It also shows that the bandwidth's attenuation is quite high (about -4/-5dB).
#Band pass filter designer code
Running this code with Octave/Matlab is a better way to design a hairpin filter than my calculator but it takes tens of minutes per simulation, depending on the frequency range, mesh size and of course computing resources.ĭownload the code on my GitHub repository: Geometry Use the form under to compute the element length for any given frequency. The microstrip hairpin filter generatorĮnter your desired elements length in the following form to generate an SVG or Kicad file.
#Band pass filter designer generator
Update (): The generator can now directly generate a Kicad footprint (kicad_mod file). Hence, I created this Javascript tool to generate them using a sensible experimental model. However, it is quite hard to extract a recipe and it will often result in poor performance. There are a lot of papers describing the mathematical models of microstrip filters. It takes up relatively low board space and it quite easy to build compared to other band-pass microstrip topologies such as the interdigital filter. The hairpin topology uses parallel-coupled lines and behaves like a band-pass filter used to isolate the bandwidth's frequencies from parasitic signals.
One of my 1090MHz hairpin microstrip filters, made using this generator. These discontinuities present a reactive impedance to a wavefront traveling down the line, and these reactances can be chosen by design to serve as approximations for lumped inductors, capacitors or resonators, as required by the filter.
There are several geometries used to construct distributed element filters, but all have the common property of causing a discontinuity on the transmission line. Microstrip filters are a higher-frequency alternative that uses the physical shapes and positions of transmission lines to affect their attenuation on specific frequency ranges. As frequency grows, this becomes increasingly unreliable. They are notably useful in the radio UHF range, to remove undesired transmissions and therefore improve the receiver's relative sensitivity.Īn SDR (software design radio) such as the RTL-SDR with good filtering and an adequate antenna (and possibly external amplification), can pick up very low amplitude signals such as satellite transmissions.įilters are usually made of discrete components (capacitors, inductors, etc.) in certain arrangements to form low-pass, high-pass, band-pass or band-cut. Update (): added tests with JLCPCB manufactured filters What is a hairpin filter?Įlectronic filters are circuits which remove unwanted frequency components from the signal to enhance the signal-to-noise ratio.