Abstract
low pass filters with ultra-wide band rejection and compact size by using radial stub and proposed radial stub with transformer are investigated. The stopband skirt selectivity and stopband width of lowpass filter are improved through generation of multiple zero points using proposed new structures. The implemented low pass filters with cutoff frequency f(c) of 3GHz demonstrates stopband rejection more than 35dB up to 8f(c) and insertion loss better than 1 dB. The size of the low pass filters are only 0.4 lambda g x 0.155 lambda g and 0.31 lambda g x 0.24 lambda g, (lambda g is the guide wavelength at center cutoff frequency).