A novel wideband MMIC voltage controlled attenuator with a bandpass filter topology

The theory, analysis, and systematic design guidelines for a novel wideband monolithic bandpass pi-network voltage controlled attenuator (VCA) are presented. A 24-32-GHz VCA was designed and manufactured using 0.15-mum GaAs pseudomorphic high electron-mobility transistor (pHEMT) technology. This is the first reported VCA to use a bandpass filter topology to achieve the required operating frequency band and eliminate the effects of parasitic capacitances of the pHEMTs. The bandpass filter absorbs the parasitic capacitances and thereby eliminates their detrimental effects. The measured attenuation dynamic range is 12 dB plusmn 0.5 dB with minimum insertion loss of 2-3 dB. The input power handling capability is up to 0 dBm. The VCA is well matched and may be placed in a 50-Omega system