JP2000050104A - Repeater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good transmission error rate without performing automatic equalization by correcting frequency characteristic for transmitting and receiving frequency modulation wave modulated by a multilevel analog signal to be sent from a transmitting part of a repeater to a receiving part of the repeater. SOLUTION: The frequency characteristics are corrected for transmitting and receiving the frequency modulated wave modulated by the multilevel analog signal to be sent from the transmitting part 9 of the repeater and to the receiving part 10 of the repeater. In this device, the multilevel analog signal to be inputted in a multilevel encoder 11 of the receiving part 10 of the repeater is inputted in a low-pass filter(LPF). The multilevel analog signal from which the noise and the signal in the unwanted frequency band are removed by the LPF and outputted to an input signal level control circuit. A function to perform reverse correction of the frequency characteristics to be degraded by the transmitting part 9 of the repeater and the receiving part 10 of the repeater is provided to the LPF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital repeater for transmitting a binary digital signal as a multi-level signal, and more particularly to a multi-use repeater using a transmitter and a receiver of an analog repeater for FM modulation and demodulation. The present invention relates to a digital FM modulation / demodulation type relay apparatus.

[0002]

2. Description of the Related Art In television broadcasting, for example,
Broadcasting the site and the broadcasting station, whether live broadcast or live recording, such as news reporting from the site where the incident occurred, production of programs involving people in the city, relaying from events and theaters, etc. A transmission system using a relay device used as a means for relaying a program, for example, an FPU (Field Pick-Up) device is an information transmission system indispensable for program production. As described above, the relay device conventionally used as an essential device for television broadcasting has conventionally been a device for transmitting an analog signal. Is changing to a device that transmits data. But,
Many of the analog repeaters are used as active devices. Therefore, digital repeaters that transmit digital signals using the analog repeaters have been developed.

A conventional analog repeater transmits signals to be transmitted, such as a video signal, an audio signal, and a control signal, in the form of an analog signal. The video signal is usually transmitted using a low-pass filter. The band of 5 MHz or less is 6 to 8 MHz where the audio signal and the control signal are higher than the band of the video signal.
A nearby high frequency subcarrier band is used. The transmitting section of the relay apparatus has a pre-emphasis characteristic for lowering the low-frequency characteristic, and the receiving section has a de-emphasis characteristic for raising the low-frequency characteristic.

[0004] The performance and functions required of the repeater are almost the same in the case of handling the transmission of analog signals and in the case of handling the transmission of digital signals. In a repeater using the system, for example, in the case of a transmission mode in which the transmission rate is 45 Mb / s and the multilevel number is eight, a substantially flat frequency characteristic from DC to about 9 MHz is required, and the conventional analog system requires Video signal, audio signal,
All of the frequency bands used for control signals and the like will be required. Particularly, in a repeater of a multilevel digital FM modulation / demodulation system for transmitting digital signals, 7.5M
The frequency characteristic up to around Hz is an important baseband signal band (the transmission mode is 45 Mb / s, in the case of eight values, and differs depending on the transmission mode). However, in the conventional analog repeater, the frequency characteristic is almost flat up to around 5 MHz, has a peak around 6 MHz to 8 MHz, and the higher frequency characteristic often drops.
To transmit digital signals, this 6 MHz
It is necessary to perform compensation corresponding to the peak around ８8 MHz and compensation corresponding to the drop down to about 9 MHz.

