A 24-30 GHz Image-Rejection Filtering LNA with > 35-dBc Image-Rejection Ratio at < 22 GHz

This paper introduces a 24–30 GHz Image-rejection filtering Low Noise Amplifier (LNA) for millimeter-wave super-heterodyne receivers, employing 0.15µm GaAs pHEMT technology and targeting n257 and n258 bands. We propose an innovative design approach to integrate multiple Elliptic High-pass Filters directly into the LNA's matching network. This is achieved through the integration of three additional capacitors into the LNA's original matching network, which effectively generate three transmission zeros in the lower frequency, resulting in a pronounced Elliptic High-pass Filter response. This novel circuit topology significantly improves the attenuation rate of the LNA's gain outside its operational frequency band, achieving more than 35 dBc of rejection at the image frequency below 22 GHz. Simulation results demonstrate that the proposed LNA achieves a Noise Figure (NF) of less than 1.9 dB, a linear gain of 21.3±1.3 dB, input and output return losses of less than -12 dB, and an Output 1dB compression point (OP1dB) exceeding 10 dBm, making it suitable for millimeter-wave satellite communication applications.