JP2006112915A - Short pulse radar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a short pulse radar in low consumption power, using a submillimeter wave band (UWB) of 22-29 GHz. <P>SOLUTION: The short pulse radar includes a transmitting part 21 for repeatedly radiating short pulse waves to a space 1; a receiving part 30 for receiving and detecting the reflected wave of the short pulse waves radiated into the space 1; a signal processing part 45 for performing analysis processing of an object 1a existing in the space 1, on the basis of detection output of the receiving part 30; and a control part 50 for controlling the transmitting part 21 and the receiving part 30, on the basis of the analysis result of the signal processing part 45. The control part 50 stops the supply of a power source Bt to the transmission part 21 within a period until the transmission part 21 radiates the next short pulse wave after it radiates the short pulse to the space, and stops the supply of a power source Br to the receiving part 30 within a period, except the period of receiving the reflected wave in the radiated short pulse wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention radiates a narrow-width pulse wave (short pulse wave) to a space at a predetermined period, receives a reflected wave from an object in the space, detects it, and analyzes the object in the space based on the detection output Among the short-pulse radars used in the 22-29 GHz quasi-millimeter wave band (UWB), which is allocated for in-vehicle radars and radars for assisting the walking of visually handicapped persons. It relates to technology.

  A pulse radar that searches for an object in space using a pulse wave basically has the configuration shown in FIG.

  That is, the transmission unit 11 receives a trigger signal G output at a predetermined cycle Tg from the control unit 16 to be described later, generates a pulse wave Pt having a predetermined carrier frequency and having a predetermined width synchronized with the trigger signal G. It radiates to space through the transmitting antenna 11a.

  The pulse wave Pt is reflected by the object 1a in the space 1, and the reflected wave Pr is received by the receiving antenna 12a of the receiving unit 12 and detected.

  The signal processing unit 15 uses, for example, the timing at which a pulse wave is transmitted from the transmission unit 11 as a reference timing, obtains the timing at which the detection output D is output from the reception unit 12 and the output waveform thereof, and obtains an object present in the space 1 Analyze 1a. The control unit 16 performs various controls on the transmission unit 11 and the reception unit 12 based on the processing result of the signal processing unit 15 and the like.

  The basic structure of such a pulse radar is disclosed in the following Patent Documents 1 and 2.

Japanese Patent Laid-Open No. 7-012921 Japanese Patent Laid-Open No. 8-313619

  Among the pulse radars having such a basic configuration, those for in-vehicle use, which are being put into practical use in recent years, use a millimeter wave band (77 GHz), search for a high-output, narrow angular range at a long distance, and perform collisions. Use the quasi-millimeter wave (22-29 GHz) for the purpose of supporting high speed driving such as prevention and driving control, and search for a wide range of angles with low power and short distance, blind spot assistance, garage parking assistance, etc. Some are intended for assistance during low-speed driving.

  This quasi-millimeter wave band is planned to be used for UWB (Ultra Wide Band) wireless communications in the future, and is considered to be used not only for in-vehicle radars but also for walking aid radars and short-range communication systems for visually impaired persons. It is done.

  Since UWB has a wide band, a radar system can use a short pulse with a width of 1 ns or less, and can realize a radar with high distance resolution.

  However, there are various problems to be solved in order to realize a short pulse radar using this UWB.

  One of the important issues is low power consumption considering the incorporation into various vehicles and portable use. Especially in the case of a walking support system, the entire device is made small so that it is easy to carry. In addition, it is necessary to reduce the weight, and it is inevitably necessary to drive the apparatus with a small battery for a long time.

  On the other hand, a semiconductor element used in a high frequency band such as the UWB consumes more power than a semiconductor element for a low frequency band, and even if the circuit configuration of the device is simplified, the above requirement cannot be met. .

  An object of the present invention is to solve this problem and provide a short pulse radar with low power consumption.

In order to achieve the above object, the short pulse radar according to claim 1 of the present invention comprises:
Based on a transmission unit (21) that repeatedly radiates a short pulse wave into space, a reception unit (30) that receives and detects a reflected wave of the short pulse wave radiated into the space, and a detection output of the reception unit And a signal processing unit (45) that performs analysis processing of an object existing in the space, and a control unit (50) that controls the transmission unit and the reception unit based on the analysis result of the signal processing unit. In pulse radar,
The controller is
The power supply to the transmission unit is stopped within a period from when the transmission unit emits a short pulse wave to the space until the next short pulse wave is emitted.

