Element-level self-calculation of phased array vectors using interpolation

1. A beam forming integrated circuit comprising:

a storage including a look-up table in which phase shift values ψ are stored for discrete dwell directions in a tabular form; and

an interpolator in which phase shift values for intermediate dwell directions are obtained from the stored phase shift values using interpolation including combining an initial phase shift value for a given discrete dwell direction with one or more shifted versions of a phase shift value to produce an interpolated phase shift value for a given intermediate dwell direction, the interpolator including interpolation circuitry configured to receive an interpolation address specifying an index into the look-up table and interpolation bits defining an interpolation value for each of a number of dimensions and further configured to produce an interpolated phase setting value for an array element based on the interpolation address, the phase setting values stored in the look-up table, and the interpolation bits.

2. A beam forming integrated circuit according to claim 1 , wherein the phase shift values include two-dimensional values.

3. A beam forming integrated circuit according to claim 2 , wherein the two dimensions correspond to spherical coordinates.

4. A beam forming integrated circuit according to claim 1 , wherein the interpolation is linear interpolation.

5. A beam forming integrated circuit according to claim 1 , wherein the interpolation is non-linear interpolation.

6. A beam forming integrated circuit according to claim 1 , wherein the phase shift values ψ are unwrapped.

7. A beam forming integrated circuit according to claim 1 , wherein the interpolation circuitry comprises:

first circuitry configured to obtain a floor phase setting value for a given dimension from the look-up table based on the index;

second circuitry configured to obtain a ceiling phase setting value for the given dimension from the look-up table based on the index;

differencing circuitry configured to produce a difference value for the given dimension based on the floor phase setting value and the ceiling phase setting value;

scaling circuitry configured to scale the difference value based on interpolation bits for the given dimension; and

combining circuitry configured to combine the scaled difference value with the floor phase setting value.

8. A beam forming integrated circuit according to claim 7 , wherein:

the scaling circuitry comprises shifting circuitry configured to produce shifted interpolation values based on the interpolation bits;

each interpolation bit is associated with a distinct value 2 −n times a fixed angle step value, where n is from 1 to the number of interpolation bits in the interpolation address; and

the interpolation circuitry is configured to produce a scaled difference value for each of the two dimensions and combine the scaled difference values with the floor phase setting value to produce the interpolated phase setting value.

9. A phased array system comprising:

a beam forming controller; and

a beam forming integrated circuit according to claim 1 , wherein the beam forming controller is configured to provide a dwell direction to the beam forming integrated circuit.

10. A phased array system according to claim 9 , wherein the phase shift values include two-dimensional values.

11. A phased array system according to claim 10 , wherein the two dimensions correspond to spherical coordinates.

12. A phased array system according to claim 9 , wherein the interpolation is linear interpolation.

13. A phased array system according to claim 9 , wherein the interpolation is non-linear interpolation.

14. A phased array system according to claim 9 , wherein the phase shift values ψ are unwrapped.

15. A phased array system according to claim 9 , wherein the interpolation circuitry comprises:

first circuitry configured to obtain a floor phase setting value for a given dimension from the look-up table based on the index;

second circuitry configured to obtain a ceiling phase setting value for the given dimension from the look-up table based on the index;

differencing circuitry configured to produce a difference value for the given dimension based on the floor phase setting value and the ceiling phase setting value;

scaling circuitry configured to scale the difference value based on interpolation bits for the given dimension; and

combining circuitry configured to combine the scaled difference value with the floor phase setting value.

16. A phased array system according to claim 15 , wherein:

the scaling circuitry comprises shifting circuitry configured to produce shifted interpolation values based on the interpolation bits;

each interpolation bit is associated with a distinct value 2 −n times a fixed angle step value, where n is from 1 to the number of interpolation bits in the interpolation address; and

the interpolation circuitry is configured to produce a scaled difference value for each of the two dimensions and combine the scaled difference values with the floor phase setting value to produce the interpolated phase setting value.

17. A beam forming method comprising:

storing a look-up table in which phase shift values ψ for discrete dwell directions are stored in a tabular form in a beam forming integrated circuit; and

using interpolation to obtain phase shift values for intermediate dwell directions from the stored phase shift values including combining an initial phase shift value for a given discrete dwell direction with one or more shifted versions of a phase shift value to produce an interpolated phase shift value for a given intermediate dwell direction, the interpolation including receiving an interpolation address specifying an index into the look-up table and interpolation bits defining an interpolation value for each of a number of dimensions and producing an interpolated phase setting value for an array element based on the interpolation address, the phase setting values stored in the look-up table, and the interpolation bits.

18. A beam forming method according to claim 17 , wherein the phase shift values include two-dimensional values.