JP2001144643A - Receiver, transmitter-receiver and transmission reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission reception method where a reference signal generator with high frequency precision is provided only to a control station A and the frequency precision of a station B to be controlled is enhanced to the same as that of the control station A with a simple configuration. SOLUTION: The control station A transmits two common carriers having a prescribed frequency interval. The station B to be controlled extracts the frequency interval of the received common carriers through frequency conversion or the like and uses the extracted frequency signal as a reference signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus, a transmitting / receiving apparatus, and a transmitting / receiving method. Technology suitable for the system to be performed.

[0002]

2. Description of the Related Art Conventionally, for example, a control station A 'which is a master station (HUB) as shown in FIG.
T), a transmission / reception apparatus used in a satellite communication system that communicates voice, data, and the like via the communication satellite C with the controlled station B ′. Frequency drift is relatively large, and it is not easy for a normal receiving apparatus to suppress a carrier frequency error within an AFC (frequency correction) range. On the other hand, if a wide range carrier search is performed every time a line is allocated in order to follow the frequency drift of the communication satellite, the line cannot be set in a short time.

As a method for addressing these problems, FIG.
As shown in the carrier layout diagram, a pilot signal 202 is constantly transmitted from a control station (master station) A ′ separately from a plurality of carrier signals 201 to be used, and a plurality of controlled stations (slave stations)
For the receiver of B ′, a method of performing frequency correction based on the pilot signal 202 is used.

FIG. 9 shows an example of a demodulation section in a conventional transmitting / receiving apparatus. Pilot signal demodulator 302 first performs a carrier search to pull in the pilot signal,
The frequency converter 301 performs frequency correction to pull in the pilot signal, and thereafter receives the pilot signal while constantly performing frequency correction. As a result, the signals that have absorbed the satellite drift are input to the demodulators 303 and 304 for each communication line. When the communication line is allocated, the demodulators 303 and 304 for the communication line
It waits around the desired carrier frequency and starts demodulation when a carrier is received within the AFC range inside each demodulator.

[0005]

However, in the above-described conventional example of receiving a pilot signal from a control station and correcting the frequency, the communication satellite C as described below is used.
Cannot correct the frequency error at the time of communication between the controlled stations B 'and B' via

That is, when the signal transmitted from the control station A 'is received by the controlled station B', the frequency drift of the satellite is Δf1, and the transmission frequency error of the control station A 'is Δf1.
f2, assuming that a frequency error caused by frequency conversion or the like at the time of reception at the controlled station B ′ is Δf3, a pilot signal is received and subjected to frequency correction, so that Δf2 other than Δf1,
The frequency error can be absorbed including Δf3.

However, when a signal transmitted from the controlled station B 'is received by another controlled station B', the pilot signal from the control station A 'is also received and frequency correction is performed. The frequency error of the transmission signal of the control station B ′ is Δf4
Then, the frequency errors Δf1, Δf3, Δf of the received signal
4, whereas the frequency error Δf1,
The correction of Δf2 and Δf3 is performed, and as a result, frequency errors of Δf2 and Δf4 occur.

[0008] Therefore, the frequency error is reduced by A inside the demodulator.
In order to keep the frequency within the FC range, both the transmitting station and the receiving station require high frequency accuracy. Therefore, it is necessary to use an expensive reference signal generator that generates a reference signal used for frequency conversion of the transmission system and the reception system with high accuracy, or to periodically adjust the frequency of the reference signal.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a reference signal generator having high frequency accuracy only in a control station, and to make the frequency accuracy of a controlled station equal to that of the control station with a simple configuration. And

[0010]

In order to achieve the above-mentioned object, the present invention is configured as follows.

That is, a receiving apparatus of the present invention is a receiving apparatus for performing frequency conversion using a reference signal, wherein the receiving means receives at least two pilot signals transmitted at a constant frequency interval; Extracting means for extracting a frequency interval between two pilot signals, wherein a frequency signal having the extracted frequency interval is used as the reference signal.

According to the present invention, the frequency accuracy of the frequency interval extracted from the two received pilot signals depends on the frequency accuracy of the reference signal generator in the transmitting station, for example, the control station. When used as a reference signal of the receiving device, the frequency accuracy of the reference signal can be made equal to that of the control station on the transmitting side.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION
A receiving device that performs frequency conversion using a reference signal,
Receiving means for receiving at least two pilot signals transmitted at a constant frequency interval; and extracting means for extracting a frequency interval between the received two pilot signals, wherein the frequency signal having the extracted frequency interval is referred to as the reference signal. According to the first aspect of the present invention, the frequency accuracy of the frequency interval extracted from the two received pilot signals is equal to the frequency accuracy of the reference signal generator in the transmitting station, for example, the control station. If the extracted frequency signal is used as a reference signal of the receiving apparatus, the frequency accuracy of the reference signal can be made equal to that of the control station on the transmission side.

According to a second aspect of the present invention, there is provided a transmitting / receiving apparatus for performing frequency conversion using a reference signal, wherein the receiving means receives at least two pilot signals transmitted at a constant frequency interval; Extracting means for extracting a frequency interval between two pilot signals, wherein a frequency signal having the extracted frequency interval is used as the reference signal of at least one of a transmission system and a reception system. According to this, the frequency accuracy of the frequency interval extracted from the two received pilot signals depends on the frequency accuracy of the reference signal generator in the transmitting station, for example, the control station. , The frequency accuracy of the reference signal can be made equal to that of the control station on the transmission side.

According to a third aspect of the present invention, in the second aspect of the invention, the two pilot signals are unmodulated waves. The configuration is relatively simple, and the occupied bandwidth of the unmodulated wave is small, so that the frequency use efficiency does not deteriorate.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the two pilot signals are modulated waves, and according to the fourth aspect of the present invention, each pilot signal has arbitrary information. Since modulation can be applied, these pilot signals can be used not only as a means for transmitting a reference signal but also as a control line or a communication line.

According to a fifth aspect of the present invention, in the second aspect, one of the two pilot signals is an unmodulated wave and the other is a modulated wave. The pilot signal which is a modulated wave may be used for a control line or a communication line, and only one unmodulated wave may be added as a pilot signal.

According to a sixth aspect of the present invention, the transmitting side transmits at least two pilot signals at a constant frequency interval, and the receiving side receives the pilot signal and extracts the frequency interval, and extracts the extracted frequency. The frequency conversion is performed using the frequency signal of the interval as a reference signal of at least one of the transmission system and the reception system. According to the invention of claim 6, the frequency interval of the frequency interval extracted from the two received pilot signals is determined. Since the frequency accuracy depends on the frequency accuracy of the reference signal generator on the transmission side, if the extracted frequency signal is used as the reference signal on the reception side, the frequency accuracy of the reference signal can be made equal to that on the transmission side. .

According to a seventh aspect of the present invention, there is provided a transmitting / receiving apparatus for performing frequency conversion of at least one of a transmitting system and a receiving system using a reference signal, wherein a pilot signal modulated and transmitted by a signal of a fixed frequency is transmitted. Receiving means for receiving, and demodulation means for demodulating the signal of the predetermined frequency from the received pilot signal, wherein the demodulated signal is used as a reference signal of at least one of a transmission system and a reception system. According to the invention described in Item 7, since the frequency accuracy of the transmitted pilot signal depends on the frequency accuracy of the reference signal generator on the transmitting side, if the received demodulated signal is used as the reference signal on the receiving side, the reference signal Can be made equivalent in frequency accuracy to that of the transmitting side.

An invention according to claim 8 is a transmitting / receiving apparatus for performing frequency conversion of at least one of a transmitting system and a receiving system using a reference signal, wherein a receiving means for receiving a modulated signal to be transmitted; And a clock reproducing means for reproducing a clock of a fixed frequency reproduced from the signal, wherein the reproduced clock is used as a reference signal of at least one of a transmission system and a reception system. The frequency conversion of at least one of the transmission system and the reception system is performed using the recovered clock as a reference signal. According to the invention of claim 8, a synchronization clock is supplied from a control line used for controlling each station. Since this clock can be extracted, it is necessary to transmit an extra pilot signal to transmit the reference signal by using this clock as the reference signal. No.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 shows a VSAT (Very Sma) which is an example of a satellite communication system to which the present invention is applied.
ll Aperture Terminal) is a schematic configuration diagram of the system,
The VSAT system includes a control station A which is a master station (HUB) and a controlled station B which is a number of slave stations (VSAT), and performs communication of voice, data, and the like via a communication satellite C. It is.

An object of the present invention is to provide a reference signal generator having high frequency accuracy only in the control station A and to make the frequency accuracy of the controlled station B equal to that of the control station A with a simple configuration. The transmitting / receiving device of the controlled station B has the configuration shown in FIG.

