The power consumption in a communication system depends on the technology of the processor and the number of processing stages in decimation part. Programmability in the decimation filter, allows it to adapt to the different channel bandwidths, interferers requirements of the different standards, while maintained the power consumption at a minimum. The appearance of various standards in communication technologies in the world requires a good technique that able to provide a compatible standard replacing any part of the system by the software defined radio (SDR) technology. Digital down converter (DDC) filter is one of a typical type of data rate converter that could be used to satisfy the Software defined radio applications. The DDC decimation fitter require to design with full flexibility in terms of pass band ripple, adjacent band rejection and blocker requirements by optimizing the FIR filter design based on SDR concept. The main aim of this book is to design and implementation of the Digital Down Converter (DDC) filter with low pass band ripple and high attenuation in the adjacent rejection and blocker requirements in the filter response for Software Defined Radio(SDR)