# US 2022/0276366 A1 · Radar apparatus and distance measurement method

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- Number: US 2022/0276366 A1
- Document ID: US20220276366A1
- Status: Published application
- Kind: A1
- Application number: 17/637,662
- Filed: 2019-08-23
- Published: 2022-09-01
- Earliest claimed: 2019-08-23
- Assignees: Nippon Telegraph and Telephone Corporation
- Applicants: Nippon Telegraph and Telephone Corporation
- Inventors: Tatsuya IIZUKA; Fumihiko ISHIYAMA; Yohei TORIUMI; Jun KATO
- Web page: https://patentgrep.com/patent/US20220276366A1

## CPC

- G01S 13/341: {wherein the rate of change of the transmitted frequency is adjusted to give a beat of predetermined constant frequency, e.g. by adjusting the amplitude or frequency of the frequency-modulating signal}
- G01S 13/343: {using sawtooth modulation}
- G01S 7/356: {involving particularities of FFT processing}
- G01S 13/006: {Theoretical aspects (G01S7/418, G01S13/9094, G01S13/958 take precedence)}
- G01S 13/38: wherein more than one modulation frequency is used
- G01S 13/584: {adapted for simultaneous range and velocity measurements}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

A radar apparatus (1) of the present embodiment includes a transmitting unit (12) that transmits a frequency chirp signal whose frequency linearly changes with time, a receiving unit (13) that receives a reflected wave that is the frequency chirp signal reflected by an object, a mixer (14) that mixes the transmitted frequency chirp signal and the received reflected wave to obtain a beat signal, a frequency estimation unit (15) that estimates a frequency of the beat signal, and a distance estimation unit (16) that estimates a distance to the object based on the frequency of the beat signal. The frequency estimation unit (15) calculates an autoregressive coefficient of an autoregressive model from a sequence of discrete signal values of the beat signal and estimates the frequency of the beat signal using a base frequency that is based on a pole of the autoregressive model.

## Claims

### Claim 1

A radar apparatus comprising:
a transmitting unit comprising an antenna and configured to transmit a signal having a constant frequency or a continuous wave signal obtained by modulating the signal;
a receiving unit comprising one or more receiving attennas and configured to receive a reflected wave that is the continuous wave signal reflected by an object;
a mixer configured to mix the received reflected wave and the continuous wave signal to obtain a beat signal;
a frequency estimation unit comprising an analog-digital converter and configured to estimate a frequency of the beat signal; and
a distance estimation unit configured to estimate a distance to the object based on the frequency of the beat signal,
wherein the frequency estimation unit calculates an autoregressive coefficient of an autoregressive model from a sequence of discrete signal values of the beat signal and estimates the frequency of the beat signal using a base frequency that is based on a pole of the autoregressive model.

### Claim 2 (depends on 1)

The radar apparatus according to claim 1, wherein the continuous wave signal is a frequency chirp signal whose frequency changes linearly with time.

### Claim 3 (depends on 1)

The radar apparatus according to claim 1, wherein the frequency estimation unit calculates the autoregressive coefficient using an autocorrelation coefficient obtained by performing a convolution operation of the sequence of discrete signal values only within a duration of the beat signal.

### Claim 4

A distance measurement method comprising:
transmitting a signal having a constant frequency or a continuous wave signal obtained by modulating the signal;
receiving a reflected wave that is the continuous wave signal reflected by an object;
mixing the received reflected wave and the continuous wave signal to obtain a beat signal;
estimating a frequency of the beat signal; and
estimating a distance to the object based on the frequency of the beat signal,
wherein, in estimating of the frequency, an autoregressive coefficient of an autoregressive model is calculated from a sequence of discrete signal values of the beat signal and the frequency of the beat signal is estimated using a base frequency that is based on a pole of the autoregressive model.

### Claim 5 (depends on 4)

The distance measurement method according to claim 4, wherein the continuous wave signal is a frequency chirp signal whose frequency changes linearly with time.

### Claim 6 (depends on 4)

The distance measurement method according to claim 4, wherein, in estimating of the frequency, the autoregressive coefficient is calculated using an autocorrelation coefficient obtained by performing a convolution operation of the sequence of discrete signal values only within a duration of the beat signal.