Book excerpt: This book collects much of Helszajn's work (formerly, Heriot-Watt University) and includes closed-form and finite element calculations of the propagation constant, attenuation and mode spectrum for the ridge waveguide, and power-current and power-voltage definitions of impedance. Circular polarization is also treated. Propagation properties where the waveguide has a dielectric filler are calculated. The treatment is then extended to more complex designs, including quadruple ridge waveguides with and without a gyromagnetic filler. The text includes descriptions of many of the passive devices which can be realized using these waveguides, including isolators, phase shifters, and circulators. c. Book News Inc.