A low-noise MMIC amplifier as a microwave-to-optics link

Abstract

A low-noise MMIC distributed amplifier was designed to operate as a microwave-to-optics link in certain radar applications. It was designed to have a small signal gain of 12 dB in the frequency band of 3.1 to 3.5 GHz. In addition to the flat gain requirement, good input and output return losses with a noise figure less than 5 dB were to be realized. The amplifier has 50 Ω input and output impedances. Test measurements on the first built prototype show that amplifier has an average small signal gain of 6.2 dB in the band under the bias conditions Vds=3.5 V, and Vgs=0.56 V. Input return loss is −5.47 dB, output return loss is −9.49 dB and the average isolation is −29.51 dB. Noise figure of the amplifier changes between 5.48 and 6.46 dB in the band. A gain ripple of ±0.50 dB is obtained.