Null control of multiple beam antenna

Claim 2

An antenna assembly comprising: a plurality of antenna elements for radiating and receiving electromagnetic energy; a single processing means, such as a transmitter or receiver, for processing signals acted upon by said antenna assembly; a beam forming network including a plurality of ports associated with said antenna elements and phase rotation means coupled between said processing means and said antenna elements for producing a substantially frequency independent null by adjusting the phase of a signal applied to each of said antenna elements so that with respect to a null point there are equidistant rings of beams with equal amplitude and phase increments of ##EQU3## wherein N R is the number of beams per equidistant ring set and M is an integer; said beam forming network including variable power divider means for splitting and combining power two ways in any ratio; said beam forming network including variable phase shifter means coupled to said plurality of ports for adjusting the phase of the signal exciting each one of said plurality of ports associated with said antenna elements; said variable phase shifter means being adapted to adjust the phase of adjacent beams in an equidistant ring with respect to the null point so that the phase difference between adjacent beams is ##EQU4## the phase of the signal applied to one of said antenna elements being equal to the amount of rotation of the center of the antenna element about the null with respect to a reference line; and said variable power divider means being adapted to adjust the amplitude of phasors associated with the beams in an equidistant ring so that there are sequentially phased signal phasors adding to zero amplitude to form a null and any constituent beam sidelobe frequency changes remain balanced at the intended null direction thus cancelling out and maintaining an advantageously deep null in spite of a frequency change or increased bandwidth of a given signal.

Claim 3

An antenna assembly as recited in claim 1 further comprising: a beam deletion means coupled to said antenna elements for turning off a narrow beam at the null point.

Claim 4

An antenna assembly as recited in claim 1 further comprising: a beam subtraction means coupled to said antenna elements for adjusting the phase and magnitude of a signal at the null to eliminate any residual signal for at least one signal frequency applied to said antenna elements

Claim 5

An antenna assembly as recited in claim 1 wherein said antenna elements are arranged in concentric circles around the null.

Claim 6

An antenna assembly as recited in claim 4 wherein the null is coincident with one of said antenna elements.

Claim 7

An antenna assembly as recited in claim 4 wherein the null is positioned between two of said antenna elements.

Claim 8

An antenna assembly as recited in claim 1 wherein said phase rotation means includes means for establishing a plurality of nulls, with arbitrary locations, the relative phases of the beams around each of the nulls being changed by equal increments.

Claim 9

An antenna assembly as recited in claim 1 wherein the phase changes between all adjacent antenna elements is a discrete, fixed increment.

Claim 10

An antenna assembly as recited in claim 1 further comprising: flank antenna elements having constant phase surrounding said antenna elements coupled to said phase rotation means so that the complexity of said antenna assembly is reduced, and antenna coverage in said flank areas is improved.

Claim 11

An antenna assembly as recited in claim 1 wherein said phase rotation means includes means for fixing the phase vector associated with adjacent antenna elements not centered about a null in accordance with the formula Mφ wherein M is an integer, φ is the angle of the antenna element about the null center.

Claim 12

An antenna assembly as recited in claim 1 wherein said phase rotation means are adjusted so as to minimize the phase difference of the signals applied to adjacent ones of said antenna elements thereby maximizing the gain of said antenna assembly.

Claim 13

An antenna assembly as recited in claim 1 wherein said phase rotation means produces more than one substantially frequency independent null, each of the nulls being surrounded by antenna elements having a phase determined by the formula ##EQU5## the transition of the phase of the signal applied to adjacent antenna elements being adjusted for minimum change.

