Novel Adjustable Microstrip Devices for Microwave Power Division and Impedance Matching

Abstract

This paper describes the design and implementation of novel adjustable microstrip devices which made possible new methods for phase shifting, variable power division and adjustable impedance matching in the 2.45 GHz ISM band. This novel technology is more affordable and simpler to develop than other state of the art technologies described in this paper. The development of this technology took place in the frame of a degree project on energetic applications of microwaves for Microbiotech SL (MBT). These devices have been used for the proper power delivery of microwave energy to a sample material provided by Microbiotech SL. The presence of this material can modify the impedance of the applicator according to the relative permittivity of the sample and therefore reduce the amount of microwave energy delivered by the applicator to the medium. The adjustable impedance matching network made possible the total transfer of electromagnetic energy, providing a simple and versatile method for reducing return losses to a minimum regardless of the load presented to the transmission line. In the other hand, the variable power divider addressed a more common problem in microwave heating such as power flow control. It supposes an affordable approach, which may be useful in some researching scenarios. The mechanism is based on the sliding of microstrip lines over the conductors of a circuit. The sliding is done in such way that the different available positions of the mobile structure control the phase shift along a certain transmission line of the circuit. The paper explains this mechanism and the implemented devices in depth; it describes its advantages and shows some examples of application.