# US 9,519,062 B2 · Methods, systems, and computer readable media for mitigation of in-band interference of global positioning system (GPS) signals

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- Number: US 9,519,062 B2
- Document ID: US9519062B2
- Status: Granted
- Kind: B2
- Application number: 13/781,226
- Filed: 2013-02-28
- Published: 2014-06-05
- Granted: 2016-12-13
- Earliest claimed: 2012-02-28
- Assignees: Physical Devices, LLC
- Applicants: Physical Devices LLC
- Inventors: Frederick Vosburgh; Charley Theodore Wilson, III
- Web page: https://patentgrep.com/patent/US9519062B2

## CPC

- G01S 19/215: {issues related to spoofing}
- H01Q 1/32: Adaptation for use in or on road or rail vehicles
- H01Q 1/52: Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure (absorbing means H01Q17/00)
- H01Q 11/10: Logperiodic antennas (H01Q11/08 takes precedence)
- H01Q 21/28: Combinations of substantially independent non-interacting antenna units or systems {(multiple beam H01Q25/00)}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)

## Abstract

Methods, systems, and computer readable media for mitigation of interference of GPS signals are disclosed providing selective mitigation of in-band interference implementing deterministic phase control. In one embodiment, a system for mitigating interference of GPS signals includes a pair of antennas, each receiving GPS signals that include both a desired signal component and a jammer signal component. The signal from one antenna is phase-shifted as needed to make it anti-phase with the signal from the other antenna, so that when the two signals are combined, the jammer signal components substantially cancel each other, leaving the desired signal components. Determining the phase shift required involves deterministically calculating the phase shift based on the amplitudes of the two input signals and the amplitude of the combined signal instead of the iterative techniques used in conventional systems.

## Claims

### Claim 1

A method of enhanced GPS receiving by mitigating interference in reception of global positioning system (GPS) signals, the method comprising:
receiving, from a first antenna, a first signal comprising a desired signal component S1 and a jammer signal component J1;
receiving, from a second antenna, a second signal comprising a desired signal component S2 and a jammer signal component J2;
introducing a test phase shift into one of the first and second signals;
combining, by a modifier circuit, the first and second signals after introducing the test phase shift to create a third signal; and
measuring an amplitude of the third signal at a first time after introducing the test phase shift;
deterministically calculating a phase shift based on the amplitude of the third signal at the first time and amplitudes of the first and second signals;
at a second time later than the first time:
modifying, using the modifier circuit, the second signal so that jammer signal component J2 is substantially anti-phase with respect to jammer signal component J1 by applying the calculated phase shift to the second signal; and
combining, by the modifier circuit, the modified second signal and the first signal to create the third signal so that, after the second time, the third signal contains desired signal components S1 and S2 and jammer signal component J2 substantially cancels jammer signal component J1.

### Claim 2 (depends on 1)

The method of claim 1 wherein deterministically calculating the phase shift comprises calculating a phase shift δφ according to the formula δφ=nπ±2 arccos(β/2α), α being an equalized amplitude of the first and second signals at the second time and β being the amplitude of the third signal at the first time, and n being an integer.

### Claim 3 (depends on 1)

The method of claim 1 comprising equalizing the first and second signals before combining the first and second signals.

### Claim 4 (depends on 1)

The method of claim 1 comprising measuring the amplitudes of the first and second signals at the first time and using the measured amplitudes of the first, second, and third signals in deterministically calculating the phase shift.

### Claim 5 (depends on 1)

The method of claim 1 comprising measuring the amplitude of the third signal from time to time and deterministically calculating a new phase shift using the measured amplitude of the third signal.

### Claim 6 (depends on 1)

The method of claim 1 wherein combining the modified second signal with the first signal comprises summing the modified second signal with the first signal.

### Claim 7 (depends on 1)

The method of claim 1 comprising providing the modified second signal to a third antenna that emits the modified second signal to create a nulling field in the vicinity of the first antenna such that the jammer signal component J1 is cancelled by destructive interference.

### Claim 8 (depends on 7)

The method of claim 7 wherein the third antenna is directional.

### Claim 9 (depends on 7)

The method of claim 7 comprising preventing the third antenna from creating a field in the vicinity of the second antenna.

### Claim 10 (depends on 1, 9)

The method of claim 9 wherein preventing the third antenna from creating a field in the vicinity of the second antenna comprises at least one of:
shielding the second antenna;
selecting a gain pattern of at least one of the second antenna and the third antenna; and
combining a feed signal from the third antenna with the modified second signal according to the method of claim 1.

### Claim 11 (depends on 1)

The method of claim 1 wherein at least one of the first antenna and the second antenna is omnidirectional.

### Claim 12 (depends on 1)

The method of claim 1 wherein the first and second antennas comprise a lambda-constant design wherein phase center separation in terms of wave length is the same across a range of receive frequencies.

### Claim 13 (depends on 1)

The method of claim 1 wherein, for each antenna signal, the jammer to signal ratios have a value >1 dB.

### Claim 14 (depends on 1)

The method of claim 1 wherein, for each antenna signal, the jammer to signal ratios have a value >5 dB.

### Claim 15 (depends on 1)

The method of claim 1 wherein, for each antenna signal, the jammer to signal ratios have a value >10 dB.

### Claim 16 (depends on 1)

The method of claim 1 wherein, for each antenna signal, the jammer to signal ratios have a value >20 dB.

### Claim 17 (depends on 1)

The method of claim 1 comprising processing the third signal to provide enhanced GPS output of at least one type of: signal, message, data, and display.

### Claim 18 (depends on 17)

The method of claim 17 wherein processing the third signal includes performing at least one of: mixing; down converting; filtering, signal conditioning; analog-to-digital converting; decoding; dispreading; determining at least one of location and time; and providing at least one output type of position, navigation, and timing.

### Claim 19

A system for enhanced GPS receiving by mitigating interference in reception of global positioning system (GPS) signals, the system comprising:
a first antenna for receiving a first GPS signal comprising a desired signal component S1 and a jammer signal component J1;
a second antenna for receiving a second GPS signal comprising a desired signal component S2 and a jammer signal component J2; and
a modifier circuit configured for:
introducing a test phase shift into one of the first and second signals, combining the first and second signals after introducing the test phase shift to create a third signal, measuring an amplitude of the third signal at a first time after introducing the test phase shift, and deterministically calculating a phase shift based on the amplitude of the third signal at the first time and amplitudes of the first and second signals;
at a second time later than the first time, modifying the second signal so that jammer signal component J2 is substantially anti-phase with respect to jammer signal component J1, by applying the calculated phase shift to the second signal, and using the modified second signal to modify the first signal to create the third signal so that, after the second time, the third signal contains desired signal components S1 and S2 and jammer signal component J2 substantially cancels jammer signal component J1.

### Claim 20 (depends on 19)

The system of claim 19 wherein deterministically calculating the phase shift comprises calculating a phase shift δφ according to the formula δφ=nπ±2 arccos(β/2α), α being an equalized amplitude of the first and second signals at the second time and β being the amplitude of the third signal at the first time, and n being an integer.

### Claim 21 (depends on 19)

The system of claim 19 wherein the modifier circuit includes a sensing means for determining at least one of a phase, an amplitude, and a delay of the first signal relative to the second signal.

### Claim 22 (depends on 19)

The system of claim 19 wherein the system is configured for equalizing the first and second signals before combining the first and second signals.

### Claim 23 (depends on 19)

The system of claim 19 wherein the modifier circuit is configured for measuring the amplitudes of the first and second signals at the first time and using the measured amplitudes of the first, second, and third signals in deterministically calculating the phase shift.

### Claim 24 (depends on 19)

The system of claim 19 wherein using the modified second signal to modify the first signal to create a third signal comprises combining the modified second signal with the first signal to create the third signal, and wherein the modifier circuit is configured for measuring the amplitude of the third signal from time to time and deterministically calculating a new phase shift using the measured amplitude of the third signal.

### Claim 25 (depends on 24)

The system of claim 24 wherein combining the modified second signal with the first signal comprises summing the modified second signal with the first signal.

### Claim 26 (depends on 19)

The system of claim 19 wherein the modifier circuit is configured for providing the modified second signal to a third antenna that emits the modified second signal to create a nulling field in the vicinity of the first antenna such that the jammer signal component J1 is cancelled by destructive interference.

### Claim 27 (depends on 26)

The system of claim 26 wherein the third antenna is directional.

### Claim 28 (depends on 26)

The system of claim 26 comprising preventing the third antenna from creating a nulling field in the vicinity of the second antenna.

### Claim 29 (depends on 1, 28)

The system of claim 28 wherein preventing the third antenna from creating a nulling field in the vicinity of the second antenna comprises at least one of:
shielding the second antenna;
selecting a gain pattern of at least one of the second antenna and the third antenna; and
combining a feed signal from the third antenna with the modified second signal according to the method of claim 1.

### Claim 30 (depends on 19)

The system of claim 19 wherein at least one of the first antenna and the second antenna is omnidirectional.

### Claim 31 (depends on 19)

The system of claim 19 wherein, for each antenna signal, the jammer to signal ratios have a value >1 dB.

### Claim 32 (depends on 19)

The system of claim 19 wherein, for each antenna signal, the jammer to signal ratios have a value >5 dB.

### Claim 33 (depends on 19)

The system of claim 19 wherein, for each antenna signal, the jammer to signal ratios have a value >10 dB.

### Claim 34 (depends on 19)

The system of claim 19 wherein, for each antenna signal, the jammer to signal ratios have a value >20 dB.

### Claim 35 (depends on 19)

The system of claim 19 wherein the first and second antennas comprise a lambda-constant design wherein phase center separation in terms of wave length is the same across a range of receive frequencies.

### Claim 36 (depends on 19)

The system of claim 19 comprising a GPS receiver.

### Claim 37 (depends on 19)

The system of claim 19 wherein the third signal is further processed to provide enhanced GPS output of at least one type of: signal, data, message, and display.

### Claim 38 (depends on 19)

The system of claim 19 comprising a preamplifier for pre-amplifying a signal from at least one of the first and second antennas.

### Claim 39 (depends on 19)

The system of claim 19 comprising a circuit for performing at least one of: amplitude equalizing; phase shifting; group delaying; signal detecting; signal amplifying; digital signal converting; and analog signal converting.