JPH0443498A - Car sensor corresponding to multiple lanes - Google Patents

Abstract

PURPOSE:To measure speed with accuracy equal to a one-lane type sensor by providing the function to reproduce mixed Doppler signals while separating them for each lane. CONSTITUTION:Reception antennas 3 and 4 mutually synchronously switch the directionality with time division for each lane as shown by codes A, A', B, B', C and C'. In this case, the first and second reception antennas 3 and 4 receive radio waves, which are reflected from cars M traveling in respective lanes L1, L2 and L3 or from the surface of the road, for the respective lanes L1, L2 and L3. The received signals is mixed with a carrier signal by mixing circuits 15, a signal as frequency difference between the both signals is taken out ad this signal is outputted as a Doppler frequency comparing the car speed in each lane. Thus, the speed can be measured with the accuracy equal to that of the one-lane type sensor.

Description

[Detailed description of the invention] (a) Industrial application field This invention uses microwave radio waves to send specific information to each vehicle traveling on multiple lanes, and also detects the presence or absence of vehicles in each lane. This invention relates to a multi-lane vehicle sensor.

(b) Conventional technology Conventionally, as a multi-lane sensor that detects vehicles traveling on multiple lanes, a transmitting antenna with a directional characteristic that covers all lanes of the multi-lane road and a single lane The vehicle is equipped with a phased array one-type receiving antenna that has a directional characteristic that covers only 100 kHz of traffic, and whose directional characteristic can be switched time-divisionally for each lane. a transmission processing unit that outputs a modulated signal to transmit specific information such as passing points on a map, and modulates a carrier signal with the modulated signal from this transmission processing unit and transmits it as a transmission signal to a transmitting antenna. a control signal processing unit that outputs a phase control signal for time-divisionally switching the pointing direction of each lane with respect to the receiving antenna; A conventional vehicle has already been proposed, which is equipped with a vehicle presence/absence signal processing section that outputs sensing data on the presence or absence of vehicles in each lane.

(c) Problems to be Solved by the Invention In order to accurately measure the speed of a vehicle traveling in each lane, it is necessary to monitor Doppler signals in each lane for a certain period of time. For example, when the speed is 5 km/h, the Doppler frequency is several dozen or more, and the period of one cycle varies, so in order to accurately measure the frequency, it is necessary to increase the monitoring time for each lane. However, as the monitoring time becomes longer, the scanning cycle becomes longer in multi-lane vehicle detectors such as those in the earlier application, which switch the directional characteristics of the receiving antenna in a time-division manner, and the speed measurement of vehicles in other lanes becomes difficult. There was a fear that it would not be possible to do so. On the other hand, if the scan period is shortened, there is a problem in that the Doppler signals of each lane are mixed, making it impossible to distinguish the Doppler frequency of each lane.

This invention was made in view of the above problem, and by providing a function to separate and reproduce mixed Doppler signals for each lane, the scanning speed can be increased.
The object of the present invention is to provide a multi-lane vehicle sensor that can measure speed with the same accuracy as a -lane type vehicle sensor, even though it is multi-lane compatible.

(d) Means and Effects for Solving the Problems The multi-lane vehicle sensor of the present invention includes a transmitting antenna and a receiving antenna that are installed on a multi-lane road and transmit and receive microwave signals. It has a signal processing means for processing the transmitted and received signals of the antenna, the transmitting antenna transmits a directional beam having a directional characteristic covering all lanes of a multi-lane system, and the receiving antenna transmits a directional beam for only one lane. The signal processing means is a phased array type that has a directional characteristic that covers the directional characteristics and whose directional direction is switched in a time-sharing manner for each I lane. a transmission processing unit that outputs a modulated signal for transmitting information; a modulation unit that modulates a carrier signal with the modulated signal from the transmission processing unit and outputs the modulated signal to the transmission antenna as a transmission signal; a control signal processing section that outputs a phase control signal for time-divisionally switching the pointing direction for each lane; a plurality of sampling and holding units that operate on the phase control signal; a reproduction processing unit that reproduces Doppler signals for each lane in response to the output of the sampling and holding units; and a reproduction processing unit that reproduces Doppler signals for each lane in response to the output of the sampling and holding units; It is characteristically equipped with a vehicle speed calculation section that calculates the speed of the vehicle.

In this multi-lane vehicle sensor, the directional characteristics of the receiving antenna can be switched quickly using the phase control signal, and even when Doppler signals from each lane are mixed, the operation of the sampling and holding section can recur at the maximum Lempler frequency. It operates at a frequency higher than the Doppler frequency, and the sampling and holding section provided corresponding to each lane is selectively operated in synchronization with the phase control signal, so a sampling signal separated into Doppler signals for each lane can be obtained and held. Ru.

