Chirp communication system
First Claim
1. Apparatus for communicating between stations comprising means including a surface wave device for producing an information bearing chirp signal starting at any one of a plurality of initial frequencies in a range, and means for transmitting said chirp signal, means for receiving said chirp signal including a unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for compressing chirp signals starting at any of said initial frequencies in said range, and means responsive to said compressed chirp signals for recovering the information content therefrom.
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Abstract
A communication system that is difficult to jam has a transmitter transmitting successive chirp signals, which start at different initial frequencies and all have the same frequency - time slope. At the transmitter successive selections are made from among the different available chirp signal frequencies in accordance with a predetermined pseudorandom program that is known at the receiving station. The receiver has a chirp matched filter capable of receiving all of the different chirps but, being a distributed filter, it delays the different received chirps by differing amounts depending upon the initial frequency of each chirp. The output of the chirp filter is envelope-detected, and the resulting pulse signal is passed through a time gate that is gated on at a time that is selected in accordance with the predetermined program. The system has advantages for anti-jam communications, multiple-access communications, frequency diversity radio, and coding using multiple frequencies, as examples. The chirp matched filter is conveniently a surface wave device.
70 Citations
13 Claims
- 1. Apparatus for communicating between stations comprising means including a surface wave device for producing an information bearing chirp signal starting at any one of a plurality of initial frequencies in a range, and means for transmitting said chirp signal, means for receiving said chirp signal including a unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for compressing chirp signals starting at any of said initial frequencies in said range, and means responsive to said compressed chirp signals for recovering the information content therefrom.
- 3. Apparatus for communicating between stations comprising means including a surface wave device for producing a chirp signal starting at any of a plurality of initial frequencies in a range and further including means for selecting a chirp signal having one of said plurality of initial frequencies in accordance with predetermined criteria for generating a sequence of chirp signals, means for transmitting said chirp signal, means for receiving said chirp signal including a unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for compressing chirp signals starting at any of said initial frequencies in said range, and wherein said distributed filter means comprises means for producing an output signal after a time delay that varies in dependence upon said initial frequency, and wherein said means for receiving said chirp signal further comprises gating means following said filter for producing a time window for passing the output signal of said filter including means for changing the time of occurrence of said time window to pass signals from chirps having any one of said initial frequencies.
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9. Apparatus for communicating between stations comprising means including a surface wave device for producing a chirp signal starting at any one of a plurality of initial frequencies in a range, means for transmitting said chip signal, means for receiving said chirp signal including a unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for compressing chirp signals starting at any of said initial frequencies in said range, and wherein said means for receiving said chirp signal further comprises local timing means producing control signals, and means preceding said unitary distributed filter means for gating on the received chirp signal for the duration of the chirp in response to said control signals of said local timing means.
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11. Apparatus for communicating between stations comprising means including a surface wave device for producing a chirp signal starting at any one of a plurality of initial frequencies in a range, means for transmitting said chirp signal, means for receiving said chirp signal including a unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for compressing chirp signals starting at any of said initial frequencies in said range, and wherein said chirp signal represents one data state, and comprising means including a second surface wave device for transmitting a distinguishably different second chirp signal representing a second data state, and further comprising modulation means for selecting said first and second chirp signals in accordance with information to be communicated.
- 12. Apparatus for communicating between spaced apart stations comprising means including an unitary surface wave device for producing an succession of chirp signals each starting at one of a plurality of initial frequencies within a range and having a fixed slope of frequency variation with respect to time, means for selecting one of said plurality of initial frequencies for each of said chirp signals in accordance with predetermined criteria for generating a sequence, means for transmitting said chirp signals, means spaced apart from said transmitting means for receiving said chirp signals including an unitary matched surface wave device serving as an unitary distributed filter means having time invariant parameters for receiving chirp signals starting at any of said initial frequencies within said range and for producing an output signal due to each chirp signal after a time delay dependent upon said initial frequency, gating means for producing a time window for passing said output signals from said filter means and time adjustable to pass output signals due to chirps having any of said initial frequencies, and means for selectively adjusting the time of occurrence of said time window in accordance with said predetermined criteria.
Specification