JPH0243385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital communication device that is resistant to multiple wave interference.

[Conventional technology]

When there are multiple waves arriving via different propagation paths, as in mobile radio, the bit error rate deteriorates, so it was considered extremely difficult to configure a digital communication line.

One solution to this problem is the BPSK-RZ method (Binary Phase Shift Keying-Return to
zero) has been devised. BPSK-RZ signal is
It is obtained by multiplying the normal BPSK signal shown in FIG. 2a by an ON-OFF signal which is "1" only in an arbitrary interval of T/2 of the time slot shown in FIG. 2b. In other words, the BPSK-RZ signal has the same amplitude and phase as a normal BPSK signal in the T/2 period in the first or second half of each time slot, and the carrier wave amplitude is effectively zero in the remaining T/2 period. It is.

This multiplexed wave of BPSK-RZ signals is reproduced by the delay demodulator shown in FIG. In Fig. 3, 1 is an IN terminal, 2 is a multiplication circuit, 3 is a delay circuit with a delay time of unit time slot T, 4 is a low-pass filter, and 5 is a delay circuit with a delay time of unit time slot T.
is the OUT terminal.

At this point, the BPSK-RZ signal supplied to IN terminal 1 is connected to the first signal generated by the same digital information.
BPSK-RZ signal wave (hereinafter referred to as D wave),
The second wave whose arrival time is delayed by τ from this D wave
It becomes a signal (that is, multiplexed wave) that is a combination of BPSK-RZ signal waves (hereinafter referred to as U waves). Fourth
The figure is a diagram explaining the temporal relationship between D waves and U waves. Here, T is the length of the time slot in which one symbol of digital information is transmitted. Section a is the section from the rise of the D wave to the rise of the U wave, section b is the section from the rise of the U wave to the time T/2 of the D wave has elapsed, and section c is the section from the time T/2 of the D wave has elapsed. The section d is the section from the time T/2 of the U wave to the time T of the D wave.

Signal e obtained at OUT terminal 5 in each section
(t) is as shown in the following equation.

For 0<2/T<0.5; In interval a; 2e(t) = 1 −1 symbol “1” 〃 “0” In interval b; 2e(t) = 1+ρ ² +2ρcosφ −(1+ρ ² +2ρcosφ) 〃 “ 1” 〃 “0” In interval c; 2e(t)=ρ ² −ρ ² 〃 “1” 〃 “0” In interval d; 2e(t)=0 For 1>τ/T>0.5; In interval a Then; 2e(t)=1−ρ ² 1+ρ ² +2ρcosφ −(1−ρ ² ) −(1+ρ ² −2ρcosφ) Symbol change “0” → “1” 〃 “1” → “1” 〃 “1” → ``0'' 〃 ``0'' → ``0'' In interval b; 2e(t) = 1 -1 Symbol ``1'' 〃 ``0'' In formula 3 interval c; e(t) = 0 In interval d; 2e(t) ) = ρ ² - ρ ² symbols "1" 〃 "0" ρ: Relative amplitude ratio of U wave to D wave φ: Phase difference between D wave and U wave As can be seen from the above calculation, 0 <τ/T<
0.5, interval a and interval c, and 1>τ/
When T > 0.5, a valid output is always obtained regardless of the phase difference between the D wave and the U wave in sections b and d, so the so-called eye pattern, which is a problem with the normal BPSK modulation method, can be obtained. The problem of the eye disappearing or the horizontal fluctuation becoming large is eliminated.

FIGS. 5A and 5B are diagrams showing an example of the characteristics of the BPSK-RZ modulation method. FIG. 5A shows the change in the bit error rate when the SN ratio is changed, and FIG. 5B shows the change in the bit error rate with respect to the change in the delay time difference between the D wave and the U wave at a constant SN ratio.

The details of each specification are as follows. D
P _D is changed by independent Lehre distribution of wave and U wave,
P _U is the average power of each D wave and U wave, Eb is the signal energy per bit, No is the noise power per unit frequency, and f _D is the maximum frequency of fading drop.

