| 摘要 |
Disclosed are microstrip resonators and bandpass filters using the same. The bandpass filters of the present invention include an input, an output and multiple resonators coupled between the input and the output. A first resonator coupled in series between the input and the output includes a first line conductor having first and second ends and a second line conductor having first and second ends. The first and second line conductors are positioned relative to one another such that the second end of the first line conductor is connected to the second end of the second line conductor, forming a first angle of the first resonator between the first and second line conductors. The first angle of the first resonator is substantially less than 180 degrees so that a physical length of the resonator, taken in a direction from the input to the output, is less than an electrical length of the first resonator. The first open ended line conductor connected to the second ends of the first and second line conductors at the point where the resonator is bent. The length of the open ended line conductor is equal to a guided quarter-wavelength of a second (or third, etc.) harmonic of a center frequency of a passband of the filter. The bandpass filter of the present invention exhibits better attenuation for second and higher harmonics.
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