JP3460949B2 - Communication device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention is used in a communication system in which a master station and a plurality of slave stations communicate with each other via a repeater. In particular, it relates to a transmission frequency synchronization technique between slave stations and a reception frequency synchronization technique of a master station. The present invention is suitable for use in satellite communication.

[0002]

2. Description of the Related Art In a wireless communication system including a master station, a repeater (communication satellite in this case) and a plurality of slave stations, such as mobile satellite communication, in addition to the local oscillators of the master station and slave stations, relay The transmission and reception frequency also fluctuates due to the frequency error of the local oscillator of the device. Usually, in such a system, the local oscillators of the slave station and the repeater have to have relatively low frequency stability precision because of the problems of cost and use environment, and the frequency error becomes large. Especially when the transmission band is narrow, this frequency error cannot be ignored, so a frequency synchronization technique for compensating for this is used. Above all, a technique in which a signal from the master station is used as a pilot signal for a frequency reference is general.

FIG. 3 is a block diagram of a main part of a conventional communication device. In FIG. 3, a signal transmitted from the master station and the slave station to the repeater is defined as an upstream signal, and the frequency is F1 (for example, 14
(GHz) band. Further, the signal transmitted from the repeater to the master station and the slave station is defined as a downlink signal, and the frequency is in the F2 (for example, 12 GHz) band. The upstream signal frequency of the pilot signal transmitted from the master station to the slave station is F11 (F11 is F
1), and the downlink signal frequency is F21 (F21 = F11 +
F2-F1), the upstream signal frequency of the signal transmitted from the child station to the parent station is F12 (F12 is near F1), and the downstream signal frequency is F22 (F22 = F12 + F2-F1).

First, the master station 1 oscillates the transmitter local oscillator 121 at the frequency F11 and transmits it as the pilot signal A toward the repeater 2. The repeater 2 is a local oscillator 2
01 and the frequency converter 202, the pilot signal A
Is frequency-converted and transmitted again to the slave station 3 (pilot signal B).

Next, the slave station 3 controls the transmission frequency with the pilot signal B as a reference. That is, the slave station 3 receives the pilot signal B, compares it with the frequency of the receiving local oscillator 312 to obtain a deviation, and causes the correction frequency oscillator 304 to oscillate at a frequency equal to this deviation. Correction frequency oscillator 30
The output of 4 is input to the frequency converter 315, and the output signal of the transmission local oscillator 313 is frequency-converted to the frequency subtraction side. The frequency-converted signal is modulated by the modulator 306 and transmitted to the repeater 2 (signal C).

The signal C is frequency-converted by the repeater 2 (signal D), which the master station 1 receives. The above operation will be described by using mathematical expressions. The oscillation frequency of each local oscillator before frequency synchronization is set as follows.

Master station transmitting local oscillator 121: F11 + Δf1 Master station receiving local oscillator 112: F22 + Δf2 Repeater local oscillator 201: F2-F1 + Δf3 Slave station transmitting local oscillator 313: F12 + Δf4 Slave station receiving local oscillator 312: F21 + Δf5 Δf1 ~ Δf5 is a frequency error. For example, the frequency F
1 is 14 GHz, frequency F2 is 12 GHz, master station frequency stability is 1 × 10 ⁻⁸ , repeater frequency stability is 1 × 1
0 ^-5 , and the frequency stability of the slave station is 1 × 10 ^-6 , Δ
f1 is within ± 140 Hz, Δf2 is within ± 120 Hz,
Δf3 is within ± 20 kHz, Δf4 is within ± 14 kHz, and Δf5 is within ± 12 kHz. When the master station 1 transmits the pilot signal A in this state, the frequency of the pilot signal B is expressed by equation (1).

F11 + Δf1 + F2-F1 + Δf3 = F21 + Δf1 + Δf3 (1) When the local oscillator frequency of the receiving local oscillator 312 of the slave station 3 and the frequency of the pilot signal B are compared by the frequency comparator 301, the deviation is given by the equation (2).

