JPH05215842A - Fm-cw radar device - Google Patents

Abstract

PURPOSE:To reduce an error per one count so as to compute the distance and relative speed to a target by detecting the sum of rise-fall numbers of beat signals in both up-down inclined blocks. CONSTITUTION:Pulsed beat signals are inputted into the respective data terminals C2 of programmable timer counter (PTM) 1, 2 and also into the respective data terminals C3 through an inverter (INV) 1. On the other hand, FM synchronizing signals are inputted into the gate terminals G2, G3 of the PTM 1 and simultaneously into the terminals G2, G3 of the PTM 2 through an inverter 2. On the basis of the pulsed beat signals inputted into the terminals C2, C3 of the PTM 1 (PTM 2), the PTM 1 (PTM 2) counts the rise-fall numbers of the pulsed beat signals in the up (down) inclined block of triangular wave modulation signals. On the basis of the sum value of the respective count numbers of the rise-fall numbers counted in the both up-down inclined blocks, a microprocessor unit MPU computes the distance and relative speed to a target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM-CW radar device, and more particularly to calculating information (distance and relative velocity) with respect to an object by counting the number of pulses of a pulsed beat signal. The present invention relates to an FM-CW radar device.

[0002]

2. Description of the Related Art This type of FM-in the prior art of FIG.
The configuration of a CW radar device is shown as an example. A PTM (programmable timer counter) and an MP
U (microprocessor unit) and the P
The FM synchronization signal output from the O1 terminal of TM is the integrator F
The triangular wave FM modulation signal is output from the integrator (modulation signal generator) to M, and the synchronization signal is input to the gate terminals G2 and G3 of the PTM directly or via the inverter INV. And the integrator FM
The frequency of the voltage controlled oscillator VCO is modulated by the modulation signal of the triangular wave output from the transmission signal, and the transmission signal FM-modulated in this way is radiated to the outside via the transmission antenna ANT1 and a part of the transmission signal. Is branched via a directional coupler C into a local signal, and the local signal and a reception signal reflected by a target in front and received via a reception antenna ANT2 are mixed by a mixer MIX to obtain a beat signal. Can be obtained.

The beat signal thus obtained is amplified by the amplifier AMP, then passed through the bandpass filter BPF, and then pulsed by the comparator COMP, and the pulsed beat signal of the PTM. It is input to the data terminals C2 and C3. Then, based on the synchronization signal input to the gate terminal G2 and the pulsed beat signal input to the data terminal C2,
The number of rising edges of the pulsed beat signal in the rising slope section of the triangular wave modulation signal (triangular wave of frequency fm as shown in FIG. 2A) is counted, while the rising number of the pulsed beat signal is counted through the inverter INV. Based on the sync signal input to the gate terminal G3 and the pulsed beat signal input to the data terminal C3, the pulsed beat signal in the downward slope section of the triangular wave modulation signal The number of rising edges of the PTM is counted, and thus the count number counted by the PTM is read from the PTM to the MPU in response to a predetermined interrupt request signal IRQ, and based on the read count data, The MPU calculates the distance or relative speed to the target.

FIG. 2B shows the waveform of the beat signal when the relative speed between the radar device and the target is 0, and FIG. 2C shows the beat signal. The situation is shown in which the signal is pulsed to count the number of rising edges of the pulsed beat signal in the upslope section and the downslope section of the modulated signal. It is shown that the rising numbers N of the beat signals generated are N = 4 and N = 3, respectively. As will be described later, the frequency of the beat signal when the relative velocity with the target object is 0 (it changes according to the distance to the target object) is the same in the up and down slope sections of the modulation signal. It is known that the value becomes a value (as shown in FIG. 2C, the number of rising edges of the pulsed beat signal in the ascending and descending slope sections is different when the relative speed is 0). Is due to an instantaneous pulse generated by the phase inversion of the beat signal that occurs when the modulated signal moves from the uphill section to the downhill section, and by counting the rising edges of the pulses in the uphill section) ..

On the other hand, in FIG. 4, when there is a relative velocity between the radar device and the target object, the frequency change of the transmission / reception signal (FIG. 4 (A)) and the beat signal frequency (FIG. 4) are shown.
4B), a beat signal waveform (FIG. 4C), and a pulsed beat signal waveform (FIG. 4D). That is, the transmission signal indicated by the solid line in FIG.
Is generated by modulating the frequency of O) is fo
With a frequency modulation width of ΔF and a cycle of 1 / fm (same as the cycle of the modulation signal) in a triangular wave shape,
Further, the transmission signal is reflected by the target object and received by the reception antenna (shown by a dotted line in FIG. 4A).
, The phase is delayed from the transmission signal by a predetermined time (proportional to the distance to the target).

