Since the difficulties in tuning the transmission zero point of microwave cavity filter, one enhancement capacitive cross-coupling structure is proposed. This structure is implemented by adding a new tap screw to the centre of supporting Teflon piece of cross coupling dumpbell. Thus a new distributed variable capacitor is generated. The capacitive cross coupling factor is achieved greater value, so the slope of cavity filter is improved. More over, the position of transmission zero point can be tuned after assembly by varying the length of the screw. The simulation results show that cross coupling bandwidth can be changed about 4.6 MHz when the screw high changing 7mm. This new proposed structure is applied to a microwave cavity filter in eNodeB for Band 3 - Long Term Evolution (LTE) application to verify the effectiveness. The filter is made up of 10 coaxial resonator cavities with two new capacitive cross - couplings. The simulation results of filter fully meets specification requirements including band of 1805 to 1880 MHz, return loss below -12.7dB, ripple of 0.1dB and insertion loss below 0.2dB. The signal rejection at frequencies below 20MHz bandwidth is improved of 1dB. More over, this structure can be developed not only in Band 3 but also in different bands when using resonator cavity filter type.