The short pulse radar according to claim 2 of the present invention is the short pulse radar according to claim 1,
The controller is
Within a period from when the transmitting unit emits a short pulse wave to space until it emits the next short pulse wave, and during a period excluding a period for receiving a reflected wave of the emitted short pulse wave, The power supply to the receiving unit is stopped.

The short pulse radar according to claim 3 of the present invention is the short pulse radar according to claim 1 or 2,
The controller is
The short pulse wave is radiated to the space after a predetermined time has elapsed since the start of power supply to the transmitter, and the power supply is stopped after the short pulse wave is emitted.

The short pulse radar according to claim 4 of the present invention is the short pulse radar according to claim 3,
The controller is
The receiving unit starts supplying power to the receiving unit in accordance with the start of power supply to the transmitting unit, and after the period for receiving the reflected wave of the short pulse wave radiated into the space by the transmitting unit has elapsed. It is characterized in that the power supply to is stopped.

The short pulse radar according to claim 5 of the present invention is the short pulse radar according to claim 3 or claim 4,
The controller is
Bias power is supplied before supplying power to the transmitter or receiver.

The short pulse radar according to claim 6 of the present invention is the short pulse radar according to claim 1, claim 2, claim 3, claim 4, or claim 5.
The controller is
When an analysis result indicating that no object is present in the space is received from the signal processing unit, control is performed such that the short pulse wave radiation interval by the transmission unit is increased.

The short pulse radar according to claim 7 of the present invention is the short pulse radar according to claim 1,
Have a temperature sensor,
The controller is
The period for stopping the power supply to the transmission unit is changed according to the temperature detected by the temperature sensor.

The short pulse radar according to claim 8 of the present invention is the short pulse radar according to claim 1,
Have a temperature sensor,
The controller is
The power supply stop period for the receiving unit is changed in accordance with the temperature detected by the temperature sensor.

  As described above, in the short pulse radar according to the present invention, the power supply to the transmitter is stopped at least within the period from the transmission of the short pulse wave to the transmission of the next short pulse wave. Can be realized.

  In addition, the power supply to the receiving unit is intermittently performed, thereby further reducing power consumption.

  In addition, the configuration in which the power supply stop period to the transmission unit or the reception unit is changed according to the temperature detected by the temperature sensor can prevent a change in device characteristics with respect to a large change in environmental temperature, and can operate stably. be able to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of a short pulse radar 20 to which the present invention is applied.

  The short pulse radar 20 includes a transmission unit 21, a reception unit 30, a signal processing unit 45, and a control unit 50.

  The transmission unit 21 generates and transmits a short pulse wave Pt having a predetermined carrier frequency Fc (for example, 26 GHz) with a predetermined width Tp (for example, 1 ns) every time the trigger signal G output from the control unit 50 with a predetermined period Tg is received. Radiates from the antenna 22 to the space 1. Note that the transmission antenna 22 may be shared with the reception antenna 31.

  As shown in FIG. 1, the transmission unit 21 includes a pulse generator 23 for generating a pulse signal Pa having a width Tp synchronized with the trigger signal G, and a signal having a carrier frequency Fc for Tp while receiving the pulse signal Pa. An oscillator 24 that oscillates and outputs the power, a power amplifier 25 that amplifies the output signal of the oscillator 24 and supplies the amplified signal to the transmission antenna 22, and a band rejection filter (BRF) 26 that suppresses out-of-band unnecessary radiation.

  Here, the oscillator 24 is made into one chip by the MMIC, and inside thereof, as shown in FIG. 2, an input common AND circuit and a NAND circuit are integrated, and an input of the gate circuit 24a. The emitter follower type input buffers 24b and 24c connected to each other, the output buffer 24d connected to the output part of the gate circuit 24a, and the delay circuit 24e that delays the inverted output of the gate circuit 24a and inputs it to one input buffer 24b. And have.

