JP2007298283A - Pulse radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse radar system using an FM-modulated wave which reduces FM-AM conversion noise. <P>SOLUTION: The pulse radar system using a transmission high-frequency signal for performing distance measurement in reception frequency conversion comprises an oscillation means which oscillates a non-modulated high-frequency signal in the measurement for a predetermined distance or less and oscillates a frequency-modulated high-frequency signal in the measurement for the predetermined distance or over, an amplitude modulation means which amplitude modulates the non-modulated high-frequency signal by a high-speed pulse signal amplitude modulated by a low-speed pulse signal and amplitude modulates the frequency-modulated high-frequency signal by the high-speed pulse signal, a transmitting means for radiating the high-frequency signal modulated by the frequency modulation means to the outside as a transmission signal, a receiving means for receiving the reflected wave of the transmission signal as a reception signal, a delay-time detection means for detecting the delay time of the reception signal, and a distance calculation means for determining the distance to an object using the delay time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pulse radar device, and more particularly to a pulse radar device that improves the detection sensitivity of a radar by removing an amplitude modulation component generated by frequency modulation.

  In recent years, millimeter-wave radar technology has attracted attention for applications such as obstacle detection on traffic roads, monitoring of passing vehicles, and ACC (Adaptive Cruise Control) of automobiles. In these radar technologies, an FM-CW (Frequency Modulated Continuous Wave) method is used, but it is difficult to measure an extremely short distance of several meters or less.

  As a radar that measures a very short distance, there is a pulse radar that uses a pulse with a width of several nsec (see Patent Document 1).

  In the pulse radar, in the pulse radar device that uses the transmission high-frequency signal as a local signal for reception frequency conversion, the pulse amplitude is modulated after the high-frequency oscillator of the transmission unit is frequency-modulated so as not to generate a null point in homodyne detection in the reception frequency conversion. Modulation is performed.

  Further, homodyne detection is also used in the reception unit of the conventional FM-CW radar, and the high frequency signal transmitted from the transmission unit is supplied as a local signal to a frequency converter (hereinafter referred to as a mixer) of the reception unit. Convert frequency to signal.

  In a radar using such frequency modulation (hereinafter referred to as FM modulation), an amplitude modulation component (hereinafter referred to as FM-AM conversion noise) generated by FM modulation when the frequency-to-amplitude characteristics of the high frequency FM modulator and the high frequency circuit are not flat. ) Occurs. The FM-AM conversion noise becomes unnecessary interference noise in the radar apparatus and lowers the sensitivity of radar measurement.

As a measure for reducing the FM-AM conversion noise, the FM modulated high frequency signal is further amplitude-modulated, and a radar reception signal having a frequency shifted by the amplitude modulation frequency is selected and extracted from the homodyne detection output of the radar receiver. There is a method of separating necessary radar received signals and unnecessary FM-AM conversion noise by frequency (see Patent Document 2).
JP 2004-264067 A JP-A-5-40169

  In the background art described above, the method of further amplitude-modulating the FM-modulated high-frequency signal and performing homodyne detection at the radar receiver can remove the component obtained by amplitude-detecting the FM-AM conversion noise at the homodyne detector output. The component shifted by the frequency of the amplitude modulation in the homodyne detection output also includes FM-AM conversion noise and cannot be separated from the necessary radar signal, so it was not a complete measure.

  Accordingly, one of the objects of the present invention is to provide a pulse radar device in which FM-AM conversion noise is reduced.

  The present invention is not limited to the above-described object, and the effects derived from the respective configurations shown in the best mode for carrying out the invention to be described later and which cannot be obtained by conventional techniques are another object of the present invention. Can be positioned as

(1) In the present invention, a pulse radar apparatus that uses a transmission high-frequency signal for distance measurement for reception frequency conversion, oscillates an unmodulated high-frequency signal when measuring a predetermined distance or less, and exceeds the predetermined distance. In this measurement, an oscillation means that oscillates a frequency-modulated high-frequency signal, and amplitude-modulates the non-modulated high-frequency signal with a high-speed pulse signal that is amplitude-modulated with a low-speed pulse signal, and the frequency-modulated high-frequency signal Amplitude modulation means for modulating the amplitude at the transmitter, transmission means for radiating the high-frequency signal modulated by the amplitude modulation means to the outside as a transmission signal, reception means for receiving a reflected wave of the transmission signal as a reception signal, and the reception A delay time detecting means for detecting a delay time of the signal; and a distance calculating means for obtaining a distance to the target using the delay time. The pulse radar apparatus according to use.

Preferably, the pulse radar device controls a modulation frequency and a modulation frequency width according to a distance measured by the pulse radar device, and a beat frequency obtained by the receiving unit is determined in the measurement over the predetermined distance. 2. The pulse radar device according to claim 1, further comprising control means for controlling to enter a predetermined band.
(2) In the present invention, the predetermined distance for switching the transmission high-frequency signal from non-modulation to frequency modulation is such that the difference between the transmission frequency and the reception frequency obtained by the receiving means is higher than the modulation frequency for frequency modulation. The pulse radar apparatus according to claim 1, wherein the distance is a corresponding distance.

Preferably, the pulse radar device according to claim 1, wherein the low-speed pulse signal for amplitude-modulating the unmodulated high-frequency signal is a pseudo-random code.
(3) According to the present invention, there is provided a pulse radar device that uses a transmission high-frequency signal as a local signal for reception frequency conversion, and oscillating means that oscillates the frequency-modulated high-frequency signal; First amplitude modulation means for modulating the amplitude with a modulation signal, transmission means for radiating the high-frequency signal modulated by the amplitude modulation means to the outside as a transmission signal, and reception means for receiving a reflected wave of the transmission signal as a reception signal And second amplitude modulation means for amplitude-modulating the received signal by a second modulation signal whose amplitude and phase are controlled in synchronization with the modulation signal for frequency modulation, and a modulation signal for frequency modulation. Third amplitude modulation means for amplitude-modulating a local signal used for the reception frequency conversion by a third modulation signal whose amplitude and phase are controlled synchronously; and A delay time detecting means for detecting the delay time of the item, a pulse radar apparatus is characterized in that a distance calculation means for calculating the distance to the target using the delay time.
(4) In the present invention, the second amplitude modulation means for modulating the amplitude of the received signal is based on the frequency-to-amplitude characteristic of the radar signal transmission path from the high-frequency signal transmitting means to the transmitting antenna, receiving antenna, and frequency converting means. 4. The pulse radar device according to claim 3, wherein the generated amplitude change component is canceled out.

  Preferably, the third amplitude modulating means for modulating the amplitude of the local signal cancels an amplitude change component generated by a frequency-to-amplitude characteristic of a local signal transmission path from the high frequency signal transmitting means to the frequency converting means. The pulse radar device according to claim 3 is used.

Preferably, the pulse radar device oscillates the non-modulated high frequency when measuring a predetermined distance or less, and oscillating means for oscillating the high-frequency signal frequency-modulated when measuring the predetermined distance or more; And an amplitude modulation means for modulating the amplitude of the high frequency signal by a high-speed pulse signal amplitude-modulated by a low-speed pulse signal, and amplitude-modulating the frequency-modulated high-frequency signal by a high-speed pulse signal. 3 is used.
(5) In the present invention, a pulse radar apparatus that uses a transmission high-frequency signal as a local signal for reception frequency conversion, an oscillation unit that oscillates the frequency-modulated high-frequency signal, and a triangular wave or a sawtooth wave that performs the frequency modulation. Band limiting means for band limiting the modulation signal, amplitude modulation means for pulse amplitude modulating the high frequency signal, transmission means for radiating the high frequency signal modulated by the amplitude modulation means to the outside as a transmission signal, and Receiving means for receiving a reflected wave as a received signal; band-pass filtering means for extracting a difference between a transmission frequency and a receiving frequency obtained by the receiving means; and a delay time detecting means for detecting a delay time of the received signal; A pulse radar apparatus comprising: a distance calculation unit that obtains a distance to the target using the delay time; There.

  Preferably, the band limiting means for the modulation signal of the triangular wave or sawtooth wave that performs the frequency modulation is a low-pass filter or a band rejection filter that cuts off a pass band of the band-pass means for extracting the beat frequency. A pulse radar device according to claim 5 is used.

  Preferably, the pulse radar device oscillates the non-modulated high frequency when measuring a predetermined distance or less, and oscillating means for oscillating the high-frequency signal frequency-modulated when measuring the predetermined distance or more; 6. An amplitude modulation means for modulating the amplitude of the high frequency signal by a high-speed pulse signal amplitude-modulated by a low-speed pulse signal and amplitude-modulating the frequency-modulated high-frequency signal by a high-speed pulse signal. The described pulse radar device is used.

  According to the present invention, a highly sensitive pulse radar device with reduced FM-AM conversion noise can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Example 1
In the first embodiment, the measurement period of the pulse radar is divided into a section in which the transmission high frequency is FM modulated and pulse amplitude modulated, and a section in which the non-modulated high frequency is pulse amplitude modulated.

  FIG. 1 shows a configuration of a radar system using the pulse radar device according to the first embodiment.

  In FIG. 1, 100 is a pulse radar device, 101 is a signal processing circuit, 102 is an FM modulation signal generation circuit, 103 is an FM oscillator, 104 is a coupling circuit, 105 is an amplifier, 106 is a transmission switch, 107 is a transmission switch drive circuit, 108 is a transmitting antenna, 109 is a radar reflector, 110 is a receiving antenna, 111 is a receiving switch, 112 is a receiving switch driving circuit, 113 is a delay sliding circuit, 114 is an amplifier, 115 is a local switch, 116 is a first mixer, 117 Denotes a second mixer, 118 denotes a BPF (bandpass filter), and 119 denotes a composite pulse generation circuit.

  In FIG. 2, the signal waveform of each part in Example 1 is shown.

2, D201 in FIG. 2A is a low-speed pulse signal, D202 in FIG. 2B is a composite pulse signal waveform, D203 in FIG. 2C is an FM modulation signal waveform, and D204 in FIG. Each local switch control signal is shown.
・ "Operation of pulse radar"
The operation of the pulse radar device 100 according to the first embodiment will be described using the system configuration diagram shown in FIG. 1 and the signal waveforms of the respective units shown in FIG.

  The FM oscillator 103 outputs a high-frequency signal that is FM-modulated by the FM modulation signal D203 supplied from the FM modulation signal generation circuit 102.

FM signal D203, as shown in FIG. 2 (c), since the interval of the beginning of the _{T m1} in period _{T m0} is a constant value, FM oscillator 103 is unmodulated continuous wave (a to _{f c} frequency) Output. In the section _{T m2} after period _{T m0,} since a triangular wave of period _{T m} (repetition frequency _{f m = 1 / T m)} , FM oscillator 103 center frequency a _{f c,} which is FM-modulated by a triangular wave The high frequency of the FM-CW signal (with modulation width Δf) is output.

  The output of the FM oscillator 103 is supplied to the transmission switch 106 via the coupling circuit 104 and the amplifier 105.

The high-speed pulse signal (with repetition frequency f _s ) generated from the signal processing circuit 101 is composite-modulated with the low-speed pulse signal _D 201 (with repetition frequency f _d ) in the composite pulse generation circuit 119, so that the composite pulse signal D 202 is generated. Generated. The composite pulse signal D202 is shortened in the transmission switch driving circuit 107 and drives the transmission switch 106.

As a result, the output of the transmit switch 106, FIG. 2 (b) ~ interval _{T m1} in (c) is a signal the continuous high-frequency unmodulated is pulse amplitude modulated by a composite pulse signal _D202, section _{T m2} is D203 The high-frequency wave modulated by the triangular wave is further amplitude-modulated by the high-speed pulse signal indicated by D202, and is radiated from the transmitting antenna.

The radar reflected wave reflected by the radar reflector 109 is received by the receiving antenna 110 and becomes a received signal. The reception signal is switched by the reception switch 111 with a short pulse. Switch signal for driving the receiving switch 111, the transmission switches a repetition frequency f _s of the same high-speed pulse signal and an amplitude modulated signal, high-speed pulse signal having the frequency f _s is, the signal processing in the delay sliding circuit 113 of FIG. 1 the delay control signal from the circuit 101, the delay time (the tau _c) is controlled so as to change sequentially in the reception switch drive circuit 112 is short-pulsed signal.

