JPH0534445A - Fw-cw radar - Google Patents

Abstract

PURPOSE:To easily and surely measure the distance to a target no matter how far the target is. CONSTITUTION:An increase sweep oscillator 11 for rectilinearly increasing frequencies from a lower limit value at every period and a decrease sweep oscillator 12 for rectilinearly decreasing the frequencies from an upper limit value at every period are provided on transmission side and signals output from the sweep oscillators 11, 12 are alternately switched from one to the other by a signal changeover switch 13 at every half the period to generate an excitation IF signal and the signal is applied to a target from an antenna 20 via a transmission mixer 22 and a transmitter 21. On the other hand, signals IF received from a first receiving mixer 24 are distributed to two parts by a distributor 14 on reception side and signals output from one of the two parts are mixed with those output from the increase sweep oscillator 11 by a reception descendent mixer 15 and frequency components equal to their difference are obtained and signals output from the other are mixed with those output from the decrease sweep oscillator 12 by a reception descendent mixer 16 and frequency components equal to their difference are obtained, and these frequency components are synthesized with each other by a synthesizer 17 and output to a filter bank 28, whereby the amount of frequency shift at every target becomes constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device, and more particularly to an FM-CW radar device.

[0002]

2. Description of the Related Art FIG. 10 shows a typical system diagram of a conventional FM-CW radar device. In the figure, 20 is an antenna, 21 is a transmitter, 22 is a transmission mixer, 23 is a local oscillator, and 24
Is a first mixer for reception, 25 is a swept oscillator, 26 is a second mixer for reception, 27 is a timing controller, 28 is a filter bank, 29 is a signal processor, 30 is a display, the upper stage is a transmission system, the lower stage is Indicates the receiving system.

The operation of this FM-CW radar device will be outlined. The timing controller 27 controls the sweep oscillator 25, and an excitation whose frequency fluctuates periodically and linearly between a lower limit value and an upper limit value with time is generated. The IF signal is output.
The timing controller 27 and the sweep oscillator 25 form an exciting unit.

Excitation I which is one output of the sweep oscillator 25
The F signal is mixed with the output of the local oscillator 23 in the transmission mixer 22 and converted into a high frequency transmission signal. A high-frequency transmission signal from the high-frequency signal conversion unit composed of the transmission mixer 22 and the local oscillator 23 is amplified by the transmitter 21, converted into an electromagnetic wave by the antenna 20, and irradiated on the target.

The radiated electromagnetic wave is reflected by the target object at a distance R, is received by the antenna 20 after a time of 2R / C (C: speed of light), and is converted into a high frequency reception signal here.

By the way, another target is the distance R '(> R).
, The time delay of the received signal with respect to the transmitted signal is 2
It becomes R '/ C. Therefore, this delay is about T (cycle) / 2
, The distance R ′ to another target is about C · T / 4
It is represented by.

The received signals from the target at the distance R and the target at the distance R'are mixed with the output of the local oscillator 23 by the first receiving mixer 24 and converted into a received IF signal. FIG. 11 is a frequency change diagram of these reception IF signals. The solid line shows the excitation IF signal output from the sweep oscillator 25, and the broken line shows the reception IF by the reflected wave from the target object at the distance R.
The signal and the alternate long and short dash line represent the received IF signal by the reflected wave from the target object at the distance R ′. Also, fH is the upper limit of the frequency, f
L is its lower limit.

Each received IF signal is received by the second receiving mixer 26.
At the other output of the sweep oscillator 25, the signal is mixed with the excitation IF signal, and a signal having a frequency of the difference is output. This signal contains a frequency component of a displacement amount proportional to the distance R to the target object, and signals from the target object at different distances R and R'have different frequency displacement amounts. FIG. 12 is a diagram showing changes in the frequency shift amount of these signals. 12
In the figure, the broken line and Δf indicate the signal and the frequency shift amount thereof by the target at the distance R, and the alternate long and short dash line and Δf ′ indicate the signal and the frequency shift amount thereof by the target at the distance R ′. The local oscillator 23, the first receiving mixer 24, and the second receiving mixer 26 form a receiving frequency detecting unit.

The output of the second receiving mixer 26 is frequency separated by a filter bank 28. FIG. 13 is a frequency change diagram of the output signal of the filter bank 28. In the figure, the broken line is the signal from the target at the distance R, and the mark ^ is the signal from the target at the distance R '.

