JPH0581093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a relay device used in a digital satellite communication system, and particularly to a relay device effective in a multi-beam satellite communication system that switches and relays a plurality of burst signals. It is something.

(Prior art and its problems) Figure 1 shows that the receiving frequencies are f, f+Δf, f+2Δf,
Four receivers with f+3Δf and a transmitting frequency of F,
This figure shows the configuration of a conventional satellite repeater that switches and connects four transmitters F+Δf, F+2Δf, and F+3Δf in a time-division manner using the same intermediate frequency f _1F . In the figure, 1-
1 to 14 are signal input terminals, 2-1 to 2-4 are the first
mixer, 3-1 to 3-4 are local oscillators, 4-1 to 3-4;
4-4 is a receiving section, 5 is a switching circuit that switches and connects the input signal in a time division manner at intermediate frequency _f1F , 6-1 to 6-
4 is a transmitter that converts the intermediate frequency f _1F into a transmission frequency, and 7-1 to 7-4 are signal output terminals. As shown in FIG. 1, conventional local oscillators were individually provided in each receiving section. Therefore, burst-like TDMA (Time Division Multiple Access) is transmitted from signal input terminals 1-1 to 1-4.
When a signal is input, each local oscillator 3-
After receiving frequency fluctuations from 1 to 3-4, the switching circuit 5
The transmission units 6-1 to 6-4 are rearranged in a time division manner.
It will be converted to the transmission frequency and output. Therefore, in order to demodulate using the conventional receiving station apparatus, the frequency stability of the local oscillators 3-1 to 3-4 must be extremely high.

FIG. 2 shows an example of the configuration of a relay device that solves the above-mentioned drawbacks (Japanese Patent Application No. 196770/1982). 8-1 to 8-4
are second mixers provided in each receiving section, 9-1 to 9-1;
9-4 is an oscillator that supplies an oscillation signal to the second mixer; 10 is an oscillator that generates a signal with a frequency close to the frequency of the local oscillation signal to the first mixer; A common oscillator that supplies
The oscillation frequencies of the oscillators 9-1 to 9-4 are f _L1 to f _L4 ,
Assuming that the oscillation frequency f _L of the oscillator 10 is f _L ≫ f _L1 , f _L2 , f _L3 , f _L4 , the frequency fluctuation of the local oscillation signal is approximately determined by the frequency stability of the common oscillator 10. It's decided. here. Since the output of the common oscillator 10 is commonly supplied to each receiving section, it is possible to reduce variations in frequency fluctuations between intermediate frequency signals output from each receiving section. However, in the conventional example shown in FIG. 2, it is necessary to set the output frequency of the common oscillator 10 close to the local oscillator input frequency, and when the local oscillator input frequency reaches about 300 GHz band, the common oscillator output terminal is connected to the common oscillator output terminal by the waveguide. It is necessary to connect the input terminals of each receiver, which imposes restrictions on the conditions for arranging the receivers on the satellite platform, and the use of waveguides has the drawback of significantly increasing weight.

FIG. 3 is a diagram showing another conventional example that solves the above drawbacks. 1-1, 1-2...8-4 are the same as in FIG. 2, 11 is a first common oscillator whose oscillation frequency is Δf (several GHz or less), and 12-1 to 12-
4 has multipliers of n, n+1, n+2, and n+, respectively.
3 (n: natural number) multiplier (including a phase synchronized oscillator), 13 is a second common oscillator for commonly giving a constant frequency deviation to the second mixers 8-1 to 8-4. . The oscillation frequency Δ of the second common oscillator is in the frequency band of several GHz, and is set so as to satisfy the relationship f _1F = f−nΔf−Δ .
In the figure, first and second common oscillators 11,1
Since the oscillation frequency of 3 is several GHz or less, the oscillation signal is transmitted to each receiving section 4-1 to 4-4 with low loss using a coaxial cable, which is lighter and easier to handle than a waveguide.
Input signals having frequencies f, f+∆f, f+2∆f, and f+3∆f, respectively, which can be supplied to the following equations, are all converted into intermediate frequency signals of the same frequency f _1F according to the relationship of the formula. For example, in the case of the receiving section 4-4,
The signal from the first common oscillator 11 is multiplied by (n+3) times, and mixed with the signal from the second common oscillator 13 in the second mixer 8-4 (n+3)Δf
The local signal with a frequency of +Δ is sent to the first mixer 2-4.
supplied to Since the input frequency is f+3∆f, the output signal frequency _f4 of the receiver 4-4 is _f4 = (f+3∆f) - [(n+3)∆f+∆] = f - n∆f - ∆= f _1F (from the formula), and the intermediate frequency f Converted to _1F .

In this case, since the same frequency Δ is supplied from the second common oscillator 13 to the plurality of second mixers 8-1 to 8-4, the frequency error of the second common oscillator 13 is Commonly appears at the input ends of mixers 8-1 to 8-4. On the other hand, the signal from the first common oscillator 11 is transmitted to a multiplier 1 of a different multiplication order.
2-1, 12-2, 12-3, 12-4 to each of the second mixers 8-1 to 8-4, local oscillation to the first mixers 2-1 to 2-4 occurs. The signals will have frequency errors with respect to each other. However, the first
Since the oscillation frequency of the common oscillator 11 is set low, the error is small. For example, f=30G
Hz, Δf=200MHz, f _1F =1.7GHz, Δ=2.3GHz, then n=130. Now, assuming that the frequency stability of the first common oscillator 11 is 1×10 ^-5 , the frequency error that appears between the outputs of multipliers that differ by one step in multiplication order is 2 kHz as a deviation, and this error also applies to the intermediate frequency signal. appear. On the other hand, in the case of the configuration shown in FIG. 1, an error of 28.3 GHz×1×10 ⁻⁵ =283 Hz occurs. Therefore, with this configuration, the error in carrier frequency can be reduced to about 1/140.

However, the conventional examples shown in Figs. 2 and 3 both require multiple oscillators, making it impossible to reduce the size and weight of the entire repeater, and having the disadvantage that there is a limit to how high reliability can be achieved. be.

(Objective of the Invention) An object of the present invention is to provide a relay device that is smaller and lighter by using a single oscillator and that is also highly reliable.

(Structure of the Invention) In order to achieve this object, the relay device of the present invention uses a switching circuit to receive a plurality of input signals separated from each other by an integer multiple of a certain frequency Δf and receive outputs from a plurality of receivers. In the relay device that switches and transmits signals from a plurality of transmitters, each of the plurality of receivers includes a plurality of first mixers each receiving the plurality of input signals as an input signal, and a first mixer that oscillates at the constant frequency Δf. a common oscillator, a plurality of multipliers each of which multiplies the output of the first common oscillator by a corresponding multiplier, and a plurality of multipliers each of which multiplies and divides the output of the first common oscillator by a corresponding multiplication division ratio. a multiplier frequency divider, and a mixed output obtained by mixing the outputs of the plurality of multipliers and the outputs of the plurality of multiplier frequency dividers for each receiving section, respectively, to the plurality of first mixers for local oscillation. and a plurality of second mixers for outputting intermediate frequency outputs in the same intermediate frequency band from the plurality of receiving sections.

FIG. 4 shows an embodiment of the present invention in which the output signal of the second common oscillator in the configuration shown in FIG. 3 is created using the output signal of the first common oscillator, and the number of common oscillators is reduced to one. It is. 1-1 to 12-
Up to 4 are the same as in Figure 3, and 14-1 to 14-
4 is a multiplier/divider, and the multiplication order N and the frequency division order M are selected so that Δ and Δf in FIG. 3 satisfy the following relationship: Δ=(N×Δf)÷M. By adopting the configuration shown in FIG. 4, the number of common oscillators can be reduced to one, thereby making it possible to improve the reliability of the entire relay device. The effect regarding the frequency error is the same as the configuration example shown in FIG.

According to the above embodiment, it is possible to sufficiently reduce the variation in the intermediate frequency, and the burst signal converted to the intermediate frequency is rearranged in a time division manner by the switching circuit 5, and then sent to the transmitting units 6-1 to 6-6. Sent via . Even in the rearranged transmission signal, the variation in carrier frequency for each burst signal is sufficiently small, so when the receiving station equipment demodulates the burst signal, the demodulator can sufficiently follow the received signal. This is extremely useful for SS/TDMA communication.

In the above embodiment, the case where there are four transmitting/receiving units has been described, but of course there may be any number of these units. Further, as the multipliers 12-1 to 12-4 in the figure, a phase synchronized oscillation circuit configured by combining a voltage controlled oscillator, a sampling phase comparator, etc. may be used. In this case, since the order of multiplication can be selected for selecting the phase comparison signal, most of the multiplier circuits in each receiving section can be shared, and the size and power consumption can be reduced compared to conventional multipliers. .

(Effects of the Invention) As described above, according to the present invention, the number of oscillators can be reduced, so that the weight of the entire relay device can be reduced and the reliability of the relay device can be increased.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional relay device using the SS-TDMA method, Figures 2 and 3 are configuration diagrams of a conventional relay device with a common receiving local oscillator, and Figure 4
The figure is a configuration diagram showing an embodiment of the present invention. 1-1~1-4...Signal input terminal, 2-1~2
-4...First mixer, 3-1 to 3 to 4...Local oscillator, 4-1 to 4-4...Receiving section, 5...Switching circuit, 6-1 to 6-4...Transmitting section , 7-1 to 7-4
... Signal output terminal, 8-1 to 8-4 ... Second mixer, 9-1 to 9-4 ... Oscillator, 10 ... Common oscillator, 11 ... First common oscillator, 12-1 ... 1
2-4... Multiplier, 13... Second common oscillator,
14-1 to 14-4...multiplier/divider.

Claims (1)

[Claims] 1. In a relay device in which a plurality of input signals separated from each other by an integer multiple of a certain frequency Δf are respectively received by a plurality of receivers, reception outputs are switched by a switching circuit and sent out by a plurality of transmitters, respectively. is a plurality of first mixers each receiving the plurality of input signals as input signals, a first common oscillator that oscillates at the constant frequency Δf, and multiplying the output of the first common oscillator by a corresponding multiplier. a plurality of frequency dividers that respectively multiply the output of the first common oscillator by a corresponding frequency division ratio; and a plurality of frequency dividers that multiply the output of the first common oscillator by a corresponding frequency division ratio; The mixed output obtained by mixing the outputs of the frequency dividers for each receiving section is supplied to each of the plurality of first mixers as a local oscillation wave, and the intermediate frequency of the same intermediate frequency band is output from the plurality of receiving sections. A relay device comprising a plurality of second mixers for outputting an output.