US3573382A
Expired / Lapsed
US
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A stereophonic receiver muting means with substitution of a dc circuit for an ac circuit
Assignee: Motorola Solutions Inc
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Filing: 1969-02-06
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Granted: 1971-04-06
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Expires: 1989-02-06
Abstract
Abstract A silicon monolithic integrated circuit stereo multiplex receiver includes a gated symmetrical demodulator for providing the desired left and right audio output signals. A second demodulator is supplied with the same composite input signal supplied to the first demodulator, but substantially attenuated, with the second demodulator providing output signals 180* out of phase with the signal supplied by the first demodulator; and the outputs of the two demodulators are combined so that the crosstalk components are effectively eliminated. A provision also is made for interstation audio muting and for stereo muting by the direct substitution of equivalent DC loads for the AC amplifiers normally responding to the signals, so that transientless muting is achieved. In order to control the muting and to provide a driver for the stereo indicator lamp, trigger circuits having predetermined hysteresis of operation are formed as part of the integrated circuit. Improved symmetrical drive for the demodulator circuit is obtained by feeding the 19 k.c. pilot signal to the doubler circuit across a string of diodes which logarithmically compress signals that would tend to overdrive the doubler transistor amplifier. A filter at the emitter of the doubler amplifier establishes a DC level which is used to fire the indicator lamp trigger circuit to indicate stereo signals are being received and also serves to self-bias the doubler amplifier to further prevent its being overdriven.
Inventors
- 👤 James H Feit
- 👤 Francis H Hilbert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:10
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/22; H03D1/2209; H03D1/2227
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
128 words
An AC signal processing system including in combination: first circuit means for utilizing AC signals; a source of AC signals; input means coupling the source of AC signals and the first circuit means for supplying said AC signals to the first circuit means, the output of the input means having a predetermined DC operating level; DC circuit means providing a DC operating level which is substantially the same as said predetermined DC operating level of the input means; and muting means for substituting the output of the DC circuit means for the output of the input means supplied to the first circuit means so that muting of the first circuit means for AC signals is accomplished without a change in the DC operating level at the input thereof.
Claim 2
Dependent Claim
128 words
An AC signal processing system including in combination: first circuit means for utilizing AC signals; a source of AC signals; input means coupling the source of AC signals and the first circuit means for supplying said AC signals to the first circuit means, the output of the input means having a predetermined DC operating level; DC circuit means providing a DC operating level which is substantially the same as said predetermined DC operating level of the input means; and muting means for substituting the output of the DC circuit means for the output of the input means supplied to the first circuit means so that muting of the first circuit means for AC signals is accomplished without a change in the DC operating level at the input thereof.
Claim 3
Dependent Claim
29 words
The combination according to claim 1 further including means controlled by the muting means for disabling the input means to render the input means nonresponsive to said AC signals.
Claim 4
Dependent Claim
53 words
The combination according to claim 1 wherein the input means includes transistor means supplied with said AC signals and biased to operate at a predetermined DC level and wherein the DC circuit means also includes transistor means supplied with a biasing potential and biased to operate at substantially the same predetermined DC level.
Claim 5
Dependent Claim
35 words
The combination according to claim 1 further including monitoring means responsive to the signal level of said AC signals for causing operation of the muting means in response to signal levels below a predetermined amount.
Claim 6
Dependent Claim
37 words
The combination according to claim 1 wherein said AC signal processing system includes an audio frequency signal processing system, said signal source is an audio frequency signal source, and said first circuit means utilizes audio frequency signals.
Claim 7
Dependent Claim
51 words
The combination according to claim 1 wherein said AC signal processing system processes stereophonic FM signals including, in part, a pilot signal, and wherein the first circuit means is a pilot signal separating circuit with the source of AC signals being, at least in part, a source of said pilot signal.
