JP2002094431A - Transmission afc device and transmission system monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect frequency shift in a CDM-SS reception signal for a short time period. SOLUTION: A CDM-SS reception signal is input into a despreading circuit 21. This despreading circuit 21 fetches, in a transmission data the sequence of all the channels from a transmission system via a delay circuit 22, and despreads the CDM-SS reception signal in the transmission data sequence of all the channels. A frequency measuring circuit 23 extracts a unmodulated signal part from the despreading signal obtained by the despreading circuit 21 to acquire its frequency, thereby measuring a deviation amount Δf, in terms of a prescribed satellite transmission frequency. According to this approach, since the CDM-SS signal is despread, if the number of multiple channels is N, as compared with the case of using one CDM channel, a SN ratio is improved by N folds. Accordingly, it is possible to obtain a signal ensuring the sufficient SN ratio without having to use processing of integration, etc., and a large-sized antenna, and to carry out a frequency measurement for a short time interval, and to follow an early frequency shift caused by a satellite repeater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDM-SS (Code Division Multiple Link) caused by a terrestrial transmitting station or a satellite repeater in a broadcasting system or a communication system using a satellite.
iplex-Spread Spectrum: Transmission AFC that corrects the frequency deviation of the signal on the transmission side.
The present invention relates to an (Automatic Frequency Control) device and a transmission system monitoring device that monitors the presence or absence of an abnormality in a transmission system.

[0002]

2. Description of the Related Art As is well known, in a satellite broadcasting system and a satellite communication system including a terrestrial transmitting station, a satellite repeater, and a terrestrial receiving station, a frequency shift caused by the terrestrial transmitting station and the satellite repeater is reduced. It needs to be corrected by AFC. AFC can be performed by a terrestrial transmitting station and a terrestrial receiving station. However, in the above-described system, the number of terrestrial receiving stations is large, and the simplicity of the AFC device configuration on the terrestrial receiving station side reduces cost. Desirable in a sense. Therefore, a higher control function is usually required for the AFC on the ground transmitting station side. AFC performed by the terrestrial transmitting station is called transmitting AFC.

The transmission AFC receives a signal transmitted from a satellite repeater, measures a deviation from the center frequency, and transmits the signal with a transmission frequency offset so as to cancel the deviation. The cause of the frequency deviation of the received signal includes the frequency deviation of the reference signal of the ground transmitting station, but the influence of the satellite motion and the frequency deviation of the reference signal in the frequency converter in the satellite repeater is large.

The frequency shift caused by the satellite repeater has a fast change speed, and this detection needs to be performed in a short time. However, since the signal transmitted from the satellite repeater is weak on the ground, a sufficient signal power to noise power ratio (SN ratio) cannot be obtained, and it is necessary to integrate over a long period of time. The request to detect the deviation cannot be met.

[0005] In addition, the method for increasing the size of the receiving antenna is referred to as S.
Although the N ratio can be improved, there is a problem that the equipment becomes large and the cost of the apparatus increases.

[0006]

As described above, in the transmission AFC device used in the conventional satellite broadcasting system or satellite communication system, the frequency shift caused by the satellite repeater has a fast change speed and is detected in a short time. Despite the necessity, the signal from the satellite repeater is weak on the ground, and a sufficient signal power to noise power ratio (SN ratio) cannot be obtained. Cannot respond to that request. In addition, although the SN ratio can be improved by a method of increasing the size of the receiving antenna, there are problems that the equipment becomes large and the cost of the apparatus increases.

[0007] The present invention solves the above problems, and a transmission AFC device capable of detecting a frequency shift of a received CDM-SS signal without using a large antenna in a short time and correcting the frequency shift. Further received CDM
An object of the present invention is to provide a transmission system monitoring device capable of monitoring the presence or absence of a transmission system abnormality from an SS signal for each CDM channel.

[0008]

In order to achieve the above object, a transmitting AFC apparatus according to the present invention provides a transmitting data sequence of a plurality of channels at a terrestrial transmitting station by a CDM modulator using a CDM modulator.
Used in a satellite communication system or a satellite broadcasting system for converting the CDM-SS signal to a service area via a satellite repeater.
Delay means for branching and delaying transmission data sequences of all channels input to the M modulator, and despreading a received signal from the satellite repeater based on the transmission data sequences of all channels delayed by the delay means Despreading means, and frequency measuring means for measuring a satellite transmission frequency from the signal despread by the despreading means, and the terrestrial transmission of the CDM-SS signal based on the measurement result of the frequency measuring means. It is characterized in that a frequency shift caused by a station or a satellite repeater is corrected.

