JPH0993216A - Data transmitter and data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve more the quality of an OFDM modulation signal. SOLUTION: A signal point transmitter 14 allocates a signal point Zk ,l in a QPSK modulation circuit 18 to parallel data S100 inputted from an S/P conversion circuit 100 by changing an amplitude so as to compensate an aperture effect of a communication transmission line and each section after an IFFT circuit 104 onto a modulation signal S20. D/A converter circuits 1061 , 1062 and LPF circuits 1081 , 1082 convert complex number data zk ,m into analog form and eliminate an undesired harmonic component to generate transmission signals S1061 , S1062 . The QPSK modulation circuit 18 adopts the QPSK modulation system to generate a modulation signal S18 at an intermediate frequency band. A transmission circuit 20 converts the modulation signal S18 into a modulation signal S20 at a carrier frequency band of a communication transmission line to send it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compensates for an aperture effect given to a transmission signal inside a data transmission device,
The present invention relates to a data transmission device and a data transmission method having improved transmission characteristics.

[0002]

2. Description of the Related Art Conventionally, as a modulation method for transmitting digital data, for example, PSK (Phase Shift Keying) for changing the phase of a single carrier signal according to the value of data. ) Method and QAM (Quadrature Amplitude) that performs modulation by changing the phase and amplitude of the carrier signal according to the data value.
Modulation) method and other orthogonal modulation methods are often used.

Further, recently, as a new modulation method for transmitting digital data, an orthogonal frequency division multiplexing method (OFDM method) is used.
plexing) is proposed. In this OFDM system, a plurality of carrier signals included in a transmission frequency band are respectively modulated with a plurality of data having a relatively low data rate to generate a plurality of modulated signals, and these modulated signals are transmitted in parallel. It is a thing.

In the OFDM system, since the transmission frequency band is divided and used for a plurality of carrier signals, the transmission band per one modulated signal (carrier signal) becomes narrow,
The transmission data rate per modulated signal cannot be increased as compared with the QAM system and the like. But OFDM
Since the method can transmit multiple modulated signals in parallel, the transmission data rate of the entire transmission frequency band is QAM.
It can be made equivalent to the method.

Further, since the OFDM system has a low transmission data rate per one modulated signal, it is highly resistant to multipath ghost interference and is suitable for data transmission via a wireless communication line using terrestrial waves. It has attracted attention as a transmission system for new digital television broadcasting. In the OFDM system, a television broadcasting station is provided for each of a plurality of broadcasting areas, and these television broadcasting stations use radio signals of the same frequency to perform data distribution of digital television broadcasting to each broadcasting area. , SFN (Sing
(le Frequency Network) system has attracted attention as a transmission system that can be realized.

It is preferable that the modulation process and the demodulation process in the OFDM system are collectively performed by applying the fast Fourier transform process and the fast Fourier inverse transform process, respectively. The OFDM system is not always practical because it is difficult to realize a device that can perform conversion processing. However, with the recent improvement in digital signal processing technology, it has become possible to realize Fourier transform processing and inverse Fourier transform processing at high speed and in hardware. In other words, it becomes possible to collectively modulate each of a large number of carrier signals with a large number of transmission data and demodulate a large number of transmission data from each of a large number of modulation signals, making the OFDM system even more practical. , Is increasing.

Further, when generating a transmission signal of the OFDM system, it is necessary to perform digital / analog conversion on the transmission data subjected to the inverse fast Fourier transform.
The circuit that executes the analog conversion process usually has a predetermined frequency characteristic, and the generated transmission signal is given an aperture effect. As described above, when the transmission signal having the aperture effect is transmitted to the communication line by the digital / analog conversion process or on the communication transmission line, the error rate of the reproduced transmission data is increased.

Therefore, it is necessary to compensate the aperture effect given to the transmission signal before transmitting the transmission signal to the communication line. In order to compensate for the aperture effect, conventionally, a method of equalizing a transmission signal converted into an analog format by passing it through a filter having a predetermined frequency characteristic has been adopted. However, if the transmission signal is equalized and the aperture signal is equalized by a filter or the like, the circuit scale of the circuit for performing the equalization processing becomes large, which hinders downsizing and cost reduction of the transmission device, and also has an aperture effect. It was not always possible to fully compensate.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a data transmission apparatus and a data transmission method capable of further improving the quality of a modulation signal generated by the OFDM system. The purpose is to It is another object of the present invention to provide a data transmission device and a data transmission device that can reduce the data error rate of transmission data reproduced from a modulated signal that has passed through a communication line.

It is another object of the present invention to provide a data transmission device and a data transmission method capable of sufficiently compensating for the aperture effect given to a modulated signal when generating an OFDM transmission signal. . In addition, the present invention provides a high-quality OFD that sufficiently compensates for the aperture effect.
An object of the present invention is to provide a data transmission device and a data transmission method that can generate a M-system modulated signal with a small-sized and low-cost device.

[0011]

In order to achieve the above object, a data transmission apparatus according to the present invention is a signal for allocating each of a plurality of transmission data to be transmitted to a predetermined signal point of a predetermined orthogonal modulation method. Point allocation means, frequency domain / time domain conversion means for converting one set of the plurality of transmission data respectively allocated to signal points from the frequency domain to the time domain, and the plurality of digital format transmissions converted to the time domain. A digital / analog conversion means for converting data into an analog format and generating a transmission signal, and a carrier signal of a predetermined frequency is modulated by the generated transmission signal by the predetermined orthogonal modulation method, and is transmitted to a predetermined communication transmission line. An OFDM type data transmission device having quadrature modulation means for transmitting, wherein the signal point allocating means is configured in advance in the frequency domain / time domain transforming means. Subsequent to the signal point of said predetermined quadrature modulation scheme gave an amplitude characteristic to compensate for the aperture effect of the transmission signal, assigning the plurality of transmission data.

[0012] Preferably, the signal allocating means is a complex number format signal point data indicating a bit string of the plurality of transmission data and a signal point of the predetermined quadrature modulation method allocated to each of the bit strings of the plurality of transmission data. Are stored in association with each other, and the signal point data is output according to each of the bit strings of the plurality of input transmission data.

Preferably, the signal allocating means counts the number of the bit strings of the plurality of input transmission data,
A counting circuit that supplies this count value to the signal point storage means, a reset circuit that resets the count value of the count circuit each time the bit string of one set of the plurality of transmission data is input, and the plurality of reset circuits. The bit string of the transmission data and the count value of the counting means are used as address input data, the signal point data are stored at storage addresses indicated by the address input data, and the signal point data corresponding to the address input data is stored. And a memory circuit for outputting.

The data transmission apparatus according to the present invention transmits N (N is an integer) transmission data obtained by dividing audio / video data for television broadcasting into N data by the OFDM method. In the data transmission apparatus according to the present invention, the frequency domain / time domain transforming means has one set of signal point allocating means (N
PSK system and QAM assigned to each transmission data
Fast Fourier Inverse Transform (IFFT) processing is performed on signal points of a quadrature modulation method such as a method to convert from a frequency domain to a time domain, and modulation processing is collectively performed on all carrier signals used for transmission.

The digital-analog conversion means converts the digital format transmission data converted in the time domain into an analog format to generate a transmission signal. The digital-analog conversion means has a predetermined frequency characteristic, and the generated transmission signal is given an aperture effect. The quadrature modulation means modulates the carrier signal in the intermediate frequency band with the generated transmission signal by the above quadrature modulation method, and further, if necessary, frequency-converts it to the carrier frequency of the communication transmission line and sends it to the communication transmission line. .

The signal point allocating means preliminarily transmits N transmissions so that the amplitude characteristic of the transmission signal is flattened in the entire transmission frequency band after the aperture effect is given to the transmission signal by the digital-analog conversion means. Each data is assigned to a signal point having an amplitude difference that cancels the aperture effect, and the equalization processing of the transmission signal is unnecessary. Also,
The signal point allocating means gives the modulated signal by the respective components such as the quadrature modulating means after the digital / analog converting means and the aperture effect given to the modulated signal by the communication transmission line etc. Assign to signal points to compensate for aperture effects.

