JP2001057580A - Demodulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in an estimate transmission rate and precision of a frame synchronizing signal. SOLUTION: When a level of a sample timing control signal 107 changes from an L level to an H level for example, a base band signal 103 is sampled and a sampling base band signal 105 is outputted. In this case, when a frequency adjustment signal 109 is, e.g. (n), a value (n) is added to/subtracted from a value set to an operation counter 106A to adjust a period of the operation counter 106A. A frequency offset estimate section 108 uses the sampling base band signal 105 to estimate an offset frequency, a value converting the offset frequency as a count of a sampling timing control section 106 is outputted as a frequency adjustment signal 109 and an update value storage section 106B updates and stores a value in response to the frequency adjustment signal 109.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulator used for a receiver of a digital radio communication system using a time division multiplexing system (hereinafter abbreviated as TDM) or a digital modulation system.

[0002]

2. Description of the Related Art In recent years, research and development of digital mobile communication systems using TDM have been actively conducted. TDM, which uses one frequency band in a time-division manner, requires symbol synchronization and frame synchronization for matching the frequency and phase of a signal on the transmission side and the reception side. As one of means for synchronizing the transmitting side and the receiving side, there is a method of transmitting a known pilot symbol, detecting the pilot symbol at the receiving side, and estimating a frequency and phase shift.

[0003] A conventional demodulator will be described below.

FIG. 8 shows a block configuration of a synchronizing section of a conventional demodulator.

In FIG. 8, reference numeral 801 denotes a quadrature baseband signal obtained by asynchronous quadrature detection of a received signal. 802
Is a pilot signal detection unit for detecting a pilot signal in the received signal, and 803 is the detected pilot signal. Reference numeral 804 denotes a phase detection unit that obtains a phase error between the pilot signal 803 and the known pilot signal 805 and outputs it as a phase signal 806. A frequency detection unit 807 detects a frequency from a temporal change of the phase signal 806. 8
Reference numeral 08 denotes a frequency information, and reference numeral 809 denotes a synchronization signal generation unit that generates a frame synchronization signal 810 and a symbol synchronization signal 811 using the phase signal 806 and the frequency information 808.

The operation of the synchronizing section of the demodulation device configured as described above will be described below.

First, a pilot signal 803 is obtained from an orthogonal baseband signal 801 obtained by asynchronous orthogonal detection of a received signal.
Is detected by pilot signal detection section 802. Next,
A phase error between the detected pilot signal 803 and the known pilot signal 805 is calculated by the phase detection unit 804,
A phase signal 806 is output. In the frequency detector 807,
The frequency is detected from the temporal change of the phase signal 806 and output as frequency information 808. Synchronization signal generator 80
At 9, a frame synchronization signal 810 and a symbol synchronization signal 811 are generated using the phase signal 806 and the frequency information 808. It is also possible to perform frequency offset compensation using the frequency information 808.

[0008]

However, in the above-described conventional configuration, when the received signal includes a large distortion due to multipath fading or the like, the detection speed and accuracy of the pilot signal are reduced, and the frequency deviation of the received signal is reduced. When estimating a phase shift, there is a problem that performance is greatly deteriorated in terms of speed and accuracy.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. In a receiver of a digital radio communication system using TDM, even in a multipath fading environment where a large transmission line distortion exists, the pull-in time is short and the accuracy is low. It is an object of the present invention to provide a demodulator capable of performing high frame synchronization and frequency offset compensation.

[0010]

According to a first aspect of the present invention, there is provided a sampling timing control section for changing a sampling time in accordance with a frequency offset estimated by a frequency offset estimating section; And a sampler for sampling a quadrature baseband signal obtained by asynchronous quadrature detection of a reception modulation wave in accordance with a sampling timing signal.

According to a second aspect of the present invention, there is provided a sampling timing control section for changing a sampling time in accordance with a frequency offset estimated by a frequency offset estimating section, and a sampling section for sampling a reception modulation wave in accordance with a sampling timing signal of the sampling timing control section. And a quadrature demodulator for quadrature demodulating the received modulated wave sampled by the sampler.

A third aspect of the present invention provides a sampling section for periodically sampling a reception modulated wave, and a sampling section for sampling a reception modulation wave at a frequency obtained by adding or subtracting an offset frequency estimated by a frequency offset estimating section to or from an initial set value. And a quadrature demodulation unit for quadrature demodulating.

[0013]

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described.
Will be described with reference to the drawings. FIG.
FIG. 3 is a block connection diagram of the demodulation device according to the first embodiment of the present invention.

In FIG. 1, reference numeral 101 denotes a reception modulated wave, 10
2 is a quadrature demodulation unit that performs quadrature detection on the received modulated wave 101, removes unnecessary signals through a filter and outputs a baseband signal 103, 104 is a sampling unit that samples the baseband signal 103 and outputs a sampling baseband signal 105, Reference numeral 106 denotes a sample timing control unit that supplies a sample timing control signal 107 to the sample unit 104;
Reference numeral 8 denotes a frequency offset estimating unit that estimates an offset frequency using the sampling baseband signal 105 and outputs a value obtained by converting the offset frequency as a counter value of the sampling timing control unit 106 as a frequency adjustment signal 109.

The operation of the demodulation device configured as described above will be described with reference to FIG. First, the received modulated wave 101 is quadrature-detected by a quadrature demodulation unit 102 and an unnecessary signal is removed through a filter or the like (not shown) to become a baseband signal 103. The sampling section 104 samples the baseband signal 103 and outputs a sampling baseband signal 105 when the sampling timing control signal 107 output from the sampling timing control section 106 changes from L to H, for example. At this time, if the frequency adjustment signal 109 output from the frequency offset estimating unit 108 is, for example, n, the sample timing control unit 106 adds or subtracts n to or from the value set in the operation counter 106A, thereby operating The period of the counter 106A is adjusted. When the state of the operation counter 106A becomes 0, for example, the sampling timing control unit 106 changes the sampling timing control signal 107 from L to H, and returns to L after a predetermined time.

A frequency offset estimating unit 108 estimates an offset frequency using the sampling baseband signal 105, outputs a value obtained by converting the offset frequency as a counter value of the sampling timing control unit 106 as a frequency adjustment signal 109, and outputs an operation counter. In order to control the cycle of 106A, a value corresponding to the frequency adjustment signal 109 is updated and stored in the update value storage unit 106B.

Here, the operation of the frequency adjustment signal 109 has been described as a value obtained by converting the offset frequency as a counter value of the sampling timing control unit 106, but when the estimated value of the offset frequency is +, it is +1 or-. Time is -1
In this case, the adjustment takes a long time, but there is a feature that the operation is stable even when the estimated value is significantly wrong.

In the initial operation, the frequency adjustment signal 1
In step 09, a value obtained by converting the estimated value of the offset frequency as the counter value of the sampling timing control unit 106 is used, and after a preset period has passed, or when the estimated value of the offset frequency has become a value equal to or less than a fixed value, It is also possible to shift to the control of +1 and -1. In this case, an operation as a device that converges quickly and has high stability can be expected.

As described above, the frequency adjustment signal 109 has a value such that if the estimated value of the offset frequency is +, the value of the operation counter cycle of the sampling timing control unit 106 becomes longer, and if the estimated value of the offset frequency is −, a value such that the operation counter cycle becomes shorter. A normal operation can be performed by using. Here, the estimated value of the offset frequency is described as + when the sampling frequency is higher than the target frequency, and as − when the sampling frequency is lower than the target frequency.

As described above, according to the present embodiment, by controlling the sampling timing based on the estimated offset frequency, the offset of the sampled baseband signal can be adjusted. This eliminates the need for an integrating portion to remove offset frequency components from the sampled baseband signal,
It is possible to reduce the size of the device. In addition, since the structure does not include an analog unit such as a voltage controlled oscillator (VCO), it can be performed without adjustment. In addition, the entire system can be performed only by digital technology, and a receiving device can be configured more easily than in the past, for example, by integrating them into one chip.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram of a demodulator according to a second embodiment of the present invention.

In FIG. 2, reference numeral 201 denotes a received modulated wave;
2 is a sample unit, 203 is a sampling reception modulated wave, 204
Is a quadrature demodulation unit, 205 is a baseband signal, 206 is a sample timing control unit, 206A is an operation counter, 206
B is an update value storage unit, 207 is a sampling timing control signal,
208 is a frequency offset estimator, and 209 is a frequency adjustment signal. 2 is different from the configuration of FIG.
In FIG. 1, the quadrature demodulation unit 102 is provided before the sample unit 104, and in FIG. 2, the quadrature demodulation unit 204 is provided before the sample unit 102.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, the sample section 202 outputs a sample timing control signal 207 output from the sample timing control section 206.
Is changed from L to H, for example, the received modulated wave 20
1 and outputs a sampling reception modulation signal 203. The sampling reception modulated wave 203 is orthogonally demodulated by an orthogonal demodulation unit 204, and an unnecessary signal is removed through a filter or the like (not shown) to become a baseband signal 205.

The sampling timing controller 206 controls the frequency adjustment signal 2 output from the frequency offset estimator 208
If 09 is, for example, n, the cycle of the operation counter 206A is adjusted by adding or subtracting n to or from the value set in the operation counter 206A. The operation counter 206A changes its state at regular intervals, and when the state becomes, for example, 0, the sampling timing control unit 206A.
Changes the sampling timing control signal 207 from L to H, and returns to L again after a predetermined time.

The frequency offset estimator 208 estimates an offset frequency using the baseband signal 205,
A value obtained by converting the offset frequency as a counter value of the sampling timing control unit 206 is output as a frequency adjustment signal 209, and a value corresponding to the frequency adjustment signal 209 is stored in the update value storage unit 206B to control the cycle of the operation counter 206A. Update and store.

Here, the operation of the frequency adjustment signal 209 has been described as a value obtained by converting the offset frequency as a counter value of the sampling timing control unit 206, but when the estimated value of the offset frequency is +, it is +1 or-. Time is -1
In this case, the adjustment takes a long time, but there is a feature that the operation is stable even when the estimated value is significantly wrong.

In the initial operation, the frequency adjustment signal 2
In step 09, a value obtained by converting the estimated value of the offset frequency as the counter value of the sampling timing control unit 206 is used, and after a preset period has elapsed, or when the estimated value of the offset frequency has become a value equal to or less than a predetermined value, It is also possible to shift to the control of +1 and -1. In this case, an operation as a device that converges quickly and has high stability can be expected.

As described above, the frequency adjustment signal 609 has a value such that the operation counter cycle of the sampling timing control unit 606 becomes longer if the estimated value of the offset frequency is +, and a value such that the operation counter cycle becomes shorter if the estimated value is −. A normal operation can be performed by using. Here, it is described that the estimated value of the offset frequency is + when the current sampling frequency is higher than the target frequency and − when the current sampling frequency is lower than the target frequency.

As described above, according to the present embodiment, by controlling the sampling timing based on the estimated offset frequency, the offset of the sampled baseband signal can be adjusted. This eliminates the need for an integrating portion to remove offset frequency components from the sampled baseband signal,
It is possible to reduce the size of the device. In addition, since the structure does not include an analog unit such as a voltage controlled oscillator (VCO), it can be performed without adjustment. In addition, the entire system can be performed only by digital technology, and a receiving device can be configured more easily than in the past, for example, by integrating them into one chip.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram of a demodulator according to a third embodiment of the present invention.

In FIG. 3, reference numeral 302 denotes a sampler which samples the reception modulation wave 301 at a predetermined period and outputs a sampling reception modulation wave 303. A quadrature demodulation unit 304 controls the frequency of quadrature demodulation based on the offset frequency. The quadrature demodulation unit 304 updates the phase with a correction value and an initial value based on a frequency adjustment signal, which will be described later, and updates the cosine value and the sine value corresponding to the phase information from the phase update unit 304A. The generated orthogonal rotator 304B includes multipliers 304C and D for multiplying the sampling reception modulated wave 303 by a cosine value and a sine value output from the orthogonal rotator 304B. Reference numeral 306 denotes a frequency offset estimating unit that estimates a frequency offset frequency based on the baseband signal 305 output from the orthogonal demodulation unit 304, and outputs a frequency adjustment signal 307 to the orthogonal demodulation unit 304.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, the sampling section 302 samples the reception modulation wave 301 at regular intervals and outputs a sampling reception modulation wave 303. Next, the quadrature demodulator 304 adds or subtracts the value of the frequency adjustment signal 307 output from the frequency offset estimator 306 to the preset phase update value for each sampling timing to update the phase. That is, in the orthogonal rotator 304B, a cosine (hereinafter abbreviated as cos) value and a sine (hereinafter abbreviated as sin) corresponding to the phase information obtained from the phase updating unit 304A.
And generate a value. Then, the above-described cos value and s are added to the sampling reception modulation signal 303 output from the sample section 302.
After multiplying the in value by the multipliers 304C and D, unnecessary signals are removed by a filter or the like (not shown), and then output as a baseband signal 305.

Next, the frequency offset estimating section 306 estimates the offset frequency using the baseband signal 305, converts the offset frequency as a phase update value of the phase update section 304 A of the quadrature demodulation section 304, and converts it into a frequency adjustment signal 307. Output.

Here, the operation of the frequency adjustment signal 307 has been described as a value obtained by converting the offset frequency into a phase update value of the quadrature demodulation section 304. However, when the estimated value of the offset frequency is +, it is +1 or-. At this time, the operation may be performed as −1. In this case, it takes a long time to adjust, but there is a feature that the operation is stable even when the estimated value is significantly wrong.

In the initial operation, the frequency adjustment signal 3
07, a value obtained by converting the estimated value of the offset frequency as the phase update value of the quadrature demodulation unit 304 is used. When a preset period has passed, or when the estimated value of the offset frequency becomes a value equal to or less than a certain value, as described above. It is also possible to shift to the control of +1 and -1. In this case, an operation as a device that converges quickly and has high stability can be expected.

As described above, as the frequency adjustment signal 307, a value that decreases the phase update of the quadrature demodulation unit 304 when the estimated value of the offset frequency is +, and a value that increases the phase update when the estimated value is − is used. And normal operation is possible.

Here, it is described that the estimated value of the offset frequency is + when the frequency of the current sampled signal is higher than the target frequency, and is-when the frequency is lower than the target frequency.

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of the demodulation device according to the first embodiment of the present invention.

In FIG. 4, reference numeral 401 denotes an orthogonal baseband signal obtained by asynchronous quadrature detection of a received modulation wave, and 402 denotes a difference vector obtained by taking a difference between the orthogonal baseband signal 401 and a signal corresponding to one symbol of the reception modulation wave. A differential vector generator 403 for continuously generating and normalizing one or more symbols per symbol, 403 is a differential vector signal output from the differential vector generator 402, 404 is a normalized differential vector signal 403 and a known differential vector signal 405. 407 is a vector correlation unit for calculating a variance value 408 from the frame sequence correlation signal 406,
Is a comparison unit that compares the variance value 408 and the variance reference value 409, 411 is a comparison signal, 412 is a correlation threshold value determination unit that determines a correlation threshold value 413 from the comparison signal 411 that is a comparison result of the comparison unit 410, 414 is a vector correlation unit 40
4 is a frame synchronization signal generation unit that compares the magnitude of the vector correlation signal 406 output from 4 with a correlation threshold 413 to generate a frame synchronization signal 415.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, an orthogonal baseband signal 401 obtained by orthogonally detecting a received signal is input to a difference vector generating section 402. The difference vector generation unit 402 generates a difference vector signal 403 by normalizing the vector product of the complex conjugate of the orthogonal baseband signal one symbol before and the current orthogonal baseband signal 401, and performs sampling of the orthogonal baseband signal 401. Output continuously every hour.

Next, the vector correlation section 404 calculates the vector correlation signal 406 by accumulating the vector product of the difference vector signal 403 and the known difference vector 405. Then, in the frame synchronization signal generation section 414, the vector correlation signal 4 output from the vector correlation section 404 is output.
06 is compared with the correlation threshold 413 to generate a frame synchronization signal 415.

On the other hand, the variance calculator 407 calculates a variance 408 from the vector correlation signal 406. The variance value 408 is compared with a preset variance reference value 409 by a comparison unit 410, and the variance value 408 is compared with the variance reference value 4
When the variance value 408 is smaller than the variance reference value 409, “1” is assigned to the comparison signal 411.
Output as When the comparison signal 411 is “1”, the correlation threshold value determining unit 412
13 is decreased by a preset ratio, and when the comparison signal 411 is "0:", the correlation threshold value 413 is increased by a preset ratio. Here, the rate at which the correlation threshold value 413 is changed may be an amount to be adjusted or a rate to be multiplied or divided.

As described above, according to the present embodiment, the distribution calculation unit 40
7, a comparing unit 410 and a correlation threshold value determining unit 412 are provided,
When the variance value 408 of the vector correlation signal 406 output from the vector correlation section 404 exceeds a preset variance reference value 409, the correlation threshold value 413 is decreased, and when the variance value 408 does not exceed the variance reference value 409, the correlation threshold value 413 is increased. In a multipath fading environment where large transmission line distortion exists, even when the absolute value of vector correlation fluctuates greatly, the correlation threshold is set adaptively to acquire fast and stable frame synchronization. It can be carried out.

Reference Example 2 Hereinafter, a second reference example of the present invention will be described with reference to the drawings. FIG. 5 is a block connection diagram of the demodulation device according to the second embodiment of the present invention.

In FIG. 5, reference numeral 501 denotes a quadrature baseband signal obtained by asynchronous quadrature detection of a received modulated wave; 502, a differential vector generator; 503, a differential vector signal; 504, a vector correlator; 505, a known differential vector sequence signal;
06 is a vector correlation signal, 507 is a maximum value detection unit, 10
8 is a detected maximum value, 509 is a comparison unit, 510 is a comparison signal, 511 is a correlation threshold value determination unit, 512 is a correlation threshold value, 513 is a frame synchronization signal generation unit, 514 is a generated frame synchronization signal, This is substantially the same as the basic configuration shown in FIG.

FIG. 5 is different from the configuration of FIG.
First, instead of the configuration in which the variance 108 is calculated by the variance calculator 107 from the vector correlation signal 106 output from the vector correlator 104 in FIG. 4, the output is the output of the vector correlator 504 in FIG. Vector correlation signal 506
Is that the maximum value 508 is detected by the maximum value detection unit 507.

Second, in FIG. 4, the comparison unit 1
Instead of the configuration in which the variance reference value 109 is input as one input of the reference 10, the correlation threshold 512 output by the correlation threshold determination unit 511 as one input of the comparison unit 509 in the configuration of FIG. The point is that the comparison is made with the maximum value 508 detected by the value detection unit 507.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, an orthogonal baseband signal 501 obtained by orthogonally detecting a received signal is input to a difference vector generating section 502. The difference vector generation unit 502 generates a difference vector signal 503 by normalizing the vector product of the complex conjugate of the orthogonal baseband signal one symbol before and the current orthogonal baseband signal 501, and samples the orthogonal baseband signal 501. Output continuously every hour.

Next, the vector correlation section 504 accumulates the vector product of the difference vector signal 503 and the known difference vector 505 to obtain the vector correlation signal 506.
Is calculated. In the frame synchronization signal generation unit 513, the vector correlation signal 50 output from the vector correlation unit 504 is output.
6 is compared with a correlation threshold 512 to generate a frame synchronization signal 514.

On the other hand, among the vector correlation signals 506, the one having the largest absolute value in one frame period is detected by the maximum value detection section 507, and the information is output as the maximum value 508.

The maximum value 508 and the correlation threshold value 512
Are compared by the comparison unit 509, and when the maximum value 508 is larger than the correlation threshold value 512, “1” is set. When the maximum value 508 is smaller than the correlation threshold value 512, “0” is set.
Output as 10. In the correlation threshold value determination unit 511,
When the comparison signal 510 is “1”, the correlation threshold value 512
Is increased by a preset ratio, and the comparison signal 51 is increased.
When 0 is "0", the correlation threshold value 512 is reduced by a preset ratio. Here, the correlation threshold 5
The rate at which 12 is changed may be the amount of addition or subtraction, the rate of multiplication / division, or the value obtained by multiplying the difference between the maximum value 508 and the correlation threshold value 512 by a fixed rate.

As described above, according to the present embodiment, the maximum value detecting section 50
7, a comparison unit 509 and a correlation threshold value determination unit 511 are provided;
When the maximum value 508 in one frame period of the vector correlation signal 506 output from the vector correlation section 504 exceeds the current correlation threshold 512, the correlation threshold 512
In a multipath fading environment where a large transmission line distortion is present in the received signal, even when the absolute value of the vector correlation greatly fluctuates, the By setting a value, fast and stable acquisition of frame synchronization can be performed.

Reference Example 3 Hereinafter, a third reference example of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram of the demodulation device according to the third embodiment of the present invention.

In FIG. 6, reference numeral 601 denotes a quadrature baseband signal obtained by asynchronous quadrature detection of a received modulated wave; 602, a differential vector generator; 603, a differential vector signal; 604, a vector correlator; 605, a known differential vector sequence signal;
06 is a vector correlation signal, 607 is a variance calculator, 608
Is a calculated dispersion value, 609 is a dispersion reference value, 610 is a comparison unit, 611 is a comparison signal, 612 is a waveform equalization unit, and 613 is a waveform-equalized orthogonal baseband signal. In FIG. 6, the difference from the configuration of FIG.
12 and an equalizer 612 instead of the frame synchronization signal generator 414 to output an equalized signal 613.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, an orthogonal baseband signal 601 obtained by orthogonally detecting a received signal is input to a difference vector generating section 602. The difference vector generation unit 602 generates a difference vector signal 603 by normalizing the vector product of the complex conjugate of the orthogonal baseband signal one symbol before and the current orthogonal baseband signal 601, and samples the orthogonal baseband signal 601. Output continuously every hour.

Next, the vector correlation unit 604 calculates the vector correlation signal 606 by accumulating the vector product of the difference vector signal 603 and the known difference vector 605. Further, a variance value 608 is calculated from the vector correlation signal 606 by a variance calculator 607. The variance value 60
8 and the preset dispersion reference value 609
When the variance value 608 is larger than the variance reference value 609, “1” is set.
If smaller, “0” is output as the comparison signal 611.

When the comparison signal 611 is "1", the waveform equalization section 612 performs waveform equalization using the orthogonal baseband signal 601. When the comparison signal 611 is "0", the waveform equalization section 612 does not perform waveform equalization and performs orthogonal equalization. The band signal 601 is output as it is.

As described above, according to the present embodiment, the distribution calculation unit 60
7, a comparison unit 610 and a waveform equalization unit 612, and the variance 608 of the vector correlation signal 606 output from the vector correlation unit 604 is set to a predetermined variance reference value 609.
Is exceeded, the waveform equalizer 612 is operated to perform waveform equalization, and when it is not exceeded, the orthogonal baseband signal 601 is passed as it is without performing waveform equalization. In a multipath fading environment that fluctuates with the above, it is possible to avoid deterioration of the error rate characteristics due to the waveform equalizer when the delay dispersion of the received signal is small.