Only when the short pulse time of the high-speed pulse signal controlled so that the delay time τ _c changes sequentially and the short pulse time of the reception signal coincide with each other, the output of the reception switch 111 is the high-speed pulse signal having the repetition frequency f _s. The high-frequency signal amplitude-modulated with is output.

  The output of the reception switch 111 is amplified at a high frequency by the amplifier 114, and in the first mixer 116, the output of the FM oscillator 103 for transmission is mixed with a local signal branched by the coupling circuit 104 and subjected to homodyne detection.

In the section of the _{T m1} in FIG. 2 (a) ~ (d) , the received signal input to the first mixer 116, a non-modulated high frequency, high-speed pulse signal at intervals of the waveform of _{T m1} of D202 (repetition frequency _{f s} ) And a low-speed pulse signal (repetition frequency f _d ), and the other local signal input to the first mixer 116 is turned off by the local switch 115 by the control signal D204 from the signal processing circuit 101. Therefore, the signal is not input to the first mixer 116. Therefore, in the section of T _m1 , the first mixer 116 detects the amplitude of only the received signal, and at the output of the first mixer 116, the waveform of the T _m1 section of D202 is obtained as an intermediate frequency (hereinafter referred to as IF: Intermediate Frequency) signal.

In the section of the _{T m2} in FIG. 2 (a) ~ (d) , the received signal input to the first mixer 116, a high frequency is FM-modulated by the waveform of D203, are further amplitude modulated in a section of the waveform of the _{T m2} of D202 It is a waveform. The other local signal input to the first mixer 116 is a signal that is FM-modulated by the waveform D203 because the local switch 115 is turned on by the control signal D204 from the signal processing circuit 101. To enter. Therefore, the first mixer 116 in a section of the T _m2 operates as homodyne detector, first mixer 116 output is a fast pulse signal with a sine wave of the beat frequency corresponding to the distance to the radar reflector in the FM-CW radar system An IF signal output in which the amplitude of (repetition frequency f _s ) changes is obtained.

The IF signal output from the first mixer 116 is synchronously detected by the second mixer 117 using the delayed high-speed pulse signal (repetition frequency f _s ) as a reference signal.

The drive pulse signal of the reception switch 111 that has passed the reception signal and the reference signal of the high-speed pulse signal supplied to the second mixer 117 are signals controlled by the delay sliding circuit 112 so as to change sequentially with the same delay time. Therefore, the repetition frequency is completely synchronized with f _s , and even if the delay time is controlled to change sequentially, the phase difference is 0 degree and does not change.

In the second mixer 117, a section of _{T m1} in FIG. 2 (a) ~ (d) a low-speed pulse signal D201 is _detected, the frequency of the difference between the FM-modulated waves received with the transmitted FM modulated signal in a section of the _{T m2} sine wave of the beat frequency _{f b} is detected is, and outputs the BPF118.

The pass band of the BPF 118 is designed to have a bandwidth through which the repetition frequency f _d of the low-speed pulse signal D201 and the beat frequency f _b pass. However, in the conventional FM-CW method, (1) as shown in the formula, the beat frequency f _b in proportion to the distance R _x to the radar reflector is changed.

ただし、ΔfはＦＭ変調の変調幅で、ｆ_ｍはＦＭ変調三角波の繰り返し周波数、Ｒ_ｘはレーダ装置からレーダ反射体までの距離、ｃは光速である。

However, Delta] f is the modulation width of FM modulation, f _m is the repetition frequency of the FM modulated triangular wave, the distance from the R _x radar apparatus to the radar reflector, c is the speed of light.

In this pulse radar, changing the Δf or f _m in accordance with the distance R _x may be measured.

In the present pulse radar, the reception signal of the reflected wave from the radar reflector 109 at the distance R _x is switched by the reception switch 111 driven by the high-speed pulse signal whose delay time sequentially changes, and the delay time τ _{x of the} reception signal When the signal coincides with the delay time (τ _c ) of the high-speed pulse signal that drives the reception switch 111, it passes through the reception switch 111, is frequency-converted, and is supplied to the BPF 118.

Note that the relationship of the controlled delay time τ _c corresponding to the delay time τ _x of the received signal corresponding to the distance R _x to the radar reflector is expressed by equation (2).

前記受信スイッチ１１１を駆動する高速パルス信号の遅延時間τ_ｃに応じて、（１）式における（Δｆｆ_ｍ）の値をＲ_ｘに対し反比例するように制御することにより、ビート周波数ｆ_ｂは一定値ｆ_ｂ０となる。

The beat frequency f _b is constant by controlling the value of (Δff _m ) in the equation (1) so as to be inversely proportional to R _x in accordance with the delay time τ _c of the high-speed pulse signal that drives the reception switch 111. The value _fb0 .

For example, if the reference state is Δf = 100 MHz and fm = 6 kHz at a distance R _x = 1.5 m, the beat frequency f _b = 12 kHz is obtained from the equation (1). In the delay time for measuring the distance R _x = 3 m, if Δf is halved in inverse proportion to twice the distance and changed to 100 MHz / 2 = 50 MHz, the beat frequency f _b is It is maintained at 12 kHz.

In the actual case, since the value of (Δff _m ) is controlled to be approximately inversely proportional to R _x , the beat frequency f _b slightly changes. When the radar reflector is moving, the beat frequency changes due to the Doppler effect, so the bandwidth of the BPF 118 is widened by these changes.
The signal processing circuit 101 calculates the received signal level of the signal that has passed through the BPF 118.

When the received signal level shows a peak value above a certain value for each delay sliding time, the distance R _x to the radar reflector is calculated by the equation (2) for the delay time τ _c .
・ "Generation of FM-AM conversion noise"
Frequency of the FM modulator 103 and, if the frequency vs. amplitude characteristics in the path of the local signal, from the FM modulator 103 to the first mixer via the local switch 115 is not flat, caused by FM modulation of a triangular wave of repetition frequency f _m A high frequency signal having an amplitude modulation (hereinafter referred to as FM-AM conversion) component is supplied to the first mixer 116 as a local signal.

