JP2728071B2 - Transmitter using range tone modulation and receiver thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and a receiver using range tone modulation, and more particularly to a transmitter and a receiver using range tone modulation for distance measurement between the two devices.

[0002]

2. Description of the Related Art A transmitting apparatus synthesizes a plurality of range tones (low-frequency signals) having different frequencies, FM-modulates the signals, and transmits the signals. While transmitting the information including the separated range tone signal back to the transmitting device, the transmitting device compares the phase of the returned range tone signal with the phase of the transmitted range tone signal to measure the distance between the two. The so-called secondary radars that perform are known.

FIG. 4 is a circuit diagram showing an example of a signal synthesizing section of a conventional transmitting apparatus using range tone modulation, and FIG. 5 is a circuit diagram showing an example of a signal separating section of a receiving apparatus receiving the transmission signal. Note that the configuration of the transmitting device after the signal combining unit and the configuration of the receiving device before the signal separating unit are omitted.

[0004] A signal synthesizing unit 50 of a conventional range tone modulation transmitting apparatus includes three resistors 51 to 53 and an amplifier 55 whose input side is connected to a common connection terminal 54 of the resistors 51 to 53. And each of the resistors 51-5
3 has the lowest frequency range tone signal f1,
A range tone signal f2 having the highest frequency and a range tone signal f3 having an intermediate frequency are input.

[0005] These signals f1 to f3 are supplied to a signal synthesizing section 50.
After that, the carrier is FM-modulated by a modulator (not shown). Then, the FM modulated wave is transmitted via a power amplifier, an antenna, and the like.

[0006] On the other hand, the transmission wave is received by a receiving device, and is demodulated by a demodulation unit (not shown) to extract a range tone signal.
1 to 63, the original three range tone signals f1 to f
3

The separated three range tone signals f1 to f3 are sent back together with other information to the transmitting device by a return means (not shown).

The transmitting device compares the phases of the returned three range tone signals f1 to f3 with the transmitted three range tone signals f1 to f3 to measure the distance between them.

The reason for comparing the respective phases using three range tone signals and calculating the distance comprehensively from these results is to improve the distance measurement accuracy. In general, it can be said that as the number of range tone signals is increased, higher ranging accuracy is obtained.

Further, in order to extend the distance, it is necessary to widen the frequency difference between the low and high range tone frequencies. Usually, the high frequency is about 500 for the low frequency.
１０００1000 times (for maximum range and maximum accuracy).

An example of this type of transmission / reception apparatus is disclosed in JP-A-4-223286, JP-A-4-142486, JP-A-4-105086 and JP-A-4-3.
No. 43084.

[0012]

However, in the conventional transmitting apparatus, the range tone signal is obtained by simply synthesizing several kinds (for example, three or four kinds) of frequencies and inputting them to the modulating unit of the transmitting apparatus. For example, when the frequency difference between the low frequency band and the high frequency band of the range tone signal is widened, there is a problem that the modulation distortion easily occurs at the lowest frequency of the range tone signal. This is because it is difficult to obtain low-frequency linearity characteristics in the modulation section.

Further, Japanese Patent Application Laid-Open Nos. Hei 4-223286, Hei 4-142486, Hei 4-105086
Japanese Patent Application Laid-Open No. Hei 4-343048 does not disclose means for solving this problem.

An object of the present invention is to provide a range tone modulation transmitting apparatus and a receiving apparatus capable of reducing modulation distortion at the lowest frequency of a range tone signal.

[0015]

According to the present invention, a carrier wave of a predetermined frequency is modulated by at least a range tone signal having the lowest frequency among a plurality of range tone signals having different frequencies. First modulating means, a signal synthesizing means for synthesizing the modulated signal and the unmodulated range tone signal, and a second means for modulating a carrier having a frequency higher than the carrier with the synthesized signal. Modulation means.

According to a second aspect of the present invention, the frequency of the carrier of the first modulating means is set near the frequency of the unmodulated range tone signal.

In the third aspect, first demodulating means for demodulating the synthesized range tone signal, signal separating means for separating the demodulated signal into respective range tone signals, and It is characterized by including a second demodulating means for demodulating the modulated carrier.

