JPH0231528A - Satellite repeater monitoring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a satellite repeater monitoring device that measures the characteristics of a satellite repeater from the ground.

[Conventional technology]

Figure 3 shows, for example, IEEE PROCEEDING VOL.
, 134. Pt.

F, No, 5. This is a part of a conventional satellite repeater monitoring device announced in AUGUST 1987. In the figure, 1 is an AM modulator, 2 is an xv4!4 generator that generates an IF signal that becomes a carrier signal, and 3 is AM for performing AM modulation on the carrier signal of IF signal generator 2.
4 is a modulated signal generator, 4 is an amplifier converter that converts the modulated IF multiplied signal, RF multiplied signal, 5 is a high power amplifier that amplifies the RF multiplied signal, 6 is a transmitting/receiving antenna, 7 is the satellite whose characteristics are to be measured, 8 is the satellite 7 9 is the received RF multiplied signal I.
10 is an AM demodulator that demodulates the transmitted AM modulated wave; 11 is a demodulated A down converter that converts it into an F signal;
This is a monitor device that monitors the M signal component.

Next, the operation will be explained. When measuring the input/output characteristics of a satellite repeater, the AM modulator l receives the I from the IF signal generator 2.
The baseband signal from the AM modulation signal generator 3, which becomes the F signal and the modulation signal, is input.

The modulated wave output from the AM modulator 1 is converted from an IF signal to an RF signal by an upconverter 4, is further amplified by a high power amplifier 5 such as a TWTA, and is transmitted via a transmitting/receiving antenna 6 to a satellite! 7.

The satellite 7 is equipped with a transmitting/receiving antenna and a repeater for receiving and amplifying transmitted radio waves from the earth station, and further transmitting the radio waves to the earth station. One of the characteristics of the repeater installed on this satellite is the input/output characteristic, and by measuring this, it is confirmed that the repeater is transmitting radio waves at the base transmission power over its lifetime. 0 Normally, this measurement is performed by the control station that manages the satellite, which transmits an RF carrier of any frequency within the band of the repeater to a repeater that is not currently in use, and relays the transmission level. The saturation point of the repeater is the point where the output power increases to zero with respect to the increase in the input power of the repeater.Normally, the satellite input side at this saturation point. Saturation power flux density of output side, saturation E I RP of
(EffectiveIsotropically
Measure the strength of radio waves heading towards the Radiated PowerH satellite. The former is determined from the earth station transmission level when saturation is indicated, and the latter is determined by back calculation from the earth station reception level when the same saturation is indicated.

The signal returned by the satellite enters the transmitting/receiving antenna 6 of the earth station, is amplified by a low noise amplifier 8, is converted from an RF signal to an IF signal by a down converter 9, and is then extracted as a demodulated signal by an AM demodulator 10. This demodulated signal is then measured by a monitor device 11 or displayed on a screen in the form of a waveform.

As the transmission level of AM modulated waves to the satellite is increased,
As shown in Figure 4, when the transmission power level from the earth station is in the linear region of the input/output characteristics of the repeater, the spectrum of the earth station received wave includes sideband waves due to AM modulation, as shown at the bottom of the figure. have. As the transmission level is further increased, the repeater enters the saturation region, and the sideband waves caused by AM modulation disappear due to the saturation characteristics of the repeater.As the transmission level is further increased, the repeater becomes oversaturated and the sideband waves are generated again. appears.

Therefore, when observing this sideband wave or demodulated waveform on the receiving station side, the amplitude of the sideband wave or demodulated wave will be at its minimum at the saturation point of the repeater.This allows the saturation point of the repeater to be detected, and the The saturated power flux density is determined from the earth station transmission power level, and the saturated EIRP is determined from the reception level.

[Problem to be solved by the invention]

In measuring the input/output characteristics of a repeater using a conventional satellite repeater monitoring device, the satellite repeater is operated in the saturation region, but depending on the frequency band, the repeater is operated in the saturation region due to ground power flux density constraints. There are cases where it cannot be made to work. In particular, for those frequency bands that are already in use, such as on terrestrial micro-circuits, the terrestrial power flux density is kept low due to interference with them. The AM modulation method that has been used has a problem that it cannot be used because the power flux density of the carrier component is high.

This invention was made to solve the above-mentioned problems, and allows repeaters to operate up to the saturation region even in frequency bands where terrestrial power flux density is severely restricted. It is an object of the present invention to provide a satellite repeater monitoring device capable of detecting the saturation point of a satellite repeater.

[Means to solve the problem]

The satellite repeater monitoring device according to the present invention performs FM modulation on an IF carrier signal using a symmetrical triangular wave to spread energy, further performs AM modulation on this FM modulated wave, converts it into an RF flaw signal, and transmits it to the satellite. After receiving the signal via the satellite repeater and converting it to an IF signal, it passes through an AM demodulator and a bandpass filter whose center frequency is equal to the AM modulation signal frequency, and outputs it to a monitor device. be.

[Effect]

In the satellite repeater monitoring device according to the present invention, first, in order to solve the constraint on ground power flux density, energy is spread by FM modulating the carrier with a symmetrical triangular wave.
AM modulation is performed to obtain M modulated waves, and a bandpass filter is inserted after demodulation to separate the AM modulated signal component from the symmetric triangular wave component for energy diffusion.
Only the AM modulation signal component is extracted and output to the monitor.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 12 is an FM modulator for performing energy diffusion, 13 is an FM modulation signal generator input to the FM modulator 12, and 14 is an FM modulation signal generator for separating the AM modulation signal component from the FM modulation signal component after AM demodulation. It is a bandpass filter.

Next, the operation will be explained. A symmetric triangular wave is output from the FM modulation signal generator 13 and connected to the baseband input terminal of the FM modulator 12. As a result, the IF carrier inside the FM modulator 12 is FM-modulated by the FM modulation signal. The reason why FM modulation is performed using a symmetric triangular wave is to spread the carrier so that the amplitude is constant on the frequency axis. This F
The M modulated waves are subjected to AM modulation by the next AM modulator 1. Generally, the modulation index of this AM modulation is small, about 5 to 15%. This spreads energy and performs AM modulation, making it easier to measure saturation characteristics.

The reason why AM modulated waves are used in this saturation characteristic measurement is that they are less susceptible to fluctuations in loss during radio wave propagation than non-modulated waves. In other words, even if level fluctuations occur due to fading or the like in the propagation path, the waveform due to AM modulation is preserved, making it easy to find the saturation point.

The modulated carrier that has passed through the satellite repeater is received by the earth station, converted to an IF band by the down converter 9, and demodulated by the AM demodulator 10. In order to extract only the AM modulation signal component by the demodulator 10, the signal is passed through a bandpass filter 14 corresponding to the AM modulation signal frequency, thereby removing the FM modulation signal component and carrier component for energy diffusion. Thereafter, the AM modulated signal component is monitored, and the AMfil [signal amplitude exhibits a minimum at the saturation point of the satellite repeater, as in the conventional case.

As the transmission level of the FM-AM modulated wave to the satellite is increased, as shown in Figure 2, the earth station received wave when the transmission level from the earth station is in the linear region of the input/output characteristics of the repeater. As shown in the lower part of FIG. 2, the spectrum appears to be a spread of spectrum A due to FM modulation and sideband B due to AM modulation.

As the transmission level is further increased, the repeater enters the saturation region, and sideband waves due to AM modulation disappear due to the saturation characteristics of the repeater. As the transmission level is further increased, the repeater becomes oversaturated and the sideband B appears again in a diffused form. Therefore, when observing this sideband wave or demodulated waveform on the receiving station side, the sideband wave or demodulated wave reaches its minimum at the saturation point of the repeater. As a result, the saturation point of the repeater can be detected, and the saturation power flux density can be determined from the earth station transmission power level at this time, and the saturation EIRP can be determined from the reception level.

〔Effect of the invention〕

As described above, according to the present invention, the A
By connecting an M modulator and using a bandpass filter on the receiving side to extract only the necessary AM modulated signal components, the saturation characteristics of the satellite repeater can be measured even in frequency bands with severe ground power flux density. By performing AM modulation at the same time, the saturation point of the satellite repeater can be easily detected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a satellite repeater monitoring device according to an embodiment of the present invention, and FIG. 2 is an earth station received modulated wave spectrum for each region of the input/output characteristics of the satellite repeater according to an embodiment of the present invention. FIG. 3 is a block diagram showing a conventional satellite repeater monitoring device, and FIG. 4 is a diagram showing the earth station received modulated wave spectrum for each region of the input/output characteristics of the conventional satellite repeater. 1 is an AM modulator, 2 is an IF signal generator, 3 is an AM signal generator, 4 is an up converter, 5 is a high power amplifier,
6 is a transmitting and receiving antenna, 7 is a satellite, 8 is a low noise amplifier, 9
is a down converter, 10 is an AMail device, 111*
12 is an FMi adjuster, 13 is an FM modulation signal generator, and 14 is a bandpass filter. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A satellite repeater monitoring device for measuring the saturation characteristics of a satellite repeater includes an FM modulator and an AM modulator that perform FM modulation and further AM modulation on a carrier, and transmit this carrier to the satellite via the repeater. What is claimed is: 1. A satellite repeater monitoring device comprising: an AM demodulator that receives a carrier and performs AM demodulation thereof; and a bandpass filter that extracts an AM modulated signal component after the AM demodulation.