US 6,154,180 A · Multiband antennas

Abstract

A parasitic antenna array (Yagi-Uda or loop type) for multiple frequency bands has its driven and parasitic elements interlaced on a single support boom. In a first aspect of the invention, series resonant circuits are located in one or more parasitic director elements in order to minimize the deleterious mutual coupling effect between directors of different frequency bands. In a second aspect of the invention, an inductance is placed across the feed point of the driven element of one or more non-selected frequency bands in order to minimize the bandwidth narrowing effect of closely-spaced driven elements and to provide a desired feed point impedance at the driven element of the selected frequency band. Although the two aspects of the invention may be used without one another, they are advantageously employed together. In addition, the second aspect of the invention may be applied to closely-spaced driven elements that are not part of a parasitic array.

Claims22

Dependent claims

A parasitic antenna array for at least two frequency bands, comprising

one or more driven elements for said at least two frequency bands,
separate parasitic elements for each of said at least two frequency bands, each of said separate parasitic elements operative as a director on one of said at least two frequency bands, respectively, at least the parasitic element or elements for the frequency band or bands other than the highest frequency band having at least one series resonant circuit in each half of the respective parasitic element when the parasitic element is a yagi element and including a series resonant circuit in each quarter of the parasitic element when the parasitic element is a loop element, the resonant circuit having a resonant frequency substantially in the frequency band in which the respective parasitic element functions as a director, thereby acting as a short circuit in said frequency band and as an open circuit in the other frequency band or bands, the series resonant circuits being located at positions substantially symmetrically spaced along the element such that for the frequency band or frequency bands other than the frequency band in which the parasitic element functions as a director, the parasitic element is electrically broken into portions that reduce the effect of the parasitic element on the radiation pattern of the antenna array in said other frequency band or bands.

A parasitic antenna array for at least two frequency bands, comprising

separate, closely-spaced, elements for each of said at least two frequency bands, each of said separate elements operative as a driven element on one of said at least two frequency bands, respectively,
a transmission feed line coupled to each of said elements, respectively,
a switch, said switch coupling an input for a further transmission feed line to a selected one of said transmission feed lines and shorting at least one of the non-selected transmission feed lines,
said at least one of the non-selected transmission feed lines having a length such that, when shorted, causes the element coupled to the selected transmission feed line to have a predetermined impedance and to have a wider bandwidth than if the element having the shorted transmission line, or the elements having the shorted transmission lines, did not have its transmission line shorted or their transmission lines shorted, respectively, and
separate parasitic elements for each of said at least two frequency bands, each of said separate parasitic elements operative as a director on one of said at least two frequency bands, respectively, at least the parasitic element or elements for the frequency band or bands other than the highest frequency band including at least one series resonant circuit in each half of the respective parasitic element when the parasitic element is a yagi element and including a series resonant circuit in each quarter of the parasitic element when the parasitic element is a loop element, the resonant circuit having a resonant frequency substantially in the frequency band in which the respective parasitic element functions as a director, thereby acting as a short circuit in said frequency band and as an open circuit in the other frequency band or bands, the series resonant circuits being located at positions substantially symmetrically spaced along the element such that for the frequency band or frequency bands other than the frequency band in which the parasitic element functions as a director, the parasitic element is electrically broken into portions that reduce the effect of the parasitic element on the radiation pattern of the antenna array in said other frequency band or bands.

2 more elements

A parasitic antenna array having three elements on each of three frequency bands, comprising

separate, closely-spaced, elements for each of said three frequency bands, each of said separate elements operative as a driven element on one of said three frequency bands, respectively,
a transmission feed line coupled to each of said elements, respectively,
a switch, said switch coupling an input for a further transmission feed line to a selected one of said transmission feed lines and shorting at least one of the non-selected transmission feed lines,
said at least one of the non-selected transmission feed lines having a length such that, when shorted, causes the element coupled to the selected transmission feed line to have a predetermined impedance and to have a wider bandwidth than if the element having the shorted transmission line, or the elements having the shorted transmission lines, did not have its transmission line shorted or their transmission lines shorted, respectively, and
a first set of separate parasitic elements for each of said three frequency bands, each of said separate parasitic elements operative as a director on one of said three frequency bands, respectively, the parasitic element for the frequency bands other than the highest frequency band including at least one series resonant circuit in each half of the respective parasitic element when the parasitic element is a yagi element and including a series resonant circuit in each quarter of the parasitic element when the parasitic element is a loop element, the resonant circuit having a resonant frequency substantially in the frequency band in which the respective parasitic element functions as a director, thereby acting as a short circuit in said frequency band and as an open circuit in the other frequency bands, the series resonant circuits being located at positions substantially symmetrically spaced along the element such that for frequency bands other than the frequency band in which the parasitic element functions as a director, the parasitic element is electrically broken into portions that reduce the effect of the parasitic element on the radiation pattern of the antenna array in said other frequency band or bands, and
a second set of separate parasitic elements for each of said three frequency bands, each of said separate parasitic elements operative as a reflector on one of said three frequency bands, respectively.

3 more elements

Dependencies are inferred from the claim text.

Multiband antennas

Life of this patent

Multiband antennas

Life of this patent

Abstract

Claims22