Study On Dual-band Broadband Single-Layer Microstrip Reflectarray

The microstrip reflectarray antenna as an emerging high-gain antenna, compared withparabolic antenna, is superior in its light weight, small size, low cost, easy to manufacture, easyto assemble, easy to integrate, etc. Compared with the microstrip array antenna, it overcomes thedilemma of the big losses in feeding network transmission. It has become a hot topic in theantenna’s research field and one of the main research directions for the future large high-gainantenna ever since it came into being.To solve the problem of the narrow bandwidth in the microstrip reflectarray antennaperformance, this paper based on the study of broadband and dual-band reflectarray, proposed anew single-layer dual-beam dual-band broadband reflectarray antenna. To meet the demand ofsingle-layer dual-band design, two new broadband elements for different frequency bands aredesigned, which have linear smoothing of the phase curve in the low-band6GHz-7GHz andhigh-band8GHz-9GHz respectively. In order to combine the two broadband elements into onedual-band antenna, the paper comes up with the concept of dual-polarized design andexperiments on its feasibility. Then，the microstrip reflectarray with the proposed elements isdesigned and simulated. The result shows that the bandwidths are13.7%at low-band1.5dBgains and11.8%at high-band1.5dB gains.The two main beam directions accord with ourexpectation. Finally, the experiment shows that the actual results and the simulation results areconsistent, which verifies the effectiveness of the antenna design.The main innovations of this paper are as follows：1. This article puts forward the concept of element phase bandwidth and concludes with twostandards to measure the characteristics of broadband element phase curve. It also opens in-depthdiscussions on the contents of these two standards, which builds up the direction for optimizingthe curve.2. Concerned with the speciality of single-layer dual-band antenna, we innovatively designthe structure of two new broadband elements. In order to optimize the phase characteristics, thedesigning process of the two elements is introduced in detail. It also brings forward the designidea ‘Break up the whole into parts，from simple to complex’ based on the summarization of thebroadband design method.3. Explorations are made to the miniaturization and cross-polarization of the elementstructure in the element design optimization. Through the study of the phase curve，we draw thecorollary that the double resonant phase curve superimposes on the phase shift range, whilemaintaining the characteristics of the independent single resonant phase curve.4. For the problems brought up by the influence of the low and high frequency elements, itcreatively comes up with an ideal assumption from the aspect of radiation, and adual-polarization solutions based on that. In order to verify the feasibility of designed ideas, thephase characteristics analysis and energy transmission characteristics analysis are presented andused to analyze the independent high and low frequency element and coplanar structure. 5. The tests on the arrays show that the dual-band bandwidth is more than10%at1.5dBgains, while in the relevant literature from both at home and abroad, it is generally less than5%.