Method and system for baseband amplitude limiting

1. A method for efficiently limiting a vector magnitude, the method comprising the steps of:

providing a first vector, the first vector comprising:

a first magnitude;

a first angle, wherein the first angle is determined from a reference axis; rotating the first vector such that the first angle is substantially zero, wherein rotating the first vector further comprises the steps of:

rotating the first vector through a plurality of angles;

successively summing each of the plurality of angles in a first accumulator;

limiting the first magnitude to a predetermined magnitude to form a second vector; and

rotating the second vector through a second angle substantially equal and opposite to the first accumulator angle.

2. The method of claim 1 , wherein rotating the first vector through a plurality of angles and successively summing each of the plurality of angles comprises:

operating a first Coordinate Rotation Digital Computer (CORDIC) device in vectoring mode, wherein the first CORDIC device comprises initial inputs of the provided first vector:

1 x 0 =I in =sum( I 0 . . . I n )

1 y 0 =Q in =sum( Q 0 . . . Q n )

1z 0 =0,

where n is predetermined;

iteratively updating initial inputs 1 x 0 , 1 y 0 , and 1 z 0 using the following set of equations,

x i+1 =x i −y i d i 2 −i

y i+1 =y i −x i d i 2 −i

z i+1 =z i −d i arctan(2 −i )

wherein d i values are selected based upon the sign of each y i with,

d

i

=

{

+

1

y

i

<

0

-

1

y

i

≥

0

wherein i is a pre-selected iteration number; and

providing outputs 1 x I , 1 y I , and 1 z I , wherein

1 x I =approximately1.647·√{square root over ( x 0 2 +y 0 2 )}=Vector A

1y I =approximately0

1 z I =approximately arctan( y 0 /x 0 )=Vectorθ.

3. The method of claim 2 , wherein limiting the first magnitude to the predetermined magnitude to form the second vector comprises:

applying a first gain factor to the Vector A; and

clipping the Vector A to produce a Vector A′.

4. The method of claim 3 , wherein rotating the second vector comprises:

operating a second CORDIC device in rotation mode, wherein the second CORDIC device comprises:

initial inputs:

2x 0 =Vector A′,

2y 0 =0,

2z 0 =Vector θ; and

and the second CORDIC device provides outputs 2 x I , 2 y I , and 2 z I , wherein

2x I =approximatelyA′ cos θ

2y I =approximatelyA′ sin θ

2z I =approximately0.

5. The method of claim 2 , wherein the first vector comprises a first CDMA voltage vector.

6. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for limiting a vector magnitude, the method comprising:

providing a first vector, the first vector comprising:

a first magnitude;

a first angle, wherein the first angle is determined from a reference axis; rotating the first vector such that the first angle is substantially zero, wherein rotating the first vector further comprises the steps of:

rotating the first vector through a plurality of angles;

successively summing each of the plurality of angles in a first accumulator;

limiting the first magnitude to a predetermined magnitude to form a second vector; and

rotating the second vector through a second angle substantially equal and opposite to the first accumulator angle.

7. The program storage device of claim 6 , wherein rotating the first vector through a plurality of angles and successively summing each of the plurality of angles comprises:

operating a first Coordinate Rotation Digital Computer (CORDIC) device in vectoring mode, wherein the first CORDIC device comprises initial inputs of the provided first vector:

1 x 0 =I in =sum( I 0 . . . I n )

1 y 0 =Q in =sum( Q 0 . . . Q n )

1z 0 =0,

where n is predetermined;

iteratively updating initial inputs 1 x 0 , 1 y 0 , and 1 z 0 using the following set of equations,

x i+1 =x i −y i d i 2 −i

y i+1 =y i −x i d i 2 −i

z i+1 =z i −d i arctan(2 −i )

wherein d i values are selected based upon the sign of each y i with,

d

i

=

{

+

1

y

i

<

0

-

1

y

i

≥

0

wherein i is a pre-selected iteration number; and

providing outputs 1 x I , 1 y I , and 1 z I , wherein

1 x I =approximately1.647·√{square root over ( x 0 2 +y 0 2 )}=Vector A

1y I =approximately0

1 z I =approximately arctan( y 0 /x 0 )=Vectorθ.

8. The program storage device of claim 7 , wherein limiting the first magnitude to the predetermined magnitude to form the second vector comprises:

applying a first gain factor to the Vector A; and

clipping the Vector A to produce a Vector A′.

9. The program storage device of claim 8 , wherein rotating the second vector comprises:

operating a second CORDIC device in rotation mode, wherein the second CORDIC device comprises:

initial inputs:

2x 0 =Vector A′,

2y 0 =0,

2z 0 =Vector θ; and

and the second CORDIC device provides outputs 2 x I , 2 y I , and 2 z I , wherein

2x I =approximatelyA′ cos θ

2y I =approximatelyA′ sin θ

2z I =approximately0.

10. The program storage device of claim 6 , wherein the first vector comprises a first CDMA voltage vector.

11. The program storage device of claim 6 , wherein the program of instructions comprise at least one Very High Speed Integrated Circuit (VHSIC) Hardware Description (VHDL) Language file.