BobaMosfet
- Joined Jul 1, 2009
- 2,110
In this case, you have one signal input @ 100MHz, for 3 different filter circuits. In any AC circuit if you find a capacitor, it's purpose is to limit current flow. It does this through reactance. With a slow frequency, the capacitor has time to discharge more fully, so more signal gets through. If you raise the frequency, the capacitor has less time to discharge, so begins to block the signal. The smaller the capacitor is, the more quickly it is filled. The size of the capacitor and the speed at which it is allowed to discharge is what filters the signal.
The majority of filtering is being done by the first 2 components (R5 & C6, R1 & L6, and R3 & C4). The resistor determines the rate of charge/discharge and the capacitor or inductor uses it's field to control voltage/current.
Each of these 3 filters utilizes a tank circuit (C5 & L5, C1 & L1, and C3 & L3), next which stores and returns energy to the circuit increasing the voltage level (signal strength).
The 2 following component in each section is a second filter to ensure proper rejection.
The values you are asking about were simply chosen arbitrarily by the author of the text in order to demonstrate wave shapes in the tutorial. You should consider getting a simulator, and implementing the circuit and walking through the tutorial that way so you can make changes on the fly and see what the circuit does, to match the tutorial.
The majority of filtering is being done by the first 2 components (R5 & C6, R1 & L6, and R3 & C4). The resistor determines the rate of charge/discharge and the capacitor or inductor uses it's field to control voltage/current.
Each of these 3 filters utilizes a tank circuit (C5 & L5, C1 & L1, and C3 & L3), next which stores and returns energy to the circuit increasing the voltage level (signal strength).
The 2 following component in each section is a second filter to ensure proper rejection.
The values you are asking about were simply chosen arbitrarily by the author of the text in order to demonstrate wave shapes in the tutorial. You should consider getting a simulator, and implementing the circuit and walking through the tutorial that way so you can make changes on the fly and see what the circuit does, to match the tutorial.