Phase sensitive demodulator

Claim 2

A phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: means for tracking and storing the instan-taneous value of said modulated signal, said track and store means including input, output and switching terminals and having said modulated signal applied to said input terminal and providing the instantaneously stored value of said modulated signal at said output terminal; and means for producing a switching signal from said carrier, said switching signal including periodic short duration pulses derived from respective cycles of said carrier, each of said pulses being produced at a predetermined polarity peak of a corresponding cycle of said carrier, and said switching signal being applied to said switching terminal to operate said track and store means, said switching signal producing means comprising means for shifting the phase of said carrier by 90*, means for producing a squared signal from said shifted carrier, and means for producing said short duration pulses from respective cycles of said squared signal, and said track and store means comprising an input resistor having an end connecting with said input terminal, an integrating operational amplifier having an input and an output connecting with said output terminal, a feedback resistor connecting said amplifier output to the other end of said input resistor, and switching means for connecting said amplifier input directly to said other end of said input resistor, said switching means including a field effect transistor having a very low resistance when rendered conductive by each of said switching pulses, and said switching means being normally open and operatively responsive to said switching pulses to connect said amplifier input periodically to said input resistor whereby said amplifier tracks the value of said modulated signal when said switching means is closed and stores the last sampled value of said modulated signal when said switching means is open, to produce an output signal at said output terminal approximating the envelope of said modulated signal whereby said information signal is substantially obtained.

Claim 3

The invention as defined in claim 1 wherein said squared signal producing means includes a Schmitt trigger, and said short duration pulse producing means includes a one-shot multivibrator.

Claim 4

The invention as defined in claim 2 further comprising means for protecting said transistor from over-voltages applied thereto, said protective means including a pair of oppositely oriented diodes connecting said other end of said input resistor to ground.

Claim 5

A doublE-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: first means for tracking and storing the instantaneous value of said modulated signal, said first track and store means including first input, output and switching terminals and having said modulated signal applied to said first input terminal and providing the instantaneously stored value of said modulated signal at said first output terminal; second means for tracking and storing the instantaneous value of said modulated signal, said second track and store means including second input, output and switching terminals and having said modulated signal applied in opposite phase to said second input terminal and providing the instantaneously stored value of said opposite phase modulated signal at said second output terminal; and means for producing first and second switching signals from said carrier, said first switching signal being applied to said first switching terminal to operate said first track and store means to produce a first output signal at said first output terminal and said second switching signal being applied to said second switching terminal to operate said second track and store means to produce a second output signal at said second output terminal, said second output signal complementing said first output signal and providing a combined output signal closely approximating the envelope of said modulated signal whereby said information signal can be substantially obtained.

Claim 6

A doublE-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: first means for tracking and storing the instantaneous value of said modulated signal, said first track and store means including first input, output and switching terminals and having said modulated signal applied to said first input terminal and providing the instantaneously stored value of said modulated signal at said first output terminal; second means for tracking and storing the instantaneous value of said modulated signal, said second track and store means including second input, output and switching terminals and having said modulated signal applied in opposite phase to said second input terminal and providing the instantaneously stored value of said opposite phase modulated signal at said second output terminal; and means for producing first and second switching signals from said carrier, said first switching signal being applied to said first switching terminal to operate said first track and store means to produce a first output signal at said first output terminal and said second switching signal being applied to said second switching terminal to operate said second track and store means to produce a second output signal at said second output terminal, said second output signal complementing said first output signal and providing a combined output signal closely approximating the envelope of said modulated signal whereby said information signal can be substantially obtained.

Claim 7

The invention as defined in claim 4 wherein each of said first and second switching signals includes periodic short duration pulses derived from respective cycles of said carrier, each of said pulses of said first switching signal being produced at a positive peak of a corresponding cycle of said carrier and each of said pulses of said second switching signal being produced at a negative peak of a corresponding cycle of said carrier.

Claim 8

The invention as defined in claim 5 wherein each of said first and second track and store means comprises an input resistor having an end connecting with said corresponding input terminal, an integrating operational amplifier having an input and an output connecting with said corresponding output terminal, a feedback resistor connecting said integrating amplifier output to the other end of said input resistor, and switching means for connecting said integrating amplifier input to said other end of said input resistor, said switching means being normally open and operatively responsive to said switching pulses to connect said integrating amplifier input periodically to said input resistor whereby said integrating amplifier tracks the value of said modulated signal when said switching means is closed and stores the last sampled value of said modulated signal when said switching means is open, to produce an output signal at said corresponding output terminal approximating the envelope of said modulated signal.

