JP3097623B2 - Diversity transmission / reception system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity transmission / reception system, and more particularly to a diversity transmission / reception system for automatically correcting a signal delay time difference due to a feeder length difference connecting two antennas and a transmission / reception device.

[0002]

2. Description of the Related Art As a measure against multipath fading, 2
A diversity system is used in which two antennas are set apart from each other by a distance that has no correlation. In this method, if the distance between the two antennas and the transmission / reception device is equal, the length of the feeder connecting them can be equal, so that there is no difference in signal delay time. However, in the case of a fixed microwave line such as non-line-of-sight communication using two antennas, the feeder lengths cannot often be equalized due to restrictions such as terrain and installation location.

In general, an adaptive matched filter is used in a diversity type receiving apparatus, and a delay difference of a signal due to multipath fading is removed by the adaptive matched filter. However, the delay difference caused by the feeder length difference often exceeds the operation range of the adaptive matching filter. Therefore, conventionally, a countermeasure is made by adding an extra feeder corresponding to the feeder length difference to the short feeder side.

[0004]

As described above, conventionally, when the distance between two antennas and the transmitting / receiving device cannot be equalized, an extra feeder corresponding to the difference in feeder length is added to the short feeder side. , The delay time difference between the signals is corrected. However, since the length of the feeder to be corrected differs for each installation location, it is necessary to conduct on-site surveys and adjustments individually for each installation location of the station, which not only requires material and construction costs for the feeder, but also Also, it is necessary to consider the storage space for the feeder, etc., and there is a problem that it takes time to investigate and adjust.

An object of the present invention is to provide a diversity transmission / reception system capable of automatically correcting a delay time difference without using a correction feeder when the distance between two antennas and a transmission / reception device cannot be equalized. It is in.

[0006]

SUMMARY OF THE INVENTION A diversity transmitting / receiving system according to the present invention is a diversity transmitting / receiving system for transmitting / receiving data between two opposing stations using two antennas. The modulated output signal of the intermediate frequency band is converted into transmission signals of two different frequencies in the microwave band and transmitted from the two antennas to the partner station, and the receiving devices of both stations transmit the two signals transmitted from the partner station. A transmission signal of a different frequency is received by one of the two antennas, frequency-separated, converted into two reception signals in an intermediate frequency band, and then combined and demodulated. Two delay correcting means for respectively providing a designated delay to the modulated output signal of the band, and the receiving apparatus further comprises:
Delay detecting means for detecting a delay difference between the two received signals based on a tap coefficient of the adaptive matched filter. Then, the delay difference detected by the delay detecting means of the local station receiving apparatus is reported to the partner station, and the delay amount of the delay correcting means of the local station transmitting apparatus is controlled according to the delay difference reported from the partner station. Accordingly, a correction control means for correcting and controlling a delay difference due to a feeder length difference connecting the two antennas and the transmission device is provided.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Opposing stations A and B have the same configuration. Stations A and B include transmitting devices 1a, 1b, receiving devices 2a,
2b, correction controllers 3a and 3b, and two antennas 4a-1 and 4a-2 and 4b-1 and 4b-2 are provided respectively.

Here, the transmitting apparatus 1a of the A station splits the modulated output signal of the intermediate frequency band phase-modulated by the transmission data signal D1a into two, performs delay correction on each of them, and then applies microwaves of frequencies f1 and f2. Band transmission signals S1, S2
The transmission signal S1 is transmitted from the antenna 4a-1 to the B station, and the transmission signal S2 is transmitted from the antenna 4a-2 to the B station. On the other hand, the receiving device 2b of the station B has the antenna 4b-
1, the transmission signals S1 and S2 of the partner station (station A) are frequency-separated, converted into intermediate frequency band signals, respectively, and subjected to S / N maximum ratio combining by an adaptive matching filter, and then the two signals are combined. And outputs a demodulated output signal D2b.

Similarly, the transmitting device 1b of the B station splits the modulated output signal of the intermediate frequency band, which has been phase-modulated by the transmission data signal D1b, into two branches, performs delay correction on each of them, and then performs microwave correction at frequencies f3 and f4. Band transmission signals S3, S4
The transmission signal S3 is transmitted from the antenna 4b-1 to the station A, and the transmission signal S4 is transmitted from the antenna 4b-2 to the station A. On the other hand, the receiving device 2a of the station A has the antenna 4a-
1, the transmission signals S3 and S4 of the partner station (station B) received are frequency-separated, converted into intermediate frequency band signals, respectively, and S / N maximum ratio-combined by an adaptive matching filter, and then the two signals are combined. And demodulates to output a demodulated output signal D2a.

The transmitting device 1 (1a, 1b) generates a modulating section 11 (11a, 1b) for generating a modulation output signal in an intermediate frequency band phase-modulated by the transmission data signal D1 (D1a, D1b).
1b) and a delay correction unit 12 (12a-1, 12a-) that performs delay correction on the modulated output signal branched into two, respectively.
2 and 12b-1, 12b-2) and the delay correction unit 12
Are transmitted to the transmission signals (S1, S2) of the microwave band frequencies (f1, f2 and f3, f4).
2 and S3, S4), transmission frequency converters 13 (13a-1, 13a-2, and 13b) for frequency conversion, respectively.
-1, 13b-2) and circulators 14a and 14b for separating transmission and reception.

FIG. 2 shows a delay correction unit 12 (12a-1, 12a-1).
a-2, 12b-1, 12b-2) is a block diagram showing an example in which three delay routes are provided. Switch 121 for selecting delay route
And a delay element 122 for giving a delay time τ to a passing signal
And a delay element 12 for giving a delay time 2τ to the passing signal
And 3.

The switch 121 is controlled by the correction control section 3 to select one of the three delay routes, and to provide a delay of 0, τ, or 2τ to the selected signal. In the initial stage, an intermediate delay route (delay time τ) is selected.

The delay correction unit 12 is provided to correct a signal delay time difference due to a difference in feeder length between the two antennas and the transmission device. The delay time τ is １ ／ of the modulation symbol period T of transmission data. And the number of delay routes is
Is equal to the number of taps of the adaptive matching filter 23 of the receiving device,
Set more than that. If the number of delay routes is M (M is an integer of 3 or more), the delay time of each delay route is 0,
τ, 2τ,. . . , (M−1) τ.

The receiving device 2 (2a, 2b) separates the frequency of two signals (S1, S2 and S3, S4) transmitted from the other station with different frequencies.
1a, 21b) and a reception frequency conversion unit 22 (22a) that frequency-converts the reception signals of microwave frequencies f1, f2 and f3, f4 into reception signals of an intermediate frequency band, respectively.
-1, 22a-2 and 22b-1, 22b-2);
An adaptive matching filter 23 (23a-23) that performs S / N maximum ratio synthesis on a signal whose frequency has been converted to an intermediate frequency band.
1, 23a-2 and 23b-1, 23b-2) and a tap detector 24 (2
4a-1, 24a-2 and 24b-1, 24b-2)
And a combining unit 25 (25a, 25b) for combining the output signals of the two adaptive matched filters, and a demodulating unit 26 (26a) for demodulating the output signal of the combining unit 25 and outputting a demodulated output signal D2 (D2a, D2b). , 26b).

FIG. 3 is a block diagram showing an example of the adaptive matching filter 23, and shows a case where the number of taps is three.

The adaptive matching filter 23 includes delay elements 231 and 232 connected between taps to provide a delay time τ,
Correlation operation circuits 233-1, 233-2, 233-3 for calculating the correlation between the signal at each tap (R1, R2, R3) and the demodulated output signal D2 and outputting the result as a tap coefficient; Circuits 234-1, 234-2, and 234-3 for multiplying the weights by tap coefficients, a synthesizing circuit 235 for synthesizing the outputs of the multiplying circuits, and a correlation operation circuit 2
It has detection elements 236-1, 236-2, and 236-3 for detecting the output of 33 and outputting a detection voltage according to the tap coefficient. Note that the delay time τ of the delay elements 231 and 232 is set to の of the modulation symbol period T.

Incidentally, the adaptive matched filter has a function of converging a signal dispersed on a time axis and a function of controlling timing. The former is a function of converging a signal dispersed by a delay or the like to enhance a signal level. It estimates the tap coefficient by calculating the correlation between the signal on each tap given a fixed delay by the delay element between taps and the demodulated output signal, and multiplies the tap coefficient with the signal on each tap. By combining the signals after weighting, the signals dispersed on the time axis are converged.

