JPS61198825A - Diversity reception method by s/n selection of broadcast data signal - Google Patents

Abstract

PURPOSE:To ensure continuously a communication line with high quality with a minimum equipment at the reception (mobile body) side by comparing the S/N of signal outputs demodulated at each reception system in the unit of bits of the signal so as to output only a demodulated output of the reception system having the best S/N at all times to a reception terminal equipment. CONSTITUTION:For example, frequencies for two waves each per station are assigned in advance to a fixed station, assigned frequencies of f1, f2 from a station A1, f3, f4 from a station A2 and f5, f6 from a station A3 are used to send the same data in the simultaneous broadcast mode. In this case, the stations A1-A3 are parted remotely and each mobile station selects the optimum frequency for reception depending on the reception point of the own station, season and reception time. A central station C and each transmission station are connected respectively by a private line (e.g., a microwave line or a cable) and the data sent from the central station C is irradiated at the same time by using a frequency depending on each transmission station. As a transmission terminal equipment 1, a computer, a typewriter, or paper tape reader to generate the transmission data is used.

Description

Detailed Description of the Invention (Technical field to which the invention pertains) The present invention transmits data signals constantly radiated in broadcast format from multiple transmitting stations of fixed stations or from multiple fixed stations to stations scattered geographically far away from the fixed stations. The present invention relates to a reception method for ensuring that a specific number of mobile stations receive data of good quality.

(Prior art) When transmitting data from a terrestrial fixed station to an unspecified number of mobile stations using radio waves mainly in the IP (shortwave) band, conventionally the transmitting side divides the available transmission band into multiple channels. A frequency diversity method in which the same transmission code is input to each channel and sent out into the air from one transmitting station equipment, and the mobile station simultaneously receives, demodulates and combines multiple channels, and similarly transmits radio waves from one transmitting station. The polarization plane is transmitted as a combination of horizontal and vertical polarization, and the mobile station receives each polarization plane, demodulates it, and then combines it. Alternatively, the transmission code is transmitted by repeating it many times at regular time intervals. On the receiving side, either a majority vote of multiple recovery modulation codes or a time diversity method that performs error checking is used. However, with either method, it is difficult to almost completely remove obstacles on the propagation path, and especially in broadcasting communications to an unspecified number of moving objects, the optimum operating frequency changes in the HF band due to the distance between transmitting and receiving points, and data In other words, it has been difficult to transmit high-quality digital codes, and on the other hand, many techniques related to antennas have been difficult to implement.

(Specific object of the invention) The purpose is to continuously receive high-quality reception for an unspecified number of moving objects that move over a wide area, especially aircraft, automobiles, ships, etc. that are located in a wide area and move at a high speed. It is characterized by good transmission to and economical mobile station equipment.

(Structure and operation of the invention) FIG. 1 shows an example of a communication system in which the present invention is implemented.
--1 is a fixed station, B+, Hg, -----B- is a mobile station. For example, two frequencies per round are assigned to the fixed station in advance, A, and f+, b, A from the station.
The same data is transmitted in the simultaneous broadcast mode using the allocated frequencies of f3° f4 for A, and 1% f for A. In this case A+.

A2. The A3 stations are far apart from each other, and each mobile station selects and receives the optimal frequency depending on its own reception location, season, and reception time.

FIG. 2 is an example of the communication system that is the mainstream of the present invention, where C is the central (fixed) station and AI+II! ＋＾, refers to transmitting equipment or transmitting stations located at mutually remote locations, hereinafter referred to as transmitting stations. The central station C and each transmitting station are connected by dedicated lines (for example, micro lines or wired lines), and data sent from the central station C is simultaneously radiated from each transmitting station using different frequencies.

