| The current trend towards total circuit integration where the antenna, R.F., and baseband circuitry are incorporated on a single substrate precludes the use of measurement systems such as the network analyser since there are no suitable R.F. input or output ports.This investigation has addressed the problem of performing 'in-situ' circuit measurements on millimetre wave printed circuits using a small, capacitively coupled probe. The technique is applicable to any 'open' printed circuit geometry, and does not require any physical connection to the circuit under test.A computer controlled measurement system is described which allows either the mode of excitation of a circuit element to be determined from the EZ distribution on its top surface, or else perform circuit measurements on individual elements using a technique analogous to the waveguide slotted line.The suitability of various probe geometries for this purpose is assessed, and sources of measurement error inherent in the probe designs employed are described. Emphasis has been placed on the characterization of integrated antenna elements and their associated feed network. Examples pertaining to microstrip patch antennas, the coplanar strip vee, and the tapered slotline antenna are presented. |
