JPH0620185B2 - Diversity control system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diversity control system, and more particularly to a diversity control system using a perturbation method for controlling phase combining diversity in a digital wireless line.

[Conventional technology]

In a wideband wireless transmission system using microwaves, etc., a diversity system is used as a measure against fading.In particular, in the digital wireless transmission system, the phase difference between the received signals from two antennas spatially separated from each other is used. The phase diversity type space diversity that controls and synthesizes is used. In space diversity in the digital wireless transmission system, indirect waves such as reflected waves with a delay time difference are suppressed to a small level by combining so as to maximize the amplitude of the combined signal or the signal-to-noise power ratio (S / N). Therefore, the amplitude frequency characteristic of the combined signal within the transmission band is constantly monitored, and control is performed so that the amplitude deviation value within the band is minimized. Therefore, a variable phase shifter that controls the phase difference between two received signals is given a minute phase change, and the control by the perturbation method that determines the direction of the next minute phase change by comparing and judging the amplitude characteristics before and after that is performed. Used. As a concrete method of this comparison judgment, the signal power at a plurality of frequencies within the band is selectively detected, and the variable phase shifter is controlled so that the difference between the maximum value and the minimum value of the detected values becomes smaller. Minimum amplitude deviation type (MI
D) A synthesis method is known, but in addition to this, a notch in-phase synthesis method that can be applied to a multi-carrier method in which a plurality of carriers are transmitted by the same wireless device and has a simple control algorithm (for example, IEICE technical research report CS84-85, P
57-P64) have been proposed. This method controls the variable phase shifter in the direction in which the level of the minimum value among the detected values increases.

[Problems to be solved by the invention]

However, in any of the above-mentioned methods, it is not always controlled to the best state under all input conditions. That is, the signal level is too low at the point where the amplitude deviation is minimized by the control of the MID combining method, and the characteristic deterioration due to interference distortion is eliminated, but there are cases where it is difficult to say that the operating state is the best because there are many code errors due to the influence of noise. is there. In addition, the notch in-phase synthesis method controls the notch (valley of amplitude) so that the level (minimum value) is increased, so the level is high and there is no influence of noise, but the amplitude deviation is large and there is a code due to interference distortion. There are cases where an error occurs and the operating state is not the best. Figure 4 (a) shows the relationship between the direct wave and the interference wave of each signal received by the two antennas is constant (amplitude ratio is about 0.9, the time delay of the interference wave is about 9 ns, and the phase of the direct wave and the interference wave is In relation to one antenna, a notch due to interference appears at a frequency about 6 MHz higher than the center frequency, and on the other antenna, it occurs at a frequency about 6 MHz lower than the center frequency and the bandwidth is about 40 MHz.
(In the case of MHz) and the relative phase relationship between the two received signals is changed (0 to 2π) by the variable phase shifter, the minimum value Gmin of the combined signal amplitude and the amplitude deviation value ΔG = Gm
It is a characteristic view which shows the relationship of ax-Gmin (this is called an evaluation curve). Under this input condition, the control reaching point by the notch in-phase synthesizing method for controlling Gmin to the maximum is the point A, the amplitude deviation value ΔG deviates from the minimum condition, and interference distortion occurs.
The reaching point of the control that minimizes the amplitude deviation value ΔG by the D combining method is the B point, and since the signal level is small and is affected by noise, it cannot be said to be the optimum point. On the other hand, for example, C
If the point can be controlled, the amplitude deviation value ΔG can be small and the signal level can be sufficiently obtained, so that a good code error rate can be obtained. The object of the present invention is to have an improved control algorithm capable of controlling the point C even in the case of the evaluation curve as shown in FIG. Under the circumstances, it is to provide a diversity control method capable of performing good control.

[Means for solving problems]

