Sine/cosine value generation apparatus

• US 8,392,492 B2
• Filed: 01/19/2009
• Issued: 03/05/2013
• Est. Priority Date: 01/19/2009
• Status: Active Grant

• Current Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Original Assignee: Himax Media Solutions, Inc. (Himax Technologies Incorporated)
• Inventors: Tsai, Tien-Ju
• Primary Examiner(s): Alrobaye, Idriss N
• Assistant Examiner(s): LEWIS-TAYLOR, DAYTON A.
• Application Number:
  US12/355,845
• Publication Number:
  US 20100182053A1
• Time in Patent Office: 1,506 Days
• Field of Search: None
• US Class Current: 708/276
• CPC Class Codes: G06F 1/0353 by using symmetrical properties of the function, e.g. using most significant bits for quadrant control

Abstract

An apparatus for generating sine/cosine values of an input phase is disclosed. The apparatus includes a phase projector, an LUT-arithmetic unit, a temp sine/cosine generator and a sine/cosine value generator. The phase projector maps the input phase angle into an octant phase and determines an octant index indicating which octant the input phase angle actually locates and a flag indicating whether or not the input phase happens to be pi/4, 3*pi/4, 5*pi/4 or 7*pi/4. The LUT-arithmetic unit receives the octant phase for provision of its corresponding sine/cosine values. The temp sine/cosine generator receives the corresponding sine/cosine values of the octant phase for provision of temp sine/cosine values based on the flag. The sine/cosine value generator selectively swaps and inverts the temp sine/cosine values as the sine/cosine values of the input phase based on a swap index derived from the octant index.

Claims

1. An apparatus for generating sine/cosine values of an input phase ranging from 0 to 2*pi and expressed with an N-bit number, comprising:

a phase projector mapping the input phase into an octant phase, and determining a flag indicating whether or not the input phase happens to be pi/4, 3*pi/4, 5*pi/4 or 7*pi/4;

an LUT-arithmetic unit receiving the octant phase for provision of its corresponding sine/cosine values;

a temp sine/cosine generator receiving the corresponding sine/cosine values of the octant phase for provision of temp sine/cosine values based on the flag; and

a sine/cosine value generator selectively swapping or inverting the temp sine/cosine values as the sine/cosine values of the input phase based on an octant index indicating which octant the input phase actually locates;

wherein;

the phase projector further determines the octant index;

the phase projector further comprises;

a first acquiring unit acquiring the first 3 MSB bits of the input phase for output as the octant index;

a second acquiring unit acquiring the last N-3 LSB bits of the input phase;

a 2'"'"'s complement code generator finding the 2'"'"'s complement of the output of the second acquiring unit;

a selector selectively choosing the output of the second acquiring unit or the output of the 2'"'"'s complement code generator as the octant phase based on the LSB bit of the octant index; and

a logic circuit generating the flag based on the octant phase and the LSB bit of the octant index.

2. The apparatus as claimed in claim 1, wherein the logic circuit further comprises:

a comparator determining whether or not all bits of the octant phase are logic 0; and

an AND gate pulling high the flag only if the LSB bit of the octant index is logic 1 and the output of the comparator indicates all bits of the octant phase are logic 0.

3. The apparatus as claimed in claim 1, wherein the LUT-arithmetic unit further comprises:

a ROM storing sine/cosine values of octant 0 and outputting the corresponding sine/cosine values of the octant phase.

4. The apparatus as claimed in claim 1, wherein the LUT-arithmetic unit further comprises:

a processor outputting the corresponding sine/cosine values of the octant phase using CORDIC iteration algorithm and based on a normalized phase, wherein the normalized phase is obtained by multiplying the octant phase by pi/4 and truncating the outcome to K bits.

5. The apparatus as claimed in claim 1, wherein the LUT-arithmetic unit further comprises:

a ROM storing sine/cosine values of octant 0 and outputting the sine/cosine values of the primary part of a normalized phase, wherein the normalized phase is obtained by multiplying the octant phase by pi/4 and truncating the outcome to K bits; and

a processor generating the sine/cosine values of the secondary part of the normalized phase using CORDIC iteration algorithm, and combining the sine/cosine values of the secondary part of the normalized phase with the sine/cosine values of the primary part of the normalized phase to output the corresponding sine/cosine values of the octant phase.

6. The apparatus as claimed in claim 1, wherein the temp sine/cosine generator further comprises:

a first selector choosing a constant value or the corresponding cosine value of the octant phase as the temp cosine value based on the flag; and

a second selector choosing the constant value or the corresponding sine value of the octant phase as the temp sine value based on the flag.

7. The apparatus as claimed in claim 6, wherein the temp sine/cosine generator further comprises:

a LUT outputting a swap index indicating whether or not corresponding sine/cosine values of the octant phase is required to swap or invert in the following sine/cosine value generator based on the octant index.

8. The apparatus as claimed in claim 1, wherein the sine/cosine value generator further comprises:

first-level selectors choosing the temp sine/cosine values or their 2'"'"'s complements based on the octant index; and

second-level selectors choosing the outputs of the first-level selectors as the sine/cosine values of the input phase based on the octant index.

9. The apparatus as claimed in claim 7, wherein the sine/cosine value generator further comprises:

first-level selectors choosing the temp sine value or its 2'"'"'s complements based on the second MSB bit of the swap index and choosing the temp cosine value or its 2'"'"'s complements based on the MSB bit of the swap index; and

second-level selectors selectively choosing the outputs of the first-level selectors as the sine or cosine values of the input phase based on the LSB of swap index.