The signal processing unit 29 detects and processes the output signals of each frequency from the filter bank 28 to generate the position information signal of each target. This allows distance measurement to the target object. The filter bank 28 and the signal processor 29 constitute a reception signal processing section.

Each target is output to the display 30 corresponding to the direction of the beam of the antenna 20, and is visualized here.

[0012]

However, in the conventional FM-CW radar device having the above-mentioned configuration, when the distance to the target object is R '(CT / 4), as is clear from FIG. Since the excitation IF signal and the reception IF signal cancel each other out over time, the range in which the frequency is constant, that is, the time during which the frequency changes are synchronized becomes very short, and the output of the filter bank 28 is almost obtained as shown in FIG. There is a problem that it becomes difficult to detect the target object when it disappears.

The present invention has been made in view of the above problems, and an object thereof is an FM that facilitates detection of a target object regardless of the distance of the target object.
-To provide a CW radar device.

[0014]

In order to achieve the above object, the present invention is a modification of the structures of the excitation section and the reception frequency detection section of the conventional FM-CW radar device.

That is, the exciter sweeps up the frequency of the output signal linearly until the frequency shift amount of twice the maximum frequency shift amount of the transmission signal is reached starting from the lower limit frequency for each cycle. An oscillator, a reduction sweep oscillator that linearly decreases the frequency of the output signal from the upper limit frequency for each cycle until the frequency shift amount that is twice the maximum frequency shift amount of the transmission signal is reached, and these sweep oscillators And a signal switching means for alternately switching the output signal of every 1/2 cycle and outputting it to the transmission signal conversion section. Further, the signal switching means is based on the timing signal generated by the reception signal processing section. And determines the frequency change timing of each output signal of the increasing sweep oscillator and the decreasing sweep oscillator, and halves the frequency change of these sweep oscillators.
A signal for inputting the output signals of the increasing sweep oscillator and the decreasing sweep oscillator and a timing controller that outputs a switching signal for each cycle, and alternately outputting one of these input signals when the switching signal is received. It is composed of a changeover switch.

On the other hand, the reception frequency detector is connected to the reception IF.
A divider that divides the signal into two, a receiving rising mixer that mixes one output signal of the divider and the output signal of the incremental sweep oscillator, and outputs the frequency component of the difference, and A receiving descending mixer that mixes the other output signal and the output signal of the decreasing sweep oscillator and outputs the frequency component of the difference, and a combiner that combines the output signals of these mixers and outputs to the received signal processing unit. It consisted of and.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Since the present invention is a modification of part of the configuration of the conventional FM-CW radar device, parts having the same functions as those of the conventional device are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows an FM-CW according to an embodiment of the present invention.
It is a block diagram of a radar device. In the figure, 10 is a timing controller, 11 is an increasing sweep oscillator, 12 is a decreasing sweep oscillator,
Reference numeral 13 is a signal changeover switch, and these parts 10 to 13
Constitutes the excitation part.

Further, 14 is a distributor, 15 is an ascending mixer for reception, 16 is a descending mixer for reception, and 17 is a combiner,
These components 14 to 17 form a reception frequency detection unit.

More specifically, the timing controller 1
0 controls the increasing sweep oscillator 11 and the decreasing sweep oscillator 12 based on the timing signal generated by the signal processor 29, determines the frequency change timing thereof, and
Further, a switching signal that determines the operation timing of the signal changeover switch 13 is generated.

As shown in FIG. 2, the incremental sweep oscillator 11 has a frequency shift amount twice as large as the maximum frequency shift amount (fH-fL) of the transmission signal, starting from the lower limit frequency fL for each period T. It linearly increases the frequency of the output signal until it is reached. At T / 2 (T is a cycle), the frequency becomes the upper limit frequency fH.

As shown in FIG. 3, the decreasing sweep oscillator 12 sets a frequency shift amount twice as large as the maximum frequency shift amount (fH-fL) of the transmission signal, starting from the frequency fH of the upper limit value for each period T. It linearly decreases the frequency of its output signal until it is reached. At the time of T / 2, the frequency becomes the lower limit frequency fL.

The signal change-over switch 13 inputs the output signals of the sweep oscillators 11 and 12, and alternately changes two input signals every 1/2 cycle based on the change-over signal from the timing controller 10. It is what is output. That is, 0 to T / 2, T to 3T / 2, 2T to 5T /
The output signal of the increasing sweep oscillator 11 is output during 2 ..., The output signal of the decreasing sweep oscillator 12 is output during T / 2 to T, 3T / 2 to 2T. As a result, an output signal having a frequency change as shown in FIG. 4 is obtained. This output signal is the same signal as the excitation IF signal of the conventional FM-CW radar device.

The timing controller 10 and the signal changeover switch 13 constitute a signal changeover means.

On the other hand, in the reception frequency detecting section, the distributor 14 divides the reception IF signal output from the first reception mixer 24 into two.

Further, the rising mixer 15 for reception is the distributor 1
4 outputs the frequency component of the difference by mixing one of the output signals of 4 and the output signal of the increasing sweep oscillator 11, and the receiving down mixer 16 and the other output signal of the distributor 14 and the decreasing signal. The output signal of the sweep oscillator 12 is mixed and the frequency component of the difference is output. 5 and 6 are frequency change diagrams of input and output signals of the rising mixer 15 for reception, and FIGS. 7 and 8 are falling mixer 1 for reception.
6 is a frequency change diagram of each of the input and output signals of FIG. In each figure, the broken line and Δf are the signal and the frequency shift amount due to the reflection from the target at the distance R, and the alternate long and short dash line and Δf ′ are the signal and the frequency shift amount due to the reflection from the target at the distance R ′. Referring to these figures, since the frequency change of each reception IF signal and the frequency change of the output signals from the increasing and decreasing sweep oscillators 11 and 12 are synchronized with each other in at least 1/2 cycle, the rising mixer for reception 15 and It can be seen that the output of the receiving down mixer 16 also has a constant frequency shift amount for each 1/2 cycle.

Further, the synthesizer 17 includes the mixers 15 and 1
The output signals of 6 are combined and output. The output signal of the synthesizer 17 is frequency-separated by the filter bank 28. FIG. 9 is a frequency change diagram of the output signal of the filter bank 28, in which the amount of frequency shift is constant for each distance R, R ′ and is output.

By detecting and processing the output of each frequency of the filter bank 28 by the signal processor 29, the distance measurement of each target is facilitated regardless of the distances R and R '. Each target object corresponds to the beam azimuth of the antenna 20 and the display 30
Is displayed in.

As described above, in the FM-CW radar device of the present embodiment, the excitation section is set to have twice the maximum frequency shift amount (fH-fL) of the transmission signal starting from the frequency of the lower limit value fL for each cycle T. An increasing sweep oscillator 11 that linearly increases the frequency of the output signal until the frequency shift amount is reached, and a frequency shift amount that is twice the maximum frequency shift amount (fH-fL) of the transmission signal starting from the upper limit frequency fH. Decrease sweeping oscillator 12 that linearly decreases the frequency of its output signal until reaching 0, and signal switching that outputs the output signals of these sweeping oscillators 11 and 12 alternately to each half cycle and outputs to the transmission mixer 22. Means, that is, a timing controller 10 and a signal changeover switch 13, and a receiving frequency detecting section for distributing a receiving IF signal to two, and one output signal of the distributor 14. And the output signal of the increasing sweep oscillator 11 are mixed to output the frequency component of the difference, and the other output signal of the distributor 14 and the output signal of the decreasing sweep oscillator 12 are mixed. And a receiving descending mixer 16 for outputting the frequency component of the difference,
A combiner 1 for combining the output signals of the mixers 15 and 16
7 and the output of the synthesizer 17 is applied to the filter bank 2
Since it is designed to lead to 8, the distance to the target is R '(
Even in the case of C · T / 4), the frequency shift amount Δf ′ of the output signal of the filter bank 28 becomes constant, and the distance can be measured without any trouble.

The frequency change timings of the sweep oscillators 11 and 12 and the switching timing of the signal change-over switch 13 are not required to be one cycle and one half cycle, respectively. It is easier than the radar device and can be set at an appropriate timing according to the distance to the target.

[0031]

As described above, according to the present invention,
It is possible to provide an FM-CW radar device that facilitates detection of a target regardless of the distance of the target.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an FM-CW radar device according to an embodiment of the present invention.

FIG. 2 is a frequency change diagram of an output signal of the incremental sweep oscillator according to the present embodiment.