The first mixer 116 detects the amplitude of the FM-AM conversion component of the received local signal even when there is no radar reflected wave input. The received local signal has a component that leaks to the amplifier 114 via the first mixer 116, is reflected again by the amplifier 114, and is input to the first mixer 116. Since amplifier 114 is affected by the receive switch 111 which is switched at a frequency f _s, components the reflected again local signal is combined to the amplitude modulation at the frequency f _m of the switch frequency f _s and FM-AM conversion . This signal is an IF signal output and the amplitude detection monkey in the first mixer 116, the signal amplitude of the frequency f _s changes at the frequency f _m. The IF signal is at the second mixer 117 is the synchronous detection frequency _{f s} as a reference signal, a second mixer 117 outputs the component of the frequency _{f m.}

Also for the received signal, the frequency-to-amplitude characteristic is flat in the path of the high-frequency transmission circuit from the high-frequency FM modulator 103 to the output of the transmission antenna 108 and the high-frequency circuit from the reception antenna 110 to the first mixer 116. If no, the received signal FM-AM conversion by the triangular wave of the repetition frequency f _m is a homodyne detection by the first mixer 116, a pulse signal of the switch frequency fs becomes the IF signal output which is amplitude modulated at a frequency of f _m, in a second mixer 117, it is synchronous detection frequency _{f s} as a reference signal, a second mixer 117 outputs the component of the frequency _{f m.}

Component of the frequency f _m becomes FM-AM conversion noise, if not blocked by BPF118, it becomes unnecessary noise in the radar measurement, degrading the measurement sensitivity.
・ "Relationship between beat signal and FM-AM conversion noise frequency"
To avoid the effect of FM-AM conversion noise as described in above, it is necessary to separate the frequency f _m of the beat signal frequency f _b and the unwanted FM-AM conversion noise desired.

First, the relationship between the frequencies f _b and f _m will be described.

In the pulse radar according to the first embodiment, in order to obtain a stable value in the reception level calculation, in the FM-CW section of T _m2 in FIG. 2, the rising and falling sections of the triangular wave having the period T _m (= 1 / f _m ) The section T _m / 2 needs to include a beat signal having a frequency f _b of ½ period or more. This relationship is expressed by equation (3).

ただし、周波数ｆ_ｂとｆ_ｍの成分を分離するには（３）式の不等号を満たす適切な関係が必要であるので後で説明する。

However, in order to separate the components of the frequencies f _b and f _m , an appropriate relationship that satisfies the inequality sign of the expression (3) is necessary, and will be described later.

The FM modulation width Δf has an upper limit value Δf _max by hardware in order to obtain good FM modulation characteristics.

ミリ波周波数を利用するレーダでは、例えば、Δｆ_ｍａｘ＝１００ＭＨｚである。
（１）、（３）、（４）式より、Δｆが許容される変化範囲は（５）式となる。

In a radar using a millimeter wave frequency, for example, Δf _max = 100 MHz.
From the expressions (1), (3), and (4), the change range in which Δf is allowed is the expression (5).

またΔｆの値は（１）式より（６）式となる。

Further, the value of Δf is expressed by equation (6) from equation (1).

また、ｆ_ｂ／ｆ_ｍは（７）式となる。

_{Further, f} b / f _m is (7).

計測距離Ｒ_ｘを変化させた時に、ビート周波数ｆ_ｂを所定の一定値にするために、ｆ_ｍを所定値に決め、（７）式によりΔｆを制御する。

When changing the distance measured R _x, to the beat frequency f _b at a predetermined constant value, determines the f _m to a predetermined value, controls the Δf by equation (7).

Delta] f when measuring distance R _x is large, by changing the equation (6), if f b _/ f _m (3) is set to type conditions, the allowable range of Delta] f (5) below is satisfied It is.

On the other hand, even if Δf when the measurement distance R _x becomes small is not increased beyond the maximum possible value Δf _max even if it is increased by the equation (6), it is fixed at Δf _max . At this time (.DELTA.fr _x) becomes smaller, the _{R x} is smaller than the predetermined value (7) _f b / _{f m} by equation becomes smaller than 1. This indicates a state in which the beat signal having the frequency f _b is not included in the rising and falling sections T _m / 2 of the triangular wave, and the calculated received signal level is not accurate.

Further, the distance measured when _{R x} is _f b / _{f m} in the case of short-range pole is close to 1, close repetition frequency _{f m} of the beat frequency _{f b} and the triangular wave, since it is difficult to separate the frequency by BPF118 The unnecessary FM-AM conversion noise appears at the output of the BPF 118 for extracting the desired beat signal. The FM-AM conversion noise included in the local signal input to the first mixer 116 is output from the BPF 118 at a level irrespective of the presence / absence of the reception signal from the radar reflector, and the FM-AM conversion noise included in the reception signal is received. Output from the BPF 118 at a level proportional to the level. Both of these become unnecessary noise for distance measurement and degrade measurement sensitivity.

In particular, at an extremely short distance with a small _Rx , the value of Δf is large according to the equation (6), so the FM-AM conversion noise level is also large, and the measurement sensitivity of the radar is greatly degraded.

In the above description, Δf is changed according to the equation (6) corresponding to the measurement distance _Rx . (6) increase in Δf Changing the f _m in formula appears to be reduced.

However, according to (6) obtained by modifying the equation (7), when fixing the case _{R x} is smaller Delta] f in Delta] f _max, since f b / _{f m} are also approaches 1, separation of _{f b} and _{f m} is Similarly, it will not be possible.

To reduce the FM-AM conversion noise in the pulse radar, it is necessary to separate by separating the f _b and f _m, if it is important f b _/ f _m is changed if in of R _x and Δf is there. (7) According to the _{formula, f} b / f _m is determined by Δf and _{R x.} Therefore, only by changing the Δf when measuring distance R _x is changed, f b _/ f _m is the predetermined ratio. According to the equation (7), if Δf and R _x are determined, even if f _m is changed, f _b only changes at the same ratio, and therefore it is not related to the separation of frequency f _b and frequency f _m .
・ "Removal method of FM-AM conversion noise"
In the first embodiment, in order to remove the influence of the FM-AM conversion noise at the extremely short distance described above, when measuring the distance of the radar reflector below a predetermined distance, the FM modulation of the transmission high frequency is stopped and the amplitude modulation is performed. use.

The lower limit of the distance R _x at which the above-described disadvantage does not occur will be described.

