JP3421879B2 - Demodulator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission system suitable for application when, for example, communication is performed with a mobile unit.

[0002]

2. Description of the Related Art Conventionally, various mobile communication systems have been put into practical use for communicating with mobile devices such as car phones and mobile phones. The conventional mobile communication is basically the same communication method as that used for communication between fixed stations.

However, a received signal received by a mobile communication terminal such as a car telephone or a portable telephone is apt to be distorted due to the influence of multipath fading. That is, multipath fading occurs, the propagation delay between the paths increases, intersymbol interference occurs, and the codes before and after overlap, which deteriorates the transmission characteristics.

In order to ensure good reception even when the transmission characteristics deteriorate, it is necessary to apply a synchronous detection circuit or the like using an adaptive equalizer or a PLL circuit, which makes the structure of the receiver complicated and expensive. turn into.

In order to solve this problem, the present applicant has previously proposed a so-called multi-carrier system in which a plurality of carriers are simultaneously transmitted, in which information is transmitted by the phase difference between the carriers. Yes (Japanese Patent Application No. 6-
No. 216311: Details of this communication method will be described in an example described later).

[0006]

By the way, in such a multi-carrier communication system, there are the following problems at the time of reception.

It is difficult to accurately synchronize the demodulation timing of one received wave for each modulation unit time of the transmitted signal, and there is a disadvantage that an offset occurs in the demodulation timing. When an offset occurs in this demodulation timing, an error depending on the carrier frequency occurs in the demodulated phase information,
The decision error rate increases. If the synchronization data is added to the transmission signal in order to obtain this demodulation timing, the amount of information that can be transmitted is reduced by that much, and there is a disadvantage that the transmission efficiency is reduced.

2 It was difficult to remove the frequency offset of the received wave. When this frequency offset exists, a fixed value error occurs in the demodulated phase difference information, and the decision error rate increases.

In view of these points, an object of the present invention is to provide a demodulation device which can easily remove a timing offset and a frequency offset in a multicarrier communication system.

[0010]

According to the present invention, for example, as shown in FIG. 1, in a demodulating device for receiving and demodulating a signal in which a plurality of carriers having different frequencies are simultaneously transmitted, sampling for sampling the received signal is performed. Means 1
02, and frequency analysis means 103 for frequency-analyzing the sampling signal of this sampling means for each carrier,
The determination means 104 determines the transmission phase from the analysis output of the frequency analysis means, and the phase difference detection means 107 detects the phase difference between the analysis output phase of the frequency analysis means 103 and the phase value determined by the determination means 104. , Phase difference detection means 1
Based on the phase difference detected in 07, the sampling means 1
The sampling timing in 02 is corrected.

Further, in this case, for example, as shown in FIG. 3, after demodulating the phase value judged by the judging means 104, error correction is carried out by the error correcting means 108, and the demodulated signal whose error is corrected is modulated, A duplicated signal of the phase value judged by the judging means 104 is generated, and the copied signal and the frequency analyzing means 1 are generated.
The sampling timing in the sampling means 102 is corrected based on the phase difference from the analysis output phase of 03.

The present invention also provides, for example, as shown in FIG.
In a demodulation device for receiving and demodulating signals simultaneously transmitted by a plurality of carriers having different frequencies, frequency conversion means 112 for frequency-converting a received signal transmitted at a predetermined frequency into a signal in a predetermined frequency band, and Sampling means 102 for sampling the signal output by the frequency conversion means 112, frequency analysis means 103 for frequency-analyzing the sampling signal of the sampling means 102 for each carrier, and determination of the transmission phase from the analysis output of the frequency analysis means 103. Cross-correlation detection means 11 for detecting the cross-correlation between the analysis output phase of the frequency analysis means 103 and the phase value judged by the judgment means 104.
3, the receiving frequency offset is detected from the cross-correlation detected by the cross-correlation detecting means 113, and the frequency converted by the frequency converting means 112 is corrected by the detected offset.

Further, in this case, for example, as shown in FIG. 6, after the phase value judged by the judging means 104 is demodulated, error correction is carried out by the error correcting means, and the demodulated signal whose error is corrected is modulated to make the judgment. A duplication signal having the phase value determined by the means 104 is generated, and the frequency to be converted by the frequency modulation means 112 is corrected based on the cross-correlation between the duplication signal and the analysis output phase of the frequency analysis means 103. is there.

Further, in each case, information is transmitted by the phase difference between a plurality of carriers.

[0015]

According to the present invention, the phase value obtained by frequency analysis by the frequency analysis means is used as the temporary judgment value, and sampling is performed by detecting the difference between this temporary judgment value and the value officially judged by the judgment means at the subsequent stage. By detecting the timing offset and correcting the sampling timing by this offset,
You will be able to sample at accurate timing.

In this case, the value judged by the judging means is demodulated, error-corrected and then modulated to generate a duplicated signal of the decided signal, and the difference between the phase value of the duplicated signal and the temporary decision value is calculated. By detecting the offset of the sampling timing in the detection, the offset can be detected more accurately.

Further, according to the present invention, the phase value obtained by frequency analysis by the frequency analysis means is used as the temporary judgment value, and the cross-correlation between this temporary judgment value and the value officially judged by the latter judgment means can be detected. By detecting the frequency offset and correcting the conversion frequency by this offset, it becomes possible to receive at an accurate frequency.

In this case, the value judged by the judging means is demodulated, error-corrected and then modulated to generate a duplicated signal of the decided signal, and the cross-correlation between the phase value of the duplicated signal and the temporary decision value. By detecting the frequency offset,
The offset can be detected more accurately.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In this example, the demodulator of the receiving system of the communication system in which the wireless communication of digital data is performed by the multicarrier system is applied. First, the structure of the transmission system of the multicarrier system as a prerequisite is shown in FIG. 7 shows. In FIG. 7, reference numeral 1 denotes a transmission data input terminal, and 8-bit data is sequentially supplied to the input terminal 1. The circuit of this example processes the 8-bit data as one modulation unit.
Then, the 8-bit data is divided into 2 bits each, and the divided 2-bit data is supplied to different transmission data / phase data conversion circuits 2, 3, 4, and 5, respectively.
The transmission data / phase data conversion circuits 2 to 5 generate phase data according to the state of the supplied 2-bit data [X, Y]. That is, as the states of the 2-bit data [X, Y], the four states shown in Table 1 below can be considered, and the respective conversion circuits 2 to 5 generate different phase data Δφ for each of the four states.

[0021]

[Table 1]

Here, the phase data output from the four transmission data / phase data conversion circuits 2, 3, 4, and 5 are Δ
Let φ ₀ , Δφ ₁ , Δφ ₂ , and Δφ ₃ .

Reference numeral 6 in the drawing denotes a reference phase data generation circuit. This reference phase data generation circuit 6 generates reference initial phase data φ ₀ , and this initial phase data φ ₀ is supplied to the phase multiplier 7 and the carrier. It is supplied to the multiplier 11. Then, the phase data Δφ ₀ output from the transmission data / phase data conversion circuit 2 is supplied to the phase multiplier 7, and the initial phase data φ ₀ and the phase data Δφ ₀ are multiplied to obtain the phase data φ ₁
To get Then, the phase data φ ₁ obtained by this multiplication is supplied to the phase multiplier 8 and the carrier multiplier 12.

Further, the transmission data / phase data conversion circuit 3
The phase data Δφ ₁ output by the
The phase data φ ₁ and the phase data Δφ ₁ are multiplied to obtain the phase data φ ₂ . Then, the phase data φ ₂ obtained by this multiplication is supplied to the phase multiplier 9 and the carrier multiplier 13.

Further, the transmission data / phase data conversion circuit 4
The phase data Δφ ₂ output by the
The phase data φ ₂ and the phase data Δφ ₂ are multiplied to obtain the phase data φ ₃ . Then, the phase data φ ₃ obtained by this multiplication is supplied to the phase multiplier 10 and the carrier multiplier 14.

Further, the phase data Δφ ₃ output from the transmission data / phase data conversion circuit 5 is supplied to the phase multiplier 10, and the phase data φ ₃ and the phase data Δφ ₃ are multiplied,
Obtain the phase data φ ₄ . Then, the phase data φ ₄ obtained by this multiplication is supplied to the carrier multiplier 15.

Therefore, the initial phase data φ₀To each multiplier
Phase data Δφ at 7, 8, 9, and 10 ₀~ Δφ₃Are ranked in order
Phase data φ₁~ Φ_FourIs formed
It

Further, in the figure, 16, 17, 18, 19, 20
Indicate the first, second, third, fourth and fifth carrier input terminals, respectively, to which carrier signals having different frequencies are supplied. In this case, the input terminals 16, 17, 1
The frequency of the carrier signal supplied to 8, 19, 20 is
The frequencies are separated by a constant angular frequency ωs. That is, the first, second, third, fourth and fifth carrier signals are changed, for example, as shown in A, B, C, D and E of FIG. However, in reality, each carrier signal is a complex signal.

Then, the carrier multiplier 11 multiplies the carrier obtained at the first carrier input terminal 16 by (initial) phase data φ ₀ , and the carrier multiplier 12 obtains the carrier obtained at the second carrier input terminal 17. The phase data φ ₁ is multiplied, the carrier multiplier 13 multiplies the carrier obtained at the third carrier input terminal 18 by the phase data φ ₂ , and the carrier multiplier 14 obtains the carrier obtained at the fourth carrier input terminal 19. The phase data φ ₃ is multiplied, the carrier multiplier 15 multiplies the carrier obtained at the fifth carrier input terminal 20 by the phase data φ _4, and the phase of the carrier signal at each multiplier is the phase indicated by the phase data. Proceed.

Then, the multiplication outputs of the carrier multipliers 11 to 15 are supplied to the mixer 21, mixed by the mixer 21, and supplied to the multiplier 24.

In the multiplier 24, the transmission signal is multiplied by the time waveform output from the time waveform generation circuit 23, and the transmission signal is multiplied by the time waveform (details of the time waveform will be described later). Is supplied to the transmission signal output terminal 22.

In the modulation by multiplication by the carrier multipliers 11 to 15, one modulation unit Tm is expressed by the following equation, where T is the time during which the angular frequency ωs, which is the frequency difference between the carriers, advances by 2π. .

[0033]

## EQU1 ## Tm = (1 + α) T

That is, the time T at which the angular frequency ωs advances by 2π
In addition, the time with a margin of αT is set as one modulation unit. FIG. 8 is a diagram showing each carrier of this one modulation unit,
It is possible to show the phase difference only in the period indicated by T in the central part of one modulation unit, but in reality, the phase difference (α /
2) The same modulation is performed during the period indicated by T.

The time waveform output from the time waveform generating circuit 23 has the structure shown in FIG. This time waveform is a waveform multiplied by each modulation unit. First, the data structure of one modulation unit will be described.
As shown in the above-mentioned [Equation 1], m is a time with a margin of αT, and this margin time αT is (α /
2) Each T is divided into two equal parts, and they are arranged before and after the central data body T.

The time waveform is a waveform that maintains a constant level in the central data body T, and of the margin time (α / 2) T before and after the data body T,
A predetermined interval (-T _{G to} 0 interval and T to T + T _G interval) adjacent to the data body portion T is a guard time portion, and a waveform that maintains the same constant level as the data body portion T in this guard time portion as well. There is. Then, the lamp unit remaining margin time (-T _G -T _R interval ~-T _G and T + T _G
.About.T + T _G + T _R ), and has a waveform that rises to a certain level in the ramp portion before and after this. It should be noted that the rising waveform is a sin (or co
It is a waveform of a curve shown by an odd function (a curve having odd symmetry at a rising edge and a falling edge) of the function of s).

Then, the output signal of the transmission signal output terminal 22 from which a transmission signal multiplied by such a time waveform is obtained is frequency-converted into a predetermined transmission channel (transmission frequency) and supplied to the antenna for radio transmission. I do.

Next, the configuration of the demodulation device of this example for receiving and demodulating the signal thus transmitted will be described with reference to FIGS. The demodulation device of the present example is capable of correcting the sampling timing and the frequency offset. First, a configuration for correcting the sampling timing will be described with reference to FIG.

In FIG. 1, reference numeral 101 denotes an input terminal from which a baseband received signal is obtained.
The baseband signal obtained at
2 is supplied to the frequency analysis circuit 103, sampling is performed at a predetermined timing, and the sampled reception signal is supplied to the frequency analysis circuit 103. The frequency analysis circuit 103 is composed of, for example, a fast Fourier transform circuit (FFT circuit), and data of a predetermined sampling point is used for each modulation unit to perform a calculation by fast Fourier transform. Then 5)
Demodulated from each carrier to obtain the phase information superimposed on the carrier for each carrier, and the phase information for each carrier (that is, 5
Phase information is provided to the decision circuit 104. In addition, F
Instead of using the FT circuit, five carriers may be individually superimposed on the baseband signal to obtain five pieces of phase information.

Then, the judging circuit 104 judges the supplied phase information for each carrier as the phase value existing in the modulation system defined by this communication system. For example, as shown in FIG. 2, when the I component and the Q component are quadrature-modulated phase modulation, the position indicated by a circle in the figure as a phase value is the original phase position, but for some reason There is a possibility that the phase value deviated to the position indicated by x may be output from the frequency analysis circuit 103. Here, the determination circuit 104 is a circuit that determines the original phase position indicated by the circle even if there is such a phase shift.

Then, the judgment circuit 5 judges 5
The individual phase position information is supplied to the differential demodulator 105, the phase difference between the five determined phase positions is detected, and each detected phase difference is converted into 2 bits according to the conversion rule of [Table 1] described above. The data is demodulated and four 2-bit data obtained from the four phase differences between the five carriers are combined to obtain 8-bit data, and the demodulated 8-bit data is obtained at the output terminal 106.

In this example, the frequency analysis circuit 1
The five pieces of phase information output by 03 and the five pieces of phase information determined by the determination circuit 104 are supplied to the timing offset calculation circuit 107. Then, the timing offset calculation circuit 107 calculates the timing offset amount by comparing the phase information of the signals demodulated from the same carrier. That is, for example, as shown in FIG. 2, as a phase value demodulated from a certain carrier, the frequency analysis circuit 10
When the output of No. 3 is the position indicated by x, and the output of the determination circuit 104 is the position indicated by o, a is detected as the timing offset amount.

Then, the data of the detected timing offset amount is supplied to the sampling circuit 102. In this sampling circuit 102, the sampling timing is adjusted so that the timing offset amount indicated by the supplied data becomes zero.

In this case, since the multicarrier system is used in this example, the timing offset amount is detected for each phase data transmitted by each carrier. For example, the timing offset amount detected for every five carriers is detected. The sampling timing may be adjusted by averaging the amounts. Alternatively, only the timing offset amount of the phase data transmitted by any of the five carriers may be detected, and the sampling timing may be adjusted based on this timing offset amount.

By adjusting the sampling timing in this way, as a result, sampling is performed at the phase position indicated by ◯ in FIG. 2, and sampling can be performed at accurate timing. Therefore, the demodulation timing can be accurately matched even if the timing detection data such as the synchronization signal is not superimposed on the transmission signal.
Accurate reception processing can be performed with a simple and highly efficient configuration that does not use a synchronization signal or the like.

Here, the correction processing of the sampling timing in the circuit of FIG. 1 will be described using mathematical expressions.

First, the baseband received signal (that is, the transmitted signal created by the circuit of FIG. 7) obtained at the input terminal 101 is expressed by the following equation.

[0048]

[Equation 2] Here, φ _l is the phase of the signal obtained by differentially QPSK modulating the information, ω _s is the basic carrier frequency, and T = 2π / ω _s
Have a relationship.

When this signal has a timing offset δ, the signal of the formula [2] is as follows.

[0050]

[Equation 3]

If a signal having this timing offset δ is obtained at the input terminal 101, the frequency analysis circuit 1
As the output of 03, φ _l ′ in the above equation is obtained. Then, by supplying this φ _l ′ to the determination circuit 104, a provisional phase determination value φ _l ″ is obtained. Then, using this detected phase value φ _l ′ and the determination value φ _l ″, the timing offset calculation is performed. In the circuit 107, δ of the above equation [Formula 2] is calculated, and by correcting the calculated timing offset δ, sampling is performed at good timing.

In the example of FIG. 1, the determination circuit 104
The data obtained as a result of the determination is supplied to the timing offset calculation circuit 107. However, after the determined phase data is demodulated into bit data and error correction is performed, the error-corrected bit data is transferred to this communication system. The phase data obtained by modulating with the applied modulation method may be supplied to the timing offset computing circuit 107.

FIG. 3 is a diagram showing the configuration in this case, in which 8-bit data in one modulation unit obtained by differential demodulation by the differential demodulator 106 is supplied to the channel decoder 108 for channel decoding. . At the time of this decoding, error correction is performed using the error correction code added to the transmitted data, and corrected bit data is obtained. The error-corrected bit data is then sent to the channel encoder 10
9 to encode into bit data for modulation.
Then, the bit data encoded by the channel encoder 109 is supplied to the differential modulator 110, and the modulation processing reverse to that of the differential demodulator 106 (that is, the conversion circuits 2 to 5 of the transmission processing configuration of FIG. The same processing as the processing by the multipliers 7 to 10) is performed to obtain 5 pieces of phase data.
Then, the five pieces of phase data are supplied to the timing offset calculation circuit 107, compared with the phase data output from the frequency analysis circuit 103 to generate data of the timing offset amount, and supplied to the sampling circuit 102.

The other parts are constructed similarly to the circuit of FIG.

As described above, by comparing the error-corrected data with the phase data output from the frequency analysis circuit 103 to detect the timing offset amount, it is possible to compare the data with more accurate data and more accurate timing. The offset amount can be adjusted.

Next, the structure for correcting the frequency offset in the demodulator of this example will be described with reference to FIG.

The configuration of FIG. 4 is a diagram showing the configuration of frequency-converting a received signal. Reference numeral 111 denotes an input terminal from which a received signal of a predetermined transmission channel is obtained, and the received signal obtained at this input terminal 111 is The signal is supplied to the frequency conversion circuit 102, a predetermined frequency signal is mixed in this frequency conversion circuit 102, and the signal frequency-converted into the transmission channel is demodulated to a baseband signal.

Then, this baseband signal is supplied to the frequency analysis circuit 103 via the sampling circuit 102, phase information for each carrier (that is, five pieces) is obtained, and this phase information is supplied to the determination circuit 104. . Then, the phase information determined by the determination circuit 104 is supplied to the differential demodulator 105, the phase difference between the phases indicated by each phase information is detected, and 2-bit data is obtained from each phase difference. Then, a total of 8-bit data is obtained, and this 8-bit data is obtained at the output terminal 106. The configuration from sampling this baseband signal to demodulating to 8-bit data is
This is the same as the example of FIG.

In this example, the frequency analysis circuit 1
The five pieces of phase information output by 03 and the five pieces of phase information determined by the determination circuit 104 are supplied to the cross-correlation detection circuit 113. The cross-correlation detection circuit 113 detects the cross-correlation of the phase values demodulated from each carrier. And
The data of the detected cross-correlation value is used as the frequency conversion circuit 112.
To correct the frequency for converting the received signal into a baseband signal so that the cross-correlation value becomes a predetermined state. By correcting this frequency, the frequency offset of the received signal can be corrected.

Here, since it is possible to correct the frequency offset by detecting this cross-correlation, description will be made using mathematical expressions.

First, when a frequency offset σ exists in the output of the frequency conversion circuit 112, this output signal is expressed by the following equation.

[0062]

[Equation 4]

Then, this signal is applied to the frequency analysis circuit 103.
, The phase value φ _l ″ ′ with an error is obtained.
Then, by supplying this φ _l ″ ′ to the determination circuit 104, a provisional phase determination value φ _l ″ ″ is obtained, and the cross-correlation value between this detected phase value φ _l ″ ″ and the determination value φ _l ″ ″. S (α)
Is expressed by the following equation.

[0064]

[Equation 5]

The equation (5) indicates that the phase value of the received data and the determined phase value are added by the amount corresponding to 5 carriers.

Here, considering, for example, the case where there is no frequency offset, the phase data included in a certain carrier is
As shown in A of FIG. 5, only one frequency is output. On the other hand, this phase data has a frequency offset b
When there is, an output corresponding to the offset amount is obtained for other frequency components as shown in B of FIG. The example of FIG. 5 shows a case where only one of the five carriers has information. Therefore, using the cross-correlation values S (-1), S (0), and S (1), the function value Re
By calculating as [S (0) × {S (1) -S (-1)}, the function value decreases as the correlation decreases.
Here, the frequency offset can be corrected by controlling the frequency to be frequency-converted so that the frequency becomes higher only where there is a correlation.

Since the frequency offset can be corrected in this way, it becomes possible to receive at an accurate frequency.
Therefore, an accurate reception process can be performed with a reception circuit having a simple structure.

In the example of FIG. 4 as well, the determination circuit 104
Instead of supplying the data obtained as a result of the determination to the cross-correlation calculation circuit 113, the determined phase data is demodulated into bit data and subjected to error correction, and the error-corrected bit data is applied to this communication system. The phase data obtained by the modulation with the modulation method may be supplied to the cross-correlation calculation circuit 113.

FIG. 6 is a diagram showing the configuration in this case, in which 8-bit data in one modulation unit obtained by differential demodulation by the differential demodulator 106 is supplied to the channel decoder 108 for channel decoding. . At the time of this decoding, error correction is performed using the error correction code added to the transmitted data, and corrected bit data is obtained. The error-corrected bit data is then sent to the channel encoder 10
9 to encode into bit data for modulation.
Then, the bit data encoded by the channel encoder 109 is supplied to the differential modulator 110, and the modulation processing reverse to that of the differential demodulator 106 (that is, the conversion circuits 2 to 5 of the transmission processing configuration of FIG. The same processing as the processing by the multipliers 7 to 10) is performed to obtain 5 pieces of phase data.
Then, the five pieces of phase data are converted into the cross-correlation calculation circuit 11
3 to calculate the cross-correlation with the phase data output from the frequency analysis circuit 103, and supply the correction data of the frequency offset amount to the frequency conversion circuit 112.

The other parts are configured similarly to the circuit of FIG.

As described above, by comparing the error-corrected data with the phase data output from the frequency analysis circuit 103 and detecting the frequency offset amount, more accurate data can be compared and more accurate data can be obtained. The amount of frequency offset can be adjusted.

Although the above-described embodiment is applied to the multi-carrier system for transmitting data by the phase difference between a plurality of carriers, the multi-carrier system of other systems can be used as long as it is a system for superimposing and transmitting a similar time waveform. It can also be applied to a carrier communication system.

[0073]

According to the present invention, the phase value obtained by frequency analysis by the frequency analysis means is used as a temporary judgment value, and the difference between this temporary judgment value and the value officially judged by the latter judgment means can be detected. ,
By detecting the offset of the sampling timing and correcting the sampling timing by this offset, it becomes possible to perform sampling at accurate timing.

In this case, the value judged by the judging means is demodulated, error-corrected and then modulated to generate a duplicated signal of the decided signal, and the difference between the phase value of the duplicated signal and the temporary decision value is calculated. By detecting the offset of the sampling timing in the detection, the offset can be detected more accurately.

Further, according to the present invention, the phase value obtained by frequency analysis by the frequency analysis means is used as the temporary judgment value, and the cross-correlation between this temporary judgment value and the value officially judged by the latter judgment means can be detected. By detecting the frequency offset and correcting the conversion frequency by this offset, it becomes possible to receive at an accurate frequency.

In this case, the value judged by the judging means is demodulated, error-corrected and then modulated to generate a duplicated signal of the decided signal, and the cross-correlation between the phase value of the duplicated signal and the tentative decision value. By detecting the frequency offset,
The offset can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a timing offset removing circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a generation state of a timing offset.

FIG. 3 is a configuration diagram showing a timing offset removal circuit according to another embodiment.

FIG. 4 is a configuration diagram showing a frequency offset removing circuit according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a frequency offset occurrence state.

FIG. 6 is a configuration diagram showing a frequency offset removal circuit according to another embodiment.

FIG. 7 is a configuration diagram showing a transmission processing configuration of a communication system to which an embodiment is applied.

FIG. 8 is a waveform diagram showing an example of each carrier of a communication system to which an embodiment is applied.

FIG. 9 is a waveform diagram showing an example of a time waveform according to an embodiment.

[Explanation of symbols]

1 Transmission data input terminal 2,3,4,5 Transmission data / phase data conversion circuit 6 Reference phase data generation circuit 7,8,9,10 Phase Multiplier 11, 12, 13, 14, 15 Carrier multiplier 16 First carrier input terminal 17 Second carrier input terminal 18 Third carrier input terminal 19 Fourth carrier input terminal 20 Fifth carrier input terminal 21 Mixer 22 Transmission signal output terminal 23-hour waveform generator 101 Received signal input terminal 102 sampling circuit 103 Frequency analysis circuit 104 Judgment circuit 105 Differential demodulation circuit 107 Timing offset calculation circuit 112 Frequency conversion circuit 113 Cross-correlation detection circuit 114 Frequency offset calculation circuit

Continuation of the front page (56) Reference JP 60-52147 (JP, A) JP 7-87056 (JP, A) JP 7-143096 (JP, A) JP 7-321762 (JP , A) JP-A-6-216948 (JP, A) JP-A-56-102142 (JP, A) JP-A-8-130563 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) H04L 27/22 H04J 9/00 H04J 11/00

Claims (5)

(57) [Claims] 1. A demodulator for receiving and demodulating a signal in which a plurality of carriers each having a different frequency are simultaneously transmitted, and a sampling means for sampling the received signal and a sampling signal of the sampling means for each carrier. Frequency analyzing means for analyzing, judging means for judging the transmission phase from the analysis output of the frequency analyzing means, and phase difference for detecting the phase difference between the analysis output phase of the frequency analyzing means and the phase value judged by the judging means A demodulation device comprising a detection means and correcting the sampling timing of the sampling means based on the phase difference detected by the phase difference detection means. 2. After demodulating the phase value judged by said judging means, error correction is carried out by error correcting means, said error-corrected demodulated signal is modulated, and a duplicated signal of the phase value judged by said judging means is obtained. 2. The demodulation device according to claim 1, wherein the demodulation device corrects the sampling timing in the sampling means based on the phase difference between the duplicated signal and the analysis output phase of the frequency analysis means. 3. A demodulator for receiving and demodulating a signal in which a plurality of carriers each having a different frequency are simultaneously transmitted, and a frequency conversion for frequency-converting a received signal transmitted at a predetermined frequency into a signal in a predetermined frequency band. Means, sampling means for sampling the signal output by the frequency converting means, frequency analyzing means for frequency-analyzing the sampling signal of the sampling means for each carrier, and determining the transmission phase from the analysis output of the frequency analyzing means. And a cross-correlation detection means for detecting the cross-correlation between the analysis output phase of the frequency analysis means and the phase value judged by the judgment means, and the reception frequency is obtained from the cross-correlation detected by the cross-correlation detection means. Detect the offset and correct the frequency converted by the frequency conversion means by the detected offset Demodulation equipment. 4. The demodulation of the phase value judged by said judging means, error correction by said error correcting means, modulation of said error-corrected demodulated signal, and duplication signal of the phase value judged by said judging means. 4. The demodulation device according to claim 3, wherein the demodulated signal is generated and the frequency converted by the frequency modulation means is corrected based on the cross-correlation between the duplicated signal and the analysis output phase of the frequency analysis means. 5. The demodulator according to claim 1, wherein information is transmitted by a phase difference between a plurality of carriers.