JPH0797739B2 - Transversal demodulator - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a transversal demodulation device for a digital radio device having a transversal equalizer and a carrier recovery circuit.

Conventional technology and problems In the digital wireless system using the modulation system such as PSK and QAM, the carrier is regenerated on the receiving side, the received signal is synchronously detected by this regenerated carrier, and the level of the detected output signal is identified. For example, a digital signal is demodulated by means of the like, and a configuration in which a transversal equalizer and a carrier recovery circuit are combined is known as a transversal demodulator. In such a transversal demodulator, when the carrier recovery circuit is in the synchronization pull-in state first, and then the transversal equalizer starts the equalization operation, when the distortion of the received signal is increased, Since the eye pattern is opened by the equalization by the transversal equalizer, the carrier recovery circuit can maintain the synchronization pull-in state up to a considerably large distortion of the received signal.

However, if a received signal with a large distortion is input before the carrier recovery circuit pulls in, the tap coefficient of the transversal equalizer greatly deviates from the optimum value, and the synchronization recovery of the carrier recovery circuit cannot be performed. Therefore, the effect of combining the carrier wave regenerating circuit and the transversal equalizer cannot be sufficiently exerted. Although it is possible to use the training pattern in such a case, it is practically difficult to use the training pattern in the wireless system.

An object of the present invention is to enable synchronization of a carrier recovery circuit even for a reception signal having a large distortion and to stabilize a demodulator.

The present invention relates to a transversal demodulator in a digital wireless communication system for demodulating a received signal, the transversal equalizer having a transversal equalizer and a carrier recovery circuit, and a coefficient unit of the transversal equalizer. In addition, normally, a switch for adding a control signal formed in the coefficient control circuit based on the demodulated data and an alarm signal due to out-of-synchronization of the carrier recovery circuit are used to switch and control the switch, and input distortion with a high probability of occurrence is generated. A corresponding control signal is applied to the coefficient unit via the switch, and when the synchronization of the carrier recovery circuit cannot be pulled in, a control signal corresponding to the input distortion of the next occurrence probability is applied to the coefficient unit via the switch. And a control circuit for repeatedly controlling the same until the synchronization of the carrier recovery circuit is performed. Even in the case of, it is possible to pull in the synchronization of the carrier recovery circuit. Examples will be described in detail below.

Embodiment 1 of the Invention FIG. 1 is a block diagram of an essential part of an embodiment of the present invention, in which a received signal is input to an input terminal IN and the output of a voltage controlled oscillator VCO is used as a reproduced carrier wave in a synchronous detector DET. Is detected. When the received signal is, for example, a 4-phase PSK signal or a QAM signal, quadrature synchronous detection is performed, and the detection output signals X and Y are input to the transversal equalizer. The transversal equalizer is composed of delay coefficient units DLC1 and DLC2, discriminators DEC1 and DEC2, and a coefficient control circuit TPC. The delay coefficient unit DLC2 has the same configuration as the delay coefficient unit DLC1. Is omitted. The delay coefficient units DLC1 and DLC2 are composed of a plurality of delay elements T, a plurality of coefficient units TP, a plurality of switches SW, and addition circuits AD1 and AD2.
And the switch SW receives the control signal A from the coefficient control circuit TPC and the control signal B from the control circuit CONT.
It is switched by the switching control signal SWC from CONT and added to the coefficient unit TP.

The level is discriminated by the discriminators DEC1 and DEC2, and the output terminal OUT
The demodulated data is output from 1 and OUT2, and this demodulated data is added to the coefficient control circuit TPC. It is also added to the carrier wave reproduction control circuit CRC via the coefficient control circuit TPC. The carrier recovery circuit, which includes the carrier recovery control circuit CRC and the voltage controlled oscillator VCO, calculates the phase error component by baseband processing in the carrier recovery control circuit CRC, outputs the control voltage of the voltage controlled oscillator VCO, and outputs the received signal phase. It generates a carrier wave synchronized with.

The control circuit CONT is composed of, for example, a microprocessor, and includes a memory ROM (read only memory) that stores control data and a DA converter D / A. When the alarm signal is received, the switching control signal SWC is output and the switch S
Control signal W from control circuit CONT to control W
Is switched so as to be input as shown in the figure.

In the steady state, the switch SW is switched to the coefficient control circuit TPC side, the control signal A from the coefficient control circuit TPC is input to the coefficient unit TP, and the coefficient unit TP is controlled so that the received pulse response becomes optimum. It

When the carrier wave reproduction circuit goes out of synchronization, an alarm signal is added from the carrier wave reproduction control circuit CRC to the control circuit CONT,
The control circuit CONT outputs the switching control signal SWC to output the switch SW.
Is switched to the control circuit CONT side, the control data stored in the memory ROM is read, the analog control signal B is output by the DA converter D / A, and the analog control signal B is added to the counter TP.

The control data corresponding to various input distortions is stored in the memory ROM, and the control data corresponding to the input distortion with a high probability of occurrence is configured to be read first, and the control data is converted by the DA converter D / A. Convert to analog control signal B to convert coefficient T
In addition to P, it causes the carrier recovery circuit CRC to perform the synchronization pull-in, and a control circuit determines whether or not the synchronization pull-in can be performed.
CONT monitors, and when the synchronous pull-in cannot be performed within the predetermined time, the control data corresponding to the input distortion with the next highest occurrence probability is read from the memory ROM to control the coefficient unit TP,
Similarly to the previous time, the carrier wave reproduction circuit CRC is made to perform the synchronization pull-in, and the control circuit CONT monitors whether or not the synchronization pull-in is possible. When the carrier recovery circuit CRC cannot perform the synchronous pull-in, the control circuit CONT reads control data from the memory ROM in the order of the probability of occurrence of input distortion and repeats until the carrier recovery circuit performs the synchronous pull-in. Since the alarm signal disappears when the carrier recovery circuit carries out the synchronous pull-in, the control circuit CONT switches the switch SW to the coefficient control circuit TPC side by the switching control signal SW to restore the automatic equalization state. Therefore, when the carrier recovery circuit is out of synchronization, even if a received signal with a large distortion is input, it is possible to switch to the tap coefficient of the transversal equalizer corresponding to that distortion, so the synchronization recovery of the carrier recovery circuit is possible. Can be achieved.

