Receiver with reduced wake-up time
An auxiliary reduced power analog-to-digital converter (ADC) is provided for use during sleep periods of a receiver. The auxiliary ADC has a reduced dynamic range but sufficient accuracy to allow demodulation of signaling information contained in an input signal and to update control parameters used for synchronization and channel estimation. As such, a main higher power, higher dynamic range ADC can be turned off during sleep periods, reducing receiver power consumption. The main ADC is turned on at the end of a sleep period, and the receiver can be ready for receiving data immediately using the main ADC because the control parameters are maintained up to date during the sleep period using the auxiliary ADC.
1. A receiver, comprising:
a first analog-to-digital converter (ADC) configured to receive an input signal and to produce a first ADC signal;
a second ADC configured to receive the input signal and to produce a second ADC signal;
a receiver processing chain;
a controller configured to receive sleep mode information of the receiver and to generate a control signal in response to the sleep mode information; and
a multiplexer configured to receive the first and second ADC signals and to output the first ADC signal or the second ADC signal as an output signal to the receiver processing chain in response to the control signal.
2. The receiver of claim 1 , wherein the second ADC has a lower dynamic range than the first ADC.
3. The receiver of claim 1 , wherein the first ADC signal includes a larger number of bits than the second ADC signal.
4. The receiver of claim 1 , wherein the receiver processing chain comprises:
a time domain processing module configured to receive the output signal of the multiplexer and to apply at least one of a time offset correction, a carrier frequency offset correction, and automatic gain control (AGC) to the output signal to produce a modified output signal;
a Fast Fourier Transform (FFT) module configured to receive the modified output signal and to produce a discrete Fourier transform of the modified output signal; and
a frequency domain processing module configured to receive the discrete Fourier transform and to estimate at least one of a time offset between the receiver and a transmitter of the input signal, a carrier frequency offset between the receiver and the transmitter, a channel estimate of a channel between the receiver and the transmitter, and a trigger position of the FFT module.
5. The receiver of claim 1 , wherein the multiplexer is configured to output the first ADC signal as the output signal to the receiver processing chain when the sleep mode information includes a sleep mode end instruction, and to output the second ADC signal as the output signal to the receiver processing chain when the sleep mode information includes a sleep mode begin instruction.
6. The receiver of claim 5 , wherein the second ADC signal includes a representation of signaling information only.
7. The receiver of claim 5 , wherein the controller is further configured to turn on the first ADC and turn off the second ADC when the sleep mode information includes the sleep mode end instruction, and to turn on the second ADC and turn off the first ADC when the sleep mode information includes the sleep mode begin instruction.
8. A receiver, comprising:
a first receiver processing chain, including a first analog-to-digital converter (ADC); and
a second receiver processing chain, including a second ADC; and
a memory that stores one or more control parameters used by the first receiver processing chain and the second receiver processing chain to maintain synchronization during processing of an input signal of the receiver,
wherein the first receiver processing chain is configured to process the input signal of the receiver when the receiver is in a normal power mode, and wherein the second receiver processing chain is configured to process the input signal of the receiver when the receiver is in a sleep mode, and
wherein the second receiver processing chain is configured to update the one or more control parameters based on processing of the input signal during the sleep mode of receiver.
9. The receiver of claim 8 , wherein the second ADC has a lower dynamic range than the first ADC.
10. The receiver of claim 8 , wherein a first output signal produced by the first ADC in processing the input signal includes a larger number of bits than a second output signal produced by the second ADC in processing the input signal.
11. The receiver of claim 8 , wherein the first receiver processing chain is configured to process the input signal to retrieve data embedded in the input signal.
12. The receiver of claim 8 , wherein the second receiver processing chain is configured to process the input signal to retrieve only signaling information from the input signal.
13. The receiver of claim 8 , wherein the first receiver processing chain is configured to retrieve the updated one or more control parameters from the memory upon transition from the sleep mode to the normal power mode.
14. The receiver of claim 8 , wherein the control parameters include one or more of a time offset estimate, a carrier frequency offset estimate, or a channel profile estimate.
15. A method of operating a receiver, comprising:
determining an operating state of a receiver, wherein determining the operating state of the receiver comprises identifying a sleep mode start trigger or a sleep mode end trigger; and
coupling an input signal of the receiver to a main processing chain or to an auxiliary processing chain based on the operating state of the receiver,
wherein the main processing chain includes a first analog-to-digital converter (ADC) and the auxiliary processing chain includes a second ADC, and wherein the second ADC has a lower dynamic range than the first ADC.
16. The method of claim 15 , wherein the sleep mode start trigger is identified, the method further comprising:
determining a sleep mode start time;
turning off the main processing chain and turning on the auxiliary processing chain at the sleep mode start time;
coupling the input signal to the auxiliary processing chain; and
processing the input signal using the auxiliary processing chain beginning at the sleep mode start time to retrieve signaling information from the input signal.
17. The method of claim 16 , wherein the signaling information is contained in low modulation order symbols of the input signal.
18. The method of claim 15 , wherein the sleep mode end trigger is identified, the method further comprising:
determining a sleep mode end time;
turning off the auxiliary processing chain and turning on the main processing chain at the sleep mode end time;
coupling the input signal to the main processing chain; and
processing the input signal using the main processing chain beginning at the sleep mode end time to retrieve data embedded in the input signal.
19. A receiver, comprising:
an analog-to-digital converter (ADC) configured to receive an input signal and to produce a first ADC signal;
a refinement circuit, coupled to the ADC, configured to receive the first ADC signal and to generate a second ADC signal, wherein the second ADC signal includes a larger number of bits than the first ADC signal;
a receiver processing chain; and
a multiplexer configured to receive the first and second ADC signals and to output the first ADC signal or the second ADC signal as an output signal to the receiver processing chain in response to a control signal.
20. The receiver of claim 19 , further comprising:
a controller configured to receive sleep mode information of the receiver and to generate the control signal in response to the sleep mode information.
21. The receiver of claim 20 , wherein the multiplexer is configured to output the first ADC signal as the output signal to the receiver processing chain when the sleep mode information includes a sleep mode end instruction, and to output the second ADC signal as the output signal to the receiver processing chain when the sleep mode information includes a sleep mode begin instruction.