In the data transmission method according to the present invention, a plurality of transmission data, which are assigned to the signal points of the predetermined quadrature modulation method, converted from the frequency domain into the time domain, and converted into the analog format, have a predetermined frequency. OFD for modulating and transmitting each of a plurality of carrier signals by a predetermined orthogonal modulation method
A data transmission method of the M system, wherein the predetermined quadrature modulation system is provided with a predetermined amplitude characteristic in advance so as to compensate an aperture effect given to each of the plurality of transmission data during the modulation and transmission. Each of the plurality of transmission data is assigned to a signal point.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a first embodiment of the present invention will be described. FIG. 1 shows a QPSK (Quadratu) according to the first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a data transmission device 1 of the re Phase Shift Keying) -OFDM system. As shown in FIG. 1, the data transmission device 1 includes a serial / parallel conversion circuit (S / P).
Conversion circuit) 100, signal point transmission device (MOD) 102,
N-point discrete inverse Fourier transform circuit (IFFT circuit) 104, digital / analog converter circuits (D / A converter circuits) 106 ₁ and 106 ₂ , low pass filter circuits (LPF circuits) 108 ₁ and 108 ₂ , QPSK modulation circuit 18 , The transmission circuit 20 and the antenna 126.

The QPSK modulation circuit 18 includes analog multiplication circuits 110 ₁ and 110 ₂ , a π / 2 phase shift circuit 112, an intermediate frequency local oscillation circuit (IFLOSC) 114, an analog addition circuit 116, and an intermediate frequency bandpass filter. It is composed of a circuit (BPF circuit) 118. The transmission circuit 20 includes an analog multiplication circuit 120, a transmission frequency band local oscillation circuit (RFLOSC) 122, and a transmission frequency BPF circuit 124.

For example, when the data transmission device 1 is used for transmitting audio / video data of digital television broadcasting using terrestrial waves, the data transmission device 1 has input data I
As N, the voice compression-encoded by the MPEG system
Video data is input serially. Data transmission device 1
Treats the input data IN as 1-bit 2-bit N data corresponding to signal points of the QPSK modulation method, generates an OFDM modulation signal having N carrier signals in the transmission frequency band, and transmits the OFDM modulation signal. .

The S / P conversion circuit 100 receives the input
N transmission data IN included in the data IN_{k, l}Each
This is converted to 2-bit parallel format data and
To the signal point transmitting device 102 as the control data S100.
Output. FIG. 2 shows the transmission data IN_{k, l}And the value of
QPSK modulation assigned by the indicated signal point transmitting apparatus 102
It is a figure which shows the correspondence with the signal point of a system. Signal point transmitter
102 is the input 2-bit parallel format transmission data.
Tain _{k, l}Depending on the value of (l = 0, 1, ..., N−1),
For example, as shown in FIG. 2, the signal point data of the QPSK modulation system is
TA Z_{k, l}Output to the IFFT circuit 104
I do. Here, the signal point data Z_{k, l}Is a table like
You can

[0022]

## EQU1 ## Z _{k, l} = X _{k, l} + jY _{k, l} where k, l is an integer, k is the number of OFDM symbol sequences, X _{k, l} is the real number component of the signal point data Z _{k, l} , Y _{k, l}
Is an imaginary component of the signal point data Z _{k, l} .

Further, in the data transmission device 1, the absolute value of the signal point data Z _{k, l} is constant as shown in the following equation.

[0024]

## EQU2 ## | Z _{k, l} | = Const However, Const> 0.

The IFFT circuit 104 is a signal point transmitting device 1
A set of N signal point data Z _{k, l} (Z
_{k, 0, Z k, 1} , ..., Z k, N-1) was IFFT processing, N pieces set of complex data _{z k, m (z k,} 0, z k, 1, ..., z
_{k, N-1} ) is generated. However, the complex number data output by the IFFT circuit 104 is expressed by the following equation.

[0026]

Z _{k, l} = x _{k, m} + jy _{k, m} where x _{k, l} is the real component of the complex data z _{k, l} , y _{k, l}
Is the imaginary component of the complex number data z _{k, l} .

D / A conversion circuit 106₁, 106₂Is that
Digital type input from the IFFT circuit 104 respectively
Complex data z of the expression_{k, m}Real component x of_{k, m}And imaginary number
Minute y _{k, m}Is converted to an analog format and the transmission signal S10
6₁, S106₂LPF circuit 108 as₁, 108₂
Output to. LPF circuit 108₁, 108₂Is
D / A conversion circuit 106₁, 106 ₂Entered from
Transmission signal S106₁, S106₂Unnecessary harmonic generation of
Of the transmission signal S108₁, S108₂As Q
Multiplier circuit 110 of PSK modulation circuit 18₁, 110₂Against
And output.

