# US 2019/0245571 A1 · Optimized demodulation of rds signals in digital radio

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- Number: US 2019/0245571 A1
- Document ID: US20190245571A1
- Status: Published application
- Kind: A1
- Application number: 16/340,162
- Filed: 2017-11-23
- Published: 2019-08-08
- Earliest claimed: 2016-11-24
- Assignees: Continental Automotive France; Continental Automotive GmbH
- Applicants: Continental Automotive France; Continental Automotive GmbH
- Inventors: Chao Lin
- Web page: https://patentgrep.com/patent/US20190245571A1

## CPC

- H04B 1/3822: specially adapted for use in vehicles (H04B1/3827 takes precedence)
- H04B 1/0042: {Digital filtering (H04B1/0035 takes precedence; digital filters per se H03H17/00)}
- H04B 1/38: Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B 1/712: Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
- H04W 4/48: for in-vehicle communication
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A method for correcting RDS demodulation in a vehicle radio system including a digital core with an RDS demodulation block, a numerically controlled oscillator, a digital mixer that mixes the input signals with the output of the numerically controlled oscillator, a low-pass filter for recovering baseband RDS signals including a sequence of symbols, and a phase-estimating block configured to estimate a phase deviation of the baseband signal. The method including a first correction acting, depending on the estimation of the phase deviation of the baseband signal, on a phase equalizer, downstream of the low-pass filter, in order to cancel out the phase deviation, and optionally a second correction forming a feedback loop and acting on the numerically controlled oscillator depending on the drift in the phase deviations of the baseband signal.

## Claims

### Claim 1

A method for correcting RDS demodulation in a vehicle radio system comprising:
a digital core with an RDS demodulation block,
an input for digital signals,
a numerically controlled oscillator that delivers a complex value,
a complex digital mixer that mixes the input signals with an output of the numerically controlled oscillator,
low-pass filter for recovering baseband demodulated RDS signals comprising a sequence of complex symbols,
a phase-estimating block configured to estimate a phase deviation of the baseband signal,
a decoding block to which the filtered signals are transmitted,
the method comprising a first correction acting, depending on the estimation of the phase deviation of the baseband signal, on a phase equalizer, downstream of the passband filter, in order to cancel out the phase deviation.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein the phase-estimating block performs a calculation of phase deviation on the N last received symbols, N being an integer comprised between 4 and 16.

### Claim 3 (depends on 2)

The method as claimed in claim 2, wherein the calculation of phase deviation between the frequency of the numerically controlled oscillator 2 and the frequency of the emitter is estimated using the following formula:
θ
^
=
1
2

arg

(
∑
k
=
0
N
-
1

(
S

(
k
)
)
2
)
=
1
2

arctan

(
∑
k
=
0
N
-
1

(
S

(
k
)
)
2
)
.

### Claim 4 (depends on 2)

The method as claimed in claim 2, wherein a conjugate e−j{circumflex over (θ)} of the estimated phase deviation is calculated, which is injected into the phase equalizer, where it cancels out the phase deviation of the symbol transmitted to the decoding block, the conjugate e−j{circumflex over (θ)} of the phase deviation estimated being calculated using the following formula:
e
-
j


θ
^
=
conj

(
∑
k
=
0
N
-
1

(
S

(
k
)
)
2

∑
k
=
0
N
-
1

(
(
Sk
)
)
2

)
.

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein the method comprises a second correction forming a feedback loop and acting on the numerically controlled oscillator depending on the drift in the phase deviations DrvΦ of the baseband signal, in order to reset the frequency of the numerically controlled oscillator to as close as possible to the received RDS subcarrier.

### Claim 6 (depends on 5)

The method as claimed in claim 5, wherein the frequency of the numerically controlled oscillator is corrected only if the drift in the phase deviations DrvΦ is higher than a preset threshold.

### Claim 7 (depends on 5)

The method as claimed in claim 5, wherein the drift in the phase deviations DrvΦ is calculated from an average drift over M consecutive phase deviations, M being an integer.

### Claim 8 (depends on 5)

The method as claimed in claim 5, wherein the second correction forming a feedback loop is undersampled with respect to the first correction.

### Claim 9

A vehicle radio system comprising:
a digital core with an RDS demodulation block,
an input for digital signals,
a numerically controlled oscillator,
a digital mixer that mixes the input signals with anoutput of the numerically controlled oscillator,
a low-pass filter for recovering baseband RDS signals comprising a sequence of complex symbols,
a phase-estimating block, and
a first correcting loop acting, depending on a measurement of the phase deviation of the baseband signal, on a phase equalizer, downstream of the passband filter.

### Claim 10 (depends on 9)

The vehicle radio system as claimed in claim 9, furthermore comprising a second correction forming a feedback loop and acting on the numerically controlled oscillator depending on the drift in the phase deviations DrvΦ of the baseband signal, in order to reset the frequency of the numerically controlled oscillator to as close as possible to the received RDS subcarrier.

### Claim 11 (depends on 1)

The method as claimed in claim 1, wherein the phase-estimating block performs a calculation of phase deviation on the N last received symbols, N being an integer equal to 8.