Spectrum surveillance receiver system

• US 4,501,020 A
• Filed: 09/21/1982
• Issued: 02/19/1985
• Est. Priority Date: 09/15/1982
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Wakeman, Philip E. D.
• Primary Examiner(s): NG, JIN FAY
• Application Number:
  US06/420,894
• Time in Patent Office: 882 Days
• Field of Search: 455/67, 455/115, 455/165, 455/226, 375/10, 324/77 B, 324/77 C, 324/77 CS, 364/485
• US Class Current: 455/226.1
• CPC Class Codes: H03J 7/32 with simultaneous display of received frequencies, e.g. panoramic receivers
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04K 3/822 by detecting the presence of a surveillance, interception or detection
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation

Abstract

A method and an apparatus for surveilling RF signals, the apparatus comprising a receiver for receiving RF signals at a selectively variable reception frequency and converting any signal received at that frequency to a predetermined IF signal, a sampling circuit for sampling the IF signal and providing output signals representative of a plurality of predetermined properties of the received signal; a circuit for comparing the representative output signals against a plurality of sets of reference signals each of which is representative of a particular modulation type and providing a first output indicative of the type of modulation of the received signal when the representative signals substantially match the set of reference values of one of the modulation types and a second output indicative of an unidentified received signal when the representative signals do not match any of the sets of reference signals.

Claims

1. A spectrum surveillance apparatus for surveilling signals within a predetermined RF band and identifying the type of modulation of signals within said band, said apparatus comprising:

a receiver adapted to receive RF signals at an adjustable reception frequency within said RF band and convert said RF signals to IF signals having a predetermined IF;

RF filter means for filtering signals input to said receiver, said filter means including a plurality of filters having bandwidths together spanning said RF band;

first switch means for selectively passing said signals through the one of said filters having the bandwidth containing said reception frequency;

IF filter means for filtering the output of said receiver, said filter means having at least one filter having a relatively broad passband and at least one filter having a relatively narrow passband, said broadband filter being normally connected to the output of said receiver and second switch means for switching the output of said receiver from said broadband filter to said narrowband filter;

means for sampling the envelope of said IF signal;

means responsive to said sampling means for providing signals representative of at least the mean, the variance, and the percentage of the samples of said signal which have at least one predetermined amplitude;

a first comparator for comparing each said representative signal with a threshold value and providing a logical set of outputs corresponding to said representative signals;

a second comparator for comparing said set of logical outputs with a plurality of sets of logical reference values, each distinctive of a particular modulation type, and providing a first output indicative of the type of modulation of said signal when said logical set of outputs substantially matches one of said sets of logical reference values or a second output when said set of logical outputs does not match any of said sets of reference values;

means responsive to said second comparator second output for causing said second switch means to switch the output of said receiver from said broadband filter to said narrowband filter; and

means for automatically indexing the frequency of reception of said receiver through at least a predetermined, variable band within said RF band at predetermined, variable frequency increments.

2. A method of surveilling signals within a predetermined RF band and identifying the type of modulation of signals within said band, said method comprising:

receiving RF signals within a relatively narrow band immediately adjacent a reception frequency and converting RF signals within said narrowband to IF signals having a predetermined IF;

passing the IF signal through a broadband IF filter;

sampling the envelope of the output of the broadband filter;

determining at least the mean, the variance and the percentage of samples having at least one predetermined amplitude;

comparing the mean, the variance and the said percentage with a set of corresponding threshold values and providing a set of logical results;

comparing the set of logical results with a plurality of sets of logical reference values and providing an indication of the type of modulation of the IF signal when the logical results substantially match one of the sets of logical reference values;

passing the IF signal through a narrowband filter and repeating the sampling, determining and comparing steps when the logical results do not match any of the logical reference values;

repeating the aforementioned steps within a predetermined band within the RF band at predetermined, variable frequency increments while maintaining a narrow bandwidth of reception immediately adjacent the reception frequency.

3. A spectrum surveillance apparatus for surveilling signals within a predetermined RF band and identifying the type of modulation and actual frequency of signals within said band, said apparatus comprising:

a receiver adapted to receive RF signals at a variable reception frequency within said RF band and convert any signal at said frequency to an IF signal having a predetermined IF;

means for sampling said IF signal and providing AM, FM and DSB lock indication outputs, modulation indication outputs and offset frequency outputs;

means responsive to said sampling means for providing output signals representative of the percentage of said samples which were locked and modulated by said sampling means;

comparator means for comparing said output signals against predetermined sets of reference values, each set being distinctive of a particular modulation type, and providing a first output indicative of the type of modulation of said signal when said representative signals substantially match the reference values of said modulation types and a second signal indicative of an unidentified signal when said representative signals do not match any of said reference values; and

means responsive to said comparator means for selecting the appropriate one of said sampling means offset frequency outputs and providing an identified signal actual frequency output.

4. An apparatus as defined in claim 3, said comparator means including:

a first comparator for comparing said representative signals with respective threshold reference values and providing a set of logical outputs; and

a second comparator for comparing said set of logical outputs against a plurality of sets of logical reference values and providing said comparator means first and second outputs.