Although FIG. 3 is a block diagram of an example of the configuration of a communication system between the central station and each transmitting station in FIG. 2, it can also be applied to the block diagram of a transmitting system at each fixed station in FIG. 1. In FIG. 3, 1 to 4 are central office equipment, 5 to 10 and TXI to TX3 are transmitting station equipment, and the transmitting terminal 1 includes a computer, typewriter, paper tape league, etc. for generating transmission data. 2 to 4 are modulators for each dedicated line that transmit data from the transmitting terminal to distant transmitting stations A and -A, respectively, and perform PSK (phase shift keying) or FSK (frequency shift keying).
The signal is simultaneously transmitted to each of a plurality of (three in this example) transmitting stations at a speed of about 1200 bps to 2400 bps using a modulation method such as . 5 to 7 convert the modulated signal transmitted by the demodulator at the dedicated line input end provided at each transmitting station into a digital signal.

Figure 4 shows an example of the spectrum of the modulated wave transmitted on the dedicated line between the central station and each transmitting station, and shows the transmission band (
For example, one channel of subchannel f within 3 kHz)
This is a case where data is transmitted using time division multiplexing using 0.

Returning to Figure 3, 8 to 10 are HF (short wave) modulators.
The time-division multiplexed digital signals from the demodulators .about.7 are transmitted through a plurality of subchannels f arranged within a transmission band Δf (for example, 3 kHz) as shown in FIG. , flll+------
--" r n - + l f 1.1 and simultaneously modulates it, which is called FDM (frequency division multiplexing) PSK or FSK modulation. Like HF lines, this involves fading and multipath due to ionospheric propagation. In wireless lines, the transmission speed per subchannel is 150bp.
This is adopted because the limit is about 3kHz.In a normal HF line, when Δf is about -3kHz, the transmission speed per subchannel is 75 to 150bps, and the number of subchannels is 1.
6, the overall transmission speed is 1200 bps to 2400
bps. TXI to TX3 are transmitters set to one wave among f1 to f6, respectively, and ANT 1 to ANT 3.
is the transmitting antenna. Conical, inverted cone, and rotating log periphery antennas are used for transmitting antennas. Note that the mobile receiving stations B and B1 can be aircraft, ships, trains, land vehicles, etc.

6 and 7 are block diagrams of configuration examples of the receiving device of each mobile station (details of the configuration will be explained later). In FIG. 6, the mobile station uses two receiving devices in a space diversity method. Figure 7 shows a case in which a mobile station selects one transmitting station and receives the data of its one transmitted wave, and in Fig. 7, the mobile station receives data from three transmitting stations using three sets of receivers, each using a space diversity method. This is a reception method that combines both space diversity and frequency diversity methods, in which received data from each transmitting station is automatically selected bit by bit and output. In order to produce this effect in such frequency diversity reception, for example, in the case of a combination of fl and fs, the operating frequencies (carrier waves to be emitted) are selected so that these three frequencies are close to each other. The choice between the method shown in FIG. 6' and FIG. 7 will be determined depending on cost and equipment availability.

In Fig. 6, RXI and RX2 are receivers, and normally two sets of receivers are used in this way, and a pair of antennas that supply input to each are separated for a while, and the propagation path of the input radio waves to the antennas is A two-system diver single reception system is used based on the space and the angle of incidence of the polarization plane, which takes advantage of the difference in the incident polarization plane.

11 and 12 are demodulators that convert the low frequency signal output from the receiver into 2
Convert and output to a hexadecimal digital signal. Although a PSK or FSK demodulator is used in the present invention, the case of PSK demodulation will be described here. The S/N (signal-to-noise ratio) of the demodulator outputs for each of the two receiving input systems is constantly measured for each system, and the output with the better S/H is selected for each focus.

In other words, 13 is an S/N comparator that converts 11 and 12 bit by bit.
The outputs of the two systems are compared, and only the data output of the system with the better S/N is sent to the receiving terminal 15 (eg, puncher, typewriter, computer) by controlling the switch 14.

Next, in FIG. 7, a, b, and c are respectively the fixed stations or transmitting stations shown in FIG. The parts are almost the same except for the receiving terminal 15. 16 is a switching circuit which inputs the data selected by the space diversity reception method from each device a, b, and c, and at the same time inputs the current S/N information in bit units, so it is possible to Only the best data is selected and output to the receiving terminal 15.

Next, the configuration of the modulated wave and the demodulation method on the receiving side will be explained.

