FIR interpolator

I have always some issue..

Say I have a baseband signal of band 2MHz clocked at 15MHz. I want to interpolate it by a 4 factor with a 2 stages interpolation.

So I have created two fir interpolators with the fir compiler megawizard.

I have set the first interpolator with a 2x factor and a multicycle implementation so that an input is processed every 4 clocks period and a new output is genereated every 2 clocks period.

I have set the second interpolator with a 2x factor and a multicycle implementation so that an input is processed every 2 clocks period and a new output is genereated every 1 clocks period.

I have set to 47 the number of the coefficients, set the sample rate of the first interpolator at 15*2MHz and 15*2*2 MHz for the second interpolator. Then I've used the autogenerate coefficients button to generate the fixed point coefficient.

Finally I have clocked both the interpolators with the 4x clock, used a counter to set the sink_valid of the first interpolator only for a 1/4 period of the 4x clock, connected the source_valid of the first interpolator with the sink_valid of the second interpolator and set to vcc all the source_ready.

By the way if use a NCO to generate a tone at +-6MHz and observing the interpolated output I cann see aliasing centered at +-30MHz..

So it seems that the first interpolator is working good but the second does not.. any suggestions ?

Thank you !