JPH0411415A - Antenna selection diversity reception system - Google Patents

Abstract

PURPOSE:To select an optimum reception antenna by using a reception signal intensity and its time differentiating coefficient so as to estimate an average signal intensity of each reception antenna and estimating the mean signal intensity by a difference of two measurments. CONSTITUTION:A reception signal intensity measuring circuit 79 measures reception signal intensities R1, R2 obtained from each reception antenna and a reception signal intensity differentiating coefficient measurement circuit 11 measures dR1, dR2 and mean signal intensities M1, M2 at a reception time are calculated and estimated from the parameters above. When the relation of M1>M2 exists in the mean signal intensities, a reception signal antenna 71 is selected for the reception and when not, a reception antenna 72 is used for receiving a reception signal burst. In an embodiment shown in the Figure, a reception intensity R3 of the antenna 71 is held by an S/H circuit 13 in a timing circuit 77, the antenna 72 is selected and a reception intensity R4 is held by an S/H circuit 14. Similarly intensities R1, R2 are obtained, and held in S/H circuits 80, 81. Subtractors 41, 42 obtain differences R1, R2 to calculate the intensities M1, M2 and to select an antenna.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an antenna selection diversity reception system, which overcomes fading that occurs in wireless communications such as mobile communications, and enables stable and high-quality information transmission. The present invention relates to an antenna selection diversity reception method for achieving this.

[Conventional technology]

A conventional antenna selection diversity reception system will be explained using a three-channel time division multiplex transmission system (hereinafter referred to as TDM system) as an example.

FIG. 9 shows a configuration diagram of a conventional antenna selection diversity receiver. In the figure, 71 and 72 are receiving antennas, 73 is a selection switch, 74 is a receiving/demodulating section, 75 is a frame synchronization circuit, 76 is an antenna selection circuit, a timing circuit 77, a switch control circuit 78, a received signal strength measurement circuit 79, and the size The received signal strength measuring circuit 79 is composed of a comparison circuit 82 and two sample and hold circuits 80 and 81.

The receiver receives a signal from a reception antenna 71 or 72 via a selection switch 73 at a reception/demodulation section 74, and inputs the demodulated signal to a frame synchronization circuit 75 to perform frame synchronization. The antenna selection circuit 76 determines the reception time of the signal burst destined for its own station from the frame synchronization signal obtained from the frame synchronization circuit 75, switches the selection switch 73 just before that time, and selects the reception signal by the two reception antennas 71 and 72. Compare the strengths.

FIG. 10 is a diagram for explaining the processing procedure of the conventional method. FIG. 2A shows a frame structure of a received signal, and is an example of a 3-channel/frame TDM system. In both cases, the signal towards the local station is assigned to the third burst within the frame.

The timing circuit 77 in FIG. 9 first sends a trigger signal to the received signal strength measurement circuit 79 at time t1 immediately before the reception time of the signal burst toward the own station, and if the currently selected receiving antenna is the receiving antenna 71, The sample hold circuit 81 detects the received signal strength R from the receiving antenna 71.
Hold 1.

Immediately thereafter, the switch control circuit 78 switches the selection switch 73 to the other receiving antenna 72, and the sample hold circuit 80 switches the receiving antenna 72 at time t2.
The received signal strength R2 is held.

The magnitude comparison circuit 82 uses these two received signal strengths R, , R2
Compare the size of.

The switch control circuit 78 selects the receiving antenna with the higher received signal strength based on the comparison result of the magnitude comparison circuit 82, and continues to receive the signal burst toward its own station.

For example, when the received signal strength by the receiving antenna 71 and the receiving antenna 72 changes as shown in a and b in FIG. 1O(B), the switch selection signal from the switch control circuit 78 becomes as shown in FIG. 1(C). . The received signal strength of the receiving antenna 71 at time t1 of X in the figure (C) is a in the figure (B).
The received signal strength of the receiving antenna 72 at time t2 on y in the same figure (C) is R2 on b in the same figure (B), and since the received signal strength is R1>R2, the reception signal strength toward the own station is The signal burst is received by the receiving antenna 71. In this way, R2 and R2 are compared for each frame and the antenna with the higher received signal strength is selected.
The average strength of the signal sent to the demodulator 74 can be maintained high, and a diversity effect can be obtained.

