Whether you realize it or not, digital filters are pervasive in many applications in our every day life. From your ordinary cell phone and iPod to sophisticated oil exploration equipment, the digital filter is the basic component upon which many of our technologies are built.

This website presents a revolutionary new type of digital filter that is much better performing and much more efficient than current methods of digital filtering. It assumes that the reader has a background in Digital Signal Processing and has at least some familiarity with the basic concepts of digital filtering. Basic background information can be found online by googling "digital signal processing" and "digital filter."


The sole purpose of Pan Filter Technology is to introduce and apply a revolutionary all purpose, multi-function, near-ideal digital filter, named after its inventor, Dr. Cheh Pan. The Pan Filter provides near-ideal performance at a much cheaper cost than conventional digital filters. The Pan Filter is the easiest to use and best performance filter for offline data analysis and a faster, better, smaller digital filter for real time applications.

An All Purpose, Multi-Function, Near-Ideal Digital Filter
The Pan Filter: An All Purpose, Multi-Function, Near-Ideal Digital Filter

The Pan Filter is a complete system of designing efficient near-ideal filters directly in the Frequency Domain. It achieves its results by filtering a signal directly in the Frequency Domain using the Fast Fourier Transform (FFT) and the Inverse Fast Fourier Transform (IFFT). The Pan Filter is not fast convolution; it is however a perfected Fourier Filter.


The Gibbs phenomenon is the main problem associated with filtering directly in the Frequency Domain. It was discovered over 100 years ago and was previously thought impossible to remove. The genius of the Pan Filter is that it completely removes the Gibbs phenomenon from the input signal with several simple, yet revolutionary techniques. As a result, near ideal filtering results can now be achieved at a fraction of the cost of conventional methods.

A signal filtered without the patented Pan Filter Gibbs phenomenon removal

A signal filtered with the patented Pan Filter Gibbs phenomenon removal


The Pan Filter is a major achievement in the field of DSP, and will fundamentally change the way signals are digitally filtered. Filtering a signal directly in the frequency domain is the simplest and fastest way to digitally filter a signal, if the Gibbs phenomenon is not a problem. It is the best filter to use for offline data analysis because:

  • Unlike conventional digital filters, there is no need to worry about which filter algorithm to use or the number of taps of the filter. The Pan Filter also does not change the phase of the input signal during the filtering process.
  • In addition, the output of the Pan Filter contains no beginning and end transients. Unlike conventional filters, the Pan Filter fully filters the entire input signal, and none of the output of the filter needs to be thrown away. Better performing conventional filters result in longer transients which means longer portions of the filter output need to be thrown away. With the Pan Filter, there is no need to worry about the trade-off between filter performance and how much of the filter output needs to be thrown away.
  • Finally, offline filtering of data using the FFT & IFFT is much faster than through conventional means, especially for higher order filters.

For real time applications such as audio and communications:

  • Unlike conventional filters, the Pan Filter is not a laggy filter.
  • The Pan Filter achieves 20 to 50+ dB more noise rejection than comparably sized conventional filters.
  • The Pan Filter is 100's to 1000's of coefficients/taps smaller than comparably performing conventional filters.
  • The bottom line is that the Pan Filter provides near-ideal performance at a much cheaper cost than conventional digital filters. This makes it particularly suitable for applications where computational resources (area, power), latency, or speed (data throughput) is an issue. From another perspective, given the same amount of computational resources, you can achieve much better filtering results with the Pan Filter. As a result, the Pan Filter will eventually replace many conventional digital filters.

A signal low pass filtered with a near-ideal 512 tap FIR filter that uses a 1024 point FFT & IFFT

Similar results can be accomplished with the Pan Filter using a 16x smaller 64 point FFT & IFFT

Though the basic techniques of the Pan Filter are simple, the technology behind them and its implementation are not. Those interested in understanding the background technology of the filter can jump to the Technology section of this website. Those interested in only the results can jump to the Demos section.


The Pan Filter has been heavily reviewed by many technical experts, and is a published and patented technology with many applications. Offline data will be filtered faster and more accurately, communication devices will have clearer conversations, and audio devices will have cleaner, crisper sound. This is a fundamental breakthrough in digital filtering technology, and will enable products that are of higher quality and performance, simpler design, and lower cost. The Pan Filter will enable your company to stay at the forefront of technology and help you attain or retain a leadership position in your industry.

Pan Filter Technology is currently seeking partners for further joint technical and marketing development of the filter. Please email info@panfilter.com for more information. This is not an offer to sell this technology.