The design of 5 dB attenuator in coplanar waveguide for DC to 67 GHz

Resistive attenuator is used to reduce incident RF power and for impedance matching due to its absorptive and dissipative nature. A resistive 5 dB attenuator has been designed for an electromechanically selectable attenuators module. The electromechanical switch structure necessitates the attenuator to be designed to approximate a coplanar waveguide. As the attenuator has to work up to 67 GHz, parasitics of the attenuator circuit and the peripheral mechanical components had to be dealt with. Three dimensional EM field simulations were performed to understand the effect of the parasitics by monitoring the field patterns. Modification to the coplanar waveguide structure was introduced to overcome the parasitic degradation. A π topology 5 dB attenuator has been successfully developed with attenuation flatness of ±0.25 dB and return loss less than -10dB up to 67 GHz.