Design Of Nonlinear Frequency Selective Limiter

Noor Azamiah, Md Fauzi (2013) Design Of Nonlinear Frequency Selective Limiter. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

This thesis presents the design of a nonlinear frequency selective limiter based upon bandstop response in order to improve receiver sensitivity for radar application. A frequency selective limiter is used to limit signals at each individual frequency independently in order to improve the receiver sensitivity. If compared to the tracking bandstop filter, FSL has a better performance due to the automatic suppression when the threshold is exceeded and, therefore, no extra control circuit is required. The FSL also plays its role as a limiter for signal equalization when accepting a large required signal. Other than that, the frequency selective limiter restricts the excess of signals whilst maintaining the power of low level signal. The three main elements involved in FSL were 90 degree hybrid coupler, quarterwave transformer and first order subnetwork. Simulation using the Advanced Design System, firstly it was done using schematic simulation, a circuit-oriented computation, followed by Momentum, which is an Electromagnetic simulation. Lastly, the prototype was fabricated using FR4 substrate and being measured using a network analyzer to obtain bandstop attenuation. In order to measure performance of the frequency selective limiter circuit, three different types of pin diode have been used as a comparison of circuit performance.

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