The diversity control method of the present invention comprises a variable phase shifter that controls the phase difference between two received signals, a combiner that combines the two received signals whose phase difference is controlled, and an output signal of this combiner. Detecting means for selectively detecting signal power at a plurality of frequencies within the transmission frequency band, and a minute phase change is given to the variable phase shifter, and the outputs of the detecting means before and after that are compared and judged to determine the next minute phase change. In a diversity control system for a digital radio line including a control circuit that determines a direction, the control circuit subtracts the minimum value from the maximum value, the minimum value, and the maximum value of a plurality of outputs of the detection means. Calculation storage means for calculating and storing the amplitude deviation value;
When the minimum value increases after giving the minute phase change, the amplitude deviation value increases and the amplitude deviation value is predetermined with the minimum value being equal to or larger than a predetermined first limit value α. And a first judgment means for reversing the direction of the next minute phase change when the second limit value β is less than or equal to the second limit value, and for keeping the direction of the next minute phase change the same as before otherwise. When the minimum value decreases after giving the minute phase change, the amplitude deviation value decreases and the minimum value is greater than or equal to the first limit value α, and the amplitude deviation value is the second limit value. When β or less, the direction of the next minute phase change is kept the same as before, and in other cases, the second judging means for inverting the direction of the next minute phase change and the minute phase change are given. After that, when the fluctuation of the minimum value is not recognized In the case where the amplitude deviation value decreases, the minimum value is less than the first limit value α, and at least the maximum value exceeds a predetermined third limit value γ, the direction of the next minute phase change When the amplitude deviation value decreases and the minimum value is equal to or larger than the first limit value α, the direction of the next minute phase change is held the same as before, and the amplitude deviation value increases. When the minimum value is less than the first limit value α and at least the maximum value exceeds the third limit value γ, the direction of the next minute phase change is kept the same as before and the amplitude deviation increases. However, when the minimum value is equal to or larger than the first limit value α, the direction of the next minute phase change is reversed, and when the fluctuation of the amplitude deviation value is not recognized, the direction of the next minute phase change is set as the front. And a third judgment means for holding the same. .

〔Example〕

The present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the system configuration of an embodiment of the present invention. In FIG. 1, two reception signals 101 and 102 received from antennas 1 and 2 are converted to intermediate frequencies by frequency converters 3 and 4, respectively, and are combined by a combiner 5 and then an intermediate frequency amplifier 6 is output. It is sent to a demodulator (not shown). The output of the local oscillator 7 is divided into two.
The phase difference between the two received signals is controlled by controlling the variable phase shifter 8. A part of the intermediate wave signal 103 synthesized by the synthesizer 5 is branched and added to the frequency converter 9, where it is mixed with the output fi (i = 1 to n) of the voltage controlled oscillator (VCO) 10. The reduction filter 11 and the detector 12 are sent to the control circuit 13 after passing through them. The control circuit 13 includes a memory and an arithmetic circuit, gives a minute phase change to the variable phase shifter 8 by the control signal 104, and controls the signal 105.
Change the frequency fi of the VCO 10 to sequentially detect the signal power of n waves in the band, and detect the maximum value Gmax and the minimum value Gmin among them, and the difference between the maximum value and the minimum value (amplitude deviation value) ΔG = G
Max-Gmin is calculated and stored, and these values before and after the minute phase change are compared and determined to determine the direction of the next minute phase change given to the variable phase shifter 8.

FIG. 2 is a flow chart for explaining the operation of the control circuit 13 shown in FIG. The control operation will be described in detail below with reference to this flowchart. In the flowchart of FIG. 2, Gi is the detection value obtained by A / D converting the output of the detector 12 at each frequency number fi, δGmin and δ.
ΔG is a change in Gmin and ΔG before and after a minute phase change, δ ₁ and δ ₂ are discrimination limit values for discriminating δGmin and δΔG, and α, β and γ are preset constants, respectively, a minimum value and an amplitude. The first and second changes the judgment depending on whether the deviation value and the maximum value are greater than or less than this value.
And the third limit value. Further, the control circuit 13 is provided with an A memory for storing a value after giving a minute phase change to the variable phase shifter 8, a B memory for storing a value before the change, and an arithmetic memory used for arithmetic operation. Has been.

When the control circuit 13 starts its operation, first, step 201
Initialization is performed with and each memory value is set to the initial value.
At step 202, each data (Gmax, Gmin, Δ
G) to B memory, then steps 203-205
By applying a minute phase change in a certain direction to the variable phase shifter 8 by sequentially changing the frequency fi from f ₁ to fn, the detection value Gi obtained by A / D converting the output of the detector 12 is stored in the arithmetic memory. Gi is compared to obtain the minimum value Gmin, the maximum value Gmax and the amplitude deviation value ΔG, which are stored in the A memory. Next, in steps 206 to 221, Gmin and .DELTA.G of both the A and B memories are compared, and the direction of the next minute phase change is determined according to the determination criteria shown in the determination sectional view of FIG. Step 20 above
6 to 221, the direction of the next minute phase change is determined such that the conventional notch in-phase synthesis method simply increases Gmin and the MID synthesis method decreases ΔG. In the case of the evaluation curve as shown in FIG. 10A, the positions are controlled to the points A and B, respectively. On the other hand, according to the control method of steps 206 to 221 in FIG. 2, it is possible to control the point C.

