Preamble detection for wireless power ask communication
According to an embodiment, a preamble detection circuit includes a slicer that normalizes a demodulated Amplitude Shift Keying (ASK) signal to generate a binary waveform, a correlator that performs correlation with a reference preamble sequence, and decision logic that determines if a valid preamble is detected. The circuit enables a primary demodulation chain to remain in a low-power state until a valid preamble is identified, providing efficient preamble detection for wireless power transfer systems while minimizing power consumption during communication inactivity. The circuit's configurable parameters allow optimization for different operating conditions and communication protocols.
1 . A method for detecting a preamble in an Amplitude Shift Keying (ASK) signal, the method comprising:
receiving a demodulated ASK signal at a preamble detection circuit;
detecting a valid preamble or portions of a valid preamble sequence using the preamble detection circuit, the detecting comprising:
normalizing the demodulated ASK signal to generate a normalized binary waveform with a configurable amplitude,
performing a correlation between the normalized binary waveform and a reference preamble sequence to generate a correlated signal, wherein the correlation is performed for a configurable number of bits,
estimating a parameter associated with the correlated signal, and
determining whether the valid preamble has been detected based on the estimated parameter; and
generating a trigger signal based on the detection of the valid preamble or portions of the valid preamble sequence.
2 . The method of claim 1 , wherein the normalizing the demodulated ASK signal comprises:
comparing the demodulated ASK signal to configurable threshold levels; and
outputting the normalized binary waveform with configurable amplitude levels based on the comparison.
3 . The method of claim 1 , wherein the performing the correlation comprises performing a finite impulse response (FIR) matched filter on a sequence of preamble bits.
4 . The method of claim 3 , wherein the reference preamble sequence comprises a configurable number of samples per preamble bit.
5 . The method of claim 1 , wherein the determining whether the valid preamble or portions of the valid preamble sequence has been detected comprises analyzing an output of the correlation, the analyzing comprising:
counting peaks in the output of the correlation that exceed a threshold value, and
determining that the valid preamble has been detected in response to a number of counted peaks reaching a predetermined count.
6 . The method of claim 1 , wherein the determining whether the valid preamble or portions of the valid preamble sequence has been detected comprises:
comparing the estimated parameter to a threshold value; and
determining whether the estimated parameter exceeds the threshold value.
7 . The method of claim 6 , further comprising generating the trigger signal in response to the estimated parameter exceeding the threshold value.
8 . A circuit for detecting a preamble in an Amplitude Shift Keying (ASK) signal, the circuit comprising:
a slicer configured to normalize a demodulated ASK signal and generate a normalized binary waveform with a configurable amplitude;
a correlator circuit coupled to the slicer and configured to perform a correlation between the normalized binary waveform and a reference preamble sequence to generate a correlated signal, wherein the correlation is performed for a configurable number of bits;
an estimator circuit coupled to the correlator circuit and configured to estimate a parameter associated with the correlated signal; and
a decision logic circuit coupled to the estimator circuit and configured to determine whether a valid preamble or portions of a valid preamble sequence has been detected based on the estimated parameter and generate a trigger signal in response to determining the valid preamble or portions of the valid preamble sequence.
9 . The circuit of claim 8 , wherein the slicer comprises a comparator configured to compare the demodulated ASK signal to configurable threshold levels and output the normalized binary waveform with configurable amplitude levels based on the comparison.
10 . The circuit of claim 8 , wherein the correlator circuit comprises a finite impulse response filter (FIR) matched to a sequence of preamble bits.
11 . The circuit of claim 10 , wherein the reference preamble sequence comprises a configurable number of samples per preamble bit.
12 . The circuit of claim 8 , wherein the estimator circuit includes a bypass mode, wherein, in response to the estimator circuit being in the bypass mode, the decision logic circuit is configured to analyze an output of the correlator circuit, the analyzing comprising:
counting samples in the output of the correlator circuit exceeding a threshold value, and
determining that the valid preamble has been detected in response to a number of counted over-threshold samples reaching a predetermined count.
13 . The circuit of claim 8 , wherein the decision logic circuit comprises:
a first comparator configured to compare the estimated parameter to a threshold value; and
a second comparator configured to determine whether the estimated parameter exceeds the threshold value for a predetermined number of consecutive occurrences.
14 . The circuit of claim 13 , wherein the decision logic circuit is further configured to generate the trigger signal in response to the estimated parameter exceeding the threshold value.
15 . A system for Amplitude Shift Keying (ASK) demodulation, the system comprising:
a primary demodulation chain; and
a preamble detection circuit coupled to the primary demodulation chain, the preamble detection circuit comprising:
a slicer configured to normalize a demodulated ASK signal and generate a normalized binary waveform with a configurable amplitude,
a correlator circuit coupled to the slicer and configured to perform a correlation between the normalized binary waveform and a reference preamble sequence to generate a correlated signal, wherein the correlation is performed for a configurable number of bits,
an estimator circuit coupled to the correlator circuit and configured to estimate a parameter associated with the correlated signal, and
a decision logic circuit coupled to the estimator circuit and configured to determine whether a valid preamble or portions of a valid preamble sequence have been detected based on the estimated parameter,
wherein the primary demodulation chain is triggered in response to detecting the valid preamble.
16 . The system of claim 15 , wherein the primary demodulation chain comprises a demodulation sub-portion and a decoding sub-portion, the demodulation sub-portion configured to operate in a low-power mode while the decoding sub-portion remains inactive until the valid preamble is detected.
17 . The system of claim 15 , further comprising an auxiliary demodulation circuit configured to:
consume less power than the primary demodulation chain when performing demodulation;
generate a signal for the preamble detection circuit; and
maintain operation while the primary demodulation chain remains inactive.
18 . The system of claim 15 , wherein the preamble detection circuit is configured to detect a preamble compliant with the ASK communication of Qi wireless power transfer standard.
19 . The system of claim 15 , further comprising a microcontroller coupled to the preamble detection circuit and the primary demodulation chain, wherein the microcontroller is configured to receive a trigger signal from the preamble detection circuit to trigger the primary demodulation chain.
20 . The system of claim 15 , wherein the primary demodulation chain and an auxiliary demodulation circuit are configured to share hardware components in a low-power mode, wherein the shared hardware components comprise components necessary for generating a signal for the preamble detection circuit.