The latter has a function of adjusting a received signal that has fluctuated on the transmission line to the clock timing of the receiving side. The signal transmitted from the transmitting side at a fixed modulation symbol period is
Although the signals propagate through independent diversity transmission paths, the transmission path characteristics fluctuate with time, and the reception timings of the diversity transmission paths do not match. However, in the adaptive matching filter, the correlation calculation processing, the multiplication processing, and the like are performed based on the clock timing on the receiving side, so that the received signal that has fluctuated on the transmission path can be combined in accordance with the timing on the receiving side.

When the number of taps is N (N is an odd number of 3 or more), the operation range in which the adaptive matched filter can converge is as follows.
(N−1) × τ = (N−1) × (T / 2). For example, in the case of an adaptive matching filter having seven taps, convergence can be achieved if the delay difference between the most advanced signal and the least delayed signal is within 3T. However, for stable operation, the delay difference is ideally within T.

Now, referring to FIG.
The signal on each of the taps R1, R2, R3 of the delay element 2
31 and 232 give a delay difference τ = T / 2. Then, based on the signal of the center tap R2, the leading signal is stored toward the far tap R3, and the late signal is stored toward the near tap R1. In addition,
Since the delay time difference between the taps is T / 2, there is no signal whose delay difference between the most advanced signal and the latest signal exceeds T. Therefore, it does not function for a signal whose delay difference exceeds T.

Correlation operation circuits 233-1, 233-2, 2
33-3 performs a correlation operation between the signals on the taps R1, R2, and R3 and the demodulated output signal D2 demodulated by the demodulation unit 26, respectively, and uses the result as a tap coefficient as multiplication circuits 234-1 and 234-2. , 234-3. A large value of the tap coefficient indicates that the correlation with the demodulated output signal D2 is high.

Multiplication circuits 234-1, 234-2, 234
-3 indicates that the signal on the tap is a tap coefficient (correlation operation circuit 23)
3 output) and weighted. The combining circuit 235 combines the outputs of the respective multiplier circuits 234. The detection element 2
36-1, 236-2 and 236-3 are the correlation operation circuit 2
An output of the tap 33 is detected to generate a detection voltage corresponding to the tap coefficient, and is output to the tap detection unit 24.

The tap detector 24 (24a-1, 24a-
2 and 24b-1, 24b-2) are adaptive matched filters 23 (23a-1, 23a-2 and 23b-1, 2).
3b-2) receives and compares the detection voltages corresponding to the tap coefficients, detects the tap having the largest tap coefficient, and sends the tap information C1 (C1a-C) to the correction control unit 3 (3a, 3b).
1, C1a-2 and C1b-1, C1b-2).

The correction control section 3 (3a, 3b) sends delay correction information C2a, C2b to the other station based on the tap information C1 from the tap detecting section 24 of the receiving apparatus of the own station, and also outputs the delay from the other station. It controls the delay correction unit 12 of its own transmitting device according to the correction information C2b and C2a.

The modulation section 11 of the transmission apparatus is configured to superimpose the delay correction information C3 from the correction control section 3 on the transmission data signal D1 and modulate it. On the other hand, the demodulation unit 26 of the receiving device is configured to demodulate the demodulated output signal D2 and the delay correction information C2 from the partner station, respectively. In addition, as means for transmitting the delay correction information C3 to the partner station, other than the superimposition on the transmission data signal, the delay correction information C3 may be transmitted using another communication line.

Next, the operation will be described.

In FIG. 3, the transmission path of the transmission signal S1 of the frequency f1 transmitted from the transmitting apparatus 1a of the station A extends from the output end of the transmission frequency converter 13a-1 to the antenna 4a-1.
Then, the signal is input to the receiving apparatus 2b via the antenna 4b-1 of the station B, converted to an intermediate frequency by the reception frequency conversion unit 22b-1, and input to the adaptive matching filter 23b-1.

The transmission path of the transmission signal S2 of the frequency f2 is input from the output end of the transmission frequency converter 13a-2 to the receiving device 2b via the antenna 4a-2 and the antenna 4b-1 of the B station. The converted frequency is converted into an intermediate frequency by the conversion unit 22b-2 and input to the adaptive matching filter 23b-2.

