Design Of Differential Antennas And Power Dividers

In modern wireless communication systems,as the data transmission rate increases,crosstalk and electromagnetic interference problems become more and more serious.Crosstalk is caused by the coupling of different signals on adjacent transmission lines within the system.Electromagnetic interference is due to the coupling of external energy generated by other electronic devices to the data lines of its own device.Both of these conditions can cause confusion on the device and cause the system to fail to work properly.Differential signal circuits used to be applied to low frequency analog circuits and electronic devices to overcome noise interference.However,as the operating frequency increases,the data transfer rate between channels increases,posing a higher challenge to the design of differential microwave circuits.Differential devices are the basic units of low-noise systems,such as differential power dividers,differential filters,differential mixers,differential antennas,etc.,and they all have symmetric features physically.These devices have high immunity to noise,high common-mode rejection,and low spurious emissions.This thesis firstly analyzes the structure and basic characteristics of the slotline and the microstrip-to-slotline conversion structure,and proposes a differential reconfigurable bandpass filter based on slotline resonators afterwards.Finally,based on the above research,a broadband differential power divider and wideband differential antennas are designed.The main content of this thesis is as follows:In this thesis,the characteristics of the slotline and the slotline resonator are studied first,and the microstrip line to slotline conversion structure is proposed.Based on this,a differential reconfigurable band-pass filter is designed.A variable capacitance diode is embedded in the stub-loaded slotline resonator(SLSR).By changing the control voltage of the varactor diode,the center frequency of the filter can be electrically controlled within 3.09 GHz to 3.6GHz.Then,based on the microstripline-to-slotline conversion structure,this thesis designs a compact ultra-wideband differential equal power divider.The impedance bandwidth(differential mode)of this power divider ranges from 1.8GHz to 11.5GHz.By placing two quarter-wavelength short-circuited stubs beside the microstrip line,one sharp differential mode notched band covering from 5.8 GHz to 5.9 GHz is achieved.Finally,this thesis designs a compact microstrip ultra-wideband differential quasi-yagi antenna.The differential impedance bandwidth of the designed antenna is from 3.8 GHz to 9.5 GHz;in addition,the antenna can also achieve a sharp reconfigurable notched band(5.6GHz to 6.7 GHz),which can effectively suppress the interference in this band.To validate the design theory,the proposed antenna is manufactured and tested and the measured results are in good agreement with the simulation ones.