Handheld GPS jammer locator

• US 20070115175A1
• Filed: 11/22/2005
• Published: 05/24/2007
• Est. Priority Date: 11/22/2005
• Status: Active Grant

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Joy, Robert, Velicer, Gregory
• Granted Patent: US 7,233,284 B2
• Time in Patent Office: Days
• US Class Current: 342/432
• CPC Class Codes: G01S 19/015 Arrangements for jamming, spoofing or other methods of denial of service of such systems
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/18 Military applications
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 3/36 the separate antennas having differently-oriented directivity characteristics
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

A handheld GPS jammer locator for locating a GPS jamming signal generated by a jammer. The handheld GPS jammer locator has two modes of operation, a amplitude mode and a difference finding mode. The amplitude measures the strength of an incoming GPS jamming signal and the difference finding mode determines the direction of the incoming jamming signal.

Claims

1. A handheld GPS jammer locator for locating a GPS jamming signal comprising:

(a) first and second antennas separated by a half wavelength of a GPS carrier frequency, said first and second antennas receiving said GPS jamming signal and providing first and second RF electrical signals at the GPS carrier frequency of approximately 1.575 GHz;

(b) a quadrature coupler connected to said first and second antennas to receive said first and second RF electrical signals, said quadrature coupler combining said first and second RF electrical signals and than generating third and fourth RF electrical signals representing a pair of displaced antenna beams received by said first and second antenna beams;

(c) an RF switch connected to said quadrature coupler to receive said third and fourth RF electrical signals, said RF switch, responsive to an RF switching signal, sequentially passing said third and fourth RF signals through said RF switch;

(d) a logarithmic narrow band receiver connected to said RF switch to receive said third and fourth RF signals passed through said RF switch, said logarithmic narrow band receiver converting said third and fourth RF signals to Intermediate Frequency (IF) signals having a logarithmic scaling factor of approximately zero volts to three volts.

(e) a video switch connected to said logarithmic narrow band receiver to receive said IF signals;

(f) first and second sample/hold circuits connected to said video switch, said first and second sample/hold circuits;

(g) said video switch switching said IF signals generating samples of said IF signals and providing the samples of said IF signals to said first and second sample/hold circuits, wherein the samples of said IF signals are provided to said first and second sample/hold circuits and held within said first and second sample/hold circuits at a sampling frequency synchronized to a switching frequency for said RF switch;

(h) a summing amplifier connected to said first and second sample/hold circuits to receive and add the samples of said IF signals held by said first and second sample/hold circuits generating a summed signal which indicates a signal strength for said GPS jamming signal; and

(i) a difference amplifier connected to said first and second sample/hold circuits to receive and subtract the samples of said IF signals held by said first and second sample/hold circuits generating a difference signal which indicates a direction of arrival for said GPS jamming signal.

2. The handheld GPS jammer locator of claim 1 further comprising a programmed logic device connected to said RF switch to provide said RF switching signal to said RF switch.

3. The handheld GPS jammer locator of claim 2 wherein said programmed logic device generates a sample hold control signal provided to said video switch and said first and second sample/hold circuits to control sampling of said IF signals by said first and second sample/hold circuits and storage of each sample of said IF signals taken within said first and second sample/hold circuits.

4. The handheld GPS jammer locator of claim 2 further comprising a five volt power supply for providing five volts to said quadrature coupler, said RF switch, said logarithmic narrow band receiver, said programmed logic device, said summing amplifier and said difference amplifier.

5. The handheld GPS jammer locator of claim 1 further comprising a seven volt power supply for providing seven volts to said first and second sample/hold circuits.

6. The handheld GPS jammer locator of claim 1 wherein the switching frequency for said RF switch is within a range of ten hertz to one kilohertz.

7. The handheld GPS jammer locator of claim 1 wherein said RF switching signal is a two bit digital code, said first RF electrical signals from said first antenna pass through said RF switch when bit one of said two bit digital code is active and said second RF electrical signals from said second antenna pass through said RF switch when bit two of said two bit digital code is active.

