JP2012237712A - Vehicle monitoring method and monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a device to monitor around a vehicle using a novel principle.SOLUTION: A vehicle monitoring device comprises: a transmission device which excites a body of a vehicle with an excitation signal; and a receiving device which receives an electromagnetic wave in proximity to the body of the vehicle. The receiving device has: a demodulator 30; a target frequency setting resistor; a target phase setting resistor; a pulse oscillator which outputs a reference signal with frequency as well as a phase coinciding with target frequency as well as a target phase; a phase comparison device 32 which outputs a phase difference signal indicating a phase difference between the reference signal and a transmission monitoring signal; a frequency control device which controls the target frequency of the pulse oscillator by obtaining the phase difference between the reference signal and the transmission monitoring signal from a temporal change in the phase difference signal; and a phase control device which controls the target phase of the pulse oscillator on the basis of the phase difference indicated by the phase difference signal. The vehicle monitoring device detects the target phase at different times, determines whether a variation is equal to or larger than a predetermined value and issues a warning that abnormality occurs around the vehicle when determining that the variable is equal to or larger than the predetermined value.

Description

  The present invention relates to a monitoring method and a monitoring apparatus for monitoring environmental changes around a vehicle. For example, the present invention relates to a method and apparatus for preventing theft of a vehicle by detecting the approach of a person to the vehicle, the opening of a door, or the like.

Japanese Patent Laid-Open No. 2004-26883 discloses a reception device that detects the level of radio waves in a house by using the fact that radio waves radiated from a broadcasting station are always invading the room. An intrusion detection system for detecting the opening of a house door and the entry of an outsider is disclosed.
Further, in Patent Document 2, for each compartment by the vehicle body, an evanescent wave is excited in the compartmented body, and this evanescent set wave is not radiated and propagated to localize inside or around the vehicle. It is disclosed that communication is performed only within a space.
Further, Patent Document 3 receives an electromagnetic wave when the electromagnetic wave environment is stable, obtains a reference reception vector composed of an amplitude and a phase of the reception signal by an average thereof, and thereafter, at regular time intervals. It is disclosed that when an electromagnetic wave is received and the received vector changes by a predetermined amount with respect to the reference received vector, it is determined that the user has entered the environment.
Japanese Patent Application Laid-Open No. H10-260260 discloses that a change in a reflection delay profile of a pulse signal in a multipath environment is detected to detect entry into an electromagnetic wave environment.
Patent Document 5 discloses detecting intrusion in an electromagnetic wave environment by obtaining phase correlations of a plurality of received signals in a multipath environment.
In addition, various systems are known as antitheft devices for vehicles.

Japanese Patent No. 4528946 Special table 2005-528848 JP 2001-229474 A JP 2003-185735 A JP-A-5-232213

In general, a theft prevention device for a vehicle detects vibrations and sound waves related to the vehicle or detects opening of a door. However, when an outsider approaches the vehicle, the vehicle may not be vibrated or the glass may not be broken. In this case, it is difficult to detect the approach or theft of the vehicle.
The present invention uses an unprecedented principle. SUMMARY OF THE INVENTION An object of the present invention is to provide a monitoring method and a monitoring apparatus using a novel principle capable of performing simpler and more accurate detection in a method and apparatus for monitoring the periphery of a vehicle.

The first aspect of the present invention is a monitoring method for monitoring the periphery of a vehicle, wherein the body of the vehicle is excited by an electromagnetic wave generated by a monitoring signal output from the transmission device, thereby forming a multipath of the electromagnetic wave between the transmission device and the reception device. In the vehicle monitoring method, the phase of the monitoring signal received by the receiving device is detected, and when the phase changes, an alarm is given that an abnormality has occurred around the vehicle.
In the present invention, the receiving device may be installed on the outer surface of the body, and excitation current of the body by the transmitting device may be supplied directly to the vehicle body. In this case, the transmission device may be provided inside the vehicle or attached to the outer surface of the body.
The receiving device may be installed on the outer surface of the body, and the vehicle body may be excited by the transmitting device using electromagnetic waves radiated from an antenna provided in the interior space of the vehicle. That is, the vehicle body is indirectly excited by electromagnetic waves radiated from the antenna inside the vehicle.

  The excitation signal that generates the electromagnetic wave to be excited may be a single-frequency sine wave or a baseband signal such as a sine wave, a square wave, a pulse, or a sawtooth wave that is modulated on a carrier wave. The supervisory signal shall mean a single frequency sine wave if not modulated and a baseband signal if modulated. When the baseband signal is a sine wave of a single frequency and the carrier wave is amplitude-modulated with this baseband signal and one sideband is extracted, the electromagnetic wave used for excitation is the baseband signal. This is a simple frequency conversion, but such frequency conversion is also modulation. Therefore, a single frequency sine wave having a frequency lower than that of the carrier wave in this case is also used as the monitoring signal. Further, in the case of modulation, the type of modulation is not limited, and both side band waves and single side band waves may be used as long as they are amplitude modulation. Further, phase modulation or frequency modulation may be used. The baseband monitoring signal includes a rectangular wave having the same period of 0 level and 1 level, a pulse having different periods of 0 level and 1 level, and a code string. In short, it is sufficient if the signal rises or falls sharply. The frequency of the monitoring signal is arbitrary as long as the change in the environment of the vehicle can be detected as a phase change. Of course, when the electromagnetic wave to be excited is a modulated signal of the carrier wave by the monitoring signal, the frequency of the monitoring signal is lower than the frequency of the carrier wave.

  The present invention excites the vehicle body to form a multipath environment in which the vehicle body is interposed between the transmission device and the reception device, and the time variation of the phase of the monitoring signal is determined in the reception device. It is characterized by detecting. If the environment in which the vehicle is placed does not change, the phase of the monitoring signal detected by the receiving device does not change even in a multipath environment. In this state, if a person approaches the vehicle, if a person touches the body, or opens the door, the multipath environment will change, and the phase of the monitoring signal received by the receiver will be temporally changed. Will change. By detecting this change, the surroundings of the vehicle can be monitored. Excitation of the vehicle body by electromagnetic waves can be performed directly or indirectly. Provide a transmitting antenna in the interior space of the vehicle to indirectly excite the body with electromagnetic waves, or install a transmitting device at a position where the body can be directly excited (such as the outer surface of the vehicle body), and attach a receiving device to the outer surface of the body Thus, it is possible to detect a change in the phase of the monitoring signal in a multipath environment. The receiving device may include a speaker that outputs an alarm sound when a change in the phase of the monitoring signal is detected and an environmental change such as the approach of a person's vehicle is detected, or at a position away from the vehicle. An alarm signal may be transmitted to a receiver possessed by the owner of the vehicle present to inform the owner of the approach of the person.

In addition, a return device that receives a monitoring signal by electromagnetic waves and transmits a monitoring signal converted in frequency is installed on the outer surface of the body, and the receiving device monitors the frequency converted from the returning device. A signal may be received.
In this case, the receiving device is usually provided inside the vehicle together with the transmitting device. The reply device receives the monitoring signal, converts it to a different frequency, and transmits it to the receiving device. Therefore, since the paths of the transmission device, the reply device, and the reception device are in a multipath environment, more accurate monitoring is possible. Also in this case, the transmission / reception device may be provided on the outer surface of the body. In this case, the transmission / reception device and the return device transmit / receive electromagnetic waves that excite the body.

According to a second aspect of the present invention, there is provided a monitoring device for monitoring the periphery of a vehicle, wherein a multipath of electromagnetic waves with the vehicle body interposed is formed between the transmission device for exciting the vehicle body with electromagnetic waves generated by a monitoring signal and the transmission device. And a receiving device that outputs a warning that an abnormality has occurred around the vehicle when the monitoring signal is received and the phase of the monitoring signal changes. Monitoring device.
The present invention is an apparatus invention corresponding to the above-described method invention.
In the present invention, the receiving device is installed on the outer surface of the body, and the body may be excited by the transmitting device by supplying an excitation current directly to the body of the vehicle.
The receiving device may be installed on the outer surface of the body, and the transmitting device may be provided in an interior space of the vehicle and may have an antenna that radiates electromagnetic waves that excite the vehicle body. That is, the vehicle body is excited by the electromagnetic wave radiated from the antenna, and a multipath environment is formed by the body.
What has been described in the method invention also applies to the present invention.

According to a third invention, in the second invention, there is provided a return device that is installed on the outer surface of the body, receives a monitoring signal by electromagnetic waves, and transmits the monitoring signal whose frequency is converted, and the receiving device transmits from the returning device. In other words, it is configured to receive a converted monitoring signal having a converted frequency.
In this case, the receiving device is usually provided inside the vehicle together with the transmitting device. The reply device receives the monitoring signal, converts it to a frequency different from the received signal, and transmits it to the receiving device. Therefore, since the paths of the transmission device, the reply device, and the reception device are in a multipath environment, more accurate monitoring is possible. Further, the transmission / reception device may be provided on the outer surface of the body. In this case, the transmission / reception device and the return device transmit and receive electromagnetic waves that excite the body.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the receiving device detects a phase of the received monitoring signal, and whether or not the amount of phase change with the passage of time of the phase detector is greater than or equal to a threshold value. An alarm device that outputs a warning that an abnormality has occurred around the vehicle when the phase change amount determining means and the phase change amount determining means determine that the phase change amount is equal to or greater than a threshold value, Is provided.
The monitoring signal propagated through the multipath environment is received by the receiving device, and the phase change amount with respect to the passage of time is measured. When the amount of phase change is equal to or greater than a predetermined threshold, an alarm sound is output or an alarm signal is transmitted to the owner located at a position away from the vehicle. Thereby, the approach of a person to a vehicle, etc. can be detected, and theft of the vehicle can be prevented.
The alarm device includes a transmission device that wirelessly transmits an alarm signal, and an output device that receives the alarm signal and displays the alarm with light, sound, and a screen. Further, instead of transmitting the alarm signal wirelessly, an output device that is provided in a receiving device attached to the vehicle and outputs an alarm directly by light, sound, or the like may be used.

  A fifth invention is the fourth invention according to the fourth invention, wherein a control signal is input, a target frequency is set and a target frequency is set and stored in accordance with the control signal, and a target phase is set and stored. A reference signal oscillator that outputs a reference signal having a frequency and phase that match the target frequency set in the target frequency setting register and the target phase set in the target phase setting register, and a monitoring signal. A phase comparator that outputs a phase difference signal indicating a phase difference from the reference signal output by the reference signal oscillator, and a time difference between the phase difference signal output by the phase comparator and a frequency difference between the monitoring signal and the reference signal at that time And based on the phase difference indicated by the frequency control device that controls the target frequency of the reference signal oscillator based on the frequency difference and the phase difference signal output by the phase comparator. And a phase control device for controlling the target phase of the reference signal oscillator, and the phase detector detects the target phase set in the target phase setting register during the period in which the monitor signal is detected. It is detected as a phase.

The phase detector, the phase change amount determining means, the alarm device, the phase comparator, the frequency control device, and the phase control device can be configured by an analog circuit, a digital circuit, and a computer. The transmitter and the receiver include a modulator, a demodulator, an amplifier, and the like when performing modulation.
In the present invention, the control signal is an addition / subtraction pulse that increases / decreases the target frequency and the target phase by a unit amount, the reference signal oscillator is a digital synthesizer, and the target frequency setting register and the target phase setting register are based on the addition / subtraction pulse. , A register for increasing or decreasing the target frequency and the target phase. In this device, the frequency and phase of the reference signal are constantly changed to the frequency and phase of the received monitoring signal by feedback control while changing the frequency and phase of the reference signal by small amounts in the reception period of the monitoring signal. Follow-up control is performed to match. The target frequency and the target phase in a state where the frequency and the phase are synchronized are stored.

  In the present invention, the control signal is a signal indicating the absolute value of the target frequency and the target phase, the reference signal oscillator is a digital synthesizer, and the target frequency setting register and the target phase setting register receive the control signal. Each of these may have a register that sets the absolute value indicated by the control signal as the target frequency and target phase. In this apparatus, the target frequency and the target phase are set as absolute values during the monitoring signal reception period, and by changing these values, the frequency and phase of the reference signal are changed and feedback control is used to change the reference signal. The frequency and phase are controlled to follow the frequency and phase of the received monitoring signal. The target frequency and the target phase in a state where the frequency and the phase are synchronized are stored.

In these inventions, the target phase may be read by reading a value set in the target phase setting register, or by reading a control signal and a target phase output to the target phase setting register. . In short, any method may be used as long as the target phase is detected at two different times.
In the present invention, during the period in which the monitoring signal is detected, the target phase set in the target phase setting register is detected at a different time, and it is determined whether or not the variation amount of the target phase is equal to or greater than a predetermined value. The That is, when the environmental state of the vehicle changes, the electromagnetic field around the vehicle changes, and the phase of the monitoring signal received by the receiving device changes. When this phase is detected at different times and the amount of phase change with the passage of a predetermined time is greater than a predetermined value, the vehicle environment such as approach of an outsider to the vehicle, contact with the vehicle, opening of a door, etc. Detecting a change in state. When the phase variation amount determining unit determines that the phase variation amount is equal to or greater than a predetermined value, an alarm is given that an abnormality has occurred around the vehicle.

  In a sixth aspect based on the third aspect, the receiving device constitutes a transmitting / receiving device together with the transmitting device, and receives and monitors the transmission monitoring signal output from the transmitting device and the transmission signal from the reply device, and is received and demodulated. A phase difference detector for detecting a phase difference from the signal, a phase difference change amount judging means for judging whether or not a change amount of the phase difference output from the phase difference detector with the lapse of time is equal to or greater than a threshold value, A vehicle monitoring device comprising: an alarm device that outputs an alarm that an abnormality has occurred around the vehicle when the amount of change in phase difference is determined to be greater than or equal to a threshold value by the amount determination means. is there.

The return device demodulates the received signal into a baseband signal when frequency-converting the received signal into a signal of another frequency and when the received signal is modulated, then shapes the waveform, and uses that waveform as the frequency of the carrier wave at the time of transmission And a case where a carrier wave having a different frequency is modulated and returned.
In the present invention, the phase difference between the transmission monitoring signal and the reception monitoring signal is detected. When the multipath environment changes due to the approach of a person to the vehicle or the like, this phase difference changes with time. When the amount of change in the phase difference is equal to or greater than a predetermined threshold, it can be determined that the multipath environment has changed, that is, the person has approached. In this case, an alarm sound can be output or an alarm signal can be transmitted to the owner located at a position away from the vehicle to notify the approach of a person to the vehicle. This effectively prevents the vehicle from being stolen.
In the present invention, the transmission monitoring signal and the reception monitoring signal are the same as the monitoring signal described above, and mean a baseband signal when the electromagnetic wave to be excited is modulated.

  In a seventh aspect based on the third aspect, the receiving device constitutes a transmitting / receiving device together with the transmitting device. The transmitting / receiving device includes a reference signal oscillator for oscillating a reference signal, a reference signal output from the reference signal oscillator, and a reply device. A first phase difference detector for detecting a first phase difference between the received monitoring signal and a reception monitoring signal obtained by demodulating, and a first phase difference output from the first phase difference detector is zero A transmission monitoring signal oscillator for controlling the frequency and phase of the transmission monitoring signal to detect the second phase difference between the reference signal output from the reference signal oscillator and the transmission monitoring signal output from the transmission monitoring signal oscillator. Two phase difference detectors, phase difference change amount determining means for determining whether or not a change amount of the second phase difference output from the second phase difference detector with respect to time is equal to or greater than a threshold value, and phase difference change amount determining means The amount of change in the second phase difference is If it is determined that the value or more, an abnormality occurs in the vicinity of the vehicle, a monitoring device for a vehicle and having a, a warning device for outputting an alarm.

The present invention is a device in which a transmission monitoring signal is subjected to a PLL (Phase Locked Loop) in a circuit consisting of a transmission device, a reply device, and a reception device. Therefore, the frequency and phase of the transmission monitoring signal are controlled so that the phase of the reception monitoring signal is synchronized with the phase of the reference signal, and the vehicle body is excited by the electromagnetic wave based on the transmission monitoring signal. In a multipath environment, the monitoring signal in the circuit of the above-mentioned circuit is PLL-synchronized, and even if there is a change in the multipath environment, the frequency and phase of the transmission monitoring signal are subject to follow-up control while maintaining the PLL synchronization. Therefore, when the time change amount of the phase difference between the transmission monitoring signal and the reference signal is equal to or greater than a predetermined threshold, it is determined that the multipath environment has changed. This makes it possible to detect a change in the multipath environment with high accuracy.
Also in this case, the return device demodulates the received signal into a baseband signal when frequency-converting the received signal to another frequency, and when the received signal is modulated, then shapes the waveform, and uses this waveform as a carrier wave at the time of transmission. And a case where a carrier wave having a frequency different from the above frequency is modulated and returned.

  In an eighth aspect based on the third aspect, the receiving device constitutes a transmitting / receiving device together with the transmitting device. The transmitting / receiving device includes a reference signal oscillator for oscillating a reference signal, a reference signal output from the reference signal oscillator, and a reply device. A first phase difference detector for detecting a first phase difference between the received monitoring signal and a reception monitoring signal obtained by demodulating, a reference signal output from the reference signal oscillator, and a transmission output from the transmitting device A second phase difference detector for detecting a second phase difference from the monitoring signal, a comparator for outputting a difference in absolute value between the first phase difference and the second phase difference, and an output of the comparator being zero The transmission monitoring signal oscillator for controlling the frequency and phase of the transmission monitoring signal and the time of the first phase difference output from the first phase difference detector or the second phase difference output from the second phase difference detector Phase difference that determines whether the amount of change over time is greater than or equal to a threshold When the change amount determination means and the phase difference change amount determination means determine that the change amount of the first phase difference or the second phase difference is greater than or equal to the threshold value, an alarm is output that an abnormality has occurred around the vehicle. A vehicle monitoring device comprising: an alarm device.

  The present invention, like the seventh invention, is a device that applies a PLL to the transmission monitoring signal in a circuit that consists of a transmission device, a reply device, and a reception device. Since there is a propagation delay time in the propagation path from the transmission device to the reception device via the return device, the phase of the reception monitoring signal is always delayed with respect to the phase of the transmission monitoring signal. Therefore, the advancement of the transmission monitoring signal is such that the absolute value of the delay phase difference (first phase difference) of the reception monitoring signal with respect to the reference signal is equal to the advance phase difference (second phase difference) of the transmission monitoring signal with respect to the reference signal. The phase is determined. In the present invention, PLL synchronization is applied between the transmission device and the reception device under such conditions. When the temporal change amount of the delay phase difference or the advance phase difference is equal to or greater than a predetermined threshold value, it is possible to detect a change in the multipath environment such as a person approaching the vehicle. Even if there is a change in the multipath environment, the frequency and phase of the transmission monitoring signal are tracked and controlled in synchronization with the PLL, so that it is possible to detect the change in the multipath environment with high accuracy.

  In the first to eighth aspects of the invention, the frequency of the electromagnetic wave that excites the body of the vehicle by the transmission device is not limited, but is preferably a frequency that excites the evanescent wave on the surface of the body. The evanescent wave does not propagate in space. Therefore, noise due to electromagnetic waves is not given to the electric equipment outside the vehicle. In the case of an evanescent set wave, the electromagnetic field in which the evanescent wave is excited changes due to the proximity and contact of the vehicle body. As a result, the approach of a person to the vehicle can be detected without becoming a noise source, and theft of the vehicle can be prevented accurately and in advance.

  If an evanescent set wave in which an electromagnetic field is constrained around the vehicle is used as the frequency of the carrier wave, a frequency at which wavelength / 2 is longer than the maximum length of a continuous metal body of the vehicle may be used. For example, in the case of 60 MHz, it becomes an evanescent wave in which the electromagnetic field is constrained around the vehicle, and in the case of 300 MHz, an electromagnetic field is also formed in the peripheral part separated from the vehicle. When a person or the like approaches the vehicle, the phase of the electromagnetic wave received by the receiving device due to the reflection of the electromagnetic wave by the person changes due to multipath or the like. By detecting the temporal change amount of the phase by the receiving device, it is possible to detect the change in the electromagnetic field around the vehicle, that is, the approach of the person to the vehicle, the contact, the opening of the door, and the like.

  In the present invention, by exciting the vehicle body with electromagnetic waves, a multipath environment can be generated between the transmission device and the reception device in the propagation path in which the body is interposed. Changes in the environment such as the approach of a person in this multipath environment can be detected by the magnitude of the temporal change amount of the phase of the monitoring signal received by the receiving device. When the amount of phase change is equal to or greater than a predetermined value, an alarm is generated because there is a change in the surrounding environment of the vehicle. This simplifies the configuration of the monitoring device, enables downsizing, and more accurately detects changes in only the environment around the vehicle without being affected by electromagnetic waves far from the vehicle. This can prevent the vehicle from being stolen more accurately. In particular, when the surface of the vehicle body is excited with an evanescent wave, the monitoring device is prevented from becoming a noise source for electrical equipment outside the vehicle.

The block diagram of the monitoring apparatus which concerns on the specific Example 1 of this invention. 2 is a timing chart for explaining the principle of a phase comparator in the apparatus according to the first embodiment. FIG. 3 is an explanatory diagram showing a relationship between a level of a phase difference signal output from a phase comparator and a phase difference in the apparatus according to the first embodiment. The block diagram of the monitoring apparatus which concerns on the specific Example 2 of this invention. The block diagram of the monitoring apparatus which concerns on the specific Example 3 of this invention. The flowchart which showed the process sequence of CPU which implement | achieves the determination means of the monitoring apparatus which concerns on the Example of this invention. The block diagram which showed the transmitter of the monitoring apparatus which concerns on a present Example. Explanatory drawing which showed the relationship between the attachment position of the transmitter of the monitoring apparatus which concerns on a present Example, and a receiver, and a vehicle. The block diagram of the monitoring apparatus which concerns on the specific Example 4 of this invention. The block diagram of the monitoring apparatus which concerns on the specific Example 5 of this invention. The block diagram of the transmission / reception apparatus of the monitoring apparatus which concerns on the specific Example 6 of this invention. The block diagram of the monitoring apparatus which concerns on the specific Example 7 of this invention. Explanatory drawing which showed the relationship between the installation position of the transmission / reception apparatus which comprises the monitoring apparatus which concerns on an Example, a reply apparatus, and a vehicle. Explanatory drawing which shows the electromagnetic field in the body and body periphery at the time of exciting the vehicle body with the electromagnetic wave of 300 MHz. Explanatory drawing which shows the electromagnetic field in the body and body periphery at the time of exciting the vehicle body with 60-MHz electromagnetic waves.

  Hereinafter, the present invention will be described based on specific examples. The present invention is not limited to the following examples.

  FIG. 8 is a diagram illustrating attachment positions of the transmission device 8 and the reception device 1 of the monitoring device of this embodiment with respect to the vehicle. The transmission device 8 and the reception device 1 are attached to the vehicle body. The transmitter 8 and the receiver 1 are provided at different positions with respect to the body. The transmission device 8 is configured as shown in FIG. A square wave of the first pulse signal of 2 MHz is generated by the oscillator 94. The baseband first pulse signal is a monitoring signal or a transmission monitoring signal. A 1 / 2n-edge circuit in the quadrature modulator 91 generates a pulse signal that rises in synchronization with the fall of the first pulse signal and falls in synchronization with the next fall. Also, a pulse signal that rises in synchronization with the rising edge of the first pulse signal and falls in synchronization with the next rising edge is generated by the 1 / 2p-edge circuit in the quadrature modulator 91. That is, two pulse signals (square waves) having a phase difference of π / 2 at 1 MHz are generated. These two signals are orthogonally modulated by the quadrature modulator 91 and synthesized by the two carriers cos (ωt) and sin (ωt) generated by the carrier wave generation circuit 96. The synthesized signal becomes an excitation signal (electromagnetic wave for excitation) for exciting the body. The excitation signal is equivalent to a signal obtained by subjecting the first pulse signal of 2 MHz to binary BPSK modulation with a single carrier wave. The excitation signal generated in this way is transmitted from the transmission conductor 92. The transmission conductor 92 includes a coaxial cable core wire and a shield wire. The core wire is connected to a location where the metal body of the vehicle is located, and the shield wire is connected to a location away from the connection location. Thereby, the metal body is excited by the excitation signal.

  Next, the receiving device 1 will be described. FIG. 1 is a configuration diagram of a receiving device 1 of the monitoring device according to the present embodiment. The detection conductor 20 is connected to the quadrature demodulator 30 via the amplifier 21. The detection conductor 20 includes a coaxial cable core wire and a shield wire. The core wire and the shield wire are connected to the metal body of the vehicle at a predetermined distance. Thereby, an excitation signal which is an electromagnetic field excited on the metal body by the transmitter 8 can be received. The excitation signal is a signal obtained by performing binary phase shift keying (BPSK) on the carrier wave using the first pulse signal (monitoring signal) that is a square wave of 2 MHz shown in FIG. Actually, in order to use quadrature demodulation by the Costas loop, two signals of a pulse signal of 1 MHz and a pulse signal obtained by shifting the phase of this signal by π / 2 are quadrature modulated, synthesized, and transmitted. doing. However, since the result of EX-OR synthesis of two 1 MHz pulse signals having a phase difference of π / 2 obtained by quadrature demodulation is a 2 MHz square wave, the result is a 2 MHz first pulse signal. Is equivalent to the one modulated with a single carrier wave. Therefore, the following description will be made as binary BPSK modulation without particular distinction. Of course, a signal obtained by modulating the first pulse signal of 2 MHz with a single carrier wave may be used as the excitation signal. For this modulation, amplitude shift keying (ASK), phase shift keying (PSK), and frequency shift keying (FSK) may be used in addition to BPSK.

  The quadrature demodulator 30 is a synchronous quadrature demodulation circuit using a Costas loop. The received signal is demodulated by carrier waves sin (ωt) and cos (ωt) input to the quadrature demodulator 30. At this time, the phases of the demodulated carriers sin (ωt) and cos (ωt) are feedback-controlled so that the average value of the products of the two pulse signals demodulated by the orthogonal demodulator 30 becomes zero. In a synchronized state, two 1 MHz two pulse signals having a phase difference of π / 2 are obtained. The two 1 MHz pulse signals are subjected to exclusive OR addition by the EX-OR circuit 31 to demodulate the first pulse signal (received monitoring signal and received monitoring signal) which is a 2 MHz square wave. The demodulated result is a 2 MHz baseband pulse signal (square wave) as shown in FIG. 1, and the baseband first pulse signal S1 (monitoring signal), which is a modulation signal of the excitation signal, is demodulated.

  The first pulse signal S1 output from the quadrature demodulator 30 and the second pulse signal S2 (reference signal) output from a pulse oscillator 60 constituting a reference signal oscillator described later have a phase difference (including a frequency difference) between them. It inputs into the phase frequency type phase comparator (PFC) 32 (for example, 4046) to detect. As shown in (a), (b), and (c) of FIG. 2, the phase comparator 32 is only in a period in which the rising edge of the first pulse signal S1 is ahead of the rising edge of the second pulse signal S2. A signal A that becomes a high level is generated (c). At this time, the signal B is at a low level. Further, as shown in FIGS. 2A, 2D, and 2E, the signal B only during a period in which the rising edge of the first pulse signal S1 is delayed from the rising edge of the second pulse signal S2. Is generated (e). At this time, the signal A is at a low level. By inputting these two signals A and B to the two gates of the CMOS, as shown in (f) and (g) of FIG. 2, the rising of the first pulse signal S1 is the second pulse. A high-level pulse signal is output during a period that is ahead of the rising edge of the signal S2, and a low-level pulse signal is output during a period when the rising edge of the first pulse signal S1 is delayed from the rising edge of the second pulse signal S2. The output signal S 3 of 32 is input to a low-pass filter (loop filter) 33.

  In the low-pass filter 33, the output signal S3 of (f): or (g) of FIG. 2 is smoothed. That is, when the first pulse signal S1 is in a leading phase with respect to the second pulse signal S2, the phase difference signal S4 output from the low-pass filter 33 increases as the phase difference between the two signals increases. Become. Further, when the first pulse signal S1 is in a delayed phase with respect to the second pulse signal S2, the phase difference signal S4 becomes lower as the phase difference between the two signals is larger.

