Research And Implementation Of HF Antenna Auto-tuning System

Affected by the mode of transmission, HF communication has been widely applied in the field of military, emergency, etc. Especially the new technology including frequency hopping, adaptive, software radio appeared in recent years, HF communication is becoming one of the research focus again. As a short-wave radio, especially the frequency hopping radio, automatic antenna tuning system must have fast tuning speed, high stability, and therefore its research and improvement is particularly important.Affected by short-wave frequency coverage factor, the whole band shortwave antenna design is greatly difficulty. The role of short-wave antenna tuning system is fast full-band tuning, improving the efficiency of the radio transmitting, extending the actual using bandwidth of the antenna. The system consists of parameter detection, tuning network and control part.In hardware design, micro-power complex parameter detection solution is designed for the detecting part. The automatic antenna tuning system, detecting VSWR, impedance magnitude and phase, frequency and other parameters simultaneously, can estimate the impedance quickly, which greatly improves tuning speed; Micro-power detecting reduces the possibility of the final radio amplifier to be damaged by the reflected power in the tuning process, and improves the possibility of achieving the network structure by PIN diodes. After calculating and ADS simulation, we use the ? type and anti ? type network structure, with low-pass characteristic, and the tuning element parameters are determined by the 8-bit binary value. Finally, all the three parts of schematics and PCBs are designed, and the key components' debugging and design is discussed.In software design, system flow chart is designed for increasing the tuning speed. While system is running, memory tuning mode is the first choice in order to improve the tuning speed. If the memory tuning fails, the search tuning will work. Search tuning mode is the major impact of the tuning time for automatic antenna tuning system in the first time. A detailed description of the search tuning process, based on the calculation of the auxiliary impedance, is discussed, including determining the impedance region, calculating the tuning parameter and fine tuning parameters. The frequency counter is added the sample selection mode, reducing interference to the counter. Finally, the tuning process is achieved by programming on the embedded controller.After the system design is completed, the test results and analysis for the parameters of the automatic antenna tuning system modules are given. And the test results for the parameters of the automatic antenna tuning system, including tuning time, impedance tuning range and so on are given. After the test results analysising, gives the system design can be optimized place.