Then, the frequency of the beat signal (generated by mixing the transmission signal and the reception signal) in the upslope section of the modulation signal is fup (usually referred to as an upbeat frequency), while the downslope of the modulation signal is obtained. Assuming that the frequency of the beat signal in the section is fdn (usually referred to as the downbeat frequency), the values of fup and fdn are equal when the relative speed to the target is 0 as described above (however, the value is Is proportional to the distance to the target), but when there is a relative velocity between the radar device and the target, the received signal is affected by the Doppler shift and the received signal is shown in FIG. As described above, the target object moves upward (for example, when the target object is approaching) or, conversely, moves downward (for example, when the target object is away).

Then, if the received signal is as shown in FIG.
4B, the value of the downbeat frequency fdn becomes larger than the value of the upbeat frequency fup, and the frequency value of the beat signal and the waveform of the beat signal are as shown in FIG. 4) and FIG. 4C, the up-slope section and the down-slope section of the modulated signal are different from each other, and accordingly, the pulse number of the pulsed beat signal is also shown in FIG. As shown in (D), the slope sections are different from each other.

Assuming that the frequency of the beat signal shown in FIG. 4C is fb, the relationship of fb = (4ΔFfm / C) R ± (2fo / C) V Yes (however, fo is the center frequency of the transmitted signal, Δ
F is the frequency modulation width of the transmission signal, fm is the modulation frequency, C is the speed of light, R is the distance to the target object, V is the relative speed to the target object, and when the relative speed V is not 0, fb
Is a different value in both slope sections).

In the above equation for the beat frequency fb, the frequency component relating to the distance R to the target object (that is, (4 · ΔF · fm / C) · R) is fr, and the relative speed V to the target object is V. Assuming that the component (i.e., the Doppler beat component (2 · fo / C) · V) is fd, when there is a relative velocity as shown in FIG. 4 (A), the downbeat frequency fdn and the upbeat are The frequencies fup are fdn = fr + fd and fu, respectively.
p = fr−fd, so fr = (fdn + f
up) / 2 and fd = (fdn-fup) / 2. Therefore, fr = (fdn + fup) / 2 = (4 · ΔF · fm /
C) R, R = (C / 4 · ΔF) · [(fdn + fup) / 2f
m] = (C / 4 · ΔF) (Ndn + Nup) (however, Nup
And Ndn represent the pulse number of the pulsed beat signal, that is, the upbeat pulse number and the downbeat pulse number, respectively, in the rising and falling slope sections of the triangular wave). On the other hand, fd = (fdn-fup) / 2 = (2 · fo / C) · V, V = (C · fm / 2 · fo) · [(fdn−fup) / 2fm] = (C · fm / 2 -Fo) (Ndn-Nup).

In this way, the distance R to the target and the relative speed V to the target can be calculated based on the upbeat pulse number Nup and the downbeat pulse number Ndn. As described above, in the prior art, as shown in FIG. 3 and FIG. 2C, each of the pulse numbers Nup and Ndn is counted so that only the rising number of each pulse is counted. ing.

However, when the beat pulse numbers Nup and Ndn of the upslope section and the downslope section are counted in this way, the beats generated when the upslope section moves to the downslope section as described above. An error may occur in the count number of the Nup or Ndn due to the instantaneous pulse generation due to the phase inversion of the signal, or the beat signal frequency fb itself may be different to some extent between the upslope section and the downslope section. Even if there is no difference between the count values of the beat pulse numbers Nup and Ndn, further, the number of counts to be counted as the Nup is shifted to the next section due to a signal bounce in the filter unit or the like, An error such as being counted as the Ndn may occur.

The error (error per 1 count) with respect to the distance R and the relative speed V, which occurs when the number of each beat pulse Nup or Ndn is erroneously counted by one count, is fo = 49.5 GHz, ΔF. = 7
Under the condition of 5 MHz and fm = 750 Hz, the above distance R
1 count error (that is, the above (C / 4
F) · (Ndn + Nup) in (Ndn + Nup)
Is ± 1 m when 1 is erroneously counted, and 1 count error for the relative speed V (that is, (Ndn-Nup) in (Cdn / 2nfo) (Ndn-Nup)) The error in the case of miscounting only 1) is ± 8 Km / h, and there is a problem that the error in the relative speed V becomes particularly large.

[0013]

The present invention has been made to solve the above problems, and reduces the error per count that occurs when the pulsed beat signals are pulse-counted, and the target object is reduced. Information such as the distance to or, relative speed, etc. can be calculated with high accuracy.

[0014]

According to the present invention, in order to solve the above problems, a local signal obtained by shunting a part of a transmission signal frequency-modulated by a modulation signal composed of a triangular wave and a reception signal are received. An FM-CW radar device having a means for pulsing a beat signal obtained by mixing with a received signal, the number of rising edges of the pulsed beat signal in each of the rising and falling sections of the triangular wave. A means for detecting the sum of the number of falling edges is provided, and based on the value of the sum of the number of rising edges and the number of falling edges in each of the detected intervals,
FM- characterized by calculating information for a target object
A CW radar device is provided.

