Novel Implementation of Broadband Detector

A new design and implementation of a diode based broadband detector module operating in excess of 40 GHz is presented. To accommodate the broadband nature, the external interface is coaxial while coplanar waveguide is used as the internal microwave transmission medium. A high performance coax to coplanar transition is incorporated into the design. By making broadband return loss measurements of prototype modules and establishing the dc characteristics of the selected diode, an equivalent circuit of the component can be deduced. This model is used to simulate the frequency response of the detector and provide the basis for optimisation. Measurements and simulated results in the range 10 MHz to 40 GHz are presented. Also shown is the means by which the frequency response can be optimised by varying a circuit parameter without any degradation to return loss.