Dual band communication receiver

• US 4,910,521 A
• Filed: 08/03/1931
• Issued: 03/20/1990
• Est. Priority Date: 08/03/1981
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Mellon, Donald W.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US06/289,424
• Time in Patent Office: 21,414 Days
• Field of Search: 343/6.5 R, 343/6.5 LC, 343/6.8 R, 343/6.8 LC, 178/22.17, 370/100, 370/101, 375/106, 375/114, 375/116, 342/45, 380/48
• US Class Current: 342/45
• CPC Class Codes: G01S 13/762 with special measures concerning the radiation pattern, e.g. S.L.S. aerials or aerial systems providing at least two radiation patterns, e.g. providing sum and difference patterns, H01Q25/00
• CPC Class Codes: G01S 13/79 Systems using random coded signals or random pulse repetition frequencies , e.g. "Separation and Control of Aircraft using Non synchronous Techniques" [SECANT]
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures

Abstract

Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency band received. A typical system is composed of a transponder and an interrogator. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals A and B are composite signals comprised of alternate L-band and H-band signals, each having a time period equal to T and each L- or H-band signal operating at a 50% duty cycle. Reference signals A and B are time reversed to the input signals applied to the convolver and are orthogonal to one another. Each of the convolver outputs are processed through log video detection circuits to reduce the dynamic range followed by peak detecting and stretching to reduce the pulse bandwidth. The outputs from each peak detection and stretching circuitry are coupled to a smaple-and-hold circuit which are in turn divided such that one path is to synchronization and interrogation sidelobe suppression (also referred to as sidelobe inhibit, ISLI or control signal) matched filters designed to look for the particular symbol sequences between the two convolver channels characteristic of the preamble and ISLI signals. The synchronization signal and the sidelobe suppression signal are used in order to determine if a valid preamble has been detected by the receiver and if the receiver is in a desired portion of the interrogator radiation pattern; if so, then a timing or address signal and the remaining portion of the message which contains the data is clocked into a memory.

Claims

1. A dual band communications receiver for receiving dual band overlapping multibit coded message input i.f. signals at a low (L) and high (H) carrier frequency, said messages comprised of synchronization and data information wherein one bit is of length T comprising,

a reference signal generating means for producing a reference signal having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each has a bit length equal to T;

a convolver having a convolution interval of 2T, and an input port connected to receive said dual band multibit i.f. coded message, a reference port connected to the reference signal generating means for receiving the reference signal; and

an output port producing a full correlated i.f. bit amplitude signal corresponding to said low or high frequency when said reference signal and a bit of information from said dual band coded input message exactly correlate and overlap in said convolver.

a signal processing means coupled to the convolver for receiving the output signal from the convolver for converting the dual band full correlated i.f. signal to a video signal,

synchronization detection circuitry coupled to said signal processing means for detecting the time arrival of each message, and

memory means coupled to said signal processing means and said synchronization detection circuitry for storing said messages when synchronization occurs.

2. A dual band receiver according to claim 1 wherein said synchronization detection circuitry includes means for detecting time stagger information from said message.

3. A dual band receiver acccording to claim 1 wherein said synchronization detection circuitry includes means for detecting preamble information from said message.

4. A dual band communications receiver for receiving dual band overlapping multibit coded message input i.f. signals at a low (L) and high (H) carrier frequency, said messages comprised of a preamble and data signal wherein one bit is of length T, comprising:

a reference signal generating means for producing a reference signal having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each has a bit length equal to T;

a convolver having a convolution interval of 2T, and an input port connected to receive said dual band multibit i.f. coded message, a reference port connected to the reference signal generating means for receiving the reference signal, and an output port producing a full correlated i.f. bit amplitude signal corresponding to said low or high frequency when said reference signal and a bit of information from said dual band coded input message exactly correlate and overlap in said convolver,

a signal processing means coupled to the convolver for receiving the output signal from the convolver for converting the dual band full correlated i.f. signal to a video signal,

preamble detection circuitry coupled to said signal processing means for detecting the time arrival of each preamble to provide synchronization and generation of a clock signal for each such preamble, and

data processing and storage means coupled to said signal processing means and said preamble detection circuitry having a plurality of storage locations related to the number of overlapping messages such that the data signals from said signal processing means is entered into each of said storage locations as clock signals are generated by said preamble detection circuitry and provided to said storage locations.

