Low Phase Noise Amplifier and Oscillator Using Feed-Forward Technique at 10 GHz

Abstract

We discuss the performance of a feed-forward amplifier (FFA) at 10 GHz. The feed-forward method is primarily used to suppress intermodulation distortion in amplifiers to suppress up-converted near-DC noise. The main amplifier in this configuration is a low-noise array of eight amplifiers in parallel and having a phase noise of -165 dBc/Hz at f = 10 kHz. By implementing a feed-forward scheme, we are able to suppress this noise, as well as close-to-carrier noise, by at least another 10 dB. This improved performance surpasses that of other present low-noise microwave amplifiers. We discuss this exceptional performance in the context of trade-offs with other amplifier properties and specifications. We also construct a 10 GHz oscillator using an air-dielectric resonator and the FFA as the loop amplifier. The phase modulated (PM) noise of this particular oscillator is either less than or comparable to the PM noise of several classes of commercial oscillators. Additionally, the AM noise performance is superior to existing oscillators