An MMIC Variable-Gain Amplifier Using a Cascode-Connected FET with Constant Phase Deviation

Hitoshi HAYASHI
Masahiro MURAGUCHI

Publication
IEICE TRANSACTIONS on Electronics   Vol.E81-C       pp.70-77
Publication Date: 1998/01/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Category: Microwave and Millimeter Wave Technology
Keyword: 
variable,  gain,  amplifier,  cascode,  FET,  phase,  deviation,  

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Summary: 
An MMIC variable-gain amplifier, which improves the transmission phase deviation caused by gain control, is presented. At first, it is shown that by controlling both the common-gate FET's gate bias voltage and the common-source FET's gate bias voltage, the transmission phase deviation caused by gain control of the variable-gain amplifier using a cascode-connected FET is greatly improved. In this case it is not desirable to control both of the gate bias voltages independently, because of the complexity. Thus we propose two simple gate bias voltage control circuits controlling both of the gate bias voltages, in which only one of the two gate bias voltages is controlled independently and the other is controlled dependently. Then we apply these circuits to the 1. 9-GHz-band variable-gain amplifier using the cascode-connected FET. One of the control circuits is the gate bias voltage control circuit using two resistors. It is confirmed that, by applying the newly proposed circuit, phase deviation is suppressed, from between 0and 30to between 3and 5, with 25-dB gain control. The other circuit is the gate bias voltage control circuit using the FET's nonlinear characteristics. It is confirmed that, by applying the newly proposed circuit, phase deviation is suppressed, from between 0and 44to between 6and 3 with 30-dB gain control. This is a promising technique for reducing the transmission phase deviation caused by gain control of the amplifiers used in active phased array antennas.