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传统基于变容二极管的双频电可调滤波器由于外部容值的加入,该类滤波器的插损变大,同时相对带宽锐减。基于多模谐振器结构,提出了一种新型的工作频段独立、电可调的双频带通滤波器。该滤波器由短路枝节线加载谐振器和一对1/4波长谐振器组成。在各自的谐振器末端加载带有变容二极管的外部偏置电路,1/4波长谐振器构成第一通带,短路枝节线加载谐振器构成第二通带,两通带之间互不干扰,单独调节。应用奇偶模分析法及调节耦合间距的方法,确保双通带均出现两个极点,保证其带宽的稳定性。该电可调滤波器第一通带可调范围为0.7~0.85 GHz,第二通带可调范围为0.9~1.05 GHz,同时双频带的相对带宽基本保持在10%以上,较以往的双频电可调滤波器,该款滤波器的相对带宽有了较为明显的提升。
Conventional varactor-based dual-frequency tunable filter Due to the external capacitance, the insertion loss of the filter becomes larger and the relative bandwidth decreases sharply. Based on the structure of multi-mode resonator, a new type of dual-band band-pass filter with independent and electrically adjustable working frequency band is proposed. This filter consists of a short-circuit stub line load resonator and a pair of ¼ wavelength resonators. An external bias circuit with a varactor diode is loaded at the end of each resonator, a ¼ wavelength resonator forms a first pass band, and a shorted stub line load resonator forms a second pass band with no interference between the two pass bands , Adjusted separately. Using the method of odd and even mode analysis and the method of adjusting the coupling distance, two poles are ensured in the double passband to ensure the stability of the bandwidth. The tunable range of the first passband of the electrically tunable filter is 0.7-0.85 GHz and the second passband is tunable range of 0.9-1.05 GHz while the relative bandwidth of the dual band basically stays above 10% Electrically tunable filter, the relative bandwidth of the filter has been significantly improved.