JP2578555B2 - Phase equalization method, frequency equalization method and communication method using them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a telephone line, a radio line,
The present invention relates to a system for performing communication by an orthogonal modulation system using an optical communication line or the like, and particularly to an equalization system for automatically correcting characteristics including a transmission system, a transmission system, and a reception system.

[0002]

2. Description of the Related Art When transmitting a quadrature modulated signal by wire or wirelessly, a sufficient transmission band is required in order to prevent a decrease in signal quality. However, usually, in addition to the shortage of the transmission band, there are factors that hinder signal transmission with good quality, such as the frequency characteristics and the phase characteristics being not flat. In particular, when transmitting a stereo signal, if the frequency characteristics and phase characteristics of the transmission band are poor, the degree of separation between left and right channels, the frequency characteristics and phase characteristics of each channel, and the like are greatly affected.

As a method of improving the quality of a transmitted signal, a method of strictly managing the characteristics of a transmitter and a receiver and transmitting / receiving a signal whose characteristics have been corrected in accordance with the characteristics of a device or a transmission line has been conventionally used. was there. That is, a technique of correcting the signal characteristics on the transmitting side, correcting the signal characteristics on the receiving side, or combining both has been used.

[0004]

However, when the quality of a transmission signal is improved by such a method, some new problems arise. For example, when the characteristics of a transmitter and a receiver are used near their limits, it is difficult to adjust the equipment. If a receiver having slightly different characteristics from the transmitter is used, generally, good transmission signal quality cannot be ensured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made in consideration of the above problem. A transmitter, which automatically corrects a signal distortion or the like caused by characteristics of a transmitter, a transmission line, and a receiver, is provided. And the characteristics of the receiver can be used up to its limit without adjusting the equipment, and good signal quality can be obtained even when a receiver with characteristics different from the transmitter is used. Aim.

[0006]

In order to achieve the above object, the present applicant proposes the following phase equalization system, frequency equalization system and communication system.

First, in the phase equalization system of the present invention, a transmitting side transmits an equalized signal synchronized with a carrier, a receiving side detects a time difference between the carrier and the equalized signal, and transmits a detection result when transmitting. It is characterized in that the time position of the equalized signal with respect to the carrier is corrected according to the comparison result so as to be the time position at the time of transmission, as compared with the time difference, and the phase detection of the quadrature modulation signal is performed based on the correction result.

Next, according to the frequency equalization system of the present invention, the transmitting side orthogonally modulates and transmits an equalized signal having predetermined frequency characteristics, and the receiving side converts the equalized signal included in the phase detection output. The frequency characteristic is compared with the predetermined frequency characteristic, and the frequency characteristic of the filter arranged in the preceding stage of the phase detection circuit is changed and set based on the comparison result so that the difference between the two is sufficiently reduced.

Further, the communication system of the present invention is characterized in that the phase equalization system and the frequency equalization system of the present invention are realized by a single equalized signal. That is, on the transmitting side, an equalized signal having a predetermined frequency characteristic is superimposed on at least one channel of the orthogonal modulation signal and transmitted in synchronization with the carrier, and on the receiving side, the time difference between the carrier and the equalized signal is calculated. Detect, compare the detection result with the time difference at the time of transmission, correct the time position of the equalized signal with respect to the carrier according to the comparison result to be the time position at the time of transmission, and perform phase detection of the quadrature modulation signal based on the correction result. On the other hand, the frequency characteristic of the equalized signal included in the phase detection output is compared with the predetermined frequency characteristic, and the frequency of the filter disposed in the preceding stage of the phase detection circuit is determined based on the comparison result so that the difference between the two becomes sufficiently small. The characteristic is changed and set.

In the communication system according to the present invention, further, on the transmitting side, the equalized signal is transmitted by only one channel of the quadrature modulated signal, and on the receiving side, the equalizing signal is transmitted on the transmitting side of the phase detection output. The frequency characteristic of a filter disposed upstream of the phase detection circuit is changed and set so that leakage of an equalized signal to a phase detection output related to a channel on which no signal is superimposed is sufficiently reduced.

[0011]

According to the phase equalization method of the present invention, an equalized signal synchronized with the carrier is transmitted from the transmitting side. On the receiving side, the time difference between the carrier of the quadrature modulated signal to be transmitted and the equalized signal is detected, and the detection result is compared with the time difference at the time of transmission. On the receiving side, the time position of the equalized signal with respect to the carrier is corrected according to the comparison result so as to be the time position at the time of transmission, and phase detection of the quadrature modulated signal is performed based on the correction result. Therefore, the phase characteristics generated by the characteristics of the transmitter, the transmission path, the receiver and the like are equalized based on the detected carrier and the time position of the equalized signal. At that time, adjustment of devices such as a transmitter and a receiver is not required. In addition, since the phase equalization processing on the receiving side is independent of the characteristics on the transmitting side, good signal quality can be obtained even when a receiver having characteristics different from those of the transmitter is used.

Next, in the frequency equalization system of the present invention, an equalized signal having a predetermined frequency characteristic is orthogonally modulated and transmitted. On the receiving side, the received quadrature modulated signal is phase-detected by a phase detection circuit. This phase detection circuit is provided with a filter whose frequency characteristic can be changed and set. In the present invention, a feedback loop including the filter and the phase detection circuit is configured. That is, on the receiving side, the frequency characteristic of the equalized signal included in the phase detection output is compared with the predetermined frequency characteristic,
The frequency characteristic of the filter is changed and set based on the comparison result so that the difference between the two becomes sufficiently small. Therefore, the transmitter,
The frequency characteristics generated by the characteristics of the transmission path, receiver, etc.
It is equalized by a feedback loop including a filter and a phase detection circuit. At that time, adjustment of devices such as a transmitter and a receiver is not required. Further, since the phase equalization processing on the receiving side is independent of the transmitting side, good signal quality can be obtained even when a receiver having characteristics different from those of the transmitter is used.

Further, in the communication system of the present invention, the phase equalization system and the frequency equalization system of the present invention are realized by a single equalized signal. That is, the equalized signal transmitted from the transmitting side is an equalized signal having a predetermined frequency characteristic, and the equalized signal is superimposed on at least one channel of the orthogonal modulation signal and transmitted in synchronization with the carrier. You. On the receiving side, the above-described time position correction and filter characteristic change setting are performed. Therefore, in this method,
The operations of both the phase equalization method and the frequency equalization method described above can be obtained by a single equalized signal.

When the equalized signal is superimposed on only one channel of the quadrature modulated signal in the communication system of the present invention, the phase detection for the channel on which the equalized signal is not superimposed is performed on the receiving side. The frequency characteristic of the filter disposed in the preceding stage of the phase detection circuit is changed and set so that the leakage of the equalized signal to the output becomes sufficiently small. Therefore,
Signal leakage between channels is reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a communication apparatus according to an embodiment of the present invention. The device shown in this figure has a configuration in which a transmitter 10 and a receiver 12 are wirelessly connected, and is a device for transmitting a stereo signal by a quadrature modulation method.

The transmitter 10 includes a quadrature modulation circuit 14, an equalization pulse generation circuit 16, and a transmission unit 18.

The orthogonal modulation circuit 14 orthogonally modulates the signals of the L and R channels during stereo transmission. In addition, during the equalization period, the equalization pulse generated by the equalization pulse generation circuit 16 is orthogonally modulated at the carrier peak timing via the electronic switch 20 and supplied to the transmission unit 18. As described above, in this embodiment, during the equalization operation, the stereo signal is turned off, and the equalization pulse whose carrier is synchronized with the L channel is superimposed only on the L channel.

The transmission section 18 converts the L and R channel signals and the equalization pulses supplied from the quadrature modulation circuit 14 into radio frequencies and transmits the radio frequencies to the receiver 12 via the antenna 22.

The equalizing pulse output from the equalizing pulse generating circuit 16 is superimposed only on the L channel.

The receiver 12 has a receiving and detecting circuit 2 for receiving and detecting a signal from the transmitter 10 through an antenna 24.
6. The quadrature modulated signal obtained by the reception and detection circuit 26 is input to the phase detection circuits 30 and 32 via the digital equalization filter 28. The phase detection circuits 30 and 32 are detection circuits for the L or R channels, respectively. That is, both of them output a quadrature modulated signal by phase detection using a quadrature sampling clock related to SIN or COS.

The output of the receiving and detecting circuit 26 is also supplied to a carrier detecting circuit 34 and an equalizing pulse timing detecting circuit 36. The carrier detection circuit 34 detects a carrier from the quadrature modulation signal output from the reception and detection circuit 26. Further, the equalization pulse timing detection circuit 36
An equalizing pulse, particularly its timing, is detected from the quadrature modulated signal output from the receiving and detecting circuit.

An equalizing pulse delay correcting circuit 38 is connected to the subsequent stage of the carrier detecting circuit 34 and the equalizing pulse timing detecting circuit 36. Equalization pulse delay correction circuit 38
Compares the peak timing of the carrier detected by the carrier detection circuit 34 with the timing of the equalization pulse detected by the equalization pulse timing detection circuit 36, and generates a quadrature sampling clock based on the comparison result. That is, the quadrature sampling clock is corrected by the equalization pulse delay correction circuit 38 so that the phase characteristics of the transmitter 10, the radio transmission path between the antennas 22 and 24, and the receiver 12 are compensated. The quadrature sampling clock is supplied to the phase detection circuits 30 and 32, and the phase detection is performed by the detection circuits 30 and 32, so that the outputs of the phase detection circuits 30 and 32 become the signals subjected to the phase equalization. Become.

In this embodiment, an error detection circuit 40 is provided at the subsequent stage of the equalization pulse timing detection circuit 36. The error detection circuit 40 stores the timing of the equalization pulse detected by the equalization pulse timing detection circuit 36 and the frequency characteristics of the equalization pulse output from the phase detection circuit 30 as data on the equalization pulse pattern table 42. This is a circuit for detecting an error by comparing the frequency characteristic (equalized pulse pattern) that has been used. In the present embodiment, an equalization pulse whose frequency characteristic is represented by a raised cosine waveform is generated by the equalized pulse generation circuit 16, and the equalized pulse pattern table 42 also has a corresponding raised cosine waveform in the equalized pulse pattern table 42. The frequency component is stored as data. The error detection circuit 40 converts an error in the frequency characteristics of the equalization pulse output from the equalization pulse timing detection circuit 36 into an equalization pulse pattern table 42.
Therefore, the detection output of the error detection circuit 40 is the transmitter 10, the antennas 22 and 2
4 represent the frequency characteristics given by the wireless transmission path and the receiver 12.

The correction circuit 4 is provided after the error detection circuit 40.
4 are connected. The correction circuit 44 includes the error detection circuit 4
0, the digital equalization filter 28
Is a circuit for setting the various coefficients. In other words, the correction circuit 44 is designed so that the output of the error detection circuit 40 is sufficiently small, that is, the frequency characteristics of the transmitter 12, the wireless transmission path between the antennas 22 and 24, and the frequency characteristics of the receiver 12 are equalized. This is a circuit for setting the frequency characteristics of the equalizing filter 28. As described above, the digital equalizing filter 2
8 is supplied to the phase detection circuits 30 and 32, and the equalized pulse is transmitted as a quadrature modulation signal relating to the L channel. Therefore, the output signal of the phase detection circuit 30 is sent to the error detection circuit 40 as an error signal. By performing the feedback, a frequency equalization feedback loop based on the change setting of the characteristic of the digital equalization filter 28 is formed.

In this embodiment, the output of the phase detection circuit 32 is also fed back to the error detection circuit 40. As described above, since the equalization pulse is superimposed only on the L channel and not on the R channel,
The leakage from the L channel to the R channel is detected by the phase detection circuit 3
2 can be detected as a component related to the equalization pulse appearing in the output. That is, the error detection circuit 40 controls the characteristics of the digital equalization filter 28 using the output of the phase detection circuit 30 as an error signal, and controls the digital equalization filter 28 so that leakage from the L channel to the R channel does not occur. It has a control function.

Therefore, according to the present embodiment, the transmitter 10 and the radio transmission path between the antennas 22 and 24 and the frequency and phase generated by the receiver 12 can be adjusted without adjusting the transmitter 10 and the receiver 12. Characteristics can be automatically corrected. As a result, without having to adjust the equipment,
Low distortion transmission can be realized. Further, when a quadrature modulation signal is transmitted from a single transmitter 10 to a plurality of receivers 12, while effectively utilizing the performance of each receiver 12,
Quadrature modulation can be transmitted with low distortion. At that time, each receiver 12 may have slightly different performance. In addition, even if the transmission paths at this time are different transmission paths, low distortion transmission can be realized by effectively utilizing the performance of this transmission path.

In the above description, only the wireless configuration is mentioned. However, the present invention can also be applied to wired communication. Further, the present invention can be applied to optical communication.

[0029]

As described above, according to the phase equalization method of the present invention, an equalized signal synchronized with a carrier is transmitted,
The receiver detects the time difference between the carrier and the equalized signal and corrects the time position of the equalized signal, and then performs phase detection of the quadrature modulated signal based on the correction result. The phase characteristics generated by such characteristics can be equalized by a phase equalization process independent of the transmission side without adjusting devices such as a transmitter and a receiver.

