JPH047612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a repeater used in a digital satellite communication system, and particularly to multi-beam satellite communication in which burst signals of multiple carrier waves are switched, reorganized, and relayed and amplified. It relates to a relay device that is effective for the system.

(Prior art) Conventionally, satellite communication systems use FDM-FM-
The FDM method has been used most often. but,
In order to cope with the increase in the number of earth stations participating in the system and the increase in communication demand, consideration has been given to introducing a digital satellite communication method that has higher efficiency, larger capacity, and can flexibly follow traffic fluctuations. . One of them is multi-beam satellites.
In combination with TDMA technology, a system called SS/TDMA has been put into practical use, in which a dynamic switch is mounted inside the satellite and beam connections are switched at high speed in synchronization with the TDMA frame.

In recent years, in order to cope with the further increase in communication demand,
The use of multi-beam satellite tower repeaters that use higher frequency sub-millimeter wave frequencies as carrier waves is being considered. FIG. 1 shows an example of the configuration of an SS/TDMA repeater using a quasi-millimeter wave band carrier wave. In FIG. 1, reference numerals 1 to 4 are receiving beam elements, and frequencies f ₁ ,
f ₂ ,... _fo are assigned. 5 to 7 are receivers assigned to each receiving beam, 8 to 10 are independent local oscillators arranged in each receiver, 11 is a switching circuit for switching the burst signal on the carrier wave, and 12 to 14 are switching circuits. a transmitting unit for converting the output of the circuit 11 into a required frequency band and transmitting it; 1;
5 to 18 are transmitting beam elements.

The plurality of receivers 1 to 4 receive signals of different frequencies f ₁ , _{f 2} , .
It is necessary that the input frequencies of both are common. In order to obtain a common intermediate frequency with the configuration shown in Figure 1,
Local oscillators 8~ inside the plurality of receivers mentioned above
It is necessary to set the 10 oscillation frequencies to the difference or sum of the receiving frequency and the intermediate frequency. In addition, local oscillators 8 to 10 having different oscillation frequencies within the plurality of receiving sections have different frequency initial setting errors and frequency temperature changes. As a result, the intermediate frequencies obtained by mixing with the received signal have substantially the same frequency, but the frequency dispersion among the intermediate frequencies becomes considerably large.

For example, if the receive input frequency of multiple receivers is
30.0GHz, 30.2GHz, 30.4GHz, ..., and the oscillation frequencies of local oscillators 8 to 10 inside each receiving section are 28.0GHz, 28.2GHz, 28.4GHz, ..., the intermediate frequency of each is 2.0GHz. become. At this time, in each local oscillator 8 to 10, the maximum deviation of the frequency initial setting error is +2×
10 ^-6 , and if there is a local oscillator with a minimum deviation of -2 x 10 ^-6 , and the frequency deviation is about 6 x 10 ^-6 between the oscillator with the maximum frequency temperature change and the oscillator with the minimum frequency temperature change, then the intermediate frequency is approximately 2.0GHz, but the frequency variation at each intermediate frequency is approximately
It can reach up to 280KHz.

As mentioned above, when a burst signal is applied to the switching circuit with large variations in each intermediate frequency, the burst signals of each communication path are switched and reorganized within the switching circuit, and then the desired frequency band is applied. In reorganization where the signals are converted and transmitted, the carrier frequency changes significantly for each burst signal. A receiving station that receives the carrier wave burst signal as described above demodulates the carrier wave burst signal. In this case, since the carrier frequency changes greatly for each burst signal, the operation of the demodulator cannot follow the above changes, resulting in a disadvantage that communication becomes impossible.

(Object of the Invention) An object of the present invention is to provide a first type of mixer and a second type of mixer in each of a plurality of receiving sections corresponding to a plurality of receiving frequencies, and to provide a plurality of second type mixers. A second type of mixer mixes the signals obtained by multiplying the signals from an oscillator that is common to the mixer and is close to the first local oscillation frequency, and an oscillator with a certain constant frequency. convert it into a first local oscillation frequency, and convert this and a plurality of reception frequencies into a first local oscillation frequency.
To provide a relay device configured to eliminate the above-mentioned drawbacks by mixing the intermediate frequencies with a mixer of the above type and converting them to the same intermediate frequency, thereby reducing the frequency error between the respective intermediate frequencies. be.