The judgment division diagram of FIG. 3 is the steps 206 to 221 of FIG.
The control circuit 13 in FIG. 6 shows a reference for comparison judgment, and holds the direction of the next minute phase change in the same direction as before with respect to the change δGmin of the minimum value and the change δΔG of the amplitude deviation value before and after the minute phase change. It is shown whether to do it or to reverse it and make it the opposite direction. In addition, the arrow in the figure is shown in FIG.
It corresponds to the direction of change in (a)-(d). As shown in FIGS. 2 and 3, in the control circuit 13 shown in FIG. 1, (1) the minimum value Gmin is applied after the minute phase change is given.
If There was increased (δGmin> δ _1), the step 207
The amplitude deviation value ΔG increases (δ
ΔG> δ ₂ ) and the minimum value Gmin is the first predetermined value
If the amplitude deviation value ΔG is less than or equal to the predetermined second limit value β above the limit value α, the direction of the next minute phase change is reversed, otherwise the direction of the next minute phase change is reversed. Is kept the same as before, and (2) when the minimum value Gmin is decreased after giving a minute phase change (δGmin <−δ ₁ ), the amplitude deviation value ΔG is decreased by the route of steps 211 to 213. (ΔΔG <−δ ₂ ) and Gmin is α or more and ΔG is β or less, the direction of the next minute phase change is kept the same as before, and otherwise the direction of the next minute phase change is reversed. ,
(3) If a small change in the minimum Gmin in After giving a phase change is not observed (| | δGmin ≦ δ _1), the step 21
By the paths 4 to 219, when the amplitude deviation value ΔG decreases and the minimum value Gmin is less than α and the maximum value Gmax exceeds the predetermined third limit value γ greater than α, the direction of the next minute phase change And the amplitude deviation value ΔG decreases and the minimum value Gmin is greater than or equal to α or the maximum value Gmax is less than γ, the direction of the next minute phase change is held the same as before, and the amplitude deviation value Δ
G is held the same as before the direction of the next minute phase changes when crossing an increase (δΔG> δ ₂₎ to and increased value Gmax at less than the minimum value Gmin are α is gamma, the minimum value Gmi increased amplitude deviation ΔG is
When n is greater than or equal to α or the maximum value Gmax is less than γ, the direction of the next minute phase change is reversed and no fluctuation is recognized in the amplitude deviation value ΔG (| δGmin | <δ ₁ , | δΔG | <δ ₂ ) At this time, the direction of the previous minute phase change is maintained. With this configuration, two reception signals 1
If the relationship between 01 and 102 is shown by the evaluation curve in FIG. 4 (a), the variable phase shifter 8 is
G is controlled to decrease, and when it is at point B, Gmin
By controlling in the direction of increasing C, the operating point can be moved in the arrow direction and stabilized at point C.

FIG. 4 (a) is an evaluation curve showing the relationship between the amplitude deviation value ΔG and the minimum value Gmin when the relative phase of the two received signals is changed as described above, and is at any position on the evaluation curve. The operating point moves in the direction of the arrow for each minute phase change given to the variable phase shifter, and reaches the point C and stabilizes. Although the evaluation curve changes when the input condition changes due to fading, the evaluation curve operates similarly to the above, and is controlled to a position corresponding to point C in FIG. 4 (a). Fig. 4 (b) shows that the evaluation curve is more Gmin than the case of Fig. 4 (a) for the limit value α of Gmin.
The case of being located on the larger side of. In this case,
Since the control direction of the part indicated by R is reversed from that in the case of FIG. 4 (a), there is a secondary stable point also at the point C ₂ facing C ₁ , depending on the initial conditions at the start of operation. May converge to the C ₂ point. However, this point is close to the C ₁ point and can be tolerated from both noise and interference distortion, and when the level at the C ₁ point decreases to α or less, this point becomes an unstable point, and therefore, FIG. 4 (a). It will be controlled to point C as shown in FIG. FIG. 4 (c) shows the case where the evaluation curve is on the side where Gmin is smaller than that in the case of FIG. 4 (a), and the operating point is C
₃ , ΔG is slightly increased, but the noise and interference are controlled in a well-balanced state. Fig. 4 (d) and Fig. 4 (a)
In order to prevent the occurrence of the secondary stable point C _{5 in} addition to the normal stable point C _{4 in} the intermediate state of (b), ΔG
Is above a certain limit value γ, Gmin is greater than α (Gm
Even in the case of in ≧ α, the control direction shown by the broken line arrow S in FIG. 4 (d) is not provided. Also, δΔG, δ
When both Gmin do not change, that is, when the movement of the operating point on the evaluation curve is small by giving a minute phase change, the same movement direction is maintained, but the amount of minute phase change should be increased. If you can move to a stable point quickly.

