Method and apparatus for measuring distance to target using frequency-modulated continuous waves

Claim 3

A distance measuring method as set forth in claim 1, further comprising detecting a direction of a relative movement of the target with respect to said distance measuring apparatus.

Claim 4

A distance measuring method as set forth in claim 1, further comprising detecting a frequency of at least one of the Doppler signals for measuring the relative velocity of the target with respect to said distance measuring apparatus.

Claim 7

In an apparatus for measuring distance to a target of the type including means transmitting frequency modulated continuous waves to the target and receiving waves reflected from the target, the improvement comprising means for mixing a transmitted wave and a reflected wave so as to derive a low frequency wave, means for separating a Doppler signal from a low frequency wave obtained by mixing said transmitted and reflected waves, means for separating a fundamental wave component and harmonic components from said low frequency wave and separating Doppler signals therefrom, means for calculating the ratio in intensity between at least two of said separated Doppler signals on a time average, and means for measuring the distance to a target from said calculated ratio.

Claim 8

In an apparatus for measuring distance to a target of the type including means transmitting frequency modulated continuous waves to the target and receiving waves reflected from the target, the improvement comprising means for mixing a transmitted wave and a reflected wave so as to derive a low frequency wave, means for separating a Doppler signal from a low frequency wave obtained by mixing said transmitted and reflected waves, means for separating a fundamental wave component and harmonic components from said low frequency wave and separating Doppler signals therefrom, means for calculating the ratio in intensity between at least two of said separated Doppler signals on a time average, and means for measuring the distance to a target from said calculated ratio.

Claim 9

A distance measuring apparatus as set forth in claim 5 further comprising means for detecting a direction of a relative movement of the target with respect to said distance measuring apparatus.

Claim 10

A distance measuring apparatus as set forth in claim 5 further comprising means for detecting a frequency of at least one of the Doppler signals for measuring the relative velocity of the target with respect to said distance measuring apparatus.

Claim 11

A distance measuring apparatus as set forth in claim 6 further comprising means for detecting a frequency of at least one of the Doppler signals for measuring the relative velocity of the target with respect to said distance measuring apparatus.

Claim 12

A distance measuring apparatus as set forth in claim 6 wherein said means for detecting a direction of a relative movement of the target with respect to said distance measuring apparatus comprises a first low-pass filter for deriving one of said Doppler signals, a first saturation amplifier for shaping the output wave of the first low-pass filter into a rectangular wave, a second low-pass filter for deriving another Doppler signal, a second saturation amplifier for shaping the output wave of said second low-pass filter into a rectangular wave, a differentiation circuit for differentiating the output wave of said second saturation amplifier, a diode for passing only one polarity component of said differentiated wave, a time delay circuit for delaying said differentiated wave, a gate circuit connected to pass the output of said first saturation amplifier when the level of the output signal from the time delay circuit is in excess of a predetermined level, and an RS flip-flop connected to be set in response to the output of said gate, and reset in response to the output of said diode, whereby said RS flip-flop produces an output signal when the target is moving toward said distance measuring apparatus.

Claim 13

A distaNce measuring apparatus as set forth in claim 5, wherein said means for mixing said transmitted and reflected waves so as to derive a low frequency wave comprises an antenna, a circulator, a solid-type microwave oscillator connected to apply oscillations to said antenna by way of said circulator, a mixer connected to said circulator and an attenuator and a wide-band amplifier connected to receive signals from said mixer.

Claim 14

A distance measuring apparatus of claim 10 wherein said means for separating said low frequency wave and for deriving said Doppler signals comprises first and second band-pass amplifiers connected to said wide-band amplifier, the first and second mixers connected respectively to the outputs of said first and second band-pass amplifiers, a source of reference oscillations connected to said first mixers, a frequency divider connected to said reference oscillator for applying frequency desired oscillations to said second mixer, first and second low-pass filters connected to the outputs of said first and second mixers respectively for providing first and second Doppler signals, third low-pass filter means connected to said wide-band amplifier for providing a third Doppler signal, and automatic gain control means for controlling the gain of said wide-band amplifier.

Claim 15

The distance measuring apparatus of claim 11 wherein said means for calculating the ratio intensity comprises first and second logarithmic dividers, and AC to DC converting means for selectively applying the outputs of said low-pass filters to said logarithmic dividers.

Claim 16

The distance measuring apparatus of claim 12 wherein said means for measuring the distance to said target comprises first and second distance disciminators connected to the outputs of said logarithmic dividers and arithmetic mean generator means connected to the outputs of said distance discriminators.

Claim 17

The distance measuring apparatus of claim 7 wherein said means for detecting a frequency of at least one of the Doppler signals comprises first, second and third frequency to voltage converting means connected to receive three separate Doppler signals, and a pair of comparitor means connected to receive separate pairs of outputs of said frequency to voltage converting means.

Claim 18

A distance measuring apparatus as set forth in claim 7, wherein said means for mixing said transmitted and reflected waves so as to derive a low frequency wave comprises an antenna, a circulator, a solid-type microwave oscillator connected to apply oscillations to said antenna by way of said circulator, a mixer connected to said circulator and an attenuator and a wide-band amplifier connected to receive signals from said mixer.

Claim 19

A distance measuring apparatus of claim 14 wherein said means for separating said low frequency wave and for deriving said Doppler signals comprises first and second band-pass amplifiers connected to said wide-band amplifier, the first and second mixers connected respectively to the outputs of said first and second band-pass amplifiers, a source of reference oscillations connected to said first mixers, a frequency divider connected to said reference oscillator for applying frequency desired oscillations to said second mixer, first and second low-pass filters connected to the outputs of said first and second mixers respectively for providing first and second Doppler signals, third low-pass filter means connected to said wide-band amplifier for providing a third Doppler signal, and automatic gain control means for controlling the gain of said wide-band amplifier.

Claim 20

The distance measuring apparatus of claim 16 wherein said means for calculating the ratio intensity comprises first and second logarithmic dividers, and AC to DC converting means for selectively applying the outputs of said low-pass filters to said logarithmic dividers.

Claim 21

The distance measuring apparatus of claim 17 wherein said means for measuring the distance to said target comprises first and second distance discrIminators connected to the outputs of said logarithmic dividers and arithmetic mean generator means connected to the outputs of said distance discriminators.

Claim 22

The distance measuring apparatus of claim 18 wherein said means for detecting a frequency of at least one of the Doppler signals comprises first, second and third frequency to voltage converters connected respectively to the outputs of said first, second and third low-pass filters, and first and second comparitors connected to receive the outputs of separate pairs of said frequency to voltage converters, said apparatus further comprising a decision circuit connected to said arithmetic means generator means, and means applying the output of one of said converters to said decision circuit.

Claim 23

In an apparatus for measuring distance to a target of the type including means transmitting frequency modulative continuous waves to the target and receiving waves reflected from the target, the improvement comprising means for mixing a transmitted wave and a reflected wave so as to derive a low frequency wave, means for separating a fundamental wave component and harmonic component from said low frequency wave and separating Doppler signals therefrom, means for calculating the ratio intensity between at least two of said Doppler signals on a time average basis, and means for determining the distance to said target from said calculator ratio.

Claim 24

In an apparatus for measuring distance to a target of the type including means transmitting frequency modulative continuous waves to the target and receiving waves reflected from the target, the improvement comprising means for mixing a transmitted wave and a reflected wave so as to derive a low frequency wave, means for separating a fundamental wave component and harmonic component from said low frequency wave and separating Doppler signals therefrom, means for calculating the ratio intensity between at least two of said Doppler signals on a time average basis, and means for determining the distance to said target from said calculator ratio.

Claim 25

A distance measuring apparatus as set forth in claim 8 wherein said means for detecting a direction of a relative movement of the target with respect to said distance measuring apparatus comprises, a first low-pass filter for deriving one of said Doppler signals, a first saturation amplifier for shaping the output wave of the first low-pass filter into a rectangular wave, a second low-pass filter for deriving another Doppler signal, a second saturation amplifier for shaping the output wave of said second low-pass filter into a rectangular wave, a differentiation circuit for differentiating the output wave of said second saturation amplifier, a diode for passing only the positive component of said differentiated wave, a time delay circuit for delaying in time said positive differentiated wave, a gate circuit for passing the output signal of said first saturation amplifier when the level of the output signal from the time delay circuit is in excess of a predetermined level, and a RS flip-flop connected to be set in response to the output of said gate, and reset in response to the output of said diode, and provides an output signal when the target is moving toward said distance measuring apparatus, and said means for detecting a frequency of at least one of the Doppler signals comprises three frequency-voltage converters and two comparators.