Investigation Of Novel RF Components And Applications Based On Composite Right/Left-Handed Transmission Lines

The composite right/left-handed transmission lines(CRLH TLs)are artificial transmissionlines They possess both left-handed and right handed characteristics at the same time The lefthanded characteristics dominate the lower~equency band while the right handed characteristicsdominate the higher~equency region While operate at lower band，the phase velocity andgroup velocity aJ’e anti-parallel compared to the parallel velocities at higher frequencies Thedispersion relations of the CRLH TLs reveal that the CRLH TLs are extremely dispersive atlower frequencies and are much less dispersive at high frequencies The CRLH TLs posses otherdistinctive characteristics as well Their characteristic impedaaces and phase shifts along theCRLH TLs can be controlled by the element values oftheir constructing unit cells The numberof the cells can be use to tune the phase shifts as well In addition，the phase relations of theCRLH TLs are non--linear in the lower frequency band while they are quasi--linear in the higher~equency band Due to these characteristics the CRLH TLs are important for microwave circuitsand antennas By using them，one can achieve arbitrary frequency ratio dual band components，which includes Wilkinson power dividers with arbitrary~equency ratios and power-splittingratios They can also be used to implement dual~equency dual circularly polarized aatennasand other compact devicesThe thesis studied the main characteristics and determination methods ofthe CRLH TLsIt also conducted analysis on bandwidth expansion method ofthe CRLH TL constructed withinterdigital capacitors(IDCs)The thesis also provided the applications of the CRLH TLs individers and circularly polarized antenna The main contribution ofthis thesis are as follows(1)、Proposed and implemented a wide band CRLH TL by eliminate the high-frequency reso-nance ofthe IDCs in the CRLH TL The high~equency resonances ofthe IDCs are removedby connecting the finger tips at either side ofthe IDCs through vias and metal strips in theslots on the ground plaae An accurate circuit model and extraction method for the mod-ified IDC is proposed The circuit model can be used to determine the left/right-handedcharacteristic frequency region when the modified IDC is used to implement CRLH TLsThe circuit model can accelerate the simulation time with much less computing resources Electromagnetic simulation，measurement mad circuit simulation show-that the circuit modeland the extraction method are reliable mad the frequency regions are correctly predicted bythe circuit model(2)Proposed and implemented two dual~equency Wilkinson power dividers with the samecontrollable frequency ratio and different power splitting ratios by using CRLH TLs，whichare constructed with IDCs mad stub inductors Theory analysis show-that the90°phaseshift along the two arms ofthe proposed divider allow-the divider split power efficiently andensure perfect match at all ports and perfect isolation between the output ports Theory anal-ysis also reveals that theπ-shaped unit cell has the same dispersion relation and bandwidthas that of the T-shaped cell As theπ-shaped cell has shorter electrical length．thereforeit is easier to meet the effective homogeneous conditionθ�'0when the both cells areimplemented with IDCs and shorted stubs The element values in the cell control the phaseshift and characteristic impedance ofthe CRLH TL，which therefore controls the~equencyratio and power splitting ratio ofthe divider．Two divider with the same frequency ratio anddifferent spitting ratios are designed and tested to verify the theory analysis Simulation andmeasurement results show-the two dividers w-ork as expected which verifies the theory(3)Proposed a novel dual~equency dual circularly polarized antenna with controllable fre-quency ratio The antenna has two stacked radiating elements excited by two capacitivepatches，which connected to the two ports of a dual~equency feeding network The feed-ing network provides equal power with quadrature phase to the two output ports The new-feeding scheme allow-easy design of dual~equency matennas having different circular po-larizations at the two operating frequencies A dual frequency dual circularly polarized an-tenna is designed，fabricated and measured，which works well at the up-link and down-linkfrequencies ofthe Chinese Beidou satellite navigation system(4)Proposed and implemented a new-balmaced CRLH TL based on double sided parallel striplines(DSPSLs)The new-CRLH TL has two identical parallel strips printed on the top madbottom sides of the substrate Theory analysis based on the circuit model show-that thephase propagates backwards along the transmission line in the lower~equency region and forwards along the transmission line in the higher frequency region With regards to theforward group velocity propagation direction．the new trmasmission line is a CRLH TL‘Ibverify the new balanced CRLH TL，a dual frequency Wilkinson power divider is designedand implemented with the CRLH TL The simulation and measurement results show thatthe divider can work efficiently at the two working frequencies as expected The power issplit equally to the two output ports，all the ports are matched and the isolation betweenthe two output ports are quite good Judging with the performances ofthe dividec the newbalanced CRLH TL provide90°and+90°phase shifts to the output ports at the lowerand higher working frequencies，respectively The results also verify that the characteristicimpedances ofthe two CRLH TL in the divider are controlled by the element values oftheconstructing unit cells...