Reference Example 4 Hereinafter, a fourth reference example of the present invention will be described with reference to the drawings. FIG. 7 is a block connection diagram of the demodulation device according to the fourth embodiment of the present invention.

In FIG. 7, reference numeral 701 denotes a quadrature baseband signal obtained by asynchronous quadrature detection of a reception modulation wave, and 702 denotes a difference vector obtained by taking the difference between the quadrature baseband signal 701 and a signal of one symbol of the reception modulation wave. A difference vector generator 703 that continuously generates and normalizes one or more symbols per symbol, 703 is a difference vector signal output from the difference vector generator 702, 704 is a normalized difference vector signal 703 and a known difference vector sequence signal 705. And a vector sequence correlation signal 706
707 generates a frame synchronization signal 708 from the frame sequence correlation signals 706 and 714, and corrects the phase of the frame synchronization signal 708, and 709 outputs a quadrature based on the frame synchronization signal 708. A waveform equalizer for performing waveform equalization control of the baseband signal 701, 710 is a waveform-equalized orthogonal baseband signal, 711 is a complex conjugate of the waveform-equalized orthogonal baseband signal one symbol before and the current waveform, etc. A difference vector generator 712 for generating a difference vector signal 712 by normalizing a vector product of the transformed orthogonal baseband signal 710;
Reference numeral 3 denotes a vector correlating unit which performs vector sequence correlation between the normalized difference vector signal 712 and the known difference vector sequence signal 705 to generate a frame sequence correlation signal 714.

The operation of the demodulation device configured as described above will be described with reference to FIG.

First, an orthogonal baseband signal 701 obtained by orthogonally detecting a received signal is input to a difference vector generating section 702. The difference vector generation unit 702 generates a difference vector signal 703 by normalizing the vector product of the complex conjugate of the orthogonal baseband signal one symbol before and the current orthogonal baseband signal 701, and samples the orthogonal baseband signal 701. Output continuously every hour.

Next, the vector correlation section 704 compares the difference vector signal 703 with the known difference vector sequence signal 70.
The vector correlation signal 706 is calculated by accumulating the vector product of 5. Then, the frame synchronization signal generation unit 707 generates a frame synchronization signal 708 using the vector correlation signal 706.

The waveform equalizer 709 outputs the orthogonal baseband signal 701 at the timing of the frame synchronization signal 708.
And outputs a waveform-equalized orthogonal baseband signal 710.

Next, the difference vector generation unit 711
The complex conjugate of the waveform-equalized orthogonal baseband signal before the symbol and the current waveform-equalized orthogonal baseband signal 710
Are normalized to generate a differential vector signal 712, which is continuously output during the training period of the waveform equalizer 709. Then, the vector correlation unit 71
In 3, the vector correlation signal 714 is calculated by accumulating the vector product of the difference vector signal 712 and the known difference vector sequence signal 705. The frame synchronization signal generation unit 707 performs phase correction of the frame synchronization signal using the vector correlation signal 714.

According to this embodiment, the frame synchronization signal generator 707, the waveform equalizer 709, the difference vector generator 711, and the vector correlator 713 are provided.
9, a vector correlation signal 714 is generated from the orthogonal baseband signal 710 whose waveform has been equalized, and the phase of the frame synchronization signal 708 is finely adjusted by the frame synchronization signal generation unit 707, whereby the delay dispersion of the received signal varies with time. In a multipath fading environment, it is possible to adaptively optimize the phase of a frame synchronization signal for operating the waveform equalization unit.

In this embodiment, the difference vector generator 7
11 and the vector correlation unit 713, and the difference vector generation unit 7
02 and the vector correlation unit 704 are provided separately, but since the operation is the same, a configuration in which they are integrated into one is also possible.

