Design and Implementation of a Low Cost High Bandwidth Sampling Bridge

Abstract

Research involving high bandwidth signals in GHz range is limited in Kenyan Universities due to lack of high bandwidth measurement equipment such as sampling oscilloscopes and spectrum analyzers among others. The cost of these instruments from international vendors is very high and hence there is need to come up with low- cost alternatives in order to promote and enhance research in our local institutions. In this work the concept of high frequency sampling bridge is to be developed for high frequency measurements. Various sampling techniques and architectures have been studied and implemented with the idea of improving the bandwidth, sampling rate, rise time, bridge circuit design, reduction of noise and distortion, minimizing aperture errors, as well as reducing the overall design cost of the bridge. This work employs the Equivalent Time Sampling Technique (ETST) in order to minimize the cost of electronic devices at the output stage. The design is implemented on monolithic GaAs which generates fast pulses for sampling, Schottky diodes which are well suited for high frequency operations and SiGe HBT technology which require small implementation area thus compact light weight and low cost device. The implemented system is capable of sampling picoseconds signals at analog measurement bandwidth of 6 GHz or above with a rise time in the order of 100 ps with low noise and low distortion.