FIG. 3 is a frequency change diagram of an output signal of the decreasing sweep oscillator according to the present embodiment.

FIG. 4 is a frequency change diagram of the output signal of the signal changeover switch according to the present embodiment.

FIG. 5 is a frequency change diagram of an input signal of the rising mixer for reception according to the present embodiment.

FIG. 6 is a frequency change diagram of the output signal of the rising mixer for reception according to the present embodiment.

FIG. 7 is a frequency change diagram of an input signal of the receiving descending mixer according to the present embodiment.

FIG. 8 is a frequency change diagram of the output signal of the receiving down mixer according to the present embodiment.

FIG. 9 is a frequency change diagram of the output signal of the filter bank according to the present embodiment.

FIG. 10 is a configuration diagram of a conventional FM-CW radar device.

FIG. 11 is a frequency change diagram of a conventional received IF signal.

FIG. 12 is a frequency change diagram of an output signal of a conventional second receiving mixer.

FIG. 13 is a frequency change diagram of an output signal of a filter bank by a conventional radar.

[Explanation of symbols]

10, 27 Timing controller 11 Incremental sweep oscillator 12 Decrease sweep oscillator 13 Signal changeover switch 14 distributor 15 Ascending mixer for reception 16 Down mixer for reception 17 synthesizer 20 Aerial 21 transmitter 22 Mixer for transmission 23 Local oscillator 24 First receiving mixer 25 sweep oscillator 26 Second receiving mixer 28 filter banks 29 Signal processor 30 indicator

Claims (3)

[Claims] 1. An excitation unit for generating an excitation IF signal of an intermediate frequency whose frequency periodically and linearly increases / decreases between its lower limit value and its upper limit value, and an output signal of the excitation unit, which are input as the frequency. And a transmission signal conversion unit for converting into a high-frequency transmission signal that is time-synchronized with the excitation IF signal; An antenna for receiving and converting to a high-frequency reception signal, and a reception for converting the reception signal converted by the antenna to a reception IF signal of an intermediate frequency and detecting a frequency difference between the reception IF signal and the excitation IF signal. In an FM-CW radar device having a frequency detection unit and a reception signal processing unit that separates a plurality of frequency components included in an output signal of the reception frequency detection unit to generate a position information signal for each target, The excitation unit is an increasing sweep oscillator that linearly increases the frequency of the output signal from the lower limit frequency as a starting point until a frequency shift amount that is twice the maximum frequency shift amount of the transmission signal is reached, and an upper limit frequency. From the starting point, a decreasing sweep oscillator that linearly decreases the frequency of the output signal until reaching a frequency shift amount that is twice the maximum frequency shift amount of the transmission signal, and switching the output signals of these sweep oscillators at a predetermined timing. The reception frequency detection unit includes a divider that divides the reception IF signal into two, and one output signal of the divider and the increase unit. By mixing the output signal of the sweeping oscillator and outputting the frequency component of the difference between the receiving rising mixer, the other output signal of the distributor and the output signal of the decreasing sweeping oscillator. A receiving falling mixer outputs the frequency components of the difference, FM-CW radar apparatus characterized by being configured by the synthesizer output to the reception signal processing unit combines the output signals of the mixers. 2. The exciter linearly increases the frequency of its output signal from the lower limit frequency for each cycle until the frequency shift amount reaches twice the maximum frequency shift amount of the transmission signal. A sweep oscillator, a reduction sweep oscillator that linearly decreases the frequency of the output signal from the upper limit frequency for each cycle until the frequency shift amount that is twice the maximum frequency shift amount of the transmission signal is reached, and these sweep oscillators The FM-CW radar device according to claim 1, further comprising a signal switching unit that alternately switches the output signal of the oscillator every 1/2 cycle and outputs the signal to the transmission signal conversion unit. 3. The signal switching means determines the frequency change timing of each output signal of the increasing sweep oscillator and the decreasing sweep oscillator based on the timing signal generated by the reception signal processing unit, and these sweep oscillators. A timing controller that outputs a switching signal every ½ cycle of the frequency change, and output signals of the increasing sweep oscillator and the decreasing sweep oscillator are input, and any one of these input signals is received when the switching signal is received. The FM-CW radar device according to claim 1 or 2, wherein the FM-CW radar device comprises a signal changeover switch that alternately outputs one of the two.