project:hgg:shf:lowpass
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Beide Seiten der vorigen RevisionVorhergehende ÜberarbeitungNächste Überarbeitung | Vorhergehende Überarbeitung | ||
project:hgg:shf:lowpass [2012-01-01 20:53] – reloc0 | project:hgg:shf:lowpass [2012-01-05 10:41] (aktuell) – 84.56.156.215 | ||
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- | This Lowpass filter is made of 2 LC filters and a terminating Resistor (R_L). The terminating Resistor can be ommited | + | This Lowpass filter is made of 2 LC filters and a terminating Resistor (R_L). The terminating Resistor can be omited |
+ | Note: Imput and output of the filter must be matched to the system impedance (e.g. 50 Ohm). | ||
==== What we expect ==== | ==== What we expect ==== | ||
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Thus, what we expect can be seen in this picture. | Thus, what we expect can be seen in this picture. | ||
+ | ==== Formulas ==== | ||
+ | The Formulas will be used to perform calculations on a base filter, not on the filter in the picture shown above. To perform calculations for this filters, the formulas are needed. | ||
+ | * {{: | ||
+ | * {{: | ||
+ | * {{: | ||
+ | * {{: | ||
+ | * {{: | ||
+ | ==== How this was used, when we built filters ==== | ||
+ | |||
+ | Since we did not have a device for measuring an Inductor but very just inductors (1%) we decided to use one of the inductors. We set our Cutoff Frequency and calculated the needed values. Calculations were performed for one of the base filters (LC). Thus we took two inductivities (L) from the stack and one Capacitor with double the size as for one filter (the picture above says 2C). | ||
+ | |||
+ | Forget formulas for more complicated filters but use simulation tools instead! There is a very old DOS based software " | ||
+ | |||
+ | ====== A few words on HF ====== | ||
+ | |||
+ | As we have found out while experimenting, | ||
+ | |||
+ | If the wavelength is less than approx. 10 to 100x the size of your components or wires in the circuitry, you will have lots of parasitic effects due to line inductance or stray capacitance which alter network behaviour. Example: At frequencies about 1 GHz, (wavelength 30 cm) you cannot use wires etc. longer than some millimeters without considering its parasitic effects. | ||
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+ | ====== Errata ====== | ||
+ | If you find errors, please tell or fix them (this is a wiki after all). | ||
+ | |||
+ | ====== Further reading ====== | ||
+ | * http:// | ||
+ | * http:// | ||
+ | * http:// | ||
project/hgg/shf/lowpass.1325447595.txt.gz · Zuletzt geändert: 2012-01-01 20:53 von reloc0