  In the oscillator 24 having this configuration, while the pulse signal Pa having the period Tg shown in FIG. 3A is being input to the input buffer 24c, a rectangular shape having a predetermined frequency (carrier frequency) as shown in FIG. A wave signal Pb is oscillated and output in bursts.

  The frequency of the output signal Pb is determined by the sum of the input / output delay time of the input buffer 24b and the gate circuit 24a and the delay time of the delay circuit 24e, but the input / output delay time of the input buffer 24b and the gate circuit 24a is general. Therefore, in this case, a part of the constant of the delay circuit 24e is configured to be variable, and this constant is adjusted so that the oscillation frequency is approximately the center of the UWB (for example, 26 GHz).

  Since the transmission unit 21 is configured to control the oscillation operation of the oscillator 24 by the pulse signal Pa as described above, no carrier leakage occurs in principle. Therefore, the limitation on the power density defined when using the UWB only needs to be considered for the instantaneous power of the short pulse wave output at the time of oscillation, and the specified power can be used most effectively.

  The configuration of the oscillator 24 in FIG. 2 described above is an example, and other circuit configurations may be used. Even in such a case, a burst wave without carrier leakage as described above can be obtained by opening and closing the feedback loop for oscillation by the pulse signal Pa, or turning on and off the power supply (current source, etc.) of the oscillation circuit by the pulse signal Pa. be able to.

  A signal Pb output from the oscillator 24 is amplified by a power amplifier 25 formed of a power FET or the like, and is supplied to the transmission antenna 22 via the BRF 26. Therefore, the short pulse wave Pt described above is radiated from the transmitting antenna 22 to the space 1 to be searched. The gain of the power amplifier 25 can be varied by the control unit 50.

  A power source Bt for the pulse generator 23, the oscillator 24 and the power amplifier 25 of the transmission unit 21 is supplied via a power switch 27. The power switch 27 is ON / OFF controlled by the control unit 50.

  On the other hand, the receiving unit 30 receives the reflected wave Pr from the object 1a in the space 1 via the receiving antenna 31, amplifies the received signal R by an LNA (low noise amplifier) 32, and then a band having a bandwidth of about 2 GHz. The band is limited by the pass filter (BPF) 41, and the reflected signal R ′ whose band is limited is detected by the detection circuit 33. The gain of the LNA 32 can be varied by the control unit 50.

  The detection circuit 33 includes a branch circuit 34 that branches the reflected signal R ′ output from the BPF 41 in phase (0 °), a linear multiplier 35 that linearly multiplies the reflected signals branched in phase, and a linear multiplier 35. And a low-pass filter (LPF) 36 that extracts a baseband component W from the output signal.

  There are several methods for the linear multiplier 35, such as using a double balanced mixer, but a method using a Gilbert mixer can be considered as one that operates at high speed.

  As shown in FIG. 4, the Gilbert mixer includes three sets of differential amplifiers 35a, 35b, and 35c. The first signal V1 is differentially input to the differential amplifier 35a, and two sets of differential amplifiers 35a are connected to the load side. When the second signal V2 is differentially input to the differential amplifiers 35b and 35c, only the signal component equal to the product of the first signal V1 and the second signal V2 is output from the load resistors R3 and R4.

  When, for example, a sinusoidal signal S (t) as shown in FIG. 5A is input in a burst in the same phase to the linear multiplier 35 having this configuration, the output signal is as shown in FIG. 5B. The waveform is obtained by squaring the input signal S (t), and its envelope (baseband) W is proportional to the power of the input signal S (t).

  As described above, the linear multiplier 35 composed of a plurality of differential amplifiers can be configured to be extremely small by the MMIC, and further, since it is not necessary to supply a local signal, power consumption can be reduced.

  The baseband signal W obtained by the detection circuit 33 is input to the sample and hold circuit 37. The sample hold circuit 37 has a configuration in which a baseband signal W is input to an integrating circuit including a resistor 37a and a capacitor 37b via a switch 37c, as shown in FIG. When the pulse signal Pc is high level (or may be low level), the switch 37c is closed to integrate the baseband signal W. When the pulse signal Pc becomes low level, the switch 37c is opened to hold the integration result.

  Here, the sampling period of the sample hold circuit 37, that is, the period of the pulse signal Pc is described as being equal to the period of the trigger signal G. However, the sampling period is an integral multiple of the period Tg of the trigger signal G. May be.

