JP2006071523A - Impulse signal generating circuit loaded on uwb radar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an impulse signal generating circuit loaded on a UWB radar for outputting an impulse signal with a ringing prevented from occurring. <P>SOLUTION: This impulse signal generating circuit is equipped with: a pulse signal generating circuit 1; a producing circuit 5 for branching a pulse signal transmitted from the generating circuit to a high-frequency transmission path 51, and re-coupling the pulse signal whose amplitude is reversed and whose time is delayed by the transmission path 51, to the pulse signal transmitted from the generating circuit 1, thereby producing the impulse signal; and a resistance 7 for preventing the ringing of the impulse signal by relatively reducing the proportion of a parasitic component to the total impedance of the generating circuit 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an impulse signal generation circuit mounted on a UWB radar that measures the distance to an object to be measured using an impulse signal.

  By transmitting a signal with an ultra-wide band of about several GHz and a very short pulse width with weak power below noise (for example, -41.3 dBm / MHz or less) without using a carrier wave, other wireless communication There is a radio technology called UWB (Ultra Wide Band) that realizes high-speed data transmission without interfering with the system (Non-Patent Document 1). This UWB is used not only for communication, but also for applications such as military radar that specifies the position of an object with high accuracy and human life search in a disaster. Previously, this UWB was used outside the consumer sector as described above, but on February 14, 2002, the US Federal Communications Commission (FCC) approved the use of UWB in the consumer sector. Therefore, the high-speed data transmission and the radar using UWB (hereinafter referred to as “UWB radar”) are expected to be diverted to the consumer field.

"Nikkei Electronics" March 11, 2002 issue

  The UWB radar as described above transmits a signal having a very short pulse width (hereinafter referred to as “impulse signal”) to the object to be measured, and receives and receives the impulse signal reflected by the object to be measured. The time difference between the impulse signal and the transmitted impulse signal is detected, and the distance from the antenna to the object to be measured is measured based on the detected time difference. In UWB radar, in order to improve the measurement sensitivity, the impulse signal described above is transmitted at a constant cycle, and the impulse signals reflected by the object to be measured and received at a fixed cycle are synchronized and cumulatively added. As a result, the measurement sensitivity is improved.

  Such an UWB radar is equipped with an impulse signal generation circuit for generating an impulse signal as described above. In the impulse signal generated from the impulse signal generation circuit, ringing in which the impulse signal vibrates positively and negatively occurs due to parasitic components included in the components constituting the impulse signal generation circuit. Thus, if there is ringing in the impulse signal output from the impulse signal generation circuit, the S / N ratio of the cumulatively added impulse signal is deteriorated and the measurement sensitivity is deteriorated.

  The present invention has been made with respect to the above problems, and an object thereof is to output an impulse signal in which generation of ringing is suppressed from an impulse signal generation circuit mounted on a UWB radar.

  The configuration of the present invention includes a pulse signal generation circuit that is mounted on a UWB radar and generates a pulse signal at a constant period, and a high-frequency transmission line that is connected to the pulse signal generation circuit and short-circuits the core wire and the ground wire at the end. The pulse signal transmitted from the pulse signal generation circuit is branched to the high frequency transmission path, and the signal whose amplitude is inverted and time is delayed with respect to the pulse transmitted from the pulse signal generation circuit by the high frequency transmission path The generation circuit that generates the impulse signal by recombining with the pulse signal transmitted from the pulse signal generation circuit, and the ratio of the parasitic component that is connected in parallel to the high-frequency transmission path and occupies the entire impedance of the impulse signal generation circuit. And a resistor that suppresses the ringing of the impulse signal by being relatively reduced.

  Also, by making the characteristic impedance of the high-frequency transmission line larger than the signal source resistance of the pulse signal generation circuit, the voltage division ratio of the pulse signal generated from the pulse signal generation circuit is changed, thereby increasing the amplitude of the impulse signal Is desirable.

  Further, the pulse signal generation circuit includes a rectifying element, and the rectifying element causes a current that is transiently output in the reverse direction when the voltage of the pulse signal is applied in the reverse direction to be steep with respect to time. It is desirable to set to 0.

  The rectifying element is preferably a step recovery diode.

  According to the present invention, it is possible to output an impulse signal in which generation of ringing is suppressed from an impulse signal generation circuit mounted on a UWB radar.

  Hereinafter, an impulse signal generation circuit mounted on a UWB radar according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of an impulse signal generation circuit mounted on the UWB radar according to the present embodiment. FIG. 2 is a diagram showing the operation of the impulse signal generation circuit mounted on the UWB radar according to the present embodiment. FIG. 3 is a diagram showing a waveform of an impulse signal output from the impulse signal generation circuit mounted on the UWB radar according to the present embodiment. Hereinafter, the configuration of the impulse signal generation circuit mounted on the UWB radar according to the present embodiment will be described in detail.

  The impulse signal generation circuit mounted on the UWB radar shown in FIG. 1 includes a pulse signal generation circuit 1, a rectifying element 3, an impulse generation circuit 5, and a resistor 7, and outputs an impulse signal having an ultra-wide bandwidth and a very short pulse width Output from. The rectifying element 3 and the resistor 7 are mounted on the same substrate, and the impulse generating circuit 5 is also formed by a high-frequency transmission line such as a microstrip line. The pulse signal generation circuit 1 may be mounted on the substrate described above, or may be mounted on a separate substrate and connected by a transmission line.

  The pulse signal generation circuit 1 includes a pulse signal generation source 11 and a signal source resistor 13. This pulse signal generation source 11 generates a pulse signal that alternately repeats positive and negative voltages, and outputs this. The signal source resistor 13 is a signal source resistor that equivalently indicates the output impedance of the pulse signal generation circuit 1, and the impedance is set to 50Ω.

  The rectifying element 3 includes a diode 31 and is a rectifying element that rectifies the pulse signal generated from the pulse signal generation circuit 1 described above. The diode 31 is a bare chip diode, is mounted on a package such as ceramic, and is connected to an external electrode by wire bonding (or direct bonding) or the like. Here, the parasitic inductances 33-1 and 33-2 are parasitic inductances that equivalently indicate an inductance component by wire bonding or the like that connects the diode 31 and the external electrode described above. The parasitic capacitance 35 is a parasitic capacitance equivalently indicating a capacitance component between two external electrodes. As will be described later, the rectifying element 3 has a relatively long accumulation time in which a reverse current flows transiently when a reverse voltage is applied, and the reverse current is 0 (zero) after the accumulation time has elapsed. It is desirable to use a diode that has a short time to transition (transition time). As such a diode having a short transition time, there is a step recovery diode, which is desirably used as the rectifying element 3.

  The impulse generation circuit 5 includes a high frequency transmission path 51. In the high-frequency transmission line 51, the core wire and the ground wire are short-circuited at the end. The characteristic impedance of the high-frequency transmission line 51 is set to a value higher than that of the signal source resistor 13 of the pulse signal generation circuit 1. This will be described later.

  The resistor 7 is connected to the high-frequency transmission path 51 in parallel. The resistance value of the resistor 7 is set to a value that relatively reduces the proportion of the parasitic inductance and parasitic capacitance (parasitic component) in the entire impedance of the impulse signal generation circuit. The resistance value of the resistor 7 will be described later.

  With the above configuration, the impulse signal generation circuit shown in the present embodiment can suppress the occurrence of ringing of the impulse signal output from the output terminal. Hereinafter, the operation will be described in detail with reference to FIGS.

  As shown in FIG. 2A, the pulse signal generation source 11 generates a pulse signal that alternately repeats positive and negative voltages. The pulse signal generated by the pulse signal generation source 11 is output from the output unit of the pulse signal generation circuit 1. The pulse signal output from the pulse signal generation circuit 1 steadily flows only when a voltage is applied to the rectifying element 3 in the forward direction (positive), and according to this amount of current, the current shown in FIG. A voltage is output as shown. Here, as shown in FIG. 2B, when the pulse signal becomes negative, the rectifying element 3 transiently flows in the reverse direction, and a voltage corresponding to the amount of current is output. As described above, the rectifying element 3 is a diode (step recovery diode) having a short transition time. For this reason, the voltage output in the reverse direction transiently becomes 0 sharply with respect to time after the accumulation time has elapsed. By inputting such a pulse signal output from the rectifying element 3 to the impulse generating circuit 5, it is possible to generate an impulse signal having a very short pulse width. The generation of this impulse signal will be described below.

  As described above, in the impulse generation circuit 5, the high-frequency transmission path 51 is connected in parallel to the input / output unit. For this reason, a pulse signal propagates from the input / output unit of the impulse generation circuit 5 and the branch point of the high-frequency transmission path 51 toward the end of the high-frequency transmission path 51. In addition, since the high-frequency transmission line 51 is short-circuited at the end, the pulse signal propagating through the high-frequency transmission line 51 is inverted in amplitude at the end of the high-frequency transmission line 51 as shown in FIG. reflect. Then, the pulse signal with the inverted amplitude propagates from the end of the high-frequency transmission path 51 in the direction of the branch point between the rectifying element 3 and the high-frequency transmission path 51, and as shown in FIG. 51 is delayed by a round-trip propagation. Thereby, at the branch point of the rectifying element 3 and the high-frequency transmission path 51, the pulse signal and the pulse signal whose amplitude is inverted and time is delayed are recombined. The high-frequency transmission line 51 has, for example, a characteristic impedance of 50Ω and a transmission line delay time of 30 ps.

