ABSTRACT. this paper describes some of the most important design considerations such as: transistor and substrate selection for high power, matching network design and stabilization of microwave power amplifiers with discrete die transistor in X-band frequency. According to these considerations, a 30- watt power amplifier with a GaN-HEMT transistor over 8.8 to 9.8GHz has been designed and fabricated. The power gain, power added efficiency and 1dB compression point of the fabricated circuit are 9.2dB, 53 percent and 29.1watt respectively. Due to the self-heating issue of high power transistors, electro thermal operation of transistor should be well-thought-out, hence the transistor attached on a high thermal conductivity carrier and biased under pulsed condition. The measurement results show good agreement with simulations.

ABSTRACT. Abstract—This paper presents a design for 1- 6 GHz low noise amplifier (LNA) based on cascade GaN HEMTs with LC ladder input matching and stabilizing output impedance. The designed LNA is simulated using Advanced Design Software (ADS) based on a commercial packaged transistor from Cree Inc. The LNA shows a maximum noise figure of 2.95 dB in the 1-6 GHz range with a gain of 14 dB. It also has a maximum S 11 of -2.4 dB, an input IP3 of 29.4dBm and is unconditionally stable over the whole bandwidth while drawing 13 Watts of DC power. The designed LNA also shows high linearity with more than 60 dBc carrier-to-intermediation distortion.

ABSTRACT. In this study, a new method of design for dual band matching network is presented. A transformer-less Band Pass (BP) prototype matching network is synthesized with well-known Simplified Real Frequency Technique (SRFT) via cascaded combination of Low Pass (LP) and High Pass (HP) sections and optimized under LP to BP frequency transformation to create dual band response. Scattering parameters based descriptive functions of transformer-less BP prototype network is obtained. Dual band response is derived via frequency mapping on the produced BP prototype network. The new method combines several advantages both in design and realization step. The application of this method is discussed with sequential transformation based approach. A dual band matching network design for a PIFA antenna is presented. By using this method dual band characteristic is derived with only one step application of frequency mapping which let use to have more practical realizations.

ABSTRACT. The reliability issue of dielectric charging in MEMS capacitive switches is discussed taking into account the present knowledge derived from the numerous papers on this topic. The weakness of the available charge injection model is pointed, the dependence of the material stoichiometry with film thickness resulting in lateral charge redistribution is discussed, the available assessment techniques are presented and the discharge process through the dielectric film is analyzed.

ABSTRACT. This paper presents a jitter correction circuit for high-speed clock signals. The circuit corrects the jitter error in the location of the rising and falling edges of the clock pulses. The proposed circuit topology employs delay units and time selection window to ensure a jitter-free output clock signal. The number of corrected edges of the clock signal is equal to the number of edge correction units.

ABSTRACT. In this paper, influence of different substrates’ thickness on coplanar waveguide (CPW) inductors for high frequency applications is presented. The designed CPW inductors are two-port meanders with one turn and outer dimension 1.8 mm × 2.0 mm. CPW inductors were made in inkjet printing technology with nanoparticle ink which contain 20 wt% of silver. CPW inductors are fabricated on substrates with 25, 50, 75 and 125 μm thicknesses. The measured response characteristics are in excellent agreement with the predicted simulation response. The best values of inductance and Q-factor were obtained with 125 μm thickness of substrate (L=2.269 nH and Q5).

ABSTRACT. A wideband antenna operating at a very high-frequency (VHF) band is presented in this communication. The antenna consists of two quad antenna (Biquad). Gain of around 5 dB of this antenna are demonstrated; narrower beam widths and a further increase of gain can be achieved using a reflector. For further increase of gain and beam width in azimuth some passive elements are used. Simulated results show that it’s operating bandwidth ranges from 125 to 210 MHz with the voltage standing wave ratio (VSWR) less than 1.5 and a good radiation pattern of 11.5-dBi average gain and bandwidth of more than 40% is earned. To validate the design a wideband modified bi-quad antenna system is fabricated and tested. Measured results of a full-scale prototype fabricated with aluminum wipe are in good agreement with simulated ones, which demonstrates the antenna's potential applications in VHF communication systems.

ABSTRACT. A new uni-planar compact electromagnetic band-gap (EBG) structure is presented. The proposed EBG unit-cell is designed based on the stepped-impedance resonator (SIR) technique. Results show that the proposed EBG structure provides a wide frequency bandgap around the 60 GHz band. Moreover, results show that the proposed EBG unit-cell has further miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uniplanar compact (UC-EBG) structures, respectively

ABSTRACT. Design and analysis of millimeter-wave (MMW) mushroom-like, circular-patch electromagnetic band-gap (EBG) structure is presented. The in-phase reflection and band-gap characteristics of the proposed EBG structure are investigated. Results show that the proposed EBG structure has stable reflection properties when normally and obliquely illuminated by a plane wave with different polarizations around the 60 GHz band. In addition, the proposed EBG structure is found to have a band-gap around the same frequency bandwidth. With these properties, proposed EBG structure is suitable to be used as reflectors in antenna applications in order to increase the gain and improve the radiation characteristics.

ABSTRACT. This paper presents the analysis and design of new planar slot array antenna with reduced back radiation for secondary surveillance Radar (SSR) application. Feed network for sum and difference beams with hybrid phase shifter and branch line coupler are implemented. A backfill antenna is designed and used to improve coverage of difference pattern in back of antenna. The effects of vital parameters on antenna performance and some other details are analyzed and discussed as well. The proposed antenna, designed on standard RO4003 substrate with 0.8mm thickness. This antenna fed by microstrip corporate feed network. The fundamental parameters of the antenna such as bandwidth, return loss, gain, and radiation pattern are obtained. The antenna operates in frequencies of 1.03GHz and 1.09GHz with the gain of about 16.5dB for the sum pattern with 3dB beam width of 10.5 ̊ in azimuth and 65 ̊ in elevation plane. The proposed antenna has better 12dB return loss in frequency range. Moreover, the physical size of the antenna is 1.85 × 0.55 × 0.08m3.

ABSTRACT. Wireless Networks-on-Chip (WiNoCs) have emerged to solve the scalability and performance bottleneck of conventional wired NoC architectures. However unlike communication in the macro-world, on-chip communication poses several constraints hence, hence there is the need for simulation and design tools that consider the effect of the wireless channel at the nanotechnology level. In this paper, we present a parameterizable channel model for WiNoCs which takes into account practical issues and constraints of the propagation medium, such as transmission frequency, operating temperature, ambient pressure and distance between the on-chip antennas. The proposed channel model demonstrates that total path loss of the wireless channel in WiNoCs suffers from not only dielectric propagation loss (DPL) but also molecular absorption attenuation (MAA) which reduces the reliability of the system.

ABSTRACT. Efficient finite difference time domain (FDTD) implementation of the modified Lorentz dispersive models is presented. The formulations, which are based on the current J-E auxiliary differential equation (ADE) scheme, unify the FDTD implementation of the frequently used dispersive materials with the minimal additional storage requirements. In addition, the stability of the formulations maintains the conventional non-dispersive FDTD constrain. Numerical tests are included to show the validity of the presented formulations.

ABSTRACT. A second harmonic mixer appropriate for direct conversion recievers is realized in 0.18 µm SiGe technology. The realized topology offers a unique mechanism to prevent LO to RF leakage, thus, suppress the DC Offset voltage due to LO self mixing. The constant current consumption of the topology provides a proper isolation of the noise mixing operation from the supply lines. Large signal analysis of the topology is presented and the dependence of the conversion gain on the biasing conditions is investigated. Measurements are acquired to verify the conversion gain gathered from the analysis and the simulation results. According to measurement results, the conversion gain of the circuit is 35 dB and the second harmonic of LO to RF leakage is less than 70 dB.

ABSTRACT. The potential utility of real-time handheld microwave imaging systems is significant in wide range of applications including nondestructive testing of aerospace composites. In such applications, monostatic imaging systems, where the structure-under-test (SUT) is inspected from one side using transceiver antenna arrays for irradiation and reception as well, are highly desired. This stems from the fact that access to both sides of the SUT is commonly limited in practice and monostatic imaging systems yield higher resolution than bi-static systems. To realize a monostatic system, a directional coupler is typically used to drive each antenna array element with the illuminating wave which impinges upon the SUT, and also delivers the reflected wave to the receiver for detection. Due to the space limitation in typical imaging arrays, the size and weight of the utilized directional coupler become critical for the realization of handled imaging systems. Many of the conventional directional couplers cannot fulfill the size requirement or otherwise show weak coupling and/or isolation coefficients at high frequencies. In this paper, we present a miniaturized 3D directional coupler design on multi-layer printed circuit board (PCB), which satisfies the size requirement and has a good performance in terms of coupling and isolation coefficients at 24 GHz.

ABSTRACT. A compact reconfigurable band-notched UWB antenna is presented in this paper. The antenna has a partial ground plane with a rectangular slot to achieve the desired bandwidth for UWB from 3.1GHz to 12GHz. The antenna has a single band-notch frequency which is achieved using a switched U-shaped slot, inserted in the radiating patch. This slot is used to decrease interference with WIMAX applications from 3.3GHz to 3.9GHz. The switching reconfiguration of the proposed antenna is achieved through two ideal switches. The antenna inhibits two modes of operation, which result from controlling the switch on/off. The proposed antenna has VSWR < 2, except the WIMAX band, as desirable. The proposed antenna design has been fabricated and tested. Measurement results show very good agreement with simulation results.

