JPH11118901A - Differential GPS receiver - Google Patents

Abstract

(57) [Summary] [Problem] In a differential GPS receiver,
To improve the positioning accuracy by receiving differential information without interruption. When a transmission signal of the same frequency is received as a reception signal, a control unit switches and controls a signal selector so as to select a reception unit having a high reception level among reception levels of the reception signals. Then, the control unit checks the signal level of the adjacent frequency by designating the adjacent frequency of the differential system to the reception frequency of the reception unit having a low reception level, and the signal level of the adjacent frequency is selected by the signal selector. If the reception level is higher than the reception level, the signal selector is switched and controlled so as to select the reception unit receiving the adjacent frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection method used for receiving differential GPS information and obtaining a differential GPS position at a receiving point.

[0002]

2. Description of the Related Art Generally, a beacon or an FM radio is used as a means for transmitting differential information. When it is desired to obtain differential information using a directional antenna in a mobile body, an antenna, an amplifier, and an It is necessary to provide two receiving systems including a demodulator. Then, transmission signals of the same frequency are received and demodulated by the two reception systems as reception signals, and transmission signals (data) of the reception system that have been accurately demodulated are used (hereinafter, referred to as a first method). ).

Further, when obtaining the differential information as described above, only two antennas are provided, the transmission signals are received in a time-division manner, and the level of the transmission signals is compared to determine which antenna has the higher reception level. Is also performed (hereinafter, referred to as a second method).

[0004]

By the way, the above-mentioned first method is used.
Although the method of the above has two receiving systems, it is possible to receive transmission signals from the same transmitting station in good condition,
One reception system is involved in the reception processing of the transmission signal, but does not substantially use the demodulated signal. For this reason, the efficiency of the receiving process is reduced. Furthermore, in the first method, there is difficulty in automatically switching to an adjacent frequency (adjacent station).

On the other hand, the second method has a problem in that when the level is measured by controlling the switching of the antenna, the demodulation of the transmission signal is interrupted and the accuracy is reduced.

An object of the present invention is to provide a differential GPS receiver which can perform antenna switching and frequency switching without interruption when receiving a transmission signal with an antenna having directivity, and in particular, to interrupt differential information. It is an object of the present invention to provide a channel selection method capable of improving the positioning accuracy by receiving a signal without receiving the signal.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a channel is selected by using one free receiving system which requires two receiving systems but also searches for adjacent frequencies as well as checking the level of the working frequency. Information for switching is obtained to improve the utilization efficiency and measurement accuracy of the device.

That is, according to the present invention, a first H field antenna is provided, a transmission signal of a first frequency is received as a first reception signal, the first reception signal is output, and the first reception signal is output. A first receiving unit that outputs a reception level of a reception signal as a first reception level; and a second H-field antenna that is orthogonal to the first H-field antenna and that is arranged so as to supplement horizontal plane directivity. A second receiving unit that receives the transmission signal of the second frequency as a second reception signal, outputs the second reception signal, and outputs the reception level of the second reception signal as a second reception level A signal selector that selects one of the first and second received signals and outputs the selected signal as a selection signal; a demodulator that demodulates the selection signal to obtain GPS differential information; And comparing the first and second reception levels when the second frequency is the same, and selecting a reception unit having a higher reception level among the first and second reception levels according to the comparison result. And a control unit for switching and controlling the signal selector. When the signal level of the adjacent frequency is checked and is higher than the reception level of the receiver selected by the signal selector, the signal selector is switched and controlled to select the receiver that is receiving the adjacent frequency. Thus, a differential GPS receiver characterized in that:

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

Referring to FIG. 1, the illustrated receiving apparatus includes first and second receiving sections 11 and 12, and the first receiving section 11 includes an H field (magnetic field) antenna and a signal amplifier 2. ing. Similarly, the second receiving unit 12 includes an H field antenna 3 and a signal amplifier 4, and the H field antenna 3 is arranged so as to be orthogonal to the H field antenna 1 and to supplement horizontal plane directivity.

As shown, the first and second receiving units 11
And 12 are connected to a signal selector 5, the signal selector 5 is connected to a demodulator 6, and the control unit 7 is provided with demodulated data from the demodulator.

A transmission signal from a transmission station (not shown) is received as first and second reception signals by H field antennas 1 and 3, respectively, and amplified by signal amplifiers 2 and 4 to a level required for data demodulation. You.

As described above, the H field antennas 1 and 3 are arranged so that their directivities are orthogonal to each other.
Therefore, when a transmission signal of the same frequency is received,
In directions other than 45 °, 135 °, 225 °, and 315 °, the reception level of one of the antennas is higher than that of the other antenna. That is, the reliability as a received signal is improved.

The signal selector 5 receives the first and second received signals, selects one of them under the control of the controller 7, and supplies the selected signal to the demodulator 6 as a selection signal. The demodulator 6 demodulates the selection signal to obtain demodulated data. The demodulated data is supplied to a GPS receiving unit (not shown) and to the control unit 7.

Here, control of the signal amplifiers 2 and 4 and the signal selector 5 by the control unit 7 will be described. First, the control unit 7 sets the first receiving unit 11 and the second receiving unit 12 to the same frequency (automatically tuned frequency. Since the automatic tuning method is well known, the description will be given here. Omitted)
And receives the first and second received signals from the signal amplifiers 2 and 4, respectively, and compares the received levels. According to the result of the comparison, the control unit 7 controls the signal selector 5 so as to select a receiving unit that receives a received signal having a high reception level. As a result, a received signal having a high reception level is provided to the demodulator 6. The demodulator 6 demodulates the received signal sent from the signal selector 5 to obtain demodulated data (differential data).
Output to PS receiver.

Next, the control unit 7 sets the frequency of the receiving unit that has not been selected to the adjacent frequency, and obtains the reception level of the adjacent station. The data of the adjacent station is usually included in the received data (demodulated data), and information (data of the adjacent station) is obtained from the output of the demodulator 6.

On the other hand, as described above, the data of the adjacent station is not obtained from the output of the demodulator 6, but the known station data is stored in the control unit 7 in advance, and the position information (position data) of the GPS is used. The data of the adjacent station may be obtained.

When the reception level of the adjacent station is obtained, the control unit 7 compares the reception level of the current station with the reception level of the adjacent station. Is selected, and the signal selector 5 is controlled so that a signal received from the receiving unit is supplied to the demodulator 6.

When the reception level of the adjacent station is high,
This means that the channel has been changed automatically. In general, there are several adjacent stations, and all stations are compared if necessary. When the comparison of all the stations is completed, the process returns to the original state, receives the currently valid frequency, and compares the reception levels.

As described above, when receiving the transmission signals of the same frequency as the reception signals, the control unit 7 controls the signal selector 5 to switch the signal selector 5 so as to select the reception unit having the higher reception level among the reception levels of these reception signals. The control unit 7 checks the signal level of the adjacent frequency by designating the adjacent frequency of the differential system to the reception frequency of the reception unit with the low reception level, and selects the signal level of the adjacent frequency by the signal selector 5. If the received level is higher than the receiving level of the receiving unit, the signal selector 7 is switched and controlled so as to select the receiving unit receiving the adjacent frequency.

In the above-described example, the H field antenna is used, but 0 ° (1 °) is used instead of the H field antenna.
Two E-field (electric field) antennas having directivity in directions of 80 °) and 180 ° (270 °) may be used.

[0022]

As described above, according to the present invention, a reception system having a high signal level is used at the same frequency.
When the adjacent frequency becomes higher than the current reception frequency, the frequency is automatically switched to the adjacent frequency, so that there is an effect that highly reliable differential information can be always obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a differential GPS receiver according to the present invention.

[Explanation of symbols]

 1,3 H field antenna 2,4 signal amplifier 5 signal selector 6 demodulator 7 control unit

Claims (2)

[Claims] A first H-field antenna having a first H-field antenna;
A first receiving unit that receives a transmission signal having a frequency of f as a first reception signal, outputs the first reception signal, and outputs a reception level of the first reception signal as a first reception level; A second H-field antenna that is orthogonal to the first H-field antenna and that is arranged so as to compensate for horizontal directivity; receives a transmission signal of a second frequency as a second reception signal; A second receiving unit that outputs a reception signal and outputs a reception level of the second reception signal as a second reception level;
A signal selector that selects one of the received signals and outputs the selected signal as a selection signal; a demodulator that demodulates the selection signal to obtain GPS differential information; and wherein the first and second frequencies are the same. Sometimes, the first and the second
And a control unit that controls switching of the signal selector so as to select a receiving unit having a large reception level among the first and second reception levels according to the comparison result. The control unit specifies the reception frequency of the reception unit having the small reception level as an adjacent frequency of the differential system, checks the signal level of the adjacent frequency, and selects the signal level of the adjacent frequency by the signal selector. A differential GPS receiver, wherein the signal selector is switched and controlled so as to select a receiving unit receiving the adjacent frequency when the receiving level is higher than a receiving level of the receiving unit. 2. The differential GPS receiver according to claim 1, wherein an E-field antenna having directivity in directions of 0 ° and 90 ° is used in place of said first and second H-field antennas. A differential GPS receiver, characterized in that: