Research And Design On Novel Filtering Power Dividers With Band-pass Response

Functional fusion devices such as filtering power dividers?FPDs?,which are characterized by miniaturization,low cost and high integration,have attracted more and more attention in recent years.Generally speaking,good isolation,excellent frequency selectivity,wide stopband rejection range and small size are desired for FPDs.In this thesis,some new types of FPDs are proposed and designed for demonstration.The main work includes the following aspects:1.A band-pass FPD with ultra-wide stopband and a band-pass FPD with wide stopband are proposed.These two FPD utilize two design schemes respectively.The first scheme realizes power division first and then filtering,and the second one realizes filtering first and then power division.The output port isolation feature of the former is better than that of the latter,but the size of the former is slightly larger than that of the latter.Finally,two examples of these FPDs were fabricated and measured.The center frequency of the first example is located at 3.11 GHz.It achieves harmonic suppression ability better than 20 dB,and 12 dB out-of-band suppression can reach4.8 f₀ and reach at20 f₀.The isolation is better than 20 dB within the 3 dB passband.The measured center frequency of the second example is located at 2.22 GHz.It achieves the at least 20 dB harmonic suppression up to 6.3f₀,and at least 17 dB isolation is achieve within broadband frequency range.2.A band-pass FPD with wide isolation range is proposed.Due to the symmetry of the structure,the FPD is divided into the even-mode circuit and the odd-mode circuit respectively.For this FPD,the key is to cascade the parallel-coupled microstrip line loaded with an open stub in the circuit.This parallel-coupled microstrip line loaded with an open stub can not only make the design more flexible,but also generate transmission zeros on both sides of the passband to improve frequency selectivity.For demonstration,an example was fabricated and measured,whose center frequency is 1.96 GHz.It can achieve at least 20 dB isolation within an ultra-wideband range,and harmonic suppression ability up to6.1 f₀.3.A new wideband Wilkinson band-pass FPD is proposed.Because of the symmetry of the structure,the odd-even mode analysis method is used to analyze it.The even-mode circuit determines the filtering response of the FPD.Then,the lumped-element equivalent circuit is obtained.According to the equivalent relation between the lumped-element value and the distributed-element ones,the structural parameters of the even-mode circuit can be determined.At the same time,by adjusting the resistance value of R,good isolation is achieved between output ports.In order to verify the design scheme,an example with the central frequency at 2.22 GHz was fabricated and measured.It achieves more than 24 dB out-of-band harmonic suppression up to6.1 f₀,and more than 20 dB broadband isolation from DC to 5.78GHz,also has a relative bandwidth of 88.8%.