System and method for an energy efficient RF transceiver

• US 20080304432A1
• Filed: 05/19/2008
• Published: 12/11/2008
• Est. Priority Date: 05/18/2007
• Status: Active Grant

• Current Assignee: Argon St
• Original Assignee: Argon St
• Inventors: Ryu, Bong K., Ma, Liangping, Zhu, Hua, Lee, Harry, Schader, Fred E.
• Granted Patent: US 8,483,649 B2
• Time in Patent Office: Days
• US Class Current: 370/311
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 52/029 reducing the clock frequency of the controller
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An energy efficient radio having a clocking system utilizing two clocks with very different precision and power characteristics. In another aspect, the time that a radio spends on listening/receiving is optimized so that energy is not wasted when there is no need to keep receiving. In another aspect, to further improve the energy efficiency, two receive portions with drastic difference in power consumption, instead of a single receive portion as is used in a typical wireless receiver, and are used to process different parts of a received packet.

Claims

1. A method of reducing the power consumption of a wireless communications device, the device having a sleep mode and a wake-up mode, comprising the steps of:

(a) placing a first receiver portion of the device in a wake-up mode;

(b) receiving a signal having a header and a payload;

(c) decoding the header to determine an identity of the intended receiver in the first receiver portion;

(d) placing the first receiver portion in a sleep mode if the device is not the intended receiver; and

(e) waking up a second receiver portion and decoding the payload in the second receiver portion if the device is the intended receiver.

2. The method of claim 1 wherein the step of decoding the header comprises the steps of:

(i) converting the header to a digital signal in a first receiver portion using a one bit modem;

(ii) decoding the digital signal using Direct Sequence Spread Spectrum; and

(iii) comparing the decoded signal with a set of known digital strings associated with available receivers to determine if the device is the intended receiver.

3. The method of claim 2 wherein the step of comparing comprises the steps of:

(i) determining the Hamming distance between the encoded signal and each of the known digital strings;

(ii) selecting the known digital string having the shortest Hamming distance to the encoded signal; and

(iv) identifying the receiver associated with the selected digital string.

4. The method of claim 1, wherein the received signal includes a gap inserted between the header and the payload, and the step of decoding the header occurs during a period of time during which the gap exists.

5. The method of claim 1 wherein the step of decoding the payload includes the steps of

(i) placing a second receiver portion in a wake-up mode;

and

(ii) converting the payload to a digital signal in the second receiver portion using an analog to digital converter.

6. The method of claim 5 further including the steps of:

(i) using a first clock to determine when to place the first receiver portion in a wake-up mode; and

(ii) using a second clock, having a higher precision than the first clock, when the first or second receiver portion is in wake-up mode.

7. The method of claim 6 further comprising the step of turning off the second clock when the first and second receiver portions are in a sleep mode.

8. The method of claim 6 further comprising the step of turning off the first clock when the first and second receiver are in wake-up mode.

9. The method of claim 4 wherein a known character string is transmitted during the period of time in which the gap exists.

10. The method of claim 2 wherein the one bit modem is an operational amplifier.

11. The method of claim 1, wherein the step of placing the first receiver portion in wake-up mode includes the steps of:

(i) starting a second clock;

(ii) tuning the receiver;

(iii) listening for a pre-amble and header of a transmitted signal.

12. An energy efficient wireless device comprising:

a first receiver portion having an operational amplifier feeding a Direct Sequence Spread Spectrum decoder and an identity decoder;

a second receiver portion having an analog to digital converter feeding a signal processor;

a first clock for providing timing to the first receiver portion; and

a second clock having a precision greater than the first clock;

for providing timing to the second receiver portion; and

wherein the first receiver portion processes a portion of a received signal and passes the received signal to the second receiver portion as a function of the processing by the first receiver portion.

13. The system of claim 12 wherein the first receiver processes the header of a received signal to identify an intended receiver for the received signal.

14. The system of claim 13 wherein the first receiver includes a computer readable medium storing a software program which when executed controls the application of power to be applied to the second receiver portion.