Volume 66, Issue 3-4

In this communication design and performance of a novel single-layer assembly of gap coupled elements in elliptical shape is proposed to achieve broadband performance with circular polarization. Out of five patches considered in this assembly, two pairs of patches having different patch areas are arranged close to an edge truncated elliptical patch. The central edge truncated elliptical patch is fed through inset feed arrangement and the other patches are parasitically gap coupled to the central patch. With such an arrangement, an improved impedance bandwidth of 1.58 GHz or 18.5% with respect to central frequency 8.5 GHz is achieved. Three resonant modes are excited with this arrangement giving improved bandwidth and gain in comparison to a conventional elliptical patch antenna with same semi-major and semi-minor axes. In the entire bandwidth, the simulated radiation patterns of proposed arrangement of patches are more or less identical in shape.

In this letter, a broadband coupler is presented that makes use of a half mode substrate integrated waveguide (HMSIW) technique using a printed circuit board process. The coupler is realized by a parallel HMSIW line which couples energy by magnetic field. Compared with microstrip coupler and conventional HMSIW coupler it has lower loss and better Electromagnetic Compatibility owning to the closed field structure. Compared with SIW coupler, it has smaller size and lower cost owing to the half TE10 model. Based on coupler, a two-way balanced power combining amplifier is designed and measured. The measured results show a good agreement with simulation and a combining efficiency of 88% is achieved at 9.7 GHz.

The aim of this study was to considered possible discrepancy in electromagnetic (EM) fascination in the human head. Commercially available software CST Microwave Studio based on the finite-difference time-domain (FDTD) method was adopted in this study. In this calculation, the conductivity and permittivity of all tissues were increased from 10 to 20% except using if not the same revelation conditions. Familiar cellular phone frequencies of 835, 900, and 1900 MHz were investigated in this research. The rise of up to 20% in conductivity, permittivity and varied substrate material always caused a SAR variation of 30.42% for SAR 1 g and 23.75% for SAR 10 g at 835 MHz, variation of 22.41% for SAR 1 g and 21.96% for SAR 10 g at 900 MHz and variation of 11.96% for SAR 1 g and 14.29% for SAR 10 g at 1900 MHz respectively.

This paper presents a novel current mode differential UWB LNA. A common-gate stage with transformer realizes a low noise input matching and produces a current gain. The output of the LNA is differential current, which can avoid the current-to-voltage conversion. The LNA is simulated with TSMC 0.18 μm RF CMOS process. Simulation results show that the max noise figure is only 2.65 dB, transconductance gain is larger than 18.7 dB, input reflection coefficient is lower than -9.9 dB, and third order input intercept point is about 2.8 dBm over 3–5 GHz. With a voltage of 0.8 V, the power consumption is 11 mW. A comparison with conventional UWB LNA shows that this LNA has advantages of low voltage, low noise, high gain, and high linearity.

In this paper, a novel current-mode differential transconductance low noise amplifier (LNA) designed in the chartered 0.18 μm CMOS technology is proposed to realize the receiver front-end. The proposed LNA frequency ranges from 4.7 GHz to 6 GHz,mainly targeting at IEEE802.11a application. It utilizes two stage structure, with a PMOS current-mirrorr using inductive series peaking technique to achieve optimized current output. The noise performance is improved through the use of a gm-boosting technique, while the gain performance is improved and power consumption is saved by using current-reused technique. Measured results demonstrate that the circuit provides flat transconductance gain higher than 17.0 dB, noise figure lower than 2.31 dB and low operating voltage of 0.85 V in frequency band. A comparison with other LNAs in similar and nearby frequency bands shows the proposed LNA has advantages of higher gain, lower noise figure and better other performances.

The capacity of multiple-input multiple-output (MIMO) wireless communication channels is affected by the multipath angle spread and relative multiple signal strength (RMSS) at both sides of the transmitter and the receiver. In this paper, we study analytically how these two factors emerge in the MIMO capacity equation when the channel state information (CSI) is unknown at the transmitter and perfectly known at the receiver. Mathematical expression for the channel capacity is carried out for 2×2 MIMO system and two propagation paths between the base station (BS) and the mobile terminal (MS) are considered. The proposed analytical model is verified through numerical results, which show that channel capacity increases with increasing angle spread. Also, as the relative strength of multipaths becomes larger, the better channel capacity is obtained.

The paper addresses the doubly iterative decoding of space-time turbo codes with a large number of transmit and receive antennas. In the doubly iterative scheme, the decoder uses preliminary soft values of the coded symbols and the soft estimates only for Quadratic-Phase-Shift-Keying (QPSK) modulation have been determined. In this paper we propose and explain the soft estimates related to the signal constellations for 8-PSK and 16-PSK modulations. The coding gains, given in dB, have been determined through simulations for two situations: without double iterations and for doubly iterative decoding for a number of 1 and 4 iterations, using 16 transmit and receive antennas, respectively showing the compromise between the spectral efficiency and the coding gain.

In this paper, we provide performance analysis of signal-to-interference ratio (SIR) based selection combining (SC) receiver, operating over correlated Weibull fading channels, with an arbitrary number of correlated co-channel interferers, over each branch. Assuming this multibranch diversity technique, infinite series expressions were derived for PDF (probability density function) and CDF (cumulative distribution function) of the output SIR. The proposed analysis was used for evaluating outage probability (OP). The effects of various system parameters, such as number of multiple interferers, correlation level and fading severity on the OP, are graphically presented. Another important system performance measure, average bit error probability (ABER) is efficiently evaluated for modulation schemes such as binary frequency-shift keying (BFSK) and binary differentially phase-shift keying (BDPSK).