IQmath Library

IQNtoIQ
IQN number to GLOBAL_Q
Description
This Macro converts an IQ number in IQN format to the GLOBAL_Q
format.
Declaration _iq _IQNtoIQ( _iqN A)
Input
Output
Usage
IQ number in IQN format
Equivalent value of input in GLOBAL_Q format
This macro may be used in cases where the result of the calculation
performed in different IQ resolution to be converted to GLOBAL_Q
format.
Example:
Following example calculates the magnitude of complex number (X+jY)
in Q26 format:
Z = sqrt(X^2 + Y^2)
The values Z, X, Y are given as GLOBAL_Q = 26, but the equation itself
may generate an overflow.
To guard against this, the intermediate calculations will be performed
using Q = 23 and the value converted back at the end as shown below:
_iq Z, Y, X; // GLOBAL_Q = 26
_iq23 temp;
temp = _IQ23sqrt( _IQ23mpy(_IQtoIQ23(X), _IQtoIQ23(X)) +
_IQ23mpy(_IQtoIQ23(Y), _IQtoIQ23(Y)) );
Y = _IQ23toIQ(temp);
©Texas Instruments Inc., June 2002 20