Volume 65, Issue 5-6

This article presents a fractal-shaped broadband balun based on the lumped-element composite right/left-handed transmission line (CRLH TL). The developed balun involved there –90° Koch-shaped microstrip branches and one +90° CRLH branch, features compact, excellent transmission performance and bandwidth enhancement. Closedform formulae for broadband strategy and general guide lines for fractal implementation are derived. For verification, a balun operated at 1.5 GHz is designed, fabricated and measured. Consistent results between simulation and measurement has validated this concept as well as the developed equations. The fabricated balun, with an occupied area of 17.7 × 24.8 mm 2 corresponding to 12% of the area that its conventional counterpart occupies, exhibits a relative bandwidth of 93.3% ranging from 1.03 to 2.43 GHz. Across this frequency region, the return loss is better than 10 dB while the amplitude and phase imbalance varies within 1 dB and 4.2° respectively.

A compact microstrip low pass filter has been designed using step impedance technique. Two slots were cut in the ground plane just below the high impedance microstrip lines. The proposed filter has spurious free response for wide band width with sharp cut-off characteristics. The filter has been designed for a cutoff frequency 2.5 GHz and provides good agreement between the simulated and measured results.

A novel single-feed circularly polarized (CP) microstrip antenna (MPA) is presented. Capacitive disk coupling feed is used in the proposed antenna. With a resistor load connecting with another capacitive disk at the opposite position, CP radiation over a wide frequency band is realized. Experimental results show that the fabricated antenna has a –10 dB impedance bandwidth of 36.5%, and a 3-dB axial ratio (AR) bandwidth of 15.5% at the center frequency 2 GHz, and owns feature of low profile (0.67 λ × 0.47 λ × 0.0402 λ ). This antenna can be used in occasions when wide CP performance and compactness is desired.

A lower power multi-modulus programmable divider is designed in this paper. The TSPC (True Single Phase Clock) Technology is used and the TSPC D flip-flop with an AND gate embedded is designed, which significantly lower the power dissipation of the programmable divider. It is designed by Cadence in Chartered 0.18 μm CMOS process, simulated under condition that the supply voltage is 1.8 V, and the frequency of input signal is 1.8 GHz. The simulation result shows that this programmable divider can operate well with achieving multi-modulus frequency dividing from 128 to 254 with step of two. And the whole power dissipation is 3.27 mW from a 1.8 V supply. The designed programmable divider has good stability and low power, and it is easily to expand the range of dividing ratios. It is very suitable for the application of the high stability frequency synthesizer in wireless communication system.

This paper presents the design of two types of magnetron injection guns (MIG's) for 1 MW, 127.5 GHz gyrotron. TE 24,8 mode has been chosen as the operating mode. In-house developed code MIGSYN has been used to estimate the initial gun parameters. The electron trajectory tracing program EGUN and in-house developed code MIGANS have been used to optimize the single-anode and the double-anode design for 80 kV, 40 A MIG. The parametric analysis of MIG has also been presented. The advantages and the disadvantages of each kind of configuration have been critically examined.

This paper analyzes the effect of the insufficient synchronization (carrier frequency offset, timing offset) on hexagonal multicarrier transmission (HMT) systems for doubly dispersive channel. Exact SINR and demodulated symbol expressions for HMT systems in the presence of insufficient synchronization transmission conditions over doubly dispersive channel with exponential delay power profile and U-shape Doppler power spectrum and uniform delay power profile and uniform Doppler power spectrum are derived, respectively. Theoretical analysis shows that similar degradations on symbol amplitude and phase caused by insufficient synchronization are incurred as in traditional cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM) transmission. HMT systems outperform traditional OFDM systems with respect to signal to interference-plus-noise-ratio (SINR) against inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by insufficient synchronization and doubly dispersive(DD) channel. The BER performance of the HMT systems using Monte Carlo simulation match with the conclusion given by the proposed exact SINR expression.

In this paper, outage probability and spectral efficiency of opportunistic and incremental relaying coded cooperation are investigated. Two protocols are considered, i.e., parallel coding and partial repetition coding. The impact of exchange ratio (i.e., the ratio of the period of first phase to the whole transmission period) on these two adopted measurement metrics is analyzed. We also derive approximate expressions for the outage probability at high SNR (signal to noise ratio) regime to reveal the diversity order. Computer simulation validates our analysis finally.

In this work, an extensive design study of a stacked U-slot microstrip patch antenna for dual band operation will be presented. This antenna consists of two stacked microstrip patches, both having U-slots embedded in them. Two feeding techniques namely probe-feeding and co-planar waveguide feeding have been used and the results compared. The antennas were simulated using CST Microwave Studio's Transient Solver which is based on the Finite Integral Technique (FIT) and particle swarm optimization was used to optimize the antenna parameters for both the cases. The simulated and measured results indicate that using co-planar waveguide feeding results in a tremendous increase in bandwidth when compared with probe feeding, however degradation in gain is observed.