8. A handheld GPS jammer locator for locating a GPS jamming signal comprising:

(a) first and second antennas separated by a half wavelength of a GPS carrier frequency, said first and second antennas receiving said GPS jamming signal and providing first and second RF electrical signals at the GPS carrier frequency of approximately 1575.42 MHz;

(b) a quadrature coupler connected to said first and second antennas to receive said first and second RF electrical signals, said quadrature coupler combining said first and second RF electrical signals and than generating third and fourth RF electrical signals representing a pair of displaced antenna beams received by said first and second antenna beams;

(c) an RF switch connected to said quadrature coupler to receive said third and fourth RF electrical signals, said RF switch, responsive to an RF switching signal, sequentially passing said third and fourth RF signals through said RF switch;

(d) a logarithmic narrow band receiver connected to said RF switch to received said third and fourth RF signals passed through said RF switch, said logarithmic narrow band receiver converting said third and fourth RF signals to Intermediate Frequency (IF) signals having a logarithmic scaling factor of approximately zero volts to three volts, said logarithmic narrow band receiver including;

(i) an RF low noise amplifier/mixer for mixing said third and fourth RF electrical signals at the GPS carrier frequency of approximately 1575.42 MHz with an external 1505.42 MHz Local Oscillator signal to generate said IF signals;

(ii) a bandpass filter connected to said RF low noise amplifier/mixer, said bandpass filter filtering said IF signal to a bandpass frequency of 70 MHz;

(iii) a log amplifier connected to said bandpass filter, said log amplifier having a log transfer function covering signals within a power level range of +10 dBm to −

70 dBm, wherein an output signal from log amplifier is provided as said zero volts to three volts signal which represents the power level range of +10 dBm to −

70 dBm for IF signals which are input to said log amplifier;

(e) a video switch connected to said logarithmic narrow band receiver to receive said IF signals;

(f) first and second sample/hold circuits connected to said video switch, said first and second sample/hold circuits;

(g) said video switch switching said IF signals generating samples of said IF signals and providing the samples of said IF signals to said first and second sample/hold circuits, wherein the samples of said IF signals are provided to said first and second sample/hold circuits and held within said first and second sample/hold circuits at a sampling frequency synchronized to a switching frequency for said RF switch;

(h) a summing amplifier connected to said first and second sample/hold circuits to receive and add the samples of said IF signals held by said first and second sample/hold circuits generating a summed signal which indicates a signal strength for said GPS jamming signal; and

(i) a difference amplifier connected to said first and second sample/hold circuits to receive and subtract the samples of said IF signals held by said first and second sample/hold circuits generating a difference signal which indicates a direction of arrival for said GPS jamming signal.

9. The handheld GPS jammer locator of claim 8 further comprising a programmed logic device connected to said RF switch to provide said RF switching signal to said RF switch.

10. The handheld GPS jammer locator of claim 9 wherein said programmed logic device generates a sample hold control signal provided to said video switch and said first and second sample/hold circuits to control sampling of said IF signals by said first and second sample/hold circuits and storage of each sample of said IF signals taken within said first and second sample/hold circuits.

11. The handheld GPS jammer locator of claim 9 further comprising a five volt power supply for providing five volts to said quadrature coupler, said RF switch, said logarithmic narrow band receiver, said programmed logic device, said summing amplifier and said difference amplifier.

12. The handheld GPS jammer locator of claim 9 further comprising a seven volt power supply for providing seven volts to said first and second sample/hold circuits.

13. The handheld GPS jammer locator of claim 9 wherein the switching frequency for said RF switch is within a range of ten hertz to one kilohertz.

14. The handheld GPS jammer locator of claim 9 wherein said RF switching signal is a two bit digital code, said first RF electrical signals from said first antenna passing through said RF switch when bit one of said two bit digital code is active and said second RF electrical signals from said second antenna passing through said RF switch when bit two of said two bit digital code is active.

