I have built a DDS (0-80MHz) with an FPGA (XC3S400) that I can program it for making almost any wave form (limited frequency by the wave form complexity). After weeks of struggling with making a suitable low pass filter for it, I realized that it is almost impractical to build a near perfect analog filter that can remove all high frequency images (Nyquist) + all low frequency aliases (photos of the results here; hindrances made by low frequency aliases in DDS, figure-1 here).
Now I want to turn into a low pass (or preferably tunable band pass) digital filter but I really have not time for learning DSP from the scratch. I searched some major companies (Analog Devices, Texas Instruments,...) for a dedicated digital filter product but my search always redirects to DSP products.
I want to know if there are dedicated digital filters with a simple interface (for example, frequency selection by a micro-controller interface or something?). For example, sending the desired filter behavior via a serial/parallel word to the device and it works with that.
I realized from the answer below that I can use the current FPGA for my purpose. I tried 2 approaches: 1- DDS > DAC > ADC > FIR (FPGA ) > DAC. this makes again aliases related to the DAC. 2- DDS > FIR ( no external ADC ) > DAC. This is not bad but the problem with aliases remains to some extend. I am looking for a good resource / method of thinking for this problem ( the easiest perhaps ! )