Investigation of 60 GHz LNA with estimated S11 values based on mathematical model and numerical solution

This paper presents the design of a millimeter-wave low noise amplifier (LNA) realized using a 0.13 μm silicon germanium bipolar complementary metal oxide semiconductor process technology. The effect of input matching on an LNA is investigated. A small-signal equivalent circuit, which depicts the resistorinductor-capacitor relationship of the input impedance network, is explored to determine its input impedance. A MATLAB code was written to understand the frequency response of the input matching network. The responses obtained are expected to be applied to the LNA to determine the input reflection coefficient (| S₁₁ |). The equivalent circuit model (ECN) is verified numerically using 2D Advanced Design System (ADS) software. Thereafter, a step-by-step methodology that can be applied in realizing a 60 GHz LNA at the V-band is formulated. The amplifier is designed using lumped elements in a two-stage cascode topology based on a novel matching network. The matched network consists of an L-input and a T-output matching network as well as inductive emitter degeneration. The output network is designed to enhance maximum power transfer, whereas interstage matching is designed to optimize for high gain while minimizing the noise of the local area network. The transistor configuration is implemented by varying the length of the transistor to observe the minimal noise figure and the maximum gain, while keeping the voltage across the collector, emitter and the base constant. By utilizing the cascode topology and series peaking inductor, (| S₁₁ |) of the LNA peaks at 14 dB, whereas the output reflection coefficient (| S₂₂ |) achieved is 25 dB. The estimated value of S11 using the ECN was about 12 dB. The noise factor is 4.3 dB minimum at 60 GHz, whereas the forward gain (| S₂₁ |) of the LNA is well above 26 dB.