This signal output is then regenerated into a Doppler signal by a regeneration processing section such as a filter. Then, the vehicle speed is calculated based on the Doppler signal for each lane.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a block diagram showing the configuration of a multi-lane vehicle sensor according to an embodiment of the present invention.

In the figure, a multi-lane vehicle sensor 1 includes a transmitting antenna 2 for transmitting microwave radio waves, a first receiving antenna 3 for detecting vehicle speed, and a second receiving antenna 4 for detecting the presence or absence of a vehicle. , a transmitting antenna 2, and a signal processing section 5 that processes transmitted and received signals from the first and second receiving antennas.

The antenna 2.3.4 in this example is as shown in FIG.
It is attached to a pillar P erected on the roadside of a road having three lanes L+, Lx, and L3.

Installing each antenna 2.3.4 on the roadside in this way is advantageous from the standpoint of installation workability and aesthetics, but the central lane L! It is also possible to install it directly above the The above-mentioned transmitting antenna 2 is configured to transmit a directional beam D having a directional angle range that covers all of , L, , L, for each lane. In addition, the first and second receiving antennas 3
．． 4 both have directional characteristics that cover only one lane, and these directional directions are indicated by symbols A, A', B, and B' in the figure.
, c, and c', this is a one-sided type of phased array system in which the lanes are switched in a time-division manner for each lane. That is,
The first and second receiving antennas 3.4 are of the planar antenna type, and as shown in FIG.
. . and each antenna element 6.6, . . . is connected to a phase shifter 7.7, .

The signal processing unit 5 includes a transmission processing unit 11 that outputs a modulated signal for transmitting specific information such as passing points on a map to the vehicle, and an oscillator that outputs a high-frequency carrier signal having a constant oscillation frequency. 12, a modulation unit 13 that modulates the carrier signal from the oscillator 12 with the modulation signal from the transmission processing unit 11 and outputs it to the transmission antenna 2 as a transmission signal; a mixer circuit 15 that mixes the signal received by the first receiving antenna 3 with the carrier signal from the distributor 14;
, a signal separation unit 16 that separates the signal output of the mixing circuit 15 into Doppler signals for each of the three lanes, and a vehicle speed that outputs vehicle speed data based on the counter value for each lane obtained by the signal separation unit 16. a calculation unit 17; a level detection unit 18 that detects the level of the signal received by the second reception antenna 4 and outputs a reception level signal that indicates the presence or absence of a vehicle;
, a vehicle presence/absence sensing unit 19 that detects the presence or absence of a vehicle based on a received level signal, the direction of the directional beam for each lane is switched in a time-division manner for the first and second receiving antennas 3.4, and the phase separation unit 16. It includes a control signal processing section 20 that outputs a phase control signal.

As shown in FIG. 4, the signal separation unit 16 includes a low-pass filter 21, sampling and holding circuits 22-3.22-2.22-8 provided corresponding to each lane, and low-pass filters 23-1.23-1.゜23-1, counter 24-
1.24-2.24-3, the sampling and holding circuit 22-1%221.22-3 receives a control signal and performs a predetermined operation in response to the control signal that controls the directivity of the phased array antenna. Only when the directivity is selected, that signal is passed; otherwise, the final value at the time of selection is maintained. Further, the control signal is set to be at least twice the maximum Doppler frequency so as to satisfy the conditions of Shannon's sampling theorem.

Next, the operation of the multi-lane vehicle sensor 1 according to the embodiment will be explained.

In this multi-lane vehicle sensor 1, a high frequency carrier signal from an oscillator 12 is distributed by a distributor 14 to a modulating section 13 and a mixing circuit 15. In parallel with this, the transmission processing unit 11 outputs a modulated signal for transmitting specific information indicating passing points on the map to the vehicle M. The modulator 13 modulates the carrier signal with a modulation signal and outputs it to the transmitting antenna 2 as a transmitting signal. As a result, from the transmitting antenna 2, each lane L+, L2,
A microwave directional beam D having a directional characteristic covering all of L3 is transmitted, and the above specific information is sent to the vehicle M running on each lane Lt, Lx, L3. Therefore, when a vehicle M equipped with a dedicated receiver capable of receiving this radio wave passes over this sensor 1, specific information can be received.

On the other hand, a phase control signal is given from the control signal processing unit 20 to each phase shifter 7.7, . Since the time is set, as a result, the re-receiving antennas 3.4 are synchronized with each other and their directivity directions are indicated by the symbols A, A'', and A'' in the figure.
As shown by B, B', C, C'', each lane is switched in a time-sharing manner.
The radio waves reflected from the vehicle M traveling in lane 3 or from the road surface are transmitted to each lane 1, + by the first and second receiving antennas 3.4.
, Lx, and Ls.

