JPH05227066A - Weak radio wave communication system and transmitter using for the same - Google Patents

Abstract

PURPOSE:To provide a modulation signal based on any radio wave having higher electric field intensity between two polarization waves by sending two weak radio waves having polarization angles different at right angles on the transmission side and simultaneously receiving and demodulating two radio waves on the reception side. CONSTITUTION:Modulation circuits 15 and 16 of a transmitter Tx is provided with the signal source of two frequencies as close as not causing the leading-in. Modulated signals from these signal sources are modulated by the modulation wave from a pulse coding circuit 14. The output of circuits 15 and 16 are given to outgoing circuits 17 and 18, transmitted from an antenna as a radio wave with polarization angles different at right angles. The signal received by an antenna is amplified by a high frequency amplifier circuit 21, given to a detection circuit 22. A pulse signal is demodulated by the detection wave. The pulse signal is given to a pulse code processing circuit 23 and given to output circuits A to C as a signal corresponding to three modulation signals by sensors A to C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system using weak radio waves and a transmitter used in this communication system.

[0002]

2. Description of the Related Art Weak radio waves are widely used because they do not require a license under the Radio Law. Especially for the purpose of communication to the extent that it is used in household appliances, it is a very convenient radio wave.

[0003]

The weak radio waves that have been receiving such attention are caused by the directivity of the radio waves, and the electric field due to the phase interference between the reflected waves of the radio waves and the rectilinear waves due to the small radio field intensity. Degradation, and signal burial in external noise are problems.

FIG. 8 shows conditions for measuring radio wave propagation in space. A signal generator SG is connected to a transmission half-wavelength dipole antenna Tx to transmit a signal, and the transmission antenna Tx is separated by Xm. The signal level of the received signal at the 1/4 wavelength receiving antenna Rx at the point is measured by the spectrum analyzer SA.

FIG. 9 shows the environment in which this measurement is carried out. On both sides of the installation location of the transmitter Tx and the installation location of the receiver Rx, there is a building wall, behind the transmitter Tx as seen from the receiver Rx. Also has a building wall (not shown) with the balcony face in between. Therefore, there is a situation in which the reflection of radio waves is likely to occur.

FIG. 10 is a graph showing the actual measurement results, where f1 = 300 MHz, f2 = 303 MHz, and f3.
When propagation measurements were performed on radio waves of four frequencies of 306 MHz and f4 = 309 MHz, it was found that the receiving antenna level greatly fluctuates as the measurement position changes sequentially.

It should be noted here that the reception level is significantly different if the frequency of the radio wave is different even at the same point.

The present invention has been made in view of the above points, and provides a communication system which can communicate using an existing receiving device and has a sufficient communication capability as a weak radio wave, and a transmitter used in this system. The purpose is to provide.

[0009]

In order to achieve the above object, according to the present invention, on the transmitting side, two modulated waves having different frequencies close to each other are modulated by a modulating wave to generate signals of a first frequency and a second frequency. Formed and transmitted by the respective signals of the first and second frequencies, two weak radio waves having mutually different 90-degree polarization angles, and the receiving side receives the two radio waves together and demodulates them by weak radio waves A modulation wave generator that generates a modulation wave having a method and content to be communicated, a first oscillator that generates a signal of a first frequency, and a second oscillator that generates a signal of a second frequency A first modulator that modulates the signal of the first oscillator with a modulated wave by the modulated wave generator, and a second modulator that modulates the signal of the second oscillator with a modulated wave by the modulated wave generator And each of the first and second modulators The first and second transmitter for sending to each other the forces as two weak radio wave having different 90-degree polarization angle to one another, there is provided a weak radio wave transmitter, with a capital.

[0010]

According to the method of the present invention, the transmitting side transmits two weak radio waves having different 90 ° polarization angles based on two modulated waves having frequencies close to each other, and the receiving side simultaneously receives the two radio waves. Demodulate. In reality, the main component of the two polarized components is the one that is easier to receive, and the other component is the supplementary component. You can

In the device of the present invention, the signals of the first and second oscillators are modulated by the modulation wave from the modulation wave generator in the first and second modulators, and then are transmitted to the first and second transmitters. Given separately. These transmitters have 9
Two weak radio waves with different polarization angles of 0 degrees are transmitted. The receiver receives two weak radio waves at the same time, but mainly demodulates the one having the larger electric field strength.

[0012]

As described above, according to the present invention, the transmission radio waves are so close to each other that the frequencies do not pull in.
Since two radio waves with different polarization angles of 0 degrees are sent out and these two radio waves are simultaneously received and demodulated on the receiving side, a demodulation signal based on a radio wave with either of the two polarizations or the electric field strength is large. Therefore, much better communication can be performed as compared with the conventional method using only a single polarized wave.

[0013]

FIG. 1 shows an embodiment of the present invention. In the figure, Tx is a transmitter and Rx is a receiver.

In this case, the transmitter Tx modulates signals of two frequencies by three modulation signals and sends them out as signals having 90 ° different polarization angles. For this reason,
Three modulated waves from sensors A, B and C, which are represented by reference numerals 11, 12 and 13, respectively, are given to a pulse coding circuit 14 to form pulse signals corresponding to the modulated waves from these sensors, This pulse signal is given to the two modulation circuits 15 and 16.

