Novel microstrip directional band-pass/band-stop couplers and filters

Multifolded Bandwidth Branch Line Coupler With Filtering Characteristic Using Coupled Port Feeding

“…The coupler filter proposed by Uysal and Watkins [21,22], made by non-uniform transmission lines had a relative bandwidth of 18% but occupied an area of more than 2-wavelengths by 5-wavelengths at the center frequency. Therefore, small size and wide bandwidth are found in antenna and feeding network integration [23].…”

Novel microstrip multifunction directional couplers and filters for microwave and millimeter-wave applications

“…Manuscript received September 5, 1990;revised January 30, 1991. This work was supported by the Ministry of Defence, United Kingdom. Some experimental results have already been reported for a band-pass coupler designed and built on an alumina substrate [2]. Further experimental results for band-pass and periodic couplers will be given in the paper.…”

“…where e and o denote the even and odd modes, respectively, w 1 and w 2 are the lower and upper band edges of the passband, w , is the center frequency of the coupler, and Ue,o(w)l, Ue,O(w)z, and Ue,o(w)3 are the coupling responses in the respective bands. Ue,o(w)l and Ue,o(w)3 can be set to nonzero but very small values [2]. Throughout this paper, out-of-band couplings will be specified as zero.…”

“…Therefore, x/u,,. in 13 Although the phase velocities are compensated, i.e, even-mode phase velocities are equal to the odd-mode phase velocities, the design is kept general in the sense that an interdigitated section (nonuniform Lange [ 11) may be required in some cases. However, the length of the interdigitated section need not be a full h/4 [2].…”