The received signal received by the first receiving antenna 3 is mixed with the carrier signal in the mixing circuit 15, and a signal with a frequency difference between the two signals is extracted. Output as Doppler frequency proportional to speed. Then, the vehicle speed calculation unit 17 calculates the vehicle speed based on the Doppler frequency for each lane and outputs the data. Further, the received signal received by the second receiving antenna 4 is detected by the level detector 18, and a received level signal having a voltage value corresponding to the level of the received signal is output. The vehicle presence/absence sensing section 19 outputs sensing data on the presence/absence of a vehicle based on this reception level signal.

Next, the operation of the signal separation section 16, which is the main circuit of the present invention, will be explained. FIG. 5 shows signal waveforms at each part of the signal separation section 16. The high frequency components of the output signal from the mixing circuit 15 are removed by a low pass filter 21 to obtain a signal a in which Doppler signals of three lanes are mixed.

Each sampling hold circuit 22-1.224.22-
8 allows the signal to pass when a predetermined specificity is selected in time order according to a control signal for switching and controlling the directivity of the phase array antenna 3, and other corresponding directivity is not selected. At this point, the final value at the time of selection is retained. Therefore, each sampling hold circuit 22-
1.22-2.22-3 output signals S, c, d are the fifth
The result will be as shown in the figure. These output signals S, C, D are
The original Doppler signals e, f, g (fifth
(see figure). The frequencies of these signals eS f, g are further counted by counters 24-1.24-7.24-3. These Doppler frequency count values are input to the vehicle speed calculation section 17 to calculate the vehicle speed. In this way, while switching the directivity for each lane in a time-sharing manner, speed can be measured with the same accuracy as when one lane is constantly monitored.

(f) Effects of the Invention According to the present invention, a signal separation unit consisting of a sampling hold unit and a Doppler signal reproducing unit is provided for each lane, and the directivity of the antenna is controlled by a control signal that is twice or more the highest Doppler frequency. The Doppler signal for each lane is held in a sampling hold section in synchronization with this control signal, and then reproduced by a reproducing circuit such as a filter, so the Doppler signal for each lane can be accurately reproduced. It is also possible to increase the scan speed, so even though it is a multi-lane type, it can measure speed with the same accuracy as the -lane type.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a multi-lane vehicle sensor showing an embodiment of the present invention, and Fig. 2 shows a transmitting antenna and a receiving antenna of the multi-lane vehicle sensor installed on a road. FIG. 3 is an explanatory diagram of the switching operation of the directional beam of the element of the receiving antenna, and FIG. 4 shows the specific configuration of the signal separation section of the multi-lane vehicle sensor of the above embodiment. The block diagram in FIG. 5 is a signal waveform diagram of each part of the signal separation section. 1: Multi-lane sensor, 2: Transmission antenna, 3: First
receiving antenna, 4: second receiving antenna, 5: signal processing section, 11: transmission processing section, 13: modulation section,
16: Signal separation unit, 17: Vehicle speed calculation unit, 22-I・22-!・224: Sampling hold circuit, 22-1, 224, 22-3: Low-pass filter.

Claims (1)

[Claims] (1) A transmitting antenna and a receiving antenna are provided on a multi-lane road to transmit and receive microwave signals, and a signal processing means is provided to process the signals transmitted and received by the antenna, and the transmitting antenna has multiple lanes. The receiving antenna transmits a directional beam having a directional characteristic that covers all lanes, and the receiving antenna has a directional characteristic that covers only one lane, and the directional direction is time-divided for each lane. The signal processing means is of a phased array type that can be switched, and the signal processing means includes a transmission processing section that outputs a modulated signal for transmitting specific information indicating passing points on a map etc. to the vehicle, and this transmission processing section. a modulation unit that modulates a carrier signal with a modulation signal from the carrier signal and outputs the modulated signal to a transmission antenna as a transmission signal; and a control signal processing unit that outputs a phase control signal that switches the pointing direction of the reception antenna in a time-division manner for each lane. and a plurality of sampling and holding sections that are provided corresponding to each of the lanes and that operate at a cycle that is equal to or greater than the maximum Doppler frequency that can be reproduced, and each of which operates in synchronization with the phase control signal; and this sampling and holding section. A multi-lane compatible vehicle comprising: a regeneration processing unit that regenerates Doppler signals for each lane in response to the output of the regeneration processing unit; and a vehicle speed calculation unit that calculates vehicle speed using the Doppler signals from the regeneration processing unit. type vehicle detector.