
689Planar Transmission Lines
This structure can be realised with ordinary microstrips by interleaving the
two arms, each of which consists of a number of conducting ngers. These
arms (with four, six or eight ngers) are arranged in an alternating manner.
The ngers of each arm are maintained at the same potential by connecting
them through bond wires, air bridges or underpasses. Figure 15.36 illustrates
such a coupler proposed by Julius Lange along with its frequency response.
15.10.5.3 Branch-Line Coupler
Coupled line and Lange couplers require narrow tracks and/or gaps and
thus, their realisation becomes a bit difcult. In the ap