On 30 MHz TE11 mode piston attenuator

A precision 30 MHz TE11 mode waveguide below cut-off piston attenuator has been designed for 0-100 dB attenuation range to serve as transfer standard of attenuation. The attenuator has been fabricated using a precision cylind rical copper waveguide and resonant inductive antennas with type-N connecto r at its input and output ports. The 30 MHz matched antennas have been inco rporated in the cylindrical waveguide in such a manner that one serves as f ixed transmitter and the other as moveable receiver for changing the attenu ation. A Faraday screen type mode filter has also been fabricated to attenu ate the amplitude of unwanted TM01 mode to an attenuation level of 60 dB. T he piston attenuator has approximately 20 dB insertion loss and has been ca librated in steps of 10 dB over the 0-60 dB range. The results were found t o lie within +/-0.01 dB/10 dB. (C) 2001 American Institute of Physics.