Design of MMIC Voltage Variable Attenuator for T/R Module of Phased Array Radar

The design and simulation of a novel 5.4-5.8 GHz MMIC voltage variable attenuator (VVA) using 0.25 µm Gallium Arsenide (GaAs) pseudomorphic High Electron Mobility Transistor (pHEMT) is presented in this paper. The proposed attenuator can be used in transmit/receive (T/R) module of phased array radar. Output power of transmitter of T/R module can be controlled as per requirements. It can also be used in an Automatic Gain Control (AGC) circuit of a frontend radar receiver to prevent its saturation. A novel technique using negative feedback in a two-stage cascaded topology is employed in this attenuator circuit to achieve necessary attenuation range. The attenuator achieves a minimum attenuation of around 3.39 dB and a maximum attenuation of around 42 dB with a control voltage of −2.5 V to 2 V while maintaining S11 & S22 below −10 dB. Also, Noise Figure of this attenuator is below or equal to its attenuation values at all specified control voltages.