JPS643380B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] In data transmission using quadrature amplitude modulation, the present invention transmits a training sequence prior to data transmission and uses an automatic equalizer without making a sequence determination. The present invention relates to a data transmission/reception device that sets tap gain to an optimal value.

[Prior art]

Conventionally, when initially setting the tap gain of an automatic equalizer, a method has been widely used in which a binary pseudorandom sequence is transmitted prior to information transmission, and the tap gain is successively set to the optimal value by determining this. However, in a transmission system where inter-symbol interference is extremely large, binary determination cannot be said to be accurate, and therefore, there may be problems with setting using the conventional method. On the other hand, a short pseudo-random sequence with a period equal to the length of the delay line of the automatic equalizer is transmitted, the same sequence is asynchronously generated on the receiving side, and the tap gain is determined using this as a reference signal. A method has been proposed in which the desired settings are made by cyclically permuting tap gains, but this method requires generation of a special signal sequence and is not common.

In order to improve the above-mentioned drawbacks, prior to the pseudo-random sequence, a binary repeating sequence is transmitted for the purpose of extracting the carrier wave and timing frequency, and the properties of this sequence are used to differentiate between the pseudo-random sequence generated on the receiving side and Frame synchronization with the transmitted pseudorandom sequence is achieved within a sufficiently small deviation range compared to the delay line length of the automatic equalizer, and the pseudorandom sequence generated on the receiving side is used as a reference signal without using any judgment. , a method has been proposed in which the tap gain of an automatic equalizer is set to an optimal value. (Refer to Japanese Unexamined Patent Publication No. 1989-89407).

[Problem that the invention seeks to solve]

However, in this method, the phase of the demodulated carrier wave used for coherent detection must be controlled on the receiver side while receiving the binary repeated sequence. That is, it is necessary to include a carrier phase control device.

An object of the present invention is to synchronize a pseudorandom sequence generated at a receiver with a pseudorandom sequence arriving from a transmitter without providing a carrier phase control device, even in a transmission system with large code interference. An object of the present invention is to provide a data transmission transmitter/receiver that can correctly correct the tap gain of an automatic equalizer.

〔principle〕

First, the principle of the present invention will be explained. First, as an example of a binary repetitive signal to be transmitted prior to a pseudorandom sequence, on a two-dimensional plane in which in-phase and orthogonal components are expressed by two mutually orthogonal axes, the values shown at points a and b in Fig. 1 are used. Let's consider a system that alternately sends out every T seconds. Now, when this signal is transmitted for a sufficiently long period of time through a system having an impulse response of an in-phase component x(t) and a quadrature component y(t), we will calculate the real part and imaginary part of the complex number, respectively. Letting z(t) correspond to the part, z(t) is expressed as follows.

z(t)=[A _∞ 〓 ^{k=-∞ X} (t-2kT)+B _∞ ^〓 k=-∞ The coordinates of point a and point B when Figure 1 is regarded as a complex plane, It is a phase difference.

Here, considering the signal W(t)=Z(t)+Z(t-T), t= of W(t) and X(t)
Let the sample values at nT be Wn and Xn respectively
Then, Wn=e ^j 〓(A+B) _∞ 〓 ^k=-∞ Xk=e _j 〓(A+B) D ₀ ...(2) (However, D ₀ is the DC gain). In other words, if the DC gain is normalized to 1, Wn is always at point c in Figure 1 when there is no noise.
The value rotated by

Next, create a pseudo-random sequence, for example, by placing "0" at point e and "1" at point d in the binary sequence with a period of 127 generated by the 7-stage maximum long period sequence generator shown in Figure 2. It is assumed that the respective series are made to correspond to each other, and the initial state of the shift register in FIG. 2 is set to "0101010". In this case, following the repetition of AB, a pseudorandom sequence is sent out, and the sequence that is sent out is as follows.

ABABDEDEDEDEEE... However, D and E are the coordinates of point d and point e when Fig. 1 is regarded as a complex plane. Further, the transition position from the AB repetition to the pseudo-random sequence may be set in advance to the same position in the transmitter and receiver.

On the other hand, if DE continues to be repeated, Wn=e ^j 〓(D+E) _∞ 〓 ^k=-∞ Xk=e ^j 〓(D+E)D ₀ ...(3). If the DC gain is normalized to 1 in the same manner as described above, Wn will be a value obtained by rotating the point f in FIG. 1 by θ. Therefore, after repeated signals of AB
If the pseudo-random sequence starting with DEDEDEDEEE... continues, W(t) is e ^j 〓(A+B) to e ^j 〓(D+E)
Move to the point.

Here, let P=e ^j 〓(A+B) Q=e ^j 〓(D+E) and consider a signal R=P ^* Q. However, P ^* is P
is the conjugate value of That is, R=P ^* Q = {e ^j 〓(A+B)} ^* {e ^j 〓(D+E)} = e ^-j 〓(A+B) ^* e ^j 〓(D+E) =(A+B) ^* (D+E) =( −j) ^* (j)=−1. Similarly, considering the signal R′=P ^* P, R′=P ^* P = {e ^j 〓(A+B)} ^* {e ^j 〓(A+B)} = (A+B) ^* (A+B) = (- j) ^* (-j) = 1 Similarly, the signal R″=Q ^* Q is R″=Q ^* Q = {e ^j 〓(D+E)} ^* {e ^j 〓(D+E)} = (D+E) ^* (D+E) = (j) ^* (j) = 1. Therefore, the real part of Wn*−k Wn is R _e [W
n*-kWk], and considering a signal as Sn=Re[Wn*-k Wn], and applying it to the case where the signal sequence "...ABABDEDEDEDEEE..." is sent, when k=1, the above Sn becomes "... 1, 1, 1, -1, 1, 1, 1, 1, 1,
1,...", and when k=2, "=1, 1, 1, -1, -1, 1, 1, 1, 1,
1,…”, and when k=7, “…1, 1, 1, -1, -1, -1, -1, -1, -
1, -1,...”.

Therefore, by detecting the point in time when this signal changes from positive to negative, it is possible to know with an error of at most ±1 time slot that a random sequence starting with DE has been received. Therefore, if we drive the maximum long period sequence generator on the receiving side (the same generator as shown in Figure 2, and the initial state is set to "0101010") at the time of code conversion of this signal, we get the following: It is possible to create a synchronized sequence on the receiving side with a deviation of at most ±1 time slot from the transmitted sequence. If you use this to correct the tap gain of the automatic equalizer, the optimum tap gain that has the maximum value of the tap gain at the center tap of the initially set delay line or the taps before and after it will be much more effective than when using judgment. can be reached at high speed.

The present invention is based on the above-mentioned principle, and includes:
In a data transmission device using quadrature amplitude modulation including polyphase phase modulation and polyphase multilevel modulation, there is provided a means for transmitting a repetitive signal prior to data transmission, and a means for transmitting a maximum long period sequence within one period after transmitting the repetitive signal. means for transmitting from a preset timing; a synchronous detector for two-axis synchronous detection of the transmission signal; and a means for transmitting a complex signal having an in-phase component as a real part and a quadrature component as an imaginary part of the output signal of the synchronous detector for a certain period of time. a first delay element that delays, a complex adder that sums the output signal of the first delay element and the output signal of the synchronous detector, and a second delay that delays the output of the complex adder for a certain period of time. a complex conjugate signal generator that generates a complex conjugate signal of the signal delayed by the delay element; and a complex multiplier that multiplies the output of the complex conjugate signal generator and the output of the complex adder. ,
a real part generator for extracting the real part of the output of the complex multiplier; and a maximum long-period sequence transmitted by the output signal of the real part generator that is synchronized within a certain time deviation. The method includes means for generating a long-period sequence, and means for setting the tap gain of an automatic equalizer to an optimal value without using the generated maximum long-period sequence to determine the transmission sequence. A feature of the present invention is that the tap gain of the automatic equalizer can be quickly set to an optimal value even when a significantly large transmission line is used.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention. The upper part of the broken line is the transmitter, and the lower part is the receiver. In the transmitter, the repetitive signals at points a and b in FIG. It is sent out to the line 4 through the switch 3. When the counter reaches a predetermined value, the input side of the switch 3 is switched and connected to the maximum long period sequence generator 5, and the maximum long period sequence generator 5 is connected to the line 4, and the maximum long period sequence starting from the repetition of points d and e in FIG. Sent out. This is counted by a counter 6 and sent out until the number of maximum long period sequences reaches a predetermined value. When the counter 6 reaches a predetermined value, the switch 3 is connected to the transmission data generator 7, and data is transmitted to the line 4 from this point on. The above series of signal sequences is orthogonally amplitude modulated by the modulator 8 and sent out to the transmission line through the terminal 9.

The signal on this transmission path enters the receiver through a terminal 10 and is detected by a synchronous detector 11. The reference phase of this synchronous detector 11 is a demodulated carrier wave whose phase is not controlled with respect to the transmission carrier wave coming from the transmission path, and this is used to perform two-axis synchronous detection. The demodulated carrier wave and the in-phase output of the synchronous detector 11 are the real part, and the detected output by the orthogonal carrier wave is the imaginary part. That is, the output of the synchronous detector 11 is a complex number. This output and this output are connected to the first delay element 1
2 and the signal delayed by T seconds through complex adder 1.
Add by 3. The output of the complex adder 13 is (2)
Corresponds to Wn in formula or formula (3).

Next, the output of the complex adder 13 is delayed by, for example, 7T seconds through the second delay element 14, and the conjugate signal generator 15 outputs a conjugate value. That is, the output value of the conjugate signal generator 15 is Wn*-7. The output value Wn of the complex adder 13 and the output value Wn*-7 of the conjugate signal generator 15 are multiplied by the complex multiplier 16 to obtain Wn*-7 Wn.
The output signal of the complex multiplier 16 is input to a real part generator 17, which outputs the real part. The output signal of the real part generator 17 is Sn=Re[Wn*-Wn].

