Balun Bandpass Low-Noise Amplifier in GaAs

In this work, the design of an on-chip balun bandpass low-noise amplifier (LNA) is proposed so as to achieve the functional integration of balun, bandpass filter, and LNA in a compact circuit structure. Specifically, the input matching network of the LNA is designed as a bandpass filter while its output matching network is realized with a balun. The resulted multi-functional circuit effectively reduces the circuit size and cost of RF front-end circuitry. The proposed balun bandpass LNA is implemented using a commercial GaAs pHEMT process. The measured in-band small signal gain is within 11.2±0.35 dB from 5.4 to 6 GHz, and the in-band input and output return losses are all better than 10.8 dB. The measured in-band noise figure is better than 6.2 dB with a minimum noise figure of 4.9 dB at 6 GHz. The measured in-band amplitude imbalance between the balanced output ports is with 1.2 dB while the inband phase imbalance is within 6.4 degree. Notably, the proposed balun bandpass LNA achieves 30-dBc stopband rejection from DC to 4.3 GHz and from 8.3 to 20 GHz.