FPGA implementation of multiplierless M-QAM modulator

Adaptive multilevel QAM (M-QAM) modulation can increase throughput in a wireless packet data network. A technique is discussed for efficiently realising M-QAM modulators on field programmable gate arrays (FPGAs) using 'multiplierless' finite impulse response (FIR) filters with carry-save addition and canonic signed-digit coefficients. An adaptive M-QAM modulator supporting 4, 16, 64 and 256-QAM is presented     

Broadband electronically tunable microstrip ring resonator filterwith negative resistance coupling

Broadband electronically tunable filters can be realised using varactor tuned ring resonators with negative resistance coupling. Broadband matching circuits must be used for negative resistance realisation and for compensating the input and output impedance variation with frequency. Circuits and simulated results for a two section 1.3 to 2.1 GHz silicon varactor tuned 50 to 70 MHz bandwidth ring resonator filter are presented     

High Aspect Ratio Vertical Cantilever RF-MEMS Variable Capacitor

An electrostatically actuated, microwave microelectromechanical system variable capacitor fabricated using deep X-ray lithography is presented. A single exposure has been used to produce the novel high aspect ratio microstructure, which includes a thin, vertically oriented, movable nickel cantilever beam and a 40:1 vertical aspect ratio capacitance gap. The 0.8-pF capacitor operates in the 1-5GHz region and has Q-factors of 36 at 4GHz and 133 at 2 GHz. The variable capacitance ratio is 1.24:1 over a 20-V tuning range at 4GHz     

Microstrip-fed high aspect ratio dielectric resonator antenna with dual-resonance broadband characteristics

A simple and broadband, microstrip-fed high aspect ratio dielectric resonator antenna is presented and fabricated. The broadband characteristic is achieved by merging the resonances of two appropriate modes of the antenna. The measured antenna bandwidth can exceed 16% with dielectric constant of 25. The approach provides stable radiation patterns as well as low cross-polarisation levels over the entire bandwidth.