(5) a minimum limit when it comes to equality of _{R x} in formula (3) is also from the case of _f b = _{f m} becomes equal, you can not separate the _{f b} and _{f m} in formula.

The BPF118, it is necessary to block the _{f m} is passed through the _{f b.}

For example, when f _b ≧ 2f _m and f _b and f _m are separated, equation (8) is obtained from equation (6).

例えばΔｆの最大値Δｆ_ｍａｘ＝１００ＭＨｚの場合（８）式よりＲｘ≧１．５ｍとなる。
即ち、計測距離Ｒ_ｘが（８）式による下限距離以下の距離計測の場合は、図２におけるＴ_ｍ１に対応し、低速パルス信号周波数ｆ_ｄを例えば１２ｋＨzの矩形波とし、高速パルス信号周波数ｆ_ｓを例えば１０ＭＨｚの矩形波を振幅変調して複合パルス信号とし、短パルス化して送信スイッチ１０６により高周波を振幅変調する。

For example, when the maximum value Δf _{max of} Δf is 100 MHz, Rx ≧ 1.5 m from the equation (8).
That is, in the case of distance measurement where the measurement distance R _x is equal to or less than the lower limit distance according to the equation (8), the low-speed pulse signal frequency f _d is a rectangular wave of 12 kHz, for example, corresponding to T _m1 in FIG. the _s example a square wave at 10MHz and amplitude modulated composite pulse signal, the high-frequency amplitude-modulated by the transmission switch 106 to short pulses.

On the other hand, in the case of distance measurement where the measurement distance is equal to or greater than the lower limit distance according to equation (8), the high frequency of radar transmission is FM-modulated corresponding to T _m2 in FIG.

By this method, the section of Tm ₁ in FIG. 2 for measuring _Rx at a very short distance is not a beat signal level by FM modulation, but a signal level calculation for detecting a low-speed pulse signal of 12 kHz, for example. The FM-AM conversion noise does not occur due to the modulation, and it is not necessary to consider the wave number of the beat signal within the FM period.

In the section of Tm ₂ in FIG. 2 where the distance R _x far from the predetermined distance is measured, the level of the beat signal by FM modulation is calculated, and the distance R _x is measured. In the measurement of this distance range, and giving the desired beat frequency _{f b} (e.g. 12 kHz) prescribed _{f m} (eg 6 kHz), is varied to Δf by (6) in accordance with the measured distance changes _{R x,} a constant beat A frequency f _b (for example, 12 kHz) is obtained.

In this case, the relation of _{f b} is a 12kHz constant _f b = 2f _m is maintained, the beat frequency _{f b} by BPF118 is passed, to block repetition frequency _{f m} of the FM-AM conversion noise It becomes possible.

In this case, for example, f _b = 12 kHz, f _m = 6 kHz, the center frequency f _c = 12 kHz of the BPF 118, and the passband width ΔW = 6 kHz (f _c ± 3 kHz) are set.

However, the passband width ± 3 kHz is a value in consideration of the Doppler frequency depending on the moving speed of the radar reflector 109, and the 3 kHz Doppler frequency corresponds to, for example, about 20 km / h of the radar reflector in the case of a millimeter wave of 76 GHz. To do. If, for example, a 6th-order Butterworth filter is used as the BPF 118, an attenuation of about 35 dB can be obtained at the FM-AM conversion noise repetition frequency f _m = 6 kHz, so that the FM-AM conversion noise can be sufficiently reduced.

Further, according to the equation (6), when the measurement distance R _x is large, Δf is controlled to a small value in inverse proportion to R _x , so that the FM-AM conversion noise itself is small, and the influence of the FM-AM conversion noise is It can be reduced.

In Example 1, to take adequate separation of _{f b} and _{f m} by selection characteristic BPF118, was a _{f b} ≧ 2f _m, if narrow selection characteristic BPF118, is _{f b} within the range according to (3) Can be close to f _m .

  In the pulse radar apparatus 100 according to the first embodiment shown in FIG. 1, the first mixer 116 is operated as an amplitude detector when the local switch 115 is turned off, and the first mixer 116 is turned on when the local switch 115 is turned on. Was operated as a homodyne detector. As described above, the level of the received signal is sufficiently high because the radar detector is operated in the vicinity of the pole to operate as an amplitude detector. At this time, even if the local switch 115 is kept on, the amplitude detection component can be output by the actual nonlinear characteristic of the first mixer 116.

Accordingly, even if the local signal is actually supplied to the first mixer 116 without the local switch 115, the low-speed pulse signal based on the amplitude modulation and the composite pulse signal based on the high-speed pulse signal in the first embodiment (T in D202 in FIG. 2). _The same signal as the waveform in the section _m1 ) can be taken out from the first mixer 116, so that the effect of the present invention can be obtained.
(Example 2)
In the second embodiment, a circuit that cancels FM-AM conversion noise is used.

  FIG. 3 shows a configuration of a radar system using the pulse radar device 300 according to the second embodiment.

  3, the same components as those in FIG. 1 are denoted by the same reference numerals, 300 is a pulse radar device, 301 is a cancellation signal generator, 302 is a cancellation signal generator, and 303 is an amplifier.

The operation of the pulse radar apparatus 300 in FIG. 3 is the same as the operation in the FM modulation section T _m2 in the first embodiment. In the second embodiment, there is no amplitude modulation section T _m1 and all of one cycle T _m0 is FM modulated. ing.

Further, the FM modulation frequency width Δf is controlled so as to change according to the equation (6) with respect to the measurement distance R _x as in the first embodiment.
・ "FM-AM conversion noise cancellation operation"
The FM-AM conversion noise canceling operation according to the second embodiment will be described with reference to FIGS. 3 and 4.

  FIG. 4 shows signal waveforms at various parts in the second embodiment.

  4, D 401 in FIG. 4A is an FM modulated signal input to the FM oscillator 103, D 402 in FIG. 4B is a local signal waveform input from the coupling circuit 104 to the amplifier 303, and the reception switch 111 to the amplifier 114. The input waveform, D403 in FIG. 4C is a cancellation signal output from the cancellation signal generator 301 and the cancellation signal generator 302, and D404 in FIG. 4D is the first mixer 116 from the amplifier 303 and the amplifier 114. Each of the high-frequency signals in which the FM-AM conversion component input to is canceled is shown.

  The received signal that has received the radar reflected wave from the radar reflector 109 is amplitude-modulated in synchronism with the triangular wave D401 of the FM modulation signal by the frequency characteristics in the high-frequency path from the FM oscillator 103 to the receiving switch 111, and for example, the waveform of D402 It has become. The cancellation signal generator 301 generates, for example, a signal D403 in synchronization with the triangular wave D401 of the FM modulation signal.

  The cancellation signal D403 is adjusted in amplitude and phase so as to have a waveform that cancels the amplitude modulation component of the reception signal D402, and the gain of the amplifier 114 is controlled to modulate the amplitude of the reception signal D402. The output of the amplifier 114 becomes D404, and the amplitude modulation component generated by the FM-AM conversion disappears. The reception signal having a constant amplitude is frequencyd by the first mixer 116 and the second mixer, and the beat signal not including the component subjected to the FM-AM conversion is supplied to the signal processing circuit 101 via the BPF 118.

  The high-frequency signal input as a local signal to the first mixer 116 has, for example, a waveform of D402 that is amplitude-modulated in synchronization with the triangular wave D401 of the FM modulation signal due to frequency characteristics in the local signal path from the FM oscillator 103 to the amplifier 303. ing.

  In FIG. 4, for simplicity of explanation, the waveform of the local signal and the waveform of the radar received signal are the same waveform D402. However, since the path of the radar signal and the path of the local signal are actually different, the frequency characteristics are also different. The FM-AM conversion component is also different.

  The amplitude-modulated component cancellation signal D403 by the FM-AM conversion of the local signal is adjusted in amplitude and phase so as to have a waveform that cancels the amplitude-modulated component of the local signal D402, and the gain of the amplifier 303 is controlled to amplitude the local signal. Modulate. The output of the amplifier 303 becomes D404, and the amplitude modulation component generated by the FM-AM conversion disappears.

  The local signal D404 having a constant amplitude is supplied to the first mixer 116. When the radar reception signal is present, the radar reception signal is frequency-converted, and the conversion gain of the first mixer 116 changes depending on the amplitude of the local signal, The FM-AM conversion component is prevented from being superimposed on the amplitude. When there is no radar reception signal, the first mixer 116 operates as an amplitude detector. However, since the local high frequency signal D404 has an amplitude-modulated component canceled by FM-AM conversion, the first mixer 116 outputs No FM-AM conversion noise appears. Therefore, FM-AM conversion noise does not appear in the signal supplied to the signal processing circuit 101 via the second mixer 117 and the BPF 118.

The cancellation signal generator 301 and the cancellation signal generator 302 AD-convert the triangular wave D401 of the FM modulation signal, and then perform FFT (Fast Fourier Transform), and then the beat frequency (frequency = f _b ) of the radar reception signal. Only the FFT frequency spectrum component passing through the BPF 118 that passes through may be taken out and DA-converted to generate the cancellation signal D403.

  The amplifier 114 and the high-frequency transistor constituting the amplifier 303, for example, a gate bias DC voltage or a drain bias DC voltage of a HEMT (High Electron Mobility Transistor) are superimposed on the cancellation signal D403, and the amplifier 114, By controlling the gain of the amplifier 303, FM-AM conversion noise in D402 may be canceled.

Further, the in the entire range of measurement distance _{R x} in the description, the pulse radar device 300 has been FM-modulated transmission frequency by a triangular wave, (7) Measurement of _f b / _{f m} is very close range _{R x may} approach the 1 by equation Then, like the section of T _{m1 in} the first embodiment, the FM modulation of the high-frequency signal is stopped, the high-frequency signal is amplitude-modulated by the composite pulse obtained by amplitude-modulating the high-speed pulse signal by the low-speed pulse signal, and the low-speed pulse signal is received by the receiving unit. You may use together the method of extracting.

In this case, in the measurement of the distance _Rx that is more than the very short distance, as described above, the amplitude modulation component included in the received signal and the cancellation of the amplitude modulation component included in the local signal are synchronized with a triangular wave that is FM-modulated. The signal is canceled by the signal, and the receiving unit extracts the beat signal. By this method, FM-AM conversion noise can be reduced in the measurement of the entire distance range from a very short distance to a long distance.
(Example 3)
In the third embodiment, band limitation for removing a component that passes through the beat frequency band is performed in the radar receiving unit with respect to the triangular wave signal that FM modulates the transmission harmonic, and FM modulation is performed using the band-limited signal.

  FIG. 5 shows a configuration of a radar system using the pulse radar device 500 according to the third embodiment.

  5, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, 500 is a pulse radar device, and 501 is an LPF (low pass filter).

The operation of the pulse radar apparatus 500 in FIG. 5 is the same as that in the FM modulation section T _m2 in the first embodiment. In the third embodiment, there is no amplitude modulation section T _m1 and all of one cycle T _m0 is FM modulated. ing.

Further, the FM modulation frequency width Δf is controlled so as to change according to the equation (6) with respect to the measurement distance R _x as in the first embodiment.

However, the waveform for FM modulation is not a triangular wave but a waveform in which a predetermined band is cut off by a filter, which is different from the first embodiment.
・ "Removal method of FM-AM conversion noise"
A method for reducing FM-AM conversion noise in the third embodiment will be described with reference to FIGS. 5 and 6.

FIG. 6A shows an example of a frequency spectrum component of FM-AM conversion noise generated by a triangular FM modulated wave. However, the ideal triangular wave includes only the fundamental frequency f _m and the odd harmonics 3f _m , 5f _m ..., But in reality, due to the nonlinearity of the frequency vs. amplitude characteristics in the amplifying circuit and high frequency circuit of the triangular wave, even harmonics _2f m of _{f m} as the 6 (a), 4f _m components also occur. harmonic component of f _m component and f _m is the operation described in the "occurrence of FM-AM conversion noise" in Example 1, in Example 3 and outputs from the second mixer 117 of FIG.

Characteristics of BPF118 of 5 is shown in D601 of FIG. 6 (b), the beat frequency _{f b} at the same time when the components are extracted, the FM-AM conversion noise falling within the passband of the BPF118 harmonic 3f _m and 4f _{The m} component is extracted and becomes an unnecessary interference wave.