According to a fourth aspect of the present invention, the receiving apparatus further comprises means for sending back information including the demodulated range tone signal to the transmitting apparatus.

According to a fifth aspect of the present invention, the transmitting apparatus further comprises a distance measuring means for measuring a distance to the receiving apparatus based on information including a range tone signal returned from the receiving apparatus.

[0020]

According to the first aspect of the present invention, a carrier having a predetermined frequency is modulated by a range tone signal having the lowest frequency.

According to the second aspect of the present invention, the frequency of the carrier of the first modulating means is set near the frequency of the unmodulated range tone signal.

According to the third aspect of the present invention, the receiving apparatus demodulates the carrier which is still modulated after signal separation, and extracts a range tone signal having the lowest frequency.

According to the fourth aspect of the present invention, the receiving device returns information including the demodulated range tone signal to the transmitting device.

According to the fifth aspect of the present invention, the transmitting device measures the distance to the receiving device based on the information including the range tone signal returned from the receiving device.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a first embodiment of a signal synthesizing unit of a transmission apparatus using range tone modulation according to the present invention.

In the following drawings, the same components as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. Also, the configuration of the transmitting device after the signal combining unit and the configuration of the receiving device before the signal separating unit are the same as those of the conventional device, so that illustration and description are omitted.

The signal synthesizing section of the transmission apparatus using the range tone modulation includes three resistors 51 to 53 and these resistors 5 to 53.
It comprises an amplifier 55 whose input side is connected to a common connection end 54 of 1 to 53, and an FM modulator 1 whose output side is connected to the other end of the resistor 51.

Then, the range tone signal f1 having the lowest frequency is input to the FM modulator 1, and the range tone signal f1
1 modulates the carrier by FM. In this case, the frequency of the carrier is a signal in a low frequency range, but in the present embodiment, an intermediate frequency of other range tone signals f2 and f3 described later is used. It should be noted that the frequency is not limited to an intermediate value between f2 and f3, but may be any frequency around f2 or f3.

The range tone signal f2 having the highest frequency is input to the other end of the resistor 52, and the frequencies f1 and f2
The range tone signal f3 set in the middle of
3 is input to the other end.

The three range tone signals f1 to f
3 is synthesized via resistors 51 to 53, and then
5, and is input to an FM modulator (not shown) and further transmitted wirelessly via a power amplifier and an antenna (not shown).

If the range tone signal f1 having the lowest frequency is directly modulated by an FM modulator (not shown), modulation distortion may occur. Therefore, in the present invention, the range tone signal f1 is modulated by the FM modulator 1 to increase the frequency to a frequency near the other range tone signals f2 and f3.

Thus, the modulation distortion when the range tone signal f1 is modulated by the FM modulator (not shown) (the carrier wave modulated by this modulator has a high frequency as in the conventional transmitting apparatus) is improved. can do.

Next, a receiver for receiving the transmitted signal will be described. FIG. 2 is a circuit diagram of one embodiment of the signal separating unit of the receiving device.

The signal separating section of the receiving apparatus includes band filters 61 to 63 for separating frequencies, and an FM demodulating section 11
Consists of

First, the received signal is demodulated by a demodulation unit (not shown). Then, the modulation signal f1m including the range tone signal f1 having the lowest frequency is separated by the bandpass filter 61. Next, the modulated signal f1m is transmitted to the FM demodulation unit 1
Demodulate by 1. Thereby, the original range tone signal f1
Is extracted.

On the other hand, the range tone signal f 2 having the highest frequency is separated by a band filter 62, and the range tone signal f 3 having an intermediate frequency is separated by a band filter 63.

In this way, even if the range tone signal f1 having the lowest frequency is a signal independently FM-modulated unlike the other range tone signals f2 and f3, the receiving apparatus demodulates the range tone signal f1. be able to.

Then, the separated three range tone signals f1 to f3 are sent back to the transmitting device together with other information, for example, the identification code of the receiving device, by a well-known returning means (not shown).

On the other hand, the transmitting device measures the phase difference between the returned three range tone signals f1 to f3 and the transmitted three range tone signals f1 to f3, respectively.
The distance between the two devices is measured based on the phase difference and the frequency.