[Invention or problem to be solved]

However, the conventional method has the disadvantage that a sufficient diversity effect cannot be obtained when the rate of change of the received signal strength is fast, that is, when the fading rate is fast. This is because the received signal strength changes after measuring the received signal strengths R3 and R2.

FIG. 11 shows a diagram for explaining the above conventional problems. This figure shows a case where the received signal strength by the selected receiving antenna is not necessarily high.

If the reception intensity by the receiving antennas 7I and 72 shown in FIG. 9 changes as shown in a and b in FIG.
Therefore, the signal burst towards the local station is sent to the receiving antenna 71.
received.

However, the received signal strength is reversed immediately after that at t in FIG. 11(B), and the signal burst toward the local station is received by a receiving antenna with a low received signal strength. For this reason, there is a problem that the above method cannot be applied when the fading speed is fast.

The present invention has been made in view of the above points, and an object of the present invention is to provide an antenna selection diversity reception system that can obtain a diversity effect even when the fading rate is high.

[Means to solve the problem]

In the antenna selection diversity reception method, which selects one antenna from multiple receiving antennas and connects the selected receiving antenna to the receiver, the received signal strength received by each receiving antenna and the received signal strength of each received antenna are The average signal strength of each receiving antenna at the reception time is estimated from the time differential coefficient, and the receiving antenna that obtains the largest average signal strength is selected.

In addition, in the antenna selection diversity reception method in which one antenna is selected from multiple receiving antennas and reception is performed by connecting the selected receiving antenna to the receiver, the received signal strength for each receiving antenna is measured twice. ,
The average signal strength of each receiving antenna at the reception time is estimated from the difference between the two measurements for each receiving antenna and the received signal strength for each receiving antenna, and the receiving antenna that obtains the largest average signal strength is selected.

[Effect]

In addition to the received signal strength, the time derivative of the received signal strength is used to estimate the average signal strength of each receiving antenna, and
Since a receiving antenna is selected by estimating the difference between two measured values and the average signal strength of each receiving antenna, the correct receiving antenna can be selected even in a situation where a receiving antenna selection error occurs.

〔Example〕

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

Components that are the same as those in FIG. 9 are designated by the same reference numerals, and their explanations will be omitted.

The antenna selection circuit 76 includes an average value estimation circuit 10, a received signal strength differential coefficient measurement circuit 11, and a received signal strength measurement circuit 7.
9th grade is provided.

In the present invention, the signal from the reception antenna 71 or 72 is received by the reception/demodulation unit 74 via the selection switch 73, and the reception time of the signal burst destined for the local station from the frame synchronization signal circuit 75 is determined based on the demodulated signal. Then, just before that time, switch the selection switch 73 to select the receiving antenna 71.7.
2, the received signal strength by the two antennas and each time differential coefficient of the received signal strength are compared.

FIG. 2 shows a diagram for explaining the processing procedure of the first embodiment of the present invention. FIG. 1A shows the frame structure of the received signal, which is the same as the conventional example shown in FIG. 1O.

The timing circuit 77 shown in FIG. holds the received signal strength R1 from the receiving antenna 71.

At the same time, the signal is also sent to the receiving/demodulating section 74, and the time differential coefficient dR is obtained by differentiating the signal strength received by the receiving antenna 71 using the differentiating circuit 12.

is held in the sample hold circuit 13. Immediately thereafter, the switch control circuit 78 switches the selection switch 73 to the other receiving antenna 72, and at time t2, the received signal strength R2 from the receiving antenna 72 is held in the sample hold circuit 81, and the received signal strength R2 from the receiving antenna 72 is The time differential coefficient dR2 obtained by differentiation by the differentiating circuit 12 is held in the sample hold circuit 14.

The above parameters R1, R2, dR3, and dR2 are input to the average value estimation circuit IO. In the average value estimation circuit lO, 4
Using the three parameters R, , R2, dR, dR2, each receiving antenna 7 at the reception time of the signal burst is
Find the average received signal strength of 1.72.

For example, when the received signal strength by the receiving antennas 71 and 72 changes as shown in a and b in FIG. 2(B), the time differential coefficients correspond to a and b in FIG. 2(C), respectively.