Next, the output signal of the real part generator 17 is input to the polarity determination circuit 18, which generates a pulse when the polarity of the input signal is reversed from positive to negative, and generates a pulse using the maximum length period sequence generator 19. Start. The maximum long period sequence generator 19 has the configuration shown in FIG. 2 described above, and its initial value is set to "0101010". The output signal of this sequence generator 19 is
It is sent to the signal line 21 via the switch 20 and used to correct the tap gain of the automatic equalizer 22. The output signal of the synchronous detector 11 is input to the automatic equalizer 22, which corrects the tap gain according to the output signal of the sequence generator 19 and outputs an automatic equalizer. In this case, as mentioned above, the output signal of the synchronous detector 11 and the output signal of the maximum long period sequence generator 19 are synchronized with a difference of at most one time slot, so it is possible to quickly correct the tap gain. be. Furthermore, even if the intersymbol interference in the transmission system is large, by modifying the tap gain, it is possible to obtain an output signal with reduced intersymbol interference. Then, the counter 23 counts the number of output signals from the maximum long-period sequence generator 19, and when it reaches a predetermined number, switches the switch 20 to connect the signal to the output of the determiner 24 connected to the automatic equalizer output terminal. do.

Here, the operations of the polarity determination circuit 18 and the maximum long period sequence generator 19 will be explained in more detail. FIG. 4 is an operation time chart based on the output Zn of the synchronous detector 11. The output Sn of the real part generator 17 is determined when Wn is A as described in the explanation of the principle above.
When +B, it is positive, and when it becomes D+E, it becomes negative. Therefore, by inputting the signal Sn to the polarity determination circuit 18, the polarity determination circuit 18 sends out an output pulse T when the signal Sn changes from positive polarity to negative polarity. This output pulse T activates the maximum long period sequence generator 19, and outputs the maximum long period sequence Pn as shown in FIG.

Tap gain setting of the automatic equalizer 22 is performed according to this maximum long period sequence Pn. Since this is well known, detailed explanation will be omitted.

After this, as mentioned above, the transmission data is sent from the transmission data generator 7 of the transmitter, and the receiver uses judgment as in the past to keep the automatic equalizer in the optimal state and remove intersymbol interference. data signal can be obtained.

〔Effect of the invention〕

As described above, in the present invention, the maximum length period sequence is transmitted following the repetitive signal, and the receiver detects the sign conversion point of the signal obtained by predetermined calculation of the received signal, thereby converting the maximum length period sequence. start point 1
The system is configured to detect errors within the time slot and correct the tap gain of the automatic equalizer using the maximum long period sequence generated on the receiving side.
The demodulated carrier wave on the receiving side does not need to be phase-controlled by the carrier wave on the transmitting side, and the tap gain of the automatic equalizer is corrected to the optimum value, allowing data transmission with inter-symbol interference removed even in transmission systems with large inter-symbol interference. became possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a training sequence transmission signal on a two-dimensional plane. FIG. 2 is a diagram showing an example of the configuration of a maximum long period sequence generator. FIG. 3 is a block diagram showing one embodiment of the present invention. Figure 4 is an operation time chart. In the figure, 1...repetitive signal generator, 2,
6,23...Counter, 3,20...Switch,
5, 19... Maximum long period sequence generator, 7... Transmission data generator, 8... Modulator, 11... Synchronous detector, 12... First delay element, 13... Complex adder, 14 ... second delay element, 15 ... complex conjugate signal generator, 16 ... complex multiplier, 17 ... real part generator, 18 ... polarity determination circuit, 22 ... automatic equalizer, 24 ... Judgment device.

Claims (1)

[Claims] 1. A data transmission transmitting/receiving device using quadrature amplitude modulation including polyphase phase modulation and polyphase multilevel modulation, comprising: means for transmitting a repetitive signal to a transmitter prior to data transmission; followed by means for transmitting the maximum long period sequence from a preset timing within one cycle, and the receiver includes a synchronous detector that performs two-axis synchronous detection of the transmitted signal, and an in-phase of the output signal of the synchronous detector. a first delay element that delays a complex signal having a real part and an orthogonal component as an imaginary part for a certain period of time; and a complex adder that sums the output signal of the first delay element and the output signal of the synchronous detector. a second delay element that delays the output of the complex adder for a certain period of time; a complex conjugate signal generator that generates a complex conjugate signal of the signal delayed by the delay element; and the complex conjugate signal generator. a complex multiplier that multiplies the output of the complex adder by the output of the complex adder, a real part generator that extracts the real part of the output of the complex multiplier, and a timing at which the polarity of the output signal of the real part generator is inverted. means for generating a maximum long-period sequence that is synchronized within a certain time period with the maximum long-period sequence activated and transmitted; and determining a transmission sequence using the generated maximum long-period sequence. 1. A data transmission transmitting/receiving device characterized by comprising means for setting the tap gain of an automatic equalizer to an optimum value without any trouble.