Printed Ridge Gap Waveguide Antenna for Frequency Scanning Application

Abstract

With the advancement in modern communication systems, the demand for high frequency microwave devices is rapidly increasing. Traditional guiding structures such as microstrip and waveguides are being discarded due to certain disadvantages. For instance, the microstrip technology has higher losses and metallic waveguides are difficult to fabricate. Ridge Gap Waveguide (RGW) is a newly developed technology which is a solution to these problems. It has low losses and no requirement of electrical contacts as required in waveguides. The RGW confines the wave propagation to the ridge (guiding part) and suppresses leakage in all other regions. The region surrounding the ridge has two parallel surfaces. One is a perfect electric conductor (PEC) and the second is a perfect magnetic conductor (PMC). The ridge and the upper metallic plate realize the PEC surface between which the wave propagates. The bed of nails adjacent to ridge realize the PMC surface and provides a frequency stop band which is analyzed by its unit cell. Many RF and microwave are designed using this technology. One of the applications of designing antennas is considered in this thesis. The design of an H-plane horn antenna with array of long slots for broadside radiation is presented. The slots are kept at λg distance apart. The resultant radiation pattern consists of a main lobe with frequency scan capability and a grating lobe. Various designs are presented which use different slot configurations to reduce the radiation pattern to single lobe. A novel method for grating lobe suppression is used by placing Electromagnetic Band Gap (EBG) material in region of wave propagation under slots. The study opens the potential of EBG study in terms of radiation suppression in various antennas. The Printed Ridge Gap Waveguide (PRGW) is an alternate transformation of the RGW design concept which uses a printed circuit methodology as opposed to the metallic RGW structure. To take advantage of its benefits, a PRGW based long slot antenna array is also presented using printed horn-ridge in order to achieve a compact, low profile and cost friendly alternate. By achieving similar radiation performance as its RGW counterpart, the PRGW demonstrates its potential utilization in next generation communication systems due to its light weight, low cost, easy fabrication and self-packaging.