Systems and methods for synchronous demodulation

• US 10,469,030 B2
• Filed: 05/20/2016
• Issued: 11/05/2019
• Est. Priority Date: 05/20/2015
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Nestler, Eric G., Magruder, Christopher Lynn, Harrington, John Brian
• Primary Examiner(s): Donovan, Lincoln D
• Assistant Examiner(s): Almo, Khareem E
• Application Number:
  US15/575,312
• Publication Number:
  US 20180159473A1
• Time in Patent Office: 1,264 Days
• Field of Search: None
• CPC Class Codes: H03D 1/22 Homodyne or synchrodyne circuits receiver circuits H04B1/30
• CPC Class Codes: H03D 7/12 by means of semiconductor devices having more than two electrodes H03D7/14 - H03D7/22 take precedence
• CPC Class Codes: H03H 11/04 Frequency selective two-port networks
• CPC Class Codes: H03H 11/34 Networks for connecting several sources or loads working on different frequencies or frequency bands, to a common load or source for use in multiplex transmission systems H04J1/00
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/233 using non-coherent demodulation

Abstract

Systems and methods for synchronous demodulation using passive sampled analog filtering are disclosed. A system for synchronous demodulation includes an input channel for accepting an input signal, a first passive sampled analog filter for filtering the input signal, a mixer for mixing the filtered input signal and outputting a mixed signal, a second passive sampled analog filter for filtering the mixed signal, and an output channel for outputting the filtered mixed signal.

Claims

1. A system for synchronous demodulation using passive sampled analog filtering, comprising:

an input channel for receiving an input signal;

a first passive sampled analog filter for sampling and filtering the input signal;

a mixer for mixing the filtered input signal from the first filter and outputting a mixed signal;

a second passive sampled analog filter for filtering the mixed signal; and

an output channel for outputting the filtered mixed signal.

2. The system of claim 1, wherein the first filter and the mixer are combined in a single passive circuit block.

3. The system of claim 1, further comprising a first active amplifier between the first filter and the mixer for amplifying the filtered signal.

4. The system of claim 3, further comprising a second active amplifier between the mixer and the second filter for amplifying the mixed signal.

5. The system of claim 1, wherein the first passive sampled analog filter is a programmable filter.

6. The system of claim 1, wherein the first passive sampled analog filter is one of a low-pass filter, a band-pass filter, a high-pass filter, and a filter with an arbitrary filter shape.

7. The system of claim 1, wherein the first passive analog filter is one of a FIR filter and an IIR filter.

8. The system of claim 1, wherein the second passive sampled analog filter is a low pass filter.

9. The system of claim 1, further comprising a clock generator for generating an excitation signal, and wherein the excitation signal is modified by a target element, and the modified excitation signal is the input signal.

10. The system of claim 9, wherein the target element is a body part and wherein the system measures bioimpedance of the body part.

11. The system of claim 9, wherein the clock generator generates a reference signal, and wherein the reference signal is mixed with the filtered input signal at the mixer.

12. The system of claim 9, wherein the target element is one of a sensor and a transformer.

13. A method for synchronous demodulation using passive sampled analog filtering, comprising:

presenting an excitation signal to a target element;

receiving, at an input, a modified signal from the target element;

sampling and filtering, using a passive sampled analog filter, the modified signal to remove noise;

mixing the filtered signal with a reference signal from a clock generator;

filtering, using a second passive sampled analog filter, the mixed signal; and

outputting, from the second passive sampled analog filter, a signal representing characteristics of the target element.

14. The method of claim 13, wherein presenting the excitation signal includes presenting a current to the target element, and wherein receiving a modified signal includes receiving a voltage.

15. The method of claim 13, wherein presenting the excitation signal includes presenting a voltage to the target element, and wherein receiving a modified signal includes receiving a current.

16. The method of claim 13, wherein outputting the signal includes outputting an I-component of the signal and outputting a Q-component of the signal.

17. A synchronous demodulation system using passive sampled analog filtering, comprising:

a clock generator for generating an excitation signal;

an input channel for receiving a modified excitation signal;

means for passively sampling, filtering and mixing the modified excitation signal to synchronously demodulate the modified excitation signal and generate a demodulated output signal.

18. The system of claim 17, wherein the means for passively filtering the modified excitation signal includes a passive sampled analog filter.

19. The system of claim 18, wherein the passive sampled analog filter is one of a low-pass filter, a band-pass filter, a high-pass filter, and a filter with an arbitrary filter shape.

20. The system of claim 17, wherein the means for mixing the modified excitation signal include a mixer, and wherein the mixer is one of a two-level mixer, a three-level mixer, and a mixer with greater than three levels.