International Outer space - September 2003

Satellite TV broadcast antijamming strategy discussion
Zhu De lives
(Headquarters of the General Staff of the CCPLA correspondence department)

1 introduction
â-¡â-¡the satellite TV broadcast has the signal quality well, the coverage is broad and so on the characteristic, is one of our country television program transmission important channels. The area not yet completes which in the remote border district and the ground optical cable, the satellite link is the visual broadcast main channel. But because the broadcast television satellite all uses the transparent transponder, also transponder dual-mode antenna wave beam coverage big, face region broad, therefore its antijamming ability is worse. Beyond the border Falungong members in August, 2003 12, on 13th once more to Xin promise - 1 satellite illegal disturbance, also exposed the satellite TV broadcast in the antijamming aspect vulnerability. In view of the satellite transparent transponder characteristic, thoroughly studies the satellite broadcast television system the antijamming strategy, regarding safeguards our country satellite broadcast television system the reliable movement to have the important practical significance.

2 satellites transparent transponders characteristic
At present, our country uses in the visual broadcast satellite to belong to the stationary orbit satellite, its transparent transponder the television, the broadcast and the correspondence equisignal which sends in the ground enlarges after the frequency conversion retransmits the ground. Are limited as a result of Earth stationary orbit position resources and the wireless frequency resources, therefore the communication satellite space position and the operating frequency must to the international electricity association (ITU) report to a higher authority and must conform to the international stipulation, therefore the above parameter all is public.
One of transparent transponder major components is Gao Gongfang the component, generally is the travelling-wave amplifier (TWTA) or the solid state power amplifier (SSPA). Its most main characteristic is when the power input is smaller than the saturation point, may approximately think the work in the linear area. But when the power input further increases surpasses this level, the power amplifier enters the saturation area or the oversaturation area. In oversaturation area, not only the output greatly reduces, moreover appears the big compression of signal small signal, namely the so-called "power plunders the" phenomenon; Meanwhile as a result of non-linear factor, but also can appear the massive parasitic intermodulation component. In order to avoid on the general the power amplifier æZ¨å.¥ saturation area or the oversaturation area, therefore generally must implement the strict on good power control in its use, if adds the amplitude limiter in front of Gao Gongfang (hard amplitude limiter or soft amplitude limiter). After the restriction transparent transponder was allowed to avoid the power amplifier work in the oversaturation area, but if has the malicious disturbance the situation, the transponder still had the possibility to work in the non-linear area, still had the television signal the phenomenon which compressed, namely the "power plundered the" phenomenon to be still inevitable. Beyond the border the Falungong members are precisely use this weakness which on the star the merit puts to the visual broadcast signal implementation disturbance, moreover plunders the "phenomenon using the" power to carry on the illegal propaganda.

3 pair of satellite communications broadcast television disturbance way
Generally has 2 kinds to the satellite communication broadcast television signal disturbance, namely on line of disturbance and under line of disturbance. The next line of disturbance is broadcasts the ground receive to the satellite TV the under good signal implementation direct disturbance. Because is small to the under good link implementation disturbance equipment cover area, implements this kind of disturbance to have enable the noise source to approach the ground tracking station, also only can disturb or the few stands. But, if the disturbance side has the absolute superiority on the distance, then the simple equipment and a smaller power can extremely effective (specially be airborne jamming equipment, it has characteristic which mobility, is easy to launch). Because receives the geographical position the limit, this kind of disturbance was easily discovered.
The previous line of disturbance is to the satellite on good channel, namely to satellite transparent transponder implementation disturbance. As a result of satellite transparent transponder inherent characteristic, therefore so long as the noise source has the enough big power, or the big antenna gain, then can have the serious disturbance effect. Adds the present satellite receiving antenna coverage to be big, the noise source may establish in beyond the border, also was not easily discovered, therefore the previous line of disturbance is at present satellite communication broadcast television main conflicting mode.
The previous line of disturbance form also has many kinds of, if stops up the type disturbance and the emergency broadcast disturbs. Stops up the type disturbance is refers usurps the transponder the correspondence resources (power), completely blocks the transponder, causes completely to be paralysed through this transponder visual broadcast line. Its noise source frequency spectrum may overlap with the visual broadcast signal, also may not overlap. Another kind is the emergency broadcast disturbs, namely plunders the "emergency broadcast illegal signal using the" power, causes the normal work the receiver station station to receive the disturbance side the illegal signal. Because the present satellite receiving antenna has the very big cover scope, therefore (including beyond the border) can implement the disturbance in the satellite receiving antenna wave beam cover scope. Therefore, most is effective, the most serious disturbance is to a satellite transponder on line of disturbance, regarding the Earth stationary orbit communication satellite is so.
In summary, as a result of the satellite antenna coverage diagram and the transparent transponder characteristic, the enemy side countermeasure aircraft in our country mainland edge definitely can to our country correspondence tv broadcast satellite implementation disturbance. The malicious disturbance causes the correspondence â-¡p broadcast and the television service is unable normal carrying on, therefore must take the corresponding measure to come effectively to enhance our country satellite TV broadcast system obstinately to save the ability.
4 constructs integrated the satellite TV broadcast system
Compares with the satellite communication, the satellite TV broadcast has its inherent characteristic. As a result of television signal band width, moreover is to the multi- spots broadcast pattern, therefore usually uses in some antijamming measures which corresponds, like the direct sequence spread spectrum (DS), on the frequency-hopping, the star regenerates processing and the auto-adapted disturbance counterbalance technology and so on, not too suits the satellite broadcast television system. But fully uses the beam antenna technology and the ground fiber optic cable line, constructs the world integration design the satellite TV broadcast system, then may greatly enhance the satellite TV to broadcast obstinately saves the nature. Its main strategy includes:
(1) uses in the visual broadcast satellite transponder to receive, to send the antenna to separate, receiving antenna may establish is the flare angle is smaller than 1.5° the controllable spot beam antenna, but transmits the antenna to bestow on the shape antenna for the macrozonality; (2) Establishes the national unification the satellite TV broadcast launching base which is composed by many launching stations; (3) Each place television signal links through the ground fiber optic cable line and the launching base; (4) The satellite transponder receive beam antenna aims at the launching base; (5) To the satellite transponder implementation optimization design, including the intelligence gain control (Smart AGC) and so in the star processes. Such system may effectively prevent to the satellite transponder malicious disturbance.
At the same time, vigorously develops the research advanced double star localization technology, also is an extremely important action. The double star localization technology can promptly discover disturbs the position, thus takes the corresponding measure. Carries on the effective monitor and the control to each kind of electromagnetic environment also is extremely essential. Moreover, should establish the perfect strict laws and regulations system. The thorough investigation indicated that, the communication satellite user in aspect the and so on frequency, power and antenna direction use is not standard, frequently creates to the visual broadcast signal non- malicious disturbance, affects the reception of TV effect.
In brief, the satellite TV broadcasts the antijamming is a system question, must consider from the world integration design, like this can effectively guarantee our country satellite TV broadcasts normal operation. â- 

 

Receives the manuscript date: 2003-08-15