US4947178A — Scanning antenna

Claim 1

Independent Claim 148 words

A scanning antenna, which comprises: a plurality of concentric antenna elements arranged in resonant modes so that each resonates at a different azimuthal mode and is functional to produce a radiated circular polarized field, and phase shift means operatively connected to said plurality of antenna elements to effect phase shifts between azimuthal modes so as to steer a combined antenna beam consisting of the individual beams provided by each antenna element, said field for the nth mode of said elements being expressed by the relationships: E.sub.θ =f.sub.n (θ)e.sup.jnφ E.sub.φ =g.sub.n (θ)e.sup.jnφ where f n (θ) and g n (θ) are the θ-dependent expressions of the radiated field, whereby for n=1, the radiation peak is along the θ=0 direction and for n>1, the radiated field is conical in shape and produces a null along the θ=0 direction, and as n increases, the beam peak moves towards larger θ values.

Claim 2

Dependent Claim 148 words

A scanning antenna, which comprises: a plurality of concentric antenna elements arranged in resonant modes so that each resonates at a different azimuthal mode and is functional to produce a radiated circular polarized field, and phase shift means operatively connected to said plurality of antenna elements to effect phase shifts between azimuthal modes so as to steer a combined antenna beam consisting of the individual beams provided by each antenna element, said field for the nth mode of said elements being expressed by the relationships: E.sub.θ =f.sub.n (θ)e.sup.jnφ E.sub.φ =g.sub.n (θ)e.sup.jnφ where f n (θ) and g n (θ) are the θ-dependent expressions of the radiated field, whereby for n=1, the radiation peak is along the θ=0 direction and for n>1, the radiated field is conical in shape and produces a null along the θ=0 direction, and as n increases, the beam peak moves towards larger θ values.

Claim 3

Dependent Claim 135 words

A scanning antenna, which comprises: N antenna elements each of which resonates at a different azimuthal mode n and is functional to produce a radiated circular polarized field wherein said field for the nth mode of said elements is expressed by the relationships: E.sub.θ =f.sub.n (θ)e.sup.jnφ E.sub.φ =g.sub.n (θ)e.sup.jnφ and the total radiated field of the antenna is expressed by the relationships: ##EQU5## where f n (θ) and g n (θ) are the θ-independent expressions of radiated field, whereby for n=1, the radiation peak is along the θ=0 direction and for n>1, the radiated field is conical in shape and produces a null along the θ=0 direction, and as n increases, the beam peak moves towards larger θ values, and phase shift means operatively connected to said N antenna elements to steer a combined beam.

Claim 4

Dependent Claim 135 words

A scanning antenna, which comprises: N antenna elements each of which resonates at a different azimuthal mode n and is functional to produce a radiated circular polarized field wherein said field for the nth mode of said elements is expressed by the relationships: E.sub.θ =f.sub.n (θ)e.sup.jnφ E.sub.φ =g.sub.n (θ)e.sup.jnφ and the total radiated field of the antenna is expressed by the relationships: ##EQU5## where f n (θ) and g n (θ) are the θ-independent expressions of radiated field, whereby for n=1, the radiation peak is along the θ=0 direction and for n>1, the radiated field is conical in shape and produces a null along the θ=0 direction, and as n increases, the beam peak moves towards larger θ values, and phase shift means operatively connected to said N antenna elements to steer a combined beam.

Claim 5

Dependent Claim 95 words

The antenna of claim 2 wherein said antenna elements comprise a ground plane and a plurality of concentric circular microstrip patches, each arranged in the form of a resonant cavity and having effective radii a e corresponding to the relationship: ##EQU6## where K mn is the mth zero of the derivative of the Bessel function of order n and ε r is the relative-permitivity of the material filling a space under each microstrip patch and wherein said microstrip patches resonate at different azimuthal modes n=1,2,3, . . . N to generate their respective radiation patterns.

Claim 6

Dependent Claim 37 words

The antenna of claim 3 wherein each said microstrip patch is fed from feed excitation means at two different locations separated angularly by φ=π/2n and at phase quadrature to effect circular polarization of the individual directional beams.

Claim 7

Dependent Claim 70 words

The antenna of claim 2, wherein said plurality of antenna elements is provided by a plurality of concentric circular elements in the form of slots having a circumference which is an integer multiple, n=1,2,3, . . . N, of the frequency wavelength, so as to effect resonance in the azimuthal mode for each slot, thereby causing a phase progression of 2n radians for the resonant mode n, along the slot.

Claim 8

Dependent Claim 88 words

The antenna of claim 2 wherein said phase shift means introduces phase shifts between excitation of different modes to produce resulting field patterns represented by the relationships: ##EQU7## where δ n is the phase introduced at the excitation of each mode, whereby when φ=δ n /n, the array field maximizes and by employing phase shift values of θ, δ 2 , 2δ 2 , nδ 2 . . . at the excitation of each mode, the array beam can be scanned to the direction of φ=δ 2 .

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-08-06	1994-02-05	1994-08-07	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-08-06	1998-02-05	1998-08-07	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-08-06	2002-02-05	2002-08-07	$7700.00	Window Closed / Lapsed

Scanning antenna

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