Claim 9

A double-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: first means for tracking and storing the instantaneous value of said modulated signal, said first track and store means including first input, output and switching terminals and having said modulated signal applied in one phase to said first input terminal and providing the instantaneously stored value of said modulated signal at said first output terminal; second means for tracking and storing the instantaneous value of said modulated signal, said second track and store means including second input, output and switching terminals and having said modulated signal applied in an opposite phase to said second input terminal and providing the instantaneously stored value of said opposite phase modulated signal at said second output terminal; and means for producing first and Second switching signals from said carrier, said first switching signal being applied to said first switching terminal to operate said first track and store means to produce a first output signal at said first output terminal and said second switching signal being applied to said second switching terminal to operate said second track and store means to produce a second output signal at said second output terminal, said second output signal complementing said first output signal and providing a combined output signal closely approximating the envelope of said modulated signal whereby said information signal can be substantially obtained, each of said first and second switching signals including periodic short duration pulses derived from respective cycles of said carrier, each of said pulses of said first switching signal being produced at a positive peak of a corresponding cycle of said carrier, and each of said pulses of said second switching signal being produced at a negative peak of a corresponding cycle of said carrier, and said first and second track and store means comprising first and second input resistors each having an end connecting with a corresponding one of said first and second input terminals, a single integrating operational amplifier having an input and an output and connected in both of said first and second track and store means for producing and combining said first and second output signals into said combined output signal, first and second feedback resistors connecting said integrating amplifier output to the other end of a corresponding one of said first and second input resistors, and first and second switching means for connecting said integrating amplifier input to said other end of a corresponding one of said first and second input resistors, said first and second output terminals being combined into a single output terminal connected to said integrating amplifier output, and said first and second switching means being normally open and responsive to said first and second pulses, respectively, to connect said integrating amplifier input periodically to said first and second input resistors whereby said integrating amplifier tracks the value of said modulated signal when one of said switching means is closed and stores the last sampled value of said modulated signal when both of said switching means are open, to produce said combined output signal at said integrating amplifier output approximating the envelope of said modulated signal.

Claim 10

A double-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: first means for tracking and storing the instantaneous value of said modulated signal, said first track and store means including first input, output and switching terminals and having said modulated signal applied in one phase to said first input terminal and providing the instantaneously stored value of said modulated signal at said first output terminal; second means for tracking and storing the instantaneous value of said modulated signal, said second track and store means including second input, output and switching terminals and having said modulated signal applied in an opposite phase to said second input terminal and providing the instantaneously stored value of said opposite phase modulated signal at said second output terminal; and means for producing first and Second switching signals from said carrier, said first switching signal being applied to said first switching terminal to operate said first track and store means to produce a first output signal at said first output terminal and said second switching signal being applied to said second switching terminal to operate said second track and store means to produce a second output signal at said second output terminal, said second output signal complementing said first output signal and providing a combined output signal closely approximating the envelope of said modulated signal whereby said information signal can be substantially obtained, each of said first and second switching signals including periodic short duration pulses derived from respective cycles of said carrier, each of said pulses of said first switching signal being produced at a positive peak of a corresponding cycle of said carrier, and each of said pulses of said second switching signal being produced at a negative peak of a corresponding cycle of said carrier, and said first and second track and store means comprising first and second input resistors each having an end connecting with a corresponding one of said first and second input terminals, a single integrating operational amplifier having an input and an output and connected in both of said first and second track and store means for producing and combining said first and second output signals into said combined output signal, first and second feedback resistors connecting said integrating amplifier output to the other end of a corresponding one of said first and second input resistors, and first and second switching means for connecting said integrating amplifier input to said other end of a corresponding one of said first and second input resistors, said first and second output terminals being combined into a single output terminal connected to said integrating amplifier output, and said first and second switching means being normally open and responsive to said first and second pulses, respectively, to connect said integrating amplifier input periodically to said first and second input resistors whereby said integrating amplifier tracks the value of said modulated signal when one of said switching means is closed and stores the last sampled value of said modulated signal when both of said switching means are open, to produce said combined output signal at said integrating amplifier output approximating the envelope of said modulated signal.

Claim 11

The invention as defined in claim 7 further comprising means for detecting an overload condition in said demodulator.

Claim 12

The invention as defined in claim 5 further comprising a summing operational amplifier having an input and an output, and first and second adder resistors respectively connecting said first and second output terminals to said summing amplifier input whereby said first and second output signals are summed by said summing amplifier to provide said combined output signal at its output.

Claim 13

The invention as defined in claim 6 further comprising a summing operational amplifier having an input and an output, and first and second adder resistors respectively connecting said first and second output terminals to said summing amplifier input whereby said first and second output signals are summed by said summing amplifier to provide said combined output signal at its output.

Claim 14

The invention as defined in claim 7 further comprising a transformer means for applying said modulated signal in one phase to said first input terminal and in an opposite phase to said second input terminal.

