# US 2018/0323955 A1 · System and method of detecting end of synchronization header of modulated signals

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- Number: US 2018/0323955 A1
- Document ID: US20180323955A1
- Status: Published application
- Kind: A1
- Application number: 16/031,944
- Filed: 2018-07-10
- Published: 2018-11-08
- Earliest claimed: 2017-01-25
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Farrokh Etezadi; Linbo Li; Chun Kin Au Yeung; Xiaoqiang Ma
- Web page: https://patentgrep.com/patent/US20180323955A1

## CPC

- H04L 7/0087: {Preprocessing of received signal for synchronisation, e.g. by code conversion, pulse generation or edge detection}
- H04L 7/042: {Detectors therefor, e.g. correlators, state machines (digital correlators in general G06F17/15)}
- H04L 25/03019: {adaptive, i.e. capable of adjustment during data reception}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A receiver of a modulated signal includes a synchronization detector configured to receive a signal indicative of the modulated signal and to detect an end of the synchronization header in the signal. The synchronization detector is configured to generate a differential signal based on the signal, perform cross-correlation of the differential signal with a reference differential signal to generate a cross-correlation output, compare a first sample of the cross-correlation output at a sample index associated with a hypothesized start frame delimiter (SFD) peak index with a second sample of the cross-correlation output at a sample index associated with a hypothesized preamble peak index, and detect an end of the synchronization header in response to a comparison result in which a magnitude of the first sample of the cross-correlation output is greater than a magnitude of the second sample of the cross-correlation output.

## Claims

### Claim 1

A receiver of a modulated signal, the receiver comprising:
a synchronization detector configured to receive a signal indicative of the modulated signal, the modulated signal including a synchronization header and a data payload, and to detect an end of the synchronization header in the signal, wherein the synchronization detector is configured to:
generate a differential signal based on the signal,
perform cross-correlation of the differential signal with a reference differential signal to generate a cross-correlation output,
compare a first sample of the cross-correlation output at a sample index associated with a hypothesized start frame delimiter (SFD) peak index with a second sample of the cross-correlation output at a sample index associated with a hypothesized preamble peak index, and
detect an end of the synchronization header in response to a comparison result in which a magnitude of the first sample of the cross-correlation output is greater than a magnitude of the second sample of the cross-correlation output.

### Claim 2 (depends on 1)

The receiver of claim 1, wherein the first sample of the cross-correlation output corresponds to the sample index at a first expected time at which a correlation peak is expected to be generated by the start frame delimiter (SFD) of the signal; and the second sample of the cross-correlation output corresponds to the sample index at a second expected time at which a correlation peak is expected to be generated by the preamble.

### Claim 3 (depends on 1)

The receiver of claim 1, wherein the synchronization detector further comprises a delay-multiplier configured to generate the differential signal according to the expression:
zn=rnr*n−D×OSR
wherein r represents the signal, r* represents the complex conjugate of r, z represents the differential signal value, n represents a sample time index, D represents a delay value, and OSR represents an oversampling ratio.

### Claim 4 (depends on 3)

The receiver of claim 3, wherein the synchronization detector further comprises a matched filter configured to perform cross-correlation of the differential signal with the reference differential signal according to the expression:
C
n
=
∑
i
=
0
L
-
1

(
r
n
-
i

r
n
-
i
-
D
×
OSR
*
)

d
L
-
i
-
1
where C represents the cross-correlation output, d represents the reference differential signal, L represents a length of the reference differential signal, × denotes the multiplication symbol, and i represents a sample time index.

### Claim 5 (depends on 4)

The receiver of claim 4, wherein the reference differential signal d is calculated according to the expression:
dk=pkp*k+D×OsR for 0≤k≤L−1
where p represents a preamble sequence of the synchronization header, p* represents the complex conjugate of p, and k represents a sample time index.

### Claim 6 (depends on 4)

The receiver of claim 4, wherein the synchronization detector further comprises a signal normalizer configured to normalize the cross-correlation output according to the expression:
M
n
=
C
n
L
×
P
n
where P represents an estimated power of the signal r, M is the normalized value of C, and × denotes the multiplication symbol.

### Claim 7 (depends on 5)

The receiver of claim 5, wherein the preamble sequence corresponds to the preamble sequence of a ZigBee formatted data packet.

### Claim 8 (depends on 2)

The receiver of claim 2, wherein the first expected time is at 28×OSR samples after a last preamble peak, and the second expected time is at 32×OSR samples after the last preamble peak, where OSR represents an oversampling ratio.