(1) In the case of PSK modulation (see Figures 8 to 13) Section 8
The figure is a time chart for creating a two-phase PSK modulated signal wave for one channel among the subchannels. The leftmost number (1) is the carrier wave,
(2) is a digital code output from the transmitting terminal 1 during transmission, and in this example it is 010110--.In this modulation, if the same code continues, such as 11 or OO, the code will change as shown in (3). The phase of the carrier wave does not change at the change point, but when the sign differs from the previous bit, such as 01 or 10, the phase advances or lags by π radians.

In the waveform (3), there is a π radian change at each point A, B, C, and H, and there is no phase change at point D.

Figure 9 is a diagram showing the relationship between the phase change θ of the receiving side demodulator and the output voltage V. Based on these characteristics, the digital signal of 1, 0 (
2) can be detected.

Figure 10 (1) is a side view of the configuration of a 4-phase PSK modulation circuit.
In the case of two-phase PSK, the phase changes in response to changes in the modulation input code are 0 and π, but in the case of four-phase PSK, the phase changes in steps of π/2. In the figure, 17 is a carrier wave oscillator, 18 is a signal distributor, 19 is a level adjustment attenuator, and its output is the first
It is assumed that the vector L1 in Figure 0 (2) is obtained.

21 is a π/2 phase shifter whose output is 2, which is the vector L2 in (2), and has a phase difference of π/2. 20 and 2
2 is a phase modulator which changes the phase by O or π as shown in FIG. 8 in response to digital signals A and B (as shown) from the terminal device. It will be explained below that when the two-phase PSK waves from 20 and 22 are combined in the mixer 23, a four-phase PSK wave is obtained. Since modulation can be performed using each digital signal, the transmission capacity can be twice that of two-phase PSK. Therefore, in 4-phase PSK of FDM (frequency division multiplexing) system, if the symbol rate per channel is 75 bps and the number of subchannels is 16, the transmission speed is 75 x 2 x 16 = 24 Q Obps.
becomes.

Here, each time a four-phase PSK modulated signal is generated by the mixer 23 will be explained with reference to FIGS. 10 (3) to (6). As an example, the modulated input signals to modulators 20 and 22 are input to the A channel.
0101------------B channel 0
011.--1---------. When both A and B are "O", the modulated wave vector of the A channel is O.
When the modulated wave vectors of the P, , and B channels are combined by OR2, 0PoI as shown in FIG. 1O (3) is obtained.

Next, A is 1. When B is 0, only the A channel changes by 0-1, so the phase of Pl advances by π, and the composite vector becomes 0P02, as shown in FIG. 10 (4). Then A is 0
．． When 8 is 1, PI is the same as (3) and only R2 has a phase advance of π, so the composite vector is 0 as shown in Figure 10 (5).
It becomes P03. Furthermore, if both A and B are 1, if we think in the same way, the resultant vector will be 0P04 as shown in Figure 1O (6)
It is clear that

In this way, each subchannel (1
) A high-speed modulator for an HF line can be obtained by creating a four-phase PSK wave using a circuit such as the one shown in FIG.

Next, a receiving circuit for four-phase PSK waves will be explained.

FIG. 11 is an example of the configuration of a receiving circuit that receives an FDM 4-phase PSK wave in a two-receive system diversity system and outputs data to a terminal device.
6 of FIG. 6 and FIG. 7.

Rx in FIG.

Rx2 is a receiver for each receiving system, and 61 and 62 are distributors, and the band for distributing the output of the receiver to each subchannel for each receiving system includes a wave device group. CHI~CHn, Cl21~CH2
It is divided into n demodulation circuits and input. The circuit of one of these subchannels, CHI, will be explained below. Furthermore, C)
A portion including 65 to 69 and 610 in II is a circuit forming a delay detection circuit for input data.

Now, one channel (hereinafter referred to as C) of the subchannels of the 4-phase PSK wave
The PSK wave of
---= (1-1). In the case of 4 phases, φ5=(π/2) fli+φ. −1−−−・−・−
...-(1-2) However, ni is a four-level code determined by the combination of the two i-th codes of the modulation PCM codes for both channels A and B, that is, nz = o, 1.2.3
It is.

