JP4045260B2 - Pulse generation circuit - Google Patents

Description

  The present invention relates to a pulse generation circuit used for, for example, an in-vehicle radar.

  As a conventional pulse radar device, there is one proposed in Patent Document 1. As shown in FIG. 1 of this document, this apparatus periodically outputs a pulsed signal by a sending unit, continuously receives reflected pulses from a target by a receiving unit, and 2 by a binarizing unit. Convert to value. The sampling means samples the binarized signal at a certain sampling point or points after the sending timing of the sending means to obtain a sampling value of 0 or 1, corresponding to each point of the sampling point. Is given to the adding means. Therefore, the adding means adds 0 or 1 sampling values for each predetermined number of times the signal is sent by the sending means. When the addition process for the predetermined number of times is completed, the determination unit compares the normalized addition value obtained by dividing the addition value for each addition unit by the number of additions with a predetermined threshold, and based on the magnitude, from the external target It is comprised from what determines whether the reflection signal of this exists, and determines the presence or absence of an external target based on this.

  However, when transmission / reception isolation is poor and a so-called leaky waveform exists, or when there is a radome, detection of an object existing at a distance of less than 10 m using a conventional apparatus for the following reasons, and It is difficult to measure the distance to the object. That is, in the conventional apparatus, the transmission pulse width is 66.7 ns corresponding to 10 m in terms of distance, and therefore when an object is present at a distance closer than 10 m, a leakage waveform or a reflected wave due to the secondary radome and the object A waveform in which the waveforms of the reflected waves overlap is detected. Therefore, if the threshold is set based on the reception level during non-transmission, so-called noise level, only the rise of the leakage waveform can be detected, and the rise of the reflected wave that is really desired to be detected cannot be detected.

  Conventionally, there has been such a problem, and it has been difficult to detect short distances. However, in recent years, the rules of the FCC Federal Communications Commission in the United States have been revised last year, and in accordance with this, UWB (Ultra Wide Band) in in-vehicle radar Technology can be used.

  The UWB technique can be used, and as a means for detecting a short distance, a method of making the pulse width as short as 350 ps as described in Non-Patent Document 1 has been proposed. However, as described in this document, when the transmission pulse width is shortened to 350 ps, the leakage waveform and the reflected wave waveform overlap only when the distance to the object is about 5 cm or less. However, the conventional pulse generation circuit for generating a pulse cannot be used by a combination of an oscillation element such as a monostable multivibrator or a crystal resonator and a logic IC.

  Here, UWB is a communication method in which modulation is performed using extremely short pulses of several hundred psec to several nsec. Since a high frequency (ultra short) pulse is used, it has an extremely wide frequency bandwidth and has a wide spectrum. Has a low transmission power because it spreads and does not affect other devices.

  Therefore, in the conventional pulse generation circuit, the pulse generation circuit composed of an easily available silicon-based semiconductor is a high-frequency (very short) pulse, that is, a pulse of 2 nsec or less (frequency of 100 MHz band or more) from pulse rising to falling. Therefore, a semiconductor device for high frequency, that is, a semiconductor having a high electron mobility using an element such as gallium arsenide (hereinafter referred to as GaAs) has to be used.

  In addition, when a high frequency pulse is generated in a semiconductor device having a silicon (hereinafter referred to as Si) element symbol generally used at low frequencies, a commercially available TTL output (voltage of 0V to 5V) is used. Output) logic ICs are not capable of high-frequency pulse operation, and output such as ECL (-0.8 V to -1.8 V voltage output), PECL (3.2 V to 4.2 V voltage output), etc. Semiconductors with different voltage levels (interfaces) must be used.

JP-A-7-72237 W. Weidmann and D. Steinbuch, "HighResolution Radar for Short Range Automotive Applications", 28th European Microwave Conference Amsterdam, 1998

  When semiconductors with element symbols such as GaAs are used, they are not only expensive but also difficult to handle themselves, and environmental performance (especially surge) may be severe, especially for automotive applications, and the availability of semiconductor elements is poor. In addition, there is a problem that reliability is low and mass production becomes difficult.

  In addition, when generating a high-frequency pulse in a semiconductor device having a Si-based element symbol that is generally used at a low frequency, an ECL or PECL output device is used. In addition to the price of, there was a problem that the price of parts added to it would be high.

  In addition, devices such as ECL and PECL have a problem that current consumption is large, the amount of heat generated by the device increases, and the environmental performance of the device further deteriorates.

  In addition, when it comes to Si-based devices capable of high-frequency pulse operation, there are almost no devices that are binarized, such as C-MOS logic ICs and comparators. ) Existed and it was difficult to obtain.

  The present invention is a radar pulse generation circuit designed to solve the above-described problems, and is inexpensive and can be easily configured without being so difficult in terms of availability and reliability, for example, for in-vehicle use.

Pulse generating circuit according to the present invention includes a DC power supply, a capacitor connected through the charging resistor to the DC power source, a discharge resistor for discharging a charging energy of the capacitor, is inserted between the capacitor and the discharge resistor Rutotomoni A single-pole double-throw semiconductor switch controlled by a control signal to switch the capacitor to either the charging resistor side or the discharging resistor side ; and an amplifier connected to an output terminal of the discharging resistor, the semiconductor switch The pulse generated at the output terminal of the discharge resistor when discharging from the capacitor to the discharge resistor is taken out through the amplifier.

  The pulse generation circuit of the present invention can generate a high-frequency pulse only by charging and discharging a capacitor and a silicon-based low-frequency semiconductor switch without using a semiconductor element such as GaAs having a high electron mobility.

Embodiment 1 FIG.
1 is a pulse generation circuit according to Embodiment 1 of the present invention. A pulse generation circuit according to the present invention includes a DC power supply 101 for applying a desired voltage, a charging resistor 102 connected to the DC power supply 101, a capacitor 103 for generating a charge / discharge waveform connected to the charging resistor 102, The semiconductor switch 105 has one end connected to the capacitor 103, a discharge resistor 104 connected to the other end of the semiconductor switch 105, and an amplifier 106 connected to the discharge resistor 104.

  The semiconductor switch 105 is, for example, a silicon-based single-pole single-throw switch whose opening and closing is controlled by a pulse signal applied to the control terminal a. The amplifier 106 is an amplifier for performing amplification, impedance conversion, or output voltage limit of a pulse applied to the input terminal.

  Next, the operation will be described. The capacitor 103 is charged and discharged in synchronization with the control pulse of FIG. 2A applied to the control terminal a of the semiconductor switch 105 (see FIG. 2B). When the semiconductor switch 105 is turned on, the current discharged from the charging capacitor 103 through the semiconductor switch 105 to the discharging resistor 104 is an output pulse determined by the rise time of the semiconductor switch 105 and the time constant of the charging capacitor 103 and the discharging resistor 104. (See FIG. 2C) is output as a high-frequency pulse through the output terminal c of the amplifier 106.

Here, the width Pw of the high-frequency pulse obtained from the amplifier 106 is composed of a rising period Thu and a falling Thd. As shown in FIG. 3, the pulse rising Thu is determined by the rising speed of the semiconductor switch 105, and the pulse falling Thd is a resistance component such as the resistance of the semiconductor switch 105 and the resistance of the wiring pattern Ron, and the resistance of the discharge resistor 104. Assuming that the value R2 and the charge / discharge capacitor 103 are capacitance C, ideally the following is determined.

Pw = Thu + Thd
Thu = Switching speed of semiconductor switch
Thd ≒ 5 × (R2 + Ron) × C

  Even if the semiconductor switch 105 is turned on and the energy of the capacitor 103 is completely discharged, the output voltage level is determined by the ratio of the charging resistor 102 and the discharging resistor 104, so that the semiconductor switch does not return from on to off immediately after discharging. However, no unnecessary voltage is generated.

Here, the unnecessary output voltage Vout output from the amplifier 106 after discharging is that the power supply voltage is Vcc, the charging resistor 102 is R1, and the discharging resistor 104 is R2.
Vout = Vcc × R2 / (R1 + R2)
Therefore, if R1 >> R2, the output voltage Vout after discharge becomes small, and an unnecessary voltage level is not generated as the output Vout at high speed without turning off the semiconductor switch.

  Further, the amplifier 106 is a high-frequency operational amplifier (an OP follower constitutes an emitter follower), and can generate pulses even without the amplifier 106, but impedance matching to a device or the like connected in the subsequent stage, or Since the pulse output voltage is limited to the power supply voltage of the OP amplifier, it is preferable to input it for the purpose of protecting the subsequent stage elements.

Embodiment 2. FIG.
FIG. 4 shows Embodiment 2 of the present invention, and is the same as FIG. 1 except for the semiconductor switch 405. The same elements as those in FIG. The semiconductor switch 405 is a single-pole double-throw silicon low-frequency switch, and the terminal of the capacitor 103 is applied to the terminal a on the charging resistor 102 side and the discharging resistor 104 side (see FIG. 5A). It is configured to switch synchronously.

  Next, the operation will be described. While the capacitor 103 is connected to the charging resistor 102 side, the capacitor 103 charged through the charging resistor 102 is disconnected from the charging resistor 102 side by switching the semiconductor switch 405 and connected to the discharging resistor 104 side. And the resulting pulse is taken out of the amplifier 106. FIG. 5 is a sequence showing this state. 5A is a control pulse applied to the control terminal a of the semiconductor switch 405, FIG. 5B is a charge / discharge voltage waveform of the capacitor 103, and FIG. 5C is a pulse waveform taken out from the output terminal c of the amplifier 106.

  In this embodiment, by using a single-pole double-throw switch as the semiconductor switch 405, the resistance value of the charging resistor 102 can be further reduced, the energy charging time to the capacitor 103 is shortened, and the pulse transmission cycle Can be expedited. Further, the unnecessary voltage after the energy discharge generated in the configuration of the first embodiment is eliminated, and the resistance value R1 of the charging resistor 102 and the resistance value R2 of the discharging resistor 104 can be freely set.

  The present invention can be used as a pulse generation circuit such as an in-vehicle radar.

1 is a circuit diagram showing a pulse generation circuit according to Embodiment 1 of the present invention. FIG. It is a wave form diagram explaining the operation | movement of FIG. It is a wave form diagram which shows the pulse formed with the circuit of FIG. It is a circuit diagram which shows the pulse generation circuit which concerns on Embodiment 2 of this invention. It is a wave form diagram explaining the operation | movement of FIG.

Explanation of symbols

101 DC power supply, 102 charging resistance,
103 capacitor, 104 discharge resistance,
105 semiconductor switch (single pole single throw type), 106 amplifier,
405 Semiconductor switch (single pole double throw type).

Claims (2)

DC power supply, a capacitor connected through a charging resistor to the DC power source, a discharge resistor for discharging a charging energy of the capacitor is controlled by the inserted Rutotomoni control signals between the capacitor and the discharge resistor, the said capacitor A single-pole double-throw type semiconductor switch that switches between the charging resistor side and the discharging resistor side , and an amplifier connected to the output terminal of the discharging resistor, and discharging from the capacitor to the discharging resistor through the semiconductor switch A pulse generation circuit characterized in that a pulse generated at the output terminal of the discharge resistor is extracted through the amplifier. 2. The pulse generation circuit according to claim 1 , wherein the semiconductor switch is a silicon-based low frequency switch .

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