  The pulse generator 38 receives a signal G ′ (which may be the trigger signal G itself) synchronized with the trigger signal G, delays the signal G by a time Td designated by the control unit 50, and the control unit A pulse signal Pc having a width Tc designated by 50 is generated and output to the sample and hold circuit 37.

  The signal H integrated and held by the sample-and-hold circuit 37 is converted into a digital value by the A / D converter 39 immediately after the holding and input to the signal processing unit 45.

  The power supply Br for the LNA 32, the detection circuit 33, the sample hold circuit 37, and the pulse generator 38 of the reception unit 30 is supplied via the power switch 40. The power switch 40 is on / off controlled by the control unit 50.

  The signal processing unit 45 analyzes the object 1a existing in the space 1 based on the signal H obtained by the receiving unit 30, and the analysis result is output by an output device (for example, a display or a sound generator) not shown. Notify the control unit 50 of information necessary for control.

  The control unit 50 performs various controls on the transmission unit 21 and the reception unit 30 according to a schedule determined in advance for the short pulse radar 20 or according to the processing result of the signal processing unit 45.

  Further, the control unit 50 stops the power supply to the transmission unit 21 and transmits the transmission within a period from when the transmission unit 21 radiates the short pulse wave to the space 1 until the next short pulse wave is emitted. In the period from when the unit 21 radiates the short pulse wave to the space until the next short pulse wave is emitted, and during the period excluding the period for receiving the reflected wave of the emitted short pulse wave, The power supply to the unit 30 is stopped to reduce power consumption.

  Note that when the transmitter 21 and the receiver 30 have a circuit that requires supply of bias power before the main power supplies Bt and Br, the power consumption of the bias power is small (for example, the gate bias of the FET). In the case where it is not necessary to pass a current), the bias power source may be always supplied. When the power consumption of the bias power source is large, a switch for supplying the bias power source is separately provided, and the main power source is supplied after the bias power source is supplied.

Next, an operation example of the short pulse radar 20 will be described.
At the initial stage of exploration, the control unit 50 turns on the power switches 27 and 40 at a constant cycle Tg (for example, 10 μs) every predetermined time Tw (for example, 400 ns) as shown in FIG. Power is supplied to the receiving unit 30 (here, it is described that the control of the bias power source is unnecessary).

  Here, the on time Tw of the power switches 27 and 40 is the time Tw1 (for example, 200 ns) required for stabilizing the voltage of the power source supplied to the transmitting unit 21 and the receiving unit 30 and the longest search distance (for example, 15 m). Is the total time with the time Tw2 (for example, 200 ns) for completing the detection process and the sample hold process for the radio wave that reciprocated in and out.

  Then, at the timing when the time Tw1 has elapsed from the timing when the power switches 27 and 40 are turned on, the gain of the power amplifier 25 is set to a specified value, the gain of the LNA 32 is set to, for example, the maximum, and the trigger signal G having the cycle Tg is set. A pulse signal Pa having a width Tp (for example, 1 ns) as shown in FIG. 7B is input to the oscillator 24 as shown in FIG. 7B, and the carrier 24 sends a carrier signal as shown in FIG. A short pulse wave Pt having a frequency Fc (for example, 26 GHz) and a width Tp is radiated to the space 1.

  The short pulse wave Pt radiated from the transmitter 21 is reflected by the object 1a existing in the space 1, and the reflected wave Pr is detected from the transmission timing of each short pulse wave Pt as shown in FIG. The signal is received by the receiving antenna 31 with a delay of time Tx corresponding to the round trip distance to the object 1a.

  In the receiving unit 30, the received signal R is amplified by the LNA 32, then the band power is limited by the BPF 41 to reduce noise power, and the output signal R ′ is detected by the linear multiplier 35 and the low-pass filter 36 of the detection circuit 33. Then, the baseband component W as shown in FIG. 7E is detected.

  On the other hand, a pulse signal Pc having a width Tc (for example, 1 ns) is delayed in the sample hold circuit 37 by Td, 2Td, 3Td,... From each transmission timing of the short pulse wave Pt, as shown in FIG. Entered. Here, the case where the delay time Td is equal to the width of the pulse Pc will be described.

