Research On Novel Filtering Microstrip Antennas And Arrays

With the rapid development of wireless communication,communication devices present the trend of miniaturization,integration and multi-function.The filtering antenna integrates the functions of both the antenna and the bandpass filter at the same time,which can effectively reduce the size,loss and cost of the system,and has become a research hotspot in the field of antenna design.Compared with the co-design method using complex filtering circuits(or filter)to achieve the filtering function,the method of fusion design as well as the method of combining fusion design and co-design do not need to introduce complex filtering circuits,and thus the structure is simpler,the integration degree is higher,and the radiation efficiency of the antenna is also higher.On the other hand,the microstrip antenna is widely used in wireless communication systems bescause of its light weight,low profile,easy integration and easy processing.Based on the above background,four novel filtering microstrip antennas or array with high performance are designed and implemented by the method of fusion design or the method of combining fusion design and co-design.The main work of this paper is as follows:(1)A compact filtering microstrip quasi-Yagi antenna operating at 2.4 GHz is proposed.The antenna consists of a dipole,a director,a reflector and a simple parasitic band,and is fed by a double-sided parallel-strip line(DSPSL).The antenna uses the reflector and the simple parasitic band placed between the dipole and the director to generate two symmetrical radiation nulls at the band-edges,thereby achieving a good bandpass filtering response.The proposed antenna has an out-of-band rejection level of about 20 d B,an impedance bandwidth of 30.4%,and an average gain of 5.7 d Bi.(2)A single-layer high-gain filtering microstrip patch antenna operating at 5.4 GHz is proposed.The antenna consists of a rectangular ring patch and a rectangular patch loaded with a pair of shorting vias,and is capacitively coupled by a T-shaped microstrip line.The antenna uses the rectangular ring patch operating in reshaped TM₂₁ mode and the rectangular patch placed inside the rectangular ring patch to generate two symmetrical radiation nulls at the band-edges,and uses the T-shaped feed line to further improve the out-of-band rejection level,thereby achieving a good bandpass filtering response.The proposed antenna has an out-of-band rejection level of over 16 d B,an impedance bandwidth of 9.2%and a gain of 8.6d Bi.(3)A planar 2×2 and 4×4 filtering microstrip patch antenna array operating at 5.2 GHz is proposed.The 2×2 array is composed of a driven patch and four identical parasitic patches.The driven patch is fed by a forked-microstrip-line-coupled slot,and the parasitic patches are capacitively coupled by the adjacent driven patch.The 2×2 array does not need to use an additional power dividing network or filtering antenna units,and only uses this specific feed scheme and patch topology to introduce radiation nulls on both sides of the passband,thereby achieving a good bandpass filtering response.The 4×4 array is composed of four 2×2 arrays,and is fed by only a four-way power dividing network.Both of the above two arrays have wide stopbands with an out-of-band rejection level of over 21 d B,and gains of 11.1 and 15.5d Bi,respectively.(4)A millimeter-wave broadband high-gain filtering microstrip patch antenna operating at26.9 GHz band is proposed.The antenna consists of four identical small microstrip patches each loaded with a shorting via and a simple parasitic strip,and is fed by a substrate-integrated waveguide(SIW)cavity working in TE₂₁₀ mode through a rectangular slot.The antenna uses the feeding SIW cavity and the parasitic strip placed between the small microstrip patches to generate a radiation null on each side of the passband,thereby achieving a good bandpass filtering response.The proposed antenna has an out-of-band rejection level of about 18 d B,an impedance bandwidth of 19.9%,and an average gain of 10.4 d Bi.