Very compact low pass and bandpass filters using uniplanar structures

A new design procedure of low pass and bandpass filters using hybrid uniplanar structures is presented. A compact topology of a quasi lumped element low pass filter has been designed and tested. For this circuit, a high rejection level of the spurious responses is obtained: a very sharp slope response above the cut-off frequency (3 GHZ) and an attenuation lower than 20 dB up to 15 GHz are observed. A broadband bandpass filter has also been investigated using series and shunt stub elements. A flat insertion response with a maximum attenuation of 0.6 dB and -15 dB return losses are observed in a Large frequency range.