JP3133208B2 - Data receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data receiving apparatus used for a digital car telephone or the like, and more particularly, to a data receiving apparatus which can always obtain accurate decoding.

[0002]

2. Description of the Related Art In phase modulation communication in which information is transmitted by a change in the phase of a carrier, a receiving side converts a baseband signal by synchronous detection by multiplying a received signal by a signal output from an oscillator having the same frequency as the carrier. Demodulated. If there is a deviation between the oscillation frequency of the oscillator and the carrier frequency, an error occurs in decoding. Therefore, in a data receiving apparatus of the phase modulation system, means for causing the oscillation frequency of the oscillator to follow the carrier frequency is provided. Is provided.

As shown in FIG. 6, a conventional data receiving apparatus of this type includes an input terminal 1 for inputting a received signal, a detector 3 for obtaining a baseband signal from the input received signal, and a carrier frequency of the received signal. And a clock regenerator 4 for obtaining a zero-cross signal from the baseband signal output from the detector 3 and generating a reproduction clock signal representing the identification timing of the baseband signal based on the zero-cross signal.
A discriminator 5 for discriminating data transmitted by a baseband signal using the reproduced clock signal generated by the clock regenerator 4, and an output terminal 6 for outputting decoded data.

In this data receiving apparatus, upon receiving a signal, the detector 3 synchronously detects the received signal using a signal having a carrier frequency component of the received signal reproduced by the oscillator 2 and outputs a baseband signal. . If the data to be transmitted is random data, the polarity of the baseband signal changes on average at a time that is 1/2 hour of the identification interval from the data identification time. The clock regenerator 4 detects the zero-cross signal indicating the change in polarity, and uses the zero-cross signal as a reference so that the time difference between the zero-cross signal and the data identification timing is １ ／ of the data identification interval. Generates data identification timing. The discriminator 5 determines whether the baseband signal is positive or negative at the discrimination timing created by the clock regenerator 4, and outputs decoded data from the output terminal 8 based on the result. Further, an error signal at the time of identification in the identifier 5 is fed back to the oscillator 2, and the frequency of the oscillator 2 is controlled so as to follow the carrier frequency.

[0005] In QPSK which is a quaternary phase modulation method,
As shown in FIG. 2, in the phase diagram in which the in-phase component is represented on the I axis and the quadrature component is represented on the Q axis, signal points of the symbols are set at positions respectively rotated by π / 4 from the I axis and the Q axis. The discriminator 5 of the data receiving apparatus determines whether each of the in-phase component and the quadrature component of the received baseband signal is positive or negative. When both the in-phase component and the quadrature component are positive (1, 1), the in-phase component is positive. When the quadrature component is negative, (1, -1), when the in-phase component is negative, when the quadrature component is positive, (-1, 1), and when both the in-phase component and the quadrature component are negative, (-1, 1, -1) ), The signal point of the symbol is identified.

The information to be transmitted is represented by the phase difference between the symbols to be transmitted. For example, the transmitting side sets the phase change amount to π / 2 when representing “00” and the phase change amount when representing “01”. The amount of change is π, the amount of phase change is 0 when representing “10”, and the amount of phase change is − when representing “11”.
Set to π / 2. On the other hand, as shown in FIG. 2, the receiving side identifies symbol (-1, 1) next to symbol (1, 1), that is, + π / 2 from the initial phase of π / 4.
When it is identified that the phase change has occurred, “00” is decoded, and the symbol (−1) follows the symbol (−1, 1).
(1, -1), that is, when the phase change amount of π is identified, “01” is decoded. Similarly, when the phase change amount of 0 is identified, “10”, −π / 2 If the amount of phase change is identified, "11" is decoded.

Such decoding can be performed without error by properly causing the oscillation frequency of the oscillator 2 in the data receiving device to follow the carrier frequency. Therefore, the discriminator 5 detects the detector 3 in the phase diagram.
And outputs an error signal corresponding to the phase difference between the signal point representing the output of
The oscillator 2 controls the oscillation frequency so as to eliminate this error. In this way, when the frequency difference is not large, the oscillation frequency of the oscillator 5 is kept equal to the carrier frequency.