The modulation circuits 15 and 16 have signal sources of two frequencies which are close to each other so that the pull-in phenomenon does not occur. The modulated wave signals from these signal sources are changed by the modulated wave from the pulse coding circuit 14. Is modulated. Modulation circuit 1
The outputs 5 and 16 are given to the transmitting circuits 17 and 18, and are transmitted from the antenna as radio waves having 90 ° different polarization angles.

[0016] This radio wave has a complementary function so that a portion that is behind the radio wave is unlikely to occur. Then, when both are received in the maximum state, a gain increase of 3 dB is obtained. In reality, the gain is increased by 1 to 2 dB due to phase disturbance or the like.

The receiver Rx mainly receives and demodulates a radio wave having a stronger electric field strength out of the two radio waves having different polarization directions from the transmitter Tx, performs pulse code processing, and reproduces three modulated signals. To do. That is, the signal received by the antenna is amplified by the high frequency amplifier circuit 21 and is detected by the detection circuit 22.
Given to. The detection circuit 22 demodulates the pulse signal by detection. Then, the pulse signal is applied to the pulse code processing circuit 23, and the output circuits A, B and C are provided as signals corresponding to the three modulated signals by the sensors A to C.
Given to.

2 (a) and 2 (b) are diagrams showing the radio wave phase disturbance as a signal waveform.

First, FIG. 1 (a) shows an outdoor radio wave propagation situation, in which the radio wave transmitted from the transmission point a0 reaches the reception point a1 after passing through the reception point a1 and reflected by the wall a2. To explain.

From the transmission point a0 to the first frequency 300 MH
f1 direct wave that is the radio wave of z, and the second frequency 306
While it reaches the reception point a1 as f2 direct wave which is a radio wave of MHz, it reaches the reception point a1 as radio waves f1 ′ and f2 ′ which have passed through the reception point a1 and are reflected by the wall a2.
In this case, the direct wave and the reflected wave are usually out of phase with each other.

Therefore, at the reception point a1, two signals having the same frequency but different phases are received. As a result,
As the received signal, the signal level is lowered due to the cancellation of the direct wave and the reflected wave. If the phase difference is 180 degrees at the same level, the signal becomes zero.

In this respect, when radio waves of two frequencies are used,
Even if the signal f1 of one frequency has a phase opposite to that of the reflected wave and cancels each other and cannot be received, the signal f2 of the other frequency has a different phase shift, so that either the direct wave or the reflected wave is strong. It can be received.

FIG. 2B shows the state of radio wave propagation indoors, in the case where there is an obstacle b3 such as a building wall or furniture on a straight line from the transmission point b0 to the reception point b1. Shows the relationship between the direct wave and the reflected wave.

As shown in the figure, when passing through the obstacle b3, the radio wave is greatly attenuated and reaches the reception point b1. On the other hand,
The radio waves f1 ′ and f2 ′ reflected by the radio wave wall b2 without passing through the obstacle b3 also reach the reception point b1. In this case, the reflected wave becomes stronger than the direct wave, and the tendency becomes stronger as the frequency becomes higher. When single wave communication is performed in such a situation, it is customary that a communication failure occurs.

The present invention is also effective as a countermeasure against this, and two radio waves having different frequencies and different polarization directions are used to compensate for the valleys of the radio waves, and the communication failure occurs even when the direct wave and the reflected wave interfere with each other. Is meant to be avoided.

Further, in FIG. 2 (b '), the composite wave f1''has a very small level for one of the two frequencies, but the other one has a different phase. The degree of deviation is different, and the level of the composite wave f2 ″ is considerably large, which makes it difficult to cause a communication failure.

FIG. 3 shows the main structure of the transmitter Tx in the circuit of FIG. That is, the pulse coding circuit 14 is responsive to signals from three sensors (not shown).
Forms a pulse signal and supplies it to the modulation circuits 15 and 16 as a modulation signal. The modulation outputs of the modulation circuits 15 and 16 are given to the transmission circuits 17 and 18, respectively,
It is transmitted as transmission signals f1 and f2.

It is desirable that the frequencies of these signals are selected such that the two frequencies are shifted with respect to one frequency within a limit of ⅛ wavelength with respect to the other frequency in addition to the condition that the pull-in phenomenon does not occur. Therefore, the two frequencies must be reasonably close and well separated.

In order to avoid the pull-in phenomenon, the positions of the two transmitting circuits 17 and 18 may be moved away from each other. For example, the upper and lower sides or the right and left sides of the same substrate may be used. A shield for preventing interference between signals of both frequencies may be omitted.

The outputs of the oscillator circuits 17 and 18 are adjusted by adjusting variable resistors VR1 and VR2. In addition, power supply B
Feeds each of the modulation circuits 15 and 16 and the transmission circuits 17 and 18 so as not to interfere with each other via the inductors.

FIGS. 4 (a) and 4 (b) are schematic diagrams showing the circuit arrangement for preventing interference of two frequencies in FIG. 4 (a), and FIG. 4 (b) of the present invention. It is a figure which shows the directional characteristic of the transmitted wave by a device.

