Receiver in a frequency hopping communication system
First Claim
1. A receiver in a frequency hopping communication system comprising:
- filter means having a broad band-pass filter with a band characteristic including a spread spectrum bandwidth, a narrow band-pass filter having selectable band characteristics including bandwidths into which said spread spectrum bandwidth is divided, a band characteristic of said narrow band-pass filter being selected in response to a selection signal applied thereto, and means for making switch-over from said broad band-pass filter to said narrow band-pass filter in response to a synchronization detected signal applied thereto;
a code generator for generating code patterns to determine a time-sequential pattern of predetermined hopping frequencies;
a clock source for generating clock pulses for driving said code generator;
a frequency synthesizer for producing a signal of a frequency determined by an output signal from said code generator;
synchronization acquisition means for synchronizing the output signal from said frequency synthesizer and the output signal from said filter means to produce said synchronization detected signal when synchronization is set up;
selection signal generating means for generating said selection signal in response to the output signal from said code generator;
correlating means for correlating the output signals from said filter means and said frequency synthesizer to remove the modulation of said frequency hopping; and
demodulating means for extracting an information signal from the output of said correlating means.
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Accused Products
Abstract
A frequency hopping spread spectrum demodulator includes a broad band filter covering the spread spectrum bandwidth and a narrow band filter which can be selected to pass any one of a number of subbands making up the spread spectrum bandwidth. The filter is switched from broad to narrow band in response to determination of synchronization acquisition. Synchronization acquisition itself is accomplished in one embodiment by summing the outputs from a plurality of channels each selectively receiving one of a number of predetermined hopping frequencies, and threshold-comparing the summed signal to test for synchronization. In an alternate configuration, the received signal and a local reference signal are correlated, the correlated signal is integrated, and the integrated signal is then compared to a threshold, with synchronization being determined when an output from either one of the threshold comparator or integrator is present.
79 Citations
13 Claims
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1. A receiver in a frequency hopping communication system comprising:
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filter means having a broad band-pass filter with a band characteristic including a spread spectrum bandwidth, a narrow band-pass filter having selectable band characteristics including bandwidths into which said spread spectrum bandwidth is divided, a band characteristic of said narrow band-pass filter being selected in response to a selection signal applied thereto, and means for making switch-over from said broad band-pass filter to said narrow band-pass filter in response to a synchronization detected signal applied thereto; a code generator for generating code patterns to determine a time-sequential pattern of predetermined hopping frequencies; a clock source for generating clock pulses for driving said code generator; a frequency synthesizer for producing a signal of a frequency determined by an output signal from said code generator; synchronization acquisition means for synchronizing the output signal from said frequency synthesizer and the output signal from said filter means to produce said synchronization detected signal when synchronization is set up; selection signal generating means for generating said selection signal in response to the output signal from said code generator; correlating means for correlating the output signals from said filter means and said frequency synthesizer to remove the modulation of said frequency hopping; and demodulating means for extracting an information signal from the output of said correlating means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification