The disclosed coupler is in a spiral form having approximately 11/4 turns and a length of just over 1/4 wavelength of a designed frequency. The coil includes an interdigitated section with two conductor portions for each conductor. In the overlapped turn portion, the inner conductors are narrower than the outer conductor. Further, conductor pads are disposed adjacent the coupler conductors for connection to associated couplers to vary the bandwidth of the coupler.