Implementation of an LNA Using a Microstrip Coupler as a DC-Block for Sub-6 5G Communication Systems

This paper presents the design strategy of a microwave low noise amplifier (LNA) in microstrip technology for sub-6 GHz 5G communication systems. A microstrip coupler is exploited to design a DC block in order to avoid unwanted parasitic effects generated by lumped elements and to facilitate fabrication. Bias and matching networks are implemented using microstrip transmission lines. Based on the designed circuit, a prototype is fabricated and measured using an Agilent Technologies (hp)® ATF13786 field effect transistor. The proposed LNA is simulated and measured at 3.5 GHz. The results demonstrate that the proposed LNA achieves high gain of 12.7 dB, noise figure less than 2 dB, input and output reflection coefficients less than –10 dB, and unconditional stability over the desired bandwidth. Regarding the large signal results, the proposed LNA yields excellent performance with an output power of 16.4 dBm, and a power added efficiency (PAE) of 18%. Furthermore, the proposed LNA exhibits good linearity with an output compression point at 1 dB (OP1dB) of 0 dBm, and a third-order intercept point (OIP3) greater than +37.7 dBm.