  Accordingly, as shown in FIG. 2D, the impulse generation circuit 5 cancels the pulse signal because it is inverted and recombined with the same amplitude, and has a pulse with a delay time corresponding to the round-trip propagation through the high-frequency transmission path 51. An impulse signal having a width is generated. The impulse signal generated by the impulse generating circuit 5 passes through a 50Ω transmission path connected to the output terminal and is radiated into the air via an antenna having a radiation resistance of 50Ω. Here, the waveform of the impulse signal output from the output terminal of the impulse generation circuit 5 mounted on the UWB radar is shown in FIG. 3, and the reduction of ringing generated in the impulse signal by the resistor 7 will be described below.

  In FIG. 3, a waveform 101 is a waveform when the resistance 7 is set to ∞Ω (= open state). Similarly, the waveform 103 is a waveform when the resistor 7 is 100Ω, the waveform 105 is a waveform when the resistor 7 is 75Ω, and the waveform 107 is a waveform when the resistor 7 is 50Ω. A waveform 109 is a waveform when the resistance 7 is set to 25Ω. Since the resistor 7 is connected in parallel to the line extending from the signal source resistor 13 to the output terminal, the smaller the resistance value of the resistor 7 occupies the overall impedance of the impulse signal generation circuit mounted on the UWB radar. The proportion of the parasitic component is relatively reduced, and ringing generated in the impulse signal can be reduced as shown in FIG.

  Further, as described above, the impulse signal is generated from the pulse signal output from the pulse signal generation circuit 1, but the pulse width of the pulse signal is different from that of the impulse signal by several tens to several hundreds. For this reason, if there is even a slight jitter in the pulse signal output from the pulse signal generation circuit 1, the impulse signal has a relatively large jitter of several tens to several hundreds times the pulse width of the impulse signal. It becomes. When such a large jitter occurs, if the ringing generated in the impulse signal is large, the S / N ratio is likely to be deteriorated when the received signals as described above are cumulatively added. If the ringing generated in the impulse signal is suppressed as shown, the S / N ratio is hardly deteriorated when cumulative addition is performed.

  On the other hand, as shown in FIG. 3, the smaller the resistance value of the resistor 7, the smaller the amplitude of the impulse signal, and the smaller the measurable distance (measurement range). In order to suppress ringing of the impulse signal and increase the amplitude, in the impulse signal generation circuit mounted on the UWB radar shown in the present embodiment, the characteristic impedance of the high-frequency transmission path 51 is set to the signal source resistance 13 of the pulse signal generation circuit 1. By making it larger, the voltage dividing ratio of the pulse signal generated from the pulse signal generation circuit 1 is changed, thereby increasing the amplitude of the impulse signal. This will be described in detail below.

  The characteristic impedance in the high-frequency transmission line is a function indicating the relationship between the voltage component and current component of the high-frequency signal. Therefore, as the characteristic impedance of the high-frequency transmission path 51 is larger than the signal source resistance 13 of the pulse signal generation circuit 1, the pulse signal output from the pulse signal generation circuit 1 is more applied to the high-frequency transmission path 51. . As an example, when the signal source resistor 13 of the pulse signal generation circuit 1 is 50Ω and the characteristic impedance of the high-frequency transmission line 51 is 50Ω, which is the same as that of the signal source resistor 13 of the pulse signal generation circuit 1, output from the pulse signal generation circuit 1 The pulse signal thus generated is divided into the signal source resistance 13, 50Ω of the high-frequency transmission path 51, and parallel resistance 25Ω consisting of the radiation resistance 50Ω of the antenna connected to the outside of the output terminal, 25 / (50 + 25) = The voltage is divided into 1/3, that is, 1/3. Thus, an impulse signal generated by the divided pulse signal is output from the output terminal.

  Similarly, when the characteristic impedance of the high-frequency transmission line 51 is 100Ω, which is twice that of the signal source resistor 13 of the pulse signal generation circuit 1, the pulse signal output from the pulse signal generation circuit 1 The partial pressure is 100/3 = 33.3Ω in parallel with 100Ω of the high-frequency transmission line 51 and the antenna radiation resistance 50Ω, and is divided into 33.3 / (50 + 33.3) = 4/10. As a result, a larger amplitude is obtained than when the characteristic impedance of the high-frequency transmission line 51 as described above is the same as that of the signal source resistor 13 of the pulse signal generation circuit 1. Thereby, even if the resistor 7 is inserted in order to suppress the ringing of the impulse signal in the subsequent stage, the characteristic impedance of the high-frequency transmission line 51 is made larger than that of the signal source resistor 13 of the pulse signal generation circuit 1, thereby the pulse signal itself. Therefore, an impulse signal having a sufficient amplitude can be supplied to the antenna.

  As described above, the impulse signal generation circuit mounted on the UWB radar according to the present embodiment is connected to the pulse signal generation circuit that generates a pulse signal at a constant period, and the core wire. A high-frequency transmission line that is short-circuited at the end of the ground wire, the pulse signal transmitted from the pulse signal generation circuit is branched to the high-frequency transmission line, and the pulse signal transmitted from the pulse signal generation circuit through the high-frequency transmission line In contrast, an impulse generation circuit that generates an impulse signal by recombining a signal whose amplitude is inverted and time is delayed with a pulse signal transmitted from the pulse signal generation circuit, and an impulse generation circuit connected in parallel to the impulse generation circuit. By reducing the relative proportion of parasitic components in the overall impedance of the signal generation circuit, the impulse signal is reduced. A resistor for suppressing a swinging, has a structure comprising a. As a result, it is possible to realize an impulse signal generation circuit mounted on the UWB radar that suppresses the occurrence of ringing of the output impulse signal.

  Further, as shown in the present embodiment, by making the characteristic impedance of the high-frequency transmission line larger than the signal source resistance of the pulse signal generation circuit, the voltage signal division ratio of the pulse signal generated from the pulse signal generation circuit is changed, and this As a result, the amplitude of the impulse signal can be increased. Further, the pulse signal generation circuit includes a rectifying element, and the rectifying element causes a current that is transiently output in the reverse direction when the voltage of the pulse signal is applied in the reverse direction to be steep with respect to time. By setting to 0, it is possible to generate an impulse signal having a shorter pulse width.

  In the present embodiment, a microstrip line is used as the high-frequency transmission line, but it goes without saying that a similar effect can be obtained even with an inductor such as a coil, and this does not depart from the spirit of the present application.

It is a circuit diagram which shows the structure of the impulse signal generation circuit mounted in the UWB radar which concerns on this embodiment. It is a figure which shows operation | movement of the impulse signal generation circuit mounted in the UWB radar which concerns on this embodiment. It is a figure which shows the impulse signal output from the impulse signal generation circuit mounted in the UWB radar which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse signal generation circuit, 3 Rectifier element, 5 Impulse generation circuit, 7 Resistance, 11 Pulse signal generation source, 13 Signal source resistance, 31 Diode, 33-1, 33-2 Parasitic inductance, 35 Parasitic capacitance, 51 High frequency transmission line .

Claims (4)

Mounted on UWB radar,
A pulse signal generation circuit for generating a pulse signal at a constant period;
Connected to this pulse signal generation circuit, has a high-frequency transmission line with the core wire and ground line short-circuited at the end, branches the pulse signal transmitted from the pulse signal generation circuit to the high-frequency transmission line, and the pulse signal is transmitted by the high-frequency transmission line A generation circuit that generates an impulse signal by recombining a signal whose amplitude is inverted and time delayed with respect to the pulse transmitted from the generation circuit and the pulse signal transmitted from the pulse signal generation circuit;
A resistor that is connected in parallel to the high-frequency transmission line and relatively reduces the proportion of parasitic components in the overall impedance of the impulse signal generation circuit, thereby suppressing the ringing of the impulse signal,
An impulse signal generation circuit mounted on a UWB radar. An impulse signal generation circuit mounted on the UWB radar according to claim 1,
The characteristic impedance of the high-frequency transmission line is made larger than the signal source resistance of the pulse signal generation circuit, thereby changing the voltage division ratio of the pulse signal generated from the pulse signal generation circuit, thereby increasing the amplitude of the impulse signal. An impulse signal generation circuit mounted on the UWB radar. An impulse signal generation circuit mounted on the UWB radar according to claim 1 or 2,
The pulse signal generation circuit includes a rectifying element,
The rectifying element is mounted on a UWB radar characterized in that when a voltage of a pulse signal is applied in the reverse direction, the current that is transiently output in the reverse direction is abruptly zero with respect to time. Impulse signal generation circuit. An impulse signal generation circuit mounted on the UWB radar according to claim 3,
The rectifying element is a step recovery diode, an impulse signal generating circuit mounted on a UWB radar.

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