Filter And Antenna Fusion Design

Regarding the fusion design of the filter and the antenna,there are mainly three types known at present: the first one is a filter antenna,and the filtering function is integrated into the antenna.The antenna is normally radiated in the passband,and has good radiation suppression characteristics outside the band,and exhibits steep edge roll-off characteristics from both the reflection coefficient and the gain curve of the antenna.The second type is a duplex antenna,which combines the function of the duplexer with the antenna.Compared with the filter antenna,the frequency division function is further realized.The last is a filter and antenna function reconfigurable device that can switch between the filter and antenna functions in the same device or both.In this paper,the above three methods of fusion design are deeply studied,and a new fusion design method is proposed.The specific research contents are as follows:1.A broadband filter dipole antenna was designed.By analyzing and utilizing the inherent characteristics of the radiating arms and the balun of the dipole antenna,three radiation zeros are generated outside the passband,achieving good out-of-band rejection,thereby the filtering function is implemented without adding any parasitic structure and opening any slot on the radiator.2.For the first time,a high-gain dual-polarization duplex antenna based on duplex balun was proposed.The duplex balun combines a low-pass filter with a high-pass filter to enable both duplex and balun functions.The duplex balun fed antenna can achieve both frequency division and antenna radiation without adding extra size and loss.3.The patch antenna and the filter are combined to realize the switching between the filter and the antenna.By using a cross-shaped feeder,the filter or antenna operating mode of the device can be excited in different frequency bands.In the antenna working mode,the crossshaped feeder only acts as a feeding force,and the patch radiates normally;in the filter working mode,the resonance of the cross-shaped feeder and the underlying short-circuit branch line realizes the filter function,and at this time,the patch acts as the ground of filter and is in a nonradiative state.