Re: [Discuss-gnuradio] A strange question involving costas loop

In GRC I have a complex sine source with amplitude 10 and frequency 2000Hz sampled at 4000Hz as a input to the costas loop through a throttle block. The max and min frequency used is +/- 0.157rad/sample which is 100Hz /sample. When I see the output on scope and FFT scope i see peak at 0Hz in the FFt scope but on the oscilloscope I see a sine wave with amplitude 10 on the Inphase component and 0 in the Q component. Why?

The output is shown in the figure.

http://img690.imageshack.us/img690/7879/snapshot1u.jpg

Thanks

On Thu, Feb 4, 2010 at 2:52 PM, Johnathan Corgan <jcorgan@corganenterprises.com> wrote:

On Thu, Feb 4, 2010 at 09:23, Mir M. Ali <mirmurtuza@gmail.com> wrote:

> What is expected if I input a costas loop block with a complex sine wave
> signal? Will the Costas track the sine and give me a baseband output
> containing nothing?

You will get a complex DC value. I will be the magnitude of the input
signal and Q will be 0, plus a small amount of "noise" due to round
off error.

Johnathan