JP2007208658A - Diversity receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to receive a plurality of media commonly using antennas in a diversity receiver using a plurality of antennas. <P>SOLUTION: When a discriminating device discriminates that the receiving condition is good, an antenna system with the smallest absolute value of a cross-correlation value is specified as a control object antenna system out of absolute values of respective cross-correlation values, and a waiting factor for the control object antenna system is gradually reduced. Respective receiving signals of respective antennas are switched and branched to a first terminal side which receives a first media and is mainly used for diversity composition, and a second terminal side which receives a second media. When the waiting factor of the control object antenna system becomes smaller than a predetermined value, the receiving signal is passed to the second terminal side. When the discriminating device discriminates that the receiving condition is poor, the receiving signal of the control object antenna system is passed to the first terminal side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a diversity receiver, and more particularly, to a receiver capable of receiving different media using a common antenna group. The present invention is effective for use in mobile communication.

Conventionally, in mobile communication, as shown in Patent Document 1 below, a signal received by each antenna is diversity-combined by maximum ratio combining or equal gain combining using a plurality of antennas to receive a signal with high quality. The device is known.
On the other hand, when a broadcast signal is received in a mobile body such as a car, for example, it may be desired to receive traffic information such as FMVICS irregularly in addition to receiving a TV signal. Usually, when broadcasting media are different, dedicated antennas are used.

Japanese Patent No. 3696013

However, broadcast signals such as FMVICS need not always be received, and it is sufficient if they can be received intermittently. Even in such a case, it is necessary to install an antenna dedicated to the system, which causes waste in using the equipment.
Accordingly, the present invention has been made to solve such a problem, and paying attention to the fact that the diversity receiving apparatus uses a plurality of antennas and the reception strength of the reception signal of the main first medium. An object of the present invention is to improve facility utilization efficiency by enabling reception without providing a dedicated antenna for receiving the second media.

  In order to solve the above-mentioned problem, according to the means of claim 1, each received signal received by a plurality of antennas is synthesized by weighted addition with each weighting factor, and the combined signal and each received signal of each antenna In a diversity receiver that calculates each weighting coefficient based on each cross-correlation value between the two and synthesizes each received signal, a determination device that determines a reception state of the combined signal, and a reception device that has a good reception state If determined, the antenna system having the smallest absolute value of the cross-correlation value is identified as the control target antenna system from the absolute values of the cross-correlation values, and the weighting factor for the control target antenna system is gradually decreased. A weighting factor reduction device for receiving each received signal of each antenna or each weighted signal weighted by each weighting factor for main diversity combining for receiving the first medium A switching device for switching and branching the received signal to the second terminal side for receiving the other second media, and a weighting factor of the antenna system to be controlled controlled by the weighting factor reduction device. When it becomes smaller than the predetermined value, the switching device is controlled to pass the received signal to the second terminal side, and when the receiving device determines that the receiving state is bad by the determining device, It is a diversity receiver comprising a control device that passes each weighted signal weighted by each weighting factor to the first terminal side.

  In the present invention, the broadcast signal of the first medium is normally received by diversity combining. In this state, when it becomes necessary to receive the broadcast signal of the second medium, the receiving apparatus can receive the signal of the second medium while keeping the signal of the first medium in a receivable state. There are various methods for determining the reception state of the first media signal. When the power level of the combined signal is high, even if a certain antenna system is switched to the second terminal side, the S / N ratio of the combined signal is small and it may be determined that the signal can be received. For this purpose, there is a method of determining based on the magnitude of the sum of absolute values of cross-correlation values between each received signal and the combined signal. Furthermore, the controlled antenna system to be switched to the second terminal side can be specified as the system having the smallest cross-correlation value among the absolute values of the cross-correlation values between the received signals and the combined signal. . Since the absolute value of the cross-correlation value is related to the power and S / N ratio of each received signal, even when a system having the smallest power and S / N ratio of each received signal is selected, This is equivalent to selecting a system having a small absolute value of the cross-correlation value with the synthesized signal, and is included in the present invention. In addition, when the antenna system to be controlled is specified, if the weighting coefficient of the system is abruptly switched and the quality of the diversity combined signal is reduced, the weighting coefficient of the system is gradually decreased, The controlled antenna system is switched to the second terminal side.

  The reception state may be determined by the magnitude of the sum of absolute values of cross-correlation values of systems other than the control target antenna system (claim 2). Also, when considering mobile communication, the reception state of each antenna changes every moment. Therefore, when the antenna to be controlled is specified and the weighting coefficient of the system is gradually decreasing, when the antenna having the worst reception state changes, or in diversity combining of received signals by the remaining antennas, The signal may change to a state where it cannot be received. In the former case, before the control target antenna system is switched to the second terminal side, another antenna system is selected as a new control target antenna system. In the latter case, the selected antenna system to be controlled is restored in order to diversity combine the signal of the first media before the selection is canceled and the second antenna is switched to the second terminal side. Therefore, the weighting factor of the antenna system other than the antenna system to be controlled is caused to act so as to gradually increase toward the weighting coefficient determined based on the cross-correlation value between the received signal and the combined signal of that system. (Claim 3). The maximum value of the weighting factor is a weighting factor that is determined based on the cross-correlation value during a period of normal diversity combining without performing the above-described reduction operation on the weighting factor. Moreover, it is desirable to combine the diversity of the signal switched to the second terminal side (claim 4). For example, if a plurality of antenna systems to be switched to the second terminal side exist when a plurality of antenna systems to be controlled are allowed to be selected, the received signal of each antenna is diversity-combined, so that the signal of the second media is obtained. On the other hand, it is possible to receive with high quality.

The present invention provides an absolute value of a cross-correlation value with respect to a composite signal when a signal of the first media is received and demodulation of the signal with high quality is possible even if the number of reception antennas is reduced. Can be switched in order to demodulate the signal of the second media.
As a result, in a diversity receiver using the same antenna group, when the reception state of the first medium is good, signals of a plurality of media can be demodulated. Therefore, the equipment utilization efficiency of the receiving device is improved. Also, the weighting factor of the control target antenna system is gradually decreased from the time when it is specified as the control target, and when the control target antenna system becomes smaller than a predetermined value, the control target antenna system is switched to the second terminal side. ing. Therefore, the receiving state of the first medium is not impaired at the time of switching.

  Whether or not the reception state of the first medium is good is determined as good when the sum of absolute values of cross-correlation values other than the antenna system to be controlled is larger than a predetermined value, and is smaller than the predetermined value. By determining the failure, it is possible to accurately predict a good reception state even if the controlled antenna system is disconnected from the diversity combining of the first medium. For this reason, at the time of switching, the reception state of the first medium is not deteriorated (claim 2).

In addition, the weighting factor of the system other than the antenna system to be controlled is caused to gradually increase toward the weighting coefficient determined based on the cross-correlation value between the received signal and the combined signal of the system. Since the weight coefficient does not change suddenly when the antenna system to be controlled returns to diversity combining of the first medium after the antenna system to be controlled is specified, the reception state of the first medium can be maintained well. 3). Of course, when the weighting factor of the system is a weighting factor determined based on the cross-correlation value by a normal method, the value becomes that value, and there is no gradual increase operation of the weighting factor.
Also, the second medium can be demodulated with high quality by diversity combining the received signal of the antenna system switched to the second terminal side.

  Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.

  FIG. 1 is a logical system configuration diagram of the diversity receiver 1 according to the first embodiment. In this embodiment, n antennas A1 to An (2 ≦ n) are used. Frequency converters (tuners) 11 to 1n are connected to the antennas A1 to An. For example, if the first medium is a TV signal, a signal of a predetermined channel to be selected is converted into an intermediate frequency band. In the present embodiment, processing is performed with the signal converted into the intermediate frequency band. In the present embodiment, since the apparatus is based on digital processing, the high frequency signals received by the antennas A1 to An are sampled at a frequency corresponding to the frequency of the station to be selected, and converted to the intermediate frequency band. The digital signal is obtained. In addition, after sampling a high frequency signal and obtaining a digital signal, it is converted into an intermediate frequency band by digital processing. Alternatively, the high frequency signal is once converted into an intermediate frequency band by an analog circuit, and the intermediate frequency band The signal may be sampled and converted to a digital signal. Further, the processing in this embodiment may be performed after conversion to a baseband (a majority carrier group in the case of OFDM) signal. Note that the signal is a complex signal composed of two signal components, ie, a real part and an imaginary part after quadrature demodulation.

  Further, the part that processes with digital values can be realized by a computer system. In this embodiment, the analog signal is converted into an intermediate frequency band and then sampled to obtain a digital signal. Therefore, the signal control unit 10 in FIG. 1 is all realized by a computer system. The demodulator 51 is a device that converts the sampled digital signal in the intermediate frequency band into an OFDM baseband signal, and then extracts and decodes the amplitude phase information of each subcarrier by FFT. The demodulator 52 is a device that performs demodulation corresponding to the second medium.

The output signals of the frequency converters 11 to 1n are output to the switching devices 21 to 2n, and the a contact side (first terminal side) of the switching device is connected to the complex multipliers 31 to 3n. The outputs of the complex multipliers 31 to 3n are input to the synthesizer 40 and synthesized. Further, the combined output signal of the combiner 40 is input to the correlation calculation device 41, and the mutual complex correlation integral value with the received signals R _{1 to} R _{n of} each antenna system is calculated. Each cross complex correlation integral value calculated by the correlation calculation device 41 is output to the weight coefficient calculation device 42, and the complex weight coefficient of each antenna system is calculated. As a method for calculating the weighting factor, the method described in Patent Document 1 can be used.

Each signal R ₁ which is received by each antenna _{A1~An, R 2, ..., R} n is, by the respective complex multipliers 31 to 3n, the complex weight coefficients _{W 1, W 2, ...,} W n are multiplied Are output to the combiner 40. Therefore, the combined signal S output from the combiner 40 is
(Equation 1)
S = W ₁ R ₁ + W ₂ R ₂ +... + W _n R _n
It becomes.

Next, the correlation calculation device 41 calculates a complex weight coefficient W _i (1) at the next timing according to the following equation. A complex conjugate is indicated by * on the right shoulder. That is, the weight coefficient is calculated as a function of the cross correlation value.
(Equation 2)
W _i (1) = f (X _i (1))
(Equation 3)
X _i (1) = ∫R _i S ^* dt
The function f is arbitrary, but the moving average of the cross-correlation values (interpolation value of the cross-correlation values at different two time points by the forgetting factor α), the normalized cross-correlation value (cross correlation of a certain system Any function can be selected, such as value / sum of absolute values of cross-correlation values of each system). Although the integration interval is arbitrary, it is not shown, but the integration shows a definite integration. That is, the complex weight coefficient of the received signal having a large absolute value of the cross-correlation value with the synthesized signal S is increased. In this way, using the obtained complex weight coefficient W _i (1), the synthesized signal S at the next timing is obtained by Equation 1. Then, the complex weight coefficients W ₁ (2), W ₂ (2), R _n for the received signals R ₁ , R ₂ ,. .., W _n (2) is calculated by successively feeding back the time.

  As a result, only the received signal having a high correlation with the synthesized signal S is selected, and the received signal having a low correlation is excluded. In this way, it is possible to diversity combine only the desired received signal. When performing the correlation calculation of Equation 3, slide each received signal on the time axis to determine the slide time with the highest correlation value, and slide the received signal by this slide time. You may make it synthesize | combine. That is, the reception quality can be further improved by performing the combination that gives the highest correlation by taking the sliding correlation. For example, when a delayed wave is strongly received in a certain antenna, reception with higher reception quality becomes possible by causing the delayed wave to contribute to the synthesized signal for that antenna.

  In this embodiment, in such diversity combining, the reception quality is sufficiently high even if the remaining n-1 reception signals are combined without combining the reception signal having the smallest absolute value of the cross-correlation value of Equation (3). It can be expensive. In such a case, when there is a request for receiving the second medium, a signal received by this antenna is used for receiving the second medium. For example, an FMVICS broadcast signal can be considered as the second medium. This FMVICS does not need to be constantly received when the vehicle is running, and it is sufficient if it can be received intermittently. Therefore, in this embodiment, the FMVICS is received when the first medium is in a good reception state. It ’s fine. Further, when the reception quality due to the synthesis of the remaining n-1 reception signals is deteriorated, the reception of the second medium is interrupted again, and only the first medium is combined by diversity using all n reception signals. I am doing so.

  Whether or not the reception quality is high even in the synthesis of n−1 received signals is determined by whether or not the received signal having the smallest absolute value of the cross-correlation value of Equation 3 is the cross-correlation value of Equation 3 of the n−1 received signals. It is determined whether or not the sum of the absolute values is greater than a predetermined value L.

  In addition, when switching the synthesis of the received signal, even if the complex weight coefficient of the received signal to be cut is gradually reduced so that the synthesized signal is not discontinuously changed, the effect on the synthesized signal is sufficient. In this state, the received signal is disconnected without being synthesized. The most desirable state is that the complex weight coefficient is set to zero and then cut.

Next, the operation procedure of the signal control unit 10 (computer system) will be described with reference to the flowchart of FIG.
In step 100, the adjustment coefficient β _i for the received signals of all antenna elements is initialized to 1. The received signal R _i is multiplied by β _i W _i as a weighting factor. Hereinafter, β _i W _i is referred to as an adjusted weighting factor. Incidentally, the weighting coefficient in the claims, refers to the adjusted weighting coefficients used for generating the real composite signal beta _i W _i.

Therefore, the composite signal S is given by the following equation.
(Equation 4)
S = β ₁ W ₁ R ₁ + β ₂ W ₂ R ₂ +... + Β _n W _n R _n

When normal diversity combining is performed with n antennas, all adjustment coefficients β _i are 1. Next, in step 102, the cross-correlation value X _{i according} to Equation 3, the weighting factor W _{i according} to Equation 2, and the adjusted weighting factor β _{i Wi} are calculated, and the adjusted weighting factor β according to Equation 4 is calculated. Diversity combining is performed by performing a weighted addition operation on each received signal R _i using _i W _i .

Next, the control target antenna system j giving the minimum value is determined from the absolute values | X ₁ | to | X _n | of the _n complex correlation values. The absolute value of the adjusted weighting coefficients of the antenna system j and T _min.
Also, let V be the sum of absolute values of n cross-correlation values.
(Equation 5)
V = | X ₁ | + | X ₂ | + ... + | X _n |
It becomes.

Next, in step 106, a value (V−T _min ) obtained by subtracting the minimum value T _min (= | X _j |) from the sum V of the absolute values of the n cross-correlation values is calculated. It is determined whether or not the value is greater than a predetermined value L. That is, the absolute value of the n-1 cross-correlation values indicates whether sufficient reception quality can be obtained even if the antenna system j to be controlled is disconnected and diversity combining is performed using the remaining n-1 antennas. Judged by the sum of

If it is determined that V−T _min > L, in step 108, the adjustment coefficient β _j of the antenna system j to be controlled to be switched to the second terminal b side is decreased by 0.1. Further, the adjustment coefficient β _i of the remaining n−1 systems is increased by 0.1. However, the maximum value of β _i is 1, and the minimum value of β _j is 0.

Next, at step 110, it is determined whether or not the absolute value | β _j W _j | of the adjusted weighting factor of the controlled antenna system j to be switched to the second terminal b side is smaller than a predetermined value Δ. If it is not smaller than the predetermined value, the process returns to step 102 and diversity combining is performed at the next timing. Then, Steps 102 to 110 are repeated, and the adjustment coefficient β _j is decreased by the operation of Step 108, and the condition of Step 110 is satisfied. During this loop, when a new antenna system is determined in step 104, the antenna system changes to become the control target antenna system j, and the process of gradually reducing the adjustment coefficient in step 108 is executed. As for the adjustment coefficient for, a gradual increase process is executed. That is, the adjustment coefficient of the previous antenna system to be controlled is no longer the object of control this time, and the adjustment coefficient gradually increases.
In such a loop of steps 102 to 110, when the absolute value | β _j W _j | of the adjusted weighting factor of the antenna system to be controlled becomes smaller than the predetermined value Δ in step 110, the next step 112 is executed. Is done. If this value is smaller than the predetermined value, it is determined that even if the control target antenna system j is disconnected from the diversity combining, there is little influence on the combining. In step 112, the weighting factor W _j of the control target antenna system j is determined. Is 0, and the adjustment coefficient β _j is 0. Next, in step 114, the switch 2j is operated to the second terminal b side to disconnect the control target antenna system j from the diversity combining.

Next, the routine proceeds to step 116 where _{VT min} > L is determined. When step 116 is first executed, T _min = 0 since the antenna system j is disconnected. Therefore, the determination in step 116 is a determination as to whether or not the sum of the absolute values of the cross-correlation values in the n−1 received signals is larger than the predetermined value L. Diversity combining of Equation 4 is performed on n-1 antenna systems excluding the target antenna system j. Then, the process proceeds to step 120, where the adjustment coefficient β _i of the antenna elements involved in diversity combining is increased by 0.1, and at the next timing, the complex cross-correlation value X _i and the expression 2 Thus, the complex weight coefficient W _i is calculated. The maximum value of the adjustment coefficient β _i is 1. Then, Steps 116 to 120 are repeatedly executed. That is, when the adjustment coefficient β _i gradually increases to 1 and becomes 1 and the fluctuation disappears, a period in which diversity combining by n−1 antennas is good with all adjustment coefficients β _i being 1 , Diversity combining by the received signals of n−1 antennas is continuously performed in step 118.

On the other hand, if _{VT min} > L is not satisfied in step 116, it means that the reception state due to diversity combining by n-1 antennas has deteriorated. Therefore, the process proceeds to step 122, the switching device 2j is switched to the first terminal a side, and the controlled antenna system j is connected to the diversity combining side. Then, the process proceeds to step 124, and all adjustment coefficients β _i are increased by 0.1. However, the maximum value is 1. Then, the process returns to step 102 and returns to diversity combining using n antennas.

In this way, it is determined that good reception is possible by separating the antenna to be controlled having the smallest absolute value | X _j | of the cross-correlation value from diversity combining and diversity combining using the remaining n−1 antenna elements. In the case of the diversity combining, diversity combining is performed by the n-1 antenna elements. The separated control target antenna system j is connected to a demodulator 52 for another second medium, and is demodulated thereby, so that the second medium can be received.

Note that the number of antenna systems to be separated may be one or more. One or more may correspond to other plural media. The determination device in the claims is realized in steps 106 and 116, the weight coefficient reduction device is realized in steps 104 and 108, and the switching device is realized in the switches 21 to 2n and steps 114 and 122. The control device is realized in steps 110, 114, 116 and 122. The synthesizer 40 in FIG. 1 includes steps 102 and 118. The complex multipliers 31 to 3n, the correlation calculation device 41, and the weight coefficient calculation device 42 are respectively calculated by β _i W _i R _i , calculation by equation 3, calculation of equation 2 and β _i W _i , which are processing procedures by a computer. It is realized by.

  FIG. 3 is a block diagram illustrating the configuration of the diversity receiver 2 according to the second embodiment. The same components as in Example 1 are given the same numbers. In this case, when the control target antenna system to be disconnected is 1 or more, and two or more control target antenna systems are disconnected, diversity combining is performed on a plurality of received signals of the disconnected antenna systems. It is. Therefore, two types of diversity combining are executed for each received signal of each antenna. In other words, the signal control unit 20 has another diversity combining system including a complex multiplier 301 to 30n, a combiner 401, a weighting factor calculation device 421, and a correlation calculation device 411. Then, a complex cross-correlation value between the output signal of the synthesizer 401 and the reception signal of each antenna is calculated to determine a weighting factor. With this configuration, diversity combining can be performed for reception of other second media. In this case, in the first diversity combining system of the first first medium, the antenna system is sequentially disconnected from the adjusted antenna system having a smaller weighting factor as long as the reception quality does not deteriorate. The antenna system is connected to the diversity reception system of another second medium. If the reception state of the first diversity combining system is lowered, the antenna system of the second diversity combining system is sequentially switched to the first diversity combining system.

  FIG. 4 is characterized in that the signal after the weighting factor is weighted is switched from the first diversity combining system to the second diversity combining system with respect to the second embodiment of FIG. The same components as those in Example 2 are denoted by the same reference numerals. The signal control unit 30 has two systems, a system that demodulates the received signal of the first medium and a system that demodulates the received signal of the second medium. Similar to the first and second embodiments, the correlation calculation device 402 and the weight coefficient calculation device 42 calculate the complex cross-correlation value between the combined signal output from the combiner 40 and each received signal, and calculate each weight coefficient. . The system of the second media combines the output of the antenna system switched by the switchers 201 to 20n among the outputs of the complex multipliers 31 to 3n by the combiner 402. Correlation calculation unit 402 receives the composite signal of the first media system and the composite signal of the second media system, calculates the complex cross-correlation value for each received signal of each system, and outputs the first A weight coefficient for each received signal of the media system and the second media system is calculated. According to this configuration, only one correlation calculation device, weight coefficient calculation device, and complex multiplier are required. The weighting factor is calculated independently for each of the signals belonging to the first diversity combining system and the signals belonging to the second diversity combining system.

  The present invention can receive a plurality of media by a diversity receiver having the same antenna group, and is effective for mobile communication.

1 is a block diagram showing the configuration of an apparatus according to a specific embodiment 1 of the present invention. The flowchart which showed the operating characteristic of the signal control part of the Example apparatus. The block diagram which showed the structure of the apparatus of the specific Example 2 of this invention. The block diagram which showed the structure of the apparatus of the specific Example 3 of this invention.

Explanation of symbols

1, 2, 3 ... Diversity receivers A1 to An ... Antennas 11 to 1n ... Frequency converters 21 to 2n ... Switches 31 to 3n, 301 to 30n ... Complex multipliers 40, 401 ... Synthesizer 41 ... Correlation arithmetic unit 42 , 402... Weight coefficient computing device 200... Diversity receiving device (first embodiment)
300: Diversity receiver (second embodiment)
400: Diversity receiver (third embodiment)

Claims (4)

Each received signal received by a plurality of antennas is combined by weighting and adding each weighting factor, and each weighting factor is calculated based on each cross-correlation value between the combined signal and each received signal of each antenna. In the diversity receiver that combines the received signals,
A determination device for determining a reception state of the combined signal;
When the determination device determines that the reception state is good, the antenna system having the smallest absolute value of the cross-correlation value is identified as the control target antenna system from among the absolute values of the cross-correlation values, and the control is performed. A weighting factor reducing device that gradually reduces the weighting factor for the target antenna system;
Each received signal of each antenna or each weighted signal weighted by each weighting factor is used for main diversity combining to receive the first medium, and the received signal is received by another second medium. A switching device for switching to the two-terminal side and branching;
When the weighting factor of the controlled antenna system controlled by the weighting factor reducing device is smaller than a predetermined value, the switching device is controlled to pass the received signal to the second terminal side, When the determination device determines that the reception state is poor, the control device that passes the weighted signal weighted by the received signal or the weighting factor of the antenna system to be controlled to the first terminal side,
Diversity receiver comprising: The determination device determines that the reception state is good when the sum of absolute values of cross-correlation values other than the antenna system to be controlled is larger than a predetermined value, and determines that the reception state is bad when the sum is smaller than the predetermined value. The diversity receiver according to claim 1, wherein the determination is performed. The control device gradually increases a weighting factor related to each received signal other than the controlled antenna system toward a weighting factor determined based on a cross-correlation value between the received signal and the combined signal. The diversity receiver according to claim 1 or 2. The diversity receiving apparatus according to claim 1, further comprising a second diversity combining apparatus that performs diversity combining on a reception signal branched to the second terminal side.

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