EP0115152A2
Expired / Lapsed
EP
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Doppler shift measurement receiver
Assignee: Litton Marine Systems Inc
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Filing: 1983-12-19
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Granted: —
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Expires: 2003-12-19
Abstract
Abstract A receiver accurately measures the Doppler shift of a radio signal from a transmitter having a known frequency and moving with respect to the receiver by using the signal from another transmitter of known frequency as a reference. The signals from the two transmitters are received by a single antenna (1), separated, and processed in separate channels. In a typical application using Global Positioning System satellite signals, each signal is discretely extracted by auto-correlation with its own pseudorandum noise signal, filtered, amplified, and applied to second mixers (17, 17') in phase locked loops in the respective channels. The two resulting second IF signals are applied to an output mixer (31) whereupon the resulting difference output signal represents the difference in frequency between the two Doppler signals.
Inventors
- 👤 Reuben Edwin Maine
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 16:27
CPC Classifications
G; G01; G01S; G01S11/00; G01S11/02; G01S11/10; G01S19/00; G01S19/01; G01S19/13; G01S19/24; G01S19/29
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
196 words
A differential Doppler receiver comprising antenna means for simultaneously receiving radio frequency signals from first and second relatively moveable remote transmitters having the same base frequency, characterised in that the receiver includes means for separating the signals from the first and second transmitters from the combined received signal, a reference channel for processing one of the separated signals, and a Doppler difference channel for processing the other separated signal, the receiver further comprising timing oscillator means (23), each of the channels including a phase locked loop in which a voltage controlled oscillator (7, 7') is regulated in accordance with the magnitude of the signal flowing in that loop, each of the phase locked loops further including means for heterodyning the separated signal flowing in that loop with a local oscillator signal derived from the voltage controlled oscillator (7, 7') in that loop, the voltage controlled oscillator being adjusted so that in the phase locked condition the signal from the heterodyning means is equal in phase and frequency to the signal from the timing means, the receiver further comprising means to provide an output signal representative of the difference in frequency between the two local oscillator signals.
Claim 2
Dependent Claim
196 words
A differential Doppler receiver comprising antenna means for simultaneously receiving radio frequency signals from first and second relatively moveable remote transmitters having the same base frequency, characterised in that the receiver includes means for separating the signals from the first and second transmitters from the combined received signal, a reference channel for processing one of the separated signals, and a Doppler difference channel for processing the other separated signal, the receiver further comprising timing oscillator means (23), each of the channels including a phase locked loop in which a voltage controlled oscillator (7, 7') is regulated in accordance with the magnitude of the signal flowing in that loop, each of the phase locked loops further including means for heterodyning the separated signal flowing in that loop with a local oscillator signal derived from the voltage controlled oscillator (7, 7') in that loop, the voltage controlled oscillator being adjusted so that in the phase locked condition the signal from the heterodyning means is equal in phase and frequency to the signal from the timing means, the receiver further comprising means to provide an output signal representative of the difference in frequency between the two local oscillator signals.
Claim 3
Dependent Claim
33 words
A receiver according to claim 1, characterised in that the remote sources are mounted in satellites in a Global Positioning System, and the signals from such sources are modulated by pseudorandom noise signals.
Claim 4
Dependent Claim
43 words
A receiver according to claim 1 or 2, characterised in that it further includes mixer means (5) for heterodyning the combined received signals with an additional local oscillator signal derived from the output of the voltage controlled oscillator (7) in the reference channel.
Claim 5
Dependent Claim
99 words
A receiver according to claim 3, characterised in that the means for separating the signals from the combined received signal includes first and second correlators (11, 13) each coupled to receive the output of the mixer means (5), the first and second correlators being connected to respond to locally generated pseudorandom noise signals which are replicas of the pseudorandum noise modulation applied to the signals in the first and second sources, respectively, the first and second correlators further being coupled to introduce their resultant despread signals into the phase locked loops of the reference and Doppler difference channels, respectively.
Claim 6
Dependent Claim
41 words
A receiver according to claim 4, characterised in that the despread signals from the correlators (11, 13) in each channel are passed through narrow bandpass amplifying means (15, 15') to attenuate noise and extraneous sidebands in the phase locked loop signals.
Claim 7
Dependent Claim
43 words
A receiver according to claim 5, characterised in that it further includes means (21, 21') to lock the phase of the signal from the bandpass amplifying means (15, 15') in each channel to the phase of the signal from the timing oscillator (23).
Claim 8
Dependent Claim
22 words
A receiver according to claim 6, characterised in that the phase locking means in each channel includes a bi-phase detector (21, 21').
Claim 9
Dependent Claim
56 words
A receiver according to any of the preceding claims characterised in that the means to provide an output signal includes output mixing means (31) coupled to receive local oscillator signals from each channel, whereby the frequency of the output signal from that mixer is equal to the difference in frequency between the two local oscillator signals.
Claim 10
Dependent Claim
52 words
A receiver according to claim 8, characterised in that it further includes means (24) to add the frequency difference signal from the mixer (31) to a signal derived from the timing oscillator means (23), whereby a positive output signal may be obtained regardless of the relative frequencies of the local oscillator signals.
References Cited (Backward Citations)
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