In general, it can be very difficult. First question that comes into mind when you ask for this type of conversion is - do you really need it? I assume you have some sort of algorithm that you want to see transferred on an FPGA. Fair enough - but does it really need to be hardware-described, or it could simply run as C code on a processor built on FPGA? Is the speed constraint allowing this option, since it is often much easier?

Indeed i want to study the ressources consumed by this code which describe an equalizer, and i see that in matlab there's HDL coder which can do this but i don't have this, so how can i do

Tough one. Yes, MATLAB's HDL coder simplifies the coding for signal processing, but as you don't have it, let's see your alternatives.

1. Code everything in VHDL/Verilog. This one is tough, since you'll have to devise ways for different routines. It will be tiresome and might not really be what you want.

2. Code everything in C and place it on an FPGA-designed processor like Altera's NIOS-II. This could be pretty straightforward, but defying the purpose in a way, not using the advantages of FPGA.

3. Determine bottlenecks of your algorithm and choose parts of it to be hardware based, parts to run on the processor and simply wire them. This is the most powerful solution.