Abstract: A single in-plane orthogonal mode launcher for generating circularly polarized waves having both right and left hand senses is disclosed. A 90.degree. hybrid provides first and second signals to respective input ports of the launcher. First and second coplanar sets of probes are orthogonally disposed in a cylindrical housing and connected to the first and second ports, respectively. The first set of probes generates a first vector signal. The second set of probes generates a second vector signal which is 90.degree. to the first vector signal. Since the input signals to the first and second sets of probes are 90.degree. out of phase, circularly polarized waves are thus generated.