15. A handheld GPS jammer locator for locating a GPS jamming signal comprising:

(a) first and second antennas separated by a half wavelength of a GPS carrier frequency, said first and second antennas receiving said GPS jamming signal and providing first and second RF electrical signals at the GPS carrier frequency of approximately 1575 MHz;

(b) a quadrature coupler connected to said first and second antennas to receive said first and second RF electrical signals, said quadrature coupler combining said first and second RF electrical signals and than generating third and fourth RF electrical signals representing a pair of displaced antenna beams received by said first and second antenna beams;

(c) an RF switch connected to said quadrature coupler to receive said third and fourth RF electrical signals, said RF switch, responsive to an RF switching signal, sequentially passing said third and fourth RF signals through said RF switch;

(d) a logarithmic narrow band receiver connected to said RF switch to received said third and fourth RF signals passed through said RF switch, said logarithmic narrow band receiver converting said third and fourth RF signals to Intermediate Frequency (IF) signals having a logarithmic scaling factor of approximately zero volts to three volts, said logarithmic narrow band receiver including;

(i) an RF low noise amplifier/mixer for mixing said third and fourth RF electrical signals at a frequency of 1575.42 MHz with a 1505.42 MHz Local Oscillator signal to generate said IF signals;

(ii) a local oscillator synthesizer connected to said RF low noise amplifier/mixer to provide said 1505.42 MHz Local Oscillator signal to said RF low noise amplifier/mixer;

(iii) a reference oscillator connected to said local oscillator synthesizer, said oscillator providing a 10 MHz reference signal to said local oscillator synthesizer which then generates 1505.42 MHz Local Oscillator signal in response to said 10 MHz reference signal;

(iv) a first bandpass filter having a signal input and a signal output connected to said RF low noise amplifier/mixer, said first bandpass filter filtering said third and fourth RF electrical signals to said frequency of 1575.42 MHz and then returning said third and fourth RF electrical signals to said RF low noise amplifier/mixer;

(v) a second bandpass filter connected to a signal output of said RF low noise amplifier/mixer, said second bandpass filter filtering said IF signal to a bandpass frequency of 70 MHz;

(vi) a log amplifier connected to said bandpass filter, said log amplifier having a log transfer function covering signals within a power level range of +10 dBm to −

70 dBm, wherein an output signal from log amplifier is provided as said zero volts to three volts signal which represents the power level range of +10 dBm to −

70 dBm for IF signals which are input to said log amplifier;

(e) a comparator connected to said log amplifier, said comparator being configured to provide a threshold voltage of 10 millivolts wherein input signals below said threshold voltage of 10 millivolts are noise signal and are clamped to ground;

(f) a video switch connected to said comparator to receive said IF signals from said comparator;

(g) first and second sample/hold circuits connected to said video switch, said first and second sample/hold circuits;

(h) said video switch switching said IF signals generating samples of said IF signals and providing the samples of said IF signals to said first and second sample/hold circuits, wherein the samples of said IF signals are provided to said first and second sample/hold circuits and held within said first and second sample/hold circuits at a sampling frequency synchronized to a switching frequency for said RF switch;

(i) a summing amplifier connected to said first and second sample/hold circuits to receive and add the samples of said IF signals held by said first and second sample/hold circuits generating a summed signal which indicates a signal strength for said GPS jamming signal;

(j) a difference amplifier connected to said first and second sample/hold circuits to receive and subtract the samples of said IF signals held by said first and second sample/hold circuits generating a difference signal which indicates a direction of arrival for said GPS jamming signal; and

(k) a programmed logic device connected to said RF switch to provide said RF switching signal to said RF switch.

16. The handheld GPS jammer locator of claim 15 wherein said programmed logic device generates a sample hold control signal provided to said video switch and said first and second sample/hold circuits to control sampling of said IF signals by said first and second sample/hold circuits and storage of each sample of said IF signals taken within said first and second sample/hold circuits.

17. The handheld GPS jammer locator of claim 15 further comprising a five volt power supply for providing five volts to said quadrature coupler, said RF switch, said logarithmic narrow band receiver, said programmed logic device, said summing amplifier and said difference amplifier.

18. The handheld GPS jammer locator of claim 15 further comprising a seven volt power supply for providing seven volts to said first and second sample/hold circuits.

19. The handheld GPS jammer locator of claim 15 wherein the switching frequency for said RF switch is within a range of ten hertz to one kilohertz.

20. The handheld GPS jammer locator of claim 15 wherein said RF switching signal is a two bit digital code, said first RF electrical signals from said first antenna passing through said RF switch when bit one of said two bit digital code is active and said second RF electrical signals from said second antenna passing through said RF switch when bit two of said two bit digital code is active.