Design Of Tightly Coupled Array With Periodic Structure

With the rapid development of modern wireless communication technology, tightly coupled array antenna is widely used in phased array radar system, space exploration, mobile communication and so on. Study of improving impedance bandwidth of tightly coupled array antenna is of great significance.The main contribution can be summarized as:1. A ring-type composite FSS structure loaded magnetic material above metal ground is studied. And a composite FSS structure loaded magnetic material is proposed. Single-layer FSS, double-layer FSS and FSS loaded magnetic material are simulated and optimizated respectively. And the influence of parameters on frequency characteristics of FSS is studied. The reflection coefficent of the structure is less than-10dB and the reflection phase is between -90-+90 degrees from 3.6 to 7.2GHz. In order to improve operation bandwidth, a structure consisted of double-layer FSS is proposed, and bandwidth is increased by 17%. On this basis, the bandwidth of FSS composite structure is further increased by loading magnetic material, in which the band for reflection coefficent less than-10dB is from 2.9 to 5.7GHz and the reflection phase changes smoothly between-90?+90 degrees.2. Based on the limit of matching bandwidth about tightly coupled array, methods of improving impedance bandwidth of tightly coupled array are studied.In order to reduce profile and increase bandwidth, infinite tightly coupled array antennas with sing-layer FSS, double-layer FSS and FSS loaded magnetic material are respectively proposed. Tightly coupled dipole elements are employed in the three cases. Simulation results show that the octave of impedance bandwidths of tightly coupled array are respectively 18.7,35.5 and 46.9 for single-layer FSS, double-layer FSS and FSS loaded magnetic material.3. A finite tightly coupled array antenna is studied. By loading single-layer FSS composite structure,1×8 and 2×8 tightly coupled arrays with single-layer FSS are studied, and the active VSWRs of different units when scanning are analyzed. A 1 x 8 tightly coupled array antenna with single-layer FSS is processed, assembled and tested,which achieves very low profile(0.17?low). The oversize of the array is A,?0×0.12?0. Test result shows that the proposed array can achieve 3.5:1 bandwidth,which has a good agreement with simulation result. A 28 tightly coupled array antenna with FSS loaded magnetic material is proposed, and the impedance characteristics of different units are analyzed. The proposed array can achieve gain of 6.5dBi (array size:0.15? × 0.6?),9dBi (array size: 0.5?×2?), and 18.4dBi (array size:1.1? × 4.4?) at 1.5GHz,5GHz and 11GHz. Compared with 2×8 array with single-layer FSS, loading magetic material can effectively improve the impedance matching of tightly coupled array antenna and 5:1 operation bandwidth is realized.