Detector system for identifying the frequency of a received signal useful in a channelized receiver

• US 6,313,620 B1
• Filed: 09/14/1995
• Issued: 11/06/2001
• Est. Priority Date: 09/14/1995
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Northrop Grumman Corporation
• Inventors: Richardson, David Livingstone, Gorham, Kenneth Duane
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US08/528,130
• Time in Patent Office: 2,245 Days
• Field of Search: 324/76.31, 324/76.39, 324/76.19, 324/76.22, 324/76.29, 455/178.1, 455/226.1
• US Class Current: 324/76.31
• CPC Class Codes: G01R 23/04 adapted for measuring in circuits having distributed constants

Abstract

A method, and apparatus for accomplishing the method, for determining the frequency of an RF signal that operates by sequentially applying a received RF signal to sequentially selected individual filters having predetermined frequency pass bands and comparing the magnitudes of the filtered and unfiltered RF signals. The frequency of the RF signal is determined as being within the predetermined frequency pass band of a filter that outputs a largest magnitude output signal relative to the magnitude of the RF signal. Signals of insufficient magnitude are not processed by the system.

Claims

1. A method for determining a frequency of an RF signal, comprising the steps of:

sequentially applying the RF signal to selected individual ones of a plurality of filters, each of the plurality of filters having a predetermined pass band;

determining magnitudes of signals that are output from individual ones of the plurality of filters;

comparing each individual one of the determined magnitudes to a magnitude of the RF signal by applying each respective individual filter output signal and the RF signal to a comparing device; and

determining a frequency of the RF signal as being within the predetermined frequency pass band of a filter that outputs a largest magnitude output signal relative to the magnitude of the RF signal, and where the filter output signal magnitude exceeds a first predetermined reference magnitude level.

2. An apparatus for determining a frequency of an RF signal comprising:

switchable filter means for sequentially applying an input RF signal to selected individual ones of a plurality of filtering means, each of said plurality of filtering means having a predetermined frequency pass band;

detecting means, coupled to an output of said switchable filter means, for determining a magnitude of an output signal emanating from each of said individual filtering means; and

processing means, coupled to an output of said detecting means, for comparing each individual one of the means, for comparing each individual one of the determined magnitudes to a magnitude of the input RF signal to determine a frequency of the input RF signal as being within the predetermined frequency pass band of the individual filtering means that outputs a largest magnitude relative to the magnitude of the input RF signal, and where the individual one determined magnitude also exceeds a first predetermined reference magnitude level.

3. An apparatus for determining a frequency of an RF signal as set forth in claim 2 wherein the switchable filter means includes:

input means, said input means having an input coupled to said input RF signal, said input means also having a plurality of outputs, said input means being responsive to an applied command for selecting one of said plurality of outputs for outputting the input RF signal;

output means, having a plurality of inputs and an output, said output means being responsive to an applied command for selecting one of said plurality of inputs of said output means to forward a signal applied to the selected one of the inputs to said output of said output means; and

a bank of filtering means, each individual one of said filtering means having a predetermined frequency pass band and being coupled between a respective individual one of said outputs of the input means and a respective individual one of said inputs of said output means.

4. A method for determining a frequency of an RF signal, comprising the steps of:

sequentially applying the RF signal to selected individual ones of a plurality of filters, each of the plurality of filters having a predetermined pass band;

determining a magnitude of an output signal emanating from individual ones of the plurality of filters;

comparing individual ones of the determined magnitudes to a magnitude of the RF signal; and

determining a frequency of the RF signal as being within the predetermined frequency pass band of a filter that outputs a largest magnitude output signal relative to the magnitude of the RF signal, and where the filter output signal magnitude exceeds a first predetermined reference magnitude level;

wherein the steps of comparing individual ones of the determined magnitudes to a magnitude of the RF signal and determining a frequency of the RF signal include the steps of;

subtracting the magnitude of an output signal emanating from individual ones of the plurality of filters from a magnitude of the RF signal to produce a difference output signal;

comparing the difference output signal magnitude to a second predetermined reference magnitude level;

reporting a signal to a loqic block when a relationship exists between the difference output signal magnitude and the second predetermined reference magnitude level which is substantially equivalent to a predefined relationship, and where the magnitude of the output signal emanating from individual ones of the plurality of filters and the magnitude of the RF signal are substantially equal, wherein the predefined relationship is defined by a characteristic of a first comparator; and

correlating the reported signal to the predetermined frequency pass band of the one individual filter that outputs a largest magnitude signal to determine a frequency of the RF signal.

