Wing-Le Chan

Broadband parallel stubs phase shifter using defected ground structure

In this paper, a broadband phase shifter is presented and employs a defected ground structure (DGS) under parallel stubs. Compared with the one without DGS, the proposed design has a wider bandwidth, smaller size and with the very high impedance microstrip lines eliminated. For demonstration purposes, a novel broadband phase shifter using H shaped DGS was designed to operate over a frequency range from 2.2 GHz to 6.1 GHz. It was measured to have insertion loss and phase variation within 2.2 dB and 3.3deg over the desired frequency band.

Broadband Butler Matrix optimized using Jumping Genes Evolutionary Algorithm

A broadband Butler matrix with simple structure is presented, consisting of broad band rectangular patch hybrid couplers and novel broad band phase shifters using lambda/8 open and short stubs. Jumping genes evolutionary algorithm is employed to obtain the optimum design. It is measured to have a wide bandwidth of 35.6% centered at 3.65 GHz.

Broad band CBCPW phase shifter optimized with Jumping Genes Evolutionary Algorithm

A 45deg microwave phase shifter is optimized for broad band application using jumping genes evolutionary algorithm. The simple structure based on conductor backed coplanar waveguide structure eliminates the air bridges and via holes. The measured insertion loss and phase difference for the two paths are within 0.5 dB and 45degplusmn5deg, respectively, over the frequency band from 3.21 to 4.62 GHz. The measured return loss is found to be better than -10 dB over the operating frequency band.

Linearised 2 GHz amplifier for IMT-2000

Under large signal conditions, amplifiers using GaAs FETs have high input non-linearity due to the non-linear gate-to-source capacitance C/sub gs/ which will result in AM-PM distortion. The method presented uses a parallel connected varactor diode to linearise a GaAs FET amplifier. A reduction of 10 dB in spectral regrowth at 2 GHz is achieved with a low loss. This method is suitable for circuit miniaturisation and can be applied to amplifiers for IMT-2000.

Spectral regrowth of digital signal through an amplifier using a new linearity method

The AM/AM and AM/PM distortion are the dominate nonlinear behaviour of linear power amplifiers. The nonlinear transfer function of the amplifier is expressed as a power series to model the small nonlinear behaviour. Fourier transformation is used to analyse and interpret the origin of the spectral regrowth of digital signals. The amount of spectral growth is analysed using convolution and a new method is proposed which can reduce the spectral regrowth of the digital signal.