Picosecond time-domain characterization of CPW bends using a photoconductive near-field mapping probe

Propagation and reflection characteristics of right-angle coplanar waveguid e (CPW) bends were measured using a novel photoconductive near-field probe with picosecond temporal resolution and mum spatial resolution. The probe c an measure the transverse electric-field components existing over devices u nder test. Time-varying transverse electric field maps for different CPW be nding structures were acquired by varying the probe position. The CSL mode generation and a difference in flight time of propagating pulses on two slo ts of the CPW bends were observed. Further, it was found that there exists a considerable unexpected pulse caused by the bent line structure, which ha s opposite polarity to the input pulse and exists only at the inner ground plane. The undesirable phenomena originated from the bend discontinuity wer e adequately reduced by bend smoothing techniques.