Receiving the signal burst toward the local station using the four parameters of the received signal strength R, , R, obtained in Fig. 2 (B), and the time fl coefficients dR, dR2 obtained in Fig. 2 (C). The average received signal strength M1, M2 of each receiving antenna at a time is determined by the following formula.

M+ =R+ 10dR, ((t, + t t
)/(2-t + ))...(1) (However, i=1.2) However, t is the signal burst reception start time for the own station, and t is the signal burst reception start time for the own station. This is the reception end time. When the average received signal strength M,,M, is estimated using the above equation, it becomes as shown in FIG. 2(D), and the average received signal strength becomes M + < M t. This information is transmitted to the switch control circuit 78 in FIG. 1, and the switch control circuit 78 selects the receiving antenna 72 as shown in FIG. 2(E).

In the first embodiment, a receiving antenna is selected by estimating and comparing the average signal strength of each receiving antenna 71, 72 at the receiving time from the time differential coefficient of the received signal strength.
Due to the transient response of 2, the correct time derivative may not be obtained.

FIG. 3 shows a flowchart for explaining the operation of the average value estimation circuit IO according to the first embodiment of the present invention.

The received signal strength measuring circuit 79 measures the received signal strengths R1 and R2 from each receiving antenna (step 300), the received signal strength differential coefficient measuring circuit II measures dR, dR2 (step 301), and parameters R, R2. ,dR,,
From dR2, the average signal strength at the reception time M, , M2
is estimated by calculating the above equation (1) (step 30
2). If the average signal strength is M, >M2, the receiving antenna 71 is selected and received (steps 303 and 304).

If the average signal strength is not M + > M 2, the receiving antenna 72 receives the signal (steps 303 and 305). The received signal burst is terminated (step 306).

FIG. 4 shows the influence of the transient response of the differentiating circuit 12 in the first embodiment of the present invention. When the received signal strength changes as shown in FIG. 2(B), the received signal strength output waveform from the receiving/demodulating section 74 in FIG. 1 is shown by the thick line in FIG. 4(A). , is the signal waveform obtained by differentiating this with the differentiating circuit 12, which is the part shown by the thick line in FIG. 4(B). At the moment when the receiving antenna 71 is switched to 72 between time t1 and time t12, the received signal strength in FIG. 4 (A) becomes (R, -R
), and the output waveform becomes discontinuous as shown in Figure 3 (B).
A negative impulse-like transient response occurs. This response gradually converges, or the time derivative d measured immediately after switching
R2' is the value obtained by adding the error for this transient response to the originally obtained time differential coefficient dR2, which will cause a large error in the average received signal strength M2 calculated by equation (1), making it difficult to select the correct receiving antenna. or become impossible.

This error increases as the received signal strength difference (R2-R,) increases.

Also, the longer the time from the switching time to the measurement time t2, the smaller the error becomes, so to reduce this error, t and t
Is it effective to increase the distance between 2 and 2? If the interval is too large, the time derivative dR, will change greatly by the reception start time t, and the time derivative dR, measured at time t1 will change by the reception start time t6. This is undesirable because the average received signal strength M, estimated using the time differential coefficient dR, measured at time t, has a large error. Examples are shown below.

FIG. 5 shows a configuration diagram of the second embodiment. Components that are the same as those in FIG. 9 are designated by the same reference numerals, and their explanations will be omitted. 40 is a received signal strength difference measuring circuit, and 41 and 42 are subtracters. In this embodiment, a differentiating circuit is not used, and instead, the received signal strength is measured by the received signal strength difference measuring circuit 40.
The signal is measured once, and the average received signal strength is determined by the average value estimation circuit 10 using the difference between the two measured values instead of the time differential coefficient.

FIG. 6 shows a diagram for explaining the processing procedure of the second embodiment of the present invention. Similar to FIG. 2, FIG. 6(A) shows the frame structure of the received signal. For the own station, the timing circuit 77 sends a signal to the received signal strength difference measuring circuit 40 of FIG. R
2 is held in the sample hold circuit 13.

Immediately thereafter, the switch control circuit 78 switches the selection switch 73 to the other receiving antenna 72, and at time t4, the sample and hold circuit 14 holds the received signal strength R4 from the receiving antenna 72.