FIG. 2 is a block diagram of a digital repeater for transmitting a digital signal by utilizing an analog repeater (the same as that of the repeater of the present invention). Digital repeaters can be broadly divided into, for example, a transmitter installed at a relay site and a receiver installed at a broadcasting station, for example. A transmitter multi-level encoding device 8 that converts the signal into a multi-level analog signal and outputs the signal once
And an analog repeater transmitter 9 for performing FM modulation
And a transmitting antenna 12. The receiving unit side includes:
It comprises a receiving antenna 13, an analog repeater receiving section 10 for performing FM demodulation, and a receiving section multi-level decoding apparatus 11 for converting a multi-level analog signal into a digital signal. In such a configuration, the multi-level FM from the video signal band to the sub-carrier band of the audio signal and the control signal of the analog repeater transmitter 9 for FM modulation and the analog repeater receiver 10 for FM demodulation are provided. Compensation corresponding to deterioration of frequency characteristics necessary for transmitting a multi-level FM signal, which is used as a band for transmitting a signal, is performed by providing an equalizer in the multi-level decoding device 11 of the receiving unit and performing frequency compensation. I have. Compensation of the frequency characteristics by this equalizer
Deterioration of the frequency characteristics of the transmission unit and the reception unit of the relay device can be compensated, but it is necessary to compensate for multipath and fading that occur during transmission.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a circuit for compensating for a frequency characteristic degraded in an analog repeater transmitter and a repeater receiver constituting a digital repeater. Is provided in the multi-level decoding device in the receiving section, and a multi-level coded signal is subjected to FM modulation / demodulation and transmitted.

[0007]

In order to achieve the above object, a repeater according to the present invention performs a multi-level encoding process on an input digital signal to obtain a multi-level encoded signal. A transmitter multi-level encoding device for performing D / A conversion (digital / analog conversion) on a signal and outputting a multi-level analog signal, and a carrier wave using the multi-level analog signal input from the transmitter multi-level encoding device FM transmitter, multiplies the signal to a required frequency and amplifies the power, and outputs an FM modulated wave of the required frequency, and transmits the FM modulated wave of the required frequency input from the relay device transmitting unit A transmitting unit side antenna, a receiving unit side receiving the FM modulated wave of the required frequency transmitted from the transmitting unit side antenna, and an FM of the required frequency inputted from the receiving unit side antenna. Increase the modulation wave And FM demodulation to output the multi-level analog signal and a multi-level analog signal input from the relay apparatus receiving section by performing A / D conversion (analog / digital conversion). A multivalued digital signal, the multivalued digital signal is subjected to waveform shaping, the shaped multivalued signal waveform is determined to a multivalued level, the determined value is converted to a binary digital signal, and data is output. And a receiving unit multi-level decoding device for compensating for frequency characteristics degraded by the relay device transmitting unit and the relay device receiving unit.

More specifically, in the relay apparatus of the present invention, the multi-level decoding device in the receiving section removes noise and unnecessary frequency band signals of the input multi-level analog signal, and removes noise and unnecessary frequency band signals. A low-pass filter that outputs a multi-level analog signal from which a signal has been removed; and a multi-level analog signal from which the noise and unnecessary frequency band signals input from the low-pass filter have been removed is adjusted to a required signal level. An input signal level control circuit that outputs a multilevel analog signal of a signal level,
An A / D conversion circuit for converting the multilevel analog signal of the required signal level input from the input signal level control circuit into a multilevel digital signal and outputting the converted multilevel digital signal; and the A / D conversion circuit A digital filter that shapes the waveform of a multivalued digital signal input from a digital filter and outputs a waveform of the shaped multilevel digital signal, and determines the waveform of the shaped multilevel digital signal input from the digital filter to a multilevel level A multi-level decision circuit for outputting a decision value of the waveform of the multi-level digital signal; and a decision value of the waveform of the multi-level digital signal input from the multi-level decision circuit into serial binary digital signal data. And a parallel / serial conversion circuit for outputting the converted data. Further, in the relay device of the present invention, the receiving unit multi-level decoding device outputs a multi-level analog signal from which a noise or an unnecessary frequency band signal has been removed, and a multi-level analog signal having a required signal level. The output input signal level control circuit is provided with a frequency characteristic for performing an inverse correction of a frequency characteristic deteriorated in the relay device transmitting unit and the relay device receiving unit. Further, in the relay apparatus of the present invention, the multi-level decoding device of the receiving unit may correct the frequency characteristic degraded in the relay unit transmitting unit and the relay unit receiving unit by the digital filter for outputting the waveform of the shaped multi-valued digital signal. Is provided with a filter coefficient set to perform the following.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a relay device according to the present invention will be described. FIG. 2 is a block diagram showing the overall configuration of the relay device according to the present invention. In FIG. 2, reference numeral 8 denotes, for example, a video signal and an audio signal output from a television camera or a microphone at a relay site, which are compressed and multiplexed by an encoder (ENC). A multi-valued transmitting unit that receives a converted digital signal, performs a multi-level coding process to obtain a multi-level coded signal, for example, an 8-level ASK signal, and further performs D / A conversion to output a multi-level analog signal. The encoding device 9 FM-modulates the carrier with the multi-level analog signal input from the transmission unit multi-level encoding device 8, multiplies the frequency up to the microwave of the required frequency and amplifies the power, and FM-modulates the microwave. , An antenna transmitting an FM-modulated wave output from the relay device transmitting unit 9, and a transmitting unit transmitting the FM modulated wave from the antenna 12. An antenna 10 receives an FM modulated wave of a black wave, 10 is an analog repeater receiver that FM-demodulates an FM modulated wave of a microwave received by the antenna 13 and outputs a multi-level analog signal.
1 shows a receiving unit multi-level decoding device that converts an M-demodulated multi-level analog signal into a digital signal.

