JPS5843639A - Automatic gain control amplifier - Google Patents

Abstract

PURPOSE:To obtain a receiving output having a constant level, by providing the sampling and holding circuits whose number is same as the number of level detectors and slave stations, and which are operated by synchronizing with a burst signal from the slave station, on an output of a variable gain control amplifier of a master station. CONSTITUTION:In a time division multi-direction radio system placed between a master station and plural slave stations scattered in the multi-direction, a variable gain control amplifier 21, and sampling SP and holding HD circuit 30-41 whose number is same as the number of level detectors 23 and slave stations are provided on a receiving device of the master station. The receiving device of the master station receives a burst- like time division signal which has taken frame synchronization, from the slave station, an SP switch SW30 is closed by synchronizing with a burst receiving signal from the slave station, and an HD circuit 31 holds a detecting level of the detector 23. In the same way, by a burst signal from other slave station, an output of the detector 23 is held by HD circuits 34, 37 and 40 in order. By the following frame, SWs 32, 35, 38 and 41 are closed by synchronizing with the burst signal of the slave station, respectively, the amplifier 21 is controlled by a held level, and a receiving output of a burst signal whose level is different is made constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time-division directional wireless communication system.

FIG. 1 shows a time-division system in which the present invention is used to communicate with a large number of distributed slave stations, in which each slave station uses the same radio frequency and communicates in the time domain. FIG. 2 shows the conventional master station receiving apparatus shown in FIG. 1.

Next, the time-division multidirectional radio system and the object of the present invention will be explained with reference to FIGS. 1 and 2. In addition,
For convenience of explanation, the number of slave stations is assumed to be four.

1 is the master station device, and the transmitted wave of the master station device 1 is 1 in Fig. 2.
0. to in the master station transmission wave 10.

tl...tll represent time on the time chart. The signal F between to and 1.0 of the transmission wave 10 is a frame synchronization signal, and the signal A between tl and t2
is a transmission signal to the slave station 2 shown in FIG. Similarly, the signal B between ts and ts is the transmission signal to the slave station 3, the signal C between ts and t4 is the transmission signal to the slave station 4, and the signal between t4 and ts is the transmission signal to the slave station 5. This is the transmission signal for. The signal from ts to ts is the frame synchronization signal F 69 times, and then similarly, the time from tl to ts is set as one cycle, and the slave stations z, s, 4.511c are repeatedly transmitted. Each slave station receives the transmission power signal of the master station transmission wave 10, and receives the transmission power signal from to to tl and from ts to ts.
...is sent over and over again.

Based on the frame synchronization signal F, the signal assigned to the local station is selected. In addition, the transmitted signal of the nave is bit synchronized with the received signal (Kazu frame synchronization). , Ega□
The signals are adjusted and transmitted at each slave station so that the time sequence is the same as that of the transmission signal from the master station at the master station receiver.

This relationship is shown at 11.12.13.14 in FIG. 2, and is transmitted from each slave station 2 e J and 4 a 5.

It shows a burst signal waveform. At the master station receiving device h, the received waveform shown at 15 in FIG. 2 is received.

In an actual system, there are delay time differences between each propagation path, etc.), and each slave station transmits data with the same delay time based on the frame synchronization signal of the signal received at the slave station. The received signals will overlap each other on the receiving side of the master station.

Therefore, the transmission timing is adjusted so that the received waveform has the same time relationship as the transmitted waveform of the master station. The waveform received at the master station in this manner is shown at 15 in FIG. In this figure, the reason for the level difference in the signals received from each slave station is due to the difference in propagation distance.
Depends on whether or not aging occurs. When the level difference between the two is large, :,.

It sometimes reaches 20-30 db. In order to perform demodulation in the demodulator of the 11 master station receiver having these level differences, the dynamic range of the demodulator must be widened, making demodulation difficult.

When using a conventional automatic gain control amplifier as shown in Figure 3, there is a limit to the response speed of the amplifier.
As shown in 16 of the figure, it was difficult to obtain a uniform output level.

Here, to explain the configuration of the conventional automatic gain control section and width amplifier shown in FIG. 3, 2o is an input signal terminal, 2no is a variable gain amplifier, 22 is an output signal terminal, 23 is a level detector, and so on.
24 is a low-frequency F wave generator, and 25#i is a gain control terminal.

In this method, the output level is detected by a level detector 23, and feedback is applied to the gain control terminal 25 so that the output level is constant. The variable gain control amplifier 210 control voltage versus gain conversion coefficient is assumed to be 2. In addition, the level detector 23 is a detector 1 having a conversion coefficient as shown by the broken line in FIG.
00, a reference voltage V, and an adder that takes the difference between the output voltage of the detector 100. The transmission coefficient of the low-pass F wave filter 24 is ~), and due to the frequency relationship, H(.)=1. The input/output relationship of the automatic gain control amplifier shown in Figure 3 is (
i) It is shown by the formula.

V6 = (V@KIV6) ・H−Kz ・Vi
--------(1) However, Vi is the input signal level,
Let vo be the output signal level. H(0) indicates the value of W-○.

Equation (1) is ζ. Now, if *IH(11h"Vi > 1), then Equation (2) is K
If IV0=V, and (2) is a constant reference voltage, and K is constant, then vOIIi is constant.

In reality, the feed function H(b) of the low-pass F-wave generator 24 is a function of the frequency, and when the input signal level handled by this method fluctuates in a stepwise manner, the response speed of the control loop changes. For this reason, a uniform level as shown at 16 in FIG. 2 cannot be obtained.

In order to solve these drawbacks, the present invention adds one variable gain control amplifier to the automatic gain control amplifier of the master station receiving device, and a level detector connected to the output signal terminal of the variable gain control amplifier. do.

This invention provides an automatic gain control amplifier that can obtain a constant output from burst-like received signals of different levels from multiple directions.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 4 is a block diagram of an automatic gain control amplifier which is an embodiment of the present invention, and FIG. 5 is a time chart for explaining FIG. In FIG. 4, 20 is a received signal input terminal;
2 is a variable gain control amplifier, 22 is an output signal terminal, and 23 is a variable gain control amplifier.
is a level detector. 30 is a sampling switch for the output signal of the level detector 23 corresponding to the burst signal A, 3 is a circuit that holds the signal sampled by the sampling switch 30, and 32 is a gain control terminal for the hold output signal of the hold circuit 3. 25 for a certain period of time, similarly 33.36.3
9 has the same function as the sampling switch 30, and is a sampling switch for the output signal of the level detector 23 corresponding to the burst signals B, C, and DK, respectively. 34.37° 40 is a hold circuit similar to the hold circuit 3. , 35, 38, and 41 are switches similar to the switch 32, 42 is a switch control circuit for controlling ON/OFF timing of each switch, and 43 is a control terminal of each switch.

Reference numeral 50 in FIG. 5 is a received signal received by a multidirectional slave station, which is an input signal of the automatic gain control amplifier of the present invention, and is applied to the received signal input terminal 20 in FIG. Further, the input signal 50 is the same as 15 in FIG. Focusing on the signal burst AK of the input signal 50, the parse) A is a signal transmitted from the slave station 2, and occupies the time from t1 to t2 and from ta to t7. Input signal 50 is amplified by variable gain control amplifier 21 and level detected by level detector 23 . Parse) The output signal of the level detector 23 between tl and taO of A is sampled by the sampling switch 30. This timing of sampling is performed from t2x to t2 of Parse A, as shown at 51 in FIG. 5, and in the waveform of this figure, sampling is performed when the signal is at a high level. Further, this time control is performed through the control terminal 43 of the switch control circuit 42.

