JPS5992633A - Diversity reception and synthesizing system - Google Patents

Abstract

PURPOSE:To hold an S/N ratio invariably high by adding auxiliary demodulators corresponding to plural propagation paths and disconnecting the signal to a propagation path which causes deterioration of S/N. CONSTITUTION:The auxiliary demodulators 106 and 206 are provided corresponding to the propagation paths and a signal with the most suitable S/N is selected and applied to an S/N comparator 18. The signal passed through a synthesizer 12, on the other hand, is applied to a demodulator 13, whose output is applied to the S/N comparator 18 similarly, to make the S/N of the signal obtained after the S/N of the propagation path where the signal with the excellent S/N comparison with the S/N of the signal obtained by synthesizing. Then, when the S/N value after the composition is less than the S/N of the propagation path where the signal of good quality is obtained, the signal of a propagation path with a lower carrier level is attenuated greatly and the synthesizer 12 disconnects the propagation path.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a diversity-received FDM-F
The present invention relates to a diversity receiving and combining method for multiple telephone signals using the M method.

In general, in communication systems where propagation path characteristics are unstable, such as non-line-of-sight communication systems, the diversity reception system is widely adopted.
Efforts are being made to improve transmission signal quality.

When combining the diversity received signals, the ratio square (
ratio 5 square) is adopted as the most superior method. This weights the signals received through each propagation path before combining them in accordance with the quality of the signals on the propagation path, and emphasizes the signals received through the outer propagation paths with good signal quality. This method performs synthesis after that. This synthesis method includes the stage before the return station (
The pre-detection synthesis method performs synthesis in the pre-det-ection stage, and the post-detection synthesis method performs synthesis in the post-demodulation stage.
There are two types, the post-detection synthesis method, which performs synthesis at 100% on), and each has its own characteristics. , a pre-detection synthesis method configured to improve the C/N ratio (ratio of carrier signal level to noise) before demodulation is superior to a post-detection synthesis method. It is thought that there is.

However, during weighting before combination, the quality of the received signal is determined only by the carrier level before demodulation, so for example, if the signal is subjected to large distortion in the transmission band due to multiple propagation paths, However, if the overall level of the carrier wave is high, the signal quality is determined to be good, and the signal received through this propagation path is output with more emphasis than other signals with a lower carrier wave level. There are drawbacks. Similarly, there is strong interference from the remote line, etc., and the D/U ratio (ratio of signal levels of desired waves to unwanted waves) is reversed, causing the carrier signal of this propagation path to be higher than the carrier signal of the remote propagation path. When the carrier wave level is high, the signal received through this propagation path is outputted as a result of being emphasized. An example of a receiving device for this purpose is shown in FIG. Referring to FIG. 1, the receiving device Fi first and second receiving antennas 1
01.102 and the first and second receiving frequency converters 1
02, 202 and the first and second variable gain amplifiers 10
3,203.

1st and r! A2 (7) AGC amplification 6104, 204
and.

First and second weighting circuits 105° 205, AGC voltage switcher 11 and 2 combiner 12, and demodulator 13
It is made up of. first and second receiving antennas 101 arranged corresponding to the diversity receiving propagation path;
The signals received from the 2DIK are converted into intermediate frequency signals by the first and second reception frequency converters 102 and 202, respectively, and the signals are converted into intermediate frequency signals by the first and second variable gain amplifiers 103.
After being amplified by ゜203, the first and second
The weighting circuits 105 and 205 weight the inputs of each propagation path according to the value of the C/N ratio. The first and second variable gain amplifiers 103, 203 are used in combination with first and second AGC amplifiers 104, 204, respectively. In order to perform ratio square combination control, a first propagation path leading to the first receiving antenna 101;

The first and second AGC amplifiers 104 and 2 are connected to the second propagation path leading to the second receiving antenna 201, respectively.
04 the first and second variable gain amplifiers 103.2
Common gain control is performed so that the gains of 03 are the same.

For the first propagation path and the second propagation path, the first
and 217th) AGC amplifier 104, . 21), A G C to be added to 4! , voltage is once supplied to the AGC voltage switch 11, and the higher of the reception input levels of these propagation paths, AGCI! A common gain is obtained by selecting the voltage and applying it to the first and second variable gain amplifiers 103 and 203.

The first and second variable gain amplifiers 103 and 203 amplify the signal on the propagation path with the higher reception input level to the reference level, and the signal on the other propagation path is made higher than the reference level by the level difference between both propagation paths. Output with a low setting. moreover,
This output signal is applied to a weighting circuit, and the weighting circuit weights it so that the difference in output level between both propagation paths is twice the difference in input level. As described above, we were able to perform control so as to satisfy the ratio square synthesis method, but after that, the signals of both propagation paths were added to the synthesizer 12 and synthesized, and the modulator 13 performed FM detection and output the signal to the output terminal. Output from 14. The above common gain control and weighting are performed in response to the received input carrier level, so for example,
Although the level of the carrier wave signal in the first propagation path is high, the demodulated signal contains distortion and interference noise due to selective fading and interference, and the S/N ratio value is low.
If the level of the carrier signal in the first propagation path is low but is not affected by distortion or interference and the S/N ratio of the demodulated signal is good, control is applied to the first propagation path. . That is, in this case, the signal on the first propagation path is emphasized, and the signal on the second propagation path is emphasized.
As a result of weakening and combining the signals of the first propagation path, the signal of the first propagation path with a low S/N ratio is output and the S/N of the combined signal is reduced.
The N ratio deteriorates significantly.

The purpose of the present invention is to add an auxiliary demodulator that supports multiple propagation paths in addition to the conventional pre-detection synthesis method, thereby once FM detecting the signal of each propagation path, and outputting the maximum S/N.
In addition to the detector, select a signal from a propagation path that has a good S/N ratio, and when the S/N ratio of the composite signal from multiple propagation paths is lower than the S/N ratio of the signal from a single propagation path. According to the present invention, the disadvantages of the conventional method are removed by separating the signals on the propagation path with a low S/N ratio using a combining/separating controller, thereby providing a diversity receiving/combining system with a good S/N ratio.

The diversity reception combining method according to the present invention uses a plurality of reception antennas and a plurality of reception frequency converters.

A plurality of variable gain amplifiers and a plurality of AGC amplifiers.

Multiple waiting circuits and AGC'[! This is an improved version of the diversity receiving and combining system, which is realized by including a pressure switch, a 1-synthesizer, and a demodulator.

That is, in addition to the above, the present invention also includes a plurality of auxiliary demodulators,
AGC voltage comparator and maximum S/N detector.

This is a method realized by including an S/N comparator and a two-synthesis/separation controller.

In the present invention, the plurality of receiving antennas are for respectively receiving modulated waves arriving via a plurality of propagation paths. The plurality of receiving frequency converters are for converting modulated waves respectively sent out from the plurality of receiving antennas into intermediate frequency signals.

The plurality of variable gain amplifiers are for amplifying intermediate frequency signals, respectively. The plurality of AGC amplifiers are for respectively controlling multiple p variable gain amplifiers. The plurality of weighting circuits individually receive the respective outputs of the plurality of variable gain amplifiers and perform ratio square synthesis control. The AGC voltage cutter is used to perform common gain control among a plurality of propagation paths. The combiner is for combining the outputs of multiple weighting circuits. The demodulator is used to modulate the output of the combiner.

Furthermore, the plurality of auxiliary demodulators are for receiving and modulating the respective outputs of the plurality of variable gain amplifiers. AG
The C+ voltage comparator is for comparing AGC voltages between multiple AGC amplifiers.

The maximum S/N detector is for once comparing the respective outputs of a plurality of auxiliary demodulators, and then selecting the output having the maximum S/N ratio. The S/N comparator is for comparing the S/N ratio of the signal of the selected best propagation path with the S/N ratio of the signal bubbled out by the demodulator after nine combinations. If the S/N ratio of the signal after combining is worse than the S/N ratio of the signal on the best propagation path, the combination/separation controller
Alternatively, if the output of the auxiliary demodulator is above a predetermined threshold, but the level of the radio pilot signal included in the modulated wave is below the predetermined threshold, the S/N ratio is degraded. This is to separate the signal in the propagation path from the demodulation system.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of a configuration for realizing a diversity reception system according to the present invention.

In FIG. 2, the receiving device includes first and second receiving antennas 101, 201, first and second receiving frequency converters 102, 202, first and second variable gain amplifiers 103, 203, tlXl and second AGC amplifiers 104, 204, first and second weighting circuits 105, 205, and first and second auxiliary demodulators 1
06,206, AGC Yoi, pressure switch 11 and 2 combiner 1
2, the demodulator 13, the AGC voltage comparator 15, and the maximum S
The device is equipped with a /N detector 16, a two-composition/separation controller 17, and an S/N comparator 18. In Figure 2,
Blocks having the same reference numerals as in FIG. 1 have the same functions as in FIG. That is, under normal conditions, the first and second
The signals received by the receiving antenna 101° 201 are converted into intermediate frequency signals via the first and second receiving frequency converters 102 and 202, respectively, and the signals are converted into intermediate frequency signals via the first and second variable gain amplifiers 103 and 203. is amplified via. These signals are subjected to weighting control by first and second weighting circuits 105 and 205, then combined by a combiner 12, subjected to FM detection by a demodulator 13, and outputted from an output terminal 14. Here, first and second auxiliary demodulators 106 and 206 are provided for each propagation path, and the signal on each propagation path is once subjected to FM detection by these auxiliary demodulators. The value of the S/N ratio of the demodulated signal and the level of the radio pilot signal included in the modulated signal are constantly monitored. That is, a signal representing the value of the 8/N ratio is applied to the maximum S/N detector 16, and among these first and second propagation path signals,
The signal with the best S/N ratio is selected and applied to S/N comparator 18. On the other hand, the signal passing through the synthesizer 12 is applied to the demodulator 13, and the signals of each propagation path are similarly outputted from the output of the demodulator 13 and applied to the S/N comparator 18. Therefore, the value of the S/N ratio of the propagation path that gives a signal with a good S/N, and the S/N of the signal obtained after combining the two.
The ratio value is compared. Under normal conditions, the S/
Is the value of the N ratio equal to the value of the S/N ratio of the signal in the propagation path that provides a good S/N ratio at the input, or is it this value? 4. Since a good S/N ratio value is obtained, a combining operation is performed by the combiner 12. However, after synthesis S/
S/N of a propagation path where a signal of good quality can be obtained with an N ratio value
When the value of the ratio is also lower than Fi, a large attenuation is given to the signal on the propagation path with a lower carrier level, and the combiner 12
Then, an operation is performed to disconnect this propagation path. That is, A
Since the AGC voltages of both propagation paths are constantly compared by the GC voltage comparator 15, the propagation path from which a high carrier wave level can be obtained is identified and applied to the combination/separation controller 17.

