Abstract-A novel bandpass filter design method of achieving different selectivity based on E-shaped dual-mode resonator is presented. The characteristic of the E-shaped dual-mode resonator is investigated. The technique of utilizing capacitive and inductive input-output cross-coupling to generate two adjustable transmission zeros at stopband is explored intensively. Advantages of this type of filter are not only its dual-mode resonator and miniaturization, but also its controllable transmission zeros. The coupling scheme is presented to model the operations of these filters. Four dual-mode microstrip BPFs have been designed, fabricated, and measured. Both the simulated and measured results are presented. The exemplary filters verify the feasibility of the new design method.
A novel hexagonal dual-mode inductance-loaded filter with four transmission zeros is presented. The technique of utilising inductive sourceload coupling introduces four transmission zeros to provide high selectivity. Then, a bandpass filter is designed, fabricated and tested. Both simulated and measured results are presented.
A positive phase-velocity tapering of 1.5 octave broadband helix traveling-wave tubes for efficiency enhancement, where the phase velocity is linearly increased in the output section, was studied by using the one-dimensional nonlinear theory. At high frequencies, the electromagnetic wave in the positively tapered section traps the fastest electrons in the decelerating electric field, extracting more energy from the electron beam. At low frequencies, a decreased velocity difference between the electron beam and the electromagnetic wave destroys the phase condition for second-harmonic generation, retaining fundamental wave efficiency as well as reducing its second-harmonic power.
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