Frequency measurement receiver with means to resolve an ambiguity in

Abstract

In multiple frequency estimation, the bandwidth and resolution of Fast Fourier Transform (FFT) based frequency estimators are limited by A/D converter sampling rate constraints and also by real-time computational requirements. The disclosed configuration uses a Modified Chinese Remainder Theorem of a paper entitled, 'A Noise Insensitive Solution to an Ambiguity Problem in Spectra Estimation' by McCormick et al and a subsampling approach of U.S. Pat. No. 5,099,194 entitled, 'Digital Frequency Measurement Receiver With Bandwidth Improvement Through Multiple Sampling of Real Signals' to resolve the frequency ambiguity problem. The configuration extends these ideas to the multiple frequency case. It significantly extends system bandwidth by operating I FFT units in parallel at specific sampling rates chosen to maximize system bandwidth for a fixed level of noise protection. Each FFT unit output is processed by a 'peak detecting' algorithm that detects the M remainders of the M frequencies for the sampling frequency, F.sub.i, of that particular FFT unit. Using a multiple frequency ambiguity resolution algorithm, the M frequencies are estimated from the I sets of M remainders. The configuration essentially resolves the 2.pi. or aliasing ambiguity problem for multiple frequencies in a parallel, highly efficient manner. In its current configuration, the system is designed for complex signal inputs.