Fig. 2 shows the M curve. The equalization range where the error rate is 10 ^-3 when the carrier recovery circuit is in the synchronization pull-in state is shown by curve a, and when the carrier recovery circuit loses synchronization, the carrier wave is lost. The conventional range in which the reproducing circuit can perform the synchronous pull-in is, as shown by the curve b, when the Dip frequency is several d.
However, according to the present invention, as shown by the curve c, the carrier recovery circuit has a sync pull-in range substantially the same as the sync pull-in state. Therefore, even in the case of a received signal having a large distortion, the carrier recovery circuit can be synchronized and the received signal can be demodulated.

The above-mentioned embodiment is a case where the transversal equalizer is provided so as to perform the equalization operation in the baseband, but the transversal equalizer is provided so as to perform the equalization operation in the intermediate frequency band. It can also be provided. That is, as shown in FIG. 3, the intermediate frequency signal IF is branched by the hybrid circuit HYB and input to the transversal equalizer.
The transversal equalizer includes a delay element T, a coefficient unit TP, an adder circuit ADD, and a switch SW, and switches the control signal A from the coefficient control circuit TPC and the control signal B from the control circuit CONT with the switch SW. Is added to the coefficient unit TP. The switching control signal SWC for switching control of the switch SW uses an alarm signal out of synchronization of the carrier wave reproduction control circuit CRC. The alarm signal is added to the control circuit CONT, and the control signal B from the control circuit CONT is used as a coefficient. Added to the vessel TP,
Similar to the above-described embodiment, the control signal B corresponding to various distortions is sequentially output until the carrier recovery circuit is brought into the synchronous pull-in state.

When the carrier recovery circuit is in the synchronous pull-in state, the alarm signal from the carrier recovery control circuit CRC disappears, so the switch SW is switched to the coefficient control circuit TPC side, and the control signal A from the coefficient control circuit TPC is added to the coefficient multiplier TP. Then, the automatic equalization operation is performed so as to optimize the received pulse response. In addition, the voltage control oscillator VCO is controlled by the control voltage from the carrier recovery control circuit CRC.
Of the equalized intermediate frequency signal IF as the reproduction carrier
Is synchronously detected by the synchronous detector DET. Illustration of the discriminator and the like is omitted.

This embodiment operates the transversal equalizer in the intermediate frequency band, and has an advantage that the configuration can be simplified as compared with the transversal equalizer operated in the baseband of the above-described embodiments. Since the synchronous detector DET is included in the control loop, it is necessary to consider the stability of the coefficient control of the transversal equalizer.

The control circuit CONT in each of the above-described embodiments may have any configuration as long as it can sequentially output the control signal B of the coefficient unit of the transversal equalizer corresponding to various distortions. It can also be configured by various logic circuits. Further, the control signal CONT is supplied from the control circuit CONT to all coefficient units TP of the transversal equalizer.
Of course, it is possible to add the control signal B from the control circuit CONT to only some of the coefficient units TP.

As described above, according to the present invention, the coefficient control signal A formed on the basis of the demodulated data in the coefficient control circuit TPC is always added to the coefficient multiplier TP via the switch SW, and the carrier wave reproduction circuit is provided.
Switch SW by alarm signal due to out of sync of CRC
To control the control signal A corresponding to various input distortions.
The output is sequentially output in the order of the input distortion with the highest probability of occurrence, and the switch SW
A control circuit CONT that is added to the coefficient unit TP via is provided. When the carrier recovery circuit CRC is out of synchronization, the control signal A corresponding to the input distortion with a high probability of occurrence in the wireless communication line is first transmitted. If the loss of synchronization of the carrier recovery circuit CRC is not eliminated in addition to the coefficient multiplier TP, the control signal A corresponding to the input distortion of the next occurrence probability is sequentially added to the coefficient multiplier TP, so that the carrier recovery circuit CRC is repeated. There is an advantage that the sync pull-in range can be expanded and the sync pull-in can be speeded up.

[Brief description of drawings]

FIG. 1 is a block diagram of an essential part of an embodiment of the present invention, FIG. 2 is an explanatory diagram of an M curve, and FIG. 3 is a block diagram of an essential part of another embodiment of the present invention. DET is a synchronous detector, CONT is a control circuit, CRC is a carrier recovery control circuit, VCO is a voltage controlled oscillator, TPC is a coefficient control circuit, TP
Is a coefficient unit, T is a delay element, and SW is a switch.

Claims (1)

[Claims] 1. A transversal demodulator in a digital wireless communication system for demodulating a received signal, comprising a transversal equalizer and a carrier recovery circuit, wherein a coefficient unit of the transversal equalizer comprises: Normally, the switch is controlled by a switch for applying a control signal formed in the coefficient control circuit based on the demodulated data and an alarm signal due to out-of-synchronization of the carrier recovery circuit, and the input distortion with a high probability of occurrence is dealt with. A control signal is added to the coefficient unit via the switch, and when the synchronization of the carrier recovery circuit cannot be pulled in, a control signal corresponding to the input distortion of the next occurrence probability is applied to the coefficient unit via the switch. And a control circuit for repeatedly controlling the carrier wave reproduction circuit until the synchronization pull-in is performed. Adjustment device.