Design of a Low Noise Figure Lnausing a Novel Coupled Inductor
Murali Banoth and Nistala Bheema RaoProblem: A low noise amplifier (LNA) design requires minimum noise introduced by the amplifier. This can be achieved by reducing the losses at the LNA's input and matching the LNA's input noise impedance with the source impedance. On-chip inductors generally have higher losses due to lower-quality factors, and this affects the noise performance of the on-chip LNAs. Approach: The paper presents a novel pyramid and coupled pyramid inductor to improve the quality factor. The improvement in quality factor is achieved by reducing the parasitic capacitance and losses utilizing a multilayer structure and also by varying the length of the inductor in each layer. The coupled pyramid inductor is designed using Sonnet software. Findings:The pyramid and coupled inductors achieve a quality factor of 16.8 and 17.15. The inductance values for these inductors are 1.92 nH and 4.85 nH, respectively. The effect of the quality factor and the inductance are validated by designing a low noise amplifier at 5.5 GHz. The LNA's simulated noise figure and gain are 1.09 dB and 15.6 dB. Conclusion:The losses in the coupled inductor are decreased by reducing the width of the conductor at each layer to compensate for the eddy currents and also the substrate losses. This results in the improvement of the inductance and quality factor in the coupled pyramid inductor. The reduced losses result in improved LNA performance, which can be observed from the Figure of Merit (FoM) of 14.6 for the LNA.