(Structure of the Invention) In order to achieve the above object, the relay device according to the present invention corresponds to a plurality of reception frequencies,
a plurality of receiving sections each having a first mixer into which each of the received frequencies is input and a second mixer connected to a local signal input terminal of the first mixer; a switching circuit for rearranging the converted signal into a plurality of specified signals; a transmitting means for converting the rearranged signal into a signal of a desired frequency band and transmitting the signal; and each of the above-mentioned signals. A first oscillator for commonly providing a local signal to the second mixer, and a second oscillator for generating a common reference frequency signal.
and a plurality of multipliers for multiplying the frequency of the second oscillator with different multiplication orders corresponding to the plurality of second mixers, and the frequency of the first oscillator is increased. The local signal frequency of the first mixer is set close to that of the first mixer, and the difference between the local signal frequency of each of the first mixers and the frequency of the first oscillator is made an integral multiple of the frequency of the second oscillator serving as the reference. and the respective frequencies obtained by multiplying the output frequency from the second oscillator by different multiplication orders and the frequency of the first oscillator are multiplied by the second oscillator.
to each of the mixers to perform frequency conversion,
A local signal is provided corresponding to each of the plurality of first mixers, and the plurality of reception frequencies are converted into intermediate frequencies of the same frequency using the local signals.

(Example) Next, a relay device according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of an SS/TDMA repeater using a quasi-millimeter wave band carrier wave according to the present invention. In Figure 2, 19
- 22 are receiving beam elements, to which frequencies f _{1 ,} f ₂ , . 2
3 to 25 are receivers assigned to each receiving beam, 26 to 28 are the first type of mixer inside the receiver, and 29 to 31 are connected to the local input terminals of the first type of mixer. a second type of mixer, 32 a first oscillator for commonly supplying a signal of frequency f _LO to a plurality of second type mixers; 33 a frequency
a second oscillator of f _SLO ; 34-36 are multipliers with different multiplier orders for multiplying the oscillation frequency of the oscillator of frequency f _SLO ; 37 is a switching circuit for switching and reorganizing burst signals on a carrier wave; 38-36; 40 is a transmitter having a function of converting a signal into a required frequency band and transmitting the signal, and 41 to 44 are transmitting beam elements.

The frequencies received by the plurality of receivers 23 to 25 are as follows:
Different frequencies f ₁ , f ₂ , ...f _o are assigned so that the frequencies on the transmitting station side do not combine, but normally,
In this frequency assignment, the frequency intervals are often equal intervals or are integral multiples of a certain frequency.

Each station on the transmitting side using the SS/TDMA communication system uses a highly stable and highly accurate signal source such as an atomic oscillator such as a cesium frequency standard or a crystal oscillator with a thermostatic oven as a reference signal source. It transmits signals with frequencies f ₁ , f ₂ , ...f _o . Therefore, errors in the received input frequencies f ₁ , f ₂ , ... _fo at the input terminals of the receiving sections 23 to 25 are caused by only frequency setting errors on the transmitting station side and extremely small frequency changes due to the Dotsubler effect. , the variation in the frequency interval between each frequency is extremely small. The signals of frequencies f ₁ , f ₂ , ... f _o received by the plurality of receivers 23 to 25 are mixed with the local oscillation frequencies of frequencies f _LO1 , f _LO2 , ... f _LOo , and are mixed with the local oscillation frequencies of frequencies f _LO1 , f LO2 , ... converted to frequency.