That is, in FIG. 6, for example, when f _m = 4 kHz, f _b = 14 kHz, and the passband width of the BPF 118 is 14 kHz ± 3 kHz, 3 f _m = 12 kHz, 4 f _m = 16 kHz, and therefore the harmonics of FM-AM conversion noise thereby extracting 3f _m and 4f _m component.

FIG. 6C shows a spectrum when the triangular wave of the FM modulated wave is band-limited by the LPF 501 in the third embodiment. LPF501 is, for example, cut-off frequency = 6 kHz, 6-order Butterworth low-pass _filter, the 3f m = 12 kHz and _4f m = 16 kHz, the attenuation characteristic over 35dB is obtained.

Consequently, _3f m of FM-AM conversion noise, 4f _m components, as shown in FIG. 6 (c), greatly reduced, components to be input to the pass band of BPF118 in FIG. 6 (d) desire only becomes a wave beat frequency f _b component, as a result, FM-AM conversion noise input to the signal processing circuit 101 is reduced.
"Beat frequency component in Example 3"
The beat frequency by the band-limited triangular wave FM modulated signal in the third embodiment will be described with reference to FIGS. 6 and 7.

  FIG. 7 shows the frequency change of each part subjected to FM modulation in the third embodiment in comparison with the prior art.

  In FIG. 7A, D701 is the frequency of the transmission signal that is FM-modulated by the triangular wave band-limited according to the third embodiment, D702 is the frequency of the reception signal received by delaying D701, and in FIG. D703 is the beat frequency according to the third embodiment, in FIG. 7C, D704 is the frequency of the transmission signal by the conventional triangular wave FM modulation, D705 is the frequency of the reception signal received by delaying D604, and in FIG. , D706 respectively indicate beat frequencies by conventional triangular wave FM modulation.

In the prior art, the transmission high frequency D704 that has been FM-modulated by the triangular wave is reflected by the radar reflector 109, delayed in accordance with the distance and becomes the reception high frequency D705, and the difference frequency between D704 and D705 becomes the beat frequency D706. Top of the frequency of the flat portion of the D706 is the beat frequency _{f b} represented by formula (1).

In the third embodiment, the transmission high-frequency frequency that is FM-modulated by the band-limited triangular wave has the frequency change waveform of D701 in FIG. 7 (a), and reception that is delayed according to the distance when reflected by the radar reflector 109. A high frequency waveform D702 is obtained, and a frequency difference between D701 and D702 is a beat frequency D703. Center frequencies near the top of the D703 is the beat frequency _{f b} represented by formula (1). Summit vicinity of the beat frequency of the FIG. 7 (b), has a but slightly changed component of the frequency f _b than in FIG. 7 (d), lowering of f _b component by band limiting is slight.

  Further, the pulse radar device 500 according to the third embodiment does not measure the distance from the value of the beat frequency as in the FM-CW method, but delays the gating pulse that maximizes the level of the beat signal that has passed through the BPF 118. Since the distance is measured by this, a slight change in the beat frequency is not a problem as long as it is within the band of the BPF 118.

  Further, although the pulse radar device 500 according to the third embodiment uses the LPF 501 as a filter that limits the band of the FM modulation signal, the band blocking filter that cuts off the pass band of the BPF 118 that extracts the beat signal may be used. In the same manner, FM-AM conversion noise can be reduced.

Further, in the entire range of measurement distance R _x in the description, the pulse radar device 500 has been FM-modulated transmission frequency by a triangular wave whose band is limited, (7) pole short distance f _{b /} f _m approaches 1 by equation In the measurement of _Rx , the FM modulation of the high-frequency signal is stopped, and the high-frequency signal is amplitude-modulated by a composite pulse obtained by amplitude-modulating the high-speed pulse signal by the low-speed pulse signal, as in the section of T _{m1 in} the first embodiment. Then, a method of extracting a low-speed pulse signal may be used in combination.