According to the frequency equalization method of the present invention,
An equalized signal having a predetermined frequency characteristic is orthogonally modulated and transmitted, and a change in the frequency characteristic of the equalized signal generated by the transmitter, the transmission path and the receiver is detected on the receiving side, and the signal is placed before the phase detection circuit. The frequency characteristics of the filter are changed and set, so that the frequency characteristics generated by the characteristics of the transmitter, transmission line, receiver, etc. can be adjusted by the frequency equalization process independent of the transmitting side to adjust the devices such as the transmitter and receiver. Can be equalized without.

As a result, according to the present invention, low distortion transmission can be realized by making the most effective use of the characteristics of the transmitter, the transmission path, the receiver, and the like, and the transmission band. Further, since the phase equalization processing and the frequency equalization processing are independent of the transmitting side, low distortion transmission can be realized even when a receiver having characteristics different from that of the transmitter is used, and good signal quality can be obtained. For example, when a signal transmitted from a certain transmitter is received by a plurality of receivers, good transmission quality can be obtained for each receiver. For example, a plurality of reception signals from a certain transmitter via different transmission paths can be obtained. Even when a signal is transmitted to a receiver, good transmission quality can be obtained for each receiver.

Further, according to the communication system of the present invention, the phase equalization system and the frequency equalization system of the present invention can be realized by a single equalized signal, and both effects can be obtained.

Then, the equalized signal is set to one of the orthogonal modulation signals.
Change the frequency characteristics of the filter placed in front of the phase detection circuit so that the leakage of the equalized signal to the phase detection output for the channel on which the equalized signal is not superimposed is sufficiently reduced. Therefore, in addition to the above effects, an effect of reducing signal leakage between channels can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a communication system according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transmitter 12 Receiver 14 Quadrature modulation circuit 16 Equalization pulse generation circuit 18 Transmitter 20 Electronic switch 22, 24 Antenna 26 Reception and detection circuit 28 Digital equalization filter 30, 32 Phase detection circuit 34 Carrier detection circuit 36 Equalization pulse Timing detection circuit 38 Equalization pulse delay correction circuit 40 Error detection circuit 42 Equalization pulse pattern table 44 Correction circuit SIN, COS Quadrature sampling clock

Claims (4)

(57) [Claims] 1. A communication system in which a quadrature modulated signal is transmitted from a transmitting side, and a receiving side transmits an equalized signal synchronized with a carrier of the quadrature modulated signal on a receiving side. On the side, the time difference between the carrier and the equalized signal is detected, the detection result is compared with the time difference at the time of transmission, and the time position of the equalized signal with respect to the carrier is corrected according to the comparison result so as to be the time position at the time of transmission. A phase equalization method which performs phase detection of a quadrature modulation signal based on a correction result. 2. A communication system in which a quadrature modulated signal is transmitted from a transmitting side, and a signal to be transmitted is phase-detected and output by a phase detecting circuit on a receiving side. At the receiving side, the frequency characteristic of the equalized signal included in the phase detection output is compared with the predetermined frequency characteristic. A frequency equalization method characterized by changing and setting the frequency characteristics of an arranged filter. 3. A communication system in which a stereo quadrature modulated signal is transmitted from a transmission side, and a reception side performs phase detection output of a signal to be transmitted by a phase detection circuit, wherein a transmission side transmits an equalized signal having a predetermined frequency characteristic. The signal is superimposed on at least one channel of the orthogonal modulation signal and transmitted in synchronization with the carrier. On the receiving side, the time difference between the carrier and the equalized signal is detected, and the detection result is compared with the time difference at the time of transmission. The time position of the equalized signal with respect to the carrier is corrected according to the comparison result so as to be the time position of the carrier, and the phase detection of the quadrature modulated signal is performed based on the corrected result, while the frequency characteristic of the equalized signal included in the phase detection output Is compared with the predetermined frequency characteristic, and the frequency characteristic of the filter arranged in the preceding stage of the phase detection circuit is changed and set based on the comparison result so that the difference between the two becomes sufficiently small. Communication method characterized by and. 4. The communication system according to claim 3, wherein the transmission side transmits the equalized signal by only one channel of the quadrature modulated signal, and the reception side equalizes the phase detection output on the transmission side. A communication method characterized by changing and setting the frequency characteristic of a filter disposed in a stage preceding a phase detection circuit so that leakage of an equalized signal to a phase detection output related to a channel on which a signal is not superimposed is sufficiently reduced.