The frequency of the range tone signal f1 having the lowest frequency is determined by the maximum range of the distance measurement, and the frequency of the range tone signal f2 having the highest frequency is determined by the distance measurement accuracy and system accuracy. The range tone signal f3 set to the intermediate frequency is used to carry the value measured by the range tone signal f2.

Next, a description will be given of a second embodiment of the signal combining section of the transmitting apparatus. FIG. 3 shows a second example of the signal combining unit of the transmitting apparatus.
It is a circuit diagram of an example.

If the distance measurement range becomes very long, four or more range tone signals may be used in view of the maximum range and accuracy of the distance measurement. The second embodiment shows this case, in which a range tone signal f1 having the lowest frequency, a range tone signal f2 having the highest frequency, and a plurality of range tone signals f2a to f2n having intermediate frequencies are used.

In this case, the range tone signal f1 having the lowest frequency is modulated by the FM modulator 1, and the range tone signal f2a having the next lower frequency is also modulated by the FM modulator 2, and these two range tone signals are then modulated. f1,
The modulation distortion is improved by increasing the frequency of f2 to near the frequency of another range tone signal.

It should be noted that it is also possible to carry out FM modulation of three or more range tone signals as required.

Further, it is needless to say that it is necessary to provide FM demodulators on the receiving device side in a number corresponding to the number of FM-modulated range tone signals.

This modulator is not limited to FM (frequency modulation), but can exhibit the same effect in AM (amplitude modulation).

[0047]

According to the present invention, a carrier of a predetermined frequency is modulated with at least the lowest frequency range tone signal among a plurality of range tone signals having different frequencies. The frequency can be raised to a region where modulation distortion does not occur.

According to the present invention, by setting the frequency of the carrier wave of the first modulation means near the frequency of the range tone signal which is not modulated, the modulation frequency band can be narrowed, thereby also improving the modulation distortion. can do.

According to a third aspect of the present invention, a demodulating means for demodulating the range tone signal modulated by the first modulating means is provided in the receiving apparatus. Can be demodulated.

According to the fourth aspect, since there is provided means for sending back the demodulated range tone signal to the transmitting device, it is possible to send back information of the range tone signal including the range tone signal modulated by the first modulating means to the transmitting device. it can.

According to a fifth aspect of the present invention, the transmitting apparatus further includes a distance measuring means for measuring a distance to the receiving apparatus based on information including the range tone signal returned from the receiving apparatus. Accurate ranging can be performed based on the signal.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of a signal synthesizing unit of a transmission apparatus using range tone modulation according to the present invention.

FIG. 2 is a circuit diagram of an embodiment of a signal separating unit of the receiving apparatus according to the present invention.

FIG. 3 is a circuit diagram of a second embodiment of a signal synthesizing unit of a transmission apparatus using range tone modulation according to the present invention.

FIG. 4 is a circuit diagram showing an example of a signal synthesizing unit of a conventional transmission device using range tone modulation.

FIG. 5 is a circuit diagram illustrating an example of a signal separating unit of a conventional receiving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 FM modulation part 11 FM demodulation part 51-53 Resistor 61-63 Band filter

Claims (5)

(57) [Claims] 1. A first modulating means for modulating a carrier of a predetermined frequency with at least the lowest frequency range tone signal among a plurality of different frequency range tone signals, and the modulated signal and the non-modulated range tone signal. And a second modulator for modulating a carrier having a higher frequency than the carrier with the combined signal. 2. The transmitting apparatus according to claim 1, wherein a frequency of a carrier of said first modulating means is set near a frequency of said unmodulated range tone signal. 3. A first demodulating means for demodulating a synthesized range tone signal, a signal separating means for separating the demodulated signal into respective range tone signals, and a signal which is still modulated among the separated range tone signals. And a second demodulating means for demodulating the carrier wave. 4. The receiving apparatus according to claim 3, wherein said receiving apparatus further comprises means for sending back information including a demodulated range tone signal to a transmitting apparatus. 5. The transmitting apparatus according to claim 1, wherein the transmitting apparatus further includes a distance measuring unit that measures a distance to the receiving apparatus based on information including a range tone signal returned from the receiving apparatus. Transmission device.