Design of Low Noise, High Dynamic Range and Triple-Band MMIC Voltage Variable Attenuator Using 0.25 μm GaAs pHEMT Technology.

This paper proposes the design of 1.2-1.3 GHz, 2.5-3 GHz and 5.4-5.8 GHz MMIC voltage variable attenuator (VVA) realized using 0.25 μm GaAs pHEMT technology. It is a wideband voltage variable attenuator as it covers entire radar frequency bands. It provides a minimum attenuation of 2 dB in L and S-Band and 3 dB in C-Band and maximum attenuation of 72 dB in L-Band, 60 dB in S-Band and 47 dB in C-Band with attenuation flatness of 3 dB in L and S-Band and 1 dB in CBand. The phase response of the attenuator is also shown in this paper. The attenuator is perfectly matched with source and load impedances. It shows full-band stability. By convention, noise figure is equal to attenuation. The novelty of this proposed design is source controlled attenuator using gm-reduction and double active termination techniques with noise figure less than attenuation. These techniques increase the dynamic range of attenuation and reduce noise figure also. The double active termination technique also contributes in reducing noise figure below each attenuation level. It is necessary to keep noise figure below attenuation because the attenuator will be used in RF front-end of radar receiver. By keeping noise figure below attenuation, sensitivity of radar receiver will improve. Input 1 dB compression point of the proposed attenuator at maximum attenuation are at -4.3 dBm in L-Band, -5.9 dBm in S-Band and -5.3 dBm in C-Band and OIP3 at minimum attenuation are at -4.4 dBm in L-Band, -4.6 dBm in S-Band and -5 dBm in C-Band. The ideal and post-layout simulation results are presented in this paper. Figure of merit of the proposed attenuator is 280 in LBand, 70.3 in S-Band and 78.54 in C-Band. The attenuator can be used in single target tracking radar as well as in T/R module of AESA radar. [ABSTRACT FROM AUTHOR]