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

The design and analysis of a novel wideband, monolithic, bandpass, 71-network, voltage controlled attenuator (VCA) is presented. A 24 to 32 GHz VCA was developed using 0.15μm GaAs 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 12dB ± 0.5dB with minimum insertion loss of 2-3dB. The input power handling capability is up to 0dBm. The VCA is well matched and may be placed in a 50Ω system (Halabi, 2004).