What are Digital Filters? Digital filters that incorporate digital-signal-processing (DSP) techniques have received a great deal of attention in technical literature in recent years. Although they rarely serve as anti-aliasing filters (in fact, they need anti-aliasing filters), digital filters merit discussion here because digital filters offer features that have no counterparts in other filter technologies. You can do things utilizing digital filters (unlimited flexibility) that may not be possible in the analog world. DSP represent a growing subset of signal-processing activities that utilize an A/D converter to turn an analog signal into a stream of digital data. An extensive sequence of multiplication's and additions then operate on those data. In some cases, a D/A converter creates an analog equivalent signal at the output of the processed stream. DSP techniques can perform functions such as fast-Fourier transform (FFT), delay equalization, programmable gain, modulation, encoding/decoding, and digital filtering. Figure 1 shows a typical digital filter configuration. Figure 1 - Typical Digital Filter Configuration A digital filter computes a quantized time-domain representation of the convolution of the sampled input time function and a representation of the weighting function of the digital filter. They are realized by an extended sequence of multiplications and additions carried out at a uniform spaced sample interval. Who are we? Frequency Devices - founded in 1968 to provide electronic design engineers with analog signal solutions and engineering services - designs and manufactures standard and custom electronic analog and digital filters, amplifier and oscillator components and instrument products for signal conditioning, signal processing and signal analysis. By addressing a wide array of signal processing needs, Frequency Devices continues to provide state-of-the-art solutions to the rapidly changing electronics industry. >From prototype to production, Frequency Devices designs and manufactures products to agreed-upon performance specifications, utilizing the latest analog and digital technologies. How can we help you? Frequency Devices has posted for your information and reference purposes an "Electronic Filter Design Guide" which you may download from our web site or view online at no cost. It covers all of the basic concepts of electronic analog and digital filter design, and describes many of the design considerations and problems that will be encountered by electronic filter design engineers. Our analog and digital filter design guide reflects our more than 30 years of experience in the field. If you are specifically interested in Digital (DSP) Filters, you may link directly to that section of the design guide. If you are considering the purchase of electronic filtering or other signal conditioning modules, instruments or subassemblies, Frequency Devices offers some of the most advanced signal-processing products in the industry. We will work with you to develop specifications that are appropriate to your unique needs, avoiding either under-specifying or over-specifying in the interest of controlling cost while maximizing performance. You will find descriptions for many of our custom and standard solutions on our web site. If you would like to discuss your particular application and needs with us, we welcome your call or e-mail.