A novel slot-line filter with stop-band up to 30 GHz is proposed in this paper, and the theoretical analysis is illustrated in detail. This filter is designed on a Rogers RT/duroid 5870 substrate. The rectangular micro-strips can generate transmission zero to give a great suppression for the spurious response around 5f0 while the L slot lines can create transmission zeros to suppress the spurious response around 7f0, 9f0 and 11f0. f0 is 2.43 GHz in this paper and represents the center frequency of the main passband. The compact size of this novel filter is 23.7 mm * 14.725 mm (0.152λ * 0.103λ (λ is the working wavelength of this filter)). Besides, the external quality factor of this filter can be as high as about 29.6. To demonstrate the transmission function, the compact filter has been fabricated and the measured results show the feasibility of this structure.
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