Next, FIG. 1 shows a detailed block diagram of the multi-level decoding device 11 of the receiving section constituting the relay device of the present invention. In FIG. 1, reference numeral 1 denotes a low-pass filter (LP) for removing unnecessary signals and noise of an FM-demodulated multi-level analog signal input from a relay device receiving unit 10 of the FM demodulation method.
F), 2 is an input signal level control circuit for adjusting a multi-level analog signal from which unnecessary signals and noise have been removed by the LPF 1 to a required signal level, and 3 is an input signal level control circuit 2 whose level is controlled to a required signal level. An A / D conversion circuit for converting the multilevel analog signal into a multilevel digital signal, a digital filter for shaping the waveform of the multilevel digital signal,
Reference numeral 5 denotes a multi-valued judgment circuit for judging the multi-valued level of the multi-valued digital signal. A parallel / serial conversion circuit 7 for outputting multivalued data is a clock recovery circuit for recovering a clock signal for operating each of the digital circuits from the multilevel digital signal.

Next, an operation of microwave relay of a video signal (an audio signal is omitted) by the relay device of the present invention will be described with reference to FIGS. 2 and 1. In general,
For example, the transmission unit multi-level encoding device 8, the relay device transmission unit 9, and the antenna 12 on the transmission unit side are installed at a relay site, and the antenna 13 on the reception unit side and the relay device reception unit 10 and the receiving unit multi-level decoding device 11 are installed in a broadcasting station. However, as is well known, if the distance between the relay site and the broadcasting station is within the effective transmission distance of the relay device, the antenna 13 on the receiving unit side and the relay device receiving unit 10
And the receiving unit multi-level decoding device 11 are installed in a broadcasting station, but if the transmission distance is outside the effective transmission distance, relaying is performed using a plurality of relay devices in tandem.

On the transmitting side, for example, a television camera (not shown) is connected via an encoder (not shown).
A digital signal obtained by compressing and multiplexing a video signal output from a television camera by an encoder is input, and the digital signal is subjected to multi-level encoding processing to obtain a multi-level encoded signal. And outputs the resulting signal to a multi-level analog signal to an analog repeater transmitter 9 that performs FM modulation. The relay device transmission unit 9 performs FM modulation on the carrier with the multi-level analog signal input from the transmission unit multi-level encoding device 8, and converts the FM modulation wave into a predetermined frequency (for example,
Microwaves) and power amplification up to a predetermined power, and output a power-amplified FM modulated wave of a predetermined frequency to the antenna 12.

