maps and the separation of the detectors in the focal plane significantly reduces uncertainties in the recovered surface modes. These results indicate that amplitude-only holography provides a practical approach for routine optical diagnosis of large crossed-Dragone telescopes using standard astronomical receivers or detector arrays and enables studies of telescope deformations induced by gravity at different elevation angles as well as by thermal effects.

ABSTRACT. Simulations of quasi-optical systems using the physical optics method of equivalent surface currents are a key tool in the design of millimeter and submillimeter-wave astronomical telescopes and instruments. A recently developed open-source software package, PyPO, implements this method using both CPU and GPU-accelerated based calculations. In the paper, we compare the performance of PyPO to TICRA GRASP, a long-standing commercial software package for these calculations, using the Submillimeter Array antenna and imaging beam-waveguide as a test case.

ABSTRACT. Space-Earth very large baseline interferometer (VLBI) is one of the key scientific modes of the Millimetron Space Observatory. It will provide the opportunity for space observations with extremely high angular resolution, including matter close to the event horizon of supermassive black holes. Millimetron VLBI instrument is a heterodyne multichannel receiver including 7mm, 3mm, 1.3mm and 0.8mm channels. In the article the design of VLBI instrument optics is presented, which allows simultaneous multifrequency observation in all bands. The initial considerations of the design are given, quasi-optical analysis results as well as electromagnetic simulation results are presented. Key features of the design are a combination of Dragone conditions optics synthesis and quasi-optical Gaussian analysis along with multi-channel bandsplitting design, which all together provide excellent symmetry of beam pattern and low cross polarization for all frequency bands

ABSTRACT. In this work, we propose and design a wide steering multi-beam geodesic lens antenna with feeds placed in a straight line. Having the feeds in a straight line eases the integration with electronics at high frequencies. The design of the lens is inspired by other dielectric designs based on quasi-conformal transformation optics. The lens produces beams within a 48 deg range with low scan losses.

ABSTRACT. This paper introduces a dielectric collimating truncated virtual image lens antenna operating from 26 to 40 GHz that provides radiation properties similar to those of a Luneburg lens antenna. The use of the collimating truncated virtual image lens avoids the fabrication constraints of realizing a unity refractive index at the periphery. The proposed lens is implemented using a quasi-periodic structure with a face-centered cubic lattice arrangement, which is selected for its superior isotropy and frequency stability. A prototype is fabricated using fused deposition modeling. Measurement results demonstrate stable radiation patterns throughout the operating band, with a reflection coefficient remaining below -12 dB and a realized gain exceeding 24.6 dBi. These results verify that the proposed lens is a practical and efficient solution suitable for millimeter-wave applications.

ABSTRACT. In this study we characterize copper tellurium and aluminum CNC micro-milled rectangular waveguides for the 750 1100 GHz frequency band. The Hammerstad-Bekkedal model is applied to extract the effective surface roughness, and predict the degradation in effective conductivity at terahertz frequencies. Copper tellurium samples show mid-band attenuation constants better than 1.2 dB/cm, while aluminum samples (1.6 dB/cm) highlight the need for additional surface coating.

ABSTRACT. We present a room-temperature continuous-wave terahertz source that bridges the 1–12 THz gap using efficient difference-frequency mixing in optically thin nonlinear metasurfaces with a giant second-order nonlinear response. By quantum-engineering intersubband transitions in a semiconductor heterostructure processed into an array of subwavelength nanoresonators, we realize a metasurface with effective second-order nonlinearity for difference-frequency generation on the order of 〖10〗^6pm/V. The metasurface enables continuous-wave THz generation and we demonstrate µW-level THz power output using two mid-infrared pump lasers with optical powers in the range 100–200 mW. We demonstrate broadband tunability, including operation within the Reststrahlen band of III–V semiconductors, and outline routes to increase THz output power to the mW level while maintaining Hz-level linewidth. Finally, we show how the metasurface complements FET detectors to enable a fast, widely tunable, room-temperature source-detector-system.

ABSTRACT. In this conference, we aim to present the measured noise temperature performance of a single-ended double sideband (DSB) twin-junction superconductor-insulator-superconductor (SIS) mixers with broad radio frequency (RF) bandwidths combining Atacama Large Millimeter/sub-millimeter Array (ALMA)-defined Bands 6 plus 7 (211-373 GHz). Our design prioritizes consistent fabrication and high yield in anticipation of future applications in sideband-separating configurations. Notable technological developments in our mixer chips are silicon-on-insulator (SOI) substrates and gold beam leads. We incorporate a modular intermediate frequency (IF) matching circuit fabricated on printed circuit board (PCB) immediately following the RF chip to broaden the IF bandwidth. We will discuss in greater depth the mixer design, fabrication process, experimental setup, and preliminary experimental results.

ABSTRACT. Next-generation communication systems require high-gain antennas with wide-angle scanning capabilities as specific requirements will increase and higher performance will be required. To extend the scanning range of planar phased array antennas (PAAs), a proposed solution is to integrate them with dielectric radomes designed with lens functionality, which enhance the gain at wide scan angles. In this study, a radome comprising three dielectric layers is designed to enhance the main lobe directivity of a PAA at 60 degrees, while preserving the directivity at broadside. The impact of the radome on directivity is analyzed using an efficient in-house two-dimensional ray tracing physical-optics tool, which significantly shortens simulation time compared to commercial full-wave simulators. Simulation results demonstrate that the integrated dielectric dome yields a directivity enhancement of 1.83 dB at 60 degrees while preserving the directivity at broadside and maintaining low sidelobe levels. Furthermore, directivity improvement is observed across the majority of the 0 to 60 degree range, with none of the angles had a directivity loss greater than -1 dB.

ABSTRACT. This paper describes a process to realize quasi-vertical diodes (QVDs) with integrated capacitor structures for biasing and RF tuning. The fabrication process is described, in addition to measurements to characterize the diode structure. By incorporating a bias connection directly into the diode’s ohmic contact, thus separating the diode from ground with a dielectric, it is possible to independently apply a bias to different diodes in multi-diode circuit configurations, such as mixers and frequency triplers. Prototype diodes with integrated capacitors are fabricated and characterized with on-wafer measurements up to 220 GHz.

ABSTRACT. Schottky-diode-based heterodyne receivers remain among the best non cryogenic solutions for detecting molecular spectra in millimetre and submillimetre wave range (300,5000 GHz). Reducing the anode size, which is required to increase the cutoff frequency of Schottky diodes operating in the upper-THz range, introduces significant fabrication challenges. Achieving a reproducible, reliable, high-performance contact with dimensions below 0.1 µm² remains a major challenge in microelectronics and requires the use of electron-beam lithography. In this context, using the fabrication of the diodes for a subharmonic frequency mixer operating over 1960–2120 GHz as an example, we detail the methods used to form these contacts and to ensure metal interconnections through metallic air bridges. We also discuss the improvements implemented in the MMIC circuit.

ABSTRACT. In this work we demonstrate that SIS mixer frequency response can be measured by a Fourier Spectrometer using the mixer intermediate frequency (IF) output signal. For SIS mixer incorporated into a heterodyne receiver this approach can provide a better signal-to-noise ratio compared to a standard DC measurement. We show theoretically and experimentally that the spectrum measured via the IF output consists of the squared mixer response function, a second harmonic component, and a spectral feature at the IF frequency. This modified spectrum represents the autocorrelation of the mixer response function shifted by the IF frequency. We demonstrate that the original frequency response function can be restored from these data, providing an alternative method to characterize receiver response.