JPS6083414A - Transversal demodulating circuit - Google Patents

Abstract

PURPOSE:To allow a carrier regenerating circuit to acquire synchronism even when a receive signal has large distortion by providing a control circuit which switches and outputs control signals of coefficient devices of a transversal equalizer successively when the carrier generating circuit gets out of synchronism. CONSTITUTION:When the carrier regenerating circuit gets out of synchronism, a carrier regeneration control circuit CRC applies an alarm signal to a control circuit CONT, which outputs a switching control signal SWC to change over a switch SW to the side of the control circuit CONT and reads control data out of a memory ROM; and a DA converter D/A outputs an analog control signal B, which is applied to a coefficient device TP of the transversal equalizer consisting of delay coefficient device parts DLC1 and DLC2, discriminators DEC1 and DEC2, and a coefficient control circuit TPC. Consequently, even when a receive signal with large distortion is inputted while the carrier regenerating circuit gets out of synchronism, switching to the tap coefficient device TP corresponding to the distortion is performed, so the carrier regenerating circuit acquires synchronism.

Description

DETAILED DESCRIPTION OF THE INVENTION 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 digital radio systems that use modulation methods such as PSK and CAM, a carrier wave is regenerated on the receiving side, and the received signal is synchronously detected using this regenerated carrier wave, and the level of the detected output signal is identified. A configuration in which a 1-transversal equalizer and a carrier recovery circuit are combined is known as a transversal demodulator. In such a transversal demodulator,
1. If the transmission wave regeneration circuit enters the synchronization pull-in state first, and then the transversal equalizer starts equalization operation, when the distortion of the received signal increases, the transversal equalizer Because the eye pattern is opened by equalization by , the carrier recovery circuit can maintain synchronization up to fairly large distortions of the received signal.

However, if a highly distorted received signal is input before the carrier wave recovery circuit pulls in, the tap coefficient of the transversal equalizer will deviate greatly from the optimum value, making it impossible for the carrier wave recovery circuit to pull in synchronization. . Therefore, the effect of the combination of the carrier wave regeneration circuit and the 1-ranceversal equalizer cannot be fully exhibited. In such cases, it is possible to use a training bag, but
It is practically difficult to use training patterns in wireless systems.

OBJECTS OF THE INVENTION It is an object of the present invention to enable synchronization of a carrier regeneration circuit even for a received signal with large distortion, thereby stabilizing a demodulator.

Composition of the Invention The present invention provides a transversal demodulation device in a digital wireless communication system that has a transversal equalizer and a carrier wave regeneration circuit and demodulates a received signal, in which the +i transmission wave regeneration circuit loses synchronization. This system is equipped with a control circuit that sequentially switches and outputs the control signal of the coefficient unit of the transversal equalization layer as a value corresponding to various input distortions when a received signal with large distortion occurs. Also, it is possible to synchronize the carrier wave regeneration circuit. Examples will be described in detail below.

Embodiment of the Invention FIG. 1 is a block diagram of main parts of an embodiment of the invention, in which a received signal is input to the input terminal IN, and the voltage controlled oscillator VC
The output of O is used as a regenerated carrier wave and is synchronously detected in a synchronous detector DET. If the received signal is, for example, a 4-phase PSK signal or Q
In the case of an AM signal, quadrature synchronous detection is performed, and the detection output signal
, Y are input to the transversal equalizer. The transversal equalizer includes delay coefficient units DLC1 and DLC2.
, discriminators DECI, DEC2, and a coefficient control circuit TPO, and LC2 is a delay coefficient unit DLC.
Since it has the same configuration as No. 1, detailed illustration is omitted.

The delay coefficient unit DLCI, D, LC2 is composed of a plurality of delay elements T, a plurality of coefficient units TP, a plurality of switches SW, adder circuits ADI, AI) 2, etc., and the switch SW is controlled by the coefficient control circuit TPO. The signal A and the control signal B from the control circuit C0NT are switched by a switching control signal SWC from the control circuit C0NT and applied to the coefficient multiplier TP.

Classifiers DEC1 and DEC2 perform level discrimination and output demodulated data from output terminals 0UTL and 0UT2, and this demodulated data is applied to a coefficient control circuit TPC. It is also applied to the carrier wave regeneration control circuit CRC via the coefficient control circuit Tpc. The carrier wave regeneration circuit consists of a carrier wave regeneration control circuit CRC and a voltage controlled oscillator VCO.The carrier wave regeneration control circuit CRC calculates the phase error component through baseband processing, outputs the control voltage of the voltage controlled oscillator VCO, and adjusts the received signal phase. It generates a one-pronged transmission wave synchronized with the .

Furthermore, the control circuit C0NT is configured by a microprocessor, for example, and includes a memory ROM (read-only memory) storing control data and a DA converter DRIA, and the control circuit C0NT is composed of a microprocessor, and includes a DA converter DRIA. When an alarm signal is received, a switching control signal SWC is output to control the switch SW, and the control signal B from the control circuit C0NT is input to the coefficient multiplier TP as shown in the figure.

In the steady state, the switch SW is switched to the coefficient control circuit Tpc side, and the control signal A from the coefficient control circuit TPO is input to the coefficient unit TP, and the coefficient unit TP is controlled so that the received pulse response is optimized. Ru.

When the carrier wave regeneration circuit becomes out of synchronization, an alarm signal is applied from the carrier wave regeneration control circuit CRC to the control circuit C0NT, and the control circuit C0NT outputs the switching control signal SWC and switches the switch SW to the control circuit C, ON T side. The control data stored in the memory ROM is read out, and the analog control signal B is outputted by the DA converter DA and applied to the coefficient unit P.