As described above, the frequency offset of the baseband signal can be adjusted by controlling the frequency of the quadrature demodulation based on the estimated offset frequency. Since the frequency adjustment is performed using the phase information, fine adjustment can be performed for the adjustment of the frequency offset. Also,
When the intermediate frequency (IF) sampling frequency is set to eight times or more of the symbol frequency, an integration part in the quadrature demodulation unit is required, so that the circuit is not practically increased by also using the frequency correction.

Further, since it has a structure without an analog section such as a voltage controlled oscillator (VCO), it can be performed without adjustment. The whole system can be performed only by digital technology, and the receiving device can be configured more easily than in the past, for example, by being integrated into one chip.

[0075]

As described above, according to the present invention, the sampled baseband signal is changed by sequentially changing the sample timing of the received orthogonal baseband signal in accordance with the difference (offset frequency) between the sample frequency and the target frequency. Can be removed, thereby enabling demodulation in a receiving system having a sample frequency different from the target frequency.

Further, by sequentially changing the sampling timing of the received modulated signal according to the difference (offset frequency) between the sample frequency and the target frequency, the offset of the sample modulated signal, that is, the offset in the baseband signal is removed. To be able to
Demodulation in a receiving system having a sample frequency different from the target frequency becomes possible. In addition, although the removal of the offset frequency in the baseband signal requires an integration operation, the present invention does not need the offset frequency because the offset frequency is removed by adjusting the sampling timing. This contributes to downsizing of the device.

The offset frequency in the baseband signal is removed by converting the received and sampled modulated signal into a baseband signal by integration with a quadrature rotator controlled by an offset frequency estimated from the baseband signal. It is possible to do. In addition, since the adjustment for the frequency offset is performed using the phase information, the control can be finely performed, and a high frequency offset removal capability is provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a demodulation device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a demodulator according to a second embodiment of the present invention.

FIG. 3 is a block connection diagram of a demodulation device according to a third embodiment of the present invention.

FIG. 4 is a block connection diagram of a demodulation device according to a first reference example of the present invention;

FIG. 5 is a block connection diagram of a demodulation device according to a second reference example of the present invention;

FIG. 6 is a block connection diagram of a demodulation device according to a third reference example of the present invention.

FIG. 7 is a block diagram of a demodulation device according to a fourth embodiment of the present invention;

FIG. 8 is a block diagram of a conventional demodulator;

[Explanation of symbols]

102, 204, 304 Quadrature demodulators 104, 202, 302 Samplers 106, 206 Sample timing controllers 108, 208, 306 Frequency offset estimators 402, 502, 602, 702, 711 Difference vector generators 404, 504, 604, 704, 713 Vector correlation unit 407, 607 Variance calculation unit 410, 509, 610 Comparison unit 412, 511, 602 Correlation threshold determination unit 414, 513, 707 Frame synchronization signal generation unit 507 Maximum value detection unit 612, 709 Waveform, etc. Conversion section 802 pilot signal detection section 804 phase detection section 807 frequency detection section 809 synchronization signal generation section

Claims (3)

[Claims] 1. A sampling timing control section for changing a sampling time in accordance with a frequency offset estimated by a frequency offset estimating section, and a quadrature baseband obtained by asynchronous quadrature detection of a received modulated wave according to a sampling timing signal of the sampling timing control section. A demodulation device comprising: a sample section for sampling a signal. 2. A sample timing control section for changing a sampling time in accordance with a frequency offset estimated by a frequency offset estimating section; a sample section for sampling a reception modulation wave according to a sampling timing signal of the sample timing control section; And a quadrature demodulation unit for quadrature demodulating the received modulated wave sampled by the unit. 3. A quadrature demodulation of a sampled reception modulated wave at a frequency obtained by adding or subtracting an offset frequency estimated by a frequency offset estimator to or from an initial setting value, and a sampling unit for periodically sampling the reception modulation wave. A demodulation device comprising a quadrature demodulation unit.