US3946313A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Combined encoder-decoder apparatus having a single active filter
Assignee: Motorola Solutions Inc
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Filing: 1974-10-15
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Granted: 1976-03-23
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Expires: 1994-10-15
Abstract
Abstract A combined encoder-decoder for use in two-way radio systems. The apparatus is operable in an encoder mode to provide tone oscillations during operation of the radio apparatus in the transmit mode and also in a decoder mode to provide a control signal in response to a received tone signal of a particular frequency during operation of the radio apparatus in the receive mode. The encoder-decoder includes a single active filter and a feedback circuit selectively coupled to the filter to form an oscillator for producing the tone oscillations in the encoder mode of operation. An input amplifier/limiter is enabled to apply received tone signals to the active filter during decoder operation. A control circuit responsive to operation of the radio apparatus is coupled to the feedback circuit and to the input circuit so as to selectively enable the feedback circuit during encoder operation and the input circuit during decoder operation. The control circuit causes the feedback circuit to provide increased gain upon initiation of encoder operation so that oscillations build up rapidly. The output of the active filter is applied to a detector to which two integration circuits are connected, the first being enabled during encoder operation and the second during decoder operation. The first integration circuit responds when the signal builds up to control the feedback circuit to reduce the gain to the desired level. The second integration circuit is enabled during decoder operation so that when the signal of a particular frequency is applied to the active filter a control signal is produced which is utilized to enable the audio circuit of the receiver. The control circuit also responds to the switching of the circuit between encoder and decoder modes of operation to increase the bandwidth of the active filter to prevent encoder tone overshoot during the receive-transmit transition and to prevent decoder falsing during the transmit-receive transition.
Inventors
- 👤 Kenneth J. Krolik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:27
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
227 words
Combined encoder-decoder apparatus for use in two-way radio equipment having a transmitter and receiver and operable in an encoder mode for providing tone oscillations during operation of the radio transmitter, and in a decoder mode for providing a control signal in response to a received tone signal of a particular frequency during operation of the radio receiver, such apparatus including in combination: active filter means with an input, output, and a control terminal responsive to an applied potential to increase the bandwidth of said active filter means; feedback means interconnecting said input and said output of said active filter means for producing tone oscillations; input means coupled to said active filter input for applying received tone signals thereto; and control circuit means coupled to said active filter means and responsive to the operation of the radio transmitter for enabling said feedback means to operate said apparatus in encoder mode and produce tone oscillations, and further responsive to the operation of the radio receiver for enabling said input means to pass tone signals and operate said apparatus in decoder mode and produce a control signal, said control means further applying a predetermined potential to said active filter control terminal during transition of the radio equipment between said different modes to momentarily increase the bandwidth of said active filter means whereby stored energy present therein may be rapidly dissipated.
Claim 2
Dependent Claim
227 words
Combined encoder-decoder apparatus for use in two-way radio equipment having a transmitter and receiver and operable in an encoder mode for providing tone oscillations during operation of the radio transmitter, and in a decoder mode for providing a control signal in response to a received tone signal of a particular frequency during operation of the radio receiver, such apparatus including in combination: active filter means with an input, output, and a control terminal responsive to an applied potential to increase the bandwidth of said active filter means; feedback means interconnecting said input and said output of said active filter means for producing tone oscillations; input means coupled to said active filter input for applying received tone signals thereto; and control circuit means coupled to said active filter means and responsive to the operation of the radio transmitter for enabling said feedback means to operate said apparatus in encoder mode and produce tone oscillations, and further responsive to the operation of the radio receiver for enabling said input means to pass tone signals and operate said apparatus in decoder mode and produce a control signal, said control means further applying a predetermined potential to said active filter control terminal during transition of the radio equipment between said different modes to momentarily increase the bandwidth of said active filter means whereby stored energy present therein may be rapidly dissipated.
Claim 3
Dependent Claim
53 words
Combined encoder-decoder apparatus in accordance with claim 1 wherein said control means includes a detector coupled to said active filter output, and means coupled to said detector and responsive thereto during decoder mode operation to provide a control signal upon the occurrence of a tone signal of a predetermined amplitude and time duration.
Claim 4
Dependent Claim
90 words
Combined encoder-decoder apparatus in accordance with claim 1 wherein said control means includes a detector coupled to said active filter output for providing a d-c voltage in accordance with the amplitude of the tone signal at said active filter output, and first and second integration circuits connected to said detector, each integration circuit being operative to produce a control signal upon detector voltage reaching a predetermined level for a given time duration, and means for selectively enabling said first and second integration circuits for respective encoder and decoder mode operation.
