Envelope detector including sample-and-hold circuit controlled by preceding carrier pulse peak(s)
First Claim
1. A synchronous sampling envelope detector, comprising:
- an input for receiving a carrier waveform which includes a series of pulses; and
means, responsive to a detected maximum-magnitude value of a present pulse of the carrier waveform, for sampling an instantaneous value of the carrier waveform at a time which is delayed to a portion of a subsequent pulse of the carrier waveform which occurs after the present pulse.
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Accused Products
Abstract
A sampling synchronous envelope detector adopts a specialized sample-and-hold ("S&H") approach, basing a detected output on instantaneous values of the carrier waveform which are sampled at specially chosen instants. Non-linear distortion is avoided by timing the sampling instants to occur at or near a carrier wave peak which is subsequent to an earlier carrier wave peak which serves as a time base. Sampling instants occur only at or near positive carrier peaks (or only at or near negative peaks) in a half-wave embodiment, and sampling instants occur at or near both positive and negative carrier peaks in a full wave embodiment. Another aspect of the detector provides means, such as a phase locked loop, for ensuring that the phase of the sampling instants is maintained continuously, even in the event of carrier pinch-off or other event which distorts or minimizes the carrier waveform from which the timing instants would otherwise be determined. Still another aspect of the detector provides for low pass filtering, and group delay equalization of the filtered signal, before it is output.
117 Citations
30 Claims
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1. A synchronous sampling envelope detector, comprising:
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an input for receiving a carrier waveform which includes a series of pulses; and means, responsive to a detected maximum-magnitude value of a present pulse of the carrier waveform, for sampling an instantaneous value of the carrier waveform at a time which is delayed to a portion of a subsequent pulse of the carrier waveform which occurs after the present pulse.
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2. A synchronous sampling envelope detector for detecting an envelope of a carrier waveform which includes a series of pulses, the detector comprising:
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a) an input which receives the carrier waveform; b) a switch having; 1) a signal input which is responsive to the carrier waveform; 2) an output; and 3) a control input for determining whether the switch is "on" to connect the output to the signal input or "off" to disconnect the output from the signal input; c) a holding device, responsive to the switch'"'"'s output, for receiving a sample of the switch output'"'"'s instantaneous amplitude when the switch is on, and for holding the sample as being indicative of the carrier waveform'"'"'s instantaneous amplitude after the switch has been turned off; and d) control means, responsive to the carrier waveform, for determining a maximum-magnitude value of a present pulse of the carrier waveform and for providing a sample signal to the switch'"'"'s control input at a time delay after the determined maximum-magnitude value which occurs during part of a subsequent pulse of the carrier waveform, so as to cause the holding device to sample and hold the sample which is indicative of the instantaneous amplitude of the carrier waveform. - View Dependent Claims (3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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7. A method of detecting an envelope of a carrier waveform which includes a series of pulses, the method comprising:
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beginning a time period in response to a detected peak of a present pulse of the carrier waveform; determining an end of the time period during a subsequent pulse of the carrier waveform which occurs after the present pulse; and sampling an instantaneous amplitude of the carrier waveform at the end of the time period.
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17. A full wave synchronous sampling envelope detector for detecting an envelope of a carrier waveform which includes a series of pulses, the detector comprising:
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a) an input which receives the carrier waveform; b) a first buffer which provides a first buffered waveform in response to the carrier waveform; c) a first switch having; 1) a first signal input which is responsive to the first buffered waveform; 2) a first output; and 3) a first control input for determining whether the first switch is "on" to connect the first output to the first signal input or "off" to disconnect the first output from the first signal input; d) an inverter which provides an inverted waveform in response to the carrier waveform; e) a second switch having; 1) a second signal input which is responsive to the inverted waveform; 2) a second output; and 3) a second control input for determining whether the second switch is "on" to connect the second output to the second signal input or "off" to disconnect the second output from the second signal input; f) a holding device, responsive to the first and second switches'"'"' outputs, for receiving samples of the first and second switches'"'"' outputs'"'"' instantaneous amplitudes when the respective switches are on, and for holding successive sample values indicative of the carrier waveform'"'"'s instantaneous amplitude after the switches have been turned off; and g) control means, responsive to the carrier waveform and which determines respective peak and trough maximum-magnitude values of present pulses and which provides first and second sample signals to the respective first and second control inputs of the first and second switches at time delays after the determined peak and trough maximum-magnitude values which occurs during part of respective subsequent pulses of the carrier waveform, so as to cause the holding device to sample and hold values indicative of the instantaneous amplitude of the carrier waveform. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification