# US 10,122,395 B2 · FM reception device, FM reception method for receiving FM signals

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- Number: US 10,122,395 B2
- Document ID: US10122395B2
- Status: Granted
- Kind: B2
- Application number: 15/635,492
- Filed: 2017-06-28
- Published: 2017-10-19
- Granted: 2018-11-06
- Earliest claimed: 2015-02-23
- Assignees: JVC KENWOOD Corporation
- Applicants: JVC KENWOOD Corporation
- Inventors: Yasuhide Okuhata
- Web page: https://patentgrep.com/patent/US10122395B2

## CPC

- H04B 1/10: Means associated with receiver for limiting or suppressing noise or interference
- H04B 1/16: Circuits
- H04B 1/26: for superheterodyne receivers (multiple frequency-changing H03D7/16)
- H04B 1/30: for homodyne or synchrodyne receivers (demodulator circuits H03D1/22)
- H04L 27/142: {Compensating direct current components occurring during the demodulation and which are caused by mistuning}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A first local oscillator generates a modulation signal of a predetermined frequency. A second local oscillator outputs a local oscillation signal frequency-modulated by using the modulation signal from the first local oscillator. A quadrature detection unit subjects an FM signal to quadrature detection by using the local oscillation signal output from the second local oscillator and outputs a base band signal. A first reduction unit and a second reduction unit reduce a direct current component contained in the base band signal. A correction unit restores the direct current component by correcting the base band signal such that the base band signal is centered around an origin of a polar coordinate system on an IQ plane. An FM detection unit subjects the corrected base band signal to FM detection and generates a detection signal.

## Claims

### Claim 1

An FM reception device comprising:
a modulation frequency generation unit that generates a modulation signal of a predetermined frequency;
a local oscillator that outputs a local oscillation signal frequency-modulated by using the modulation signal from the modulation frequency generation unit;
a quadrature detection unit that subjects an FM signal to quadrature detection by using the local oscillation signal output from the local oscillator and outputs a base band signal;
a reduction unit that reduces a direct current component contained in the base band signal output from the quadrature detection unit;
a correction unit that restores the direct current component by correcting the base band signal such that the base band signal is centered around an origin of a polar coordinate system on an IQ plane;
an FM detection unit that subjects the base band signal corrected by the correction unit to FM detection and generates a detection signal;
an addition unit that smoothes the detection signal generated in the FM detection unit and adds an offset to the detection signal;
an Auto Frequency Controller (AFC) unit that generates a first control signal for controlling a frequency of the local oscillation signal based on the smoothed detection signal to which the offset is added;
a selection unit that selects one of the first control signal from the AFC unit and the modulation signal from the modulation frequency generation unit as a second control signal and outputs the selected second control signal to the local oscillator; and
a control unit that generates a selection signal indicating a signal that should be selected in the selection unit, based on the detection signal generated in the FM detection unit.

### Claim 2 (depends on 1)

The FM reception device according to claim 1, wherein
the control unit includes a means to detect a carrier in the detection signal generated in the FM detection unit, the control signal generating the selection signal that causes the first control signal to be selected when a carrier is detected and causes the modulation signal from the modulation frequency generation unit to be selected when a carrier is not detected.

### Claim 3

An FM reception method comprising:
outputting a modulation signal of a predetermined frequency;
subjecting an FM signal to quadrature detection by using a local oscillation signal and outputting a base band signal;
reducing a direct current component contained in the base band signal;
restoring the direct current component by correcting the base band signal such that the base band signal is centered around an origin of a polar coordinate system on an IQ plane;
subjecting the corrected base band signal to FM detection and generating a detection signal;
adding an offset to the generated detection signal;
generating a control signal for controlling a frequency of the local oscillation signal based on the detection signal to which the offset is added; and
selecting one of the control signal and the modulation signal according to a selection signal generated based on the detection signal and outputting the selected signal to the local oscillator.

### Claim 4 (depends on 3)

The FM reception method according to claim 3, further comprising:
detecting a carrier in the detection signal, wherein
the selection signal causes the control signal to be selected when a carrier is detected and causes the modulation signal to be selected when a carrier is not detected.