  When the phase difference signal S4 output from the low-pass filter 33 is at the reference level, the frequency difference and phase difference between the first pulse signal S1 and the second pulse signal S2 are zero. When the first pulse signal S1 and the second pulse signal S2 have the same frequency and the phase difference signal S4 is at the maximum level, the first pulse signal S1 is advanced by 2π with respect to the second pulse signal S2. When the phase difference signal S4 is at the 0 level, the first pulse signal S1 is in a delayed phase of -2π with respect to the second pulse signal S2. The relationship between the phase θ of the first pulse signal S1 with respect to the second pulse signal S2 (hereinafter, this phase is referred to as the phase difference θ) and the phase difference signal S4 that is the output of the low-pass filter is proportional as shown in FIG. There is a relationship. In the present embodiment, the phase comparator of the present invention includes a phase comparator 32 and a low-pass filter 33. When the frequency of the first pulse signal is higher than the frequency of the second pulse signal, the phase difference signal S4 exists between the reference level and the maximum level, and when the frequency of the second pulse signal is increased by feedback control, The phase difference signal S4 vibrates as the frequency changes between the reference level and the maximum level. Further, when the frequency of the first pulse signal is lower than the frequency of the second pulse signal, the phase difference signal S4 exists between the reference level and the 0 level, and the frequency of the second pulse signal is reduced by feedback control. Then, the phase difference signal S4 vibrates with a change in frequency between the reference level and the 0 level.

Next, a circuit for frequency synchronization will be described. The phase difference signal S4 is input to the frequency difference calculator 40 and the delay circuit 41, and the output of the delay circuit 41 is input to the frequency difference calculator 40. The frequency difference calculator 40 is a circuit that performs the following processing from the phase difference signal S4. The time differentiation of the phase difference θ (t) represents the frequency difference ω (t) at time t with respect to the fundamental frequency of the second pulse signal of the fundamental frequency of the first pulse signal S1. That is, the following equation is established.
However, Δt is a minute delay time in the delay circuit 41, and the output signal S5 of the delay circuit 41 represents θ (t−Δt).

  The frequency difference calculator 40 calculates the frequency difference ω (t) from the value obtained by dividing θ (t) −θ (t−Δt) by Δt. Since ω (t) is a negative value, a positive bias (reference level) is added to ω (t) and output to the comparator 42 as a signal S6 in the positive range. When the signal S6 is at the reference level, the frequency difference ω (t) is zero. When the signal S6 is greater than the reference level, the frequency difference ω (t) is positive, and the greater the difference from the reference level, the greater the frequency difference ω (t). When the signal S6 is smaller than the reference level, the frequency difference ω (t) is negative, and the absolute value of the frequency difference ω (t) is larger as the difference from the reference level is larger.

  The signal S6 output from the frequency difference calculator 40 is input to one input terminal of the comparator 42. The reference level is input to the other terminal of the comparator 42. The comparator 42 has a differential output, and an inverted signal of one output signal is output from the other output terminal. Therefore, when the signal S6 input to the comparator 42 is higher than the reference level, the high level signal S7 is output from the non-inverting output terminal of the comparator 42. When the signal S6 is lower than the reference level, a high level signal S8 is output from the inverting output terminal. That is, the comparator 42 is a circuit that determines whether the frequency difference ω (t) is positive or negative. The signals S7 and S8 output from the comparator 42 are input to one input terminals of the AND circuits 43 and 44, respectively. Clock signals having the same frequency for pulsing the signals S7 and S8 are input to the other input terminals of the AND circuits 43 and 44.

  Therefore, as for the signals S9 and S10 output from the AND circuits 43 and 44, the high levels of the signals S7 and S8 are output only during the period when the clock pulse is at the high level. That is, during the period in which the frequency difference ω (t) is positive, the signal S9 becomes a pulse signal synchronized with the clock, and the signal 10 maintains a zero level. Further, during the period in which the frequency difference ω (t) is negative, the signal S10 becomes a pulse signal synchronized with the clock, and the signal 9 maintains a zero level. These signals S9 and S10 are input to the addition terminal and the subtraction terminal of the target frequency setting register 61. The target frequency setting register 61 adds 1 to the value held every time one addition pulse is inputted from the addition terminal, and only 1 is held every time one subtraction pulse is inputted from the subtraction terminal. A circuit for subtraction. In other words, the value held by the target frequency setting register 61 increases sequentially every time an addition pulse is input in a period in which the frequency difference ω (t) is positive, and a period in which the frequency difference ω (t) is negative. As the subtraction pulse is input, the value decreases sequentially.

  The value held in the target frequency setting register 61 is converted to an analog level by the D / A converter 62 and input to the voltage controlled oscillator (VCO) 63. The value held in the target frequency setting register 61 gives the frequency of the oscillation signal of the VCO 63. The output signal of the VCO 63 is input to the binarization circuit 65 after the phase is adjusted by the phase shifter 64. The output of the binarization circuit 65 is the second pulse signal S2 (reference signal).

  Phase comparator 32, low-pass filter 33, frequency difference calculator 40, comparator 42, AND circuits 43 and 44, target frequency setting register 61, D / A converter 62, VCO 63, phase shifter 64, binarization circuit 64 Becomes a frequency feedback loop. As a result, the second pulse signal S2 has a frequency set in the target frequency setting register 61 when the frequency difference ω (t) obtained by the frequency difference calculator 40 becomes zero, and the first pulse signal S1 Match the frequency. When the frequency difference ω (t) is a positive value, it means that the frequency of the second pulse signal S2 is smaller than the frequency of the first pulse signal S1. During a period when the frequency difference ω (t) takes a positive value, the value held in the target frequency setting register 61 increases from the input of the signal S9 (addition pulse), and the frequency of the second pulse signal S2 increases. On the contrary, during the period in which the frequency difference ω (t) takes a negative value, the value held in the target frequency setting register 61 decreases from the input of the signal S10 (subtraction pulse), and the frequency of the second pulse signal S2 decreases. By such feedback control, the operation is performed so that the frequency difference ω (t) converges to zero.

  Next, a circuit for phase synchronization will be described. As shown in FIG. 3, the phase difference signal S4 output from the low-pass filter 33 is a signal having a level in the positive range. When the phase difference signal S4 is at the reference level, the phase difference θ (t) is zero. is there. When the phase difference signal S4 is higher than the reference level, the second pulse signal S2 is in a delayed phase with respect to the first pulse signal S1, and the higher the level of the phase difference signal S4, the longer the delay of the second pulse signal S2. The phase value is also large. When the phase difference signal S4 is lower than the reference level, the second pulse signal S2 is in an advance phase with respect to the first pulse signal S1, and the advance of the second pulse signal S2 is lower as the level of the phase difference signal S4 is lower. The phase value is also large. The phase difference signal S4 is input to one input terminal of the comparator 46. The reference level is input to the other input terminal of the comparator 46.

  The comparator 46 has a differential output, and an inverted signal of the output signal of one terminal is output from the other terminal. Therefore, when the phase difference signal S4 input to the comparator 46 is higher than the reference level, a high level signal S11 is output from the non-inverting output terminal of the comparator 46. When the phase difference signal S4 is lower than the reference level, a high level signal S12 is output from the inverting output terminal. That is, the comparator 46 is a circuit that determines whether the phase difference θ (t) is positive or negative. The signals S11 and S12 output from the comparator 46 are input to one input terminals of AND circuits 47 and 48, respectively. The other input terminals of the AND circuits 47 and 48 receive clock signals having the same frequency for pulsing the signals S11 and S12.

  Therefore, as for the signals S13 and S14 output from the AND circuits 47 and 48, the high levels of the signals S11 and S12 are output only during the period when the clock pulse is at the high level. That is, during the period in which the phase difference θ (t) is positive, the signal S13 becomes a pulse signal synchronized with the clock, and the signal 14 maintains a zero level. Further, during the period in which the phase difference θ (t) is negative, the signal S14 becomes a pulse signal synchronized with the clock, and the signal 13 maintains the zero level. These signals S13 and S14 are input to the addition terminal and the subtraction terminal of the target phase setting register 66. The target phase setting register 66 adds 1 to the held value every time one addition pulse is input from the addition terminal, and only 1 to hold the value every time one subtraction pulse is input from the subtraction terminal. A circuit for subtraction. In other words, the value held by the target phase setting register 66 increases sequentially every time an addition pulse is input in the period in which the phase difference θ (t) is positive, and the period in which the phase difference θ (t) is negative. As the subtraction pulse is input, the value decreases sequentially.

  The value held in the target phase setting register 66 is converted to an analog level signal S15 by the D / A converter 67 and input to the phase shifter 64. In the phase shifter 64, the phase of the oscillation signal output from the VCO 63 is controlled according to the level of the signal S15. In this way, the phase of the second pulse signal S2 (reference signal) is controlled.

  The phase comparator 32, the low-pass filter 33, the comparator 46, the AND circuits 47 and 48, the target phase setting register 66, the D / A converter 67, the phase shifter 64, and the binarization circuit 64 form a phase feedback loop. . When the frequency difference ω (t) is positive, the phase difference signal S4 output from the low-pass filter 33 becomes a sawtooth wave as shown in FIG. 3, and always changes in the increasing direction. When the frequency difference ω (t) is negative, the phase difference signal S4 becomes a sawtooth wave as shown in FIG. 3, and always changes in a decreasing direction. Therefore, as long as there is a time variation in the phase difference θ (t), the frequency difference ω (t) is observed, feedback regarding the frequency is applied, and the frequency difference ω (t) is stabilized to be zero. The phase difference θ (t) in this state is a phase difference that does not depend on the frequency difference, and is controlled by the above-described phase feedback loop so that this phase difference becomes zero.