[0015]

According to the above construction, by counting both the number of rising edges and the number of falling edges of the pulsed beat signal in the up and down slope sections, the up beat pulse number and the down beat pulse number can be calculated. The amount of information can be doubled, which can improve the accuracy of data such as the distance R to the target or the relative speed V.

[0016]

FIG. 1 shows an FM-CW as one embodiment of the present invention.
1 shows the overall configuration of a radar device. In FIG. 1, parts common to those in FIG. 3 are designated by common reference numerals. In this embodiment, the FM sync signal is output from the DOUT terminal of the MPU, and the PTM is the PTM1 for counting the number of rising edges and the number of falling edges of the pulsed beat signal in the upslope section, and A PTM2 is provided for counting the number of rising edges and the number of falling edge of the pulsed beat signal in the falling slope section.

As described above, the beat signal obtained by mixing the local signal obtained by branching a part of the transmission signal with the reception signal reflected by the target and received is pulsed by the comparator COMP, The beat signal pulsed in this manner is used as it is for the PTM1 and PTM1.
It is input to each data terminal C2 of TM2 and also input to each data terminal C3 of PTM1 and PTM2 via the inverter INV1. On the other hand, the FM synchronization signal is directly input to the gate terminals G2 and G3 of the PTM1, and the PT signal is output via the inverter INV2.
It is input to the gate terminals G2 and G3 of M2. In this way, based on the pulsed beat signals input to the respective data terminals C2 and C3 of the PTM1, the number of rising edges and the number of falling edges of the pulsed beat signals in the upslope section of the triangular wave modulation signal are calculated. Are counted in the PTM1, respectively, and based on the pulsed beat signals input to the data terminals C2 and C3 of the PTM2, the rising number and the rising number of the pulsed beat signals in the downward slope section of the modulation signal are set. The number of drops is the PTM
Each is counted in 2.

Thus, in the present invention, FIG.
As shown in (D), both the number of rising edges and the number of falling edges of the pulsed beat signal are counted in each of the upslope section and the downslope section of the modulated signal, and the sum of these counts ( (Indicated as N = 7 in the figure) is set as the number Nup of upbeat pulses and the number Ndn of downbeat pulses in each section, and the distance R or the relative speed V in the MPU is determined based on the values of these Nup and Ndn. Is calculated. As described above, in FIG. 2, the relative velocity with respect to the target object is 0.
The situation of the beat signal at the time is shown. Therefore, in this case, the values of Nup and Ndn are also equal (in the case of FIG. 2D, both Nup and Ndn are 7).

As described above, according to the present invention, when counting the values of Nup and Ndn, both the rising number and the falling number of the pulsed beat signal in each section are counted. As compared with the case where only the number of rising edges is counted as
Therefore, the distance R to the target and the relative speed V to the target are R = (C / 4.ΔF). [(Ndn + Nup) / 2] = ( C / 8 · ΔF) (Ndn + Nup) and V = (C · fm / 2 · fo) · [(Ndn-Nup) /
2] = (C.fm./4.fo)(Ndn-Nup), which is the error per count (that is, (Nd
The error in R or V when n + Nup) or (Ndn-Nup) is erroneously counted by 1) is half that in the case of the above-mentioned conventional technique. Therefore, as in the case of the above-mentioned conventional technique, fo = 49.5 GHz and ΔF = 75 M
Under the condition of Hz and fm = 750 Hz, the one-count error for the distance R is ± 0.5 m, and the one-count error for the relative speed V is ± 4 Km / h, and these errors are halved. become.

[0020]

According to the present invention, a one-count error in pulse counting a pulsed beat signal can be halved, so that the accuracy of the distance to the target and the relative speed can be improved. .. Therefore, it is possible to improve the feeling when the radar device according to the present invention is applied to the inter-vehicle distance control or the like during constant speed traveling.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an FM-CW radar device as one embodiment of the present invention.

FIG. 2 is a timing diagram showing the operation of the device shown in FIG. 1 in comparison with the case of the prior art.

FIG. 3 is a diagram illustrating a configuration of an FM-CW radar device in the related art.

FIG. 4 is a diagram illustrating an operating principle of the FM-CW radar device.

[Explanation of symbols]

MPU ... Microprocessor unit (microcomputer) PTM, PTM1, PTM2 ... Programmable timer counter FM ... FM modulation signal generator (integrating circuit) VCO ... Voltage controlled oscillator C ... Directional coupler ANT1, ANT2 ... Transmitting and receiving antenna MIX ... Mixer COMP ... Comparator INV, INV1, INV2 ... Inverter

Claims (1)

[Claims] 1. A means for pulsing a beat signal obtained by mixing a local signal obtained by shunting a part of a transmission signal frequency-modulated with a modulation signal composed of a triangular wave and a reception signal received through a reception antenna. Have FM-
A CW radar device, comprising means for detecting the sum of the number of rising edges and the number of falling edges of the pulsed beat signal in each section of the rising and falling slopes of the triangular wave. An FM-CW radar device, characterized in that information for a target object is calculated based on a value of a sum of the number of rising edges and the number of falling edges in a section.