Low-Noise Amplifier Design Considerations For Use in Antenna Arrays

This work analyzes the implications of noise coupling in arrays of antennas on the design of low-noise amplifiers (LNAs). To select LNA design parameters in a manner familiar to LNA designers, the effective noise temperatures T^eff of LNAs are presented. The effect of beamformer coefficients and antenna coupling on T^eff is analyzed in a manner similar to a stand-alone LNA analysis. This leads to the proposed LNA design strategy of selecting LNA Γ_opt near the reflection coefficient of antenna ports and selecting the largest practical |S₁₁| with a proper phase. This strategy is based on the assumption that the antenna array may be used for various beamforming and nonbeamforming applications, unknown at the time of the design. Numerical simulations of a 38- and 41-element antenna arrays show that a global search of LNA S₁₁ and Γ_opt, which result in the minimum average beam-equivalent receiver noise temperature T_rec, finds nearly identical results to the proposed LNA design strategy. For a 41-element array with high antenna coupling at low frequencies, the proposed method shows as much as 80% improvement in the T_rec over conventional LNA design strategies that do not account for the intended use of the amplifier in an array.