[0008]

However, in the conventional data receiving apparatus, when the frequency deviation Δf between the oscillation frequency of the oscillator and the carrier frequency is larger than ±± of the symbol transmission rate of the transmission data. However, there is a problem that the oscillation frequency of the oscillator cannot follow the carrier frequency, and a large transmission error occurs.

The frequency deviation Δf between the oscillation frequency of the oscillator and the carrier frequency generates a phase error θe of the baseband signal corresponding to θe = 2πΔf / fr (where fr is the symbol transmission rate). Is | △ f | ≧ fr / 8
In this case, the phase error θe becomes π / 4 or more, and the signal point of the baseband signal output from the detector 3 deviates from the quadrant where the original signal point exists on the phase diagram. Therefore, the discriminator 5 erroneously discriminates the signal point, and an incorrect error signal is sent from the discriminator 5 to the oscillator 2, resulting in a large transmission error.

The present invention solves such a conventional problem. The oscillation frequency of an oscillator used for synchronous detection is higher than a carrier frequency by a frequency greater than ± １ ／ of a symbol transmission rate of transmission data. It is an object of the present invention to provide a data receiving device capable of performing correct decoding even when there is a deviation.

[0011]

SUMMARY OF THE INVENTION Therefore, the present invention uses a detecting means for synchronously detecting a phase-modulated received signal using a signal output from an oscillator, and a baseband signal output from the detecting means. and a discrimination means for discriminating the transmission data Te, the data receiving device for controlling the oscillation frequency of the oscillator by using the determination result of the identification means, the transmission side及
And a base obtained by phase-modulating a data sequence known to the receiving side.
The band signal is used as the first reference signal, and
1 / n of the symbol transmission rate of the transmission data
(N is a positive or negative integer)
Providing a band signal as a second reference signal;
The correlation between the baseband signal output from the first and the second reference signal is checked , and the oscillation frequency of the oscillator and the carrier frequency of the received signal are determined based on the highest correlation reference signal. And a reference signal having the highest correlation is the first reference signal.
In this case, the data determined by the identification means is not replaced,
When the reference signal having the highest correlation is the second reference signal,
It is provided with a data replacement means for replacing the discrimination data of the identification means.

In this data receiving apparatus, QPSK
Receive a modulated or π / 4 shifted QPSK modulated signal.

[0013]

Further, the phase modulation of the known data sequence is performed by QPS.
Performed with K or π / 4 shift QPSK.

The data string uses a synchronization word of a TDMA frame.

Further, the oscillator is configured to reproduce a frequency deviated from the carrier frequency of the received signal by at least 1/8 of the symbol transmission rate of the transmission data.

[0017]

Therefore, the oscillator, the detecting means and the identifying means operate in exactly the same manner as in the conventional device. If the frequency deviation between the oscillating frequency of the oscillator and the carrier frequency is greater than ± 1/8 of the symbol transmission rate of the transmission data, the baseband signal correlation detecting means detects it, and the data replacing means detects the discriminating means. Replace the data determined by with the correct data.

The baseband signal correlation detecting means transmits and receives
A baseband signal obtained by phase-modulating a data sequence known on the receiving side, that is, a data sequence such as a synchronization word of a TDMA frame, and 1 / n of a symbol transmission rate of transmission data.
A baseband signal modulated at a frequency (n is a positive or negative integer) is prepared as a reference signal, and the baseband signal output from the detection means when the known data sequence is received, and the prepared reference signal The level of the frequency deviation is detected by examining the correlation with

