For many antenna applications it is desirable to have a single antenna that will function on two or more frequency bands. Many techniques exist which enable double or multiple resonances from a single antenna. They include multiple elements fed in parallel, single elements with wave traps which allow certain frequencies to use only a portion of the element, and parasitic coupled elements.
Parasitic elements typically have one driven element, for example a simple half wave length dipole antenna at the lowest frequency, and secondary elements which are resonant ½ wavelengths at different frequencies, positioned near the first element. Through inductive and/or capacitive coupling, the responses of the secondary elements can be seen at the first element's feed point. With proper adjustment of the lengths and the spacing of the element an effective multi-band antenna can be realized.
It is an object of the present invention to provide an efficient multi-band antenna, that is relatively simple in construction and easy to manufacture.