5. A spectrum surveillance apparatus for surveilling signals within a predetermined RF band and identifying the type of modulation and actual frequency of signals within said band, said apparatus comprising:

a receiver adapted to receive RF signals at a reception frequency within said RF band and convert any signal at said reception frequency to an IF signal having a predetermined IF;

RF filter means for filtering the input to said receiver, said filter means including a plurality of filters having bandwidths together substantially spanning said RF band;

first switch means for selectively passing said signals through the one of said filters having the bandwidth containing said reception frequency;

IF filter means for filtering the output of said receiver, said filter means including at least one broadband filter and at least one narrowband filter, said broadband filter being normally connected to the output of said receiver;

second switch means for switching the output of said receiver from said broadband filter to said narrowband filter;

an AM phase-locked loop connected to the output of said IF filter means and providing an AM lock indication output, an AM modulation indication output and an AM offset frequency output;

an FM phase-locked loop connected to the output of said IF filter means and providing an FM lock indication output, an FM modulation indication output and an FM offset frequency output;

a DSB phase-locked loop connected to the output of said IF filter means and providing a DSB lock indication output, a DSB modulation indication output and a DSB offset frequency output;

means for sampling the lock and modulation indication outputs of each said loop at a predetermined sampling frequency and providing output signals representative of the percentage of samples which were locked and modulated;

first comparator means for comparing said representative signals with respective threshold reference values and providing a set of logical outputs;

second comparator means for comparing said set of logical outputs against a plurality of sets of logical reference values, each distinctive of a particular type of modulation, and providing a first output indicative of the type of modulation of said signal when said set of logical outputs substantially match one of said sets of logical reference values and a second signal indicative of an unidentified signal when said set of logical outputs does not match any of said sets of logical reference values;

means responsive to said second comparator means second output for causing said second switch means to switch the output of said receiver from said broadband filter to said narrowband filter;

means responsive to said second comparator first output for selecting the appropriate one of said circuit offset frequency outputs and providing an output representative of the actual frequency of said signal; and

means for automatically indexing the frequency of reception of said receiver through at least a predetermined variable band within said RF band at predetermined variable frequency increments.

6. A method of surveilling signals within a predetermined RF band and identifying the type of modulation of signals within said band, said method comprising:

receiving RF signals at a reception frequency within said RF band and converting any signal at said frequency to an IF signal having a predetermined IF;

passing said IF signal through AM, FM and DSB phase locked loops having lock and modulation outputs;

sampling the lock and modulation outputs of said phase locked loops;

determining the percentage of samples which indicate lock and the percentage of samples which indicate modulation;

comparing the percentages obtained in the determining step against predetermined sets of reference values, each being distinctive of a particular modulation type; and

identifying the type of modulation of the IF signal as being that whose reference values substantially matches one of the predetermined sets of reference values.

7. A spectrum surveillance apparatus for surveilling signals within a predetermined RF band and identifying at least the type of modulation of signals within said band, said apparatus comprising:

a receiver adapted to receive RF signals at a variable reception frequency within said RF band and convert any signal at that frequency to an IF signal having a predetermined IF;

first sampling means for sampling the IF envelope of said IF signal;

second sampling means for sampling said IF signal and providing AM, FM and DSB lock indication and modulation indication outputs;

means responsive to said first and second sampling means for providing signals representative of at least the variance and the percentage of said first sample means samples having at least one predetermined amplitude and signals representative of the percentage of the samples of said second sampling means which are indicative of a condition of lock and modulation;

comparator means for comparing said signals of said responsive means against predetermined sets of reference values, each set being distinctive of a particular modulation type, and providing a first output indicative of the type of modulation of said signal when said responsive means signals substantially match the reference values of said modulation type and a second signal indicative of an unidentified signal when said responsive means signals do not match any of said sets of reference values.

8. An apparatus as defined in claim 7, further including:

means for automatically indexing the frequency of reception of said receiver through at least a predetermined, variable band within said RF band at predetermined, variable frequency increments.

9. A spectrum surveillance apparatus as defined in claim 7, further including:

said second sampling means providing further output signals representative of offset frequencies; and

means responsive to said comparator means first output and said second sampling means further output signals for providing an output signal representative of the actual frequency of said signal.

10. An apparatus as defined in claim 7, further including:

filter means for filtering the output of said receiver, said filter means having at least one filter having a relatively broad passband and at least one filter having a relatively narrow passband, and switch means for selectively passing the output of said receiver through one of said filters.

11. An apparatus as defined in claim 7, said second sampling means including:

an AM phase-locked loop circuit means for providing an AM lock indication output, an AM modulation indication output and an AM offset frequency output;

an FM phase-locked loop circuit means for providing an FM ock indication output, an FM modulation indication output and an FM frequency offset output; and

a DSB phase-locked loop circuit means for providing a DSB lock indication output, a DSB modulation indication output and a DSB frequency offset output.

12. An apparatus as defined in claim 7, said comparator means including:

a first comparator for comparing said responsive means output signals against predetermined threshold values and providing a set of logical output signals; and

a second comparator for comparing each said logical output signals of said first comparator against a plurality of sets of a logical reference values, each set being distinctive of a particular modulation type, and providing said first or second comparator means output.

13. An apparatus as defined in claim 12, said modulation types including AM, FM, DSB, SSB, CW and PSK.