Therefore, φ! in equation (1-2)! 1 is φi−+ = n=−+ +φO・−−−−−−−
--------(1-3) Therefore, the PSK wave E and the PSK wave delayed by 1 code (bit) (denoted as Ea) are E = ACO5 (6J t + -ni +φo)
'-------'il 4) Ea "A4 co
s(ωt + ni−+ +φo)−−−−−(1
5: It will look like this. E4 in (1-5) corresponds to the output of the delay circuit 67 in FIG. 11, and the delay amount τ=T (T is the time of one bit), which is one bit. Further, if E is divided into two and one phase is delayed by π/2, the output Ep is expressed by the following formula (',' cos (θ-2)=sinθ)Ep = A
sin(ωt +−ni +φ, > −i−(t−6)
The waveform of the output of the π/2 phase shifter 65 in FIG. 11 is expressed by this equation. Further, when the waveform of Ed is delayed by π/4 by the π/4 phase shifter 68, the output E' a is expressed by the following equation.

-・-・・-(1-7) Next, divide E'a into two and divide each of them into 6
The outputs R1 and R2 of 69 and 610 are inputted to the product circuits 9 and 610, respectively, and the DC components are extracted as follows.

・---------(1-8) Here, nl-1 and nyu are quaternary numbers (0, 1, 2, 3)
Therefore, ni nl-1 is -3, -2, -1, 0,
It takes a value of 1,2°3. 66 is an attenuator for level adjustment and has the same attenuation amount as the π/2 phase shifter 65. R1. for each value of the phase ni*nl-1 based on these.
Calculating Rz results in the following table.

However, it is assumed that A-Aa/2=1.

Tables 1 (1-8) and (1-9) show the phase and detection output in the case of delayed detection. Now, since n1ni-1 is a quaternary number and takes the value described above, -3, -2, and -1 can be read as 1 and 2.3 shown in parentheses, respectively. Also, when R,, R2 is -1, it is 1°, and when it is 1, it is read as O, then R+, Rz is ni, ni-
1 is expressed as a binary code of 0.1, which is 69.610
The output after delayed detection is obtained as the output.

The circuits after 69 and 610 are parts that perform code processing on the delayed detection output, and 611 and 614 are DC amplifiers, and 612°6
15 is an integrator, 613.616 is a sampling circuit, 6
Reference numeral 17 denotes a switching circuit (2) for switching the sampling circuit outputs of the two R+ and Rz systems and outputting them as one continuous signal.

FIG. 12 is a waveform diagram of each part of the circuits 611 to 617, and (1) and (2) in the figure are l? of the two receiving systems. It shows the output waveform of the multiplication circuit corresponding to 69 of one of the subchannels received simultaneously on
=1/75-13.3+as. (3) is RX,
(7) Output waveform of integrator 612, (4) is S of 618
A /N circuit compares R9 from 69 and R2 from 610, for example, S+N, extracts a high level S/N signal, and integrates it in an integrating circuit 619. This is the waveform. Also (71. (
8) is the output waveform of the same integrators 612 and 619 of the RX2 system. Based on this integration time and the integration result in (3), the clock that triggers the sample of 1.0 of the data is R.
An important aspect of the present invention is that the receiving systems of X and RXz are synchronized bit by bit. In other words, (5) determines the integration time per bit using the quench pulse of clock (abbreviated as CM) 1, and (6) determines 1.0 or S/N for each bit using the sample pulse of CK2. . Furthermore, l? In the XZ series, CKI and CK2 are each CK2.
1. It becomes CK22.

When there is one subchannel, the S/N judgment of the receiving system is
The channel used for /N determination matches the signal channel, but if there are multiple subchannels, one channel is
/N determination to determine the overall S/N, and perform diversity signal selection switching. In the example of Figure 11, CHI and CH
21, that is, S/N using one subchannel for each receiving system.
Judgment is being made. (9) is the sample signal waveform of the R1 system, that is, the 611-612-613 system taken out from the switching circuit 1 of 617, and the switching circuit 617 alternately switches and outputs the R, system and R2 system sample signals. (9)
waveform to the differentiating circuit 621.

When input, the output is the conversion point pulse 1 as shown in α
becomes. This conversion point pulse 1 causes the crystal oscillator 626 to
．． Frequency divider 627. The timing generation circuit 628 is operated and the clock CK1. CK2. CK21.
Create 22 timing on C. In other words, the focus conversion point is extracted from the received detection output digital signal and the first
The phase correction of the quench pulse CKI and sampling pulse CK2 in Figure 2 (51, (6)) is always performed for each receiving system of RX, R, and CK1, C in Figure 11.
K 2 , CK21°CK22 correspond to this. R
Which bit, XI or RXz, is to be adopted is determined by the S/N comparison circuit 630 of both receiving and receiving systems, and the switching circuit 631 is activated every 7) based on the resulting switching selection signal. output the signal. These will be explained in more detail below.

The level of the S/N integral output of each receiving system shown in (4) and (8) in FIG. A switching signal is sent to the switching device 631 to make the output of the better receiving system after comparison judgment.The phase of the clock system is also corrected by the conversion point pulse from the differentiating circuit 621 on a bit-by-bit basis. The switch 629 uses the signal (output of 630) of the system with the better S/N so that bit synchronization is performed by the system with the better S/N.

Normally, when performing S/N determination of a 4-phase PSK wave, the signal vector is determined by the sign as shown in (3) to (6) in Fig. 10.
s, OP o a, so if the S/N is good, at least the area within the broken line area centered on each op vector shown in Figure 13 is considered to be the signal component vector, and the area outside the broken line area is the noise component due to interference or external noise. be. That is, R,
, Rg system, the difference between the signal component and the noise component is extracted as an S/N component in the S/N circuit 618 using the phase angle versus voltage characteristics as shown in FIG. Integrate bit by bit and +4 in Figure 12),
+8) is obtained.

63 and 64 are code processing circuits that input each subchannel signal received by the receivers RX, RX in parallel, one bit at a time, and perform character synchronization, error correction processing, etc., and this output is input to a switch 631. S from the comparator circuit 630
The /N determination signal makes it possible to always output a digital signal that is subjected to bit-by-bit diversity processing.

The above is based on the reception data selection method shown in Fig. 6, in which one of the multiple transmitting stations is arbitrarily selected in advance, and the RX is transmitted at that transmission frequency.
RX! This is a reception method that presets the reception frequency channel of 2 and performs space and polarization diversity by bit-by-bit S/N determination.

On the other hand, the reception data selection method shown in FIG. 7 basically uses the receiving circuit shown in FIG.
circuits), each receiving system is pre-centered to the emission frequency of the other transmitting station, and each receiving system is received using the space and polarization diversity method. This is a method of selecting a good value of N and automatically outputting the data. Specifically, 63 in Figure 11
The S/N judgment of each receiving system is output from the output of 0, and the three S/N judgments are output.
This is a method in which data with the best S/N is further selected one pin at a time from N and subjected to code processing, and employs frequency diversity in addition to space and polarization diversity. In this case, if there is a large difference in the emission frequency of each transmitting station in the HF line (for example, 6 Mn2 and 9 Mn2), the effect of S/N switching based on frequency will not be much.
For example, when the difference is small, such as between 6.2 MHz and 6.3 MHz, the effect of switching based on bit-by-bit S/N due to frequency diversity becomes noticeable and contributes greatly to improving the quality of received data.

(2) In the case of FSK modulation (see Figs. 14 and 15) Fig. 14 shows the signal spectrum per IC 11 of the FSK modulated wave, and the vertical axis represents the level height, f68. is the mark frequency and fol is the space frequency. Depending on the input binary digital signal, the modulator switches between mark and space frequencies to produce modulated signals. foI is f
olTll and f. 1. is the center frequency of

If the S/N of the received wave deteriorates, f@1m+ and f09. The f61 component in the common noise region increases and the spectrum changes from (1) to (2) in FIG. 14. Therefore, on the receiving side, f08. and fulls components (
The difference between S) and f01 component (N) is used as S/N.

Figure 15 is an example configuration diagram of a receiving side device for FSK modulated waves.
This corresponds to FIG. 11 for K.

RX+, RXz and their respective antennas in the figure constitute two receiving systems similar to those in FIG. 11. 71.7
Reference numeral 2 denotes a distributor that distributes the subchannel signals received and demodulated in each receiving system to each channel, and is composed of bandpass filters for each channel. This output is RX, and in the receiving system from CHI to C
Cl21 in the RX2 receiving system for subchannels up to Hn.
It is divided into subchannels from C) to C)12n, of which channel CHI will be explained first.

75 is a common amplifier, and 76, 77, and 78 are bandpass filters that extract the mark frequency, center frequency, and space frequency, respectively. Normally, when arranging about 16 CH FSK subchannels in a 3 kHz band, for example, the center frequency is set to fo, and the shift width is ±45.5 Hz around fo at approximately 110 Hz intervals as shown in Figure 5. Since the subchannel arrangement is performed, the bandwidth Δf of these bandpass filters is
is approximately ±10H7. Reference numerals 79, 80, and 81 are amplifiers, and 82, 83, and 84 are diode detectors, where the input is converted into a DC component to obtain detection outputs of a mark signal, a center frequency component, and a space signal, respectively. A differential amplifier 85 extracts mark and space signal components and sends them through an amplifier 88 to an integrator 89, where the signal components are integrated bit by bit.

Reference numeral 90 denotes a sampling circuit 1 which has the role of extracting a signal from the integrator 89. Further, 86 is an adder for both mark and space signals, and the adder 87 takes the difference between the adder output (signal component) and the detection output (noise component) of the center frequency, and uses this as an S/N signal component for the amplifier. After amplification in step 91, the S/N signal is integrated one bit at a time in an integrator 92.
A sampling circuit 2 extracts the S/N component.

Reference numeral 95 is a comparison circuit that compares the RX from 93, the S/N component of the receiving system (> S/N component of CH1), the RX, and the S/N component of the receiving system (for example, Cl21), and selects the better receiving system. Accordingly, the switch 2 of 97 outputs the receiving system signal with a better S/N as the output signal, as in the case of FIG. 11.

In this way, in the case of FSX modulation, the code processing after diode detection is the same as in the case of PSK modulation, and the timing is exactly the same as in the time chart of FIG. 12.

That is, the quench pulse of clock CK1 and CN21.

CN3. The phase timing for the sampling circuit of CN22 is the same as (5) and (6) in the time chart of FIG. Differentiating circuit 9 outputs the sampling circuit 93
4 and its output, the conversion point pulse 1, is sent to the switching circuit 101. 98 is a crystal oscillator, 99 is a frequency divider,
100 is a timing generation circuit whose operation is exactly the same as in the case of FIG. Similarly, the switching circuit 101 is provided to switch to a receiving system timing with a good S/N ratio on a bit-by-bit basis. Also, 73 and 74 are RX
+, A code processing circuit that inputs the sampling output of each subchannel of the RXz receiving system in parallel and performs code processing such as parallel-to-serial conversion and error correction.The code of each subchannel is switched one bit at a time. It is sent to a circuit 97, and if selected there, is sent to the receiving terminal device. As described above, this circuit system can be adopted in both the data reception systems shown in FIG. 6 and FIG. 7, as in the case of the PSK modulation system.

Figure 16 is a time chart of data transmission and reception when the present invention is implemented, in which (1) to (4) are on the sending side, (5)
~(8) is the receiving side. (1) is a transmission command signal from the central station C in FIG. 2 to each transmitting station, and the transmitters at each transmitting station start broadcasting from time A. (21, (3), (4) are wireless data signals sent from each transmitting station A1-8, respectively, and the same data from the central station C is simultaneously broadcast from each transmitting station on different frequencies. Among the signals, 5YNC is a synchronization signal and is sent before data transmission. On the receiving side, bit synchronization and frame synchronization (character synchronization) are set by this 5YNC. Data is sent following 5YNC, but B in the figure -C specifically illustrates the data to be sent as a binary code. That is, the data sent from time B is as follows: 0110100110--.