Next, the switch control circuit 78 returns the signal to the receiving antenna 71 at time 1. The received signal strength R by the receiving antenna 71 is
1 is held in the sample hold circuit 80 of the received signal strength measuring circuit 79.

Finally, the switch control circuit 78 switches to the reception antenna 72, and the reception signal strength R2 is measured at the reception signal strength measurement circuit B7.
The sample hold circuit 81 of No. 9 holds the sample.

By the above method, four received signal strengths R, , R2, R3, R, shown in FIG. 6(B) are obtained.

Furthermore, a received signal strength difference measuring circuit 40 and a subtracter 41.
Using 42, the received signal strength difference value △R, (=R, -R,), △R, , = (R, = R,
) is calculated.

The average value estimation circuit IO has four parameters R, , R2,
Using △R3 and △R2, the average received signal strength M, , M of each receiving antenna at the reception time of the signal burst is calculated for the local station.
, is estimated using the following formula.

However, t is the signal burst reception start time for the own station, t
, is the end time of the signal burst toward the local station. Formula (2)
Estimating the average received signal strength M1, Ml by the sixth
As shown in Figure (C), the average received signal strength is Ml < Ml
becomes. This information is conveyed to the switch control circuit 78,
If the receiving antenna 71Sb is designated as the receiving antenna 72 at a in FIG. 4D, the switch control circuit 78 selects the receiving antenna 72 as shown in FIG. As a result, the signal strength toward the local station is maintained high when receiving the signal burst.

FIG. 7 shows a flowchart for explaining the operation of the average value estimation circuit 10 according to the second embodiment of the present invention. The received signal strength from each receiving antenna is measured twice by the received signal strength measurement circuit 79 to obtain R, , R2, R, , R, (step 700).
, the difference between the two measurements for each receiving antenna △R7, △
Calculate R2 (step 701).

From the parameters R, , R2, ΔR3, ΔR2, the average signal strength M, , Ml at the reception time is estimated by calculating the above equation (2) (step 702).

Average signal strength or Ml If Ml > Ml, receiving antenna 71
is selected and received (steps 703 and 704). If the average signal strength is not Ml>Ml, reception is performed using the receiving antenna 72 (steps 703 and 705). The received signal burst is terminated (step 706).

In addition, as a modified example, in the above, received signal strength R+, R
2, R-, R4 with four sample and hold circuits 80.8
1, I3.14, or use an A/D converter or register instead of the sample and hold circuit 80.81.13.14.

FIG. 8 shows a modification of the second embodiment. Components that are the same as those in FIG. 9 are designated by the same reference numerals, and their explanations will be omitted. 60 is an A/D converter, 61.62.63.64 is a register, 6
5 is a digital circuit, and 66 and 67 are digital subtracters.

The A/D converter 60 outputs 4 at times 1+, 11, tl, and t4.
Measurement is performed twice, and the measured values at this time are stored in four registers 61.
．． 62.63.64.

The received signal strength R3 is output from the register 61, R2 is output from the register 62, and the received signal strength difference ΔR2, ΔR2
is calculated by digital subtracters 66 and 67. As a result, from the digital circuit 65 corresponding to the received signal strength difference measuring circuit 40 and the received signal strength measuring circuit 79 in FIG.
,, R,, △R+, △R2 are output as digital values, so calculate the average received signal strength M I, M 2 using the same method as Equation (2) in the second embodiment, and select the highest value. You can select either receiving antenna. In this case, R, , R2, ΔR1, and ΔR2 are input to the average value estimation circuit 10 as digital values quantized with a certain number of bits n. For example, a ROM with a 4n-bit address input terminal is used as the average value estimation circuit IO, and the average received signal strength M l, M ! corresponding to these input values is calculated. The average value estimation circuit 10 can be realized with one ROM if the results of calculating the magnitudes and comparing the values are written in the ROM in advance. Received signal strength R,, R2, R,, R4 and average received signal strength M, , M
, can be performed entirely by digital circuits, making it easy to integrate into an IC.