FIG. 5 is a block diagram showing the system configuration of another embodiment of the present invention, which is an embodiment provided with a plurality of detectors as the means for detecting the in-band signal power. In FIG. 5, the variable phase shifter 14 for controlling the phase difference between the two received signals is provided in the intermediate and intermediate wave number stage of the output of the frequency converter 4, unlike the case of FIG. Is provided as n detectors 15-j (j is 1 to n, each of which is composed of a band filter and a detector or a local oscillator, a frequency converter, a low-pass filter and a detector). Control circuit 16
Is similar to the control circuit 13 of FIG. 1 except that it is configured to detect the outputs of the n detectors and perform A / D conversion, and the same control as described above is performed.

In the above description of FIGS. 2 and 3, Gmax is determined in steps 217 and 219, but this determination is not always necessary. That is, if this step is omitted, the control direction (the direction of the arrow) of the portion indicated by T is reversed in each evaluation curve of FIGS. 4 (a) to (d),
The effect of this is that the range of convergence at the secondary stable point is slightly increased, or the time until the stable point is reached is slightly different, and it is clear that the same effect as the above description can be obtained. is there.

〔The invention's effect〕

As described above, according to the diversity control method of the present invention, regardless of the input condition, both the noise due to the decrease in the signal level and the interference distortion due to the amplitude deviation can be phased under a well-balanced and good operating condition. There is an effect that synthesis can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the system configuration of an embodiment of the present invention, FIG. 2 is a flow chart showing the operation of the control circuit of FIG. 1, and FIG. 3 is steps 206 to 22 in FIG.
FIG. 4 (a) to (d), which is a classification chart showing the criteria of the judgment operation of 1.
Is a characteristic diagram showing an evaluation curve, and FIG. 5 is a block diagram showing a system configuration of another embodiment of the present invention. 1,2 ... Antenna, 3,4,9 ... Frequency converter, 5
...... Combiner, 6 ・ ・ ・ Intermediate frequency amplifier, 7 ・ ・ ・ Local oscillator, 8,14 ・ ・ ・ Variable phase shifter, 10 ・ ・ ・ Voltage controlled oscillator (VCO), 11 ・ ・ ・ Reduction filter, 12 ・ ・ ・ Detector,
13, 16 ... Control circuit, 15-j ... Detector.

Claims (1)

[Claims] 1. A variable phase shifter for controlling a phase difference between two received signals, a combiner for combining the two received signals whose phase difference is controlled, and a transmission frequency band from an output signal of the combiner. Detecting means for selectively detecting the signal power at a plurality of frequencies in the inside of the variable phase shifter, and a minute phase change is given to the variable phase shifter, and the outputs of the detecting means before and after that are compared and determined to determine the direction of the next minute phase change. In a diversity control system for a digital radio line including a control circuit, the control circuit has a maximum value, a minimum value, and an amplitude deviation value obtained by subtracting the minimum value from the maximum value among a plurality of outputs of the detection means. And a calculation storage means for calculating and storing, and a first limit value α in which the amplitude deviation value increases and the minimum value is predetermined when the minimum value increases after the minute phase change is given. The direction of the next minute phase change is inverted when the amplitude deviation value is equal to or less than the second limit value β which is set in advance, and the direction of the next minute phase change is the same as the previous direction otherwise. A first determination means held in
In the case where the minimum value decreases after the minute phase change is applied, the amplitude deviation value decreases and the minimum value is equal to or more than the first limit value α, and the amplitude deviation value changes to the second value.
A second judgment means for keeping the direction of the next minute phase change the same as before when the limit value β is less than or equal to the limit value β, and for inverting the direction of the next minute phase change in other cases; In the case where the variation of the minimum value is not recognized after the change is given, the amplitude deviation value is reduced, the minimum value is less than the first limit value α, and at least the maximum value is predetermined. When the limit value γ is exceeded, the direction of the next minute phase change is reversed, and when the amplitude deviation value decreases and the minimum value is greater than or equal to the first limit value α, the direction of the next minute phase change. The same as before, the amplitude deviation value increases, the minimum value is less than the first limit value α, and at least the maximum value exceeds the third limit value γ, the next minute phase Keep the same direction of change as before, and increase the amplitude deviation value. Wherein the serial minimum first limit value α
In the above case, a third judging means for inverting the direction of the next minute phase change and holding the direction of the next minute phase change in the same direction as before when the fluctuation of the amplitude deviation value is not recognized. Diversity control method characterized by