In particular, the delay means applies a delay corresponding to a delay time via a satellite repeater to a transmission data sequence.

Further, the frequency measuring means extracts a non-modulated signal component from the despread signal and measures the frequency of the extracted component.

On the other hand, a transmission system monitoring apparatus according to the present invention provides a terrestrial transmitting station for transmitting a transmission data sequence by CDM (code division multiplexing).
The modulator is used in a satellite communication system or a satellite broadcasting system that converts the signal into a CDM-SS (code division multiplex spread spectrum) signal through a satellite repeater to a service area via a satellite repeater. CDM
Delay means for branching and delaying a transmission data sequence input to the modulator; despreading means for despreading a reception signal from the satellite repeater based on the transmission data sequence delayed by the delay means; Power measuring means for measuring the power of the signal despread by the despreading means, wherein the presence or absence of an abnormality in the transmission system is monitored based on the measurement result of the power measuring means.

In particular, when the terrestrial transmitting station multiplexes transmission data sequences of a plurality of channels to generate the CDM-SS signal, the transmission data sequences are input to the despreading means through the delay means for each channel. Thus, the presence or absence of an abnormality for each channel is monitored.

[0013] Further, the delay means applies a delay corresponding to a delay time via a satellite repeater to a transmission data sequence.

Further, the power measuring means extracts an unmodulated signal component from the despread signal and measures the power of the extracted component.

That is, the transmission AFC device and the transmission system monitoring device having the above-described configuration branch and delay the data sequence input to the CDM modulator, and receive a signal from the satellite repeater based on the delayed data sequence. Is despread, and the frequency and power of the despread signal are measured.

The received signal from the satellite repeater is a CDM-SS
It is a signal and the carrier center frequency cannot be measured as it is. However, since the transmission data sequence is known at the terrestrial transmitting station, these are branched and re-modulated to the received signal from the satellite repeater to perform despreading. However, a delay corresponding to the delay time via the satellite repeater needs to be given to the transmission data sequence. The despread signal contains an unmodulated signal component, which is extracted and the frequency is measured.

According to this method, all of the SS signals subjected to CDM multiplexing are despread, so that if the number of multiplexed channels is N, the SN ratio is N times larger than in the case of using one CDM channel. To be improved. Therefore, neither processing such as integration nor use of a large antenna is required, and sufficient SN
As a result, a signal whose ratio is secured can be obtained, and the frequency can be measured in a short time. Since the frequency can be measured in a short time, an AFC that can follow a fast frequency shift caused by the satellite repeater can be realized.

If the power of the unmodulated component after despreading is measured using the transmission data sequence of a specific CDM channel instead of using the entire CDM transmission data sequence, the C
The operation of the transmission system of the DM channel can be monitored.
If there is an abnormality in the transmission system of the CDM channel, it can be detected by lowering the level of the unmodulated component.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a system of a general transmission AFC system in a communication or broadcasting system using a satellite.

First, the terrestrial transmitting station 11 inputs a transmission data sequence of a plurality of channels to the CDM modulator 111, and performs frequency spread modulation with a local signal (transmission frequency) from the local oscillator 112 to convert it to a CDM-SS signal. rear,
The signal is transmitted from the transmitting antenna 113 to the satellite repeater 12.

In the satellite repeater 12, the receiving antenna 121
Then, after receiving the transmission wave from the ground transmission station 11 and frequency-converting it by the frequency converter 122 using the local signal from the local oscillator 123, the signal is transmitted from the transmission antenna 124 toward a predetermined service area. The frequency shift generated in the transmission output is the sum of the transmission frequency shift of the ground transmitting station 11, the local frequency shift of the satellite repeater 12, the Doppler shift due to the satellite motion, and the like.

The terrestrial transmitting station 11 fetches the transmitted wave from the satellite repeater 12 by the receiving antenna 114 installed in the service area, detects and detects the received wave by the AFC receiver 115, and detects the frequency deviation from the specified satellite transmission frequency. Measure Δf. Then, the frequency controller 116 obtains a ground station transmission frequency offset amount Δf ′ for correcting the measured frequency deviation amount Δf, and controls the local signal frequency of the local oscillator 112 based on the offset amount Δf ′. This implements transmission AFC.

FIG. 2 is a block diagram showing a specific configuration of the frequency shift amount measuring unit in the AFC receiver 115 as one embodiment of the transmission AFC device according to the present invention.

In this embodiment, first, a CD obtained by receiving and detecting a satellite transmission wave from the reception antenna 114 is obtained.
The M-SS signal is input to the frequency despreading circuit 21. The frequency despreading circuit 21 fetches transmission data sequences of all channels from the transmission system via the delay circuit 22 and
The DM-SS signal is frequency despread with transmission data sequences of all channels. Here, the delay circuit 22 is for giving a delay corresponding to the transmission data sequence of all channels via a satellite repeater to synchronize with the received CDM-SS signal. The frequency measuring circuit 23 extracts a non-modulated portion from the despread signal obtained by the frequency despreading circuit 21 to obtain the frequency, and calculates a deviation ΔΔ from a specified satellite transmission frequency.
Measure f.

In other words, the transmitting AFC system having the above-described configuration uses the AFC receiver 115 of the ground transmitting station 11 to transmit
The transmission data sequences of all the channels input to the DM modulator 111 are fetched and delayed, and the reception signal from the satellite repeater 12 is despread based on the delayed transmission data sequences of all the channels and despread. This is achieved by measuring the frequency of the signal.

The signal received from the satellite repeater 12 is a CDM-
This is an SS signal, and the carrier center frequency cannot be measured as it is. However, the terrestrial transmitting station 11 knows the transmission data sequences of all channels. So, AFC
The receiver 114 performs frequency despreading of the received signal from the satellite repeater 12 using the transmission data sequences of all the channels. At this time, a delay corresponding to the delay time via the satellite repeater 12 is given to the transmission data sequence, and the satellite repeater 1
2. Synchronization with the CDM-SS signal from the second device. The despread signal contains an unmodulated signal component, which is extracted and the frequency is measured.

According to this method, all SS signals multiplexed by the CDM method are despread, so that if the number of multiplexed channels is N, the SN ratio is lower than in the case where one CDM channel is used. It is improved by N times. Therefore, a sufficient SN can be obtained without processing such as integration or using a large antenna.
As a result, a signal whose ratio is secured can be obtained, and the frequency can be measured in a short time. Since the frequency can be measured in a short time, an AFC that can follow a fast frequency shift caused by the satellite repeater 12 can be realized.

FIG. 3 is a block diagram showing an embodiment of a transmission system monitoring apparatus according to the present invention, which utilizes a despreading process using a transmission data sequence of a CDM-SS signal. here,
A case where the system is used in the system configuration shown in FIG. 1 will be described.

In the present embodiment, first, a CD obtained by receiving and detecting a satellite transmission wave from the reception antenna 114 is obtained.
The M-SS signal is input to the frequency despreading circuit 31. The frequency despreading circuit 31 fetches a transmission data sequence of a channel to be monitored from a transmission system via a delay circuit 32, and frequency despreads the received CDM-SS signal with the fetched transmission data sequence. Here, the delay circuit 32 is for giving a delay corresponding to the transmission data sequence to be monitored via the satellite repeater to synchronize with the received CDM-SS signal. The power measuring circuit 33 extracts a non-modulated signal portion from the despread signal obtained by the frequency despreading circuit 31, measures its power, and outputs it as a transmission data sequence monitoring signal. When the transmission data sequence includes a plurality of channels, a monitoring device may be provided for each channel, but may be sequentially switched and input to the frequency despreading circuit 31 via the delay circuit 32.

That is, the transmission system monitoring apparatus having the above configuration branches and delays the transmission data sequence input to the CDM modulator 111, and receives the reception signal from the satellite repeater 12 based on the delayed transmission data sequence. Is despread, and the power of the despread signal is measured.

As described above, the received signal from the satellite repeater 12 is a CDM-SS signal, and the received power of each channel cannot be measured as it is. However, the terrestrial transmitting station 11 knows the transmission data sequence. Therefore,
Satellite repeater 1 using transmission data sequence to be monitored
2 is subjected to frequency despreading of the received signal. At this time, a delay corresponding to the delay time via the satellite repeater 12 is given to the transmission data sequence, and the CDM-SS
Synchronize with signals. The signal after despreading contains an unmodulated signal component, and the power is measured by extracting this.

According to this method, the power of the unmodulated component after despreading is measured using the transmission data sequence of a specific CDM channel, so that the transmission state of the transmission system of that channel can be monitored. That is, if there is an abnormality in the transmission system of the channel to be monitored, the level of the unmodulated signal component decreases. By comparing the level with the reference value, it is possible to detect whether or not an abnormality has occurred in the transmission system. .

[0034]

As described above, according to the present invention, there is provided a transmission AFC apparatus capable of detecting a frequency shift of a received CDM-SS signal without using a large antenna in a short time and correcting the frequency shift. , And received CDM-
It is possible to provide a transmission system monitoring device capable of monitoring the presence or absence of a transmission system abnormality from an SS signal for each CDM channel.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system diagram of a general transmission AFC system in a communication or broadcast system using a satellite.

FIG. 2 is a block diagram showing a specific configuration of a frequency shift amount measuring unit in the AFC receiver of the AFC system as one embodiment of the transmission AFC device according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a transmission system monitoring device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ground transmission station 111 ... CDM modulator 112 ... Local oscillator 113 ... Transmission antenna 114 ... Receiving antenna 115 ... AFC receiver 116 ... Frequency controller 12 ... Satellite repeater 121 ... Receiving antenna 122 ... Frequency converter 123 ... Local oscillator 124 transmission antenna

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 1/707 H04J 13/00 D H04L 27/227 H04L 27/22 B F term (Reference) 5K004 AA05 FD05 FG05 FG03 5K022 EE01 EE21 EE31 5K042 AA05 BA00 CA13 DA16 FA08 JA01 NA04 5K072 AA19 BB22 BB27 CC20 DD01 DD15 EE09 GG02 GG15 GG34 GG37 GG39 HH01

Claims (7)

[Claims] A terrestrial transmitting station multiplexes transmission data sequences of a plurality of channels with a CDM (Code Division Multiplexing) modulator using a CDM-S
S (code division multiplex-spread spectrum) signal,
It is used in a satellite communication system or a satellite broadcasting system that sends out this CDM-SS signal to a service area via a satellite repeater. The transmission data sequence of all channels input to the CDM modulator is branched and delayed. Delay means; despreading means for despreading the received signal from the satellite repeater based on the transmission data sequence of all channels delayed by the delay means; Frequency measuring means for measuring a frequency, and the CDM- based on a measurement result of the frequency measuring means.
A transmission AFC (automatic frequency control) device for correcting a frequency shift of an SS signal caused by the terrestrial transmitting station or the satellite repeater. 2. A transmission AFC apparatus, wherein said delay means applies a delay corresponding to a delay time via a satellite repeater to a transmission data sequence. 3. The transmission AFC apparatus according to claim 1, wherein said frequency measuring means extracts an unmodulated signal component from the despread signal and measures the frequency of the extracted component. 4. A terrestrial transmitting station transmits a transmission data sequence by CDM.
The signal is converted into a CDM-SS (code division multiplex-spread spectrum) signal by a (code division multiplex) modulator.
Delay means for use in a satellite communication system or a satellite broadcast system for transmitting an S signal toward a service area via a satellite repeater, for branching and delaying a transmission data sequence input to the CDM modulator; Despreading means for despreading the received signal from the satellite repeater based on the transmission data sequence delayed by the means, and power measuring means for measuring the power of the signal despread by the despreading means. A transmission system monitoring device that monitors the presence or absence of an abnormality in a transmission system based on a measurement result of the power measurement unit. 5. When the terrestrial transmitting station multiplexes transmission data sequences of a plurality of channels to generate the CDM-SS signal, the transmission data sequence is input to the despreading unit through the delay unit for each channel. A transmission system monitoring apparatus characterized in that the presence or absence of an abnormality is monitored for each channel. 6. A transmission system monitoring apparatus according to claim 1, wherein said delay means applies a delay corresponding to a delay time via a satellite repeater to a transmission data sequence. 7. The transmission system monitoring apparatus according to claim 1, wherein said power measuring means extracts a non-modulated signal component from the despread signal and measures the power of the extracted component.