5. A method as set forth in claim 4 wherein the second predetermined reference magnitude level is adjustably set to a magnitude that is offset relative to the magnitude of the difference output signal such that a signal is reported to the logic block when the magnitude of the output signal emanating from individual ones of the plurality of filters is substantially equal to the magnitude of the RF signal.

6. An apparatus for determining a frequency of an RF signal comprising:

switchable filter means for sequentially applying the RF signal to selected individual ones of a plurality of filtering means, each of said plurality of filtering means having a predetermined frequency pass band;

detecting means, coupled to an output of said switchable filter means, for determining a magnitude of an output signal emanating from said individual filtering means; and

processing means, coupled to an output of said detecting means, for comparing individual ones of the determined magnitudes to a magnitude of the RF signal to determine a frequency of the RF signal as being within the predetermined frequency pass band of the individual filtering means that outputs a largest magnitude relative to the magnitude of the RF signal, and where the individual one determined magnitude also exceeds a first predetermined reference magnitude level;

wherein the processing means includes;

subtracting means, coupled to the output of said detecting means, for subtracting the magnitude of an output signal emanating from said individual filtering means from the magnitude of the RF signal to produce a resulting difference signal;

first comparing means, having a first input coupled to an output of said subtracting means and a second input coupled to a second predetermined reference magnitude level, for comparing the resulting difference signal magnitude to the second predetermined reference magnitude level and generating an output signal when a relationship exists between the resulting subtraction signal magnitude and the second predetermined reference magnitude level which is substantially equivalent to a predefined relationship, and where the magnitude of the output signal emanating from individual ones of the plurality of filtering means and the magnitude of the RF signal are substantially equal, wherein the predefined relationship is defined by a characteristic of said first comparing means;

second comparing means, having a first input coupled to the output of said detecting means and a second input coupled to the first predetermined reference magnitude level, for comparing said detecting means output signal magnitude to the first predetermined reference magnitude level and generating an output signal when the detecting means output signal magnitude exceeds the first predetermined reference magnitude level;

logic means, coupled to the outputs of the first and second comparing means, for reporting a signal to a microprocessor means when output signals are received by the logic means from both the first and second comparing means; and

said microprocessor means being coupled to the output of said logic means and to at least one control input of said switchable filter means, for correlating the reported signal received from said logic means to the predetermined frequency pass band of the one individual filtering means that outputs the largest magnitude signal to determine the frequency of the RF signal.

7. An apparatus for determining a frequency of an RF signal as set forth in claim 6 wherein the second predetermined reference magnitude level is adjustably set to a magnitude that is offset relative to the magnitude of the subtraction output signal such that a signal is reported by said second comparing means to the microprocessor means when a magnitude of an output signal emanating from individual ones of the plurality of filtering means is substantially equal to the magnitude of the RF signal.

8. A method for determining a frequency of an RF signal, comprising the steps of:

sequentially applying an input RF signal to selected individual ones of a plurality of filters, each of the plurality of filters having a predetermined pass band;

determining a magnitude of each individual signal that is output from each individual one of the plurality of filters;

comparing a magnitude of the input RF signal to each individual one of the determined magnitudes of the individual filter output signals by applying the input RF signal and each respective one of the individual filter output signals to a comparing device; and

determining a frequency of the input RF signal as being within the predetermined frequency pass band of one of the plurality of filters that outputs a largest magnitude signal relative to the magnitude of the input RF signal.

9. An apparatus for determining a frequency of an RF signal comprising:

switchable filter means for sequentially applying an input RF signal to selected individual ones of a plurality of filtering means, each of said plurality of filtering means having a predetermined frequency pass band;

means for determining a magnitude of the input RF signal and respective magnitudes of signals that are output by individual ones of said plurality of filtering means; and

processing means, said processing means having an input coupled to an output of said determining means, said processing means for comparing the determined magnitude of the input RF signal to each individual one of the determined magnitudes of the signals output by said individual filtering means and determining a frequency of the input RF signal as being within the predetermined frequency pass band of one of the individual filtering means that outputs a largest magnitude signal relative to the magnitude of the input RF signal.