Doppler aided detection, processing and demodulation of multiple signals
Multiple co-channel signals are received at the same time. The co-channel signals are separated and demodulated within a frequency range by using the Doppler shift, or offset, of the co-channel signals. The signals are isolated by determining the peaks of the signals within the subchannel, or bin. A threshold is applied to the peaks to separate signals from noise and clutter. The individual peaks are compared to a baseband frequency to determine the Doppler shift. Those signals above the threshold are processed and demodulated.
1 . A method for processing signals, the method comprising:
heterodyning at least one signal of a plurality of signals to a baseband frequency;
detecting at least one peak within the plurality of signals;
determining a Doppler shift for the at least one signal;
isolating the at least one signal by determining whether the at least one peak is above a threshold for a frequency bin; and
demodulating the at least one signal with the Doppler shift.
2 . The method of claim 1 , further comprising transform the at least one signal into the frequency bin.
3 . The method of claim 1 , further comprising reconstructing data from the at least one signal.
4 . The method of claim 1 , further comprising determining the threshold for the frequency bin using a statistical process.
5 . A method for demodulating signals, the method comprising:
detecting a plurality of signals within a frequency bin, wherein the plurality of signals are received at a same instance;
determining if a signal power of the plurality of signals equals or exceeds a threshold for the frequency bin;
determining a Doppler shift for the signal in relation to a baseband frequency;
separating the plurality of signals; and
demodulating the signal.
6 . The method of claim 5 , further comprising detecting a peak within the signal, wherein the peak equals or exceeds the threshold.
7 . The method of claim 5 , further comprising determining the threshold using a statistical process.
8 . The method of claim 7 , wherein the statistical process comprises a least squares method.
9 . The method of claim 5 , further comprising converting the plurality of signals from a plurality of analog signals.
10 . The method of claim 9 , further comprising receiving the plurality of analog signals at an antenna.
11 . A signal processing system comprising:
an antenna to receive a plurality of signals;
a peak detector to detect a peak within the plurality of signals;
a separation detector to determine an offset from a baseband frequency for the peak;
a statistical detector to calculate a threshold for the plurality of signals; and
a filter to separate the peak from noise within the plurality of signals and to identify a signal from the plurality of signals according to the peak.
12 . The signal processing system of claim 11 , wherein the filter comprises a low pass filter.
13 . The signal processing system of claim 11 , where the plurality of signals is within a frequency bin having a bandwidth.
14 . The signal processing system of claim 13 , wherein the threshold corresponds to the frequency bin.
15 . The signal processing system of claim 11 , further comprising a decoder to decode the signal.
16 . A signal processing device comprising:
a peak detector to identify a peak within a plurality of signals;
a separation detector to determine an offset for the peak from a baseband frequency; and
a low pass filter to isolate the peak from noise within the plurality of signals and to identify a signal from the plurality of signals.
17 . The signal processing device of claim 16 , further comprising a statistical detector to determine a threshold for the low pass filter.
18 . The signal processing device of claim 17 , where the threshold corresponds to a statistical process using the plurality of signals.
19 . The signal processing device of claim 16 , wherein the plurality of signals are within a frequency bandwidth, said frequency bandwidth corresponding to a frequency bin.
20 . A signal processing system comprising:
heterodyning means for heterodyning at least one signal of a plurality of signals to a baseband frequency;
detecting means for detecting at least one peak within the at least one signal within the plurality of signals;
determining means for determining a Doppler shift for the at least one signal;
isolating means for isolating the at least one signal by determining whether the at least one peak is above a threshold for a frequency bin; and
demodulating means for demodulating the at least one signal with the Doppler shift.
21 . A signal processing system comprising:
detecting means for detecting a plurality of signals within a frequency bin, wherein the plurality of signals are received at a same instance;
first determining means for determining if a signal power of the plurality of signals equals or exceeds a threshold for the frequency bin;
second determining means for determining a Doppler shift for the signal in relation to a baseband frequency;
separating means for separating the plurality of signals; and
demodulating means for demodulating the signal.