US4541118A
Expired / Lapsed
US
⏱️ 0.0 years remaining
SSB System with pilot coded squelch
Assignee: Motorola Solutions Inc
•
Filing: 1983-12-22
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Granted: 1985-09-10
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Expires: 2003-12-22
Abstract
Abstract A single sideband communications system conveying a message through a transmitter to one or more predetermined receivers which are enabled by a coded squelch signal unique to the predetermined receivers is disclosed. The transmitter comprises means to angle modulate both the pilot signal and the information bearing single sideband signal with the coded signal at a predetermined deviation and to transmit the resulting signal. Each receiver frequency control means tracks the frequency excursions of a selected portion of the transmitted signal up to predetermined limits so that the message can be demodulated without frequency distortion being introduced. Each receiver demodulates the coded squelch without interfering with the message demodulation or tracking functions and activates the receiver squelch of those preselected receivers.
Inventors
- 👤 Bruce C. Eastmond
- 👤 Julian H. Richardson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:09
CPC Classifications
H; H04; H04W; H04W88/00; H04W88/18; H04W88/185; H04W88/188; H04B; H04B1/00; H04B1/68; H04B14/00; H04B14/002; H04B14/006
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
129 words
A single sideband communications system for conveying a message through a transmitter to at least one predetermined receiver and employing a coded squelch signal unique to that receiver, comprising: means for generating and transmitting a radio frequency signal comprising a single sideband signal and pilot both angle modulated with the coded squelch signal at a predetermined deviation; means for receiving the radio frequency signal and tracking to predetermined limits the frequency excursions of said pilot so as to essentially eliminate frequency distortion of the message; means for demodulating the single sideband signal; and means for demodulating the coded squelch signal from said received radio frequency signal in cooperation with said frequency excursion tracking means thereby avoiding interference to said single sideband signal demodulating means and said frequency tracking means.
Claim 2
Dependent Claim
129 words
A single sideband communications system for conveying a message through a transmitter to at least one predetermined receiver and employing a coded squelch signal unique to that receiver, comprising: means for generating and transmitting a radio frequency signal comprising a single sideband signal and pilot both angle modulated with the coded squelch signal at a predetermined deviation; means for receiving the radio frequency signal and tracking to predetermined limits the frequency excursions of said pilot so as to essentially eliminate frequency distortion of the message; means for demodulating the single sideband signal; and means for demodulating the coded squelch signal from said received radio frequency signal in cooperation with said frequency excursion tracking means thereby avoiding interference to said single sideband signal demodulating means and said frequency tracking means.
Claim 3
Dependent Claim
24 words
A communications system in accordance with claim 1 wherein said coded squelch signal is one of a plurality of low frequency digital bit sequences.
Claim 4
Dependent Claim
16 words
A communications system in accordance with claim 2 wherein said predetermined deviation is approximately 34 Hz.
Claim 5
Dependent Claim
23 words
A communications system in accordance with claim 1 wherein said coded squelch signal is one of a plurality of precise audio frequency signals.
Claim 6
Dependent Claim
15 words
A communications system in accordance with claim 4 wherein said predetermined deviation is 0.15 radians.
Claim 7
Dependent Claim
15 words
A communications system in accordance with claim 1 wherein said pilot is a reduced carrier.
Claim 8
Dependent Claim
14 words
A communications system in accordance with claim 1 wherein said pilot is a tone.
Claim 9
Dependent Claim
36 words
A communications system in accordance with claim 1 further comprising means for detecting the level of the pilot and correspondingly adjustng the predetermined receiver, whereby a constant level may be presented at the predetermined receiver output.
Claim 10
Dependent Claim
18 words
A communications system in accordance with claim 1 whereby said means for tracking is a phase locked loop.
Claim 11
Dependent Claim
36 words
A communications system in accordance with claim 9 wherein said phase locked loop further comprises a loop filter which outputs, inter alia, a demodulated coded squelch signal developed in tracking said frequency excursions of said pilot.
