JPH04205300A - Position information receiver - Google Patents

Abstract

PURPOSE:To prevent the error of direct descending detection caused by multipath phasing or the like by adding a gate to disable direct descending even when it is detected while detecting error in demodulated information. CONSTITUTION:At the position information receiver equipped with an approach detecting means 16 to detect the approach to a fixed transmitter based on received waves, a gate means 18 is provided to disable the detecting signal of the approach detecting means 16 while an error detecting means 14 detects the error of data. In this case, while the state of a communication path is made adverse by multipath phasing or the like, it is enough estimated that the error is generated even in the demodulated data as well. Therefore, while the error is generated in the demodulated data, the approach detecting signal is disabled. Thus, the error of direct descending detection is prevented, and the reliability of a navigation system is more improved.

Description

[Detailed Description of the Invention] [Summary] An on-vehicle receiver has a function of receiving radio waves from a transmitter installed on the road to obtain position information and detecting that the vehicle is directly under the road transmitter. The purpose is to prevent errors in detection directly below due to deterioration of communication channels due to multipath fading and the like.

A gate is added so that the detection of the position immediately below becomes invalid while an error is detected in the demodulated position information.

[Industrial application field]

The present invention relates to a position information receiving device for receiving radio waves carrying position information from a fixed station to know the position of a mobile object, and in particular a radio wave carrying position information from a roadside communication device installed on the road. The present invention relates to a position information receiving device having a function of receiving location information by receiving a signal and determining whether or not the device is located directly below a roadside communication device based on an AM modulation component of a received wave.

This type of device is used to correct the position of a navigation system using autonomous navigation, which calculates its own position based on data from an azimuth sensor and a vehicle speed sensor.

[Conventional technology] In the second type of system, a roadside communication device sends out radio waves modulated with digital information that includes information about the installation location, and the on-vehicle communication device receives these radio waves within a range of several tens of meters. be able to.

Therefore, accurate position information cannot be obtained unless the timing at which the vehicle passes directly under the roadside communication device is detected.

FIG. 4 is a block diagram showing the roadside communication device portion of the system constructed for this purpose. The modulated wave subjected to phase or frequency modulation such as FSK modulation using digital data in the data modulation section 102 is further transmitted to the AM modulation section 108.
, 110 for AM modulation. The modulation signal for this AM modulation is a low frequency sine wave and its phase shifted by a 180° phase shift circuit 106. The two types of AM-modulated transmission waves are sent out from the two directional antennas 112 and 114 as in-phase transmission waves and anti-phase transmission waves, respectively, in different directions on the road.

The in-phase transmission wave and the anti-phase transmission wave are received in a combined form by a receiver mounted on a car within a range of several tens of meters from the roadside communication device. As the car approaches directly below the roadside communication device, the electric field strength of either the in-phase or anti-phase transmitted wave becomes stronger, and the amplitude of the AM modulation component also increases. The intensities of the out-of-phase transmitted waves become equal, so that the in-phase and out-of-phase components of the AM modulation component cancel each other out, and the AM modulation component rapidly decreases. Therefore, while Kimaria is received above a given level,
And the amplitude of the AM modulation component is a predetermined threshold value V. When the following is true, it can be determined that the vehicle is directly under the roadside communication device.

FIG. 5 is a block diagram showing the configuration of an example of a conventional position information receiving device based on this principle.

The received wave is mixed with a signal from a local oscillator 122 in a mixer 120, converted to an intermediate frequency, and FSX (
The data is demodulated in a frequency shift keying (frequency shift keying) demodulator 126. The demodulated data becomes valid in the gate circuit 128 only while the carrier detector 124 detects a carrier of a certain level or higher from the received wave, and is supplied to the microcomputer 200.

On the other hand, the AM modulation component is demodulated in the AM demodulator 162, and its envelope is detected in the envelope detection circuit 164. This detection output is the threshold voltage V in the comparator 166. When it is less than that, a direct detection signal is output. This direct detection signal becomes valid in the gate circuit 168 only while a carrier of a certain level or higher is detected from the received wave in the carrier detector 160, and is supplied to the microcomputer 200.

The microcomputer 200 uses the position information when this direct detection signal is output to correct the position.