Claim 14

An antenna assembly comprising: a plurality of antenna elements for radiating and receiving electromagnetic energy; a single processing means, such as a transmitter or receiver, for processing signals acted upon by said antenna assembly; a beam forming network including a plurality of ports associated with said antenna elements and phase rotation means coupled between said processing means and said antenna elements for producing a substantially frequency independent null by adjusting the phase of a signal applied to each of said antenna elements so that with respect to a null point there are equidistant rings of beam with equal amplitude and phase increments of ##EQU6## wherein N R is the number of beams per equidistant ring set and M is an integer; said beam forming network including variable power divider means for splitting and combining power two ways in any ratio; said beam forming network including variable phase shifter means coupled to said plurality of ports for adjusting the phase of the signal exciting each one of said plurality of ports associated with said antenna elements; said variable phase shifter means being adapted to adjust the phase of adjacent beams in an equidistant ring with respect to the null point so that the phase difference between adjacent beams is ##EQU7## the phase of the signal applied to one of said antenna elements being equal to the amount of rotation of the center of the antenna element about the null with respect to a reference line; said variable power divider means being adapted to adjust the amplitude of phasors associated with the beams in an equidistant ring so that there are sequentially phased signal phasors adding to zero amplitude to form a null and any constituent beam sidelobe frequency changes remain balanced at the intended null direction thus cancelling out and maintaining an advantageously deep null in spite of a frequency change or increased bandwidth of a given signal; and said antenna elements being arranged so that each antenna element can be a part of a group of three antenna elements wherein each antenna element of said group of three antenna elements is adjacent the other two antenna elements of said group of three antenna elements.

Claim 15

An antenna assembly comprising: a plurality of antenna elements for radiating and receiving electromagnetic energy; a single processing means, such as a transmitter or receiver, for processing signals acted upon by said antenna assembly; a beam forming network including a plurality of ports associated with said antenna elements and phase rotation means coupled between said processing means and said antenna elements for producing a substantially frequency independent null by adjusting the phase of a signal applied to each of said antenna elements so that with respect to a null point there are equidistant rings of beam with equal amplitude and phase increments of ##EQU6## wherein N R is the number of beams per equidistant ring set and M is an integer; said beam forming network including variable power divider means for splitting and combining power two ways in any ratio; said beam forming network including variable phase shifter means coupled to said plurality of ports for adjusting the phase of the signal exciting each one of said plurality of ports associated with said antenna elements; said variable phase shifter means being adapted to adjust the phase of adjacent beams in an equidistant ring with respect to the null point so that the phase difference between adjacent beams is ##EQU7## the phase of the signal applied to one of said antenna elements being equal to the amount of rotation of the center of the antenna element about the null with respect to a reference line; said variable power divider means being adapted to adjust the amplitude of phasors associated with the beams in an equidistant ring so that there are sequentially phased signal phasors adding to zero amplitude to form a null and any constituent beam sidelobe frequency changes remain balanced at the intended null direction thus cancelling out and maintaining an advantageously deep null in spite of a frequency change or increased bandwidth of a given signal; and said antenna elements being arranged so that each antenna element can be a part of a group of three antenna elements wherein each antenna element of said group of three antenna elements is adjacent the other two antenna elements of said group of three antenna elements.

Claim 16

An antenna assembly as recited in claim 13 wherein at least some of said antenna elements are part of a group which form an incomplete circle about the null.

Claim 19

A method as recited in claim 15 wherein the step of equally spacing the excitation phases in accordance with the formula Mφ wherein M is some integer and φ is the angle of the element about the null center.

Claim 20

A method as recited in claim 15 wherein choosing the amount of phase rotation of a signal applied to an antenna element includes determining the relative amount of spatial rotation of the center of that antenna element about the null position with respect to a reference line.

Claim 21

A method as recited in claim 16 further comprising the step of minimizing the phase difference of the signals applied to adjacent ones of the antenna elements thereby maximizing the gain of the antenna beam coverage pattern.

Claim 24

A method as recited in claim 19 wherein the step of adjusting the phase includes spacing the phase of the excitation signal applied to adjacent antenna elements, which are equidistant from the null, by an amount equal to (360°)/N R , where N R is the number of such equidistant antenna elements.

Claim 25

A method as recited in claim 20 further comprising the step of reducing dependence of the phase adjustment on the formula (360°)/N R , with increasing distance from the null.