What are Electronic Signal Filters? Real-world signals contain both wanted and unwanted information. Therefore, some kind of electronic signal filtering technique must separate the two before processing and analysis can begin. Every electronic design project produces signals that require electronic signal filtering, processing, or amplification, from simple gain to the most complex digital-signal processing (DSP). Designers base their electronic signal filter implementation selections on the desired bandwidth and accuracy of the target system. These parameters, along with hardware costs, determine the system's speed (sample rate), resolution (number of bits), type of A/D converter (sigma-delta, successive-approximation, flash), and anti-alias filter technology. Choosing an electronic signal filter technology (analog/DSP) is less straightforward than simply selecting a transfer function from among Butterworth, Bessel, elliptic, or FIR-40, -60, -80 dB. The best solution depends heavily on the application. Linear-active filters serve applications that require system bandwidths as close as possible to the sampling frequency, with a sharp cutoff. Simple two or three-pole versions serve as anti-alias filters to block clock feed-through or as reconstruction filters for systems employing switched-capacitor or DSP solutions. Switched-capacitor designs work best where space is at a premium, system accuracy does not exceed 10 or 12 bits, and where this approach’s DC accuracy and stability specifications are adequate. Appropriate applications employing passive electronic filters have frequencies in the megahertz range or lack available power. DSP filters serve primarily when transfer-function requirements have no counterpart in the analog world, or when DSP already resides on the circuit board to perform other functions. Electronic designers often try to ensure a product's signal integrity by constructing their own electronic filter circuitry. Unfortunately, the time and money associated with engineering design and assembly efforts make the actual cost of such an electronic filter very high. The filter may require a complex arrangement of sensitive components that consume precious board real estate and compromise system reliability. In addition, some of these components can generate their own alias signals. Design engineers generally understand their own applications very well. Typically, however, they are not filtering experts. Limited experience with electronic filter designs and a limited familiarity with basic electronic filtering components often make creating an effective and accurate solution difficult and time-consuming. 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 filter, amplifier and oscillator component 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, we design and manufacture products to agreed-upon performance specifications, utilizing the latest analog and DSP technologies. How can we help you? We have 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 filter design, and describes many of the design considerations and problems that will be encountered by electronic signal filter designers. Our electronic filter design guide reflects our more than 30 years of experience in the field. If you are considering the purchase of electronic filtering or other signal processing components, 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.