Now, for example, the adaptive matched filter 23b-1
, The tap coefficient of the center tap R2 is the largest,
Tap R1 in the front in adaptive matching filter 23b-2
Is the maximum, the signal system of the frequency f2 input to the adaptive matching filter 23b-2 is delayed by T / 2 from the signal system of the frequency f1 input to the adaptive matching filter 23b-1. Will be.

The delay difference is a relative difference between the propagation delay time of the transmission path of the transmission signal S1 and the propagation delay time of the transmission path of the transmission signal S2. The difference between the distance from the end to the antenna 4a-1 and the distance from the output end of the transmission frequency converter 13a-2 to the antenna 4a-2 can be detected. That is, the distance from the output end of the transmission frequency conversion unit 13a-2 to the antenna 4a-2 is greater than that of the transmission frequency conversion unit 13a-2.
-1 is longer than the distance from the output terminal to the antenna 4a-1 by an amount corresponding to the delay time T / 2.

As described above, the adaptive matched filter 23b-
The relative delay of the propagation delay time between the transmission path of the transmission signal S1 and the transmission path of the transmission signal S2 can be determined by the tap position states of the maximum tap coefficients of 1, 23b-2. In this case, the delay due to the difference in feeder length includes the propagation path from the A station antenna 4a-1 to the B station antenna 4b-1 and the propagation path from the A station antenna 4a-2 to the B station antenna 4b-1.

By the way, considering the variation of the propagation characteristics between the stations A and B, the adaptive matching filter 23 is provided with the center tap R2.
It is preferable that the tap coefficient is maximized. In the above-described adaptive matched filter 23b-2, in order to set the center tap to the maximum tap coefficient, the adaptive matched filter 23b-2
The signal input to b-2 may be advanced by T / 2. That is, the delay correction unit 12 initially sets the delay time τ (= T
/ 2), the delay time in the delay correction unit 12a-2 of the transmitting device 1a of the station A is switched from the delay time τ to the delay time 0. In this case, the delay correction information C is transmitted from the correction control unit 3b of the station B to the correction control unit 3a of the station A.
2b, and the correction control unit 3a of the station A switches the delay time of the delay correction unit 12a according to the delay correction information C2b from the station B.

Further, for example, the adaptive matched filter 23b-
At 1, the tap coefficient of the rear tap R3 is the maximum,
Tap R1 in the front in adaptive matching filter 23b-2
Is the maximum, the signal system of the frequency f1 input to the adaptive matching filter 23b-1 is T / 2 earlier than the reference, and the signal system of the frequency f2 input to the adaptive matching filter 23b-2 is the reference. That is, it is delayed by T / 2. That is, the distance from the output end of the transmission frequency conversion unit 13a-2 to the antenna 4a-2 is equivalent to the delay time T than the distance from the output end of the transmission frequency conversion unit 13a-1 to the antenna 4a-1. Will only be long.

In this case, the correction control unit 3b of the station B includes the adaptive matching filter 23b-1 and the adaptive matching filter 23b.
-2, so that the center tap R2 becomes the maximum tap coefficient.
The delay correction information C2b is sent to the correction control unit 3a of the station A,
The switch of the delay correction unit 12a-1 of the station A is switched from the delay time τ to the delay time 2τ, and the delay correction unit 12a-1
2 is switched from the delay time τ to the delay time 0.

In this manner, the delay time difference between the two antennas on the A station side and the transmitting / receiving device can be automatically corrected without using a correction feeder.

Similarly, for the transmission signal S3 of the frequency f3 and the transmission signal S4 of the frequency f4 transmitted from the transmitting device 1b of the station B, the maximum of the adaptive matching filters 23a-1 and 23a-2 of the receiving device 2a of the station A is obtained. It is possible to make a relative comparison between the propagation delay times of the transmission path of the transmission signal S3 and the transmission path of the transmission signal S4 by using the tap position state of the tap coefficient, and to correct the delay time difference between the two antennas at the B station and the transmission / reception device. Can be automatically corrected without using a feeder.

