project:hgg:shf:lowpass
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Beide Seiten der vorigen RevisionVorhergehende ÜberarbeitungNächste Überarbeitung | Vorhergehende Überarbeitung | ||
project:hgg:shf:lowpass [2012-01-01 21:19] – 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 omited if not needed (?) but is shown in the graph because we will be calculating it here. It's called a T-Filter. | This Lowpass filter is made of 2 LC filters and a terminating Resistor (R_L). The terminating Resistor can be omited if not needed (?) but is shown in the graph because we will be calculating it here. It's called a T-Filter. | ||
+ | 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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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). | 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). | ||
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+ | Forget formulas for more complicated filters but use simulation tools instead! There is a very old DOS based software " | ||
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+ | ====== A few words on HF ====== | ||
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+ | As we have found out while experimenting, | ||
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+ | 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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====== Further reading ====== | ====== Further reading ====== | ||
* http:// | * http:// | ||
+ | * http:// | ||
+ | * http:// | ||
project/hgg/shf/lowpass.1325449150.txt.gz · Zuletzt geändert: 2012-01-01 21:19 von reloc0