Wideband Bandpass Filter Design with Parallel Three-line Coupled Microstrips and the Suppression of Spurious Responses

• Main Authors: Wei-Cheng Lee, 李偉乘
• Other Authors: Jen-Tsai Kuo
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/66117929017468417691

碩士 === 國立交通大學 === 電信工程系 === 90 === Bandpass filters are designed based on parallel coupled three-line microstrip structure. The relation between the circuit parameters of a three-line coupled microstrip section and an admittance inverter is established. A design graph for substrate with Er=2.2 is provided. Two Chebyshev filters, of order 2 and 1dB passband ripple, with fractional bandwidth 40% and 60% are fabricated and measrued. Good agreement between prediction and measurement is obtained. Line corrugation is introduced to the three-line microstrip wideband bandpass filters for suppressing the spurious response at the second harmonic (2fo). The corrugation is used to equalize the phase velocities in the propagation direction of the two activated eigen-modes. Measured results show that a suppression better than —50dB can be achieved.