Methods and Systems for Interference Rejection for Low Signals

• US 20120171978A1
• Filed: 01/26/2012
• Published: 07/05/2012
• Est. Priority Date: 12/29/2010
• Status: Active Grant

• Current Assignee: Secureall Corporation
• Original Assignee: Secureall Corporation
• Inventors: Sharma, Arun Kumar, Wurm, Michael
• Granted Patent: US 8,606,215 B2
• Time in Patent Office: Days
• US Class Current: 455/230
• CPC Class Codes: H03H 11/1208 comprising an electromechanical resonator
• CPC Class Codes: H03H 2210/015 Quality factor or bandwidth
• CPC Class Codes: H03H 2210/028 Resistor
• CPC Class Codes: H03H 2210/036 Stepwise
• CPC Class Codes: H03H 7/0161 Bandpass filters H03H7/12 takes precedence
• CPC Class Codes: H03H 7/06 including resistors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence
• CPC Class Codes: H03H 7/175 Series LC in series path H03H7/1783 takes precedence
• CPC Class Codes: H03H 7/1775 Parallel LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H04B 1/1638 Special circuits to enhance selectivity of receivers not otherwise provided for resonant circuits H03H
• CPC Class Codes: H04B 1/24 the receiver comprising at least one semiconductor device having three or more electrodes

Abstract

A radio device and a method to operate a non-heterodyne receiver are provided. The radio device is configured to receive a signal waveform and to provide a wake-up signal to a second communication circuit when the signal waveform is a valid communication request; wherein the second communication circuit switches from a power saving state to an operating state upon receiving the wake-up signal from the non-heterodyne receiver. The non-heterodyne receiver further including an Electromagnetic interference (EMI) rejection circuit, including a narrow band filter and a broadband filter to reject an EMI signal. A filter circuit for a narrow passband circuit is also provided. The filter including a buffer circuit; a crystal oscillator coupled to the output of the buffer circuit; and an inverting amplifier coupled in parallel to the crystal oscillator.

Claims

1. A radio device, comprising:

a non-heterodyne receiver, configured to receive a signal waveform and to provide a wake-up signal to a second communication circuit when the signal waveform is a valid communication request;

wherein

the second communication circuit switches from a power saving state to an operating state upon receiving the wake-up signal from the non-heterodyne receiver;

the non-heterodyne receiver further comprising an Electromagnetic interference (EMI) rejection circuit including a narrow band filter and a broadband filter to reject an EMI signal.

2. The radio device of claim 1 wherein the signal waveform is a sub-carrier modulation signal.

3. The radio device of claim 1 wherein the signal waveform is a base-band modulation signal.

4. The radio device of claim 1 wherein the EMI rejection circuit includes a switch to alternate a signal measurement with the narrow band filter and a signal measurement with the broadband filter.

5. The radio device of claim 1 wherein the EMI rejection circuit performs a measurement with the narrow band filter concurrently with a measurement with the broadband filter.

6. The radio device of claim 1 wherein the EMI rejection circuit is configured to measure a first power of a signal with the narrow band filter and a second power of a signal with the broad band filter, wherein the first power and the second power are approximately the same when the signal is the EMI signal.

7. The radio device of claim 1 wherein the EMI rejection circuit is configured to measure a first power of a signal with the narrow band filter and a second power of a signal with the broad band filter, wherein the first power is greater than the second power when the signal is from a valid communication partner.

8. The radio device of claim 1 wherein the EMI rejection circuit is configured to measure a first power of a signal with the narrow band filter and a second power of a signal with the broadband filter, wherein the first power is approximately equal to the second power when the signal is from a valid communication partner.

9. The radio device of claim 1 wherein the EMI rejection circuit is configured to measure a first power of a signal with the narrow band filter and a second power of a signal with the broad band filter, wherein the second power is greater than the first power when the signal is the EMI signal.

10. The radio device of claim 1 wherein the EMI circuit includes a trans-conductance amplifier stage coupled to a narrow band filter and a broad band filter.

11. The radio device of claim 10 wherein the trans-conductance amplifier is a transistor and the narrow band filter is an LCR circuit.

12. The radio device of claim 1 wherein the EMI circuit includes a clipper circuit to constrain a dynamic range of the circuit, reducing signal clipping artifacts.

13. The radio device of claim 1 wherein the EMI circuit is configured to measure a first power of a signal with the narrow band filter and a second power of a signal with the broad band filter;

and

the EMI circuit includes a comparator circuit to compare the first power and the second power.

14. A filter circuit for a narrow passband circuit comprising:

a buffer circuit;

a crystal oscillator coupled to the output of the buffer circuit; and

an inverting amplifier coupled in parallel to the crystal oscillator.

15. The filter circuit of claim 14 wherein the crystal oscillator includes a Piezo-electric crystal.

16. The filter circuit of claim 14 wherein the inverting amplifier is coupled in series to a capacitor.

17. A method to operate a radio device, comprising:

turning ‘

on’

a first receiver for a period of time;

receiving a signal waveform in the first receiver;

detecting a first signal level from the signal waveform using a narrow band filter;

detecting a second signal level from the signal waveform using a broad band filter;

comparing the first signal level and the second signal level to determine if the signal waveform is a valid communication request or an electromagnetic interference (EMI);

when the signal waveform is a valid communication request, turning ‘

on’

a second circuit;

when the signal waveform is EMI, maintaining the second circuit in a sleep mode;

turning ‘

off’

the first receiver after the period of time lapses.

18. The method of claim 17 wherein comparing the first signal level and the second signal level includes determining that the signal is a valid communication request when the first signal level is greater than the second signal level.

19. The method of claim 17 wherein the signal waveform is a sub-carrier modulated signal.

20. The method of claim 17 wherein the signal waveform is a base-band modulated signal.