5. A dual band receiver system for receiving dual band overlapping coded multibit message input i.f. signals at a low (L) and high (H) carrier frequency, said input signals comprising synchronization and data information on its sum pattern and a control signal on its difference pattern and having a bit time period equal to T, comprising:

(a) at least two receiver channels A and B,

(1) channel A comprising an i.f. frequency stage for producing a dual band i.f. representation of the coded multibit signals, a reference signal generating means for generating A reference signals having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each has a bit length of T, a first convolver having a convolution interval of 2T and having an input, reference and output port, said input port connected to the i.f. frequency stage for receiving the dual band i.f. representation of the coded multibit signals, the reference port coupled to the reference signal generating means for receiving the reference signal A having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each has a bit length of T, whereby said first convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal A and a bit of information from said coded input message exactly correlate and coincide in said first convolver,

signal processing means coupled to said output port for converting said correlated dual band i.f. signal to a first video signal and producing its maximum amplitude during predetermined time intervals to form the output signal of channel A,

(2) channel B comprising an i.f. frequency stage for producing a dual band i.f. representation of the coded multibit signals, a reference signal generating means for generating B reference signals having alternate L and H band carrier signals such that each L or H band signal operates at a 50% duty cycle and each has a bit length of T, a second convolver also having a convolution interval of 2T and having an input, reference and output port, said input port connected to the i.f. frequency stage for receiving the same signal as the input port of said channel A convolver, the reference port coupled to the reference signal generating means for receiving the reference signal B, having alternate L and H band barrier signals, such that each L or H band signal operates at a 50% duty cycle and each has a bit length of T, such that whereby said second convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal B and a bit of information from said dual band coded input message exactly correlate and coincide in said second convolver,

signal processing means coupled to said output port for converting such dual band correlated i.f. signal to a second video signal and producing its maximum amplitude during predetermined time intervals to form the ouput signal of channel B,

(b) processor means coupled to the channel A and channel B signal processing means for receiving the output signals of channels A and B for detecting, storing and de-interleaving said overlapping messages and including a plurality of memory locations, and

(c) synchronization detection circuitry coupled to the channel A and channel B convolvers for receiving the output signals of channels A and B for identifying synchronization of said overlapping messages to establish time of arrival of said dual band overlapping coded multibit message input signals and produce signals selectively to said plurality of memory locations to transfer the data bits into selected memory locations.

6. A dual band receiver according to claim 5 wherein said synchronization information is preamble information and said synchronization detection circuitry is preamble detection circuitry.

7. A dual band receiver system according to claim 6 further including sidelobe suppression circuitry coupled to the channel A and channel B convolves for receiving the output signals of channels A and B, said sidelobe suppression circuitry producing an ouptut signal related to the magnitude of said control signal and which selectively inhibits the pulses from said preamble detection circuitry when the amplitude of the output from said preamble detection circuit has a predetermined relationship to the amplitude from the sidelobe suppression circuitry.

8. A dual band receiver system according to claim 7 further including means for varying the amplitude of the sidelobe suppression circuitry to thereby sharpen or broaden the response of said receiver system.

9. A dual band receiver system according to claim 5 wherein said first and second convolvers are surface acoustic wave convolvers.

10. A dual band receiver system according to claim 5 wherein said first and second signal processing means includes a log detector coupled to said convolver output, a peak detector coupled to said log detector and a sample-and-hold circuit coupled to said peak detector.

11. A dual band receiver system according to claim 10 further including a first analog-to-digital (A/D) converter coupled to the sample-and-hold circuit in said first processing means and a second analog-to-digital converter connected to the sample-and-hold circuit in said second processing means, the outputs of each of said A/D converters being input to a digital differencing circuit.

12. A dual band receiver system according to claim 11 wherein the output from said digital differencing circuit is coupled to said preamble detection circuit, said preamble detection circuit comprising an n-tap transversal filter, where n equals the number of bits in said preamble and having n-weighted taps which are matched to the preamble code.

13. A dual band receiver system according to claim 11 wherein the output from said digital differencing circuit is input to a preamble amplitude correlator having taps weighted to match the preamble code.

14. A dual band receiver system according to claim 11 wherein said digital differencing circuit is also input to a control signal amplitude correlator having taps weighted to match the control signal code.

15. A dual band receiver system according to claim 14 further including digital comparison means for comparing the amplitude outputs of said preamble and control signal correlators and generating timing signals when the correlator outputs have a predetermined relationship to one another.

16. A dual band receiver system according to claim 5 further including band pass filter means coupled to the output of each of the convolvers, said filter means comprising an L band pass filter for rejecting the H band frequencies and an H band pass filter for rejecting the L band frequencies to produce only i.f. full correlation L and H signals, respectively.

17. A dual band receiver system according to claim 16 further including switching means for multiplexing the output of said filter means to produce a composite i.f. full correlation L and H output signal.