Nose from tl to t2) Level detector 2 corresponding to A
The output signal of No. 3 is subjected to sampling as described above, and the unsoldering output is applied to the hold circuit No. 3 to maintain its level. This waveform #i is held from p't to p2 as shown at 52 in FIG. The gain control signal for a4-st A applied from ta to t7 is
2 is turned ON from ta to t7 at the timing shown at 53 in FIG. 5, the level held from pl to p2 is applied to the terminal 25 to control the gain. In other words, the magnitude of the gain control signal from ta to t7 is determined based on the signal level from tl to t2 of the previous frame signal from the same direction, and the output level from ta to t7 is constant. control so that Similarly, from i2 to t
Level detector 230 no 9- is also used for i+-st B of a.
5) The output signal of the level detector 23 corresponding to
Sampled at the timing a, this level is held by the hold circuit 34, and the held signal is controlled by the switch 35 so that the output is kept constant through the gain control terminal 25 from t7 to ta at the timing shown at 55 in FIG. Control. Again, the sampling switch 33 samples the BK from t7 to tl from tsx to ta in 54 in FIG. 5, holds it, and so on, and so on. Similarly, for the burst C from 50 ta to t4 in FIG. 5, the switch timing is set at 56.57 in FIG. 50 t4 in figure 5
to t5) For D, the fifth
Similar operations are repeated at timings 58 and 59 in the figure.◎ As described above, in this control system, there is a time delay of 17 lems from level detection to control. Naturally, this time difference (ta
-tt ), if a level difference occurs in the same burst, an output level deviation remains.

However, for example, the attenuation rate of fading that occurs in a spatial propagation path in the 2 GHz band is 1 dB per 10 milliseconds.
If the frame period is a few milliseconds or less, the output level difference can be ignored.

As explained above, by having the same number of sampling circuits and hold circuits as one slave station, and repeating the above timing, sampling, hold, and control for each burst, time-division multidirectional communication creates a level difference between bursts. It is effective as an automatic gain control amplifier for the system's master station receiver. In addition, in this embodiment, for burst-like received signals with different levels from multiple directions, the level is sampled and held for each burst, and the gain control signal of the received signal from the same direction in the next sampled frame is The hold signal is used to construct an automatic gain control amplifier. As a result, 5 L/-eA-OJI &, 6'4-2) (P
i, 1. This has the advantage that it is possible to obtain a constant power and pel for one pair, and that the dynamic range of the demodulator that follows this can be suppressed.

Note that the automatic gain control amplifier according to the present invention does not have a feedback continuous control loop, but a discrete λ control root that repeats sampling and holding, and the stability conditions of the roots are different, but the essence of the present invention will be explained here. I'll omit it because it's kakawashiganah.

- Next, a second embodiment of the present invention will be explained with reference to FIGS. 6 and 7. FIG. 6 is a block diagram of an automatic gain control amplifier according to a second embodiment of the present invention, and FIG. 7 is a time chart for explaining FIG. 6. In FIG. 6, parts with the same symbols as those in FIG. 4 have the same functions as those with the same symbols in the same figure.

To the received signal input terminal 2o in FIG. 6, a master station received input signal for time-division multidirectional communication is applied, with a level difference between the bursts shown at 60 in FIG. 7, from t1 to t6 as one frame □. This is the same as 50 in FIG. 4;,i
, is amplified by the variable gain control amplifier 21 in FIG. 6 to obtain an output signal from the output signal terminal 22, but a part of the output signal is branched and the output level is detected by the level detector 2311C. Ru.

The detected signal is transferred to the sampling switch 30°33.
36. Added to 39. sampling switch 30,
When 33, 36, and 39 are respectively on, the signals of 79 are held by the hold circuits 3i and 34.

37 and '40, and that level is maintained.

The respective held signals are sent to switches 32, 35° 38
．． The output signal of the hold circuit 48 is applied to the gain control terminal 25 and controlled so that the output level of the output signal terminal 22 is constant.

These operating states will be explained using the time chart of FIG. In the input signal 60, from time t'i to t2 and from time t6 to tl is a burst A which is a received signal from the slave station 2. Here, we will focus on this perspective) A. t
The desired AO level between l and t2 is detected by the level detector 23, and the sampling switch 30 is set at the time t2.
It is turned on during the period from tag to tag, and the level detected signal is added to the hold low 31 and held. This time tal and ta2
is the time t as shown at 61 in the time chart of FIG.
1 and tl, or are set to be inside them. This is done through the terminal 46 by the switch control circuits 4 and 5. Furthermore, the timing of these is set in consideration of wiring delays, jitter, aging, etc. on the actual circuit.

&Kt1 to t2 The output signal of the hold circuit 31 for A is held from pl to p2 as shown at 62 in FIG. Then, parse between t6 and t7 of the next frame) 6 in Figure 87 immediately before A is input
3, the switch 32 is turned on from time tx4 to tea, and the switch 47 is turned on from time tl6 to t6.
It is turned on as shown in 11 in the figure, its input level is held in the hold circuit 48, and a hold output signal is applied to the control terminal 25 from t6 to t70 shown in 22 in FIG. 7 through the hold circuit 48. The output level of the hold circuit 48 is held as the contents of the hold are rewritten the moment the switch 47 is turned on. In addition, the switch 47
The time it takes for the switch to turn on is 32.35mB'8a4
As shown in the time chart, it is set to be the same as or inside the time when 1 is turned on. Similarly below, parse)
For B, the sampling switch 33 is turned on from tb to tb3 at 64 in FIG. 7, and its level is held from p3 to p4 as shown at 65 in FIG.
The switch 35 switches from txt to t as shown at 66 in FIG.
It is on for y7. Furthermore, when the switch 42 is turned on from ts7 to tl as shown in No. 2 of FIG. Add through.

Parse) Repeat the same operation for C and D.

The control signal for each reception burst from each direction has a waveform as shown at 72 in FIG.

60-1 in Figure 7. The control signal generated from the received signal of one frame that occupies ts from 9t6 to tl, as shown in 1, after one frame as shown at 72 in Figure M7, and from 6pa0 in Figure 7. It is used as a control signal for signals from t6 to 111.

In this way, the second aspect of the present invention? In this embodiment, the received signal is a burst signal from a multi-directional slave station, which is a front wing.Sampling and holding are performed for each burst signal, and this held signal is sampled as the input signal of the next frame. It is used as a gain control signal for received signals from the same direction.

This makes it possible to obtain a reception output with a constant output level, and the dynamic range of the demodulator that follows it does not need to be narrow, which is effective in system design.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a time-division multidirectional radio system in which the present invention is used, FIG. 2 is a time chart when the automatic gain control amplifier of the conventional master station receiving device in FIG. 1 is used, and FIG. The figure shows a configuration diagram of a conventional automatic gain control amplifier.
Fig. 4 is a block diagram of an automatic gain control amplifier which is an embodiment of the present invention, Fig. 5 is a time chart for explaining Fig. 4, and Fig. 6 is an automatic gain control amplifier which is an embodiment of the present invention. A block diagram of the gain control amplifier, FIG. 7 is a time chart for explaining FIG. 6. 20... Reception signal input terminal, 2... Variable gain control amplifier, '22... Output signal terminal, 23... Level detector, 25... Gain control terminal, 30, 33, 36° 39...Sensilling switch for the output signal of the level detector 23 corresponding to the burst signal ASD, 31.
34, 37.40...Circuit that holds the signal sampled by the sampling switch, 32.35
．． ;j8.41...Switch for supplying the hold signal of the hold circuit to the gain control terminal 25 for a certain period of time, 4
2...Switch control circuit that performs ON-OFF timing control of each switch, 43...Control terminal of each switch. Figure 1 Figure 3 Figure 4 Figure 1

Claims (1)

[Claims] In a multidirectional wireless system that performs time-division communication between one master station and at least two or more slave stations scattered in multiple directions, a 7-rem synchronized burst-like signal from the slave station is used. The automatic gain control amplifier of the master station receiving device that receives a time division signal includes one variable gain control amplifier and a level detector connected to an output terminal of the variable gain control amplifier, and the level detector is connected to an output terminal of the variable gain control amplifier. The output of the received burst time-division signal is synchronized with a signal synchronized with the received burst-like time-division signal, and the number of s/f shilling and holding circuits equal to the number of slave stations performs shilling and holding for each burst. An automatic gain control amplifier characterized in that a hold signal is used as a gain control signal for a received signal from the same slave station in the next seven frames after sampling, and the output level of the gain control amplifier is kept constant.