### Claim 9 (depends on 1)

The receiver of claim 1, further comprising:
a signal mixer configured to perform baseband down-conversion of the modulated signal according to a mixer frequency to generate the signal;
a data demodulator configured to demodulate the data payload in response to detection of the end of the synchronization header; and
a frequency offset estimator configured to:
calculate a frequency offset based on the stored sample values, and
compensate a frequency offset of the signal by causing the signal mixer to increase or decrease the mixer frequency according to the calculated frequency offset.

### Claim 10

A method of synchronizing a receiver of a modulated signal, the method comprising:
receiving a signal indicative of the modulated signal, the modulated signal including a synchronization header and a data payload;
generating a differential signal based on the signal;
performing cross-correlation of the differential signal with a reference differential signal to generate a cross-correlation output;
comparing a first sample of the cross-correlation output at a sample index associated with a hypothesized start frame delimiter (SFD) peak index with a second sample of the cross-correlation output at a sample index associated with a hypothesized preamble peak index; and
detecting an end of the synchronization header in response to a comparison result in which a magnitude of the first sample of the cross-correlation output is greater than a magnitude of the second sample of the cross-correlation output.

### Claim 11 (depends on 10)

The method of claim 10, wherein the first sample of the cross-correlation output corresponds to the sample index at a first expected time at which a correlation peak is expected to be generated by the start frame delimiter (SFD) of the signal; and the second sample of the cross-correlation output corresponds to the sample index at a second expected time at which a correlation peak is expected to be generated by the preamble.

### Claim 12 (depends on 10)

The method of claim 10, wherein generating a differential signal based on the signal comprises generating the differential signal according to the expression:
zn=rnr*n−D×OSR
wherein r represents the signal, r* represents the complex conjugate of r, z represents the differential signal value, n represents a sample time index, D represents a delay value, and OSR represents an oversampling ratio.

### Claim 13 (depends on 12)

The method of claim 12, wherein performing cross-correlation of the differential signal with the reference differential signal to generate the cross-correlation output comprises performing cross-correlation of the differential signal with the reference differential signal according to the expression:
C
n
=
∑
i
=
0
L
-
1

(
r
n
-
i

r
n
-
i
-
D
×
OSR
*
)

d
L
-
i
-
1
where C represents the cross-correlation output, d represents the reference differential signal, L represents a length of the reference differential signal, × denotes the multiplication symbol and i represents a sample time index.

### Claim 14 (depends on 13)

The method of claim 13, further comprising:
calculating the reference differential signal d according to the expression:
dk=pkp*k+D×OsR for 0≤k≤L−1
where p represents a preamble sequence of the synchronization header, p* represents the complex conjugate of p, and k represents a sample time index.

### Claim 15 (depends on 13)

The method of claim 13, further comprising:
subsequent to performing cross-correlation, normalizing the cross-correlation output according to the expression:
M
n
=
C
n
L
×
P
n
where P represents an estimated power of the signal r, M is the normalized value of C, and × denotes the multiplication symbol.

### Claim 16 (depends on 14)

The method of claim 14, wherein the preamble sequence corresponds to the preamble sequence of a ZigBee formatted data packet.

### Claim 17 (depends on 11)

The method of claim 11, wherein the first expected time is at 28×OSR samples after a last preamble peak, and the second expected time is at 32×OSR samples after the last preamble peak, where OSR represents an oversampling ratio.

### Claim 18 (depends on 10)

The method of claim 10, further comprising:
performing baseband down-conversion, by a signal mixer, of the modulated signal according to a mixer frequency to generate the signal;
operating a data demodulator in response to detection of the end of the synchronization header to demodulate the data payload;
calculating a frequency offset based on the stored sample values; and
compensating a frequency offset of the signal by causing the signal mixer to increase or decrease the mixer frequency according to the calculated frequency offset.

### Claim 19 (depends on 10)

The method of claim 10, wherein performing cross-correlation of the differential signal with a reference differential signal to generate a cross-correlation output comprises performing cross-correlation of the differential signal with a reference differential signal using a matched filter to generate the cross-correlation output.

### Claim 20 (depends on 19)

The method of claim 19, wherein performing cross-correlation of the differential signal using the matched filter comprises:
performing cross-correlation of the differential signal using the matched filter to generate the first sample of the cross-correlation output and the second sample of the cross-correlation output.