18. A dual band IFF system comprising:

(a) a plurality of interrogators each comprising an interrogator transmitter and receiver, said interrogator transmitter transmitting a multibit coded message including synchronization and data information on the sum pattern and a control signal on the difference pattern, each bit being of length T, said message being transmitted at a low (L) or high (H) carrier frequency,

(b) at least one dual band transponder comprising a transponder transmitter and receiver, said dual band transponder receiver detecting and validating receipt of said message and control signal at said L or H carrier frequency and said transponder transmitter transmitting a unique message at a carrier frequency L or H corresponding to the carrier frequency detected by the transponder receiver in response thereto which is detected by said interrogator receiver, and

(c) said transponder receivers each comprising;

(1) a reference signal generating means for generating A and B reference signals having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each bit has a bit length of T,

(2) at least two receiver channels A and B, channel A comprising an i.f. stage for producing a dual band i.f. representation of the coded multibit signals, a convolver having a convolution interval of 2T and having an input, reference and output port, said input port connected to the i.f. frequency stage for receiving the dual band i.f. representation of the coded multibit signals, the reference port coupled to the reference signal generating means for receiving the reference signal A whereby said convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal A and a bit of information from said coded input message exactly correlate and coincide in said first convolver,

signal processing means coupled to said output port for converting such correlated dual band i.f. signal to a first video signal and producing its maximum amplitude during pre-determined time intervals to form the output signal of channel A,

Channel B comprising an i.f. stage for producing a dual band i.f. representation of the coded multibit signals, a convolver having a convolution interval of 2T and having an input, reference, and output port, said input port connected to the i.f. stage for receiving the same signal as the input port of said first convolver, the reference port coupled to the reference signal generating means for receiving the reference signal B, whereby said convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal B and a bit of information from said dual band coded input message exactly correlate and coincide in said convolver,

signal processing means coupled to said output port for converting such correlated dual band i.f. signal to a second video signal and producing its maximum amplitude during predetermined time intervals to form the output signal of channel B,

(3) processor means coupled to receive the output signals of channels A and B for detecting, storing and de-interleaving said overlapping messages and including a plurality of memory locations, and

(4) synchronization detection circuitry coupled to receive the output signals of channels A and B for detecting synchronization of said overlapping messages to establish time of arrival of said dual band overlapping coded multibit message input signals and produce signals selectively to said plurality of memory locations to transfer the data bits into selected memory locations.

19. A dual band IFF system according to claim 18 wherein said synchronization information is preamble information and said synchronization detection circuitry is preamble detection circuitry.

20. A dual band IFF system according to claim 19 further including sidelobe suppression circuitry in said transponder receiver coupled to receive the output signals of channels A and B, said sidelobe suppression circuitry producing an output signal related to the magnitude of said control signal and which selectively inhibits the pulses from said preamble detection circuitry when the amplitude of the output from said preamble detection circuit is of a predetermined magnitude with respect to the amplitude from the sidelobe suppression circuitry.

21. A dual band IFF system according to claim 19 wherein said first and second signal processing means includes a log detector coupled to the convolver output, a peak detector coupled to said log detector and a sample-and-hold circuit coupled to said peak detector.

22. A dual band IFF system according to claim 21 further including a first analog-to-digital (A/D) converter coupled to the sample-and-hold circuit in said first processing means and a second analog-to-digital converter connected to the sample-and-hold circuit in said second processing means, the outputs of each of said A/D converters being input to a digital differencing circuit.

23. A dual band IFF system according to claim 22 wherein the output from said digital differencing circuit is coupled to said preamble detection circuit, said preamble detection circuit comprising an n-tap transversal filter, where n equals the number of bits of said preamble, and having n-weighted taps which are matched to the preamble code.

24. A dual band IFF system according to claim 22 wherein the output from said digital differencing circuit is coupled to said sidelobe suppression circuit, said sidelobe suppression circuit comprising an n-tap transversal filter, where n equals the number of bits in said control signal, and having n-weighted taps which are matched to the control signal code.

25. A dual band IFF system according to claim 18 further including means for varying the amplitude of the sidelobe suppression circuitry to thereby sharpen or broaden the response of the transponder receiver system.

26. A dual band IFF system according to claim 18 wherein said first and second convolvers are surface acoustic wave convolvers.

27. A dual band IFF system according to claim 18 further including band pass filter means coupled to the output of each of the convolvers, said filter means comprising an L band pass filter for rejecting the H band frequencies and an H band pass filter for rejecting the L band frequencies to produce only i.f. full correlation L and H signals, respectively.

28. A dual band IFF system according to claim 27 further including switching means for multiplexing the output of said filter means to produce a composite i.f. full correlation L and H output signal.