Further, since the correction means is provided for the data output from the identification means, correct decoding can be obtained even if the oscillation frequency of the oscillator used for synchronous detection deviates from the carrier wave frequency. Accuracy requirements are relaxed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A data receiving apparatus according to an embodiment of the present invention
As shown in FIG. 1, a baseband signal correlator 6 for detecting a correlation between a baseband signal obtained from a received signal of a known data sequence and some reference signals, and a detection result of the baseband signal correlator 6 And a data replacement unit 7 for replacing the output of the discriminator 5 accordingly. The baseband signal correlator 6 calculates the frequency deviation Δf between the oscillation frequency of the oscillator and the carrier frequency based on the reference signal having the highest correlation.
The data replacement unit 7 detects whether the symbol transmission rate fr of the transmission data is equal to or more than 1/8, equal to or less than-／, or in the middle, and the data replacement unit 7 determines that the absolute value of Δf is fr / 8 At this time, the decoding output from the discriminator 5 is converted. Other configurations are the same as those of the conventional apparatus (FIG. 6).

The operation of the data receiving device will be described. When a QPSK-modulated received signal is input from the input terminal 1, the detector 3 synchronously detects the received signal using a signal having a carrier frequency component of the received signal reproduced by the oscillator 2, and outputs a baseband signal. . Clock regenerator 4
Generates a discrimination timing based on the zero cross signal of the baseband signal, and the discriminator 5 discriminates the sign of the baseband signal at this discrimination timing and discriminates a signal point of the symbol. Then, an error signal corresponding to the phase difference between the signal point of the identified symbol and the baseband signal point output from the detector 3 is fed back to the oscillator 2, and the oscillator 2 sets the error signal to zero. Control the oscillation frequency. This series of operations is the same as the operation in the conventional device.

As a result of this control, if the absolute value of the frequency deviation Δf between the oscillation frequency of the oscillator 2 and the carrier frequency is smaller than １ ／ of the symbol transmission rate fr of the transmission data, the oscillation frequency of the oscillator 2 Correctly follows the carrier frequency. Now, the transmitting side sets the phase change amount to π / 2 to represent data “00”, the phase change amount to π to represent “01”, and the phase change amount to 0 to represent “10”.
In order to represent "11", the phase change amount is -π /
2, if the oscillation frequency of the oscillator 2 is controlled correctly, as shown in FIG. 2 (FIG. 2 shows a case where the initial phase is π / 4),
When the transmitted data is “00”, the phase change amount is identified as π / 2, when the transmitted data is “01”, the phase change amount is identified as π, and when the transmitted data is “10”, the phase change amount is identified as 0. And when “11”, the phase change amount is identified as −π / 2,
The correct transmission data is decoded based on the identification.

However, when | △ f | ≧ fr / 8, correct data cannot be decoded only by sending an error signal from the discriminator 5 to the oscillator 5. This is because when the oscillation frequency of the oscillator 2 is higher than the carrier frequency of the received signal by at least fr / 8, a phase error θe exceeding π / 4 occurs between the baseband signal point and the original symbol signal point. Therefore, the discriminator 5 discriminates the signal point of the baseband as a signal point of a symbol shifted by -π / 2. As a result, as shown in FIG. 3, the discriminator 4 sets the phase change amount to π when the transmission data is “01”.
/ 2, when the transmission data is "11", the phase change is identified as π, when the transmission data is "00", the phase change is identified as 0, and when the transmission data is "10". In the case of, the phase change amount is identified as -π / 2. At this time, the discriminator 5 determines that the detector 3 is 1/1 of the symbol transmission rate of the transmission data.
Because we don't know that we are detecting at a frequency higher than 8,
According to the relationship between the normal phase change amount and the data, "01"
The transmission data is decoded to "00", the transmission data of "11" is decoded to "01", the transmission data of "00" is decoded to "10", and the transmission data of "10" is decoded to "11".

Conversely, when the oscillation frequency of the oscillator 2 is lower than the carrier frequency of the received signal by at least fr / 8,
The discriminator 5 discriminates the signal point of the baseband as the signal point of the symbol shifted by + π / 2. as a result,
As shown in FIG. 4, the discriminator 4 determines that the transmission data is “10”.
When the transmission data is “00”, the phase change is identified as π, when the transmission data is “11”, the phase change is identified as 0, When the transmission data is “01”, the phase change amount is identified as −π / 2. Then, according to the normal relationship between the phase change amount and the data, the transmission data of “10” is changed to “00” and “00”
The transmission data of "1" is decoded to "01", the transmission data of "11" is decoded to "10", and the transmission data of "01" is decoded to "11".

The decoding error is removed by the baseband signal correlator 6 and the data permuter 7. First, in the baseband signal correlator 6, three kinds of reference signals obtained by performing different modulations on a known data sequence are prepared in advance, and when the transmitting side transmits the data sequence, the baseband signal correlation The detector 6 calculates a correlation value between the baseband signal of the received signal output from the detector 3 and those reference signals, and detects which reference signal has the highest correlation.

As the known data sequence, as shown in FIG. 5, a synchronization word included in each frame of the data format TDMA communication can be used. The baseband signal correlator 6 converts a baseband signal (referred to as a "first reference signal") obtained by QPSK-modulating the synchronization word as a reference signal, and a symbol transmission rate fr of the transmission data as the first reference signal. And a baseband signal (referred to as a "second reference signal") obtained by modulating the first reference signal at a frequency of -1/4 of the symbol transmission rate fr of the transmission data. Three types of signals, that is, the obtained baseband signal (referred to as “third reference signal”) are prepared.

The baseband signal correlator 6 calculates respective correlation values between the baseband signal output from the detector 3 when the synchronization word is received and the three types of reference signals,
A reference signal having the strongest correlation is detected. Data Replacer 7
Replaces the decoding performed by the discriminator 5 according to the detected reference signal.

When the baseband signal correlator 6 detects the first reference signal as the reference signal having the strongest correlation, the frequency deviation Δf between the oscillating frequency of the oscillator 2 and the carrier frequency is ± fr / 8 or less. In this case, since the discriminator 5 performs correct decoding, the data replacing unit 7 does not perform any replacement, and outputs the decoding of the discriminator 5 to the output terminal 8 as it is. .

When the baseband signal correlator 6 detects the second reference signal as the reference signal having the strongest correlation, the oscillation frequency of the oscillator 2 is higher than the carrier frequency by at least fr / 8 (that is, the oscillation frequency is higher than the carrier frequency). + Fr from frequency
/ 8 or more apart). In this case, as described above, the discriminator 5 sets the transmission data of “01” to “00”, the transmission data of “11” to “01”,
Since the transmission data of “00” is decoded to “10” and the transmission data of “10” is decoded to “11”, the data replacing unit 7 restores the data, that is, the identifier 5 Is "01" when "00" is decoded, "11" when "01" is decoded, and "0" when "10" is decoded.
When "0" is decoded and "11" is decoded, it is replaced with "10" and output from the output terminal 8.

When the baseband signal correlator 6 detects the third reference signal as the reference signal having the strongest correlation, the oscillation frequency of the oscillator 2 becomes fr / 8 than the carrier frequency.
This means that the oscillation frequency is smaller than the carrier frequency (ie, −fr / 8 or more from the carrier frequency). In this case, as described above, the discriminator 5 sets the transmission data of “10” to “00” and the transmission data of “00” to “01”.
The transmission data of “11” is changed to “10”, and the transmission data of “0” is changed to “0”.
Since the transmission data of “1” is decoded to “11”, the data replacing unit 7 restores the transmission data to “11”, that is, to “10” when the discriminator 5 decodes “00”, "01" when "01" is decoded, "11" when "10" is decoded, and "01" when "11" is decoded.
And output from the output terminal 8.

As described above, in the data receiving apparatus of the embodiment, the level of Δf and its sign are detected by the correlation between the baseband signal output from the detector 3 and the reference signal, and Δf Is greater than fr / 8,
By replacing the decoding of the discriminator 5 in accordance with the sign, it is possible to always obtain correct decoding.

Conversely, this means that an oscillator that outputs an oscillation frequency deviated from the carrier frequency by at least fr / 8 can be used for synchronous detection, and the accuracy required for the oscillator is relaxed.

In the embodiment, the case where QPSK-modulated data is received has been exclusively described. However, the data receiving apparatus of the present invention employs π / 4-shift QPSK modulation, that is, at a certain time, on the I and Q axes. An operation of transmitting one of the four symbols and transmitting one of the four symbols on the axis rotated by π / 4 from the I and Q axes at the next time is repeated. The same operation can be performed when receiving data of a modulation scheme for transmitting information according to the phase difference of. Further, even when data of QPSK modulation is handled, a baseband signal obtained by performing a π / 4 shift QPSK modulation on a data sequence can be used as a reference signal prepared in the baseband signal correlator 6. In addition, even when data of π / 4 shift QPSK modulation is handled, a baseband signal obtained by performing QPSK modulation on a data sequence can be used as a reference signal.

Further, by further developing the concept of the embodiment, correct decoding can be obtained even when the frequency deviation Δf between the oscillation frequency of the oscillator and the carrier frequency is further larger.

[0035]

As is clear from the above description of the embodiment, the data receiving apparatus of the present invention can always correct the output of the discriminator to a correct value, and can transmit data by QPSK or π / 4 shift QPSK. Can be decoded without error.

Further, the accuracy required for an oscillator used for synchronous detection can be relaxed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment in a data receiving apparatus of the present invention;

FIG. 2 is a diagram showing correspondence between transmission data and baseband signals (△
f = 0),

FIG. 3 is a correspondence diagram between transmission data and a baseband signal (△
f ≧ π / 4),

FIG. 4 is a diagram showing correspondence between transmission data and baseband signals (△
f ≦ −π / 4),

FIG. 5 is a block diagram showing a data format of a TDMA frame;

FIG. 6 is a block diagram showing a configuration of a conventional data receiving device.

[Explanation of symbols]

 Reference Signs List 1 input terminal 2 oscillator 3 detector 4 clock regenerator 5 discriminator 6 baseband correlator 7 data replacer 8 output terminal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koichi Honma 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (56) References JP-A-2-200043 (JP, A) JP-A-3-248651 (JP, A) JP-A-4-310038 (JP, A) JP-A-3-104454 (JP, A) JP-A-2-2725 (JP, A) JP-A-5-83313 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 27/00-27/38

Claims (5)

(57) [Claims] 1. A detecting means for synchronously detecting a received signal phase-modulated by using a signal output from an oscillator, and an identifying means for determining transmission data using a baseband signal output from the detecting means. A data receiving apparatus for controlling an oscillation frequency of said oscillator using a determination result of said identification means, wherein said data receiving apparatus obtains a data string known to a transmitting side and a receiving side by phase modulation.
The baseband signal obtained as the first reference signal
Further, the baseband signal is transmitted at a symbol transmission rate of transmission data.
Modulated at a frequency of 1 / n of the degree (n is a positive or negative integer)
Prepared baseband signal as a second reference signal
And, a baseband signal outputted from said detection means and before
Investigated the correlation between the serial first and second reference signals, most of the correlation
Baseband signal correlation detection means for detecting a frequency deviation level between the oscillation frequency of the oscillator and the carrier frequency of the received signal based on a high reference signal, and the reference signal having the highest correlation is the first reference signal Place
In this case, replace the data determined by the identification means.
The reference signal having the highest correlation is the second reference signal.
A data replacement unit that replaces data determined by the identification unit when the data is received. 2. The method according to claim 1, wherein the received signal is QPSK modulated or π
2. The data receiving apparatus according to claim 1, wherein the data is phase-modulated by a / 4 shift QPSK modulation method . 3. The phase modulation of the known data sequence is performed by QPS.
K or π / 4 shift QPSK.
The data receiving device according to claim 1 . 4. A TDMA file as the known data string.
2. The method according to claim 1, wherein a frame synchronization word is used.
Or the data receiving device according to 3 . 5. The method according to claim 1, wherein said oscillator is a carrier frequency of a received signal.
Deviated by more than 1/8 of the symbol transmission rate of transmission data
5. The method according to claim 1, wherein the frequency is reproduced.
A data receiving device according to any of the preceding claims .