JP6663240B2 - Multi line sensor - Google Patents

Description

  The present invention relates to a multi-line sensor, and more particularly to an opposed-type line sensor for monitoring between a transmitter and a receiver using microwaves.

Conventional opposed-type line sensors construct a radio transmission / reception line in which a transmitter and a receiver are opposed to each other at a predetermined distance, and detect a decrease in reception power on the receiver side, etc. This is to determine a state in which the transmission / reception line is cut off, for example, when an object such as a person or a car that attenuates microwaves enters.
Usually, this type of line sensor is composed of a device that generates and transmits microwaves and a device that receives the microwaves, and often uses ASK (Amplitude-Shift keying) modulated waves for radio waves. As the microwave frequency band, the 10 GHz band is the mainstream overseas, but the domestic radio law does not permit the use of the 10 GHz band outdoors, so it is necessary to use the 24 GHz band.
As a method of detecting a transmission wave level in a receiver, there is a method of using a frequency detector, a method of performing FFT (Fast Fourier Transform) processing on a received signal, and detecting a change in a received power value.

JP 2009-99020 A

By the way, the conventional line sensor has the following problems.
1. Depending on the installation environment, for example, the conditions of snowfall, falling leaves and weeds, etc., it is easily affected by the height pattern, and it is difficult to maintain the performance for a long time. The height pattern is a phenomenon in which received power fluctuates due to cancellation or superposition of phases due to radio waves directly reaching the antenna and radio waves reflected on the ground or the like and reaching the antenna.

FIG. 10A shows the configuration of a line sensor. For example, a transmitter 51 and a receiver 52 are arranged at intervals of several meters to several hundred meters, but the ground position at the time of installation is E0. On the other hand, when the ground position becomes E1 in an environment such as rainfall, snowfall, fallen leaves, or growth of weeds, the relative ground height changes, and the reflection of the transmitted radio wave from the ground changes from a solid line to a dotted line. .
To avoid this phenomenon, it is necessary to reduce the radiation angle of the antenna or increase the height above the ground.However, when the radiation angle of the antenna is reduced, the antenna becomes larger and the outer shape becomes larger. And cost problems arise. In addition, when the ground height is increased, an area where no detection is performed (dead zone) increases, and it becomes difficult to obtain a function as a sensor.

2. Since the system of the receiver is broadband diode detection, it is affected by extraneous waves, causing false alarms and unavoidably affected by radio wave interference. Also, simultaneous use of multiple frequencies is not possible.

3. When a 24 GHz band is used as the operating frequency, the monitoring range becomes narrow because the Fresnel zone of the radio wave is narrow. The Fresnel zone is a region that connects a transmitter (transmitting antenna) and a receiver (receiving antenna) with a straight line and has a small power loss.
FIG. 10B shows a Fresnel zone, which is the thickest in the middle part between transmission and reception, and tends to become thinner as it approaches the transmitter (antenna) 51 and the receiver (antenna) 52. The thickness d differs depending on the frequency, and increases as the frequency of the carrier decreases. For example, in the 24 GHz band, when the distance between transmission and reception is 100 m, the thickness d is about 1 m (about 0.5 m in radius) near the center as shown in the figure, and when 50 m, the diameter d is about 0 m near the center. 0.8 m (radius about 0.4 m).
Therefore, when a transceiver is installed at a height of 1 m above the ground with a line sensor in the 24 GHz band, as shown in FIG. 10B, a dead zone G of 0.5 m is generated with respect to the Fresnel zone. Becomes larger as it approaches the transmitting / receiving antenna end.

  The present invention has been made in view of the above problems, and its purpose is to prevent the function of the monitoring system from being impaired even when affected by the height pattern, and to eliminate the dead zone due to the narrow Fresnel zone. It is another object of the present invention to provide a multi-line sensor that can eliminate false reports and the like without using diode detection that is easily affected by extraneous waves.

In order to achieve the above object, a multi-line sensor according to the first aspect of the present invention includes a forward-direction transceiver in which a transmitter and a receiver face each other, and a transmission-reception direction which is arranged on the same line as the forward-direction transceiver. And a plurality of pairs of forward and backward transceivers are arranged on the lines having different heights, and the forward and backward transceivers and the backward direction of each pair are arranged. transceiver to transmit and receive signals of different frequencies respectively, a sensor for monitoring an object to block the signal transmitted between the transmitter and the receiver of the plurality of pairs, the forward transceivers and reverse transceiver of each pair In order to distinguish between the received signal and the image signal, a set frequency range is provided for each line, and each of the forward and backward transceivers receives only the frequency transmitted from the transmitter on the same line. While signal, between the operating frequency of the positive direction transceiver operating frequency and the reverse transceiver, the image signal is set to the offset frequency for preventing entering the set frequency range of each said line It is characterized by .

The invention according to claim 2 is an oscillator that oscillates a reference frequency, a PLL circuit that outputs a frequency signal used for each pair of transceivers based on the output of the oscillator, a reception signal from the receiver, and the PLL circuit. a mixer for mixing the local oscillation signal obtained on the basis, characterized by a Turkey and a frequency analysis circuit for analyzing the received frequency from the output of the mixer.
The invention according to claim 3, in transceiver of each pair, by verify reception frequency obtained from the frequency analysis circuit, if the frequency shift occurs, for outputting the correction data to said PLL circuit, The transmission frequency of each pair of transceivers is corrected and updated.

  According to the above configuration, a plurality of transmitters and receivers are arranged on lines having different heights, with a pair of transmitters and receivers arranged opposite to each other. It is configured to transmit and receive, and surface monitoring becomes possible by such arrangement of a plurality of lines. Further, assuming that the transmitting and receiving direction by the transceiver is a forward direction, the transceivers that transmit and receive in the reverse direction are arranged on the same height line, and signals of different frequencies are used in all the forward and reverse transceivers. The number of monitoring lines can be further increased.

In the reception of each pair of transceivers, the reception signal is determined based on the set frequency range (Fk) for each line set for each pair, and further, the frequency used in the forward transceiver group and the reverse transceiver group are used. The offset frequency (Fof) for preventing the image signal from entering the set frequency range for each line is set between the used frequencies.
Further, as described above, when monitoring using different frequencies in each of a plurality of pairs of transceivers, depending on the stability of the transmission and reception frequencies, it becomes susceptible to extraneous waves and the like, making monitoring of multiple lines difficult. It happens. Therefore, at the time of reception of each pair of transceivers, the respective reception frequencies are checked, and if there is a frequency shift, correction data is output to the PLL circuit, so that the transmission frequency of each pair of transceivers is output. Has been corrected and updated.

  According to the present invention, the transmission and reception of a plurality of lines having different heights does not impair the function of the monitoring system even if it is affected by the height pattern, making it possible to eliminate the dead zone due to the narrow Fresnel zone, Erroneous reports, unreported reports, etc. can be eliminated without using diode detection which is easily affected by the above.

In addition, by setting a set frequency range for each line for determining a received signal and an offset frequency between a frequency used in the forward direction transceiver group and a frequency used in the reverse direction transceiver group, the influence of the image signal is reduced. Can be eliminated.
Furthermore, by checking the receiving frequency with each pair of transceivers and correcting the frequency shift, the frequency used by each pair of transceivers can be adjusted even if the operating frequency fluctuates due to temperature conditions, installation environment, and aging. As set, the detection sensitivity can be maintained satisfactorily.

FIG. 1 is a side view illustrating the overall configuration of a multiline sensor according to an embodiment of the present invention. FIG. 2 is a side view illustrating a configuration of two upper lines of the multi-line sensor of FIG. 1. FIG. 4 is a diagram for explaining a transmission / reception state in the multiline sensor according to the embodiment. FIG. 2 is a block diagram illustrating a circuit configuration of the multi-line sensor according to the embodiment. FIG. 4 is an explanatory diagram showing frequencies set by each pair of transceivers constituting the multi-line sensor of the embodiment. FIG. 5 is a diagram for explaining a set frequency range, a frequency offset, and the like for each line set by the multi-line sensor according to the embodiment. It is a flowchart figure which shows the operation | movement of the frequency adjustment in an Example. It is a side view which shows the structure when increasing a monitoring system in an Example. FIG. 3 is a diagram for explaining frequency adjustment performed in each system of the embodiment. FIG. 9 is a diagram for explaining a transmission / reception state in a conventional opposed line sensor.