An antenna 12 on the transmitting side transmits an FM modulated wave of a predetermined frequency toward an antenna 13 on the receiving side. The antenna 13 on the receiving side is the antenna 1 on the transmitting side.
2 receives the FM-modulated wave of a predetermined frequency transmitted from 2 and outputs the received FM-modulated wave of the predetermined frequency to the analog repeater receiver 10. Relay device receiving unit 10
Amplifies and FM-demodulates an FM-modulated wave of a predetermined frequency input from the antenna 13, and outputs a demodulated multi-level analog signal to the receiver multi-level decoding device 11. The operation of the receiving unit multi-level decoding device 11 will be described for each circuit using the block diagram of FIG. Note that the relay device transmitting unit 9
The correction of the frequency characteristics degraded by the relay device and the receiving device 10 is performed by three circuits. The frequency characteristics that can be adjusted by each circuit are adjusted in the overall frequency characteristics, and the overall frequency characteristics are adjusted. The characteristics are made flat.

The multi-level analog signal input from the relay apparatus receiving section 10 to the receiving section multi-level encoding apparatus 11 is an LPF 1
Is input to The LPF 1 removes noise and unnecessary frequency band signals of the multi-level analog signal input from the repeater receiver 10 and sends the multi-level analog signal from which the noise and unnecessary frequency band signals have been removed to the input signal level control circuit 2. Output. The LPF 1 includes a relay device transmitting unit 9 and a relay device receiving unit 10
In this case, a frequency characteristic for reversely correcting the frequency characteristic degraded by the above is provided. The input signal level control circuit 2 controls the level of the multilevel analog signal input from the LPF 1 so as to have a required signal level, and outputs the multilevel analog signal of the required signal level to the A / D conversion circuit 3. The input signal level control circuit 2 uses a video amplifier, and can perform adjustment so as to perform inverse correction of the frequency characteristic deteriorated in the relay device transmitting unit 9 and the relay device receiving unit 10. The A / D conversion circuit 3 converts a multilevel analog signal of a required signal level input from the input signal level control circuit 2 into a multilevel digital signal, and converts the converted multilevel digital signal into a digital filter 4 and a clock signal. Output to the reproduction circuit 7.

The digital filter 4 shapes the waveform of the multilevel digital signal input from the A / D conversion circuit 3 and outputs the shaped multivalued digital signal waveform to the multilevel decision circuit 5. The digital filter 4 uses almost the same filter coefficients as those of a digital filter (not shown) provided in the multi-level coding unit 8 of the transmission unit.
The filter characteristics of the transmitting unit and the receiving unit are combined to form a roll-off filter that enables multi-value determination. The filter coefficients of the digital filter 4 are selected so as to correct the frequency characteristics deteriorated by the relay device transmitter 9 and the relay device receiver 10. The coefficient is determined by correcting the coefficient having a low-pass filter characteristic when the frequency characteristic around 7.5 MHz of the combined frequency characteristic of the relay device transmitting unit 9 and the relay device receiving unit 10 is increasing. The coefficient is calculated by combining with the off characteristic. Conversely, 7.5
Correction in the case where the frequency characteristic around MHz is reduced is performed by combining a coefficient having a high-pass filter characteristic with a roll-off characteristic and calculating the coefficient.

The multi-value determination circuit 5 includes a digital filter 4
The waveform of the shaped multi-level signal input from is determined to the multi-level, and the determination value is output to the parallel / serial conversion circuit 6. The parallel / serial conversion circuit 6 converts the determination value of the waveform of the multi-level digital signal input from the multi-level determination circuit 5 into serial binary digital signal data and outputs the data to another device. The other clock signal reproduction circuit 7 reproduces a clock signal synchronized with the multi-level signal input from the A / D conversion circuit 3 and converts the reproduced clock signal to A
The signal is output to the / D conversion circuit 3, digital filter 4, multi-value determination circuit 5, and parallel / serial conversion circuit 6. In addition,
The parallel / serial conversion circuit 6 outputs the clock signal input from the clock signal reproduction circuit 7 to another device together with the data.

Since the repeater of the present invention corrects the frequency characteristic for transmitting and receiving the FM modulated wave based on the multi-level analog signal from the repeater transmitter 9 to the repeater receiver 10, it does not perform automatic equalization. However, a good transmission error rate can be obtained. Although not shown in FIG. 1, if an automatic equalization circuit is further added to the multi-level decoding device shown in FIG. 1, the frequency characteristics of the relay device are not affected, and multipath and fading are not affected. Equalization ability can be improved.

[0018]

According to the present invention, a circuit for compensating for frequency characteristics degraded in an analog repeater transmitter and a repeater receiver constituting a digital repeater is provided in the receiver multilevel decoding device. And a relay apparatus that performs FM modulation / demodulation on the multi-level encoded signal and transmits the signal.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multi-level decoding device of a receiving unit of a relay device according to the present invention.

FIG. 2 is a block diagram of a relay device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low-pass filter (LPF) 2 Input signal level control circuit 3 A / D conversion circuit 4 Digital filter 5 Multi-value judgment circuit 6 Parallel / serial conversion circuit 7 Clock signal reproduction circuit 8 Transmitter multi-value coding device 9 FM modulation Transmitter for FM system 10 Relay receiver for FM demodulation 11 Receiver M-ary decoding device 12, 13 Antenna.

Claims (4)

[Claims] An input digital signal is subjected to a multi-level encoding process to obtain a multi-level encoded signal.
A multi-level encoding apparatus for transmitting a multi-level analog signal by performing a / A conversion, and performing a FM modulation on a carrier with the multi-level analog signal input from the multi-level encoding apparatus, until a required frequency is reached. A relay device transmitting unit that performs multiplication and power amplification and outputs an FM modulated wave of a required frequency; and an FM of the required frequency input from the relay device transmitting unit.
An antenna on a transmitting unit side for transmitting a modulated wave, an antenna on a receiving unit side for receiving the FM modulated wave of the required frequency transmitted from the antenna on the transmitting unit side, and the input from the antenna on the receiving unit side A relay device receiving section that amplifies and FM-demodulates an FM modulated wave of a required frequency and outputs the multi-level analog signal; and performs A / D conversion on the multi-level analog signal input from the relay device receiving section. Multi-level digital signal, the multi-level digital signal is subjected to waveform shaping, the shaped multi-level signal waveform is determined to a multi-level level, the determined value is converted to a binary digital signal, and the data is converted. A relay device, comprising: a receiving unit multi-level decoding device that outputs and compensates for frequency characteristics degraded by the relay device transmitting unit and the relay device receiving unit. 2. The relay apparatus according to claim 1, wherein the receiving unit multi-level decoding apparatus removes noise and unnecessary frequency band signals of the input multi-level analog signal, and converts the noise and unnecessary frequency band signals. A low-pass filter that outputs the removed multi-level analog signal; and a multi-level analog signal that removes the noise and unnecessary frequency band signals input from the low-pass filter to a required signal level. An input signal level control circuit for outputting a multi-level analog signal, and converting the multi-level analog signal of the required signal level inputted from the input signal level control circuit into a multi-level digital signal, and converting the converted multi-level digital signal. An A / D conversion circuit for outputting, and a digital for shaping the waveform of the multi-valued digital signal input from the A / D conversion circuit and outputting a waveform of the shaped multi-valued digital signal A multi-level decision circuit for determining a waveform of the shaped multi-level digital signal input from the digital filter to a multi-level level, and outputting a decision value of the waveform of the multi-level digital signal; A relay device, comprising: a parallel / serial conversion circuit that converts a determination value of a waveform of a multilevel digital signal input from a circuit into serial binary digital signal data and outputs the converted data. 3. The relay device according to claim 1, wherein the multi-level decoding device includes a low-pass filter that outputs a multi-level analog signal from which noise and unnecessary frequency band signals have been removed. An input signal level control circuit for outputting a multi-level analog signal having a required signal level is provided with a frequency characteristic for performing an inverse correction of a frequency characteristic deteriorated in the repeater transmitter and the repeater receiver. Relay device. 4. The relay device according to claim 1, wherein the multi-level decoding device in the receiving unit includes: a digital filter for outputting a waveform of the shaped multi-valued digital signal; A relay device comprising: a filter coefficient set so as to correct a frequency characteristic deteriorated by a unit.