PCB SUBSTRATES CHARATERISATION USING PRINTED STRUCTURES

Abstract

Growing user requirements for data exchange rates in telecommunication systems have resulted in
the active adoption of mm-band wavelengths and the intensive development of broadband communication
systems. Designing mm-wave microwave devices using CAD requires accurate frequency-dependent relative
permittivity data for the used substrate to reduce the device design time. This paper focuses on determining
the relative dielectric constant of the Rogers 3003G2 substrate in the mm-wavelength range. Both
non-resonant and resonant methods were used to find the dielectric permittivity. The automation of the
measurement data processing was achieved by using the developed script in MATLAB. The relative permittivity
of the substrate in the band 1-42 GHz was determined by applying the phase difference method,
using two microstrip lines of different lengths. SIW resonators with waveguide excitation were developed
to avoid using a probe station with fragile probes for S-parameter measurements in the mm-length range.
The relative permittivity of the studied substrate in the 60-170 GHz range was found using three prototype
multi-mode SIW resonators. A set of single-mode SIW resonators with different waveguide excitation coupling
was produced to avoid ambiguity in longitudinal mode number determination in multi-mode SIW
resonators. Several loaded resonant frequencies were obtained by varying the length of SIW-resonators'
excitation slots to calculate the unloaded resonant frequency used to find the relative dielectric permittivity
of the substrate. Recommendations for developing SIW resonators for the determination of dielectric
properties of the substrates are given in the conclusion section.