Claim 5
Dependent Claim
73 words
Combined encoder-decoder apparatus in accordance with claim 3 wherein said control means includes means responsive to said control signals from said first and second integrator circuits for controlling the potential applied by said control means to said active filter control terminal, with a control signal indicating operation in one of the encoder and decoder modes of operation causing said potential to change so that the bandwidth of said active filter means is reduced.
Claim 6
Dependent Claim
271 words
Combined encoder-decoder apparatus for use in two-way radio equipment having a transmitter and receiver and operable in an encoder mode for providing tone oscillations during operation of the radio transmitter, and in a decoder mode for providing a control signal in response to a received tone signal of a particular frequency during operation of the radio receiver, such apparatus including in combination: active filter means with input and output; feedback means interconnecting said input and said output of said active filter means for producing tone oscillations, said feedback means further including bandwidth control means which when actuated is effective to increase the bandwidth of said active filter means to a predetermined amount; input means coupled to said active filter input for applying received tone signals thereto; gain control means for causing said tone oscillations produced by said active filter means during encoder mode operation to initially occur at a boosted gain rate until reaching a predetermined level and thereafter reducing and maintaining said tone oscillations at a given lower gain level; and control circuit means coupled to said active filter means and responsive to the operation of the radio transmitter for selectively enabling said feedback means whereby said active filter means produces tone oscillations for encoder mode operation, and further responsive to the operation of the radio receiver for enabling said input means to pass tone signals for decoder mode operation, said control means further including means for actuating said bandwidth control means for a predetermined time duration whenever said active filter is caused to change operating modes whereby stored energy present in said active filter means may be rapidly dissipated.
Claim 7
Dependent Claim
271 words
Combined encoder-decoder apparatus for use in two-way radio equipment having a transmitter and receiver and operable in an encoder mode for providing tone oscillations during operation of the radio transmitter, and in a decoder mode for providing a control signal in response to a received tone signal of a particular frequency during operation of the radio receiver, such apparatus including in combination: active filter means with input and output; feedback means interconnecting said input and said output of said active filter means for producing tone oscillations, said feedback means further including bandwidth control means which when actuated is effective to increase the bandwidth of said active filter means to a predetermined amount; input means coupled to said active filter input for applying received tone signals thereto; gain control means for causing said tone oscillations produced by said active filter means during encoder mode operation to initially occur at a boosted gain rate until reaching a predetermined level and thereafter reducing and maintaining said tone oscillations at a given lower gain level; and control circuit means coupled to said active filter means and responsive to the operation of the radio transmitter for selectively enabling said feedback means whereby said active filter means produces tone oscillations for encoder mode operation, and further responsive to the operation of the radio receiver for enabling said input means to pass tone signals for decoder mode operation, said control means further including means for actuating said bandwidth control means for a predetermined time duration whenever said active filter is caused to change operating modes whereby stored energy present in said active filter means may be rapidly dissipated.
Claim 8
Dependent Claim
23 words
Combined encoder-decoder apparatus in accordance with claim 5 wherein said active filter means comprises at least a pair of serially connected operational amplifiers.
Claim 9
Dependent Claim
41 words
Combined encoder-decoder apparatus in accordance with claim 6 wherein said bandwidth control means includes a resistance interposed in said feedback means of said active filter and which further includes a transistor device having its emitter-collector circuit in parallel with said resistance.
Claim 10
Dependent Claim
79 words
Combined encoder-decoder apparatus in accordance with claim 5 wherein said gain control means includes a controllable amplifier in said feedback means having variable impedance means in the output circuit thereof which when actuated is effective to reduce the gain of said controllable amplifier a predetermined amount, said control means further including means for actuating said variable impedance element comprising detector means for receiving tone oscillations, and integrator delay means interposed between said detector means and said variable impedance means.
Claim 11
Dependent Claim
40 words
Combined encoder-decoder apparatus in accordance with claim 8 wherein said variable impedance means includes a resistance element in parallel with the emitter-collector circuit of a transistor device, the base thereof being coupled to the output of said integrator/delay circuit means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-23 | 1979-09-22 | 1980-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-23 | 1983-09-22 | 1984-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-23 | 1987-09-22 | 1988-03-23 | $7700.00 | Window Closed / Lapsed |