Page 9 - Complete Wireless Design
P. 9
Wireless Essentials
8 Chapter One
Figure 1.5 Proper winding of a toroidal inductor.
Figure 1.6 A toroid used to form
a transformer.
Figure 1.7 Impedance matching with a toroidal transformer.
Toroidal transformers, with the proper core material, are quite effective up
to 1 GHz as broadband transformers. As the broadband transformer increases
in frequency, however, the capacitance between the transformer’s windings
becomes more of a limiting factor. This internal capacitance will decrease the
transformer’s maximum operating frequency, since the signal to be trans-
formed will now simply pass through the transformer. However, this effect can
be minimized by choosing a high-permeability core, which will allow fewer
turns for the very same reactance, and thus permit less distributed capaci-
tance for higher-frequency operation.
Toroidal transformer design. For proper toroidal transformer operation, the
reactances of the primary and secondary windings must be 4 or more times
greater than the source and loads of the transformer at the lowest frequency
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