In the QPSK modulation circuit 18, the local oscillation circuit 114 generates a carrier signal in the intermediate frequency band,
It outputs to the multiplication circuit 110 ₁ and the π / 2 phase shift circuit 112. The π / 2 phase shift circuit 112 includes the local oscillation circuit 11
The phase of the carrier signal input from 4 is π / 2 rad
The phase is delayed (90 °) and the phase is shifted, and output to the multiplication circuit 110 ₂ . The multiplication circuits 110 ₁ and 110 ₂ are LP
Transmission signal S1 input from the F circuits 108 ₁ and 108 ₂
08 ₁ , S108 ₂ , the carrier wave signal input from the local oscillator circuit 114, and π by the local oscillator circuit 114.
1/2 rad phase-shifted carrier signal is multiplied in an analog manner, and added as multiplication signals S110 ₁ and S110 _2.
Output to 16.

The adder circuit 116 includes the multiplier circuits 110 ₁ , 1
Multiplied signal input from 10 ₂ S110 _1, S110 ₂
Are added and output as a modulated signal S116 to the BPF circuit 118. The BPF circuit 118 is the addition circuit 116.
The unnecessary signal components other than those in the intermediate frequency band are removed from the modulated signal S116 input from. QPSK modulation circuit 18
Uses these components to modulate the carrier signal in the intermediate frequency band by the QPSK modulation method to generate a modulated signal S18, and outputs the modulated signal S18 to the multiplication circuit 120 of the transmission circuit 20.

In the transmission circuit 20, the local oscillation circuit 12
2 produces | generates the carrier wave signal of the frequency suitable for a communication transmission path, and outputs it to the multiplication circuit 120. Multiplication circuit 120
Is a carrier signal input from the local oscillator circuit 122,
The modulation signal S18 input from the QPSK modulation circuit 18 is multiplied in an analog manner to obtain the modulation signal S1 in the transmission frequency band.
20 is generated and output to the BPF circuit 124.

The BPF circuit 124 removes unnecessary signal components other than the transmission frequency band from the modulation signal S120 input from the multiplication circuit 120. The transmission circuit 20 converts the intermediate frequency band modulated signal S18 into a carrier frequency band modulated signal S20 by these components, and the antenna 12
It is sent to the communication transmission line via 6.

As described above, the data transmission device 1
Is N pieces of transmission data IN forming input data IN such as compression-encoded audio / video data of television broadcasting.
_{With k, l} , N carrier signals in the transmission frequency band are modulated to generate an OFDM modulated signal S20, which is distributed to the receiving device at the viewer's house.

According to the data transmission device 1 of the present invention,
The transmission data can be transmitted at the same transmission data rate as when the modulation method such as the QAM method is used.
Since the transmission data rate per one modulated signal can be lowered, it is less likely to be affected by a multipath ghost failure or the like. Therefore, the data transmission device 1 is suitable for digital television broadcasting using terrestrial waves. Further, since the data transmission device 1 performs data transmission by the OFDM system, it is suitable for SFN system transmission and can effectively use frequency resources.

Although the data transmission apparatus 1 in the first embodiment uses the QPSK method as the modulation method in the QPSK modulation circuit 18, for example, the S / P conversion circuit 10 is used.
Change 0 to generate 4-bit parallel data,
The QPSK modulation circuit 1 is modified by changing the signal point transmitting device 102 so as to allocate signal points of the 16QAM system.
Other multi-level quadrature modulation schemes such as 16QAM scheme can be used in 8, and a plurality of modulation schemes, for example, QAM scheme and PSK scheme can be mixed in the QPSK modulation circuit 18.

Each component of the data transmission device 1 is
It does not matter whether it is realized by hardware or software as long as equivalent functions and performances can be guaranteed. Further, the data transmission device 1 can be used not only for transmitting audio / video data of a television program but also for other types, for example, for transmitting data for a computer.

Further, the data transmission method in the data transmission device 1 can be applied not only to the data transmission device but also to, for example, recording in a magnetic recording device. Further, the data transmission device 1 can be used not only for data transmission via a wireless communication transmission line, but also for data transmission via a wired communication transmission line.

Second Embodiment Hereinafter, a second embodiment of the present invention will be described. FIG. 3 shows the QPSK-OFDM according to the present invention in the second embodiment.
It is a figure which shows the structure of the data transmission apparatus 2 of a system. As shown in FIG. 3, the data transmission device 2 includes an S / P conversion circuit 10
0, signal point transmitting device 14, IFFT circuit 16, D / A conversion circuits 106 ₁ and 106 ₂ , LPF circuits 108 ₁ and 10
8 ₂ , a QPSK modulation circuit 18, a transmission circuit 20 and an antenna 126. The components and signals (data) of the data transmission device 2 that are the same as the data transmission device 1 shown in FIG. 1 are denoted by the same reference numerals.

FIG. 4 shows the signal point transmitting device 14 shown in FIG.
It is a figure which shows the structure of. As shown in FIG. 4, the signal point transmitting device 14 includes a ROM 142 and a carrier wave counter circuit 1.
It is composed of 44. The carrier wave counter circuit 144 counts up the count value every time the parallel data S100 is input to the signal point transmission device 14. That is, the signal point delivery device 14 transmits data INZ _k, subscripts _l l (l =
0, 1, ..., N-1) is counted, and the count value S144 (0,
, ..., N-1; ROM # 0 to ROM # N-1 (FIG. 5)) with respect to the ROM 142, for example, the ROM 142
Of the modulated signal S20.
R stored in the ROM 142 for each carrier in
The OM table (ROM # 0 to ROM # N-1) is switched. The count value of the carrier wave counter circuit 144 is I
It is reset by the reset signal S16c input from the FFT circuit 16 and becomes 0.

As described above, the count value S144 of the carrier wave counter circuit 144 is input as the high-order bit of the address of the ROM 142. For example, as the low-order bit, S /
Parallel data S10 input from the P conversion circuit 100
0 and the count value S144 of the carrier wave counter circuit 144 are input.

FIG. 5 is a diagram showing the contents of the signal point data Z _{k, l} stored at the address of the ROM 142 shown in FIG. It should be noted that the signal point data Z _{k, l} is the IFFT circuit 16
The following shows the case where the amplitude characteristics (aperture effect) given to the modulated signal S20 by the respective parts of the D / A conversion circuits 106 ₁ and 106 ₂ and the communication transmission line are represented by sinc [kπ / 2N].

At each address of the ROM 142, as shown in FIG. 5, the signal point data Z _{k, l} is stored in the ROM table (ROM # 0-RO #) for each N carrier signals of the modulated signal S20.
M # N-1) is stored in a complex number format.
Here, similarly to the case of the data transmission device 1 (FIG. 1), also in the data transmission device 2, the signal point data Z _{k, l} can be expressed by the following equation.

[0042]

Z _{k, l} = X _{k, l} + jY _{k, l} where k, l is an integer, k is the number of OFDM symbol sequences, X _{k, l} is the real number component of the signal point data Z _{k, l} , Y _{k, l}
Is an imaginary component of the signal point data Z _{k, l} .

The absolute value of the signal point data Z _{k, l} stored in the ROM 142 is the carrier wave counter circuit 144.
Of the parallel data S100 input from the S / P conversion circuit 100 and the count value S144 of the IF
Each of the components after the FT circuit 16, in particular, the D / A conversion circuits 106 ₁ and 106 ₂ , or a predetermined value so as to compensate the aperture effect given to the modulation signal S20 by the frequency characteristic of the communication transmission line measured in advance. The frequency characteristic of is added. Unlike the data transmission device 1 (FIG. 1), in the data transmission device 2, the absolute value (amplitude, average power) of the signal point data Z _{k, l} is not constant, as shown in the following equation.

[0044]

[Expression 5] | Z _{k, l} | = f (S144, S100) where f (S144, S100)> 0, f (S144,
S100) is parallel data S100 and count value S1
It is the amplitude of the signal point determined according to 44.

The IFFT circuit 16 is used in the data transmission device 1
Similar to the IFFT circuit 104 of FIG. 1, a set of N signal point data Z _{k, l} output from the signal point transmission device 102.
(Z _{k, 0} , Z _{k, 1} , ..., Z _{k, N-1} ) is IFFT processed,
A set of N complex number data z _{k, m} (z _{k, 0} , z _{k, 1} , ...,
z _{k, N-1} ) is generated.

The IFFT circuit 16 activates the reset signal S16c every time N (one set) of signal point data Z _{k, l} is input from the signal point transmitting device 14, and the carrier wave of the signal point transmitting device 14 is activated. Count value S14 of the counter circuit 144
Clear 4 to 0. Similar to the IFFT circuit 104 of the data transmission device 1 (FIG. 1), the complex number data output by the IFFT circuit 16 is expressed by the following equation.

[0047]

Z _{k, l} = x _{k, m} + jy _{k, m} where x _{k, l} is the real number component of complex number data z _{k, l} , y _{k, l}
Is the imaginary component of the complex number data z _{k, l} .

The operation of the data transmission device 2 will be described below. The S / P conversion circuit 100 converts each of the N pieces of transmission data IN _{k, l} input in the serial format into parallel data S100 in the 2-bit parallel format. In the signal point transmission device 14, the carrier wave counter circuit 144 has a count value S1 indicating the number of input parallel data S100.
44 is output as the upper bits of the address of the ROM 142, and the ROM table (ROM # 0 to ROM # N-1) stored in the ROM 142 is selected.

The value of the parallel data S100 is input to the lower bits of the ROM 142, and the ROM 142 stores the value shown in FIG.
The signal point data Z _{k, l} corresponding to the count value S144 of the ROM 142 and the parallel data S100 shown in FIG.
Output to the circuit 16. The IFFT circuit 16 IFFT-processes a set of N signal point data Z _{k, l} (Z _{k, 0} , Z _{k, 1} , ..., Z _{k, N−1} ) input from the signal point transmission device 14. , N set of complex data z _{k, m} (z _{k, 0} ,
z _{k, 1} , ..., Z _{k, N−1} ) to generate the D / A conversion circuit 10
It outputs to 6 ₁ and 106 ₂ .

[0050] D / A conversion circuit 106 _1, 106 ₂ and LPF circuits 108 _1, 108 ₂ converts complex data z _{k, respectively,} the real component x _k of _{m, m} and imaginary components y _k, a _m to analog form , And removes unnecessary harmonic components to generate transmission signals S106 ₁ and S106 _2, which are output to the QPSK modulation circuit 18.

The QPSK modulation circuit 18 converts the carrier signal in the intermediate frequency band into the transmission signal S1 by the QPSK modulation method.
06 _1, S106 ₂ in modulation to generate a modulated signal S18, the output to the transmitting circuit 20. The transmission circuit 20 is
The modulated signal S18 is converted into a modulated signal S20 in the carrier frequency band and sent out to the communication transmission line via the antenna 126.

As described above, the data transmission device 2 is
The D / A conversion circuit 106 is set in advance by the signal point transmission device 16.
₁ , 106 ₂ or the modulation signal S20 depending on the communication transmission line
Since the signal point data Z _{k, l} whose amplitude is changed according to the input data IN _{k, l} (parallel data S100) is assigned so as to compensate for the aperture effect given to, the filter for equalization is not used. , The amplitude characteristic of the modulated signal S20 can be flattened within the entire transmission frequency band. Therefore, the error rate of the reproduced input data IN _{k, l} can be reduced.

Further, the data transmission device 2 uses the modulated signal S2
Since an equalization filter for equalizing 0 is unnecessary,
The circuit scale is small and the cost is low. Further, the data transmission device 2 uses the input data IN _{k, l} (parallel data S10
Since the signal point data Z _{k, l} optimized in advance can be assigned to 0), it is possible to sufficiently compensate the aperture effect for the modulated signal S20. The data transmission device 2 shown as the second embodiment can be modified in the same manner as the data transmission device 1 (FIG. 1) shown as the first embodiment.

[0054]

As described above, according to the data transmission device and the data transmission method of the present invention, the quality of the modulation signal generated by the OFDM system can be further improved. Further, according to the data transmission device and the data transmission method of the present invention, the data error rate of the transmission data reproduced from the modulated signal passing through the communication line can be reduced.

Further, according to the data transmission device and the data transmission method of the present invention, the aperture effect given to the modulated signal can be sufficiently compensated when the OFDM modulated signal is generated. Further, according to the data transmission device and the data transmission method of the present invention, it is possible to generate a high-quality OFDM modulation signal in which the aperture effect is sufficiently compensated with a small-sized and low-cost device.

[Brief description of drawings]

FIG. 1 is a QPSK according to the present invention in a first embodiment.
FIG. 3 is a diagram showing the configuration of an OFDM data transmission device.

FIG. 2 is a diagram showing the correspondence between the value of transmission data IN _{k, l} and the signal points of the QPSK modulation method assigned by the signal point transmitting apparatus shown in FIG.

FIG. 3 is a QPSK according to the present invention in a second embodiment.
FIG. 3 is a diagram showing the configuration of an OFDM data transmission device.

FIG. 4 is a diagram showing a configuration of a signal point transmission device shown in FIG.

5 is a diagram showing the contents of signal point data Z _{k, l} stored at an address of the ROM shown in FIG.

[Explanation of symbols]

1, 2 ... Data transmission device, 100 ... S / P conversion circuit, 1
02, 14 ... Signal point sending device, 104, 16 ... IFFT
Circuit, 106 ₁ , 106 ₂ ... D / A conversion circuit, 18 ... Q
PSK modulation circuit, 108 ₁ , 108 _2, ... LPF circuit, 1
10 ₁ , 110 ₂ ... Multiplication circuit, 112 ... π / 2 phase shift circuit, 114 ... Local oscillation circuit, 116 ... Addition circuit, 118
... BPF circuit, 20 ... Transmission circuit, 120 ... Multiplication circuit, 1
22 ... Local oscillation circuit, 124 ... BPF circuit, 126 ... Antenna

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04N 7/081 (72) Inventor Yasunari Ikeda 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Within the corporation

Claims (4)

[Claims] 1. A signal point allocating means for allocating each of a plurality of transmission data to be transmitted to a predetermined signal point of a predetermined quadrature modulation method, and a plurality of transmission data allocated to each signal point.
Frequency-domain / time-domain conversion means for converting from the frequency domain to the time domain, and digital-analog conversion means for converting the plurality of transmission data in the digital format converted into the time domain into an analog format to generate a transmission signal. And a quadrature modulation method that modulates a carrier signal of a predetermined frequency with the generated transmission signal by the predetermined quadrature modulation method, and sends the modulated signal to a predetermined communication transmission path. The signal point allocating means preliminarily assigns the plurality of transmission data to the signal points of the predetermined quadrature modulation method to which an amplitude characteristic for compensating the aperture effect given to the transmission signal by the frequency domain / time domain converting means and thereafter is given. Data transmission device for allocating. 2. The signal allocating means stores a bit string of the plurality of transmission data and signal point data in a complex number format indicating a signal point of the predetermined orthogonal modulation method allocated to each of the bit strings of the plurality of transmission data. The data transmission device according to claim 1, wherein the signal point data is stored in association with each other and outputs the signal point data in accordance with each of the bit strings of the plurality of input transmission data. 3. The signal allocating means counts the number of the bit strings of the plurality of input transmission data and supplies the count value to the signal point storing means, and a set of the plurality of bit lines. A reset circuit that resets the count value of the counting circuit each time the bit string of the transmission data is input, the bit string of the plurality of transmission data and the count value of the counting means as address input data, and the address input The data transmission device according to claim 2, further comprising a memory circuit that stores each of the signal point data at a storage address indicated by each data and outputs the signal point data according to the address input data. 4. A plurality of carrier signals having a predetermined frequency are respectively assigned a predetermined orthogonal by a plurality of transmission data which are assigned to the signal points of the predetermined quadrature modulation system, converted from a frequency domain into a time domain, and converted into an analog format. A data transmission method of an OFDM method, which is modulated by a modulation method and transmitted, so as to compensate an aperture effect given to each of the plurality of transmission data at the time of the modulation processing and transmission,
A data transmission method in which each of the plurality of transmission data is assigned to a signal point of the predetermined quadrature modulation method to which a predetermined amplitude characteristic is given in advance.