Δf1 + Δf3−Δf5 (2) A frequency equal to this deviation is oscillated by the correction frequency oscillator 304, and the transmission local oscillator 31 is oscillated by the frequency converter 315.
Subtract from the oscillation frequency of 3. The output frequency of the frequency converter 315 is given by the equation (3).

F12 + Δf4− (Δf1 + Δf3−Δf5) (3) As a result, the frequency of the signal D becomes a value represented by the equation (4).

F12 + Δf4− (Δf1 + Δf3−Δf5) + F2 + F1 + Δf3 = F22−Δf1 + Δf4 + Δf5 (4) The signal D of this frequency is received by the receiving local oscillator 112 of the master station 1.
The frequency is converted by the frequency converter 103 according to the output of 1 and demodulated by the demodulator 110. The frequency error at the input of demodulator 110 is given by equation (5).

[0012]   F22-Δf1 + Δf4 + Δf5- (F22 + Δf2)   = -Δf1-Δf2 + Δf4 + Δf5 (5)

[0013]

As can be seen from the equation (5), in the conventional technique, the error due to the local oscillator of the repeater is canceled, but the error due to the local oscillators of the master station and the slave station remains. . There is a problem that the reception characteristic is deteriorated by this residual error. The only solution to this problem in the prior art is to improve the frequency stability accuracy of the local oscillator. However, although it is possible to increase the frequency stability accuracy on the master station side with a highly stable device, it is difficult to improve the frequency stability accuracy on the slave station side due to the device scale and cost constraints.

The present invention has been made in view of such a background, and solves the above-mentioned problems, and uses a local oscillator of a communication device having relatively low frequency stability accuracy while achieving high frequency correction accuracy. An object is to provide a communication device that can be realized. An object of the present invention is to provide a communication device capable of suppressing the device cost while realizing high frequency correction accuracy. It is an object of the present invention to provide a communication device capable of reducing the device size while realizing high frequency correction accuracy. It is an object of the present invention to provide a communication device that can realize high frequency correction accuracy without improving a repeater.

[0015]

SUMMARY OF THE INVENTION The present invention is a communication device comprising a master station, a plurality of slave stations communicating with the master station, and a relay for relaying communication between the master station and the slave station. Equipped with
In the communication device, a carrier wave frequency of a signal transmitted from the master station and the slave station to the repeater is F1, and a carrier wave frequency of a signal transmitted from the repeater to the master station and the slave station is F2.

Here, a feature of the present invention is that the master station and the slave station each include one reference frequency signal generator and a PLL circuit for synchronizing with the reference frequency signal for transmission and reception. Each comprising a local oscillator for, the slave station, means for detecting an error between the reception frequency of the pilot signal received from the master station via the repeater and the frequency of the local oscillator for reception, The master station includes means for multiplying the error by a constant F1 / F2, and means for adding the multiplication result of the multiplication means to the transmission frequency, and the master station receives the pilot signal of the own station via the repeater. Means for detecting an error between the reception frequency of the signal and the frequency of the local oscillator for reception, and a constant (F1 + F2) for the error.
It is provided with means for multiplying / F2 and means for correcting and receiving the reception frequency of the signal from the slave station according to the multiplication result of this multiplication means. It is desirable that the means for correcting and receiving should include means for subtracting the multiplication result of the multiplying means from the reception frequency of the signal from the slave station.

The local oscillator in the master station and the local oscillator in each slave station are synchronized by a PLL circuit driven by the same reference frequency signal for each station. Therefore, the oscillation frequencies of the local oscillators of the master station and slave stations are values proportional to the frequencies of the reference frequency signals of the master station and slave stations, respectively, and there is an error in the frequency of the reference frequency signal between the master station and slave stations. In this case, the frequency error of each local oscillator between the master station and the slave station is also proportional to the frequency error of the reference frequency signal. Utilizing this, the slave station side calculates the ratio of the transmission frequency to the reception frequency (F1) to the reception frequency error detected from the pilot signal.
The transmission frequency is corrected by the value obtained by multiplying / F2).
By this operation, the transmission frequency error and the reception frequency error on the slave station side are just canceled, and the transmission frequency from the slave station does not include the frequency error component on the slave station side. However, the error caused by the master station and repeater is not corrected at this stage,
It remains at the transmission frequency of the slave station. Since the master station cancels this at the time of reception, the pilot signal is also simultaneously received by the master station to detect the frequency error. The detection result shows (F1 + F
2) / F2 is multiplied, and when the received signal from the slave station is corrected by this value, all frequency error components are canceled as will be described later by mathematical expressions, and communication that is completely unaffected by the accuracy of the local oscillator becomes possible. Become.

As another configuration, each of the master station and the slave station includes a local oscillator for transmission and a local oscillator for reception, each including one reference frequency signal generator and a PLL circuit synchronized with the reference frequency signal. Each of the slave stations comprises means for detecting an error between the reception frequency of the pilot signal received from the master station via the repeater and the frequency of the local oscillator for reception, and a constant F1 for the error. / F2, and a means for adding the multiplication result of this multiplication means to the transmission frequency, wherein the master station receives the reception frequency of the pilot signal of its own station received via the repeater and A means for detecting an error from the frequency of the local oscillator for reception, a means for controlling the transmission frequency of the pilot signal so that the error becomes zero, and a means for controlling according to the control amount of the controlling means. It may be configured to include a means for receiving and correcting the reception frequency of the signal from the slave station.
It is preferable that the means for correcting and receiving includes a means for adding a frequency corresponding to the control amount from a reception frequency of a signal from the slave station.

This configuration is different in that the master station controls the transmission frequency of the pilot signal in addition to the operation of the slave station similar to the former. In the former case, when the frequency stability accuracy of the local oscillator of the repeater is extremely poor, the transmission frequency of the slave station may largely deviate and deviate from the allowed frequency band.
On the other hand, in the latter, while the pilot signal transmitted by the master station is received by the master station itself, its transmission frequency is controlled so that the reception frequency error becomes zero. By this operation, the pilot signal is not affected by the frequency error in the local oscillator of the repeater and is localized at the frequency determined by the frequency stability accuracy of the local oscillator of the master station. Since the accuracy of the local oscillator of the master station can be made considerably high, the deviation of the transmission frequency of the slave station is suppressed, and the problem that may occur in the former does not occur. Furthermore, since the master station performs frequency correction on the received signal from the slave station by the control amount of the transmission frequency, all frequency error components are canceled as described later by mathematical expressions, and the frequency stability accuracy of the local oscillator is reduced. Communication that is completely unaffected is possible.

As described above, according to the present invention, it is possible to realize a high frequency correction accuracy while using a local oscillator of a communication device having a relatively low frequency stability accuracy. Therefore, the device cost can be kept low while realizing high frequency correction accuracy. Further, it is possible to reduce the size of the device while realizing high frequency correction accuracy. Further, the present invention can achieve high frequency correction accuracy without improving the repeater. For example,
Even when the repeater is a communication satellite or the repeater is geographically remote and difficult to easily improve, the present invention can be used to replace the existing repeater. It can be used to improve frequency correction accuracy.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the essential parts of a communication device according to the first embodiment of the present invention. FIG. 2 is a block diagram of the essential parts of a communication device according to the second embodiment of the present invention.

The first embodiment of the present invention, as shown in FIG.
A master station 1, a plurality of slave stations 3 that communicate with the master station 1, and a relay 2 that relays communication between the master station 1 and the slave station 3,
The carrier wave frequency of the signal transmitted from the master station 1 and the slave station 3 to the relay station 2 is F1, and the carrier wave frequency of the signal transmitted from the relay station 2 to the master station 1 and the slave station 2 is F2.

Here, the feature of the present invention is that the master station 1 and the slave station 3 each have one reference frequency signal generator 1.
06 and 308 and P synchronized with this reference frequency signal
Transmitting and receiving local oscillators 101, 303, and receiving local oscillators 102, 104, 30 including LL circuits
2, the slave station 3 includes a frequency comparator 301 which is a means for detecting an error between the reception frequency of the pilot signal received from the master station 1 via the repeater 2 and the frequency of the reception local oscillator 302. The master station includes a multiplier 307 that is means for multiplying the error by a constant F1 / F2, and a correction frequency oscillator 304 and a frequency converter 305 that are means for adding the multiplication result of the multiplier 307 to the transmission frequency. Reference numeral 1 denotes a frequency comparator 105 which is a means for detecting an error between the reception frequency of the pilot signal of the own station received via the repeater 2 and the frequency of the reception local oscillator 104, and a constant (F1 + F2) / A multiplier 109 which is means for multiplying F2, and a correction frequency which is means for correcting and receiving the reception frequency of the signal from the slave station 3 according to the multiplication result of this multiplier 109. Oscillator 107 and the frequency converter 1
08 and is equipped with. This frequency converter 108
Subtracts the output of the correction frequency oscillator 107 corresponding to the multiplication result of the multiplier 109 from the reception frequency of the signal from the slave station 3.

The second embodiment of the present invention, as shown in FIG.
The slave station 3 is a frequency comparator 301 that is a means for detecting an error between the reception frequency of the pilot signal received from the master station 1 via the repeater 2 and the frequency of the reception local oscillator 302.
A multiplier 307 that is means for multiplying the error by a constant F1 / F2, and a correction frequency oscillator 304 and a frequency converter 305 that are means for adding the multiplication result of the multiplier 307 to the transmission frequency. The station 1 is a means for detecting an error between the reception frequency of the pilot signal of its own station received via the repeater 2 and the frequency of the reception local oscillator 104, and the error is zero. A correction frequency oscillator 117 which is means for controlling the transmission frequency of the pilot signal, and the correction frequency oscillator 11
The frequency converter 108 is a means for correcting the reception frequency of the signal from the slave station 3 in accordance with the control amount of No. 7 and receiving the signal. The frequency converter 108 adds the output frequency of the correction frequency oscillator 117 corresponding to the control amount from the reception frequency of the signal from the slave station 3.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first and second embodiments of the present invention, satellite communication will be described as an example, but the scope of application of the present invention is not limited to this. For example, the repeater 2 can be installed on the ground. In this case, a wired line may be provided between the master station 1 and the repeater 2, and between the repeater 2 and the slave station 3 instead of a wireless line.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIG. In FIG. 1, the frequency of the upstream signal transmitted from the master station 1 and the slave station 3 to the repeater 2 is F1 (for example, 14
(GHz) band. The frequency of the downlink signal transmitted from the repeater 2 to the master station 1 and the slave station 3 is F2 (for example, 12 GH).
z) Belt. The pilot signal transmitted from the master station 1 to the slave station 3 has an upstream signal frequency of F11 (F11 is near F1) and a downstream signal frequency of F21 (F21 = F11 + F2).
-F1), the upstream signal frequency of the signal transmitted from the slave station 3 to the master station 1 is F12 (F12 is near F1), and the downstream signal frequency is F22 (F22 = F12 + F2-F1).

In FIG. 1, the transmission local oscillator 1 of the master station 1
01 and the receiving local oscillators 102 and 104 are PLLs synchronized with the signal from the same reference frequency signal generator 106.
It constitutes the circuit. In addition, the transmitter local oscillator 30 of the slave station 3
3 and the receiving local oscillator 302 also constitute a PLL circuit synchronized with the signal from the same reference frequency signal generator 308.

First, the master station 1 oscillates the transmission local oscillator 101 at the frequency F11 and transmits it as the pilot signal A to the repeater 2. The repeater 2 includes a local oscillator 20.
1 and frequency converter 202 frequency-converts pilot signal A and transmits again to slave station 3 and master station 1 (pilot signal B).

Next, the slave station 3 receives the pilot signal B, compares the reception frequency of the pilot signal B and the local oscillation frequency of the reception local oscillator 302 with the frequency comparator 301 to obtain the deviation, and the multiplier 307. Therefore, the frequency obtained by multiplying this deviation by F1 / F2 is corrected frequency oscillator 304
To oscillate. The output of the corrected frequency oscillator 304 is input to the frequency converter 305, and the output signal of the transmission local oscillator 303 is frequency-converted to the frequency addition side. The frequency-converted signal is modulated by the modulator 306 and transmitted to the repeater 2 (signal C).

The pilot signal B is also received by the master station 1,
The reception frequency of this pilot signal B and the reception local oscillator 1
The frequency is compared with the local oscillation frequency of No. 02 by the frequency comparator 105 to obtain the deviation. The frequency obtained by multiplying this deviation by (F1 + F2) / F2 by the multiplier 109 is oscillated by the correction frequency oscillator 107.

On the other hand, the signal C is frequency-converted by the repeater 2 into the signal D, which is frequency-converted by the receiving local oscillator 102 and the frequency converter 103 of the master station 1. Further, the output of the corrected frequency oscillator 107 is frequency-converted by the frequency converter 108 and demodulated by the demodulator 110.

The above operation will be described by using mathematical expressions. The local oscillation frequency of each local oscillator before frequency synchronization is set as follows.

Master station transmitting local oscillator 101: F11 + Δg1 Master station receiving local oscillator 102: F22 + Δg2 Repeater local oscillator 201: F2-F1 + Δg3 Slave station transmitting local oscillator 303: F12 + Δg4 Slave station receiving local oscillator 302: F21 + Δg5 Parent Station reception local oscillator 104: F21 + Δg6 Δg1 to Δg6 are frequency errors. For example, the frequency F
1 is 14 GHz, frequency F2 is 12 GHz, master station frequency stability is 1 × 10 ⁻⁸ , repeater frequency stability is 1 × 1
0 ^-5 , and the frequency stability of the slave station is 1 × 10 ^-6 , Δ
g1 is within ± 140Hz, Δg2 and Δg6 are ± 120H
Within z, Δg3 within ± 20 kHz, Δg4 within ± 14 k
Within Hz, Δg5 is within ± 12 kHz. However,
Since the frequency error of the local oscillator in a synchronous relationship due to the PLL circuit is in a proportional relationship, equations (6) and (7) hold.

Δg1 / F11 = Δg2 / F22 = Δg6 / F21 ≈Δg1 / F1 = Δg2 / F2 = Δg6 / F2 (6) Δg4 / F12 = Δg5 / F21 ≈Δg4 / F1 = Δg5 / F2 (7) In this state When the master station 1 transmits the pilot signal A,
The frequency of pilot signal B is expressed by equation (8).

F11 + Δg1 + F2-F1 + Δg3 = F21 + Δg1 + Δg3 (8) When the oscillating frequency of the receiving local oscillator 302 of the slave station 3 and the frequency of the pilot signal B are compared, the deviation is expressed by the equation (9).

Δg1 + Δg3-Δg5 (9) The frequency that is F1 / F2 times this deviation is corrected by the frequency oscillator 3
04, and the frequency converter 305 adds it to the oscillation frequency of the transmission local oscillator 303. Frequency converter 30
The output frequency of 5 is given by equation (10).

F12 + Δg4 + (Δg1 + Δg3-Δg5) F1 / F2 = F12 + (Δg1 + Δg3) F1 / F2 (10) As a result, the frequency of the signal D becomes a value represented by the equation (11).

F12 + (Δg1 + Δg3) F1 / F2 + F2-F1 + Δg3 = F22 + Δg1 · F1 / F2 + Δg3 (F1 + F2) / F2 (11) On the other hand, the pilot signal B is compared with the output of the receiving local oscillator 104 in the master station 1 to obtain the deviation. To be The deviation is expressed by equation (12).

