IF Filter

An IF filter or intermediate frequency filter passes certain bands of frequency while rejecting others. The relationship between these bands determines the type of filter. For example a lowpass filter passes all frequencies below a cut-off frequency while rejecting all other frequencies. Conversely, a highpass filter passes everything above the cut-off and rejects everything below it. A bandpass filter can be thought of as a highpass plus a lowpass with the cut-off frequency of the highpass filter less than the lowpass filter. As a result only a band of frequencies pass and all else is rejected. Finally, a bandstop filter (or band reject filter) is the compliment of a bandpass. It rejects all frequencies between the lowpass cut-off and the highpass cut-off while passing everything else.

In communication systems energy is transmitted as electronic fluctuations. These electronic signals contain everything from digital data to voice and visual information. Once received the signal must undergo electronic filtering to get rid of other, unwanted data on adjacent frequency bands. The information is encoded with a modulation scheme on a carrier frequency. Thus, the desired information resides in a band centered about the carrier frequency. However, in order to digitally process, display or hear this information it must be converted down from the RF carrier frequency to baseband frequency -- DC to the passband width frequency. The number of conversion steps required is determined by the frequency of the carrier and amount of distortion that can be tolerated. Each down convert, achieved by a mixer, is termed an intermediate frequency and requires an IF filter and amplifier. The need for IF filtering is quite ubiquitous in electronics. Virtually every device that transmits or receives information requires at least one IF filter.

Filtronetics, Inc. manufactures nearly every type of electronic IF filter available. For low frequency and power applications we offer LC filters. At higher frequencies we supply crystal, monolithic, LC, SAW and ceramic IF filters. And at high frequency we provide custom microwave filters. We can build from one custom IF filter prototype to over 1 million IF filters. We offer surface mount, through-hole, and connectorized packages.