As is known in the art, one type of analog phase shifter includes a branchline coupler. One such branchline coupler, sometimes also referred to as a reflective coupler or a shunt hybrid combiner, Quadrature Hybrid, having an input port (Input 1), a pair of output ports (Output 2, Output 3) and an isolated port (Isolate 4), is shown in FIG. 1 to include a pair of main transmission lines and a pair of shunt transmission lines. One analog phase shifter, (FIG. 2) that includes a branchline coupler having a pair of phase adjusting sections is described in a paper entitled “Integral analysis of hybrid coupler semiconductor phase shifters” by Kori et al, IEE Proceedings, vol. 134, Pt.H. No. 2. April 1987.
One technique used to adjust phase shift of the branchline coupler type phase shifter is to connect a phase adjusting section connected to each one of the pair of shunt transmission lines as described in a paper entitled “A Low-Loss Voltage-Controlled Analog Phase-Shifter Using Branchline Coupler and Varactor Diodes” by Gupta et al., (Gupta, Nishant, Raghuvir Tomar, and Prakash Bhartia. “A low-loss voltage-controlled analog phase-shifter using branchline coupler and varactor diodes.” Microwave and Millimeter Wave Technology, 2007. ICMMT'07. International Conference on. IEEE, 2007). In that paper a pair of varactor diodes is controlled by voltages to adjust the phase shift provided by the phase shifter. Another branchline coupler type phase shifter having a phase adjusting section connected to each one of the pair of shunt transmission lines is shown in FIG. 3A. In that paper the phase adjusting sections each includes a pair of conductors separated one from and the other; one of the conductors being connected to a ground plane conductor on the bottom of a substrate by ground vias (FIGS. 3A and 3B). The two conductors are connected by a series of bridging, spaced bond wires, as shown. With an input signal applied at an input the phase at an output is measured and the bond wires are removed one at a time, as shown in FIG. 3B, to thereby change the electrical length of the path through the phase adjusting sections to ground until the desired phase shift is obtained; FIG. 3B showing several of the bond wires removed from the branchline coupler type phase shifter of FIG. 3A.