Wide Angle Frequency Sweep Antenna Array Research And Design

Electronic scanning antennas have found many applications and are rapidly advancing as the development of radar, communication, mobile TV reception in both commercial and military applications. Frequency scanning antenna is one kind of electronic scanning antenna, which beam can scan over a large angle for small changes in frequency. Because the scan angle, working frequency bandwidth and loss of slow-wave line frequency scan array are mutually constraint, in this thesis, two solutions are proposed to design frequency scan array with wide scan angle and high performance under limited bandwidth. The main contents are listed below:First is a strip line slow-wave line frequency scan antenna. In the design, the loss of some conventional planar transmission lines such as microstrip line, inverted microstrip line and strip line is investigated. It is found that the strip line is with lower loss compared with the other two lines in X-band. Furthermore, the bends of the strip line slow-wave structure are optimized to reduce the line loss caused by bend discontinuities, and the strip line slow-wave structure with low loss is designed. Then this strip line slow-wave structure is used to design frequency scan array. In the array, a coupling feed structure composed of strip line, slot coupling and microstrip patch is applied. The integrated Balun printed dipoles and the parallel strip line fed double-sided printed dipole antenna arrays are used as the radiating elements. Frequency scanning arrays of 8×4 elements,22×4 elements, and 22×8 elements are fabricated and measured. The results from measurement and those from simulation are in good agreement. In addition to wide angle scanning capability in one dimension under limited bandwidth, this proposed design is with light weight.Second is a waveguide frequency scanning array using hybrid coupling. In the structure, a low loss E-plane bent waveguide is used as slow-wave structure. The microstrip radiating antenna array is fed by a hybrid coupling technology which combines of the aperture coupling from slotted waveguide and microstrip feeding. The measured results show that the scan angle of this 22 elements array can achieve about 90°within 1GHz bandwidth in X-band, the side lobe level is all below-13.5dB, and the peak gain is 21dBi. Comparing with the traditional waveguide slot frequency scanning array, In addition to large scan angle and high efficiency, this proposed design is compact, with low profile, and can be easily expanded into a larger array.