6.4.6 FFTComplexIP

Description

FFTComplexIP computes the Fast Fourier Transform of a source complex vector in place.

Prototype

fractcomplex* FFTComplexIP (int log2N, fractcomplex* srcCV, fractcomplex* twidFactors);

Arguments


Parameters	Description
log2N	Base 2 logarithm of N (number of complex elements in source vector)
srcCV	Pointer to the source vector
twidFactors	Pointer to twiddle factors

Return

Pointer to the base address of the destination sample.

Remarks

N must be an integer power of 2.

The elements in the source complex vector are expected in a natural order. The resulting transform is stored in bit-reverse order.

The srcCV vector must be allocated in the Y-Data space with address alignment to a modulo of N.

To avoid saturation (overflow) during computation, the values of the source vector should be in the range [-0.5, 0.5].

Only the first N/2 twiddle factors are needed.

The twiddle factors must be initialized with conjFlag set to zero.

Output is scaled by the factor of N.

Source File

Function Profile


Program Words	PIC32A
	46


Cycle count	Transform Size (N)	PIC32A
	Transform Size (N)	Cycles if Twiddle Factors in X-mem	Cycles if Twiddle Factors in P-mem
	32	1,780	2,318
	64	4,060	5,356
	128	9,188	12,228
	256	20,588	27,564
	512	45,684	61,428
	1024	100,476	135,548
	2048	219,268	296,580

System resource usage