  1 and 2 show the configuration of the multi-line sensor (multi-line monitoring device) according to the embodiment. As shown in FIG. 1, the multi-line sensor transmits a signal of frequency f1 as group A. A sensor unit F1, a sensor unit F2 transmitting a signal of a frequency f2, a sensor unit F3 transmitting a signal of a frequency f3, a sensor unit F4 transmitting a signal of a frequency f4, a sensor unit F5 transmitting a signal of a frequency f5, a group As B, a sensor unit F6 transmitting a signal of frequency f6, a sensor unit F7 transmitting a signal of frequency f7, a sensor unit F8 transmitting a signal of frequency f8, a sensor unit F9 transmitting a signal of frequency f9, and a sensor unit F9 of frequency f10 A sensor unit F10 for transmitting a signal is provided. The sensor units F1 and F6, F2 and F7, F3 and F8, F4 and F9, and F5 and F10 are arranged on lines having the same height. Each of the sensor units F1 to F10 includes a transmitter for transmitting the signal and a receiver for receiving in the direction opposite to the transmission direction. That is, each of the sensor units F1 to F5 of the group A transmits a signal from the right to the left (reverse direction) of the figure together with the transmitter for transmitting from left to right (representing the forward direction) in the figure. Each of the sensor units F6 to F10 of the group B includes a transmitter for transmitting in the reverse direction and a receiver for receiving in the forward direction.

  FIG. 2 shows the configuration of the upper two lines. As shown, the sensor unit F1 is provided with a transmitter 1t for transmitting the frequency f1 and a receiver 6r for receiving the frequency f6. The sensor unit F6 on the same line is provided with a receiver 1r for receiving the frequency f1 and a transmitter 6t for transmitting the frequency f6, and transmits the frequency f2 to the sensor unit F2 on the line below. A transmitter 2t and a receiver 7r for receiving the frequency f7 are provided, and a sensor unit F7 on the same line is provided with a receiver for receiving the frequency f2 and a transmitter 7t for transmitting the 2r frequency f7. . The transmitters 1t and 2t and the receivers 1r and 2r perform forward transmission and reception, and the transmitters 6t and 7t and the receivers 6r and 7r perform reverse transmission and reception.

  FIG. 3 shows a state of transmission / reception by two lines of transceivers having different heights. When the transceivers are provided on lines having different heights, as shown in FIG. Even if the ground position changes from E0 to E1 in an environment such as snowfall, falling leaves, or the growth of weeds, and the reception by the transceivers 2t and 2r is affected by the height pattern, the transceivers 1t and 1r have no effect. This makes it possible to detect an object (a person, a car, or the like) between the transmitter and the receiver. When the frequency is in the 24 GHz band, the degree of influence varies greatly with a difference of about several cm, but if a transceiver is installed on a plurality of lines of different heights, object detection (object blocking state) cannot be performed due to the effect of the height pattern. Nothing.

  Further, as can be seen from a comparison between FIG. 3B and FIG. 10B, by monitoring the surface with a plurality of lines, the dead zone G can be reduced. That is, since an object such as a person or a car is sensed not by any one line but by a plurality of lines at the same time, the presence or absence of the object can be reliably detected.

  FIG. 4 shows a circuit block of the embodiment, in which reference numeral 4 denotes a temperature-compensated crystal oscillator (TCXO) having high stability, 5 denotes a PLL (Phase Locked Loop: phase locked oscillator) unit, and 6 denotes a phase locked oscillator. This is a VCO (Voltage Controlled Oscillator), and the embodiment uses a fractional frequency division PLL (Fractional PLL) method. Reference numeral 7 denotes an amplifier, 8 denotes a distributor, 9a and 9b denote amplifiers, 10 denotes an LPF (low-pass filter), 12a denotes a transmitting antenna (TX), 12b denotes a receiving antenna (RX), 13 denotes an amplifier, and 14 denotes an amplifier 9b output. Mixer (for example, an image rejection mixer) that mixes the LO signal (local signal) and the RF signal output from the amplifier 13 to obtain an I signal and a Q signal, 15a and 15b are IF (intermediate frequency) amplifiers, and 17a and 17b are EVRs. (Electronic volume), 18a and 18b are IF amplifiers, 20 is a signal processing unit (micro control unit) having an A / D conversion unit, FFT (fast Fourier transform) processing unit, and determination processing unit.