[0038]

As described above, according to the present invention, 2
A modulated output signal provided with a delay for correcting a delay difference due to a feeder length difference connecting one antenna and a transmission device is converted into a signal of a different transmission frequency and transmitted from each of the two antennas. One of the antennas receives and converts it to two received signals in the intermediate frequency band,
These two received signals are input to the adaptive matching filter to detect a delay difference based on the tap coefficient, report the detected delay difference to the partner station, and, in accordance with the delay difference reported from the partner station, to the local station. By controlling the delay amount of the modulation output signal of the transmitting device, the delay time difference can be automatically corrected without using a correction feeder as in the past, so that the local It is not necessary to carry out surveys and adjustments at the same time, and not only can material costs and construction costs of the feeder be reduced, but also it is not necessary to consider the storage space for the correction feeder.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an example of a delay correction unit 12 shown in FIG.

FIG. 3 is a block diagram showing an example of an adaptive matched filter 23 shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting apparatus 2 Receiving apparatus 3 Correction control part 4 Antenna 12 Delay correction part 23 Adaptive matching filter 24 Tap detection part C1 Tap information C2 Delay correction information D1 Transmission data signal D2 Demodulation output signal S1, S2, S3, S4 Transmission signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-150113 (JP, A) JP-A-5-300059 (JP, A) JP-A-60-125027 (JP, A) JP-A-63-1988 263834 (JP, A) JP-A-6-303172 (JP, A) JP-A-10-256969 (JP, A) JP-A-1-174040 (JP, A) JP-A-3-201629 (JP, A) HEIQ 3/00-3/46 H01Q 21/00-25/04 H04B 7/00 H04B 7 / Field surveyed (Int. Cl. ⁷ , DB name) 02-7/12 H04B 7/24-7/26 113 H04L 1/02-1/06 H04Q 7/00-7/04

Claims (5)

(57) [Claims] 1. A diversity transmitting / receiving system for transmitting and receiving between two opposing stations using two antennas, wherein the two opposing stations transmit a modulated output signal of a bifurcated intermediate frequency band in a microwave band. A transmitting device that converts the signals into transmission signals of two different frequencies and transmits the signals from the two antennas to the partner station, respectively,
A receiving device that receives a transmission signal of two different frequencies from one of the two antennas, separates the signals into two reception signals in an intermediate frequency band, and then combines and demodulates the two reception signals; And a correction control means for correcting and controlling a delay difference caused by a feeder length difference connected to the apparatus, wherein the transmission apparatus provides two delays that respectively provide a designated delay to the two-branched intermediate frequency band modulated output signal. Correction means, and the reception device has delay detection means for detecting a delay difference between the two reception signals converted into an intermediate frequency band, and the correction control means has the delay of the local station reception device. The delay difference detected by the detecting means is reported to the correction control means of the partner station, and the delay compensation of the own station transmitting device is reported according to the delay difference reported from the correction control means of the partner station. A diversity transmission / reception system, wherein a delay amount of the correct means is controlled. 2. The receiving device according to claim 2, wherein
The two received signals are each given a fixed delay by a delay element between taps, multiply the signal on each tap by a tap coefficient, and then combine the signals, and output a detection voltage corresponding to the tap coefficient of each tap. 2. The diversity transmission / reception system according to claim 1, further comprising an adaptive matching filter, detecting the delay difference by detecting a tap having a maximum tap coefficient by comparing the detection voltages from the two adaptive matching filters. . 3. The delay correction means of the transmission device includes: a plurality of delay routes including delay elements having different delay times;
3. The diversity transmission / reception system according to claim 2, further comprising a switch controlled by the correction control means of the own station to select one of the plurality of delay routes. 4. The number N of taps of the adaptive matching filter of the delay detecting means is an odd number of 3 or more, and the delay time τ of each delay element between taps is の of the modulation symbol period T. The number of delay routes M selected by the delay correction means
Is M ≧ N, and the delay time of each delay route is 0,
τ, 2τ,. . . , (M-1) τ. 4. The diversity transmitting / receiving system according to claim 3, wherein 5. The diversity control device according to claim 4, wherein said correction control means controls said delay correction means such that a tap of a maximum tap coefficient in said adaptive matching filter of said delay detection means becomes a center tap. Transmission / reception system.