In FIG. 2, a signal received by an antenna 11 is sent to a receiving system by a duplexer (Feed Duplex) 12, and an unnecessary wave component is removed by a band limiting filter (BPF) 13, followed by frequency conversion. (LNC: Low Noise Co)
nverter) 14 to convert to an intermediate frequency. The output of the frequency converter is supplied to a demodulator (DEM) via the IF cable 15a.
OD) 16. On the other hand, the output of the modulator (MOD) 17 is supplied to the frequency conversion circuit (U
/ C: Up Converter (HPA) 1 after being sent to an up converter 18 and converted into a transmission frequency.
9 and a band limiting filter (BPF) 20
After the unnecessary wave components have been removed at, the signal is sent from the duplexer 12 to the antenna 11 and emitted toward the communication satellite C.

The transmission / reception apparatus of this embodiment includes a control station A
Receive the two pilot signals transmitted from the base station, extract the frequency interval between the pilot signals, and perform frequency conversion of the receiving system and the transmitting system using the frequency signal of the frequency interval as a reference signal.

For this reason, the transmitting and receiving apparatus is provided with receiving means such as an antenna 11 and a demultiplexer 12 for receiving a pilot signal as in the prior art, and further includes a reference signal which is a frequency signal having a frequency interval between two pilot signals. A reference signal extraction circuit 21 is provided as extraction means for extracting a signal.

The reference signal extracting circuit 21 includes frequency converters (D / C: Down Converters) 22 and 24, band limiting filters (BPFs) 23a and 23b, and an amplifier 25. This is to extract a reference signal of a frequency difference between two pilot signals transmitted from A.

The reference signal generator (Ref.) 26
Is a reference signal generator used only at the time of pilot signal acquisition, and may have low frequency accuracy.

Next, an operation until a reference signal is obtained will be described.

FIG. 3 shows an example of the carrier arrangement. 401
a and 401b are pilot signals transmitted from the control station A, which are unmodulated waves in this embodiment. Also, 4
02 is a communication line carrier signal, and 403 is a video / data carrier signal.

When the controlled station B equipped with the transmitting / receiving device of this embodiment is started up, the changeover switch 27 in FIG. 2 is set to the reference signal generator 26 side. Two pilot signals 401a, 401 transmitted from the control station
01b is distributed to the reference signal extraction circuit 21 from the output of the frequency converter 14, and unnecessary band components are removed by band limiting filters 23a and 23b.
After each extraction of 401b, the frequency interval is extracted by the frequency converter 24. The output of the frequency converter 24 is amplified by the amplifier 25, and is used as a reference signal of the transmission / reception device by switching the switch 27 to the reference signal extraction circuit 21.

In FIG. 2, the reference signal is distributed only to the frequency converters 14 and 18 which require high frequency accuracy, but it is needless to say that the reference signal may be used for the demodulator 16 and the modulator 17. Nor.

Here, the frequency accuracy of the extracted reference signal will be described.

Assuming that the frequency interval between two pilot signals transmitted from the control station A is Δfr and the transmission frequency error of the control station A is Δf2, one of the frequencies of the two pilot signals can be expressed as fup + Δf2 and the other as fup + Δf2 + Δfr. The received pilot signal includes a satellite drift Δ
f1, a frequency error Δf3 generated at the time of reception is added,
The frequency of the received pilot signal is fdn +
Δf2 + Δf1 + Δf3, fdn + Δf2 + Δfr + Δ
f1 + Δf3. Here, fdn is a value corresponding to the return frequency at the satellite with respect to the frequency fup. Here, when the frequency interval between the two received pilot signals is extracted, only Δfr is extracted as the difference. Since the frequency accuracy of the difference Δfr depends on the frequency accuracy of the reference signal generator in the control station A, this signal is
Is used as the reference signal for all the controlled stations B
Can be made to have the same frequency accuracy as that of the control station A.

Therefore, each controlled station B does not need to include a reference signal generator with high frequency accuracy. Further, in this embodiment, since both pilot signals are unmodulated waves, the received pilot signals are separated by a band-limiting filter, and one signal is frequency-converted by the other signal, so that the frequency interval is reduced. It can be extracted and has a simple configuration. Moreover, since the occupied bandwidth of the unmodulated wave is small, the present invention can be realized at low cost without deteriorating the frequency use efficiency.

As another embodiment of the present invention, in order to absorb the satellite drift, the demodulator 16 may demodulate a pilot signal and the frequency converter 22 may perform frequency correction. In this case, since the bandwidth of the band limiting filters 23a and 23b can be narrowed, a high C / N reference signal can be obtained.

As a specific numerical example of this embodiment,
Transmission frequency 14.5 GHz, reception frequency 12 GHz, modulator output frequency 140 MHz, demodulator input frequency 1.2
GHz, the frequency interval of the pilot signal is 10 MHz, and the communication line is QPSK modulated at 70 kbps.
Since the frequency drift of the satellite is about ± 15 kHz and the AFC range inside the demodulator is about ± 3 kHz, the initial carrier search range of the pilot signal is ± 20 kHz, and the frequency error of the control station is ± 1.5 kHz or less (about 0.1 ppm). )
What should I do?

(Embodiment 2) FIG. 4 shows the configuration of a transmitting / receiving apparatus according to Embodiment 2 of the present invention. The transmitting and receiving apparatus of this embodiment corresponds to a case where both pilot signals transmitted from control station A are modulated waves, and basically has a configuration similar to that of the above-described first embodiment. The same or similar parts are denoted by the same reference numerals,
Description is omitted.

In this embodiment, the first embodiment is used.
The demodulator 16 has a configuration including an extraction circuit for extracting a frequency signal at a frequency interval between two pilot signals as a reference signal.

That is, in the transmitting / receiving apparatus of this embodiment, the received pilot signal is sent to reference signal extracting circuit 500 including a demodulator, and frequency converter 505
As in the prior art, the satellite drift is absorbed and input to the demodulators 501a and 501b. Then, carrier reproduced signals 502a and 502b corresponding to each pilot signal reproduced inside the demodulator are input to a frequency converter 503 to extract a frequency interval, amplified by an amplifier 504, and then switched via an IF cable 15c. And is used as a reference signal.

According to the transmission / reception apparatus of this embodiment, the frequency accuracy of the reference signal is
It can be made equivalent to the control station A, and there is no need to provide a reference signal generator with high frequency accuracy.

Since the two pilot signals are both modulated waves, any information modulation can be applied to each pilot signal. Therefore, these pilot signals can be used only as a means for transmitting a reference signal. Not
Can be used as a control line or a telephone line.

(Embodiment 3) FIG. 5 shows a configuration of a reference signal extraction circuit of a transmission / reception apparatus according to Embodiment 3 of the present invention, and is a portion corresponding to reference signal extraction circuit 500 in FIG. The same or similar parts as those of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

The transmission / reception apparatus of this embodiment comprises a control station A
This corresponds to a case where two transmitted pilot signals are a modulated wave and an unmodulated wave. Among the received pilot signals, the modulated wave is demodulated by the demodulator 501a, and the unmodulated wave is a band-limited filter. (BPF) 601. Then, the carrier reproduction signal 502 of the demodulator 501a
a to the frequency converter 50
3, and the frequency interval is extracted. Other operations are
This is the same as in the second embodiment.

According to the transmission / reception apparatus of this embodiment, the frequency accuracy of the reference signal is
It can be equivalent to a control station, and does not need to include a reference signal generator with high frequency accuracy.

One of the pilot signals is a modulated wave and the other is a non-modulated wave. In a satellite communication network, a control line is used for controlling each station. Therefore, one of the pilot signals is used for this control line. The other unmodulated wave
Only one wave needs to be added and can be easily implemented.

(Embodiment 4) FIG. 6 shows a configuration of a reference signal extracting circuit of a transmitting / receiving apparatus according to Embodiment 4 of the present invention.
The same reference numerals are given.

The transmission / reception circuit of this embodiment comprises a control station A
This shows a case where the transmitted pilot signal is one modulated wave, and a modulated wave modulated with a reference signal having a constant frequency is transmitted from control station A as a pilot signal.

The pilot signal received by the transmitting / receiving apparatus of this embodiment is input to demodulator 501a, and demodulation result 502a output from demodulator 501a is used as a reference signal. Other operations are the same as those in the second embodiment.

According to the transmitting / receiving apparatus of this embodiment, the pilot signal modulated by the reference signal is received from the control station A, and the demodulation result of the received signal is used as the reference signal. Since the accuracy of the transmitted modulated signal depends on the frequency accuracy of the reference signal generator in the control station A, the frequency accuracy of the reference signal received and demodulated by the transmission / reception device is equal to the frequency accuracy of the control station A.

Further, as another embodiment of the present invention,
A synchronous clock reproduced inside the demodulator 501a is used as a demodulator output 502a.
a may be used as a reference signal. In this case, there is no need to transmit an extra pilot signal for transmitting the reference signal.

(Other Embodiments) The two pilot signals in the first to third embodiments can be arranged at an arbitrary frequency on the satellite transponder if a certain frequency interval is maintained. Can be arranged between two video signals or on different transponders.

Although the above embodiments have been described with reference to the satellite communication system, the present invention is not limited to the satellite communication system, but may be applied to any base station or terminal in which frequency accuracy must be kept high. It is applicable to the system.

In each of the above embodiments, the present invention is applied to a transmitting / receiving apparatus, but the present invention is not limited to the transmitting / receiving apparatus, but may be applied to a mere receiving apparatus.

In the first to third embodiments, the number of pilot signals is two, but a pilot signal may be added.

[0056]

As described above, according to the present invention, on the receiving side such as a controlled station, the same frequency accuracy as that of the control station can be obtained on the receiving side such as the controlled station by using the pilot signal transmitted from the transmitting side such as the controlling station. This makes it possible to reduce costs by using a low-cost reference signal generator on the receiving side, and eliminates the need to periodically adjust the frequency of the reference signal generator. The associated costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a satellite communication system to which the present invention is applied.

FIG. 2 is a circuit diagram showing a configuration of a transmission / reception device according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a carrier arrangement according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a transmitting and receiving apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a reference signal extraction circuit according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a reference signal extraction circuit according to a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a satellite communication system.

FIG. 8 is a conventional carrier layout diagram.

FIG. 9 is a circuit diagram illustrating a configuration of a demodulation unit in a conventional transmission / reception device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 transmitting / receiving antenna 12 duplexer 14 frequency converter 15 a, 15 b IF cable 16 demodulator 17 modulator 18 frequency converter 19 amplifier 21 reference signal extraction circuit 22, 24 frequency converter 27 switch

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Sakakura 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5K011 CA06 DA03 DA15 EA01 FA07 JA04 KA04 LA06 5K042 AA05 BA14 CA02 CA11 CA13 DA21 EA01 EA06 FA11 FA30 JA01 JA04 LA11 NA04 5K052 AA01 AA03 BB10 DD17 EE15 EE24 EE35 FF26 GG26 5K067 AA24 DD25 EE02 EE07 EE32 EE67 5K072 AA02 AA22 BB22 DD06 DD17 EE09 EE27 FF13 GG01

Claims (8)

[Claims] 1. A receiving apparatus for performing frequency conversion using a reference signal, comprising: receiving means for receiving at least two pilot signals transmitted at a fixed frequency interval; and a frequency interval between the received two pilot signals. Extracting means for extracting frequency signals, wherein a frequency signal of the extracted frequency interval is used as the reference signal. 2. A transmitting / receiving apparatus for performing frequency conversion using a reference signal, comprising: receiving means for receiving at least two pilot signals transmitted at a constant frequency interval; and a frequency interval between the received two pilot signals. And a extracting means for extracting a frequency signal at a frequency interval as the reference signal of at least one of a transmission system and a reception system. 3. The transmitting / receiving apparatus according to claim 2, wherein the two pilot signals are unmodulated waves. 4. The transmitting / receiving apparatus according to claim 2, wherein the two pilot signals are modulated waves. 5. The transmitting and receiving apparatus according to claim 2, wherein one of the two pilot signals is a non-modulated wave and the other is a modulated wave. 6. A transmitting side transmits at least two pilot signals at a fixed frequency interval, and a receiving side receives the pilot signal, extracts the frequency interval, and transmits a frequency signal at the extracted frequency interval. A transmission / reception method, wherein frequency conversion is performed using a reference signal of at least one of a system and a reception system. 7. A transmitting and receiving apparatus for performing frequency conversion of at least one of a transmitting system and a receiving system using a reference signal, comprising: receiving means for receiving a pilot signal modulated and transmitted by a signal of a constant frequency; Demodulating means for demodulating the signal of the predetermined frequency from the received pilot signal, wherein the demodulated signal is used as a reference signal of at least one of a transmission system and a reception system. 8. A transmitting and receiving apparatus for performing frequency conversion of at least one of a transmitting system and a receiving system using a reference signal, comprising: a receiving unit for receiving a modulated signal to be transmitted; A transmission / reception apparatus, comprising: clock recovery means for recovering a frequency clock; and using the recovered clock as a reference signal for at least one of a transmission system and a reception system.