Claim 15

The invention as defined in claim 7 further comprising a differential input operational amplifier, and an inverter, said differential amplifier applying said modulated signal in one phase to said first input terminal and to said inverter which applies said modulated signal in an opposite phase to said second input terminal.

Claim 16

The invention as defined in claim 7 further comprising an ouTput filter operational amplifier connecting said integrating amplifier output to said single output terminal, said filter amplifier including a capacitor electively connectable in a feedback circuit thereof to smooth out steps in said combined output signal appearing at said single output terminal.

Claim 17

A double-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: means for tracking and storing the instantaneous value of said modulated signal, said track and store means including first and second input means, storing means, and first and second switching means for respectively connecting said first and second input means to said storing means, said first input means having said modulated signal applied in one phase thereto and said second input means having said modulated signal applied in an opposite phase thereto, and said first and second switching means being normally open and operatively responsive respectively to applied first and second switching signals to connect said first and second input means periodically to said storing means; and means for producing said first and second switching signals from respective polarity portions of each cycle of said carrier, said first and second switching signals being alternately applied to said first and second switching means to operate the same and provide the instantaneous value of said modulated signal to said storing means which tracks the value of said modulated signal when either of said first and second switching means is closed and stores the last sampled value thereof when both of said first and second switching means are open, whereby said modulated signal is sampled twice for each cycle of said carrier and said storing means provides an output signal closely approximating the envelope of said modulated signal so that said information signal can be accurately obtained.

Claim 18

A double-ended phase sensitive demodulator for demodulating a modulated carrier signal produced by modulating a carrier with an information signal, said demodulator comprising: means for tracking and storing the instantaneous value of said modulated signal, said track and store means including first and second input means, storing means, and first and second switching means for respectively connecting said first and second input means to said storing means, said first input means having said modulated signal applied in one phase thereto and said second input means having said modulated signal applied in an opposite phase thereto, and said first and second switching means being normally open and operatively responsive respectively to applied first and second switching signals to connect said first and second input means periodically to said storing means; and means for producing said first and second switching signals from respective polarity portions of each cycle of said carrier, said first and second switching signals being alternately applied to said first and second switching means to operate the same and provide the instantaneous value of said modulated signal to said storing means which tracks the value of said modulated signal when either of said first and second switching means is closed and stores the last sampled value thereof when both of said first and second switching means are open, whereby said modulated signal is sampled twice for each cycle of said carrier and said storing means provides an output signal closely approximating the envelope of said modulated signal so that said information signal can be accurately obtained.

Claim 19

The invention as defined in claim 14 further comprising means for detecting an overload condition in said demodulator.

Claim 20

The invention as defined in claim 14 wherein said first and second input means comprises first and second input resistors, said storing means comprises an integrating operational amplifier including first and second feedback resistors connecting its output to respective common junctions between said first and second input means and said first and second switching means, and said first and second switching means comprises first and second field effect transistors which have a very low resistance when rendered conductive respectively by said first and second switching signals.

Claim 21

The invention as defined in claim 16 wherein said first switching signal includes periodic short duration pulses derived from corresponding portions of one polarity of said cycles of said carrier and said second switching signal includes periodic short duration pulses derived from corresponding portions of an opposite polarity of said cycles of said carrier, and said first and second switching signals producing means includes means for shifting the phase of said carrier by 90*, means for producing first and second squared signals of opposite phases from said shifted carrier, and means for producing said short duration pulses of said first switching signal from respective cycles of said first squared signal and of said second switching signal from respective cycles of said second squared signal.

Claim 22

The invention as defined in claim 17 wherein said first squared signal producing means comprises a Schmitt trigger, said second squared signal producing means comprises a squared signal inverter connected to the output of said Schmitt trigger, and said short duration pulse producing means comprises first and second one-shot multivibrators responsively connected respectively to said Schmitt trigger and said squared signal inverter.

Claim 23

The invention as defined in claim 16 further comprising first and seconD means for protecting said first and second transistors respectively from overvoltages applied thereto, said first and second protective means including first and second pairs of oppositely oriented diodes connecting respective common junctions between said first and second input means and said first and second switching means to ground.

Claim 24

The invention as defined in claim 19 further comprising a differential input operational amplifier, and a differential signal inverter, said differential amplifier applying said modulated signal in one phase to said first input means and to said differential signal inverter which applies said modulated signal in an opposite phase to said second input means.

Claim 25

The invention as defined in claim 20 further comprising an output filter operational amplifier connected to said integrating amplifier output, said filter amplifier including a capacitor electively connectable in a feedback circuit thereof to smooth out steps in said output signal of said integrating amplifier.

Claim 26

The invention as defined in claim 21 further comprising means for detecting an overload condition in said demodulator.