In this case, in the measurement of the distance _Rx greater than or equal to the very short distance, the high-frequency signal is FM-modulated with the band-limited triangular wave, and the beat signal is extracted in the receiving unit. By this method, FM-AM conversion noise can be reduced in the measurement of the entire distance range from a very short distance to a long distance.
(Appendix 1)
A pulse radar device that uses a transmission high-frequency signal for distance measurement for reception frequency conversion,
Oscillating means for oscillating an unmodulated high-frequency signal for measurement of a predetermined distance or less, and for oscillating a frequency-modulated high-frequency signal for measurement of the predetermined distance or more,
Amplitude modulation means for amplitude-modulating the unmodulated high-frequency signal with a high-speed pulse signal amplitude-modulated with a low-speed pulse signal, and amplitude-modulating the frequency-modulated high-frequency signal with a high-speed pulse signal;
Transmitting means for radiating the high-frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to the target using the delay time.
(Appendix 2)
The pulse radar device controls the modulation frequency and the modulation frequency width according to the distance measured by the pulse radar device, and the beat frequency obtained by the receiving means is within a predetermined band in measurement over the predetermined distance. The pulse radar device according to appendix 1, further comprising control means for controlling to enter.
(Appendix 3)
The predetermined distance for switching the transmission high-frequency signal from non-modulation to frequency modulation is a distance corresponding to a higher frequency than a modulation frequency at which the difference between the transmission frequency obtained by the receiving means and the reception frequency is modulated. The pulse radar device according to Supplementary Note 1, wherein the pulse radar device is characterized.
(Appendix 4)
The pulse radar apparatus according to claim 1, wherein the low-speed pulse signal for amplitude-modulating the unmodulated high-frequency signal is a pseudo-random code.
(Appendix 5)
A pulse radar device that uses a transmission high-frequency signal as a local signal for reception frequency conversion,
Oscillating means for oscillating the frequency-modulated high-frequency signal;
First amplitude modulation means for amplitude-modulating the high-frequency signal with a first modulation signal of a high-speed pulse;
Transmitting means for radiating the high frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
Second amplitude modulation means for amplitude-modulating the received signal with a second modulation signal whose amplitude and phase are controlled in synchronization with the modulation signal for frequency modulation;
Third amplitude modulation means for amplitude-modulating a local signal used for the reception frequency conversion by a third modulation signal whose amplitude and phase are controlled in synchronization with the modulation signal for performing frequency modulation;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to the target using the delay time.
(Appendix 6)
The second amplitude modulating means for modulating the amplitude of the received signal cancels an amplitude change component generated by a frequency-to-amplitude characteristic of a radar signal transmission path from the high-frequency signal transmitting means to a transmitting antenna, a receiving antenna, and a frequency converting means. The pulse radar device according to appendix 5, wherein
(Appendix 7)
The third amplitude modulation means for amplitude modulating the local signal cancels an amplitude change component generated by the frequency-to-amplitude characteristic of the local signal transmission path from the high-frequency signal transmission means to the frequency conversion means. The pulse radar device described.
(Appendix 8)
The pulse radar device oscillates the non-modulated high frequency when measuring a predetermined distance or less, and oscillating means for oscillating the frequency-modulated high frequency signal when measuring a predetermined distance or more,
Amplitude modulation means for amplitude-modulating the unmodulated high-frequency signal with a high-speed pulse signal amplitude-modulated with a low-speed pulse signal, and amplitude-modulating the frequency-modulated high-frequency signal with a high-speed pulse signal;
The pulse radar device according to appendix 5, characterized by comprising:
(Appendix 9)
A pulse radar device that uses a transmission high-frequency signal as a local signal for reception frequency conversion,
Oscillating means for oscillating the frequency-modulated high-frequency signal;
Band limiting means for band limiting the modulation signal of the triangular wave or sawtooth wave that performs the frequency modulation;
Amplitude modulation means for pulse amplitude modulating the high-frequency signal;
Transmitting means for radiating the high frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
Bandpass filtering means for extracting the frequency of the difference between the transmission frequency and the reception frequency obtained by the receiving means;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to a target using the delay time.
(Appendix 10)
The band limiting means for the modulation signal of the triangular wave or the sawtooth wave that performs the frequency modulation is a low-pass filter or a band rejection filter that cuts off a pass band of the band-pass means for extracting the beat frequency. The pulse radar device according to appendix 9.
(Appendix 11)
The pulse radar device oscillates the unmodulated high frequency when measuring a predetermined distance or less, and oscillating means for oscillating the frequency-modulated high frequency signal when measuring a predetermined distance or more,
Amplitude modulation means for amplitude-modulating the unmodulated high-frequency signal with a high-speed pulse signal amplitude-modulated with a low-speed pulse signal, and amplitude-modulating the frequency-modulated high-frequency signal with a high-speed pulse signal;
The pulse radar device according to appendix 9, characterized by comprising:

It is a figure which shows a pulse radar system structure (Example 1). It is a figure which shows the signal waveform (Example 1) of each part. It is a figure which shows a pulse radar system structure (Example 2). It is a figure which shows the signal waveform (Example 2) of each part. It is a figure which shows a pulse radar system structure (Example 3). It is a figure which shows a beat spectrum (Example 3). It is a figure which shows FM modulation signal and beat frequency (Example 3).

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Pulse radar apparatus 101 Signal processing circuit 102 FM modulation signal generation circuit 103 FM oscillator 104 Coupling circuit 105 Amplifier 106 Transmission switch 107 Transmission switch drive circuit 108 Transmission antenna 109 Radar reflector 110 Reception antenna 111 Reception switch 112 Reception switch drive circuit 113 Delay Sliding circuit 114 Amplifier 115 Local switch 116 First mixer 117 Second mixer 118 BPF (Band pass filter)
119 Compound Pulse Generation Circuit 300 Pulse Radar Device 301 Cancellation Signal Generator 302 Cancellation Signal Generator 303 Amplifier 500 Pulse Radar Device 501 LPF (Low Pass Filter)

Claims (5)

A pulse radar device that uses a transmission high-frequency signal for distance measurement for reception frequency conversion,
Oscillating means for oscillating an unmodulated high-frequency signal for measurement of a predetermined distance or less, and for oscillating a frequency-modulated high-frequency signal for measurement of the predetermined distance or more,
Amplitude modulation means for amplitude-modulating the unmodulated high-frequency signal with a high-speed pulse signal amplitude-modulated with a low-speed pulse signal, and amplitude-modulating the frequency-modulated high-frequency signal with a high-speed pulse signal;
Transmitting means for radiating the high-frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to the target using the delay time.   The predetermined distance for switching the transmission high-frequency signal from non-modulation to frequency modulation is a distance corresponding to a higher frequency than a modulation frequency at which the difference between the transmission frequency obtained by the receiving means and the reception frequency is modulated. The pulse radar device according to claim 1, characterized in that: A pulse radar device that uses a transmission high-frequency signal as a local signal for reception frequency conversion,
Oscillating means for oscillating the frequency-modulated high-frequency signal;
First amplitude modulation means for amplitude-modulating the high-frequency signal with a first modulation signal of a high-speed pulse;
Transmitting means for radiating the high frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
Second amplitude modulation means for amplitude-modulating the received signal with a second modulation signal whose amplitude and phase are controlled in synchronization with the modulation signal for frequency modulation;
Third amplitude modulation means for amplitude-modulating a local signal used for the reception frequency conversion by a third modulation signal whose amplitude and phase are controlled in synchronization with the modulation signal for performing frequency modulation;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to the target using the delay time.   The second amplitude modulation means for modulating the amplitude of the received signal cancels the amplitude change component generated by the frequency-to-amplitude characteristic of the radar signal transmission path from the high-frequency signal transmitting means to the transmitting antenna, the receiving antenna, and the frequency converting means. The pulse radar device according to claim 3. A pulse radar device that uses a transmission high-frequency signal as a local signal for reception frequency conversion,
Oscillating means for oscillating the frequency-modulated high-frequency signal;
Band limiting means for band limiting the modulation signal of the triangular wave or sawtooth wave that performs the frequency modulation;
Amplitude modulation means for pulse amplitude modulating the high-frequency signal;
Transmitting means for radiating the high frequency signal modulated by the amplitude modulating means to the outside as a transmission signal;
Receiving means for receiving a reflected wave of the transmission signal as a received signal;
Bandpass filtering means for extracting the frequency of the difference between the transmission frequency and the reception frequency obtained by the receiving means;
A delay time detecting means for detecting a delay time of the received signal;
A pulse radar apparatus comprising: distance calculation means for obtaining a distance to the target using the delay time.

Images