Claim 12
Dependent Claim
66 words
A communications system in accordance with claim 10 wherein said loop filter is a network with a low pass characteristic which produces a frequency response corner at about 150 Hz to select said pilot of said radio frequency signal for tracking and to define said predetermined frequency excursion limit of said radio frequency signal thereby avoiding interference to said means for demodulating the single sideband signal.
Claim 13
Dependent Claim
29 words
A communications system in accordance with claim 1 wherein said means for receiving and tracking further comprises an IF pilot bandpasss filter with a bandwidth of approximately 300 Hz.
Claim 14
Dependent Claim
20 words
A communications system in accordance with claim 12 wherein said means for demodulating the coded squelch signal is a discriminator.
Claim 15
Dependent Claim
132 words
A receiver for processing a single sideband signal and pilot additionally angle modulated with a coded squelch signal and providing an output, comprising: means for detecting the level of the pilot and correspondingly adjusting the receiver to effect a substantially constant level at the output of the receiver; means for tracking the frequency excursions of the pilot to predetermined limits thereby allowing an essentially frequency distortion free demodulation of the single sideband signal; means, coupled to said means for tracking the frequency excursions, for demodulating the coded squelch signal whereby interference to said single sideband signal, said tracking means, and said level detecting means is essentially avoided; and means for decoding and comparing the demodulated coded squelch signal to an internally stored reference thereby activating the receiver output upon a detected match.
Claim 16
Dependent Claim
132 words
A receiver for processing a single sideband signal and pilot additionally angle modulated with a coded squelch signal and providing an output, comprising: means for detecting the level of the pilot and correspondingly adjusting the receiver to effect a substantially constant level at the output of the receiver; means for tracking the frequency excursions of the pilot to predetermined limits thereby allowing an essentially frequency distortion free demodulation of the single sideband signal; means, coupled to said means for tracking the frequency excursions, for demodulating the coded squelch signal whereby interference to said single sideband signal, said tracking means, and said level detecting means is essentially avoided; and means for decoding and comparing the demodulated coded squelch signal to an internally stored reference thereby activating the receiver output upon a detected match.
Claim 17
Dependent Claim
29 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said coded squelch signal is one of a plurality of low frequency digital bit sequences.
Claim 18
Dependent Claim
28 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said coded squelch signal is one of a plurality of precise audio frequency signals.
Claim 19
Dependent Claim
20 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said pilot is a reduced carrier.
Claim 20
Dependent Claim
19 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said pilot is a tone.
Claim 21
Dependent Claim
23 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said means for tracking is a phase locked loop.
Claim 22
Dependent Claim
38 words
A receiver for a single sideband communications system in accordance with claim 19 wherein said phase locked loop further comprises a loop filter which outputs, inter alia, a demodulated coded squelch signal developed in tracking said reduced carrier.
Claim 23
Dependent Claim
62 words
A receiver for a single sideband communications system in accordance with claim 20 wherein said loop filter is a network with a low pass characteristic which produces a frequency response corner at about 150 Hz to select a portion of said radio frequency signal for tracking and to define said predetermined frequency excursion limit thereby avoiding interference to said single sideband signal.
Claim 24
Dependent Claim
32 words
A receiver for a single sideband communications system in accordance with claim 14 wherein said means for tracking further comprises an IF pilot bandpass filter with a bandwidth of approximately 300 Hz.
Claim 25
Dependent Claim
25 words
A receiver for a single sideband communications system in accordance with claim 22 wherein said means for demodulating the coded squelch signal is a discriminator.
Claim 26
Dependent Claim
87 words
A transmitter for transmitting a message and a coded squelch for enabling at least one predetermined receiver in a single sideband communications system, comprising: means for creating a single sideband signal modulated by the message; means for generating a pilot and combining it with said single sideband signal; means for further combining said combined signal with a coded squelch signal to derive a single sideband radio frequency signal angle modulated at a predetermined deviation with said coded squelch signal; and means for transmitting said radio frequency signal.