ABSTRACT. A frequency tunable resonator topology is proposed that consists of an S-shaped resonator, a ground frame and a feeding transmission line. Tunability is achieved by using reverse biased varactor diodes employed at critical locations on the structure. As well as being a tunable resonator, the structure also provides tunable metamaterial properties. Reflection and transmission parameters, electric and magnetic field distributions, and permittivity and permeability at each tuned frequency were analyzed and shown. Simulation and measured results agree well and demonstrate about 28% frequency tunability.

ABSTRACT. This paper presents experimental investigation of excised human skin tissue material parameters by THz Time Domain Spectroscopy in the band 0.1 - 2.5 THz. The results are applied to evaluate the channel pathloss Nano-electromagnetic communication. Refractive index and absorption coefficient values are evaluated for dermis layer of the human skin. The results presents the effect of hydrated tissue on channel parameters and provide the optimum distance with can be utilized for effective communication inside the human skin.

ABSTRACT. A multiple-input-multiple-output (MIMO) ultra-wideband (UWB) antenna with planar structure and a compact size is presented in this paper. It consists of two modified slot antennas excited by microstrip transmission lines. An inverted U-shaped slot is inserted in the feeding transmission line to create a band-rejection at the WLAN (5.15–5.825 GHz) band. The isolation between the two antenna elements is enhanced by introducing T-shaped slot and a rectangular slot between them. The rectangular slot reduces the coupling at lower frequencies i.e. 3-5 GHz while T-shaped slot maintains good isolation at higher frequencies i.e. 5-10.6 GHz. The proposed antenna has a bandwidth of 7.5 GHz and operates from 3.1-10.6 GHz. It occupies a space of 22 x 26 〖mm〗^2 and achieves a minimum isolation of 20 dB between its antenna elements over the whole operating band. The small size, good isolation and better radiation characteristics of the proposed antenna make it suitable candidate for UWB diversity applications.

ABSTRACT. Two CPW fed band-notched antenna are presented. In the first antenna by using four CSRRs(Complementary Split Ring Resonators) and a MLs(Meander Lines) on the patch and the feed line, band notched features are obtained in 5.4 GHz - 6.5 GHz for WLAN, 7.2 GHz- 8 GHz for partial C-band and 8.5 GHz-10.4 GHz for X-band. The presented antenna consists of a square patch which has four CSRRs in four different sides and a feeding line with a ML. The ground of the second proposed antenna includes six MLs which lead to different and multiple band notched. Total size of each antenna is 50*50 mm2 . Out of rejection band for both antennas in the input bandwidth frequencies where S11 10dB, the VSWR is less than 2.

ABSTRACT. A novel compact dual-band stop frequency selective surface (FSS) for shielding GSM application is proposed. The aim of this design is to block the 900/1800 MHz GSM signals transmitted by mobile phones from entering certain buildings such as mosques, hospitals, embassies, etc. without disturbing other type of communication systems. The proposed FSS design consists of a modified double square loop with folded strips into the inner space at the four corners of both square loops to control both resonant wavelengths of the band stop filter. As a result, the unit cell area is reduced to 0.11 λ, where λ is the free-space wavelength associated with the lower resonant frequency, achieving more than 34% size reduction in the unit cell area as compared to the existed designs in the literature at the same GSM resonant frequencies (GSM 900 and 1800 MHz). So, this will allow a limited area to accommodate more number of periodic FSS elements, also will isolate the desired resonances from grating effects. Furthermore, the proposed design shows a stable frequency response for the angles of incidence ranging from 0 to 60° with shielding efficiency of more than 20 dB at 900 and 1800 MHz mobile bands for both the transverse electric (TE) and the transverse magnetic (TM) polarization.

ABSTRACT. This paper presents a miniature planar UWB microstrip patch antenna for breast cancer detection. The antenna can be placed on the breast skin to detect any possible breast tumors. Both simulation results and experimental measurements show good agreement for the return loss of the fabricated antenna in the UWB range from 4.23GHz to 11.71GHz. The antenna gain was found to vary from 2.25dBi to 4.55dBi over the operating band with 96% average radiation efficiency. Simulation results also indicate that the current density inside the tumor is about eight times higher when the antenna is placed in direct contact with the breast, compared to when it is placed 5 cm or 15 cm off the breast. Hence, the sensitivity of developed antenna for detecting breast tumor increases when the fabricated antenna is in direct contact with the breast skin.

ABSTRACT. This paper focuses on the modelling of communication channel noise inside human tissues at the THz band (0.1-10THz). A novel model is put forward based on the study of the physical mechanism of the channel noise in the medium, which takes into account both the radiation of the medium and the molecular absorption from the transmitted signal. The derivation and the general concepts of the noise modelling is detailed in the paper. The results show that the channel noise power spectral density at the scale of several micrometres is at acceptable levels and the value tends to decrease with the increase of both distance and frequency. In addition, the channel noise is also related to the composition of the human tissues, with the result of higher channel noise in tissues with higher water concentration. The conclusion drawn from the conducted study and analysis paves the way for more comprehensive characterisation of the electromagnetic channel within in-vivo nano-networks.