Large diameter rf rotary coupler used with a passive rf sensor

Abstract

A rotary coupler comprises a statorhaving a first faceand a rotorhaving a second face, the first and second facesbeing spaced apart from and facing each other. A first electrically conducting trackis provided on the first faceof the statorwhich forms a transmission line and has spaced apart ends A, B and a second electrically conducting trackis provided on the second surfaceof the rotoralso forming a transmission line and having spaced apart ends C, D. One end A of the first track, in use, is connected to signal generating means and the other end B of the first track is connected to earth through a resistor substantially equal to the characteristic impedance of the transmission line. The first trackextends along a generally circular arc substantially around the first faceof the stator, the first trackhaving a length substantially equal to an integer number of wavelengths of the signal produced, in use, by the signal generating means. The second track () extends along a generally circular arc partially around the second faceof the rotor, the second trackhaving a length substantially equal to one quarter of the wavelength of the signal produced, in use, by the signal generating means.