Fig. 6 is a timing chart for explaining the operation of the circuit shown in Fig. 5, and shows the states of the signals at the points A-D in Fig. 5 when a car passes directly under the roadside communication device. These are shown in columns (A) to (D>).At the position directly below, the envelope of the modulation component (column (B)) is below the threshold V. At this time, the carrier detection signal (column (A)) is at H level. Therefore, the direct detection signal (column (D)) is output.

In addition to the above-mentioned method, roadside communication devices use a fixed period rectangular wave synchronized with data instead of a sine wave and a 180
There is also a method in which AM modulation is performed using a phase-shifted component, and on the receiving side, the phase of the AM modulation component is detected based on the received data, and when the phase is inverted, it is considered to be a direct pass.

[Problem to be solved by the invention]

FIG. 7 is a diagram similar to FIG. 6, but it is assumed that multipath fading has occurred in the section indicated by T.

At this time, as shown in column (A), the carrier level may exceed the dark value due to the influence of the reflected wave and a carrier detection signal may be output. In this case, since the received wave is distorted, the envelope of the AM modulation component is at the threshold V as shown in column (B).

The following may be possible. Therefore, in such a case, as shown in column (D), a problem arises in that the direct detection signal is output even though the vehicle is not directly below the roadside communication device.

The same applies to the second system, which has the problem of determining that it is directly below even though it is not directly below due to multipath fading.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a position information receiving apparatus that does not detect passing directly below even if the condition of a communication path deteriorates due to multipath fading or the like.

[Means to solve the problem]

FIG. 1 is a diagram showing the basic configuration of the present invention.

In the figure, the position information detecting device of the present invention has a data demodulating means 12 for restoring digital data including position information carried in a received wave from a fixed transmitter 10. In a position information receiving device comprising an error detection means 14 for detecting an error and an approach detection means 16 for detecting approach to the fixed transmitter based on the received wave, at least the error detection means 14
The present invention is characterized in that it includes a gate means 18 for invalidating the detection signal of the approach detection means 16 during a period when the detection means 16 is detecting data errors.

2 Effects] While the condition of the communication channel is deteriorating due to multipath fading, etc., it is fully expected that errors will occur in the demodulated data. Therefore, by disabling the approach detection signal while errors occur in the demodulated data,
This detection can be prevented.

〔Example〕

FIG. 2 is a diagram showing the configuration of an embodiment of the present invention. Components that are the same as those in FIG. 5 are given the same reference numerals and their explanations will be omitted. Further, FIG. 3 is a diagram in the same format as FIG. 7, showing the states of signals at points A to G in FIG. 2.

A communication control LSI (not shown) included in the microcomputer 200 usually performs a CR on received data.
It has a function to perform C check. When it is determined that it is a CRC check, the microcomputer 200
0 port (not shown) to output a pulse (3rd
Figure (E) column). The mono multi-by-break 180 uses this pulse as a trigger to output a pulse with a predetermined width ((F
) column).

The gate circuit 182 is closed while this pulse is being output, and the direct detection signal during this period is invalid ((G)
column).

〔Effect of the invention〕

As described above, according to the present invention, errors in direct detection due to multipath fading and the like are prevented, and the reliability of the navigation system is further improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing an embodiment of the invention, Fig. 3 is a diagram for explaining the operation of the device shown in Fig. 2, and Fig. 4 is a diagram showing the construction of the device on the road. A diagram showing the configuration of a communication device, FIG. 5 a diagram showing the configuration of a conventional position information receiving device, FIG. 6 a diagram for explaining the operation of the device in FIG. 5, and FIG. 7 a diagram showing the conventional device. A diagram explaining the problem. In the figure, 124, 160...carrier detector, 126...
-FSK demodulator, 162...AM demodulator, 180...mono multi-by-break. Configuration of roadside communication device Figure 4 T-

Claims (1)

[Claims] 1. Data demodulation means (
12), error detection means (14) for detecting errors in data restored by the data demodulation means (12), and approach detection means (16) for detecting approaching the fixed transmitter based on the received waves. ), gate means (18) for invalidating the detection signal of the approach detection means (16) at least during a period when the error detection means (14) is detecting data errors; A location information receiving device comprising: