JP2001086091A - Digital broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large-scale circuit and increase the number of branches because OFDM demodulation is performed on signals received by a plurality of antennas and optimum data is synthesized for each sub-channel. However, there is a problem that power consumption increases with the above. SOLUTION: A signal received by a plurality of antennas is
An OFDM receiver that improves the characteristics of a received signal without increasing hardware complexity by performing processing and combining before FDM demodulation is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiving apparatus, and more particularly to a digital broadcast receiving apparatus which can be suitably used in a poor reception environment such as mobile reception and portable reception.

[0002]

2. Description of the Related Art In terrestrial digital broadcasting, SFN (Singing) is used.
le Frequency Network), MFN
(Multi Frequency Network)
Digitization is being performed to realize effective use of bandwidth and bandwidth. According to this, it is possible to broadcast one program for HDTV and three programs for SDTV using a 6 MHz area. At the same time, high-quality sound broadcasting and data broadcasting will be realized.

In digital broadcasting, video / audio information is converted to MPE
The transport stream (TS) is generated by multiplexing the compressed video, audio information, and data broadcasts according to the G2 method. The generated TS signal is transmitted by a digital modulation method.

[0004] In the case of terrestrial digital broadcasting, COFDM (Coded Orthogonal) is used as a transmission system in Europe.
Frequency Division Multi
plexing) and BST-OFDM (Ban
d SegmentedTransmission-
Orthogonal Frequency Divi
A zone multiplexing system is adopted, and both are based on an orthogonal frequency division multiplexing system (OFDM system). The OFDM system is a multi-carrier transmission system using a plurality of carriers at the same time. Each carrier is orthogonal to each other, and DQPSK, Q
It is modulated by PSK, 16QAM, 64QAM.
Do you use about 1,400 carriers for digital terrestrial broadcasting in Japan? 5600 lines, OFDM modulation and OFDM
Demodulation is performed by inverse Fourier transform and Fourier transform, respectively.

In actual transmitters and receivers, an I-DFT (Inverse-D) of 2K to 8K points is used.
iscree Fourier Transform
) process, DFT (Discrete Fou)
rior Transformation) processing.

In terrestrial digital broadcasting, unlike satellite broadcasting, radio waves are emitted horizontally from a transmitting tower, so that reflected waves are generated by obstacles such as buildings and mountains, and the reflected waves are ghosts, causing errors in digitally modulated signals. In this case, the video and audio signals are broken, and the reception quality is significantly degraded. Signal degradation due to noise can be corrected by error correction, and the receiver can reproduce video / audio without error.

As described above, a buffer region is provided in the OFDM system in order to absorb the influence of interference due to ghosts and multipaths, so that even if a delay wave is present, the corruption of information is not caused. This buffer area is called a guard interval. If the delay time of the delay wave of the received signal does not exceed the time of the guard interval, no intersymbol interference occurs, so that the error can be corrected by the error correction circuit. The guard interval signal is 1 /
4, 1/8, 1/16, and 1/32, which correspond to about 8 microseconds to 250 microseconds.

In general, in mobile reception in terrestrial broadcasting, selective fading occurs due to multipath fading, and a digitally modulated signal is extremely deteriorated, causing information errors. In digital broadcasting, such errors are reduced by adopting the BST-OFDM scheme, and mobile reception is being attempted.

In particular, this method can correct a degraded signal by interleaving, convolutional code and error correction even when selective fading occurs.

However, under multipath fading with extremely slow selectivity and very slow time variation, there are cases where the signal cannot be corrected even if the above method is used.

In order to cope with such poor transmission paths, antenna diversity using a plurality of receiving antennas has been proposed. FIG. 2 shows a diversity reception system using two conventional antennas.

According to this method, a radio wave transmitted from a broadcasting station is received by two antennas 11a and 11b,
A desired frequency is selected in 3a and 3b. Selected IF
The signals or baseband signals are converted to digital signals by analog-to-digital converters (ADCs) 14a, b. The digitized signal is output to the OFDM demodulator 17
The signals are demodulated by a and b and decoded by the decoders 18a and 18b.

The error rate calculator 26 calculates the error rate from the signal received and demodulated in each branch, and sends a control signal to the selection circuit 27 so as to select a branch with a small number of errors. The signal decoded by the decoders 18a and 18b is selected by the selection circuit 27 from the one with less error, and a TS signal is output.

As described above, by selecting a branch having a small number of errors from the demodulated signal, stable reception can be performed even when the radio wave environment is not good such as mobile reception.

However, the above-mentioned diversity receiving method has a disadvantage that the OFDM demodulation processing is required in each branch, and the receiving system becomes complicated.
Also, as the number of branches increases, the size of the system increases, and the power consumption also increases.

[0016]

As described above, multipath fading occurs in mobile reception, resulting in transmission path characteristics accompanied by selective fading, and the frequency characteristics of the transmission path deteriorate while fluctuating with time.

In the OFDM system, data is divided into subcarriers, and error correction and interleaving are performed by encoding, so that errors in received data can be corrected even if transmission characteristics deteriorate due to multipath delay waves.

However, there is a problem in mobile reception that the environment where direct waves cannot be received and the reception electric field are reduced. or,
In order to solve such a problem, antenna diversity for receiving signals with a plurality of antennas has been proposed, which is compatible with multipath fading.

FIG. 2 shows a configuration diagram of a conventional space diversity system that receives an OFDM reception signal.

The signal received by the receiving antenna 11a is transmitted to a tuner 23a for channel selection and an analog-digital converter (A
DC) 14a. The received signal converted into a digital signal is OFDM-demodulated by the OFDM demodulation unit 24a, and is passed to the subsequent decoding unit 25a. The decoding unit 25a performs an inverse process of the encoding performed on the transmission side and outputs a signal. This output signal is passed to the selection circuit 27. Similarly, the signal received by the receiving antenna 11b is independently processed according to the same procedure as the above processing. The signal received and demodulated in each branch is selected by the selection circuit 27 so that data having the least error between subcarriers is selected.

However, as described above, in the conventional diversity, it is necessary to perform OFDM demodulation on signals received by a plurality of antennas and to synthesize optimum data for each sub-channel. That is, the number of OFDM demodulation units required is equal to the number of antennas (branches), and there is a disadvantage that the circuit becomes large-scale, and there is a problem that power consumption increases with an increase in the number of branches.

The present invention solves this problem by processing signals received by a plurality of antennas before OFDM demodulation and combining the signals, thereby improving the characteristics of the received signals without increasing the complexity of hardware. An OFDM receiver is provided.

[0023]

Means for Solving the Problems The present invention has the following configuration in order to solve the above problems.

That is, in a digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal by a plurality of antennas, the delay amount of each signal received by the plurality of antennas is represented by:
A plurality of variable delay means for changing by a separately input control signal, a plurality of tuning means for selecting the same station from the signal whose delay amount is controlled, and a single common means common to the plurality of tuning means. Local oscillation means, analog-to-digital conversion means for converting a signal tuned by the plurality of tuning means into a digital signal, coefficient calculating means for calculating a predetermined coefficient from the plurality of digital signals, Comprising a combining means for multiplying the digital signal by the predetermined coefficient to combine the signals, an orthogonal frequency division multiplexing signal demodulating means for demodulating the combined signal, and a decoding means for decoding the demodulated signal. I made it.

In a digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal by a plurality of antennas, a plurality of channel selecting means for selecting the same station from each signal received by the plurality of antennas, A single local oscillation means common to a plurality of tuning means, a plurality of variable delay means for changing respective delay amounts of the plurality of tuned signals by a separately input control signal, and a plurality of variable delay means; Analog-to-digital conversion means for converting a signal selected by the tuning means into a digital signal, coefficient calculation means for calculating a predetermined coefficient from the plurality of digital signals, and applying the predetermined coefficient to the plurality of digital signals. Combination means for multiplying and combining the signals, orthogonal frequency division multiplexing signal demodulation means for demodulating the combined signal, and decoding means for decoding the demodulated signal may be provided. .

Alternatively, in a digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal with a plurality of antennas, a plurality of channel selecting means for selecting the same station from respective signals received by the plurality of antennas; A single local oscillation means common to the plurality of tuning means, an analog / digital conversion means for converting a signal tuned by the plurality of tuning means into a digital signal, and a delay of each of the plurality of digital signals; A plurality of variable delay means for changing the amount by a separately input control signal; a coefficient calculating means for calculating a predetermined coefficient from the plurality of digital signals whose delay amount is controlled; and A combining means for multiplying the combined signal by a coefficient, an orthogonal frequency division multiplexing signal demodulating means for demodulating the combined signal, and a decoding means for decoding the demodulated signal. You may make it.

Here, it is preferable that the delay means controls a delay amount and / or a time during which the delay amount changes by a separately input control signal.

The coefficient calculating means may calculate a coefficient which maximizes the signal-to-noise ratio of the signal synthesized by the synthesizing means. May be calculated such that the signal powers of the signals are equal to each other, or a coefficient may be calculated such that only the signal having a large received power is selected from the signals synthesized by the synthesis unit. Further, a plurality of coefficient calculation units may be provided, and an arbitrary calculation result may be selected from the plurality of coefficient calculation results.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of a digital broadcast receiver according to the present invention will be described. In the present invention, broadcast waves are independently received by N receiving antennas.

It is assumed that a multipath having L paths has arrived at each receiving antenna, and the complex amplitude of the l-th path arriving at the m-th receiving antenna is represented by

[0031]

(Equation 1) And

At this time, the received signal at the m-th receiving antenna (branch) is

[0033]

(Equation 2) Then the received signal is

[0034]

(Equation 3) Can be written. here

[0035]

(Equation 4) Is the white noise at the m-th receiving antenna.

The signals received by the respective antennas are multiplied by a weight coefficient and added. The received signal after addition

[0037]

(Equation 5) Then, it is expressed by the following equation.

[0038]

(Equation 6) Here, the weight coefficient of the m-th branch is

[0039]

(Equation 7) It is.

The receiver performs demodulation by performing DFT processing on the received signal. Therefore, the DFT output signal

[0041]

(Equation 8) Then, the received signal can be expressed by the following equation.

[0042]

(Equation 9) The weight vector w of the weight coefficient of each receiving antenna is

[0043]

(Equation 10) And

In the digital broadcast receiver according to the present invention, the received branch signals are combined before the DFT, and the weight coefficient is determined so as to maximize the SNR after the DFT.
That is, the covariance matrix of the received signal is obtained, and the eigenvector corresponding to the largest eigenvalue of the matrix may be set as the weight coefficient W.

Hereinafter, an embodiment of a digital broadcast receiver according to the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing a configuration of a diversity OFDM receiver system according to a first embodiment of the present invention. In this example, a two-branch (antenna) diversity receiving system is shown. However, it goes without saying that a system with more branches than this can be similarly applied.

The operation will be described below.

The signals received by the receiving antennas 11a and 11b are input to the tuners 13a and 13b as RF signals.
The tuners 13a and 13b select a desired channel and output an IF signal or a baseband signal. The output IF signal or baseband signal is output from the ADC 14
Sampled and quantized by a and b, and converted into a digital signal.

The digitized received signal is supplied to the synthesizing circuit 16.
, Are added and output to the demodulator. The OFDM demodulation unit 17 performs OFDM demodulation on the signal added by the combining circuit 16. In this example, a case where an IF signal is output from the output terminals of the tuners 13a and 13b will be described. A similar effect can be obtained with a baseband signal output.

The R received by the receiving antennas 11a and 11b
The F signal is passed through the variable tuners 12a and 12b to the receiving tuner 1.
3a and 3b. Here, the control unit 20 changes the delay time of each independently received signal to generate a received signal. The amount of change and the speed of change of the delay time of the control unit 20 are controlled by an external control signal input terminal 21.
Can be set by the input control signal.

Channels are selected by the receiving tuners 13a and 13b,
The signals converted into digital signals by C14a, b are
An optimum weighting coefficient for each branch is calculated by a coefficient calculating unit 15, combined by a combiner 16, the combined signal is demodulated by an OFDM demodulation unit 17, and the demodulated signal is subjected to complex processing by a decoding unit 18. And output the TS signal to output terminal 1
9 to output.

In the decoding section 18, the reverse processing of the processing on the transmission side is performed. That is, frequency deinterleaving, time deinterleaving, demapping, depuncturing, Viterbi decoding, Reed-Solomon decoding, despreading, and the like are performed, and a transport stream (TS signal) is output.

FIG. 4 is a block diagram of the synthesizer 16 shown in FIG.

In FIG. 4, the received signals converted into digital signals by the ADCs 14a and 14b are multiplied by weighting factors w1 and w2 by multipliers 41a and 41b inside the synthesizing unit 16, respectively.
The addition is performed by the adder 42. The weight coefficients w1 and w2 are coefficients obtained by the weight coefficient calculation unit 15 from the received signal.

The signal generated by the synthesizer 16 is O
Demodulated by the FDM demodulation unit. The demodulated signal is decoded by the decoding unit 18 at the subsequent stage and output from the output terminal 19.

FIG. 5 shows a block diagram of the OFDM demodulation unit 17 in FIG.

In FIG. 5, the output signals of the ADCs 14a and 14b are input as digital signals from the input terminal 51 of the OFDM demodulation section, demodulated by the IQ demodulation section 52, and converted into baseband signals. The guard interval removing circuit 53 removes the guard interval signal added on the transmitting side from the converted digital baseband signal.

The removed signal becomes only an effective symbol signal and is passed to the subsequent FFT processing circuit 54. Fast Fourier transform is performed by the FFT processing circuit 54, and the signal on the time axis is converted into a signal on the frequency axis. The converted signal is passed to a subsequent-stage waveform equalization circuit 55 for processing.
The equalized data is output from the data output terminal 56. The signal output from the output terminal 56 is passed to the decoding unit 18 in FIG. 1 and processed.

FIG. 6 shows the variable delay unit 12a,
It is a figure which shows the structure of the element of b.

The signal input from the input terminal 60 is
The signal is transmitted from the strip line 62 formed above the signal line 1 and output from the output terminal 63.

The variable delay units 12a and 12b are connected to the BST (Ba, S
An oxide of r, Ti) or a dielectric material 68 using liquid crystal is sandwiched between an upper electrode 66 and a lower electrode 67.
A control voltage is supplied from an external control circuit 64 to a voltage input terminal 65.
By giving the values from a and b, the permittivity of the dielectric element 68 is changed, and the signal transmission time of the variable delay units 12a and 12b is controlled. The element is formed on a substrate 69.

FIG. 7 shows the tuner section 13a in FIG.
It is a block diagram of b.

The signal received from the receiving antenna is input through input terminals 70a and 70b, amplified to predetermined levels by amplifiers 72a and 72b, and input to multipliers 73a and 73b.
The desired frequency is selected by multiplying the signal by a local signal from a distributor 78 for distributing the local signal for channel selection. The tuning local signal controls a PLL circuit according to a desired frequency specified by the tuning control unit 82 to generate a predetermined frequency. The output signals of the multipliers 73a and 73b
Only the desired frequency band is selected by 4a and 4b, and adjacent unnecessary signal components are removed and output. The selected signal is converted to an intermediate frequency (IF signal) by multipliers 75a and 75b at the subsequent stage.
Is converted to

A local signal for conversion to an intermediate frequency (IF signal) is generated by a signal source 81 and distributed by a distributor 79. The generated IF signal is amplified to an optimum level through amplifiers 76a and 76b and output from output terminals 77a and 77b.

FIG. 8 is a block diagram showing the configuration of the count calculation unit 15 in FIG.

The coefficient calculation unit 15 includes three types of calculation units, a maximum ratio synthesis calculation unit 103, a selection synthesis calculation unit 104, and a gain synthesis calculation unit 105, and inputs and outputs signals of these three types of calculation units. It comprises switching units 102 and 107 for switching, and a control unit 106 for controlling the switching units.

The calculation result of the most appropriate calculation unit is output from these three types of calculation units according to the reception state. It should be noted that this calculation unit may be further increased as necessary. The received signal of each branch is input from the input terminals 100a and 100b, and selects a coefficient calculation method according to the reception state.

FIG. 9 is a block diagram of the maximum ratio combining calculation unit 103 in FIG.

The covariance matrix of the signal selected by the selection unit 102 in FIG. As a result, an eigenvector for the largest eigenvalue of the matrix is obtained by the eigenvector calculation unit 92. The calculation result is output from output terminals 93a and 93b.

The output signal is supplied to the selector 10 in FIG.
7 through the coefficient input terminals 43a and 43b of FIG. 4 and passed to the multipliers 41a and 41b, and the input terminals 40a and 40b.
Is multiplied by the received signal.

FIG. 10 is a block diagram of the calculation section 104 for selective synthesis in FIG.

For the signal selected by the selection unit 102 in FIG. 8, the power calculation unit 112 calculates the power of each branch. The comparison circuit 113 at the subsequent stage selects a branch having the maximum power according to the calculation result of the power calculation unit 112, and at the same time, generates a coefficient so that the branch having the maximum power can be selected and outputs the coefficient from the output terminals 114a and 114b.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

The signals received by the antennas 11a and 11b are tuned by the receiving tuners 13a and 13b, and the tuned signals are delayed by the delay units 31a and 31b.
The signal converted into a digital signal by the
, The optimum weighting coefficient for each branch is calculated by the combiner 16, the combined signal is combined by the combiner 16, the combined signal is demodulated by the OFDM demodulation unit 17, the demodulated signal is subjected to the complex processing by the decoding unit 18, and The signal is output from the output terminal 19.

Here, the control unit 20 changes the delay time of each independently received signal to generate a received signal. The amount of change and the speed of change of the delay time of the control unit 20 can be set by a control signal input from an external control signal input terminal 21.

FIG. 11 is a block diagram showing a third embodiment of the present invention.

The signals received by the antennas 11a and 11b are tuned by the receiving tuners 13a and 13b,
The signals are input to a and b and converted into digital signals. The signals converted into digital signals are each independently delayed by a delay unit 121.
a, b. For the delayed signal, a coefficient calculating unit 15 calculates an optimal weight coefficient for each branch,
The synthesized signal is synthesized by the synthesizer 16, and the synthesized signal is
The demodulated signal is demodulated by the demodulation unit 17, and the demodulated signal is
Performs a composite process, and outputs a TS signal from an output terminal 19.

The delay time of the delay unit is controlled by a control unit 122, and the amount and speed of change of the delay time of the control unit 122 are set by a control signal input from an external control signal input terminal 21. Can be.

In the above description of the present invention, the number of reception branches is two. However, a configuration of three or more branches can be adopted, and the effect becomes larger as the number of branches increases.

[0080]

As described above, according to the receiving apparatus of the present invention, the hardware is not complicated as in the conventional antenna diversity, and the multipath fading that occurs during mobile reception is overcome.

The present invention is a means for very efficiently realizing high-speed mobile reception such as digital broadcasting and broadband communication, which is expected in the future, and can realize a small-sized and low-power-consumption receiving system.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital broadcast receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a conventional digital broadcast receiver.

FIG. 3 is a block diagram illustrating a configuration of a digital broadcast receiver according to another second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a combiner according to the present invention.

FIG. 5 is a block diagram illustrating a configuration of an OFDM demodulation unit according to the present invention.

FIG. 6 is a block diagram showing a configuration of a variable delay device according to the present invention.

FIG. 7 is a block diagram illustrating a configuration of a tuning unit according to the present invention.

FIG. 8 is a block diagram illustrating a configuration of a counting unit according to the present invention.

FIG. 9 is a block diagram showing a configuration of a maximum ratio combining circuit in the counting section according to the present invention.

FIG. 10 is a block diagram showing a configuration of a selective gain combining circuit in the counting section according to the present invention.

FIG. 11 is a block diagram illustrating a configuration of a digital broadcast receiver according to a third different embodiment of the present invention.

[Explanation of symbols]

 11a, b Receiving antennas 12a, b Variable delay devices 13a, b Tuners 14a, b ADC 15 Coefficient calculator 16 Synthesis unit 17 OFDM demodulation unit 18 Decoding unit 19 Output terminal 20 Delay control circuit 21 Control signal input terminal 22 Common oscillator (local oscillator) 23a, b Tuner 24a, b OFDM demodulation unit 25a, b decoding unit 26 Error rate calculation unit 27 selection circuit 28 output terminal 31a, b delay unit 34 output terminal 40a, b signal input terminal 41a, b multiplication Device 42 adder 43a, b coefficient input terminal 44 output terminal 51 signal input terminal 52 IQ demodulation circuit 53 guard interval removal circuit 54 FFT processing circuit 55 waveform equalization circuit 56 output terminal 57 synchronization processing circuit 60 signal input terminal 61 variable delay device 62 strip line 63 output terminal 6 Control circuit 65a, b Control voltage application terminal 66 Upper electrode 67 Lower electrode 68 Dielectric element 69 Substrate 70a, b Input terminal 72a, b Amplifier 73a, b First mixer 74a, b Filter 75a, b Second mixer 76a, b Amplifier 77a, b output terminal 78 distributor 79 distributor 80 PLL circuit 81 oscillator 82 tuning control unit 83 crystal oscillator 90a, b input terminal 91 covariance matrix 92 eigenvector calculation unit 93a, b output terminal 100a, b output terminal 101 control signal Input terminal 102 Selection circuit 1 103 Coefficient calculation circuit 1 104 Coefficient calculation circuit 2 105 Coefficient calculation circuit 3 106 Control unit 107 Selection circuit 2 108a, b Output terminals 110a, b Input terminal 112 Power calculation circuit 113 Comparison circuit 114a, b Output terminal 121a, b Delay device 12 2 control circuit 123 control terminal

Claims (7)

[Claims] 1. A digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal by a plurality of antennas, wherein a plurality of antennas receive signals of the plurality of antennas, and a delay amount of each signal is changed by a separately input control signal. Variable delay means; a plurality of tuning means for selecting the same station from the signal whose delay amount is controlled; a single local oscillation means common to the plurality of tuning means; and the plurality of tuning means Analog-to-digital conversion means for converting a signal selected by the means into a digital signal; coefficient calculating means for calculating a predetermined coefficient from the plurality of digital signals; and multiplying the plurality of digital signals by the predetermined coefficient. A digital device comprising: synthesizing means for synthesizing; orthogonal frequency division multiplexing signal demodulating means for demodulating the synthesized signal; and decoding means for decoding the demodulated signal. Broadcast receiver. 2. A digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal with a plurality of antennas, comprising: a plurality of channel selecting means for selecting the same station from respective signals received by the plurality of antennas; A single local oscillation means common to a plurality of tuning means; a plurality of variable delay means for changing a delay amount of each of the plurality of tuned signals by a separately input control signal; and Analog / digital conversion means for converting a signal selected by the tuning means into a digital signal; coefficient calculating means for calculating a predetermined coefficient from the plurality of digital signals; and applying the predetermined coefficient to the plurality of digital signals. Synthesizing means for multiplying and synthesizing; orthogonal frequency division multiplexing signal demodulating means for demodulating the synthesized signal; and decoding means for decoding the demodulated signal. Digital broadcast receiver. 3. A digital broadcast receiver for receiving an orthogonal frequency division multiplexed signal with a plurality of antennas, comprising: a plurality of channel selecting means for selecting the same station from respective signals received by the plurality of antennas; A single local oscillation means common to a plurality of tuning means; an analog / digital conversion means for converting a signal selected by the plurality of tuning means into a digital signal; and a delay of each of the plurality of digital signals A plurality of variable delay means for changing the amount by a separately input control signal; a coefficient calculating means for calculating a predetermined coefficient from the plurality of digital signals with the controlled delay amount; A combining means for multiplying the combined signal by a coefficient of the following, an orthogonal frequency division multiplexing signal demodulating means for demodulating the combined signal, and a decoding means for decoding the demodulated signal. A digital broadcast receiver, characterized in that: 4. The delay unit according to claim 1, wherein the delay unit controls a delay amount and / or a time during which the delay amount changes by a separately input control signal. Digital broadcast receiver. 5. The coefficient calculation unit according to claim 1, wherein the coefficient calculation unit calculates a coefficient that maximizes a signal-to-noise ratio of the signal synthesized by the synthesis unit. Digital broadcast receiver as described. 6. The apparatus according to claim 1, wherein said coefficient calculating means calculates a coefficient such that the signal powers of the signals synthesized by said synthesizing means are the same. Digital broadcast receiver. 7. The coefficient calculation unit according to claim 1, wherein the coefficient calculation unit calculates a coefficient that selects only a signal having a large received power from the signals synthesized by the synthesis unit. A digital broadcast receiver according to crab. 8. The apparatus according to claim 1, wherein said coefficient calculation means has a plurality of coefficient calculation units, and selects an arbitrary calculation result from said plurality of coefficient calculation results. Digital broadcast receiver as described.