[Delta] g1 + [Delta] g3- [Delta] g6 = [Delta] g1 (F1 + F2) / F1 + [Delta] g3 (12) The correction frequency oscillator 107 generates a frequency that is (F1 + F2) / F2 times this deviation. The output frequency of the correction frequency oscillator 107 is given by equation (13). Δg1 (F1−F2) (F1 + F2) / (F1 · F2) + Δg3 (F1 + F2) / F2 (13) Next, when the frequency of the signal D is converted by the frequency converter 103 by the output of the reception local oscillator 102 of the master station 1, The error is given by equation (14). F22 + Δg1 · F1 / F2 + Δg3 (F1 + F2) / F2- (F22 + Δg2) = Δg1 (F1 / F2-F2 / F1) + Δg3 (F1 + F2) / F2 (14) Since the formula (13) and the formula (14) are equal, the correction frequency oscillator When the output of the frequency converter 103 is frequency-converted and demodulated by the frequency converter 107 and the frequency converter 108, all the errors due to the local oscillators are canceled and the frequency error at the input of the demodulator 110 becomes zero.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. Similar to the first embodiment of the present invention, the frequency of the upstream signal transmitted from the master station 1 and the slave station 3 shown in FIG. 2 to the repeater 2 is the F1 (for example, 14 GHz) band. The frequency of the downlink signal transmitted from the repeater 2 to the master station 1 and the slave station 3 is the F2 (12 GHz) band. The uplink signal frequency of the pilot signal transmitted from the master station 1 to the slave station 3 is F11 (F11 is near F1), and the downlink signal frequency is F21.
(F21 = F11 + F2-F1), the upstream signal frequency of the signal transmitted from the slave station 3 to the master station 1 is F12 (F12
Is near F1), and the downlink signal frequency is F22 (F22 = F1
2 + F2-F1).

In FIG. 2, the transmission local oscillator 1 of the master station 1
01 and the receiving local oscillators 102 and 104 are PLLs synchronized with the signal from the same reference frequency signal generator 106.
It constitutes the circuit. In addition, the transmitter local oscillator 30 of the slave station 3
3 and the receiving local oscillator 302 also constitute a PLL circuit synchronized with the signal from the same reference frequency signal generator 308.

First, the master station 1 causes the transmitting local oscillator 101 to oscillate at the local oscillation frequency F11, and the pilot signal A
Is transmitted to the repeater 2. The repeater 2 frequency-converts the pilot signal A by the local oscillator 201 and the frequency converter 202, and transmits again to the slave station 3 and the master station 1 (pilot signal B).

The pilot signal B is first received by the master station 1, and the deviation is obtained by comparing the reception frequency of the pilot signal B and the local oscillation frequency of the reception local oscillator 104 by the frequency comparator 105. The oscillation frequency of the correction frequency oscillator 117 is controlled so that this deviation becomes zero, and the local oscillation frequency of the transmission local oscillator 101 is changed to the frequency converter 11.
The frequency is converted by 1 to determine the transmission frequency.

Next, the slave station 3 receives the pilot signal B, compares the reception frequency of this pilot signal with the local oscillation frequency of the reception local oscillator 302 by the frequency comparator 301 to obtain the deviation, and the multiplier 307. F to this deviation
The frequency multiplied by 1 / F2 is oscillated by the correction frequency oscillator 304. The output of the correction frequency oscillator 304 is input to the frequency converter 305, and the local oscillation frequency signal output from the transmission local oscillator 303 is frequency-converted to the frequency addition side. The frequency-converted signal is modulated by the modulator 306 and transmitted to the repeater 2 (signal C).

The signal C is frequency-converted by the repeater 2 into a signal D, which is frequency-converted by the receiving local oscillator 102 and the frequency converter 103 of the master station 1. Further, the frequency converter 10 is controlled by the output of the correction frequency oscillator 117.
The frequency is converted by 8 and demodulated by the demodulator 110.

The above operation will be described by a mathematical expression. The local oscillation frequency of each local oscillator before frequency synchronization is set as follows.

Master station transmitting local oscillator 101: F11 + Δh1 Master station receiving local oscillator 102: F22 + Δh2 Repeater local oscillator 201: F2-F1 + Δh3 Slave station transmitting local oscillator 303: F12 + Δh4 Slave station receiving local oscillator 302: F21 + Δh5 Parent Station local oscillator 104: F21 + Δh6 Δh1 to Δh6 are frequency errors. For example, the frequency F
1 is 14 GHz, frequency F2 is 12 GHz, master station frequency stability is 1 × 10 ⁻⁸ , repeater frequency stability is 1 × 1
0 ^-5 , and the frequency stability of the slave station is 1 × 10 ^-6 , Δ
h1 is within ± 140Hz, Δh2 and Δh6 are ± 120H
Within z, Δh3 within ± 20 kHz, Δh4 within ± 14 k
Within Hz, Δh5 is within ± 12 kHz. However,
Since the frequency error of the local oscillator which is in a synchronous relationship by the PLL circuit is in a proportional relationship, the equations (15) and (16) are established.

Δh1 / F11 = Δh2 / F22 = Δh6 / F21 ≈Δh1 / F1 = Δh2 / F2 = Δh6 / F2 (15) Δh4 / F12 = Δh5 / F21 ≈Δh4 / F1 = Δh5 / F2 (16) In this state When the master station 1 transmits the pilot signal A,
The frequency of pilot signal B is expressed by equation (17). At this time, the output frequency of the correction frequency oscillator 117 is set to zero.

F11 + Δh1 + F2-F1 + Δh3 = F21 + Δh1 + Δh3 (17) The pilot signal B is received by the master station 1 at the receiving local oscillator 10
The deviation is obtained by comparing the output of FIG. The deviation is expressed by equation (18).

Δh1 + Δh3−Δh6 = Δh1 (F1−F2) / F1 + Δh3 (18) The frequency of the correction frequency oscillator 117 is set so as to cancel this deviation. Therefore, the output frequency of the correction frequency oscillator 117 is equal to the value obtained by inverting the expression (18).
This is shown in equation (19).

-Δh1 (F1-F2) / F1-Δh3 (19) After the frequency of the correction frequency oscillator 117 is set, the frequency of the pilot signal B is expressed by the equation (20).

F11 + Δh1-Δh1 (F1-F2) / F1-Δh3 + F2-F1 + Δh3 = F21 + Δh1 · F2 / F1 (20) Next, comparing the oscillation frequency of the reception local oscillator 302 of the slave station 3 with the frequency of the pilot signal B, The deviation is expressed by equation (21).

Δh1 · F2 / F1−Δh5 (21) The frequency that is F1 / F2 times the deviation is corrected frequency oscillator 3
04, and the frequency converter 305 adds it to the oscillation frequency of the transmission local oscillator 303. Frequency converter 30
The output frequency of 5 is given by equation (22).

F12 + Δh4 + (Δh1 · F2 / F1-Δh5) F1 / F2 = F12 + Δh1 (22) As a result, the frequency of the signal D becomes a value represented by the equation (23).

F12 + Δh1 + F2-F1 + Δh3 = F22 + Δh1 + Δh3 (23) Next, when the frequency of the signal D is converted by the frequency converter 103 by the output of the receiving local oscillator 102 of the master station 1, the frequency error is given by the formula (24).

F22 + Δh1 + Δh3− (F22 + Δh2) = Δh1 (F1−F2) / F1 + Δh3 (24) The expressions (24) and (19) have a positive / negative inversion relationship. Therefore, if the output of the frequency converter 103 is frequency-converted by the output frequency of the correction frequency oscillator 117 and demodulated, all the errors due to the local oscillators are canceled out, and the frequency error at the input of the demodulator 110 becomes zero.

As described above, the second embodiment of the present invention is different from the first embodiment of the present invention in that the slave station 3 operates and the master station 1 controls the transmission frequency of the pilot signal. In the first embodiment of the present invention, when the frequency stability accuracy of the local oscillator 201 of the repeater 2 is extremely poor, the transmission frequency of the slave station 3 may largely shift and deviate from the permitted frequency band. On the other hand, in the second embodiment of the present invention, the transmission frequency is controlled while receiving the pilot signal transmitted by the master station 1 by the master station itself so that the reception frequency error becomes zero. By this operation, the pilot signal is not affected by the frequency error in the local oscillator 201 of the repeater 2,
It is localized at the frequency determined by the frequency stability accuracy of the transmission local oscillator 101 of the master station 1. Transmitting local oscillator 10 of master station 1
Since the accuracy of 1 can be considerably increased, deviation of the transmission frequency of the slave station 3 is suppressed, and the problem that may occur in the first embodiment of the present invention does not occur. Furthermore, in the master station 1,
Since the frequency of the received signal from the slave station 3 is corrected by the control amount of the transmission frequency, all the frequency error components are canceled out, and the communication that is completely unaffected by the frequency stability accuracy of each local oscillator becomes possible.

Further, in the embodiment of the present invention, the pilot signal is a non-modulated signal, but it may be a modulated signal modulated by control information transmitted from the master station 1 to the slave station 3, for example.

[0059]

As described above, according to the present invention,
It is possible to achieve high frequency correction accuracy while using a local oscillator of the communication device having relatively low frequency stability accuracy. Therefore, the device cost can be kept low while realizing high frequency correction accuracy. Further, it is possible to reduce the size of the device while realizing high frequency correction accuracy. Further, the present invention can achieve high frequency correction accuracy without improving the repeater.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a communication device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a communication device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a main part of a conventional communication device.

[Explanation of symbols]

1 master station 2 repeater 3 slave station 100, 200, 300 antenna 103, 108, 111, 202, 305, 315 frequency converter 110 demodulator 101, 121, 303, 313 transmission local oscillator 102, 104, 112, 302, 312 Reception local oscillator 106, 308 Reference frequency signal generator 107, 117, 304 Correction frequency oscillator 109, 307 Multiplier 201 Local oscillator 105, 301 Frequency comparator 306 Modulator

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A 64-17521 (JP, A) JP-A 6-276244 (JP, A) JP-A 9-233014 (JP, A) JP-A 54- 107207 (JP, A) JP 7-99470 (JP, A) JP 54-31216 (JP, A) JP 4-57416 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B ^7/ 14-7/22

Claims (4)

(57) [Claims] 1. A master station, a plurality of slave stations communicating with the master station, and a relay device for relaying communication between the master station and the slave station, the master station and the slave station In the communication device, the carrier frequency of the signal transmitted to the relay is F1, and the carrier frequency of the signal transmitted from the relay to the master station and the slave station is F2, wherein the master station and the slave station are: Each one reference frequency signal generator and PLL (Phase L
ocked Loop) circuit and a local oscillator for reception, respectively, including, the slave station, the reception frequency of the pilot signal from the master station received via the repeater and the local oscillator for reception. And a means for multiplying the error by a constant F1 / F2, and a means for adding the multiplication result of the multiplying means to the transmission frequency, the master station being the relay station. Means for detecting an error between the reception frequency of the pilot signal of its own station received via the terminal and the frequency of the local oscillator for reception, and a constant (F1
A communication device comprising: means for multiplying + F2) / F2; and means for correcting and receiving the reception frequency of the signal from the slave station according to the multiplication result of this multiplication means. 2. The communication device according to claim 1, wherein the means for correcting and receiving includes means for subtracting a multiplication result of the multiplying means from a reception frequency of a signal from the slave station. 3. A master station, a plurality of slave stations communicating with the master station, and a relay device for relaying communication between the master station and the slave station, the master station and the slave station In the communication device, the frequency of the signal transmitted to the repeater is F1, and the frequency of the signal transmitted from the repeater to the master station and the slave station is F2, wherein each of the master station and the slave station is one. Each of which is provided with a local oscillator for transmission and reception which includes a reference frequency signal generator and a PLL circuit which is synchronized with the reference frequency signal, wherein the slave station is from the master station received via the repeater. Means for detecting an error between the reception frequency of the pilot signal and the frequency of the local oscillator for reception, a means for multiplying the error by a constant F1 / F2, and the multiplication result of this multiplication means is added to the transmission frequency. And means, The master station is a means for detecting an error between the reception frequency of the pilot signal of the own station received via the repeater and the frequency of the local oscillator for reception, and the pilot signal so that the error becomes zero. And a means for correcting the reception frequency of the signal from the slave station in accordance with the control amount of the control means and receiving the signal. 4. The communication device according to claim 3, wherein the means for correcting and receiving includes a means for adding a frequency corresponding to the control amount from a reception frequency of a signal from the slave station.