US5157688A
Expired / Lapsed
US
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Spread spectrum transmitter for degrading spread spectrum feature detectors
Assignee: Raytheon Co
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Filing: 1991-03-14
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Granted: 1992-10-20
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Expires: 2011-03-14
Abstract
Abstract A spread spectrum transmitter uses simultaneous pseudorandom shifts of the transmitted carrier phase and receive local oscillator phases by 90 or 45 degrees and/or pseudorandom time shifts of the transmitted and receiver chip timing by half a chip duration to limit the coherent integration of carrier and chip rate detectors at an intercept receiver attempting to detect the transmissions. Direct sequence spread spectrum signals are intercepted and identified using an intercept receiver by recovering a spectral line corresponding to their carrier frequency or to their direct pseudo-noise chip rate. The conventional use of a phase shift with a fixed carrier frequency and/or a chip time shift with a fixed chip rate simplifies the design of the intercept receiver because the receiver is optimized to a single carrier frequency and chip rate. However, in accordance with the present invention, changing the frequency of the carrier and the chip rate demands complex changes in the intercept receiver design to implement carrier line recovery and chip linear recovery. This strategy accomplishes the desired reduction in the efficiency of the intercept receiver, and hence provides for low probability of detection.
Inventors
- 👤 Robert A. Dell-Imagine
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:37
CPC Classifications
H; H04; H04K; H04K3/00; H04K3/80; H04K3/82; H04K3/827; H04B; H04B1/00; H04B1/69; H04B1/707
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
139 words
A spread spectrum transmitter comprising: a clock oscillator; a first pseudo-noise code generator coupled to the clock oscillator; a half clock cycle delay coupled to the clock oscillator; a second pseudo-noise code generator coupled to the half clock cycle delay; a first modulator coupled to the first pseudo-noise code generator; a second modulator coupled to the second pseudo-noise code generator; a local oscillator; first means for pseudorandomly selecting predetermined phase steps coupled to the local oscillator; second means for pseudorandomly selecting predetermined phase steps coupled to the local oscillator; output means for providing a pseudorandomly selected output coupled to the first and second means for pseudorandomly selecting predetermined phase steps; and controller means coupled to the first and second means for pseudorandomly selecting predetermined phase steps and to the output means for selecting the pseudorandom output from the transmitter.
Claim 2
Dependent Claim
139 words
A spread spectrum transmitter comprising: a clock oscillator; a first pseudo-noise code generator coupled to the clock oscillator; a half clock cycle delay coupled to the clock oscillator; a second pseudo-noise code generator coupled to the half clock cycle delay; a first modulator coupled to the first pseudo-noise code generator; a second modulator coupled to the second pseudo-noise code generator; a local oscillator; first means for pseudorandomly selecting predetermined phase steps coupled to the local oscillator; second means for pseudorandomly selecting predetermined phase steps coupled to the local oscillator; output means for providing a pseudorandomly selected output coupled to the first and second means for pseudorandomly selecting predetermined phase steps; and controller means coupled to the first and second means for pseudorandomly selecting predetermined phase steps and to the output means for selecting the pseudorandom output from the transmitter.
Claim 3
Dependent Claim
30 words
The transmitter of claim 1 wherein the first and second modulators respectively comprise means for providing bi-phase shift keyed (BPSK) modulation with switched chip rate phase and switched carrier phase.
Claim 4
Dependent Claim
21 words
The transmitter of claim 1 wherein the first and second modulators respectively comprise means for providing minimum shift keyed (MSK) modulation.
Claim 5
Dependent Claim
21 words
The transmitter of claim 1 wherein the first and second modulators respectively comprise means for providing quadri-phase shift keyed (QPSK) modulation.
Claim 6
Dependent Claim
22 words
The transmitter of claim 1 wherein the first and second modulators respectively comprise means for providing staggered quadri-phase shift keyed (SQPSK) modulation.
Claim 7
Independent Claim
105 words
A method of transmitting spread spectrum signals that provides for a low probability of detection by intercept receivers, said method comprising the steps of: generating a clock signal; generating a first pseudorandom code in response to the clock signal; delaying the clock signal by a one half cycle clock delay to provide a delayed clock signal; generating a second pseudorandom code in response to the delayed clock signal; modulating the first and second pseudorandom codes using a predetermined modulation to provide first and second modulated pseudorandom codes; combining the first and second modulated pseudorandom codes to provide an output waveform; and transmitting the output waveform.
Claim 8
Independent Claim
105 words
A method of transmitting spread spectrum signals that provides for a low probability of detection by intercept receivers, said method comprising the steps of: generating a clock signal; generating a first pseudorandom code in response to the clock signal; delaying the clock signal by a one half cycle clock delay to provide a delayed clock signal; generating a second pseudorandom code in response to the delayed clock signal; modulating the first and second pseudorandom codes using a predetermined modulation to provide first and second modulated pseudorandom codes; combining the first and second modulated pseudorandom codes to provide an output waveform; and transmitting the output waveform.
Claim 9
Dependent Claim
138 words
The method of claim 6 which further comprises the steps of: generating first and second local oscillator signals; pseudorandomly shifting the phase of the first local oscillator signal by a first predetermined amount to provide a first phase shifted local oscillator signal; pseudorandomly shifting the phase of the second local oscillator signal by a second predetermined amount to provide a second phase shifted local oscillator signal; combining the first phase shifted local oscillator signal with the first modulated pseudorandom code to provide a first modulated and phase shifted pseudorandom code signal; combining the second phase shifted local oscillator signal with the second modulated pseudorandom code to provide a second modulated and phase shifted pseudorandom code signal; combining the first and second modulated and phase shifted pseudorandom code signals to provide an output waveform; and transmitting the output waveform.
Claim 10
Dependent Claim
15 words
The method of claim 6 wherein the predetermined modulation comprises bi-phase shift keyed (BPSK) modulation.
Claim 11
Dependent Claim
15 words
The method of claim 6 wherein the predetermined modulation comprises minimum shift keyed (MSK) modulation.
Claim 12
Dependent Claim
15 words
The method of claim 6 wherein the predetermined modulation comprises quadri-phase shift keyed (QPSK) modulation.
Claim 13
Dependent Claim
16 words
The method of claim 6 wherein the predetermined modulation comprises staggered quadri-phase shift keyed (SQPSK) modulation.
Claim 14
Independent Claim
151 words
A method of transmitting spread spectrum signals that provides for a low probability of detection by intercept receivers, said method comprising the steps of: generating first and second local oscillator signals; pseudorandomly shifting the phase of the first local oscillator signal by a first predetermined amount to provide a first phase shifted local oscillator signal; pseudorandomly shifting the phase of the second local oscillator signal by a second predetermined amount to provide a second phase shifted local oscillator signal; combining the first phase shifted local oscillator signal with the first modulated pseudorandom code to provide a first modulated and phase shifted pseudorandom code signal; combining the second phase shifted local oscillator signal with the second modulated pseudorandom code to provide a second modulated and phase shifted pseudorandom code signal; combining the first and second modulated and phase shifted pseudorandom code signals to provide an output waveform; and transmitting the output waveform.
Claim 15
Independent Claim
151 words
A method of transmitting spread spectrum signals that provides for a low probability of detection by intercept receivers, said method comprising the steps of: generating first and second local oscillator signals; pseudorandomly shifting the phase of the first local oscillator signal by a first predetermined amount to provide a first phase shifted local oscillator signal; pseudorandomly shifting the phase of the second local oscillator signal by a second predetermined amount to provide a second phase shifted local oscillator signal; combining the first phase shifted local oscillator signal with the first modulated pseudorandom code to provide a first modulated and phase shifted pseudorandom code signal; combining the second phase shifted local oscillator signal with the second modulated pseudorandom code to provide a second modulated and phase shifted pseudorandom code signal; combining the first and second modulated and phase shifted pseudorandom code signals to provide an output waveform; and transmitting the output waveform.
Claim 16
Dependent Claim
15 words
The method of claim 12 wherein the predetermined modulation comprises bi-phase shift keyed (BPSK) modulation.
Claim 17
Dependent Claim
15 words
The method of claim 12 wherein the predetermined modulation comprises minimum shift keyed (MSK) modulation.
Claim 18
Dependent Claim
15 words
The method of claim 12 wherein the predetermined modulation comprises quadri-phase shift keyed (QPSK) modulation.
Claim 19
Dependent Claim
16 words
The method of claim 12 wherein the predetermined modulation comprises staggered quadri-phase shift keyed (SQPSK) modulation.
References Cited (Backward Citations)
US5029180A
Cited
US5029181A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-10-20 | 1996-04-20 | 1996-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-10-20 | 2000-04-20 | 2000-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-10-20 | 2004-04-20 | 2004-10-20 | $7700.00 | Window Closed / Lapsed |