Abstract: A method for processing positioning signals in a ranging receiver in a stand-alone mode is provided. The method includes collecting pseudorange samples from positioning signals received at the ranging receiver from a plurality of satellites. The pseudorange samples comprise message data modulation. Each satellite has an associated Gold code. A previously determined carrier frequency offset (CFO) is selected from a plurality of directly extracted CFOs. The pseudorange samples are compensated for the selected CFO. The message data modulation is removed from the pseudorange samples. The pseudorange samples are stacked for each satellite. The Gold code associated with each satellite is correlated to generate a pseudorange time sequence for the satellite. A determination is made regarding whether an adequate correlation peak exists in each pseudorange time sequence.

Abstract: A method for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver is provided. The positioning signals comprise a plurality of samples. The method includes, for each of a previously determined number of decimated samples, accumulating a specified number of samples into the decimated sample. A determination is made regarding whether to apply rate correction to the decimated samples. A particular number of rate corrections are applied to each decimated sample to generate a set of results when rate correction is to be applied. Each set of results is stored. A determination is made regarding whether a minimum number of significant carriers exists in the sets of stored results. The CFOs are determined based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results.

Abstract: A method for processing positioning signals is provided that includes receiving positioning signals at a ranging receiver from a plurality of satellites. Carrier frequency offset (CFO) results are determined at the ranging receiver based on the positioning signals. The CFO results are provided to a geolocation processor. Satellite information for the plurality of satellites is determined at the geolocation processor based on the CFO results. The satellite information is provided to the ranging receiver. Pseudorange data for the ranging receiver is determined at the ranging receiver based on the satellite information.

Abstract: An FM receiver for the reception of digital data modulated on a Subsidiary Communication Authorization (SCA) subcarrier is provided with automatic tuning capability and a coherent demodulator for minimizing noise, distortion and interference. The FM receiver is tuned automatically to minimize the measured amplitude of noise and distortion at the high frequency end of the spectrum of the FM demodulator output, above the frequencies of the SCA signal. The SCA signal is tuned by a heterodyne circuit including a balanced modulator, a voltage-controlled oscillator (VCO), and a bandpass filter. The VCO is automatically tuned to maximize the measured amplitude of the SCA signal selected by the bandpass filter. For coherent detection of BPSK (Binary-Phase-Shift-Keying), the coherent demodulator is preferably and kind of data-aided Costas loop in which digital logic circuits perform phase shifting, phase detecting, a multiplying functions.