Planar four-way power divider using impedance-transforming branch-line couplers

In a planar 4-way power divider consisting of three impedance-transforming branch-line couplers (BLC PD), the effects of interconnecting transmission lines have been investigated in terms of line length and characteristic impedance. When quarter-wavelength transmission lines are used for interconnection, the power division characteristics are improved in the sense of suitability for narrow-band communication systems because flatness and sharp attenuation are shown around the center frequency. Although Wilkinson power dividers have advantages of wide-band frequency characteristics, 4-way BLC PDs have been discussed in this paper because of the need for narrow-band communication systems with low spurious signals and low VSWR. The case in which a two or three quarter-wavelength interconnecting transmission line is used will be discussed in the near future.