MICROSTRIP COUPLED LINE BANDPASS FILTER WITH RADIAL STUBS FOR NARROW-BAND APPLICATIONS

Abstract

The necessity of creating channels by utilizing narrow-bands in high frequency regions is a
matter of concern for the next generation-oriented wireless communication systems. A microstrip bandpass
filter for narrow-band applications has been proposed in this article. Two coupled line filters with tapered
line resonators are loaded at the mid-points of two identical pairs of radial stubs. The scalable length of
microstrip lines to extend the radial stubs provides over 536 MHz shift of the resonant frequency with a
narrow-band at each perturbing step. The proposed filter has been designed on Taconic TLX-8 substrate with
0.5 mm thickness and its filtering parts occupy a nominal area of 131.09 mm2 without feedlines. The
fabricated filter exhibits nearly a 50 MHz pass-band at 6.428 GHz center frequency according to the
measurement. Steep response of this filter entirely attenuates the out-band signal which enables it to be
suitable for narrow-band applications in the higher frequency regions of C-band and ultra-wideband.