Variable gain amplifier architecture with constant matching and insertion phase

In this contribution, a Variable Gain Amplifier architecture with a reduced phase deviation is presented. The proposed architecture ideally allows constant insertion phase and input/output return losses over any gain settings. Moreover, it allows gain control both in analog and digital operating modes, depending on the application. To demonstrate its effectiveness, a full X-Band MMIC VGA has been designed in the 0.13 μm pHEMT OMMIC process. The presented MMIC VGA achieves an average 13.7 dB insertion gain with 18 dB attenuation range and 1 dB amplitude resolution; input and output return losses are better than 12.8 dB and 14.1 dB, respectively. In the 9.0-10.2 GHz range, an average 15.3 dB insertion gain is achieved, with input and output return losses better than 17.4 dB and 18.1 dB respectively, while RMS amplitude and phase errors are below 0.27 dB and 1.7° respectively.