If it is necessary to disconnect from the S/N comparator 18, a disconnect signal is triggered and applied to the composite disconnect controller 17, which causes the weighting circuit 105 . Or drive 205. In the weighting circuit of the propagation path, a large amount of attenuation is given to the separation signal, and the signal of the propagation path is substantially separated by the combiner 12. At this time, the AGC voltage switch 11 is simultaneously driven, and the AGC voltage switching mode is changed from the common gain control mode to the A
The control mode is switched to perform GC operation. The first and second auxiliary demodulators 106 and 206 compare the S/N ratio after demodulation by taking the AGC voltage into consideration, and when this relationship falls within the allowable range, extreme distortion or It is determined that the interference has disappeared, and a combination recovery signal is sent to the combination/disconnection controller 17 to restore the combination operation. Even if the combining is restored, if the S/N ratio after combining is lower than the S/N ratio of the signal propagation path that provides good quality after passing through the combiner 13, The above-mentioned cutting operation is repeated. In the first and second auxiliary demodulators 106 and 206, the level of the radio pilot signal is constantly monitored, and even though the input electric field is above the critical threshold, the radio pilot signal contained in the modulated wave is If the level falls below the threshold, it is assumed that strong interference has occurred and the signal on this propagation path is separated from the combiner 12 in the same manner as described above.

As explained above, according to the present invention, in addition to the detection-based combination method, an auxiliary demodulator is added to perform FM detection on the signals on each propagation path, thereby selecting a signal with a good S/N ratio. , when the S/N ratio value of the composite signal from multiple propagation paths is lower than the S/N ratio value of the signal of each propagation path, the combining/disconnecting controller selects the signal from the propagation path with the lower S/N ratio. This has the effect of separating the signal.

In the above description, the dual diversity reception method has been taken up as an example, but the generality is not lost for triple diversity reception methods or more. In addition, although Figure 2 shows the space diversity method,
In the present invention, it goes without saying that similar relationships hold true regarding diversity reception of frequency, polarization, angle, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a receiving device for implementing an example of a conventional space diversity receiving method. Figure 2 is a block diagram showing a receiving device for implementing an embodiment of the space diversity receiving system according to the present invention. 101.201...Receiving antenna 102.202@--Receiving frequency converter 103.203
...Variable gain amplifier 104.204...AGC amplifier 105.205...Weighting circuit 106.20
6...Auxiliary demodulator 11...Fist AGC voltage switch 12...Synthesizer 13.e...Demodulator 14...Output terminal 15...Fist/AGC voltage comparison Device 16...Maximum S/N detector 17...Synthesis disconnection controller 18...S/N comparator Patent applicant NEC Corporation Representative Patent attorney Hisashi Inoro

Claims (1)

[Claims] A plurality of reception antennas for respectively receiving modulated waves arriving via a plurality of propagation paths, and a plurality of reception frequency converters for converting the modulated waves respectively transmitted from the plurality of reception antennas into intermediate frequency signals. , a double-sided variable gain amplifier for amplifying each of the intermediate frequency signals, a plurality of AGC amplifiers for controlling each of the plurality of variable gain amplifiers, and an output of each of the plurality of variable gain amplifiers. a plurality of weighting circuits for performing ratio square synthesis control based on the received signals; an AGC voltage switch for performing common gain control among the plurality of propagation paths; and for combining the outputs of the plurality of weighting circuits. and a demodulator for demodulating the output of the combiner, a plurality of auxiliary demodulators for demodulating the outputs of the respective variable gain amplifiers; An AGC voltage comparator for comparing AGC voltages between a plurality of AGC amplifiers and outputs of the plurality of auxiliary demodulators, and for selecting a signal having a maximum S/N ratio from among the outputs. maximum S/N of
a detector; an S/N comparator for comparing the S/N ratio of the selected signal with the S/N ratio of the signal extracted by the demodulator after the synthesis; S/N
If the S/N ratio deteriorates from the S/N ratio of the signal having the maximum S/N ratio, the output of the auxiliary demodulator may exceed a predetermined threshold value and the radio pilot included in the modulated wave and a combination/separation controller for isolating the signal in the propagation path that degrades the S/N ratio from the demodulation system when the signal level is below a predetermined threshold. Features a diversity reception combining method.