Ehf Band Satellite Uplink Radio Frequency Link Key Technology Research

With the depletion of the microwave frequency resources and the development of millimeter-wave band technology, it becomes possible to develop high band system in satellite communication systems, where the EHF band (millimeter-wave band) is one of the preferred frequency bands available. EHF band referred here is in range of43.5GHz～45.5GHz.EHF band has a lot of advantages, such as large available bandwidth, small size devices, etc. Many countries, such as the United States, Britain and other developed countries, have already had mature EHF band satellite communication systems, and the technology of EHF band has been widely applied. Developing the EHF band satellite communication systems and improving the performance of RF devices is one of the urgent tasks in China. The choice of Intermediate Frequency conversion link, broadband low phase noise local oscillator and power combiner network is the key point of the study and also the difficulty of the design.According to the need of the project, the schemes of conversion link and power amplification are studied, and the scheme composed of L/S-band up-converter and EHF band transmitter is chosen. Meanwhile, the circuit design, circuit implementation and system testing are discussed. Especially, two key technologies composed of broad-band amplitude equalizer and bond-wire are analyed.In order to improve the amplitude-frequency characteristics of the system, the compensation solution of adding amplitude-equalize network is proposed. According to the analysis of equalizer, open microstrip lines and variable resistors are applied to achieve the changeable amplitude compensation in S-band. A good final test result is obtained, which solved the equilibrium problem of the broad-band amplitude.Because of the limit output power provided by the EHF-band single-chip (maximum P1dB of32dBm), it is necessary to employ the power combining technology to enhance the power of the amplifier module. In order to increase the output power of combining network, all kinds of factors influencing combining efficiency are studied and finally reducing the loss of bonding wire is chosen to improve the combining efficiency.By increasing the quantity of the bonding wires, widening the microstrip line and choosing proper line space, the loss of final power chip is reduced, which enhances the combining efficiency of the whole equipment. The theoretical calculation and actual tested data almost fit. According to the tested data, improvement of wire-bonding parameters can extensively enhance performance of the equipment.Finally, we present the complete equipments of L/S-band up-converter and the EHF band transmitter. The measurement results are as follows:P1dB power output is greater than40.3dBm (10.7W); third order intermodulation:-24.5dBc (P1dB power fallback3dB); the amplitude-frequency characteristics in2GHz bandwidth is2.2dB, and1.8dB within any500MHz bandwidth; the maximum of system spurious output is-61.3dBc.The results show that the EHF-band uplink radio link scheme is entirely feasible, which provides a strong technical support for future development of broadband satellite communications system in China.