JPH0416787A - Apparatus for detecting speed of moving body - Google Patents

Abstract

PURPOSE:To calculate real Doppler transform quantity without requiring a highly stable oscillator and to detect low speed by measuring transmission frequency within a real time and accurately detecting the same on the side of a moving body receiving apparatus. CONSTITUTION:The transmitter 2 within a ground fixed transmission apparatus 20 generates a radio wave R which is, in turn, emitted to a moving body receiving apparatus 30 through a transmission antenna 1. The transmission frequency measuring apparatus 7 in the apparatus 20 measures frequency fr. The frequency fr is converted to digital data D by an encoder 8 and this digital data is modulated in a modulator 9 by a sub-carrier wave to be sent out to the transmitter 2. The radio wave R radiated from the transmission antenna 1 is received by the receiving antenna 3 integrated with the receiving apparatus 30 and the receiver 4 separates the sub-carrier wave from a carrier wave to send out the same to a demodulator 10. The digital data D is demodulated by the demodulator 10 and a decoder 11 detects the value of the frequency fr from the data to inform the same to an operational processing part 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a moving object speed detection device, and in particular, the present invention relates to a moving object speed detection device, and particularly to a moving object speed detection device by detecting an accurate Doppler shift amount even if there is a fluctuation in the oscillation frequency on the transmitting side. The present invention relates to a moving body speed detection device that can detect the speed of a moving body with high accuracy.

C. Prior Art FIG. 2 is a configuration diagram showing a conventional Dotsupura navigator moving object speed detection device, as shown in, for example, the Electronic Communication Handbook (P146, published by Ohmsha, March 30, 1972). In the figure, (1) is a transmitting antenna that radiates radio waves R generated from a fixed ground transmitter, (2) is a transmitter on the ground that constitutes the fixed ground transmitter (20), and (3)
is a receiving antenna that receives radio waves R and transmits them to the mobile receiver (30). (4) is a receiver connected to the receiving antenna (3), (5) is a frequency measuring device that continuously measures the frequency of the received radio wave R, and (6) is a device that measures the speed of the moving object from the amount of Doppler deviation. It is an arithmetic processing unit that calculates these (
4) to (6) are provided in a mobile body together with the receiving antenna (3), and constitute a mobile body receiving device (30).

The conventional mobile speed detection device is configured as described above, and the transmitter (2) of the ground fixed transmitter (20) transmits the frequency f to the mobile receiver (30) via the transmitting antenna (1).
emit radio waves R. The mobile receiver (30) receives radio waves R via the receiving antenna (3) with a receiver (4). Reception frequency measuring device (
5) continuously measures the frequency f of the received radio wave R. At this time, the frequency fP undergoes a Doppler shift due to reception from the mobile object, and the transmission frequency f? The frequency fR is shifted from . This received radio wave frequency 8 is transferred to the arithmetic processing unit (6), and speed calculation is performed according to the following formula.

However, f is the amount of Doppler deviation, f, : is the transmission frequency, f
8 is the reception frequency, C is the speed of light, and ■ is the speed of the moving object.

In this way, the speed V of the moving object is determined by the Doppler shift amount f under the condition that the frequency f of the transmitted radio wave is constant.

Determined by measuring

[Problem to be solved by the invention]

As described above, in the conventional mobile object speed detection device, it is assumed that the frequency of the transmitted radio wave R is a preset constant value. However, since there is a frequency drift in the oscillator (2), the fluctuation of the frequency f, △
f must be taken into account. Now, let the true Doppler deviation amount be fD < true), the frequency of the true transmitted radio wave be f, (true), and let ft (true) = f, r±△f, then fo (true) = f, - f, (true) = f, - (fa±Δf) = f o±Δf. Therefore, the velocity ■ of the moving object should be as follows. However, since the variation Δf has been ignored in the past, the variation Δf has become an error.

Therefore, the detection accuracy of the conventional moving body speed detection device is determined by the frequency stability of the oscillator 2), and there is a problem in that the detection range, especially at low speeds, is restricted. Furthermore, if an attempt is made to suppress the frequency variation Δf to a small value, there is a problem that the apparatus becomes expensive.

This invention was made to solve the above-mentioned problems, and it is possible to determine the true Doppler deviation amount without the need for a high-stability oscillator, and to detect the speed of a moving object at low speeds. The purpose is to provide a detection device.

[Means to solve the problem]

A mobile object speed detection device according to the present invention is provided with means for measuring the frequency of its own transmitted radio waves in real time in a fixed ground transmitting device, and means for encoding the measured value and transmitting it as digital data. The device is equipped with a decoding means for decoding digital data.

[For production]

In this invention, the transmission frequency is measured in real time and accurately detected on the mobile receiver side. Therefore, even if there is a fluctuation in the oscillation frequency of the transmitting side, the receiving side can accurately detect the amount of Doppler shift and perform highly accurate speed detection.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing one embodiment of the present invention,
(1) to (8), (20) and (30) are similar to the conventional device described above.

(7) is a transmission frequency measurement device that continuously measures the transmission frequency f of the transmitter (3), and (8) is a transmission frequency measurement device that converts the frequency f measured by the transmission frequency measurement device (7) into digital data D. The encoder (9) is a modulator that modulates the digital data D using a subcarrier and transmits it to the transmitter (2). These (7) to (9) are ground fixed transmitting devices (20)
The encoder (8) and the modulator (9)
constitutes coded modulation means.

On the other hand, (10) is a demodulator that demodulates digital data from the subcarrier output from the receiver (4), and (11) is a decoder that decodes the transmission frequency value from the terrestrial fixed transmitter (20) from the digital data. These constitute demodulation/decoding means within the mobile receiving device 30).

In this case, the arithmetic processing unit (6) detects the Doppler shift from the transmission value decoded by the decoder 11) and calculates the speed of the moving object.

In the mobile speed detection device configured as described above, the transmitter (2) in the ground-fixed transmitter (20) transmits radio waves R at a frequency expressed by fT (true) = f, ±△f. This radio wave R is radiated toward the mobile receiving device (30) via the transmitting antenna (1). At the same time, the ground fixed transmitter (20
) The transmission frequency measuring device (7) in ) has a frequency f, (true)
Measure. This measurement frequency fT is converted into digital data D by an encoder (8), and further converted into digital data D by a modulator (9).
is modulated by a subcarrier and sent to a transmitter (2). As a result, the transmitter (2) transmits the center frequency f of the carrier wave.
T (true) generates a radio signal modulated on the subcarrier of the modulator (9).

Transmission air I! Radio waves R radiated from (1) are received by a receiving antenna (3) integrated with a mobile receiver (30) and transferred to a receiver (4). The receiver (4) separates the subcarrier from the carrier of the received radio wave R, and sends it to the demodulator (1).
0). A demodulator (lO) demodulates digital data D from the subcarrier. The decoder (11) detects the frequency f and the (true) value from the digital data D, and notifies this value to the arithmetic processing unit (6).

On the other hand, the reception frequency measuring device (5) measures the reception frequency f8 based on the radio signal from the receiver (4), and notifies the arithmetic processing unit (6) of this value. The arithmetic processing unit (6) is
From the input frequency information f and fR, it is possible to know that fD (true)=fRfT (true) "fIl<fr±△f) fD±△f. From this, the following is calculated.

In this way, it is possible to perform calculations that take into account the fluctuations in the transmission frequency f, and the speed detection accuracy is improved.

〔Effect of the invention〕

As described above, according to the present invention, the terrestrial fixed transmitter side is provided with an encoding/modulating means for transmitting the frequency of the transmitted radio wave as digital data, and the mobile receiver side is provided with a demodulating/decoding means for demodulating and decoding the digital data. The device is equipped with an arithmetic processing unit that calculates the speed of the moving object using the digital data and the received frequency, and even if there is a frequency fluctuation on the transmitting side, this can be detected on the receiving side, making it possible to detect speed with high accuracy. In addition, it is possible to obtain a moving object speed detection device that realizes cost reduction without paying special consideration to the frequency stability of the transmitter even when detecting low speeds.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional moving object detection device. In the district, (2) is a transmitter, (4) is a receiver, and (5)
is a reception frequency measurement device, (6) is an arithmetic processing unit, (7) is a transmission frequency measurement device, (8) is an encoder, (9) is a modulator, (10) is a demodulator, and (11) is a decoder. (20) is a fixed terrestrial transmitter, (30) is a mobile receiver, f is a transmission frequency, f8 is a reception frequency, and D is digital data. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A transmitter that generates radio frequency radio waves, a transmission frequency measuring device that measures the frequency of the radio waves, and an encoding/modulating device that transmits the measured frequency as digital data. a fixed ground transmitter; a receiver that receives the radio wave including digitized information on the frequency; a reception frequency measuring means that measures the frequency of the received radio wave; and digitized frequency information included in the radio wave. a mobile object receiving device comprising: a demodulating/decoding means for demodulating and decoding the received radio wave; and an arithmetic processing section for calculating the speed of the mobile object based on the frequency of the received radio wave and the digitized frequency information. Mobile speed detection device.