Claim 8
Dependent Claim
112 words
The combination according to claim 1 wherein the first circuit means, input means and muting means all are part of an integrated circuit and wherein the input means includes an input transistor supplied with said AC signals and biased to a predetermined DC operating level, the DC circuit means includes a further transistor biased to substantially said same predetermined DC operating level, and the DC circuit means is connected to the circuit means for utilizing AC signals in the same manner as the input means when said DC circuit means is substituted for said input means, so that the DC operating level of said integrated circuit is substantially unchanged by said substitution.
Claim 9
Dependent Claim
83 words
The combination according to claim 7 wherein the input transistor and the further transistor each include base, emitter, and collector electrodes, the collector electrodes being connected together to the first circuit means, and the emitter electrodes being connected together, with the input transistor normally being conductive and supplied with said AC signals and a DC biasing potential on the base thereof and the further transistor normally being nonconductive, operation of the muting means rendering the further transistor conductive and the input transistor nonconductive.
Claim 10
Dependent Claim
67 words
The combination according to claim 7 wherein the input transistor and the further transistor each include at least input and output electrodes with the output electrodes being connected in common to the first circuit means, the input electRode of the input transistor being connected to the source of AC signals, and the input electrode of the further transistor being controlled by DC signals from the muting means.
Claim 11
Dependent Claim
140 words
A muting circuit for a signal wave receiver including in combination: a load; input signal responsive circuit means operated at a predetermined DC operating level for supplying signals to the load; DC circuit means connected to the load in parallel with the input signal responsive means; and switching means having first and second output conditions and connected to the input signal responsive circuit means and the DC circuit means for rendering said input signal responsive means conductive and for rendering the DC circuit means nonconductive when the switching means is in its first output condition, and for rendering the input signal responsive means nonconductive and for rendering the DC circuit means conductive when the switching means is in its second output condition, the DC current level through the load being the same irrespective of which circuit means is rendered conductive.
Claim 12
Dependent Claim
140 words
A muting circuit for a signal wave receiver including in combination: a load; input signal responsive circuit means operated at a predetermined DC operating level for supplying signals to the load; DC circuit means connected to the load in parallel with the input signal responsive means; and switching means having first and second output conditions and connected to the input signal responsive circuit means and the DC circuit means for rendering said input signal responsive means conductive and for rendering the DC circuit means nonconductive when the switching means is in its first output condition, and for rendering the input signal responsive means nonconductive and for rendering the DC circuit means conductive when the switching means is in its second output condition, the DC current level through the load being the same irrespective of which circuit means is rendered conductive.
Claim 13
Dependent Claim
78 words
The combination according to claim 10 wherein the input signal circuit responsive means and the DC circuit means each include electronic amplifying means with input and output electrodes, the output electrodes being connected in common to the load, and the input electrodes being controlled by the switching means, with the input electrode of the signal responsive amplifying means being further controlled by the received input signal, said amplifying means operating at a predetermined DC level when rendered conductive.
Claim 14
Dependent Claim
39 words
The combination according to claim 11 wherein the amplifying means are transistors of the same conductivity type and the switching means provides the same DC bias to the input electrodes of the transistors when the transistors are rendered conductive.
Claim 15
Dependent Claim
180 words
In a stereophonic FM receiver of the type for receiving composite stereophonic multiplex signals including audio frequency signals, a pilot signal and a modulated subcarrier signal with circuit means for separating the pilot signal from the remainder of the composite signal and with audio circuit means for processing said audio frequency signals for application to the output of said receiver, said receiver further including switching circuit means for muting the pilot signal and the audio frequency signal, said switching circuit means including in combination: pilot signal muting means responsive to a first output from said switching circuit means and connected to the pilot signal separating circuit means for substituting a DC load having substantially the same DC operating level as the pilot signal separating circuit means for the pilot signal separating circuit means; and means responsive to a second output of the switching circuit means and connected to the audio circuit means for substituting for the audio frequency circuit means a DC load having substantially the same DC operating level as the DC operating level of the audio circuit means.
Claim 16
Dependent Claim
180 words
In a stereophonic FM receiver of the type for receiving composite stereophonic multiplex signals including audio frequency signals, a pilot signal and a modulated subcarrier signal with circuit means for separating the pilot signal from the remainder of the composite signal and with audio circuit means for processing said audio frequency signals for application to the output of said receiver, said receiver further including switching circuit means for muting the pilot signal and the audio frequency signal, said switching circuit means including in combination: pilot signal muting means responsive to a first output from said switching circuit means and connected to the pilot signal separating circuit means for substituting a DC load having substantially the same DC operating level as the pilot signal separating circuit means for the pilot signal separating circuit means; and means responsive to a second output of the switching circuit means and connected to the audio circuit means for substituting for the audio frequency circuit means a DC load having substantially the same DC operating level as the DC operating level of the audio circuit means.
Claim 17
Dependent Claim
56 words
The combination according to claim 13 further including means for monitoring the signal level of the received FM signals and providing first and second control signals to the switching circuit whenever the input signal level attains first and second predetermined levels, said control signals causing said switching circuit to produce said first and second outputs respectively.
Claim 18
Dependent Claim
93 words
The combination according to claim 13 wherein the pilot signal separation circuit means and the audio circuit means include active components in the form of integrated circuit transistors responsive respectively to the pilot signal and the audio frequency signals, and wherein the respective DC loads substituted for said pilot signal separating circuit means and said audio circuit means also include integrated circuit transistor means operated at a constant DC level to render the receiver nonresponsive to said pilot signal separating Means and said audio circuit means whenever said DC load is substituted therefor.
Claim 19
Dependent Claim
206 words
In a stereophonic FM receiver of the type for receiving composite stereophonic multiplex signals including a pilot signal and also operating in response to monaural FM signals, a circuit for automatically switching the mode of operation from stereophonic reception to monaural reception whenever the input signal level drops below a predetermined level, said automatic switching circuit including in combination: means for monitoring the signal level of the received FM signals; switching means responsive to the output of the signal monitoring means for producing an output signal whenever the signal from the output of the monitoring means indicates the received signal level is below a predetermined value; means having a predetermined DC operating level for separating the pilot signal from the remainder of the composite signal received by the receiver; means responsive to the output of the pilot signal separating means for producing output signals indicative of the receipt of stereophonic signals; and means connected to the pilot signal separating means and controlled by the output of the switching means for substituting a DC load having said DC operating level for the pilot signal separating means in response to the output signal from the switching means indicating that the received signal level is below said predetermined value.
Claim 20
Dependent Claim
206 words
In a stereophonic FM receiver of the type for receiving composite stereophonic multiplex signals including a pilot signal and also operating in response to monaural FM signals, a circuit for automatically switching the mode of operation from stereophonic reception to monaural reception whenever the input signal level drops below a predetermined level, said automatic switching circuit including in combination: means for monitoring the signal level of the received FM signals; switching means responsive to the output of the signal monitoring means for producing an output signal whenever the signal from the output of the monitoring means indicates the received signal level is below a predetermined value; means having a predetermined DC operating level for separating the pilot signal from the remainder of the composite signal received by the receiver; means responsive to the output of the pilot signal separating means for producing output signals indicative of the receipt of stereophonic signals; and means connected to the pilot signal separating means and controlled by the output of the switching means for substituting a DC load having said DC operating level for the pilot signal separating means in response to the output signal from the switching means indicating that the received signal level is below said predetermined value.
Claim 21
Dependent Claim
67 words
The combination according to claim 16 wherein the pilot signal separating means is disabled by the switching means when the received signal level is below said predetermined value, so that the receiver is rendered insensitive to the pilot signal while at the same time the DC operating levels of the circuit remain substantially unchanged in order to provide transientless muting of stereophonic signals for low signal levels.
Claim 22
Dependent Claim
53 words
The combination according to claim 16 wherein the switching means is operated to remove said output signal whenever the signal from the output of the monitoring means indicates the received signal level is above a second predetermined value which is higher than said predetermined value casing the switching to produce said output signal.
References Cited (Backward Citations)
US3174102A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-05 | 1974-10-05 | 1975-04-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-05 | 1978-10-05 | 1979-04-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-05 | 1982-10-05 | 1983-04-06 | $7700.00 | Window Closed / Lapsed |