A 4-240-GHz InP Variable-Gain Amplifier Using an Analog-Controlled Input Attenuation Network

This paper presents a broadband variable-gain amplifier (VGA) using a new analog-controlled input attenuation network for distributed amplifier (DA). The input attenuation network implements diode-connected HBTs along the DA’s input line to adjust attenuation rate, thus, signal amplitudes at inputs/outputs of gain stages. By adjusting the diodes’ bias conditions, the individual stages’ contributions to the DA’s total gain are controlled for gain variation across a wide bandwidth. The 4-240-GHz VGA provides an average gain of 11 dB from 4 to 230 GHz and 7.8 dB at 240 GHz with gain control range from 8.9 to 4.7 dB. The input and output return losses are below -10 dB up to 200 GHz. The VGA generates an average power of 16 dBm and 1-dB compression point of 12 dBm. The output power is > 14 dBm up to 200 GHz and > 10 dBm up to 230 GHz.