Radar device

1. A radar device comprising:

processing circuitry to

generate a radar signal whose frequency changes, over time, nonlinearly with respect to the time;

output the generated radar signal as a reference wave, transmit the radar signal to a target, and receive a returning radar signal reflected from the target as a reflected wave;

detect a beat signal indicating a difference frequency between a frequency of the output reference wave and a frequency of the received reflected wave, and convert the beat signal into a digital signal from an analog signal; and

calculate a distance correspondence value corresponding to the distance to the target from the converted digital signal and calculate the distance to the target from the distance correspondence value,

generate, as a replica signal of the digital signal, a signal having a sampling period same as a sampling period of the beat signal upon conversion of the beat signal from an analog signal into the digital signal;

calculate an inner product of the converted digital signal and the generated replica signal;

calculate, as the distance correspondence value corresponding to the distance to the target, an absolute value of the calculated inner product; and

calculate the distance to the target from the calculated absolute value.

2. The radar device according to claim 1 ,

wherein the processing circuitry further converts the beat signal that is defined as a first beat signal into a first digital signal from an analog signal and converts a second beat signal that is delayed in phase by 90 degrees with respect to the first beat signal into a second digital signal from an analog signal, and

the processing circuitry generates, as a first replica signal of the first digital signal, a signal having a same sampling period as a sampling period of the first beat signal upon conversion of the first beat signal into the first digital signal from an analog signal, generates, as a second replica signal of the second digital signal, a signal having the sampling period, and generates a complex replica signal that is a complex signal from the first replica signal and the second replica signal;

generates a complex digital signal that is a complex signal from the first digital signal and the second digital signal and calculates an inner product of the complex digital signal and the complex replica signal;

calculates, as the distance correspondence value corresponding to the distance to the target, an absolute value of the calculated inner product; and

calculates the distance to the target from the calculated absolute value.

3. The radar device according to claim 1 ,

wherein the processing circuitry further divides the beat signal in two, one of the divided signals being a first beat signal, and the other of the divided signals being a second beat signal, converts the first beat signal into a first digital signal from an analog signal, and converts the second beat signal into a second digital signal from an analog signal at a sampling period that is delayed in phase by 90 degrees with respect to a sampling period of the first beat signal upon conversion of the first beat signal from the analog signal into the first digital signal, and

the processing circuitry

generates, as a first replica signal of the first digital signal, a signal having a same sampling period as the sampling period of the first beat signal, generates, as a second replica signal of the second digital signal, a signal having a same sampling period as the sampling period of the second beat signal, and generates a complex replica signal that is a complex signal from the first replica signal and the second replica signal;

generates a complex digital signal that is a complex signal from the first digital signal and the second digital signal and calculates an inner product of the complex digital signal and the complex replica signal;

calculates, as the distance correspondence value corresponding to the distance to the target, an absolute value of the calculated inner product; and

calculates the distance to the target from the calculated absolute value.