Efficient angle rotator configured for dynamic adjustment
An apparatus and method for angle rotation is disclosed to rotate a complex input by the angle θ to produce a rotated complex output signal. A memory storage device generates control information based on a coarse angle θ M . A coarse rotation butterfly circuit uses the control information to rotate the complex input signal by the coarse angle θ M to produce an intermediate complex number. The control information controls one or more multiplexers and/or adders in the coarse rotation butterfly circuit to rotate the complex input signal. The fine rotation butterfly circuit uses the control information to rotate the intermediate complex number by a fine angle θ L to produce the complex output signal. The control information controls one or more multiplexers and/or adders in the fine rotation butterfly circuit to rotate the intermediate complex number.
1. A digital device for rotating an input complex number having a plurality of coordinates and for producing at least one coordinate of a rotated complex number, comprising:
a coarse rotation module having a plurality of multiplexers;
a memory including:
a first read only memory having a plurality of addressable locations, and configured to store a set of bits for controlling the plurality of multiplexers for a first set of fine-stage angles, and
a second read only memory configured to store a set of bits for controlling the plurality of multiplexers for a second set of fine-stage angles, the angles of the second set being larger than the angles of the first set,
wherein the coarse rotation module is configured to:
receive at least one coordinate of an input complex number and either the set of bits from the first read only memory or the set of bits from the second read only memory for controlling the plurality of multiplexers,
use the set of received bits to control the plurality of multiplexers, and
produce at least one coarsely rotated coordinate; and
a fine adjustment circuit configured to receive the at least one coarsely rotated coordinate and perform a fine rotation on the at least one coarsely rotated coordinate to produce the at least one coordinate of a rotated complex number.
2. The digital device of claim 1 , further comprising:
a phase accumulator coupled to the memory and configured to produce a normalized truncated phase angle having a coarse angle value and a fine angle value.
3. The digital device of claim 2 , further comprising:
a conditional angle negation module coupled to the phase accumulator, wherein the conditional angle negation module is configured to receive a first bit of the normalized truncated phase angle as a first input and a plurality of additional bits of the normalized truncated phase angle as a second input.
4. The digital device of claim 3 , wherein the conditional angle negation module is configured to communicate a set of the plurality of additional bits of the normalized truncated phase angle to the memory.
5. The digital device of claim 4 , wherein one bit in the set of the plurality of additional bits of the normalized truncated phase angle is a first fine-angle bit.
6. The digital device of claim 5 , wherein the memory is configured to select the first read only memory or the second read only memory based on the value of the first fine-angle bit.