Design of a Low-Noise 2.4/5.5 GHz Dual-Band LNA Based on Microstrip Structure

This paper presents a 2.4/5.5 GHz single-stage dual-band low-noise amplifier (DB-LNA) based on a microstrip structure. The design utilizes a purely microstrip dual-band bias circuit (DBBC), composed of series microstrip lines and radial stubs. The broadband characteristics of the radial stubs enable wide frequency coverage and good frequency selectivity. A simple series-shunt microstrip matching network is adopted to maintain a compact overall design structure. The proposed DB-LNA is fabricated using a standard printed circuit board (PCB) process. Measurement results show that the amplifier achieves gains of 15.6 dB and 12.3 dB, input return losses of 14.6 dB and 14.5 dB, and output return losses of 23.2 dB and 14.1 dB at 2.4 GHz and 5.5 GHz, respectively. The measured noise figures (NF) are 1.0 dB and 1.1 dB at the corresponding frequencies, with -3 dB bandwidths exceeding 200 MHz. Compared with existing designs, the proposed LNA demonstrates notable advantages in both noise performance and bandwidth, while occupying a compact area of only 75 × 43 mm².