US4904950A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telemetry digital subcarrier demodulator
Assignee: Medical Data Electronics Inc
•
Filing: 1988-11-04
•
Granted: 1990-02-27
•
Expires: 2008-11-04
Abstract
Abstract A telemetry receiver for demodulating subcarrier frequencies is disclosed. The flexibility of the receiver permits it to decode signals from a wide variety of transmitters. In the preferred embodiment, a biomedical digital telemetry subcarrier demodulator employs microprocessor control of a variable bandpass filter and cycle counter. The bandpass of the filter is set by the microprocessor to pass frequencies at and around the center frequency of the desired subcarrier frequency. The counter is preset for the desired number of cycles. In operation, the desired subcarrier frequency is passed by the filter, through a signal shaper, and to the counter. Upon receiving the first cycle, the counter activates a timer, which measure the period of the predetermined number of cycles. The desired signal is the percentage deviation of the subcarrier period from the average subcarrier period. The signal to noise ratio in a digital circuit may be improved by modulating the frequency of the clock supplied to the digital circuitry coupled with passing the signal through a bandpass filter whose passband is sufficiently narrow that interference signals caused by the clock will be within the passband a portion of the time and outside the passband a portion of the time.
Inventors
- 👤 Jay E. Brown
- 👤 Gary M. Zednick
- 👤 Bibiano P. Costello
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 04:13
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/0002; A61B5/0004; A61B5/0006; Y; Y10; Y10S; Y10S128/00; Y10S128/903
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
51 words
A biomedical telemetry signal decode circuit comprising: filter means for selecting a desired passband arranged to receive said signal, a cycle counter arranged to receive the output of said filter means, a timer to receive a signal output from the cycle counter and a microprocessor for control of the decode circuit.
Claim 2
Dependent Claim
51 words
A biomedical telemetry signal decode circuit comprising: filter means for selecting a desired passband arranged to receive said signal, a cycle counter arranged to receive the output of said filter means, a timer to receive a signal output from the cycle counter and a microprocessor for control of the decode circuit.
Claim 3
Dependent Claim
20 words
The biomedical telemetry decode circuit of claim 1 wherein the filter means includes a frequency generator and switched capacitor filter.
Claim 4
Dependent Claim
21 words
The biomedical telemetry decode circuit of claim 1 which further comprises a shaper disposed between the filter and the cycle counter.
Claim 5
Dependent Claim
51 words
A variable decoder for use in telemetry comprising: a variable bandpass filter, a cycle counter coupled to the filter, a timer coupled to the cycle counter, and control circuitry to set the passband of the variable bandpass filter, to set the cycle counter and to receive the result from the timer.
Claim 6
Dependent Claim
51 words
A variable decoder for use in telemetry comprising: a variable bandpass filter, a cycle counter coupled to the filter, a timer coupled to the cycle counter, and control circuitry to set the passband of the variable bandpass filter, to set the cycle counter and to receive the result from the timer.
Claim 7
Dependent Claim
63 words
A biomedical telemetry digital subcarrier demodulator comprising: a switched capacitor filter disposed to receive the subcarrier, a frequency generator for the switched capacitor filter, a shaper to convert the output of the filter to a square wave, a cycle counter disposed to receive an output from the shaper, a timer controlled by the cycle counter, and a microprocessor for control of the demodulator.
Claim 8
Dependent Claim
63 words
A biomedical telemetry digital subcarrier demodulator comprising: a switched capacitor filter disposed to receive the subcarrier, a frequency generator for the switched capacitor filter, a shaper to convert the output of the filter to a square wave, a cycle counter disposed to receive an output from the shaper, a timer controlled by the cycle counter, and a microprocessor for control of the demodulator.
Claim 9
Independent Claim
75 words
A method of demodulating a subcarrier signal comprising the steps of: filtering the subcarrier through a variable bandpass filter, counting a predetermined number of cycles of the filtered subcarrier signal, measuring the time for the predetermined number of cycles, generating an average period for the filtered subcarrier signal, determining the demodulated subcarrier signal by determining the percentage deviation of the period of the filtered subcarrier signal from the average period for the filtered subcarrier signal.
Claim 10
Independent Claim
75 words
A method of demodulating a subcarrier signal comprising the steps of: filtering the subcarrier through a variable bandpass filter, counting a predetermined number of cycles of the filtered subcarrier signal, measuring the time for the predetermined number of cycles, generating an average period for the filtered subcarrier signal, determining the demodulated subcarrier signal by determining the percentage deviation of the period of the filtered subcarrier signal from the average period for the filtered subcarrier signal.
Claim 11
Dependent Claim
22 words
The method of demodulating a subcarrier signal of claim 6 wherein the filtered subcarrier signal is shaped prior to the counting step.
Claim 12
Independent Claim
65 words
A method for reducing interference with a signal in a digital demodulator circuit comprising: modulating the frequency of the clock signals in the digital demodulator circuit, passing the signal through a bandpass filter whose passband is sufficiently narrow that interference signals caused by the clock signals will be within the passband a portion of the time and outside the passband a portion of the time.
Claim 13
Independent Claim
65 words
A method for reducing interference with a signal in a digital demodulator circuit comprising: modulating the frequency of the clock signals in the digital demodulator circuit, passing the signal through a bandpass filter whose passband is sufficiently narrow that interference signals caused by the clock signals will be within the passband a portion of the time and outside the passband a portion of the time.
Claim 14
Dependent Claim
59 words
A biomedical telemetry digital subcarrier demodulator comprising: a microprocessor, a clock operatively connected to the microprocessor, a dither circuit associated with the clock for causing the clock frequency to modulate, a variable bandpass filter to receive an unfiltered signal, a cycle counter to receive the output of the filter and a timer to receive output from the cycle counter.
Claim 15
Dependent Claim
59 words
A biomedical telemetry digital subcarrier demodulator comprising: a microprocessor, a clock operatively connected to the microprocessor, a dither circuit associated with the clock for causing the clock frequency to modulate, a variable bandpass filter to receive an unfiltered signal, a cycle counter to receive the output of the filter and a timer to receive output from the cycle counter.
Claim 16
Dependent Claim
19 words
The biomedical telemetry digital subcarrier demodulator of claim 9 wherein the variable bandpass filter includes a switched capacitor filter.
Claim 17
Dependent Claim
14 words
The biomedical telemetry digital subcarrier demodulator of claim 9 further including a signal shaper.
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) | 1993-02-26 | 1993-08-28 | 1994-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-26 | 1997-08-28 | 1998-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-26 | 2001-08-28 | 2002-02-27 | $7700.00 | Window Closed / Lapsed |