  FIGS. 5 and 6 show the relationship between the frequencies assigned by the sensor units F1 to F10. The signals transmitted by the sensor units F1 to F10 are formed by the circuit of the LPF 10 from the crystal oscillator 4 and output from the transmission antenna 12a. These frequencies are as shown in FIG. That is, the frequencies f1 to f5 of the group A (sensor units F1 to F5) and the frequencies f6 to f10 of the group B (sensor units F6 to F10) are assigned with a channel interval (frequency) Fs, respectively. An offset frequency Fof is set between A and B. Note that the channel interval Fs is set to a value that does not exceed the adjacent channel frequency even when the sensor is affected by temperature fluctuations and aging due to the performance of the oscillator mounted on each sensor unit.

  As shown in FIG. 6A, in the embodiment, a set frequency range Fk is provided for each transmission / reception line. When receiving multiple frequencies at the same time, unnecessary frequencies such as image signals and cross modulation may occur.In order to distinguish the image wave from the original received wave in the received signal, The set frequency range Fk is provided as a determination width for each.

Further, the reception frequency is always set within the range of the set frequency range Fk, and the frequency control (in order to maintain the performance by discriminating the inter-modulation in the reception of a plurality of frequencies or the unexpected external wave from the original reception wave and maintaining the performance). It is necessary to perform AFC (Automatic Frequency Control). In the embodiment, as one of them, an offset frequency Fof is provided between the groups A and B, and the image signal generated from the mixer 14 enters the set frequency range Fk for each line. Not to be.
That is, the offset frequency Fof is a value smaller than the channel interval Fs. As shown in FIG. 6B, when the relationship between the sensor units F3 and F8 is described, 1/2 of Fs and the set frequency range Fk are set. The value falls within the avoided ranges Wa and Wb. In formula, the offset frequency Fof is a value satisfying (Fs / 2) + (Fk / 2 or more) when Fof <Fs.

FIG. 6 (C) shows an image signal received by the receiver. As shown, the image signal from the mixer (image rejection mixer) 14 has opposite positive and negative frequencies with respect to DC (zero). And its magnitude differs depending on the IQ phase difference and the amplitude difference of the mixer 14.
Therefore, in the embodiment, by giving the frequency offset Fof for each group, the image signal by the mixer 14 in the IF band of the receiver is prevented from overlapping the reception frequency (set frequency range Fk) of each line.

  According to the above configuration, by using the mixer 14, when the frequency received with respect to the local oscillation signal frequency Flo of the receiver is the same, the IF output signal of the receiver becomes DC (zero) and the input frequency becomes If it is high with respect to the Flo of the receiver, it is output in the positive direction (plus side frequency), and if it is low, it is output in the negative direction (negative side frequency).

  Referring to FIGS. 5 and 6B, for example, when the sensors F1 to F4 are viewed from the sensor unit F8, the frequencies f1, f2, and f3 are lower than the frequency f8 (negative frequency), and the frequencies f4 and f5 are the frequencies f8. As shown in FIG. 6B, the frequency of the line from the sensor F8 to the sensor F1 is Fof + Fs + Fs, and the frequency f1 is lower than the frequency Flo and is located on the minus side frequency. On the other hand, the frequency of the line from the sensor F8 to the sensor F5 is Fs-Fof + Fs, and the frequency f5 is higher than Flo and is a plus side frequency. Such a frequency relationship can be easily determined by subjecting the IF output signal obtained by each sensor unit to FFT conversion in the signal processing circuit 20 and frequency decomposition.

  When it is desired to increase the number of monitoring lines as in the above embodiment, the smaller the channel interval Fs, the better, and it is necessary that the transmitter and the receiver have frequency stability. Generally, the frequency stability is affected by aging, temperature fluctuation, initial deviation, and the like, and these effects cannot be avoided by using any oscillator. In consideration of the cost and the scale of the device, the IF frequency must be kept within several MHz, and maintaining and controlling the frequency in the 24 GHz band is a difficult task due to the frequency ratio.

Further, as described above, in the embodiment, a fractional frequency-divided PLL is used as a PLL method.
When a PLL circuit is used in the configuration of the oscillator, the frequency deviation is several PPM, but in the 24 GHz band, 1 PPM is a relatively large value of 24 kHz.
When the line is determined by the frequency, there must be no frequency fluctuation exceeding each set frequency range Fk. Therefore, it is necessary to consider the frequency stability of the device, the channel interval Fs, and the IF bandwidth of the receiver. . As a method of stabilizing the frequency, there is a method of using a high-stability temperature-controlled crystal oscillator (OCXO: with a constant temperature bath), but in consideration of size and cost, and within a limited IF frequency band. For the purpose of configuring many lines, a fractional frequency division PLL using a temperature compensated crystal oscillator (TCXO) is adopted.
According to the fractional frequency division PLL, the frequency can be set in small steps, and the frequency can be controlled in steps of about 100 Hertz in the 24 GHz band.

In the embodiment, the following frequency management is performed to increase the accuracy of the frequency.
In other words, many monitoring sensors are installed outdoors or the like, and it is difficult to manage the absolute frequency after shipment or installation, and it is not possible to deviate from the band specified by the Radio Law by performing frequency correction. Since it is not allowed, it is necessary to manage the set initial frequency and the frequency correction value known in advance. Therefore, in the embodiment, the following is performed.
1. Adjustment at the time of factory shipment: Make the deviation of the frequency of each sensor unit zero or close to zero.
That is, in the manufacturing process of the multi-line sensor, the sensor frequency is adjusted to the absolute frequency (zero adjustment) by using a calibrated external measuring device, and the machine difference correction value is stored in the sensor.
2. When operating the multi-line sensor: When the frequency shifts, the frequency step of the PLL is automatically updated so that the frequency always becomes as set (AFC).
In order to change the frequency, an instruction to change the numerator variable of the fractional frequency division PLL in the PLL unit 5 is issued from the signal processing circuit 20 in accordance with the frequency shift.

  FIG. 7 shows the operation at the time of operation. In step 101 of FIG. 7, the reception frequency is analyzed by the FFT unit of the signal processing circuit 20, and in step 102, the analyzed reception frequency and setting / storage are stored. In step 103, it is determined whether the received frequency is the same as the set frequency. If there is a difference in the frequency, the received frequency is set to the set frequency. adjust. The above operation is performed in the signal processing circuit 20, and the signal processing circuit 20 supplies a frequency correction value to the PLL unit 5. In other words, after shipment, judgment is made based on the relative frequency, and even if the reception frequency changes due to temperature conditions, installation environment, and aging, the reception frequency does not always fluctuate by linking the PLL setting data accordingly. In addition, a limit (limit) is provided for the frequency correction value, and when the amount of fluctuation is abnormally large, it is determined that the device has failed.

The frequency correction by the PLL unit 5 is, for example, when the frequency correction value from the signal processing circuit 20 is D, this D is obtained by D = Δf / fsmin, and the frequency correction is performed by fnum ± D. Here, Delta] f: the difference between the original frequency determined from the FFT ^{_{unit, fsmin = F TCXO / 2 18}} [fsmin: amount of change per 1fnum (fnum: a PLL frequency resolution, the minimum frequency step indicates the size) is .

By performing such frequency correction, it is possible to keep the frequency obtained by performing the FFT processing on the received signal constant. With such a function, the correlation between a plurality of frequencies and the line is broken, and the presence or absence of an object in the line is detected. So that it does not interfere with the judgment of
Therefore, according to the present invention, by providing control from the signal processing side by register control of the PLL without providing a special frequency determination circuit, it is possible to realize an advanced monitoring sensor with good sensitivity and cost. There is an advantage that an advantageous sensor can be obtained in terms of surface.

  Note that the received signal includes cross modulation in the received signal in addition to the IQ image generated by the mixer 14. However, since the multiline sensor itself handles a very small received signal, an integer multiple of spurious signal is not generated. However, in the case of installation at a very short distance or the like, a phenomenon that may theoretically occur may occur. Therefore, under such installation conditions, another measure such as lowering the transmission power is required. It has been confirmed that the above problem does not occur when the transmission / reception distance is 10 m to 100 m.

Further, in the embodiment, as shown in FIG. 8, the system (FIG. 5) composed of the sensors F1 to F10 can be used as the system 1, and the number of systems 2, 3,.
However, in this case, since radio wave interference with other multi-line sensor groups is expected, frequency management is performed by dividing the frequencies. For example, when the system 1 and the system 2 are installed adjacent to each other, the radio waves reach beyond the line range of each other, so that the receiver of the system 2 also receives the transmission signal of the system 1. In 2, the operation is performed while changing the frequency.

In the embodiment, the frequency of each system group is adjusted.
Since each of the sensor units F1 to F10 has a frequency adjusting function, if the frequency adjustment is performed by all the opposing sensors, an infinite loop may occur and the frequency may not be determined. Therefore, the system group is provided with a function of adjusting the frequency of one of the opposing ones according to the other, or determining the reference device (master) and adjusting the frequency according to the reference device.

FIG. 9A shows a frequency adjustment for adjusting the group A to the group B (or vice versa). For example, the frequency of the frequency (transmission frequency) f1 of the sensor unit F1 and the frequency (transmission frequency) f6 of the sensor unit F6 are adjusted. Similarly, the relative relationship between the frequencies F2 and F7, F3 and F8, F4 and F9, and F5 and F10 is adjusted.
FIG. 9 (B) shows an example in which the reference device is determined and the frequency is adjusted. For example, the sensor unit F1 is used as the reference device, and the frequencies (transmission frequency) of the sensor units F6 to F10 and the frequency (transmission frequency) of F1 are adjusted first. Thereafter, the frequencies of F2 to F5 are matched with the frequencies of the opposite F7 to F10. As a result, all the sensor units in the system are adjusted to the frequency of F1.

  In the above-described embodiment, the sensor unit is set to five opposing lines. However, if it is within the limit of the frequency band of the IF signal processing (within the limit of the IF frequency bandwidth of the receiver, the FFT sample for IF processing, the Nyquist frequency, etc.). In addition, it is possible to further increase the number of lines of the sensor unit facing each other.

1t, 2t ... transmitter, 1r, 2r ... receiver,
4 temperature-compensated crystal oscillator 5 PLL section
6 ... VCO, 10 ... LPF,
14: mixer, 20: signal processing circuit,
F1 to F10: Sensor unit.

Claims (3)

A transmitter and a receiver are provided with a plurality of forward-direction transceivers facing each other, and a plurality of pairs of reverse-direction transceivers that are arranged on the same line as the forward-direction transceiver and have opposite transmission and reception directions ,
Along with arranging each of the plural pairs of forward-direction transceivers and reverse-direction transceivers on lines having different heights,
Each pair of forward and backward transceivers transmits and receives signals of different frequencies, and is a sensor that monitors an object that blocks signals transmitted between the plurality of pairs of transceivers ,
In each pair of the forward and backward transceivers, a set frequency range is provided for each line in order to distinguish a received signal from an image signal, and each of the forward and backward transceivers is connected to the same line. While receiving only the frequency transmitted from the above transmitter,
A multi-line sensor in which an offset frequency is set between the operating frequency of the forward direction transceiver and the operating frequency of the reverse direction transceiver so that the image signal does not fall within the set frequency range for each line. An oscillator for oscillating a reference frequency;
A PLL circuit that outputs a frequency signal used for each pair of transceivers based on the output of the oscillator;
A mixer for mixing a received signal from the receiver and a local oscillation signal obtained based on the PLL circuit;
2. The multi-line sensor according to claim 1, further comprising: a frequency analysis circuit that analyzes a reception frequency from an output of the mixer . In each of the pair of transceivers, the reception frequency obtained from the frequency analysis circuit is checked, and if a frequency shift occurs, correction data is output to the PLL circuit, whereby the transmission and reception of the pair of transceivers is performed. 3. The multi-line sensor according to claim 2, wherein the transmission frequency is corrected and updated .

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