  As described above, if the distance to the far end of the space 1 to be searched is within 15 m, the time required for the radio wave to travel back and forth through the 15 m is approximately 100 ns, so that the transmission timing of the short pulse wave Pt reaches 100 Td at the maximum. By delaying, the reflected wave from within 15 m can be covered.

  Note that a reflected wave from a predetermined exploration distance arrives and is detected for detection until the time Tw2 elapses from each transmission timing of the short pulse wave Pt, and Tg−Tw2 after the time Tw2 elapses. Until the time elapses, the power supply to the transmission unit 21 and the reception unit 30 is stopped as shown in FIG.

  Here, if the time Tg is 10 μs and the time Tw is 400 ns as described above, the ratio Tw / Tg of the power supply time to the pulse transmission cycle Tg is 0.04 (4 percent), and the power is always supplied. Compared to the case, 96% of power can be saved by simple calculation.

  As shown in FIG. 7, since the first to third pulse signals Pc do not overlap with the baseband component W, the sample-and-hold circuit 37 integrates only the noise component. The result and the retained value are almost zero.

  When the fourth and fifth pulse signals Pc overlap with the baseband component W, the baseband signal W is integrated within the high level period of the pulse signal Pc as shown in FIG. H1 and H2 are held and converted into digital values as shown in (h) of FIG.

  The signal processing unit 45 detects the distance to the object 1a, the size of the object, and the like based on the hold values H1 and H2.

  For example, when a holding value H of a predetermined level or higher is input, the distance to the object is detected depending on how many times the sampling is obtained. In addition, when the holding value H of a predetermined level or higher continues, the size of the object is detected based on the number of consecutive times.

  This detection information is notified to the control unit 50. For example, when the notified detection information indicates that the distance to the object is close and the intensity of the reflected wave Pr is large, the control unit 50 determines that the input level of the detection circuit 33 is the linear operation range of the linear multiplier 35. The gain of the LNA 32 is lowered so as to be within, and the gain of the power amplifier 25 is also lowered if necessary, so that the baseband component W can be detected more accurately in the next search.

  Further, when it is necessary to analyze a weak reflected wave from the vicinity of the far end of the exploration space 1, the gain of the power amplifier 25 is increased.

  Further, the integration time Tc of the sample and hold circuit 37 is also appropriately changed according to the state of the space 1 to be searched and the size of the object 1 to obtain necessary search information.

  Here, power is supplied to the transmission unit 21 and the reception unit 30 for a total time of a power supply voltage stabilization time Tw1 and a time Tw2 required to receive a reflected wave for a predetermined search distance. As shown in FIG. 8A, power is supplied to the transmission unit 21 for the total time of the stabilization time Tw1 and the width Tp of the pulse signal Pa in FIG. As shown in FIG. 8B, if the power is supplied only for the total time of the stable time Tw1 and the time Tw2 necessary for receiving and detecting the reflected wave for the predetermined search distance, the power consumption can be further reduced. Can do.

  Further, although it is necessary to vary the power supply time, the power consumption can be further reduced by stopping the power supply to the receiving unit 30 immediately after the sample hold.

  Further, depending on the situation, the power supply to the transmission unit 21 and the reception unit 30 may be stopped for a time longer than the period Tg to further save power.

  For example, when the holding output H of a predetermined level or more cannot be obtained by 100 short pulse waves Pt, the signal processing unit 45 determines that there is no obstructing object within the search range, and sends this to the control unit 50. Notice. Receiving this notification, the control unit 50 stops supplying power to the transmission unit 21 and the reception unit 30 for a certain period (for example, 1 ms), and repeats the above operation again after the certain time has elapsed.

  By such power supply control, the power consumption can be extremely reduced, the battery can be driven for a long time, and portable use is possible.

  In the short pulse radar 20 of this embodiment, since a short pulse wave is generated and detected without using a local signal, there is no power consumption by the local signal generator or the local signal amplifier, and the configuration is high. In this respect, it is possible to save power, and further, it is possible to reduce the size without requiring local signal routing or shielding.

  In the case of an on-vehicle radar, the ambient temperature range in which the radar is installed is as wide as −50 ° C. to 80 ° C. Due to the temperature change of the characteristics of the devices constituting the transmitter 21 and the receiver 30, It is expected that the characteristics will change greatly.