As a result, the phase of the second pulse signal S2 (reference signal) becomes the phase set in the target phase setting register 66 when the phase difference θ (t) becomes zero, and the first pulse signal S1 (monitoring signal). Match the phase. When the phase difference θ (t) is a positive value, it means that the phase of the first pulse signal S1 is ahead of the phase of the second pulse signal S2. During the period in which the phase difference θ (t) takes a positive value, the value held in the target phase setting register 66 increases from the input of the signal S13 (addition pulse), and the phase of the second pulse signal S2 is advanced. Conversely, during the period in which the phase difference θ (t) takes a negative value, the value held in the target phase setting register 61 decreases from the input of the signal S14 (subtraction pulse), and the phase of the second pulse signal S2 is delayed. When the phase difference θ (t) becomes zero, the fluctuation of the value held in the target phase setting register 61 stops, the phase of the second pulse signal S2 is held at the set phase, and the second pulse signal S2 has its phase. At the same time as the phase of the first pulse signal.
By such frequency and phase feedback control, the operation is performed so that the frequency difference ω (t) and the phase difference θ (t) converge to zero.

As described above, the second pulse signal S2 (reference signal) synchronized with the frequency and phase of the first pulse signal S1 (monitoring signal, reception monitoring signal) is generated by feedback control of the frequency and phase.
With the above operation, the target frequency setting register 61 and the target phase setting register 66 hold the frequency and phase at the current time of the received first pulse signal S1 in real time. The value held in the target phase setting register 66 is read by the CPU 70 at regular time intervals T, and the process shown in FIG. 6 is executed.

In step 100 of FIG. 6, the value at the current time of the target phase setting register 66 is input as φ ₁ . Next, in step 102, it is determined whether or not a predetermined time T has elapsed since the phase was input. When the predetermined time T has elapsed, in step 104, the value at the current time of the target phase setting register 66 is φ. _Entered as ₂ . Next, in step 106, the absolute value Δφ = | φ ₂ −φ ₁ | of the phase difference between the phases φ ₁ and φ _{2 at} the two times is calculated. If it is determined in step 108 that the absolute value Δφ of the phase difference is greater than or equal to a predetermined value, the transmitter 71 is driven and an alarm signal is transmitted in step 110 assuming that the electromagnetic wave environment around the vehicle body has changed. The This alarm signal is received at a position away from the vehicle, for example, the receiver 72 held by the owner of the vehicle, and the alarm is notified to the owner by sound, light, display on the screen, etc. Is done. Next, in step 112, it is determined whether or not a predetermined time T has elapsed since the phase φ ₂ was input. If the predetermined time T has elapsed, the process returns to step 100, and the above processing is repeatedly executed. The monitoring state continues. In this way, it is possible to notify the owner of the vehicle of an outsider's contact with the vehicle body or the opening of the door.

  In this embodiment, the reference signal oscillator (pulse signal oscillator 60) of the present invention includes a target frequency setting register 61, a target phase setting register 66, D / A converters 62 and 67, a VCO 63, a phase shifter 64, and a binary value. The circuit 65 is constituted by a circuit 65. The frequency control device according to the present invention includes a frequency difference calculator 40, a comparator 42, and AND circuits 43 and 44. The phase control device according to the present invention includes a comparator 46 and AND circuits 47 and 48. The phase change amount determining means includes a CPU 70 and steps 100 to 108 and 112. The alarm device includes a CPU 70, a step 110, a transmitter 71, a receiver 72, and an alarm device 73.

  In the above embodiment, the output of the low-pass filter 33 is A / D converted, polarity determination by the frequency difference calculator 40 and comparators 42 and 46, and pulsing by the AND circuits 43, 44, 47 and 48 are performed using a computer. It may be realized by digital processing. That is, the addition pulse and the subtraction pulse output to the target frequency setting register 61 and the target phase setting register 66 may be output under software control by a computer. In this case, the computer can use the CPU 70. Further, the phase comparator 32 and the low-pass filter 33 may be constituted by digital circuits. The transmission device 8 may be provided in the interior space of the vehicle. In this case, the transmission conductor 92 is an antenna provided in the interior space of the vehicle. The vehicle body is indirectly excited by the electromagnetic waves radiated from the antenna.

  FIG. 4 is a configuration diagram of the monitoring apparatus according to the second embodiment. In the present embodiment, the pulse generator 60 that is the reference signal oscillator of the first embodiment is configured by a digital synthesizer 80. As in the first embodiment, the digital synthesizer 80 has a target frequency setting register 61 and a target phase setting register 66 for adding and subtracting values held by addition pulses and subtraction pulses. The digital synthesizer 80 is a device that generates a square wave from a frequency set in the target frequency setting register 61 and a phase set by the target phase setting register 66 by a computer. The operation principle of synchronizing the frequency and phase of the second pulse signal S2 (reference signal) with respect to the first pulse signal S1 (monitoring signal) is the same as in the first embodiment. Further, the process of converting the phase difference signal S4 output from the low-pass filter 33 into a digital value and outputting the addition pulse and the subtraction pulse may be realized by a computer.

The value held in the target phase setting register 66 is read by the CPU 70 at regular time intervals T as in the first embodiment, and the process shown in FIG. 6 is executed. When the absolute value Δφ = | φ ₂ −φ ₁ | of the phase difference between the phases φ ₁ and φ ₂ at two different times is determined to be equal to or greater than a predetermined value, the transmitter 71 is driven and an alarm signal is generated. Sent. The subsequent steps are the same as those in the first embodiment. In this way, it is possible to notify the owner of the vehicle of an outsider's contact with the vehicle body or the opening of the door.

  In the second embodiment, the target frequency setting register 61 and the target phase setting register 66 of the digital synthesizer 80 are composed of incremental registers that perform addition / subtraction using addition pulses and subtraction pulses. In the present embodiment, the target frequency setting register and the target phase setting register of the digital synthesizer are configured by an absolute value register that holds input data (absolute value). As shown in FIG. 5, the digital synthesizer 81 has a target frequency setting register 82 and a target phase setting register 83 for setting input data. The generation of a square wave (reference signal) according to the frequency and phase set in these registers is the same as in the second embodiment.

  Since the target frequency setting register 82 and the target phase setting register 83 are absolute value registers, in this embodiment, the signal S6 indicating the frequency difference ω (t) output by the frequency difference calculator 40 and the low-pass filter 33 are output. PID calculators 51 and 52 for inputting a phase difference signal S4 indicating the phase difference θ (t) are provided. The PID calculators 51 and 52 are devices that calculate a control amount by calculating a deviation of the level of the signal S6 and the phase difference signal S4 with respect to a reference level, an integral of the deviation, and a differential of the deviation. This reference level is a level at which the frequency difference ω (t) becomes zero and a level at which the phase difference θ (t) becomes zero. The frequency control amount and the phase control amount calculated by the PID calculators 51 and 52 are set in the target frequency setting register 82 and the target phase setting register 83, respectively. Further, the phase value output from the PID calculator 52, that is, the phase value set in the target phase setting register 83 is read by the CPU 70 at a period of a predetermined time interval T.

  During a period when the frequency difference ω (t) is positive, the output frequency control amount is increased by the integration function of the PID calculator 51. During the period when the frequency difference ω (t) is negative, the output frequency control amount is reduced by the integration function of the PID calculator 51. When the frequency difference ω (t) becomes zero, the integral value does not change, and the frequency control amount becomes a constant value.

  Similarly, during the period in which the phase difference θ (t) is positive, the output phase control amount increases due to the integration function of the PID calculator 52. During the period in which the phase difference θ (t) is negative, the output phase control amount decreases due to the integration function of the PID calculator 52. When the phase difference θ (t) becomes zero, the integral value does not change, so the phase control amount becomes a constant value. By such frequency and phase feedback control, the frequency and phase of the second pulse signal S2 (reference signal) are synchronized with the frequency and phase of the first pulse signal S1 (monitoring signal).

The phase output from the PID calculator 52 and held in the target phase setting register 66 is read by the CPU 70 at regular time intervals T as in the first embodiment, and the processing shown in FIG. Is executed. When the absolute value Δφ = | φ ₂ −φ ₁ | of the phase difference between the phases φ ₁ and φ ₂ at two different times is determined to be equal to or greater than a predetermined value, the transmitter 71 is driven and an alarm signal is generated. Sent. The subsequent steps are the same as those in the first embodiment. In this way, it is possible to notify the owner of the vehicle of an outsider's contact with the vehicle body or the opening of the door.

  In the present embodiment, the frequency control device of the present invention is constituted by a frequency difference calculator 40 and a PID calculator 51. In addition, the phase control apparatus of the present invention is configured by a PID computing unit 52 in this embodiment. The PID calculators 51 and 52 may perform PI calculation without differential correction or only integration calculation when the tracking deviation due to the change in the electromagnetic wave environment around the vehicle is small. The PID calculators 51 and 52 may be configured by analog circuits, digital circuits, and computers. Also in the present embodiment, the process of converting the phase difference signal S4 output from the low-pass filter 33 into a digital value, performing PID calculation, and outputting the control amount may be realized by a computer. Further, this computer may be shared with the CPU 70. Similarly to the first embodiment, the phase change amount determination means is constituted by the CPU 70 and steps 100 to 108 and 112. The alarm device includes a CPU 70, a step 110, a transmitter 71, a receiver 72, and an alarm device 73.

  FIG. 9 is a block diagram illustrating a specific configuration of the transmission / reception device 100 and the reply device 200 according to a specific embodiment 4 of the present application. In this embodiment, the transmission / reception device 100 is provided in the interior space of the vehicle, and the reply device 200 is attached to the outer surface of the vehicle body.

Of the configuration of the transmission / reception device 100 of FIG. 9, the transmission device is as follows.
A sine wave having a fixed frequency f is output from the fixed frequency oscillator 10 which is a reference signal oscillator. The reference signal output from the fixed frequency oscillator 10 is input to the first phase comparator 11, the second phase comparator 18, and the first high frequency generator 14.

  The first phase comparator 11 forms a phase-locked loop (PLL) through the low-pass filter 12, the voltage-controlled oscillator 13 that is a transmission monitoring signal oscillator, and the propagation path of the transmission / reception device 100 and the return device 200. The first phase comparator 11 receives the reception monitoring signal output from the bandpass filter 163 and the reference signal output from the fixed frequency oscillator 10. The first phase comparator 11 outputs the reference signal for the reception monitoring signal to the reference signal. A first phase difference that is a phase difference is output. Then, the frequency and phase of the transmission monitoring signal output from the voltage controlled oscillator 13 are controlled so that the first phase difference becomes zero. In this way, the transmission is a sine wave of the frequency f output from the voltage controlled oscillator 13 such that the phase of the reception monitoring signal output from the bandpass filter 163 matches the phase of the reference signal output from the frequency fixed oscillator 10. The phase of the monitoring signal is advanced.

The sine wave of frequency f output from the voltage controlled oscillator 13 is input to the mixer 15. The mixer 15 can be composed of a double balanced mixer. The mixer 15 receives a high frequency having a frequency Nf (N >> 1) from the first high frequency generator 14. Thus, in order to excite the vehicle body from the first transmitting antenna A _T1 , the band filter 161 transmits the double sideband wave (DSB (Nf)) (excitation signal) only in the vicinity of the frequency Nf from the output of the mixer 15. Electromagnetic waves are emitted. As a result, the vehicle body is in an excited state. The carrier wave with the frequency Nf may be completely suppressed or coexist without being suppressed. Although not shown in detail, the first high frequency generator 14 can be configured by a phase locked loop (PLL) including, for example, a phase comparator, a low-pass filter, a voltage controlled oscillator, and a frequency divider. The body may be directly excited by attaching the excitation conductor directly to the vehicle body as in the first embodiment instead of the first transmission antenna A _T1 .

The configuration of the reply device 200 in FIG. 9 is as follows.
The double sideband wave (DSB (Nf)) (excited electromagnetic wave) near the frequency Nf received by the second receiving antenna A _2R attached to the vehicle body is transmitted only near the frequency Nf by the bandpass filter 262, The signal is demodulated synchronously by the second synchronous demodulator 27, passes through the band filter 263, and is demodulated as a reception monitoring signal. The demodulated sine wave of frequency f is input to the mixer 25 (second modulator). Although details are not shown as the second synchronous demodulator 27, any known synchronous demodulator can be adopted in addition to the Costas loop.
A sine wave having a frequency f is output from the fixed frequency oscillator 23, and a high frequency having a frequency Mf (M >> 1 and M ≠ N) is generated by the second high frequency generator 24 and input to the mixer 25. In this way, the output of the mixer 25 is transmitted through the band filter 261 through the double sideband wave (DSB (Mf)) only in the vicinity of the frequency Mf, and transmitted from the second transmitting antenna A _T2 to the transmitting / receiving apparatus 100. The carrier wave with the frequency Mf may be completely suppressed or coexist without being suppressed. Although not shown in detail, the second high-frequency generator 24 can be configured by a phase-locked loop (PLL) including, for example, a phase comparator, a low-pass filter, a voltage-controlled oscillator, and a frequency divider. The transmission signal from the second transmission antenna A _T2 may be transmitted as an electromagnetic wave to the transmission / reception device 100, or may be transmitted by exciting the vehicle body with the electromagnetic wave.

The configuration of the receiving device of the transmitting / receiving device 100 of FIG. 9 is as follows.
The double sideband wave (DSB (Mf)) near the frequency Mf received by the first receiving antenna A _1R is transmitted only in the vicinity of the frequency Mf by the band filter 162, is synchronously demodulated by the first synchronous demodulator 17, and is band filtered. A sine wave having a frequency f, that is, a baseband reception monitoring signal is demodulated through the filter 163. The reception monitoring signal that is a demodulated sine wave of frequency f is input to the first phase comparator 11. Although details are not shown as the first synchronous demodulator 17, any known synchronous demodulator such as Costas Loop can be adopted.

  9 is configured as described above, the phase of the reception monitoring signal output from the bandpass filter 163 matches the phase of the reference signal output from the fixed frequency oscillator 10 (reference oscillator) in the transmission / reception device 100 of FIG. In this way, the phase of the transmission monitoring signal which is a sine wave of the frequency f output from the voltage controlled oscillator 13 (transmission monitoring signal oscillator) is advanced. The reference signal output from the fixed frequency oscillator 10 and the transmission monitoring signal output from the voltage controlled oscillator 13 are input to the second phase comparator 18.

The phase difference (second phase difference) of the transmission monitoring signal with respect to the reference signal is converted into a digital value by the A / D converter 19 and then read by the CPU 70. The processing procedure of the CPU 70 is the same as the procedure in which the second phase difference output from the second phase comparator 18 is processed as the phase φ in FIG. The second phase difference is a phase difference caused by a propagation delay time due to a round trip between the transmission / reception device 100 and the return device 200. If there is no change in the multipath environment around the vehicle body, the second phase difference does not change with time. For example, when a person approaches the vehicle, touches the door, or opens the door, the multipath environment between the transmission / reception device 100 and the return device 200 changes, so that the second phase difference is associated with time. To change. When it is determined that the change amount Δφ (step 106) of the second phase difference in the predetermined time interval T is greater than or equal to the threshold Th (step 108), an alarm signal is sent from the transmitter 71 to the receiver 72 owned by the vehicle owner. Sent to. Then, an alarm is displayed on the alarm device 73 and an alarm sound is output.
Further, since the double sideband waves (DSB (Nf) and DSB (Mf)) obtained by modulating the high frequency of the frequency Nf or the frequency Mf with the sine wave of the frequency f are used, the occupied band is extremely narrow.

  FIG. 10 is a block diagram illustrating a specific configuration of the transmission / reception device 101 and the reply device 201 according to the fifth embodiment of the present invention. The arrangement positions of the transmission / reception device 101 and the reply device 201 in the vehicle are the same as in the fourth embodiment.

  10 includes a reference oscillator 110 that oscillates a sine wave that is a reference signal having a single reference frequency f, a first reception antenna 120 that receives a transmission signal from the reply device 201, and amplifies the received signal. Amplifier 119, a first frequency converter 112 that converts the output signal of the amplifier into a reception monitoring signal that is a sine wave having the same frequency as the reference signal, and a phase of the sine wave of the reference signal output from the reference oscillator 110 And a first phase comparator 111 that compares the phase of the sine wave output from the first frequency converter 112. The transmission / reception apparatus 101 also integrates a loop filter 113 that integrates the first phase difference signal output from the first phase comparator 111, and a voltage-controlled oscillator 114 that changes the oscillation frequency according to the output voltage of the loop filter 113 ( A transmission monitoring signal transmitter), an amplifier 115 for amplifying the transmission monitoring signal that is the output thereof, and a first transmission antenna 118 for transmitting the output signal. Further, a second phase comparator 116 that compares the phase of the reference signal that is a sine wave output from the reference oscillator 110 with the phase of the transmission monitoring signal that is a sine wave output from the voltage controlled oscillator 114, and integrates the output thereof. And a low-pass filter 117.

  The second phase difference output from the second phase comparator 116 is converted into a digital value by the A / D converter 119 via the low-pass filter 117 and then read by the CPU 70. The processing procedure of the CPU 70 is the same as the procedure in which the second phase difference output from the second phase comparator 116 is processed as the phase φ in FIG. The second phase difference is a phase difference caused by a propagation delay time due to a round trip between the transmission / reception device 101 and the return device 201. If there is no change in the multipath environment around the vehicle body, the second phase difference does not change with time. For example, when a person approaches a vehicle, touches a door, or opens a door, the multipath environment between the transmission / reception device 101 and the return device 201 changes, and accordingly, the second phase difference is associated with time. To change. When it is determined that the change amount Δφ (step 106) of the second phase difference in the predetermined time interval T is greater than or equal to the threshold Th (step 108), an alarm signal is sent from the transmitter 71 to the receiver 72 owned by the vehicle owner. Sent to. Then, an alarm is displayed on the alarm device 73 and an alarm sound is output.

  The reply device 201 includes a second reception antenna 251 that receives the transmission monitoring signal transmitted from the transmission / reception device 101, and a second frequency converter 250 that converts the frequency of the signal received by the second reception antenna 251. Yes. In this embodiment, the first frequency converter 112 is a 1/10 frequency divider, and the second frequency converter 250 is a 10 × multiplier. In this embodiment, the reply device 201 is a device that simply converts the frequency and transmits it without demodulating the received signal into the baseband.

  Next, the operation of this apparatus will be described. In this embodiment, the reference signal output from the reference oscillator 110 is a sine wave having a frequency of 10 MHz. The transmission monitoring signal output from the voltage controlled oscillator 114 is also a sine wave having a frequency of 10 MHz. The return device 201 converts the frequency of the received transmission monitoring signal, which is a 10 MHz sine wave, into a 100 MHz sine wave, and outputs it from the second transmission antenna 252 to excite the vehicle body.

  In this way, in this apparatus, the feedback of the frequency and the phase is applied so that the first phase difference output from the first phase comparator 111 becomes zero, and is formed between the transmission / reception apparatus 101 and the reply apparatus 201. The one-round PLL is stable.

In this embodiment, the electromagnetic wave that excites the vehicle body by the transmission / reception device 101 has a single frequency of 10 MHz, and the electromagnetic wave that excites the vehicle body by the return device 201 has a single frequency of 100 MHz. It will be a thing. Further, since only frequency conversion is performed using only a single frequency, the circuit configuration becomes extremely simple.
In this way, it is possible to detect a change in the situation in the multipath environment between the transmission / reception device and the return device.

  FIG. 11 is a configuration diagram of the transmission / reception device 102 of the monitoring device according to the sixth embodiment of the present invention. The reference oscillator 310 is an oscillator that oscillates a 1 MHz square-wave reference signal S0. The reference signal S0 output from the reference oscillator 310 is input to the first phase comparator 311 and the second phase comparator 312. The second phase comparator 312 receives a transmission monitoring signal that is a transmission baseband signal B2 output from the voltage controlled oscillator 317. The transmission baseband signal B2 is a square wave that is frequency-synchronized with the reference signal S0 and phase-synchronized so that the phase difference becomes a predetermined value. The transmission baseband signal B 2 output from the voltage controlled oscillator 317 is input to the modulator (mixer) 318. The reference signal S0 output from the reference oscillator 310 is input to the PLL voltage controlled oscillator 319. The PLL voltage controlled oscillator 319 generates a sine wave obtained by multiplying the frequency of the reference signal S0 based on the reference signal S0 as a carrier wave. To do. This carrier wave is input to the modulator 318, and the carrier wave is amplitude-modulated by the modulator 318 by the transmission baseband signal B2. Then, the signal output from the modulator 318 is input to the bandpass filter 320, and only the upper sideband of the modulation signal is extracted. The output signal of the band pass filter 320 is amplified by the amplifier 322, and then input to the transmission antenna 321 as an excitation signal and radiated to the interior space of the vehicle. As a result, the vehicle body is excited by the electromagnetic wave generated by the excitation signal S2. Alternatively, the body may be directly excited by using the transmission antenna 321 as an excitation conductor directly attached to the vehicle body as in the first embodiment.

  The reply device has the same configuration as the reply device 200 shown in FIG. That is, the reply device 200 receives an electromagnetic wave from the vehicle body, demodulates it to a baseband transmission monitoring signal, and then outputs a reply signal S1 obtained by modulating a carrier wave having a frequency different from the transmission carrier wave with the signal. Is done. In the reply device 200, the body of the vehicle is excited by this reply signal. The reply signal S1 is received by the receiving antenna 330, and the received signal is amplified by the amplifier 331 and then input to the demodulator 333. The demodulator 333 is a synchronous demodulator, generates a demodulated carrier wave having a sine wave frequency synchronized with the carrier wave of the reply signal S1, and synchronously demodulates the reply signal S1 using the demodulated carrier wave. The output signal of the demodulator 333 passes through the band pass filter 334 and is input to the first phase comparator 312 as a reception baseband signal B1 that is a reception monitoring signal. The reception baseband signal B1 is a square wave, the same frequency as the transmission baseband signal B2, and a signal delayed by a predetermined phase.

  The first phase comparator 311 detects the first phase difference θ1 between the reception baseband signal B1 (reception monitoring signal) and the reference signal S0. The first phase difference θ1 is defined as the phase of the received baseband signal B1 minus the phase of the reference signal. That is, it is the phase of the received baseband signal B1 when the phase of the reference signal is 0 degree. A negative value of θ1 represents a delayed phase. The first phase comparator 311 includes a flip-flop circuit as is well known. A pulse signal having a width proportional to the phase difference of the received baseband signal B1 with respect to the reference signal S0 is output. When the reception baseband signal B1 and the reference signal S0 are in phase, the output of the first phase comparator 311 is a square wave with a duty ratio of 50%, and the reception baseband signal B1 is only π with respect to the reference signal S0. When the phase is advanced, a square wave with a duty ratio of 100% (high level direct current) is obtained, and when the received baseband signal B1 is delayed in phase by π with respect to the reference signal S0, the duty ratio is 0. % Square wave (low level direct current). The output signal of the first phase comparator 311 is input to a low-pass filter (loop filter) 314 and is smoothed (averaged). The output level of the low-pass filter 314 gives the first phase difference θ1. The reception baseband signal B1 is always delayed in phase with respect to the reference signal S0. Therefore, the first phase difference θ1 is a negative value. Therefore, in the inverter 316, the signal level is inverted, and the absolute value of the first phase difference θ1 is obtained. That is, the output signal of the inverter 316 gives the absolute value (−θ1) of the first phase difference.

  Similarly, the second phase comparator 312 receives the reference signal S0 and the transmission baseband signal B2 (transmission monitoring signal). The second phase comparator 312 has the same configuration as the first phase comparator 311 and performs the same function. Therefore, when the transmission baseband signal B2 and the reference signal S0 are in phase, the output of the second phase comparator 312 is a square wave with a duty ratio of 50%, and the transmission baseband signal B2 is compared with the reference signal S0. When the phase is advanced by π, a square wave with a duty ratio of 100% (high level direct current) is obtained, and when the transmission baseband signal B2 is delayed by π with respect to the reference signal S0, the duty is It is adjusted to be a square wave (low level direct current) with a ratio of 0%. The output signal of the second phase comparator 312 is input to a low-pass filter (loop filter) 315 and is smoothed (averaged). The output level of the low-pass filter 315 gives the second phase difference θ2. The transmission baseband signal B2 always advances in phase with respect to the reference signal S0. Therefore, the second phase difference θ2 is a positive value. For this reason, the output level of the low-pass filter 315 gives the absolute value (θ2) of the second phase difference θ2.

The absolute value (−θ1 ≧ 0) of the first phase difference and the absolute value θ2 of the second phase difference are input to the comparator 313. The output of the comparator 313 calculates the phase difference Δθ of the absolute value of the first phase difference with respect to the absolute value of the second phase difference.
The output signal of the comparator 313 is input to the control terminal of the voltage controlled oscillator 317 (transmission monitoring signal transmitter). When the phase difference Δθ is positive, feedback control is performed so that the phase of the transmission baseband signal B2 output from the voltage controlled oscillator 317 is advanced and the output Δθ of the comparator 313 becomes zero. When Δθ is negative, feedback control is performed so that the phase of the transmission baseband signal B2 output from the voltage controlled oscillator 317 is delayed and the output Δθ of the comparator 313 becomes zero. In this way, the phase of the transmission baseband signal B2 is controlled so that the phase difference Δθ that is the output of the comparator 313 is always zero. That is, PLL synchronization is established between the transmission / reception device 102 and the reply device 200 with respect to the baseband signal.

In a state where PLL synchronization is established, the phase difference Δθ that is the output of the comparator 313 is zero.
That is, the absolute values of the first phase difference θ1 and the second phase difference θ2 are equal.

  The second phase difference θ2 output from the second phase comparator 312 is converted into a digital value by the A / D converter 319 via the low-pass filter 315 and then read by the CPU 70. The processing procedure of the CPU 70 is the same as the procedure in which the second phase difference θ2 output from the second phase comparator 312 is processed as the phase φ in FIG. The second phase difference θ <b> 2 is a phase difference caused by a one-way propagation delay time between the transmission / reception device 102 and the return device 200. If there is no change in the multipath environment around the vehicle body, the second phase difference does not change with time. For example, when a person approaches the vehicle, touches the door, or opens the door, the multipath environment between the transmission / reception device 102 and the return device 200 changes, so that the second phase difference θ2 is reduced according to the time. Changes. When the change amount Δφ (step 106) of the second phase difference θ2 in the predetermined time interval T is determined to be equal to or greater than the threshold Th (step 108), an alarm signal is transmitted from the transmitter 71 to the receiver 72 owned by the vehicle owner. Sent to. Then, an alarm is displayed on the alarm device 73 and an alarm sound is output. As the time change of the phase difference, the time change of the first phase difference θ1 may be detected.

The monitoring apparatus according to the seventh embodiment is a monitoring apparatus according to the fourth embodiment, in which a PLL is not applied to a monitoring signal in a circuit of a transmission / reception apparatus, a reply apparatus, and a transmission / reception apparatus.
In FIG. 12, the reference signal output from the reference signal oscillator 10 is a transmission monitoring signal. The carrier wave is modulated (frequency converted) by this transmission monitoring signal and output as an excitation signal. The phase comparator 11 receives a reception monitoring signal obtained by demodulating the reception signal and a transmission monitoring signal that is a reference signal. The output of the phase comparator 11 indicates the phase difference between the reception monitoring signal and the transmission monitoring signal. This phase difference is caused by the propagation delay time due to a round path of the transmission / reception device, the return device, and the transmission / reception device. This phase difference is converted into a digital value by the A / D converter 19 and read by the CPU 70. The processing procedure of the CPU 70 is the same as that in the first embodiment shown in FIG.

  In this way, the phase difference between the transmission monitoring signal and the reception monitoring signal can be detected, and when the temporal change amount of the phase difference is equal to or greater than a predetermined threshold, the change in the multipath environment, that is, Abnormalities such as the approach of a person to the vehicle can be detected.

  In the case of Example 4-7 using a transmission / reception device and a return device, both the transmission / reception device 100 and the return device 200 may be provided on the outer surface of the vehicle body. And the transmission / reception apparatus 100 may be provided in one place, and the several reply apparatus 200 may be provided in many places of the outer surface of a body. In this case, the frequency of the reply signal may be changed for each reply device 200 and the signal may be received by each reply device 200 in the transmission / reception device 100 by switching the frequency. As described above, by using a plurality of reply devices 200, it is possible to monitor surrounding abnormalities over a wide range of the body. Also, instead of assigning different frequencies to each reply device 200, different spread codes may be assigned and this spread code may be used as a baseband monitoring signal unique to each reply device.

FIG. 14 shows the simulation result of the electromagnetic field when the vehicle body is excited with 300 MHz electromagnetic waves. It can be seen that there is an electromagnetic field in the space around the body. And when a dielectric is provided around, it turns out that the surrounding electromagnetic waves are disturbed. Thereby, when a person approaches a vehicle, it turns out that the multipath environment between a transmission device and a reception device and between a transmission / reception device and a reply device changes.
FIG. 15 shows a simulation result of the electromagnetic field when the vehicle body is excited by 60 MHz electromagnetic waves. In this case, it can be seen that the electromagnetic field is constrained by the vehicle body and hardly exists in the vicinity. Thus, it can be seen that when the body is excited at 60 MHz, an evanescent wave that does not propagate to the periphery is excited. This evanescent wave can be detected by a receiving device and a transmitting / receiving device, and when a person or the like approaches the vehicle, the electromagnetic field due to the evanescent wave is affected and changes. This change in the electromagnetic field can be detected as a temporal change in the phase difference between the transmission monitoring signal and the reception monitoring signal.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a monitoring device that can detect the approach, contact, door opening, etc. of an outsider to a vehicle and prevent the vehicle from being stolen.

DESCRIPTION OF SYMBOLS 1 ... Monitoring apparatus 20 ... Detection conductor 30 ... Quadrature demodulator 32 ... Phase comparator 40 ... Frequency difference calculating circuit 42, 46 ... Comparator 43, 44 ... AND circuit 60 ... Pulse oscillator 66 ... Target phase setting register 11 ... 1st Phase comparator 18 ... second phase comparator

Claims (17)

In a monitoring method for monitoring the periphery of a vehicle,
The body of the vehicle is excited by an electromagnetic wave generated by a monitoring signal output from a transmitting device, thereby forming a multipath of the electromagnetic wave between the transmitting device and the receiving device, and the phase of the monitoring signal received by the receiving device The vehicle monitoring method is characterized in that an alarm is issued when an abnormality occurs in the vicinity of the vehicle when the phase changes.   The receiving device is installed on an outer surface of the body, and the body is excited by the transmitting device by supplying an excitation current directly to the body of the vehicle. The vehicle monitoring method described in 1.   The receiving device is installed on an outer surface of the body, and excitation of the vehicle body by the transmitting device is performed by electromagnetic waves radiated from an antenna provided in an internal space of the vehicle. The vehicle monitoring method according to claim 1. On the outer surface of the body, a return device that receives the monitoring signal by the electromagnetic wave and transmits the monitoring signal whose frequency is converted is installed,
2. The vehicle monitoring method according to claim 1, wherein the receiving device receives a monitoring signal having a frequency converted from the reply device. 3. In a monitoring device that monitors the periphery of a vehicle,
A transmission device for exciting the vehicle body with an electromagnetic wave generated by a monitoring signal;
The vehicle is arranged at a position where a multipath of electromagnetic waves is interposed between the transmitter and the vehicle body, receives the monitoring signal, and the phase of the monitoring signal changes. A vehicle monitoring device comprising: a receiving device that outputs an alarm when an abnormality occurs around the vehicle.   6. The receiving device is installed on an outer surface of the body, and the body is excited by the transmitting device by directly supplying an exciting current to the body of the vehicle. The vehicle monitoring device described in 1. The receiving device is installed on the outer surface of the body,
The vehicle monitoring device according to claim 5, wherein the transmission device includes an antenna that is provided in an internal space of the vehicle and radiates an electromagnetic wave that excites the body of the vehicle. A return device that is installed on the outer surface of the body, receives the monitoring signal by the electromagnetic wave, and transmits the monitoring signal whose frequency is converted;
6. The vehicle monitoring device according to claim 5, wherein the receiving device receives a monitoring signal having a frequency converted from the reply device. The receiving device is:
A phase detector for detecting the phase of the received monitoring signal;
A phase change amount judging means for judging whether or not a phase change amount with respect to elapse of time of the phase detector is equal to or more than a threshold
When the phase change amount determining means determines that the phase change amount is greater than or equal to a threshold value, an alarm device that outputs an alarm that an abnormality has occurred around the vehicle;
The vehicle monitoring device according to claim 5, further comprising: The receiving device is:
According to the control signal, a target frequency is set and a target frequency setting register for setting and storing the target frequency and a target phase setting register for setting and storing the target phase are set according to the control signal. A reference signal oscillator that outputs a reference signal having a frequency and phase that match the target frequency set in the register and the target phase set in the target phase setting register;
A phase comparator that outputs a phase difference signal indicating a phase difference between the monitoring signal and the reference signal output from the reference signal oscillator;
A frequency for determining the frequency difference between the monitoring signal and the reference signal from the time variation of the phase difference signal output from the phase comparator and controlling the target frequency of the reference signal oscillator based on the frequency difference A control device;
A phase control device that controls the target phase of the reference signal oscillator based on the phase difference indicated by the phase difference signal output by the phase comparator;
Have
The said phase detector detects the said target phase set to the said target phase setting register as a phase of the said monitoring signal in the period when the said monitoring signal is detected. Vehicle monitoring device. The receiving device is:
Configure a transmitting / receiving device together with the transmitting device;
A phase difference detector for detecting a phase difference between a transmission monitoring signal output from the transmission device and a reception monitoring signal obtained by receiving and demodulating the transmission signal from the reply device;
Phase difference change amount determining means for determining whether or not the amount of change with time of the phase difference output by the phase difference detector is equal to or greater than a threshold;
When the phase difference change amount determining means determines that the amount of change in the phase difference is equal to or greater than a threshold value, an alarm device that outputs an alarm that an abnormality has occurred around the vehicle;
The vehicle monitoring device according to claim 8, comprising: The receiving device constitutes a transmitting / receiving device together with the transmitting device,
The transmission / reception device includes:
A reference signal oscillator for oscillating a reference signal;
A first phase difference detector for detecting a first phase difference between the reference signal output from the reference signal oscillator and a reception monitoring signal obtained by receiving and demodulating a transmission signal from the return device;
A transmission monitoring signal oscillator for controlling the frequency and phase of the transmission monitoring signal so that the first phase difference output from the first phase difference detector becomes zero;
A second phase difference detector for detecting a second phase difference between a reference signal output from the reference signal oscillator and a transmission monitoring signal output from the transmission monitoring signal oscillator;
Phase difference change amount determination means for determining whether or not the amount of change of the second phase difference output from the second phase difference detector with respect to the passage of time is equal to or greater than a threshold;
An alarm device that outputs a warning that an abnormality has occurred around the vehicle when the phase difference change amount determining means determines that the change amount of the second phase difference is equal to or greater than a threshold;
The vehicle monitoring device according to claim 8, comprising: The receiving device constitutes a transmitting / receiving device together with the transmitting device,
The transmission / reception device includes:
A reference signal oscillator for oscillating a reference signal;
A first phase difference detector for detecting a first phase difference between the reference signal output from the reference signal oscillator and a reception monitoring signal obtained by receiving and demodulating a transmission signal from the return device;
A second phase difference detector for detecting a second phase difference between the reference signal output from the reference signal oscillator and the transmission monitoring signal output from the transmission device;
A comparator that outputs a difference in absolute value between the first phase difference and the second phase difference;
A transmission monitoring signal oscillator that controls the frequency and phase of the transmission monitoring signal so that the output of the comparator becomes zero;
Phase difference change for determining whether a change amount of the first phase difference output from the first phase difference detector or the second phase difference output from the second phase difference detector with respect to time is equal to or greater than a threshold value. A quantity determination means;
An alarm device that outputs an alarm that an abnormality has occurred around the vehicle when the change amount of the first phase difference or the second phase difference is determined to be greater than or equal to a threshold value by the phase difference change amount determination means When,
The vehicle monitoring device according to claim 8, comprising:   The control signal is an addition / subtraction pulse that increases or decreases the target frequency and the target phase by a unit amount, the reference signal oscillator is a digital synthesizer, and the target frequency setting register and the target phase setting register are the addition / subtraction pulses The monitoring device according to claim 10, wherein the monitoring device is a register that increases or decreases the target frequency and the target phase based on the target frequency.   The control signal is a signal indicating an absolute value of the target frequency and the target phase, the reference signal oscillator is a digital synthesizer, and the target frequency setting register and the target phase setting register receive the control signal. The monitoring apparatus according to claim 10, further comprising a register that sets an absolute value indicated by a control signal as the target frequency and the target phase each time the control signal is displayed.   5. The frequency of the electromagnetic wave that excites the body of the vehicle by the transmission device is a frequency that excites an evanescent set wave on the surface of the body. 6. Vehicle monitoring method.   The frequency of the electromagnetic wave that excites the body of the vehicle by the transmission device is a frequency that excites an evanescent wave on the surface of the body. Vehicle monitoring device.