Research On Frequency Reconfigurable Antenna And Feed Network With Tunable Function

Under the background of the increasing shortage of spectrum resources,wireless communication systems are developing towards miniaturization,multi-band,multi-function and intelligence,which requires more on hardware devices.It is obvious that increasing the number of microwave devices and antennas alone cannot meet the growing complex communication environment and expanding business requirements.In order to overcome this bottleneck,reconfigurable technology came into being,which aims to integrate multiple functions with a single component to meet the diversified needs of the system.As important carriers of reconfigurable technology,antenna and feed network are the key research directions of reconfigurable technology.This thesis focuses on the research of frequency reconfigurable antenna and feed network with switchable functions.The main work is summarized as follows:（1）A frequency reconfigurable circular microstrip patch antenna is proposed,which realizes the switching between four operating frequencies of 2.4GHz,2.58GHz,2.7GHz and 2.744GHz.The influence of loading various shapes of slots on the resonant frequency of TM₁₁mode of the patch antenna are analyzed.After the initial realization of frequency separation,aiming at the problem of antenna mismatch,short-circuit pins and stubs are introduced for impedance matching,which finally makes the return loss of the four frequencies better than 14d B,both with side-fire beams,and their gains are above 4d Bi.（2）A single-layer wide-band phase shifter is proposed,achieving 45°phase shift from 1.6-4.16GHz,and meanwhile exhibiting a band pass filter response.The proposed phase shifter is composed of a stub-loaded transmission line with a delay line and an Open-circuited three-line MMR both providing filter function.The relative bandwidth of the phase shifter is 88.9%,the in-band return loss is better than 11.3d B,and the in-band phase shift deviation is less than±3°.The measured results are in good agreement with the simulation ones.（3）A function-tunable feed network is proposed,which composed b a broadband 3d B parallel-coupled line power divider,a dual-frequency/single-frequency switchable bandpass filter and a cascaded Schiffman phase shifter.The feed network has dual-band/single-band switchable frequency response and switchable phase shift response at the same time.The proposed feed network achieves a dual-band dual-phase shift response with a constant phase shift of 90°±5°over 2.27GHz to2.51GHz（10.04%）and 270°±10°over 5.7GHz to 5.9GHz（3.45%）;a dual-band dual-phase shift response with a constant phase shift of 45°±5°over 2.21GHz to 2.57GHz（15.5%）and 135°±10°over5.72GHz to 5.95GHz（3.94%）,a single-band single-phase shift response with a constant phase shift of 90°±5°over 3.95GHz to 4.3GHz（8.5%）and other working modes.A circular microstrip patch antenna is excited by the proposed feed network,realizing polarization reconfiguration function.When the antenna works in the circular polarization state,the circular polarization bandwidth is9.48%,and the impedance bandwidth is 17.4%when working with linear polarization.