Research On Antenna For Island Hf Surface Wave Radar

HF surface wave radar(HFSWR) can achieve real-time monitoring to the sea, which has the characteristics of a large monitoring area, low running costs, all-weather work, great ability of anti-interference, over the horizon, and so on. Due to the limits of operating frequency(3~30MHz) and detection requirements, the size and area of received antenna array for HFSWR must be large enough.Because of the shortness of coastline resources now, the study of HFSWR is turnning to erecting small-size antenna on the island. According to the characteristics of special environment and complex terrain for the island, the performances of antenna are researched. The article is organized as follows.In the first part, aiming at the problem that antenna elements are damaged easily and repaired difficultly in the harsh environment of the island, the effect of the location and number of failure sensors on the array pattern and DOA estimation is discussed firstly. Then the position of a single failure sensor can be found according to the characteristic of pattern. Finally two compensating methods are proposed for pattern and DOA estimation, which are respectively least square error synthesis with nulls for beam pattern and isolating the failure sensors.The simulation results show that the closer to the middle of array the damaged position is, the worse the performance is.It also shows that two compensating methods for pattern and DOA estimation achieve very good effect, and the feasibility of the method is verified by the data of HFSWR.In the second part, aiming at the problem of slope, surface irregularity and difficult arraying, the effect of different terrain on the antenna pattern is analyzed firstly. Beamforming weights are adjusted to achieve the correction according to the phase relationship between the terrain slope and the antenna. Sparse array is deployed on hills and ravines to overcome impedent terrain. Genetic algorithm is used for the element spacing optimization of sparse array and chebyshev weighting are applied for further optimization of side-lobe level. The simulation results prove the validity of the compensation algorithm and the practicability of sparse array.In the third part, aiming at the problem that antenna array laying the ground net is difficult on the island, the model of dipole antenna and antenna array are established firstly. Compare the characterics of input impedance, the maximum radiation angle of elevation, reflection loss, resonant frequenc y, voltage standing wave ratio before and after laying the ground net. Then change the size, shape, vertical distance of the ground net, and calculate the main comparative antenna parameters above. The simulation results may give some theory support on the design of antennas for island HFSWR.In the fourth part, aiming at the problem of mutual coupling on arrays, the effect of mutual coupling on the array pattern and DOA estimation is discussed firstly. A method based on cyclic iteration to estimate the mutual coupling coefficients of arrays are brought out, which iterate until convergence to the optimal solution. Use this method to correcte array mutual coupling for uniform linear array, uniform circular array and semi-arcwise conformal array antennas with island. The simulation results show that small arrays is affected by mutual coupling more seriously, and it also proves the validity of this method.