As shown in FIG. 3A, the circuit elements are arranged to prevent interference as much as possible, and two dipole antennas A
Radio waves of two frequencies having 90 ° different polarization angles are transmitted from NT1 and ANT2.

FIG. 2B shows these two antennas ANT.
1 shows the radiation directivity characteristics of ANT2, antenna A
The NT1 has a donut shape centered on the dipole 11, and the antenna ANT2 has a donut shape centered on the dipole 22. Therefore, the electric field strength becomes highest in the direction perpendicular to the dipole, and the electric field strength becomes weakest in the extension direction of the dipole.

FIG. 5 shows the frequency spectrum of the radio wave transmitted from the transmitter and the reception frequency characteristic of the receiver. That is, there is generally a difference in the strength of the received radio waves f1 and f2 from the receiver, and in the case of the figure, the peak value P of the frequency f1 is obtained.
The peak value of the frequency f2 is smaller than that of o by P.

Thus, there are two frequencies f1 and f with two levels.
When a receiver having a bimodal characteristic shown in the figure receives a radio wave having a bimodal characteristic having a peak at 2, the reception characteristic has two frequencies f.
The overall characteristic is that the reception level decreases at frequencies between 1 and f2.

FIG. 6 shows the two transmitting antennas A of FIG. 4 (b).
The directional characteristics of NT1 and ANT2 are shown when the antenna ANT1 is cut on a horizontal plane and the other antenna ANT2 is cut on a vertical plane.
Both ends 11 of the dipole 11 for the antenna ANT1
The maximum level is obtained in the direction 1aL which is orthogonal to the direction connecting a and 11b, and the dipole 22 is used for the antenna ANT2.
Direction 2aR orthogonal to the direction connecting both ends 22a, 22b of the
Is the maximum level.

FIG. 7 shows transmitting antennas ANT1 and ANT2.
It shows the result of actually measuring the radio wave transmission characteristics of
When the transmitter is rotated 360 degrees about the dipole 22 of the antenna ANT2 (this is referred to as rollover) and when it is rotated about the dipole 11 of the antenna ANT1 by 360 degrees (this is referred to as vertical roll). It is a plot of the reception sensitivity at the same reception position in every 20 degrees.

Near 20 degrees and 180 in FIG.
A valley at a vertical rotation of 306 MHz appears near the degree, and a valley at a horizontal rotation of 300 MHz appears near the 110 degrees and 290 degrees. No significant valley appears at 300 MHz in the vertical direction and 306 MHz in the horizontal direction. This is the effect of transmitting radio waves of two frequencies with their polarization directions shifted by 90 degrees.

In the above embodiment, the signals of two frequencies are pulse-modulated at the same time, but each frequency may be separately modulated for alternate transmission. However, the effect of adding 3 dB at the maximum when both frequencies are added disappears.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

2A and 2B are diagrams showing a radio wave phase disturbance as a signal waveform.

3 is a diagram showing a detailed configuration of a main part of a transmitter Tx in the circuit of FIG.

FIG. 4A is a diagram schematically showing a circuit arrangement for preventing interference of two frequencies.

FIG. 5 is a diagram showing a frequency spectrum of a radio wave transmitted from a transmitter and a reception frequency characteristic of a receiver.

FIG. 6 is a diagram showing two transmitting antennas ANT1 and AN shown in FIG.
The figure which showed the state when the directional characteristic of T2 was cut | disconnected by the horizontal surface about antenna ANT1 and the vertical surface about another antenna ANT2.

FIG. 7 is a diagram showing a result of actual measurement of radio wave transmission characteristics of transmission antennas ANT1 and ANT2 by an electrometer.

FIG. 8 is a diagram showing a method of measuring radio wave propagation in space.

9 is a diagram showing an environment in which the measurement of FIG. 8 is performed.

FIG. 10 is a graph showing a result of actual measurement according to FIG.

[Explanation of symbols]

 Tx transmitter Rx receiver

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuyoshi Takeuchi 1-22-12 Higashimagome, Ota-ku, Tokyo

Claims (4)

[Claims] 1. A transmitting side modulates two modulated waves having different frequencies close to each other by a modulating wave to form signals of a first and a second frequency, and each of the signals of the first and second frequencies. Is a communication system using weak radio waves in which two weak radio waves having different 90-degree polarization angles are transmitted, and the receiving side receives and demodulates the two radio waves together. 2. The communication system according to claim 1, wherein the first and second frequencies have a difference to the extent that they do not attract each other. 3. A modulated wave generator for generating a modulated wave having contents to be communicated, a first oscillator for generating a signal of a first frequency, and a second oscillator for generating a signal of a second frequency. An oscillator, a first modulator that modulates a signal of the first oscillator with a modulation wave generated by the modulation wave generator, and a second modulator that modulates a signal of the second oscillator with a modulation wave generated by the modulation wave generator And a transmitter for transmitting the respective outputs of the first and second modulators as weak radio waves having 90-degree polarization angles different from each other. 4. The transmitter according to claim 3, wherein the first and second frequencies have a difference that does not cause pull-in.