For comparison, the characteristic of normal BPSK is shown by curve BPSK in FIG. 5A. As shown in the figure,
The BPSK-RZ method is considerably improved over the regular BPSK method.

In addition, as shown in Figure 5B, τ/T is 0.1~
The bit error rate becomes extremely good between 0.75 and 0.75. So far, I have explained about BPSK (two-phase modulation).
A similar improvement can be obtained for QPSK (four-phase modulation) by using the QPSK-RZ modulation method in which the amplitude in the latter half of one time slot is set to zero. Figure 6 shows the BPSK-RZ modulation method and QPSK-RZ
This is a comparison of the characteristics of the modulation methods, and the improved characteristics show the same trend.

It has been confirmed that when the ON-OFF signal is band-limited using a baseband filter (bandwidth Bb), the change in characteristics is extremely small as shown in FIG.

It has been confirmed that a similar concept can be extended and applied not only to binary information symbols but also to polyphase modulation that supports multi-level information symbols.

[Problem that the invention seeks to solve]

However, when we calculate the transmission speed at the same level as data transmission using the voice band in ordinary mobile radio (several thousand baud or less), the delay time difference τ is small and τ/T is much smaller than 0.1.
There was a problem in that it was not possible to operate in areas with a good bit error rate, taking advantage of the characteristics of the BPSK-RZ system.

This invention solves the above-mentioned problems and can be used even in low-speed data transmission in ordinary mobile radio.
The object of the present invention is to obtain a digital communication device that can fully utilize the bit error rate improvement characteristics of the BPSK-RZ system, QPSK-RZ system, etc.

[Means for solving problems]

The digital communication device according to the present invention has two systems each of base station transmitting equipment and base station receiving equipment, and one system each has a BPSK-RZ system, a QPSK-RZ system, etc., which is required for optimal operation. A delay circuit is inserted to ensure a delay time difference between the wave and the U wave. This allows the base station transmitter to transmit signals with the required delay separately using horizontally polarized waves and vertically polarized waves, while the base station receiver uses horizontally polarized antennas and vertically polarized antennas. After giving the received signals a required delay time difference, they are combined and detected.

[Effect]

With the above configuration, in mobile station reception, uncorrelated D waves and U waves with a delay time difference that work best in the BPSK-RZ system and QPSK-RZ system are received and demodulated. , the signals emitted from the same mobile transmitter are in the BPSK-RZ format,
The signal is a composite of two signals with a delay time difference that works best in the QPSK-RZ system, and is applied to the demodulator of the base station receiver and demodulated.
As a result, the bit error rate of the BPSK-RZ method,
It is possible to construct a mobile radio digital transmission system that secures the best value in the QPSK-RZ system.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Note that for convenience of explanation, the BPSK-RZ method will be explained, but the method can also be applied to the QPSK-RZ method. In FIG. 1, reference numeral 1 denotes a base station, which is composed of a base station transmitting device 11, a base station receiving device 12, and a base station antenna section 13. Base station transmitter 11
consists of two transmission circuits. That is, the signal from the data input terminal 111 is divided into two systems, and the delay circuit 112 forming the first system
(hereinafter referred to as DL112), a modulator 113 (hereinafter referred to as MOD113) that performs BPSK-RZ modulation,
a power amplifier (hereinafter referred to as PA115), and a second
MOD1 that performs BPSK-RZ modulation that constitutes the system of
14, PA116.

The receiving device of the base station includes a radio frequency amplifier 121 (hereinafter referred to as RFA 121), a mixer 123 (hereinafter referred to as MIX 123), and an IF amplifier 1 that constitute a first system.
25 (hereinafter referred to as IFA125), delay circuit 127
(hereinafter referred to as DL127), RFA122, MIX124, and IFA126 that constitute the second system, and a demodulator 128 (hereinafter referred to as DEM1) that demodulates the output signals of these two systems using a T delay detection circuit after combining the output signals of these two systems.
28), and an output terminal 129.

In addition, the base station antenna section 13 includes a diplexer 1
31 (hereinafter referred to as DUP131), DUP132,
Horizontal polarization antenna 133, vertical polarization antenna 13
Consists of 4.

The mobile station 2 includes a first antenna 21, a second antenna 22 with orthogonal polarization, and a hybrid circuit 2.
3, receiver 24, transmitter 25, reception output terminal 2
6 and a transmission input terminal 27.

Next, the operation will be explained.

In the base station transmitter 11, the data input terminal 111
The signal from is divided into two, one is DL112,
It is transmitted via the MOD 113, PA 115, DUP 131, and horizontally polarized antenna 133. The other one is MOD114, PA116, DUP132 as is.
It is also transmitted via a vertically polarized antenna 134. In the mobile station, the DL 112 in the transmitter 11 receives and detects two signals with a delay time difference.

By the way, when the transmission speed is low, the delay time difference in the spatial propagation path in mobile radio is extremely small compared to the width of the time slot, so the delay time difference required to obtain the best bit error rate in the BPSK-RZ system is DL.
The delay amount of DL 112 is set to be given by 112. Since the mobile station receives and detects the signal sent out from the base station transmitter in this manner, an extremely good bit error rate can be obtained. On the other hand, from the mobile station, the signal from one TX 25 is sent to the first antenna 21 and second antenna 22 whose polarizations are orthogonal.
and received by the base station antenna unit 13. The base station antenna unit 13 is a horizontally polarized antenna 1
33 and vertically polarized antenna 134 receive the signal transmitted from one mobile station transmitter 25, and the signal is converted to an intermediate frequency by two receiving systems corresponding to horizontally polarized and vertically polarized signals. receiving system only
After adding a delay with DL127, synthesize and create DEM12
Leads to 8. As above, DL127 is BPSK-
Since the delay amount is set to the amount necessary to obtain the best bit error rate of the RZ system, data with a very good bit error rate at the base station receiving device can be obtained.

As can be seen from the above explanation, two BPSK-RZ signals transmitted through uncorrelated (or very little correlated) transmission paths, such as horizontally polarized signals and vertically polarized signals in mobile radio, The purpose can be achieved by using DEM128 to detect the signal with the delay time difference between the signals set to the required size (the delay time that allows the code error improvement function in the BPSK-RZ system to be achieved), so the delay circuit As in the previous embodiment, the insertion point is as follows: divide the signal before BPSK-RZ modulation into two, delay one to give the required delay time difference, perform BPSK-RZ modulation on each, and then divide the signal into two. The correlation signal is sent to the transmission path (using horizontal polarization and vertical polarization), and the receiving side combines the signals received through these two paths and performs delay detection (transmission side delay addition method).
The BPSK-RZ signal is sent to two uncorrelated transmission paths, one of the signals received through the first transmission path and the second transmission path is delayed to give the required delay time difference, and then combined and delayed. In addition to the detection method (receiving side delay adding method), another method of transmitting side delay adding method is to divide one BPSK-RZ signal into two, give a delay time difference, and then send it to an uncorrelated transmission path. Another method of receiving delay adding method is to send one BPSK-RZ signal to two uncorrelated transmission paths, give the required delay time difference between each high frequency output of the two uncorrelated transmission paths, and then A method of combining and delay detection may also be used.

Although the above description deals with the case where the delay circuit is inserted only on the base station side, it may be inserted only on the mobile station side or separately on the base station side and the mobile station side.
In addition, although the above explanation was about the case where horizontally polarized signals and vertically polarized signals are used as uncorrelated transmission paths, a method using two sets of antennas whose installation positions are shifted (using the concept of so-called space diversity) A method that uses two antennas with different directivity (using the concept of so-called directional diversity) or a method that uses two sets of antennas that use two or three different combinations of polarization, installation location, and directivity. (polarization, spatial and pointing)
(using a combination of gender diversity).

Furthermore, although the above description is based on the case where both the base station and the mobile station are equipped with antennas for horizontally polarized waves and vertically polarized waves, the plane of polarization is extremely disturbed due to multiple reflections in the propagation path of mobile radio, and The correlation between polarization components and vertical polarization components becomes very weak.
In other words, even if one polarization component decreases, the other polarization component does not decrease, so the antenna of the mobile station may have one type of polarization plane. The transmitted wave from the mobile station becomes a signal with horizontally polarized wave and vertically polarized wave components and is sent to the horizontally polarized antenna 13 of the base station antenna section.
3 and the vertically polarized antenna 134, the signal is converted into a signal with a predetermined delay time by two receiving sections, and then combined, so that the optimum operating characteristics in the BPSK-RZ system can be obtained. Furthermore, the same effect can be obtained even if each signal is radiated as a circularly polarized wave.

Furthermore, although the BPSK-RZ method has been described above, the same effect can be obtained by applying the present invention to other modulation methods as well, if the code error rate can be improved by increasing the delay time difference.

The above explanation applies to both upstream and downstream systems.
Although a case has been described in which a modulation method with an improvement effect such as the BPSK-RZ method is applied, it is also possible to apply the present method to only one system and apply another improvement method to the other system.

〔Effect of the invention〕

As described above, the digital communication device according to the present invention is capable of transmitting signals such as BPSK and RZ signals transmitted via two transmission paths with little or no correlation in transmission characteristics.
Since the delay circuit necessary to secure the delay time difference necessary for the BPSK-RZ method to perform the required code error improvement operation is inserted in series in a part of the path of the two BPSK-RZ signals, etc., Even if the delay time of the spatial propagation path itself is smaller than the delay time difference necessary for the BPSK-RZ method to perform the desired improvement operation, the required delay time difference can be given by selecting the specifications of the delay circuit. It has the effect of being able to operate at the optimal operating point, which is the same as the RZ method.

[Brief explanation of the drawing]

FIG. 1 is a system diagram according to an embodiment of the present invention, and FIG.
The figure is a diagram explaining the BPSK-RZ method, Figure 3 is a diagram explaining two signals with a delay time difference, and Figure 4 is a diagram explaining the BPSK-RZ method.
The system diagram of the BPSK-RZ method demodulation circuit, Figure 5, is
Figure 6 is a characteristic diagram showing the relationship between the bit error rate and the delay time difference in the BPSK-RZ system.
FIG. 7 is a comparison diagram of the characteristics of the RZ method and the QPSK-RZ method, and is a diagram showing the influence on the characteristics of the baseband filter in the BPSK-RZ method. Figure 6 is
A comparison diagram of the characteristics of the BPSK-RZ modulation method and the QPSK-RZ modulation method. FIG. 7 is a comparison diagram of the characteristics when the band is limited by a baseband filter. 1...Base station, 11...Base station transmitter, 111...
Data input terminal, 112...Delay circuit, 113...
BPSK-RZ modulator, 114...BPSK-RZ modulator, 133...Horizontal polarization antenna, 114...Vertical polarization antenna, 12...Base station receiving device, 121...High frequency amplifier, 122...High frequency amplifier, 127...Delay circuit, 128... Demodulator, 129... Data output terminal, 2... Mobile station, 21... Antenna with a first polarization plane, 22... Second antenna with a polarization plane orthogonal to the first polarization plane, 24... Receiver , 25...Transmitter, 26...Data output terminal, 27...Data input terminal.

Claims (1)

[Claims] 1. Two independent signal paths each including two transmission systems with little correlation, and a signal generated from a single signal source sent through these two signal paths. Two BPSK-RZ signals (Binary Phase Shift Keying-Return to zero
BPSK-RZ signal) is synthesized using delayed detection.
The BPSK-RZ method performs a predetermined code error improvement between the signal and the demodulation circuit, and two BPSK-RZ signals that are inserted in cascade into one of the two signal paths and arrive at the demodulation circuit via these two signal paths. A digital communication device comprising: a delay circuit that provides a delay time difference necessary for operation. 2 Divide the signal from one signal source into two, give the required delay to one of the divided signals, and then
2. The digital device according to claim 1, wherein BPSK-RZ modulation is performed and the signal is guided to the demodulation circuit through two signal paths including two paths with little correlation. Communication device. 3 Performs BPSK-RZ modulation on a signal from one signal source, divides the signal into two, applies a predetermined delay to one of the divided signals, and divides each into two signal paths including two paths with little correlation. The digital communication device according to claim 1, characterized in that the signal is led to the demodulation circuit through the. 4 BPSK-RZ modulation is applied to a signal from one signal source, the signal is divided into two, each is guided through two signal paths including two paths with little correlation, and a predetermined signal is applied to one signal. 2. The digital communication device according to claim 1, wherein the digital communication device is configured to apply a delay of .times.1 to 1.0 and then combine the two signals and guide them to a demodulation circuit. 5. The digital communication device according to claim 1, characterized in that propagation paths with mutually orthogonal polarization are used as the two paths with little correlation. 6. The digital communication device according to claim 1, wherein a propagation path passing through two antennas whose antenna positions are shifted is used as the two paths with little correlation. 7. The digital communication device according to claim 1, wherein a propagation path passing through two antennas having different antenna directivity is used as the two paths with little correlation. 8 Two paths with little correlation include a propagation path using mutually orthogonal polarizations, a propagation path that goes through two antennas whose antenna positions are shifted, and a propagation path that goes through two antennas with different antenna directivity. The digital communication device according to claim 1, characterized in that a propagation path configured by combining one or three is used. 9 In devices that mutually exchange digital signals between a base station and a mobile station, the BPSK-RZ modulator installed in the route from the base station to the mobile station and the route from the mobile station to the base station, and each route two independent signal paths including each of two low correlation paths formed for each route, and each route inserted in cascade into one of the two signal paths;
a delay circuit in which the delay time difference between the BPSK-RZ signals of the two signal paths of each route is set to a required value required for code error improvement operation of the BPSK-RZ method;
The signals arriving via the two signal paths in each route are combined and processed into BPSK-RZ by delayed detection.
A digital communication device comprising a demodulation circuit that demodulates a signal. 10 The base station sends one of the divided input signals to BPSK-RZ through a delay circuit having the required delay time.
A first transmission system that performs modulation, high frequency amplification, and then sends it out with a first antenna, and a second transmission system that performs BPSK-RZ modulation on the other half of the input signal, and then sends it out with a second antenna, after high frequency amplification. The signal received by the first receiving antenna is converted to an intermediate frequency, the required delay is given, and the signal received by the second receiving antenna is combined with the converted intermediate frequency. By delay detection
The mobile station consists of a demodulation circuit that demodulates the BPSK-RZ signal, and the mobile station consists of a single transmitter that modulates the BPSK-RZ signal and a single demodulation circuit that demodulates the BPSK-RZ signal using a delay detector. The digital communication device according to item 9 of the patent scope. 11. The digital communication device according to claim 10, wherein the two antennas constituting the transmission system and the two antennas constituting the reception system are composed of two polarized antennas orthogonal to each other. 12. Claim 10, characterized in that the two antennas constituting the transmission system and the two antennas constituting the reception system are antennas having a space diversity effect whose installation positions are different from each other. digital communication equipment. 13. The digital communication device according to claim 10, wherein the antenna constituting the transmitting system and the antenna constituting the receiving system are constructed of antennas having different directivity and having a directional diversity effect. 14 The antennas that make up the transmission system and the antennas that make up the reception system are two or three antennas: antennas with mutually orthogonal polarization planes, antennas with mutually shifted antenna positions, and antennas with mutually different directivity. 11. The digital communication device according to claim 10, wherein the digital communication device is an antenna having a diversity effect configured by a combination of two different types. 15. Claims 10, 11, 12, and 13, characterized in that the antenna of the first signal path in the transmission system and the antenna of the first signal path in the reception system are shared. Or the digital communication device according to item 14. 16 Two independent signal paths each including two transmission systems with little correlation,
Two QPSK-RZ signals (Quadruple phase shift keying-Return to
QPSK-
A predetermined QPSK-RZ system is used between a demodulation circuit that demodulates the RZ signal and two QPSK-RZ signals that are cascaded into one of the two signal paths and arrive at the demodulation circuit via these two signal paths. A digital communication device comprising: a delay circuit that provides a delay time difference necessary for code error correction operation. 17 Divide the signal from one signal source into two, give the required delay to one of the divided signals, and then
The digital device according to claim 16, wherein QPSK-RZ modulation is performed and the signal is guided to the demodulation circuit through two signal paths including two paths with little correlation. Communication device. 18 Perform QPSK-RZ modulation on a signal from one signal source, divide the signal into two, apply a predetermined delay to one of the divided signals, and divide each signal into two signal paths each containing two paths with little correlation. 17. The digital communication device according to claim 16, wherein the digital communication device is configured to lead the signal to the demodulation circuit through the digital communication device. 19 QPSK-RZ modulation is applied to a signal from one signal source, the signal is divided into two, each is guided through two signal paths including two paths with little correlation, and one signal is given a predetermined signal. 17. The digital communication device according to claim 16, wherein after a delay is applied, both are combined and guided to a demodulation circuit. 20. The digital communication device according to claim 16, characterized in that propagation paths with mutually orthogonal polarization are used as the two paths with little correlation. 21. The digital communication device according to claim 16, wherein a propagation path passing through two antennas whose antenna positions are shifted is used as the two paths with little correlation. 22. The digital communication device according to claim 16, wherein a path passing through two antennas having different antenna directivity is used as the two propagation paths with little correlation. 23 Two paths with little correlation include a propagation path using mutually orthogonal polarizations, a propagation path that goes through two antennas whose antenna positions are shifted, and a propagation path that goes through two antennas with different antenna directivity. 17. The digital communication device according to claim 16, wherein a propagation path configured by combining one or three is used. 24 In devices that mutually exchange digital signals between base stations and mobile stations, QPSK-RZ modulators installed in the route from the base station to the mobile station and from the mobile station to the base station, and each route QPSK of the two signal paths of each route is inserted in cascade into one of the two signal paths of each route, and the QPSK of the two signal paths of each route is
The delay time difference of the RZ signal is set to the required value for the QPSK-RZ system code error correction operation, and the signals arriving through the two signal paths in each route are combined and delayed detection is used to perform the QPSK-
A digital communication device comprising a demodulation circuit that demodulates an RZ signal. 25 The base station sends one of the divided input signals to QPSK-RZ through a delay circuit having the required delay time.
A first transmission system that performs modulation, high frequency amplification, and then sends it out with a first antenna; and a second transmission system that performs QPSK-RZ modulation on the other half of the input signal, and sends it out using a second antenna, after high frequency amplification. The signal received by the first receiving antenna is converted to an intermediate frequency, the required delay is given, and the signal received by the second receiving antenna is combined with the converted intermediate frequency. By delay detection
The mobile station consists of a demodulation circuit that demodulates the QPSK-RZ signal, and the mobile station consists of a single transmitter that modulates the QPSK-RZ signal and a single demodulation circuit that demodulates the QPSK-RZ signal using a delay detector. 25. A digital communication device according to claim 24. 26. The digital communication device according to claim 25, wherein the two antennas constituting the transmission system and the two antennas constituting the reception system are composed of two polarized antennas orthogonal to each other. 27. The digital communication device according to claim 25, wherein the two antennas constituting the transmission system are antennas having space diversity effects whose installation positions are different from each other. 28. The digital communication device according to claim 25, wherein the antenna constituting the transmitting system and the antenna constituting the receiving system are constructed of antennas having different directivity and having a directional diversity effect. 29 The antennas constituting the transmission system, the antennas constituting the reception system, and the antennas constituting the reception system are antennas with polarization planes orthogonal to each other,
Claim 25, characterized in that the antenna has a diversity effect and is configured by two or three different combinations of antennas whose antenna positions are shifted from each other and antennas whose directivity is different from each other. Digital communication equipment. 30. Claims 25, 26, 27, and 28, characterized in that the antenna of the first signal path in the transmission system and the antenna of the first signal path in the reception system are shared. Or the digital communication device according to item 29.