Re: [Discuss-gnuradio] A problem to the FFT Block

[Tom Rondeau]

On Tue, Nov 13, 2012 at 10:43 AM, Zhiwen He <address@hidden> wrote:

hello all,


When I use the fft blcok, it seems not right.

I build the test system like this:   Square source -> IFFT -> FFT -> File Sink,  when the input is 1, the output in the file sink is 1, and when the intput is 0, the output is random, sometimes 0, sometimes between -1 and 1.

Like this:

input:

						0	0	0	0	0	0	0							0	0	0	0	0	0	0							0	0	0	0	0	0	0
						0						0							0						0							0						0
						0						0							0						0							0						0
						0						0							0						0							0						0
						0						0							0						0							0						0
						0						0							0						0							0						0
0	0	0	0	0	0	0						0	0	0	0	0	0	0	0						0	0	0	0	0	0	0	0						0

output:

						0	0	0	0	0	0	0							0	0	0	0	0	0	0							0	0	0	0	0	0	0
						0						0							0						0							0						0
	0					0						0							0						0							0						0
0						0						0			0				0						0							0						0
			0		0	0						0		0		0			0						0		0					0						0
		0		0		0						0	0				0	0	0						0	0		0	0	0		0						0
						0						0							0						0						0	0						0

How should I do, so that the source data is the same as the sink data?

Thanks.

Heyutu

Hi Heyutu,

I just tried this right now and don't have a problem. This is my full graph:

sig_source (square wave) -> throttle -> stream_to_vector(fftsize) -> fft(fftsize, reverse) -> multiply_const(fftsize*[1/fftsize], fftsize) -> fft(fftsize, forward) -> vector_to_stream -> time sink

Tom