Claim 27
Dependent Claim
87 words
A transmitter for transmitting a message and a coded squelch for enabling at least one predetermined receiver in a single sideband communications system, comprising: means for creating a single sideband signal modulated by the message; means for generating a pilot and combining it with said single sideband signal; means for further combining said combined signal with a coded squelch signal to derive a single sideband radio frequency signal angle modulated at a predetermined deviation with said coded squelch signal; and means for transmitting said radio frequency signal.
Claim 28
Dependent Claim
23 words
A transmitter in accordance with claim 24 wherein said coded squelch signal is one of a plurality of low frequency digital bit sequences.
Claim 29
Dependent Claim
15 words
A transmitter in accordance with claim 25 wherein said predetermined deviation is approximately 34 Hz.
Claim 30
Dependent Claim
22 words
A transmitter in accordance with claim 24 wherein said coded squelch signal is one of a plurality of precise audio frequency signals.
Claim 31
Dependent Claim
14 words
A transmitter in accordance with claim 27 wherein said predetermined deviation is 0.15 radians.
Claim 32
Dependent Claim
14 words
A transmitter in accordance with claim 24 wherein said pilot is a reduced carrier.
Claim 33
Dependent Claim
13 words
A transmitter in accordance with claim 24 wherein said pilot is a tone.
Claim 34
Independent Claim
128 words
A method of enabling by coded squelch at least one predetermined receiver to receive a single sideband modulated message from a transmitter and deliver the message to an output, comprising the steps of: deriving a radio frequency signal comprising a pilot and the message carrying single sideband signal angle modulated with the coded squelch signal at a predetermined deviation; transmitting the resulting radio frequency signal; receiving and tracking the frequency excursions of said pilot of said radio frequency signal to predetermined limits; demodulating the single sideband modulated message essentially frequency distortion-free as a result of said frequency excursion tracking; and demodulating said coded squelch signal from said radio frequency signal essentially without interference to said single sideband message demodulating step as a result of said frequency tracking step.
Claim 35
Independent Claim
128 words
A method of enabling by coded squelch at least one predetermined receiver to receive a single sideband modulated message from a transmitter and deliver the message to an output, comprising the steps of: deriving a radio frequency signal comprising a pilot and the message carrying single sideband signal angle modulated with the coded squelch signal at a predetermined deviation; transmitting the resulting radio frequency signal; receiving and tracking the frequency excursions of said pilot of said radio frequency signal to predetermined limits; demodulating the single sideband modulated message essentially frequency distortion-free as a result of said frequency excursion tracking; and demodulating said coded squelch signal from said radio frequency signal essentially without interference to said single sideband message demodulating step as a result of said frequency tracking step.
Claim 36
Dependent Claim
35 words
A method in accordance with the method of claim 31 wherein said coded squelch signal is one of a plurality of low frequency digital bit sequences modulated at a predetermined deviation of approximately 34 Hz.
Claim 37
Dependent Claim
33 words
A method in accordance with the method of claim 31 wherein said coded squelch signal is one of a plurality of precise audio signals modulated at a predetermined deviation of approximately 0.15 radians.
Claim 38
Dependent Claim
36 words
A method in accordance with claim 31 further comprising the step of detecting the level of carrier of said single sideband signal and correspondingly adjusting the receiver to present a constant level at the receiver output.
Claim 39
Dependent Claim
17 words
A method in accordance with the method of claim 31 wherein said pilot is a reduced carrier.
Claim 40
Dependent Claim
16 words
A method in accordance with the method of claim 31 wherein said pilot is a tone.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-09-09 | 1989-03-11 | 1989-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-09-09 | 1993-03-11 | 1993-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-09-09 | 1997-03-11 | 1997-09-10 | $7700.00 | Window Closed / Lapsed |