Since the memory ROM stores control data corresponding to various distortions, for example, the control data assuming the distortion with the highest probability of occurring is first read out to control the coefficient unit TP, and the resulting transversal etc. If the carrier wave recovery circuit is unable to pull in synchronization even with the equalization operation of the equalizer, control data assuming the distortion with the next probability of occurrence is read out, the ζ coefficient unit TP is controlled, and the carrier wave recovery circuit pulls in the synchronization. The control circuit C0NT monitors whether this can be done. In this way, the control circuit C0NT sequentially reads out the control data from the memory ROM and repeats it until the carrier wave regeneration circuit performs synchronization pull-in. When the carrier wave regeneration circuit performs synchronization pull-in, the alarm signal disappears, so the control circuit GO'
NT switches the switch SW to the coefficient control circuit TPC side by the switching control signal SW, and returns to the automatic equalization state.

Therefore, when the carrier regeneration circuit loses synchronization, even if a received signal with large distortion is input, the tap coefficient of the transversal equalizer can be switched to correspond to the distortion, so the carrier regeneration circuit can be synchronized. can be achieved.

Figure 2 shows the M curve. The equalization range where the error rate is 10-3 when the carrier regeneration circuit is in the synchronization state is shown by curve a. When the carrier regeneration circuit loses synchronization, the carrier The conventional range in which the reproducing circuit can perform synchronization pull-in is as shown in the curve, where synchronization becomes impossible when the DIP frequency drops by several dB, but according to the present invention, as shown in curve C, synchronization pull-in becomes impossible. The carrier wave regeneration circuit has a synchronization pull-in range that is approximately the same as that in the synchronization pull-in state. Therefore, even in the case of a received signal with large distortion, the carrier regeneration circuit can be synchronized and the received signal can be demodulated.

The above embodiment is about a case where a transversal equalizer is provided to perform an equalization operation in the baseband band, but a transversal equalizer is provided to perform an equalization operation in an intermediate frequency band. It is also possible to provide one. That is, as shown in FIG. 3, the intermediate frequency signal IF is connected to the hybrid circuit HY.
It branches at B and inputs each to a transversal equalizer. The transversal equalizer consists of a delay element T and a coefficient unit T
The control signal A from the coefficient control circuit TPO and the control signal B from the control circuit C0NT are switched by the switch SW and applied to the coefficient multiplier TP. The switching control signal SWC that controls the switching of this switch SW uses an alarm signal of out-of-synchronization of the carrier wave regeneration control circuit CRC.The alarm signal is added to the control circuit C0NT, and the control signal B from the control circuit C0NT is used as a coefficient. Control signals B corresponding to various distortions are sequentially outputted until the carrier regeneration circuit enters the synchronization pull-in state, as in the previous embodiment.

When the carrier wave regeneration circuit enters the synchronous pull-in state, the alarm signals from the carrier wave regeneration control circuits C and RC disappear, so the switch SW is switched to the coefficient control circuit TPC side.
A control signal A from the coefficient control circuit TPC is applied to the coefficient unit TP to perform an automatic equalization operation to optimize the received pulse response. Further, the voltage controlled oscillator VCO is controlled by the control voltage from the carrier wave regeneration control circuit CRC,
Using the output of the voltage controlled oscillator VCO as a regenerated carrier wave, the equalized intermediate frequency signal IF is synchronously detected by the synchronous detector DET. Note that illustration of the discriminator and the like is omitted.

This embodiment operates the transversal equalizer in the intermediate frequency band, and has the advantage of being simpler in configuration compared to the transversal equalizer operated in the baseband band of the previous embodiment. However, 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 C0NT in each of the above-mentioned 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, so it may be configured by various types other than being configured by a microprocessor. It can also be configured with a logic circuit. Also, it is of course possible to apply the control signal B from the control circuit C0NT to all the coefficient units TP of the transversal equalizer, but it is possible to apply the control signal B from the control circuit CON'F to only some coefficient units TP.
It is also possible to have a configuration in which .

As described in detail, the present invention sequentially switches the control signal of the coefficient unit of the 1-rance universal equalizer to values corresponding to various input distortions when the carrier recovery circuit becomes out of synchronization. It is equipped with a control circuit C0NT that outputs
When the carrier wave regeneration circuit becomes out of synchronization, by controlling the coefficient unit of the transversal equalizer with the control signal B corresponding to the assumed sparrow, it is possible to bring the carrier wave regeneration circuit into synchronization. can be converted into

Therefore, there is an advantage that the synchronization pull-in range of the carrier wave regeneration circuit can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a main part of one embodiment of the present invention, FIG. 2 is an explanatory diagram of an M curve, and FIG. 3 is a block diagram of a main part of another embodiment of the present invention. DET is a synchronous detector, C0NT is a control circuit, CRC is a carrier wave regeneration control circuit, VCO is a voltage controlled oscillator, TPC is a coefficient control circuit, TP is a coefficient multiplier, T is a delay element, and SW is a switch. Patent applicant: Fujitsu Ltd. Representative Patent Attorney Shoji Aitani Representative Patent Attorney Hiroshi Watanabe −

Claims (1)

[Claims] In a transversal demodulator in a digital wireless communication system that has a transversal equalizer and a carrier wave regeneration circuit and demodulates a received signal, when the carrier wave regeneration circuit becomes out of synchronization, the transversal, etc. 1. A 1-lance versal demodulator comprising a control circuit that sequentially switches and outputs a control signal of a coefficient unit of a converter as a value corresponding to various input distortions.