Farrow-Based Decimating Sample Rate Converter
from Altera Corporation
This reference design is supplied with the DSP Builder. The use of this design is governed by, and subject to, the terms and conditions of the Altera Hardware Reference Design License Agreement.
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Overview
The Farrow-based decimating sample rate converter demonstrates a Farrow resampler. You can simulate its performance in MATLAB, change it as required for your application, generate a VHDL version and synthesize it to Altera®devices. The converter is designed for an input clock rate identical to the system clock. For applications where the input rate is much lower than the system clock, time sharing should be implemented to get a cost-effective solution. The DSP Builder example file is FarrowResamp.mdl.
Many integrated systems, such as software defined radios (SDR), require data to be resampled so that a unit can comply with different communication standards, where the sample rates are different. In some cases, where one clock rate is a simple integer multiple of another clock rate, resampling can be accomplished using interpolating and decimating finite impulse response (FIR) filters. However, in most cases the interpolation and decimation factors are so high that this approach is impractical. Farrow resamplers offer an efficient way to resample a data stream at a different sample rate. The underlying principle is that the phase difference between the current input and wanted output is determined on a sample-by-sample basis. This phase difference is then used to combine the phases of a polyphase filter in such a way that a sample for the wanted output phase is generated.
Demonstrated Altera Technology
Block Diagram
Figure 1. Block Diagram
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These reference design illustrations may be used within Altera Corporation devices only and remain the copyrighted property of Altera. They are being provided on an "as-is" basis and as an accommodation, and therefore all warranties, representations, or guarantees of any kind (whether express, implied or statutory) including, without limitation, warranties of merchantability, non-infringement, or fitness for a particular purpose, are specifically disclaimed. Altera expressly does not recommend, suggest, or require that these examples be used in combination with any other product not provided by Altera.
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