Research And Design Of Microstrip Patch Antenna With Harmonic Suppression

With the rapid development of communication technology,the RF front-end devices with single-function can no longer meet the requirements of communication in different environments.Therefore,highly integrated multi-functional antennas are gradually replacing single-functional antennas and becoming a new research hotspot.Meanwhile,with the rapid growth of the amount and varieties of wireless terminal devices,more and more communication frequency bands are demanded in different fields.The continuous improvement of spectral efficiency also brings new challenges that electronic devices in adjacent frequency bands are susceptible to interference with each other.Therefore,in the design of wireless communication system,antenna as a key device to transmit and receive radio frequency signals needs to be equipped with the function of harmonic suppression,which ensures the stability and reliability of the entire wireless communication system.As such,this thesis is aiming to propose a new method to design a class of microstrip patch antennas with wideband harmonic suppression characteristics,and the main work includes:（1）Proposing a double-point inserted feeding method and designing a microstrip patch antenna with wideband harmonic suppression.Firstly,the rectangular microstrip patch antenna with single feeding point has been simulated and analyzed by the 3-D electromagnetic simulation software Ansoft HFSS.The radiation pattern at the harmonics has been discussed and summarized.A double-point inserted feeding method is proposed without introducing additional filtering circuit.The proposed feeding scheme can suppress the high-order modes effectively by arranging the feeding positions at the intersection of the electric wall of the harmonics.Based on this feeding method,a double-point inserted feeding patch antenna is designed.The operating frequency of the designed antenna is at 2.45 GHz,and the 10-d B bandwidth is about 20 MHz.The microstrip patch antenna using this double-point inserted feeding structure can effectively suppress the excitation of TM₀₂ mode,TM₁₂ mode,TM₂₀ mode,and TM₂₂mode,leading to 2.8f₀ harmonic suppression.In addition,the antenna has good radiation performance at the operating frequency with a gain of 7.4 d Bi.Finally,the designed antenna is fabricated,and the tested results are in good agreement with the simulated results.（2）Proposing a multi-point inserted differential feeding method and designing a microstrip patch antenna with enhanced harmonic suppression.Firstly,based on the afore-mentioned double-point inserted feeding structure,a multi-point inserted differential feeding method has been proposed.The even-order harmonics can be well suppressed by the proposed differential feeding method,leading to an enhanced stopband performance.Based on this differential feeding scheme,a multi-point inserted differential feeding microstrip patch antenna is designed.The operating frequency of the designed antenna is at 2.45GHz,and the 10-d B bandwidth is about 20 MHz.The adopted multi-point inserted differential feeding method can effectively suppress all high-order harmonics within 4 f₀.Similarly,the antenna has good radiation performance at the operating frequency with a gain of 7.5 d Bi.Finally,the designed differential fed antenna is fabricated and measured.The results show that the designed microstrip patch antenna has obvious harmonic suppression performance and good radiation property.（3）On the basis of the double-point inserted feeding microstrip patch antenna,a double-layer stacked structure is introduced to improve the radiation bandwidth of the antenna.Finally,a microstrip patch antenna with enhanced bandwidth and harmonic suppression characteristics is designed and developed.For the above microstrip patch antenna with double-point inserted feeding structure,although good harmonic suppression performance has been achieved,the bandwidth is only 0.82%due to the adoption of a thin dielectric substrate.With the introduction of the double-layer structure,the antenna has two radiation modes,and the radiation bandwidth of the antenna has been increased to 12.47%,which is 15.2 times that of the original antenna.Finally,the designed wideband antenna is fabricated and measured.The tested and simulated results are in good agreement.It has been proved that the antenna in this stacked configuration not only improves the bandwidth significantly,but also does not introduce additional high-order harmonics.The antenna still has good harmonic suppression performance.