Phase noise in heterojunction field effect transistor amplifiers

We present phase modulation (PM) noise results in linear high electron mobility transistor (HEMT) amplifiers at different bias conditions at carrier frequencies of 1 GHz and 2 GHz. Our measurements show that the noise at a carrier frequency of 1 GHz is higher than at 2 GHz as expected. It was also found that the dependence of PM noise with drain voltage and drain current varied when different transistors were used. The best PM noise obtained for a HEMT amplifier was L(10 Hz) ≈ -132 dBc/Hz at a carrier frequency of 1 GHz and L(10 Hz) ≈ -127 dBc/Hz at a carrier frequency of 2 GHz.