The transmitting frequency is A, (transmitting station) is f, ((2)
Data of〕.

A2 becomes f3 ((data of 31)), A3 becomes fs (data of (4)).

Next, (5) to (8) are data received by one mobile unit, for example B, among an unspecified number of mobile units, and (5)
) is the data from the A transmitting station as f, (6) is the data from the A2 transmitting station as f, and (7) is the data from the A3 transmitting station as fs, which is the receiving frequency of each receiver. This is a case where data is preset and received using the data reception method shown in FIG. In this case, the mobile side (mobile station) manually briscents to the frequency of the reception channel with the best quality and receives using the space/polarization diversity method. (8) is the seventh
As shown in the figure, three waves of data from each transmitting station are received simultaneously,
Furthermore, it is assumed that the data is received using the frequency diversity method. In any case, it is difficult to completely eliminate errors in received data in long-distance wireless lines that are subject to fading, multipath, etc., such as IP lines. It is necessary to receive the same data using a diversity reception method so that a communication line with the best quality can be constructed at all times.

(Effects of the Invention) By implementing the present invention, when performing broadcast-style data transmission using the minimum operating frequency to an unspecified number of moving bodies scattered over a geographically large distance, the communication situation changes from moment to moment. In contrast to wireless HF lines, which have a large number of connections, it is possible to secure continuous high-quality communication lines on the receiving (mobile) side with minimal equipment. Therefore, it can be expected to make a significant contribution to downsizing transmission and reception equipment and improving transmission efficiency.

[Brief explanation of drawings]

FIG. 1 is an example diagram of a communication system in which the present invention is implemented;
FIG. 2 is a diagram of an example of the communication system that is the main object of the present invention, and FIG. 3 is a separate diagram of the configuration of the communication system between the central station and each transmitting station in FIG. 2.
Figure 4 is an example of the spectrum of the modulated wave transmitted between the central station and each transmitting station, Figure 5 is an example of the spectrum arrangement of multiple subchannels arranged within the transmission band, and Figures 6 and 7. Figure 8 shows an example of the configuration of a receiver for each mobile station, Figures 8 to 13 are diagrams related to PSK (phase shift) modulation, and Figure 8 is a time chart for creating two-phase PSK modulated waves for one channel among subchannels. , Fig. 9 is an example diagram of demodulator phase change vs. output voltage characteristics, and Fig. 10 is an example diagram of a 4-phase PSK modulation circuit configuration (1)
and explanatory vector diagrams (2) to (6) for four-phase PSK wave generation,
Figure 11 is a configuration example diagram of a 4-phase PSK wave receiving circuit, Figure 12 is a time chart of received signal processing, and Figure 13 is a 4-phase PSK wave receiving circuit.
Comparison diagram of K wave signal component and noise component, Figure 14 is FSX
(Frequency shift) Example diagram of one channel spectrum of modulated wave,
FIG. 15 is a configuration example diagram of an FSK wave receiving circuit, and FIG. 16 is a time chart of data transmission and reception when the present invention is implemented.

Claims (1)

[Claims] In order to continuously transmit data in broadcast format to an unspecified number of geographically dispersed mobile units, the same data is simultaneously sent from a land-based central fixed station to multiple transmitting stations distributed over long distances via dedicated lines. Generally speaking, each transmitting station uses carrier frequencies close to each other, allocates an arbitrary number of subchannels within its exclusive bandwidth, and modulates these subchannels with a phase shift or frequency shift when radiating. On the mobile side, multiple receiving systems are installed, each consisting of multiple antennas and receiving circuits, with space and polarization diversity of two or more systems plus frequency diversity up to the number of transmitting stations, and each receiving system is always tuned to the optimum frequency. Adjustments are made in advance to select a transmitting station for reception, and the signal-to-noise ratio (S/N) of the demodulated signal output of each receiving system is compared on a bit-by-bit basis to constantly check the signal-to-noise ratio. A diversity reception method using S/N selection of broadcast data signals, characterized in that only the demodulated output of the best reception system is output to a reception terminal device.