  In such a case, the short pulse radar 20 is provided with a temperature sensor (not shown), and the control unit 50 transmits the transmission unit 21 or the reception unit 30 (both in accordance with the temperature detected by the temperature sensor). However, the temperature of the devices constituting the transmission unit 21 and the reception unit 30 is not significantly changed, and the characteristics of the entire radar may be stabilized.

  That is, the lower the ambient temperature detected by the temperature sensor, the shorter the power stop period of the transmitter 21 and the receiver 30 and increase the power consumption of the device. Conversely, the higher the ambient temperature, the longer the power stop period. The device power consumption is reduced and the device temperature is kept constant.

  In addition, among the devices of the transmission unit 21 or the reception unit 30, a device having a particularly large characteristic variation due to a temperature change is provided with a temperature sensor in the vicinity thereof, so that the temperature detected by the temperature sensor is constant. The length of the power supply stop period may be variably controlled.

The figure which shows the structure of embodiment of this invention The figure which shows the structural example of the principal part of embodiment. Operation explanatory diagram of the main part of the embodiment The figure which shows the structural example of the principal part of embodiment. Operation explanatory diagram of the main part of the embodiment The figure which shows the characteristic of the principal part of embodiment The figure for demonstrating operation | movement of embodiment The figure for demonstrating another operation example of embodiment Basic configuration of pulse radar

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Space, 1a ... Object, 20 ... Short pulse radar, 21 ... Transmitter, 22 ... Transmitting antenna, 23 ... Pulse generator, 24 ... Oscillator, 25 ... Power amplifier, 26 ... Band rejection filter (BRF), 27 …… Power switch, 30 …… Receiver, 31 …… Receiving antenna, 32 …… LNA, 33 …… Detector circuit, 34 …… Branch circuit, 35 …… Linear multiplier, 36... Low pass filter (LPF) 37. Sample hold circuit 38. Pulse generator 39 39 A / D converter 40. Power switch 45. Signal processor 41. Band pass filter (BPF), 50 ...... Control unit

Claims (8)

Based on a transmission unit (21) that repeatedly radiates a short pulse wave into space, a reception unit (30) that receives and detects a reflected wave of the short pulse wave radiated into the space, and a detection output of the reception unit And a signal processing unit (45) that performs an analysis process on an object existing in the space, and a control unit (50) that controls the transmission unit and the reception unit based on an analysis result of the signal processing unit. In pulse radar,
The controller is
A short pulse radar characterized in that the power supply to the transmission unit is stopped within a period from when the transmission unit emits a short pulse wave to space until the next short pulse wave is emitted. The controller is
Within a period from when the transmitting unit emits a short pulse wave to space until it emits the next short pulse wave, and during a period excluding a period for receiving a reflected wave of the emitted short pulse wave, 2. The short pulse radar according to claim 1, wherein power supply to the receiving unit is stopped. The controller is
The power supply is stopped after the short pulse wave is radiated to the space after a predetermined time has elapsed from the start of the supply of power to the transmission unit. 2. The short pulse radar according to 2. The controller is
The receiving unit starts supplying power to the receiving unit in accordance with the start of power supply to the transmitting unit, and after the period for receiving the reflected wave of the short pulse wave radiated into the space by the transmitting unit has elapsed. 4. The short pulse radar according to claim 3, wherein the power supply to the power supply is stopped. The controller is
5. The short pulse radar according to claim 3, wherein bias power is supplied before power is supplied to the transmitter or receiver. The controller is
The control unit according to claim 1 or 2, wherein when the analysis result indicating that no object is present in the space is received from the signal processing unit, the transmission interval of the short pulse wave by the transmission unit is increased. The short pulse radar according to claim 2 or claim 3 or claim 4 or claim 5. Have a temperature sensor,
The controller is
The short pulse radar according to claim 1, wherein a stop period of power supply to the transmission unit is changed according to a temperature detected by the temperature sensor. Have a temperature sensor,
The controller is
3. The short pulse radar according to claim 2, wherein a stop period of power supply to the receiving unit is changed according to the temperature detected by the temperature sensor.

Images