Internal R&D

It has ever since the beginning of the 1990’s possible for P O Risman to pursue research projects as an independent researcher – gentleman  scientist –  financed by his consulting and patent royalties.  Some of these studies are of a basic nature and have no immediate industrial use, while others (mainly on mode theory, diffraction, and surface waves) form a basis for competitive consulting and inventions, and in 2015 led to his part-time employment as adjunct professor at the Mälardalen University  (MDH) in Sweden.


From the beginning of the 1990’s,  theoretical work in mode and diffraction theory was carried out. It resulted in a number of “chapters”, only some of which has hitherto been published,  in part and then as conference papers.

Some core parts were presented at an AMPERE conference when some secrecy agreements had lapsed. They deal with the disparate "states-of-the-art" in cavity/applicator mode theory The presented paper with colour introduced is in the version that can be downloaded here (F, 300 dpi; 5 MB). At the same conference, a poster with a description of some of the complex cavity theory and practically relevant examples was also given and is available here (1,2 MB); it is an excerpt from unpublished text by P O Risman.

From 1998, access to the then quantum-leap FDTD numerical microwave modelling software by QWED in Poland led to increasingly advanced projects. These were both internal and for clients, and many of them had not been possible to pursue – or had been too risky to initiate – were it not for the possibilities to SEE AND FOLLOW  the fields, particularly for mode ore diffraction studies.   

In 1999, some important aspects of microwave oven cavity modes and on the concept of microwave penetration depths in presentations by P O Risman at an IMPI course. They have astonishingly not yet been brought up in the technical or scientific literature in the subject area. Click on the bolded text above  to download a copy.

In 2005 and 2006 interest was focussed on new systems for accurate dielectric measurements. The dual-frequency measurement applicator was designed.  An example of instruction sheet is given here (290kB).

The project on improved data for pure liquid water was concluded in 2006. Data from –15 °C to +40 °C were presented at the 6th ISEMA conference in Weimar May-June 2005. A full paper was published in the April, 2007 issue of the IOP journal. Algorithms are given in the section Technical References. Selections of suitable reference liquids were also made, and three of them were measured with high precision. Data are given in the same section.

During 2008, four chapters were authored for a book to be published in 2009 by Woodhead Publishing Ltd: Development of packaging and products for use in microwave ovens. edited by M.W Lorence and P.S.Pesheck. The chapters deal with  dielectric measurement methods, dielectric data including mixture formulas, modelling of susceptors and ameliorators – and advanced topics on heating unevenness. In that chapter, two cavity-bound and twelve (!) load-dependent factors are described. One of these is the very interesting burnt stripe effect.

 Risman retained the copyright to the chapters written by him. As an example. the chapter on heating unevenness can be downloaded HERE (15 MB) 


Many papers authored by P O Risman have been published in the Journal of Microwave Power (and Electromagnetic Energy). There has been a major effort by the journal to provide internet access to all published journal issues since 1966. P O Risman participates in this. He has for example recently scanned and provided all the 1966–67 issues, and several others. See the JMPEE website


Information on patents: Click on  Patents.