Further, the functions of the digital subtracters 65 and 66 in FIG. 8 can also be included in the average value estimation circuit 10. In this case, the average value estimation circuit lO has Rr, Rt, Rs,
R4 is input, and the average value estimation circuit calculates the formula (
2), the average received signal strength M, ,M, is compared. For example, the received signal strength R, each expressed by a certain number of bits n,
, R, , R, , R, are input to a ROM with a 4n-bit address input terminal, and the values of the average received signal strength M, , M, corresponding to these inputs are calculated in advance and the results are compared in magnitude. If written in the ROM, the average value estimation circuit 10
is one R including the functions of digital subtracters 66 and 67.
Realize it with OM.

In addition, in the 2 first embodiment, the second embodiment, and the modified example, 2
Although we have discussed the configuration in which one of three receiving antennas is selected, is it possible to implement the present invention or can similar effects be obtained when one is selected from three or more receiving antennas? I can make an analogy.

For the first embodiment, the received signal strength for each receiving antenna is calculated from the time differential coefficient of each received signal strength using equation (1).
The calculation in (2) may be performed for each receiving antenna, and the receiving antenna estimated to have the highest average signal strength may be selected.

For the second embodiment, the received signal strength for each receiving antenna was measured twice, and the received signal strength for each receiving antenna was measured twice.
This can be achieved by calculating equation (2) for each receiving antenna from the difference between the measured values and the received signal strength for each receiving antenna, and selecting the receiving antenna that is estimated to have the highest average signal strength.

The present invention can also be applied to the FDM method by replacing all signal bursts in one frame in FIG. 2(A) with bursts for the own station and setting the measurement time in a free time.

For example, it is useful for reducing the size, power consumption, and cost of radio equipment.

〔Effect of the invention〕

As described above, according to the present invention, by selecting the correct receiving antenna, it is possible to perform antenna selection diversity reception in which a diversity effect can be obtained even when the fading rate is high. In the conventional antenna selection diversity borrowing method, the diversity effect could only be obtained at a fading speed slow enough to be carried around by a person, so the applicable range was limited, but according to the present invention, it can be used in low-speed automobiles, etc. Since a diversity effect can also be obtained in this case, it can be used in more mobile communication devices, and the receiving ability of the communication devices can be significantly improved.

In addition, by applying the antenna selection diversity reception method of the present invention, mobile communication equipment, which conventionally used two receivers to improve reception capability through post-detection selection diversity reception, can now be configured with one receiver.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a diagram explaining the processing procedure of the first embodiment of the present invention, and FIG. 3 is an average value estimation circuit of the first embodiment of the present invention. 4 is a diagram showing the influence of the transient response of the differential circuit in the first embodiment of the present invention, FIG. 5 is a block diagram of the second embodiment of the present invention, and FIG. 6 is a diagram showing the influence of the transient response of the differential circuit in the first embodiment of the present invention. FIG. 7 is a flowchart for explaining the operation of the average value estimation circuit of the second embodiment of the present invention, and FIG. 8 is a diagram showing a modification of the second embodiment of the present invention. FIG. 9 is a block diagram of the conventional method, FIG. 10 is a diagram for explaining the processing procedure of the conventional method, and FIG. 11 is a diagram for explaining the problems of the conventional method. 10... Average value estimation circuit, l]... Received signal strength differential coefficient measuring circuit, 12... Differentiation circuit, 13.14...
- Sample hold circuit, 40... Received signal strength difference measuring circuit, 41° - Subtractor, 71° - Receiving antenna, - Selection switch, - Receiving/demodulating section, - Timing circuit, - Switch control circuit.

Claims (2)

[Claims] (1) In the antenna selection diversity reception method in which one antenna is selected from multiple receiving antennas and reception is performed by connecting the selected receiving antenna to the receiver, the received signal strength received by each receiving antenna and each reception An antenna selection diversity reception method characterized by estimating the average signal strength of each receiving antenna at the reception time from the time differential coefficient of the signal strength, and selecting the antenna that obtains the largest average signal strength. (2) In the antenna selection diversity reception method, which selects one antenna from multiple receiving antennas and connects the selected receiving antenna to the receiver for reception, the received signal strength for each receiving antenna is measured twice. Then, the average signal strength of each receiving antenna at the reception time is estimated from the difference between the two measurements for each receiving antenna and the received signal strength for each receiving antenna, and the receiving antenna that obtains the largest average signal strength is selected. An antenna selection diversity reception method characterized by: