JPH0356021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a satellite communications earth station transmission power control system.

Satellite communications, especially satellite communications that use high frequencies such as sub-millimeter wave bands, are subject to significant attenuation due to rain, and appropriate countermeasures are required to deal with this.

For downring, it is considered appropriate to provide a margin in the earth station receiver to compensate for the attenuation, or to use a site diversity method to eliminate the effects of rain.

On the other hand, for uplinks, apart from using the site diversity method, using a transmission power with a certain predetermined margin against rain attenuation means that the satellite's transmission power is reduced by that amount during clear skies. This results in unnecessary consumption, which is very disadvantageous from the viewpoint of effective use of satellite transmission power.
Therefore, a method of controlling the transmission power from the earth station according to the amount of attenuation of uplink rainfall has been considered, and this method is generally called earth station transmission power control.

Transmission power control systems for such purposes are described, for example, in the 1981 Institute of Electronics and Communication Engineers General National Conference Proceedings, Paper No. S10-11 "Semi-millimeter wave vehicle-mounted station communication system" (pages 8-293, 294), and Although it has already been proposed in Proceedings of the National Conference of the Optical and Radio Division of the Institute of Electronics and Communication Engineers, Paper No. 182 "Compensation method for uplink rain attenuation of BS main station" (Page 182), the former is based on line quality (S/N). Since two pilot lines for measurement are set up between the partner station and the partner station, there are disadvantages in that the partner station is required and a frequency is dedicated for this purpose. In addition, the latter method requires specific facilities on the satellite side in advance because it detects the received power on the satellite side and sends it out on a telemeter signal.
Another method is to estimate and control uplink attenuation using the correlation of rain attenuation between uplink and downlink frequencies based on the drop in the level of the received signal transmitted from the own station and reflected back by the satellite. However, the disadvantage is that control errors due to variations in individual cases cannot be avoided.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, do not require a specific partner station, a dedicated frequency for control, or specific facilities on the satellite side, and do not cause estimation errors due to variations in correlation data. An object of the present invention is to provide a satellite communication earth station transmission power control method.

The satellite communication earth station transmission power control method of the present invention includes:
A satellite communication earth station that communicates via a satellite includes a beacon receiving means for receiving a beacon signal emitted from the satellite, and a transmission power control means for transmitting a pilot signal or a communication signal or both toward the satellite. and loop-receiving means for receiving a return signal obtained by returning the pilot signal or communication signal via the satellite; N) and a comparison control means for generating a control signal for controlling the transmission power of the transmission means so that the value thereof matches a predetermined value.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, which is a single channel per carrier (SCPC).
This is an example of an earth station using the method. 1 is an antenna for both transmitting and receiving, 10 is a low noise amplifier (LNA), 1
1 is a hybrid (H) that branches the signal into two, 12
13 is a down converter (D/C) that converts the beacon signal to an intermediate frequency; 13 is a beacon receiver (BCN REC) that receives the beacon signal and generates an antenna control signal (ANT CONT) and a beacon level output 101; The beacon receiving means is composed of five elements. Also, 20 is SCPC
A pilot signal oscillator (PIL OSC) serves as the reference frequency of the system, a combiner (COMB) 21 combines the pilot signal and a communication signal (TX SIG), and an intermediate frequency amplifier (22) whose gain can be controlled by a control signal. AMP), 23 is an up converter (U/C) that converts the intermediate frequency signal to a transmission frequency, and 24 is a transmission power amplifier (HPA) that amplifies the output of the U/C to obtain the necessary transmission power. Together with the antenna 1, it constitutes a transmitting means capable of transmitting power control for transmitting pilot signals and communication signals. Furthermore, 14 is a communication down converter that converts communication signals including pilot signals returned via the satellite into intermediate frequencies, 15 is an intermediate frequency amplifier (IF AMP) that amplifies the output, and 16 is an IF AMP. Output (RX
SIG) via a directional coupler, the AFC signal is sent to the local oscillator of the D/C14, and the AGC signal is sent to the IF.
A pilot signal receiving section (PIL) supplies the pilot level output 102 to the comparator 17 in the AMP15.
REC) constitutes a return receiving means together with antenna 1, LNA 10, and hybrid 11, and BCN
A comparator (COMP) 17 that compares the level output 101 of the REC 13 and the level output 102 of the PIL REC 16 and outputs the ratio, and a control signal 103 that controls the gain of the VG AMP 22 so that its output always maintains a constant value. A transmission power control panel (TPC CONT) 18 that generates the power and the transmission power control panel (TPC CONT) 18 constitutes a comparison control means.

FIG. 2 is an explanatory diagram of the operating principle of the present invention, showing the relationship between uplink and downlink rain attenuation and transmission and reception power. The uplink pilot signal 4 radiated from the earth station (E/S) 2 with an effective radiated power P ₀ provides power to the satellite station (S/S) 3 during clear weather.
It is received at P _r (P _r ′ during rain), frequency converted and amplified by the satellite transponder, and then radiated from the satellite with effective radiated power P ₁ (P ₁ ′ during rain). This downlink pilot signal returned by the satellite 5
is E/S with received power P ₂ in sunny weather (P ₂ ′ in rainy weather)
Received at 2. The beacon signal 6 in the same frequency band as this downlink pilot signal is radiated from the satellite with an effective radiated power (EIRP) of B ₁ , and the E/S2
The signal is received with received power B ₂ (B ₂ ′ during rain). If the uplink rain attenuation is Δα and the downlink rain attenuation is Δβ, then according to many research results published so far, Δα ≠ Δβ for uplink and downlink, which have different frequency bands, and the difference between the two is Δα. Although the correlation is not perfect and there is some variation, it can be safely assumed that within the uplink or downlink frequency band, the rain attenuation is almost the same regardless of the frequency, and the correlation is almost 1. Therefore, the reception power B ₂ ', P ₂ ' of the pilot signal and beacon signal at the earth station during rainy days is calculated by β ₁ and β ₂ , The receiving gain at each frequency of the earth station antenna is G ₁ and G ₂ ,
Then, B ₂ ′=B ₁・β ₁・Δβ・G ₁ =Δβ・B ₂ P ₂ ′=P ₁ ′・β ₂・Δβ・G ₂ =Δα・P ₁・β ₂・Δβ・G ₂ = It is given by Δα・Δβ・P ₂ , and when you take the ratio, it becomes P ₂ ′/B ₂ ′=Δα・(P ₂ /B ₂ ), and the received power ratio of the pilot signal and beacon signal during rainy weather is The uplink rainfall attenuation can be determined from the change over time. Now, if we control the transmission power so that the received power ratio during rainy days is the same as when it is sunny, the EIRP of beacon signal 6 is constant regardless of rain or shine, so the EIRP of downlink pilot signal 5 will be the same as when it is sunny. It will be controlled to have the same value.

In the circuit of the embodiment shown in FIG. 1, an output corresponding to the received power of the beacon signal is obtained from the output 101 of the BCN REC 13, an output corresponding to the received power of the pilot signal is obtained from the output 102 of the PIL REC 16, and the received power ratio is calculated. The beacon receiving system including BCN REC13 and the pilot receiving system including PIL REC16 both have linear output characteristics with respect to decibel input, and COMP17 generates a control signal by determining the magnitude of The configuration is such that the differential voltage is extracted after being appropriately amplified so that the characteristics match. This voltage, which corresponds to the received power ratio of the beacon and the pilot, is TPC CONT1.
8 and compares it with the voltage corresponding to the received power ratio under clear weather conditions, and generates a control output 103, thereby automatically controlling the EIRP of the pilot signal at the satellite to always be constant. Temporal fluctuations in attenuation due to rain are not so sudden, and even if the response time of the control system is selected to be long compared to the approximately 0.3 seconds required for radio waves to return to the satellite, sufficient effects can be achieved.

In the above embodiment, the pilot signal is used at the earth station that performs SCPC communication, but in the earth station using the FM multiple channel method, even if the communication signal wave transmitted by the own station is received back, the same transmission power will be required. can be controlled. Furthermore, a station dedicated to monitoring and control that does not perform communication can emit only a specific pitch signal and provide a pitch signal with a constant EIRP. It goes without saying that the method of detecting the reception power ratio of the pilot signal and beacon signal and the method of controlling the transmission power are not limited to the circuits of the embodiments.

Furthermore, in the previous explanation, a method was described in which the level of the beacon signal and the pilot signal or communication signal reflected by the satellite, that is, the ratio of the received power, is made constant, but instead of the received power ratio, the C/N of both signals is Almost the same operation is possible using the ratio of . Noise in the earth station reception system is generally dominated by the antenna system and the LNA that performs broadband reception, and has almost the same noise temperature for beacon signals and pilot signals. In addition, the equivalent noise temperature of the propagation path increases with rain attenuation, but this has almost the same effect on frequencies within the reception band as does rain attenuation. In the uplink as well, the noise temperature of the propagation path increases with rainfall attenuation, but the noise temperature of satellite receivers is generally much higher than that of the earth station, and rain attenuation has little effect on the total noise temperature of the uplink. I won't give it. In general, uplink noise contribution is less than downlink noise, but while uplink noise is added to the return signal, beacon signals do not have this noise, so when C/N is used, the C/N of both signals is Although controlling the satellite's EIRP to be the same as on clear skies does not make the satellite's EIRP constant, it does have the effect of sufficiently compressing its fluctuations.
Furthermore, when C/N is used, there are no restrictions on the gains and AGC characteristics of both receiving systems after branching at the hybrid 11 shown in FIG. 1, and there is an advantage that the COMP 17 is also simplified.

In addition, when using C/N, it is also possible to further compress the fluctuations in satellite EIRP by using a certain predetermined correction for the uplink noise contribution based on the C/N or level of the beacon signal. be.

As explained above, according to the present invention, there is no need for a specific partner station, a dedicated frequency for control, or specific facilities on the satellite side, and the transmission power of a satellite communications earth station is free from estimation errors due to variations in correlation data. This has the effect of realizing a control method.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is an explanatory diagram of the operating principle of the present invention. 1... Antenna, 2... Earth station, 3... Satellite station, 4, 5... Pilot signal, 6... Beacon signal, 10... Low noise amplifier, 11... Hybrid, 12, 14... Down converter , 13...
... Beacon receiving section, 15 ... Intermediate frequency amplifier, 1
6...Pilot signal receiving section, 17...Comparator,
18... Transmission power control board, 20... Pilot signal oscillator, 21... Combiner, 22... Intermediate frequency amplifier, 23... Up converter, 24...
Transmission power amplifier.

Claims (1)

[Claims] 1. In a satellite communication earth station that communicates via a satellite, a beacon receiving means that receives a beacon signal emitted from the satellite, and a transmission power control that sends a pilot signal, a communication signal, or both toward the satellite. Compare the level or carrier-to-noise power ratio of the beacon signal and the return signal with a return reception means for receiving a return signal obtained by returning the pilot signal or communication signal via the satellite. and comparison control means for generating a control signal for controlling the transmission power of the transmission means so that the value thereof matches a predetermined value.