At this time, first type mixers 26 to 2 for frequency conversion are provided inside each of the plurality of receiving units 23 to 25.
8 and second type mixers 29-31 connected to the local input terminals of the first type mixers 26-28, and the second type mixers 29-31 are provided with a first type mixer 29-31 connected to the local input terminals of the first type mixers 26-28.
The signal from the first oscillator 32 is common to the plurality of second type mixers 29 to 31. , whose frequency is set close to the local input frequency of the first type of mixers 26-28. Further, the output frequencies of the multipliers 34 to 36 corresponding to the plurality of second type mixers 29 to 31 are the local input frequency of the first type mixers 26 to 28 and the output frequency of the first oscillator 32. The setting is such that this frequency is obtained by multiplying the shared output frequency of the second oscillator 33 having the frequency f _SLO by an integer.

Since the first oscillator 32 is common to the plurality of second type mixers 29 to 31, the frequency initial setting error and the frequency error due to frequency temperature change of the first oscillator 32 are respectively caused by the second type of mixers 29 to 31. Commonly appears at the inputs of mixers 29-31 of the type.

Next, a plurality of second type mixers 29 to 31 use the common signal from the first oscillator 32 and the frequency f _SLO
and the signals obtained by multiplying the signals of the second oscillator 33, respectively, and convert them into first local oscillation frequencies f _LO1 , f _LO2 , . . . f _LOo . The frequency error with respect to the first local oscillation frequency of each specified value is the sum of the frequency error of the first oscillator 32 and the frequency error of the signal obtained by multiplying the output signal of the second oscillator 33 with frequency f _SLO . It is becoming. However, since the first oscillator 32 commonly supplies signals to the plurality of second type mixers 29 to 31, the frequency error is canceled out and the first local oscillation frequencies f _LO1 , f _LO2 , . . . The frequency error in each frequency interval in f _LOo is mainly caused by multiplying the second oscillator 33 of frequency f _SLO .

FIG. 3 is a block diagram showing connections between a second oscillator 33 having a frequency f _SLO and a plurality of multipliers 34-36. 33-36 are symbols representing the same elements as shown in FIG. 2, while 45-48 are output terminals of a plurality of multipliers 34-36. In other words, the output of the second oscillator 33 with frequency f _SLO is multiplied by 1,
Multiplication, 3 multiplication... The output signal is obtained by multiplying by n, but the output frequency increases each time the multiplication order increases by one.
The frequency is incremented by f _SLO , and the frequency initial setting error of the second oscillator 33 having the frequency f _SLO and the frequency temperature change are added, resulting in a frequency error. However, since the frequency of the first oscillator 32 is set as close as possible to the first local oscillation frequency,
The oscillation frequency of the second oscillator 34 is approximately 1/10 to 1/1000 of the local oscillation frequency in the configuration shown in FIG.
becomes. Therefore, the influence on the first local oscillation frequency due to the frequency error of the second oscillator 33 of frequency f _SLO is approximately 1/1 compared to that in FIG.
It decreases by 10 to 1/1000. For example, if the receiving frequency is
30.0GHz, 30.2GHz, and 30.6GHz, and assuming that the desired intermediate frequency is 2.0GHz, the first local oscillation frequencies of the first type of mixers 26 to 28 within the receiving sections 23 to 25 are 28.0GHz and 28.2GHz. GHz，28.4GHz，…
...becomes... Next, a plurality of second type mixers 29
~31, the frequency of the first oscillator 32 common to
When set to 27.8GHz, the second oscillator 33 multiplies the oscillator signal with a frequency of 200MHz by 1, 2, or 3.
Multiplication...200MHz, 400M obtained by multiplying by n
Hz, 600MHz, ...200nMHz signal. 1st
Since the oscillator 32 is common, the variation in the frequency interval of the first local oscillation frequency is 200 MHz.
is generated by multiplying the output of the oscillator 33.

Next, let us assume that the frequency initial setting error of an oscillator with a frequency of 200 MHz is +2×10 ⁻⁶ as a deviation, and that the temperature change in frequency is ±6×10 ⁻⁶ as a deviation. Assuming this, the frequency error that appears in the output of the multiplier for each difference in the multiplication order is +8 × 10 ^-6 as a deviation, which is 1.6KHz when converted to a frequency, and this error is
This appears as a frequency error at the local oscillation frequency. When the first local oscillation frequency is mixed with the reception frequency in the first type of mixers 26 to 28 and converted to an intermediate frequency, the error in the frequency interval of the first local oscillation frequency is the frequency error at the intermediate frequency. It appears. However, in the conventional repeater shown in FIG. 1, the variation in carrier frequency of the burst signal at the input terminal of the switching circuit 11 was 280 KHz, but according to this embodiment, the variation in carrier frequency is 280 KHz. It becomes 1/175.

According to this embodiment, it is possible to reduce variations in the intermediate frequency, and the burst signal converted to the intermediate frequency is transmitted after being switched and reorganized by the switching circuit 11. Even in this reorganized signal, the variation in the carrier frequency for each burst signal is sufficiently small, so when the receiving station receives the above signal and demodulates the burst signal, the demodulator receives the input signal sufficiently. can be followed,
This is extremely useful for SS/TDMA communication.

In the embodiment described above, the receiving units 23 to 25
Although a case has been described in which two mixers are provided inside the mixer, the number of mixers may be three or more and is not particularly limited. Further, although the frequency used is a quasi-millimeter wave band and the multiplication order of the multiplier is 1 multiplication or more, there are no particular regulations regarding these.

(Effects of the Invention) As explained above, in the present invention, a plurality of first type mixers are provided inside the plurality of receiving units, and a second type mixer connected to the first type mixer is provided. and a signal obtained by multiplying the signal from the first oscillator common to the second type of mixer and the signal from the second oscillator having a specific frequency f _SLO , respectively. , are converted to the first local oscillation frequency, and further mixed with the respective reception frequencies in the first type of mixer to convert to the same intermediate frequency, thereby making the variation in the intermediate frequency sufficiently small. Therefore, SS/TDMA
If this method is adopted in a communication system based on this method, demodulation can be performed effectively even when using a carrier wave in the sub-millimeter wave band.

[Brief explanation of drawings]

Figure 1 shows the conventional
FIG. 2 is a block configuration diagram showing an example of a relay device using the SS/TDMA method. FIG. 2 is a block configuration diagram showing an embodiment of a repeater according to the SS/TDMA system of the present invention using a quasi-millimeter wave band carrier wave.
FIG. 3 is a block diagram showing details of the second oscillator and a plurality of multipliers in FIG. 2. 1-4, 19-22...reception beam element, 5-
7, 23-25... Receiving unit, 8-10... Local oscillator, 11, 37... Switching circuit, 12-14, 38
~40... Transmission unit, 15-18, 41-44... Transmission beam element, 26-31... Mixer, 32, 33...
Oscillator, 34-36...Frequency multiplier, 45-48
...Output terminal.

Claims (1)

[Claims] 1. Compatible with multiple receiving frequencies,
a plurality of receiving sections each having a first mixer into which each of the received frequencies is input and a second mixer connected to a local signal input terminal of the first mixer; a switching circuit for rearranging the converted signal into a plurality of specified signals; a transmitting means for converting the rearranged signal into a signal of a desired frequency band and transmitting the signal; and each of the above-mentioned signals. A first oscillator for commonly providing a local signal to the second mixer, and a second oscillator for generating a common reference frequency signal.
and a plurality of multipliers for multiplying the frequency of the second oscillator with different multiplication orders corresponding to the plurality of second mixers, and the frequency of the first oscillator is increased. The local signal frequency of the first mixer is set close to that of the first mixer, and the difference between the local signal frequency of each of the first mixers and the frequency of the first oscillator is made an integral multiple of the frequency of the second oscillator serving as the reference. and the respective frequencies obtained by multiplying the output frequency from the second oscillator by different multiplication orders and the frequency of the first oscillator are multiplied by the second oscillator.
to each of the mixers to perform frequency conversion,
A heterodyne relay device characterized in that the local signal corresponds to each of a plurality of first mixers, and the local signal is configured to convert a plurality of reception frequencies into an intermediate frequency of the same frequency.