| ??? 05/26/07 03:54 Read: times |
#139859 - Don't take the values too seriously,... Responding to: ???'s previous message |
...what counts is the result.
David said:
If you add C2 and C12 to C4 you get 4pF which leads me to f = 2.054GHz. 
Not C2 and C12, but the series circuit of C2 and C12 which is 1/(1/C2 + 1/C12) = 0.9pF. Again, don't take the values too seriously. This circuit was optimized by try and error, not neccesarily by plain text book calculations. I'm sure this circuit was optimized for a resonance frequency of exactly 2.45GHz, even if the concrete values might look false. David said:
I'm not sure that I see why you need to add C2 and C12 to C4. For high frequencies the connection point between C4 and C7 is virtual at ground. So, every stray capacitance at output adds to C4 and by this shifts the resonance frequency. It's like the biasing network at input of a JFET: Connect a resistance of 1M from input to Vcc and another 1M from input to ground (to bias the input by Vcc/2) and you will result in an input impedance of 500kOhm. Kai |
| Topic | Author | Date |
| RF forum/question? | 01/01/70 00:00 | |
| Physician's Assistant? | 01/01/70 00:00 | |
| Daddy? | 01/01/70 00:00 | |
| Power Amp | 01/01/70 00:00 | |
| this is not a RF forum | 01/01/70 00:00 | |
| Power Amplifier | 01/01/70 00:00 | |
| my intent was not ... | 01/01/70 00:00 | |
| Power Attenuator | 01/01/70 00:00 | |
| What is your problem? | 01/01/70 00:00 | |
| not getting any output | 01/01/70 00:00 | |
| Don't forget C2, C12 and the stray capacitances | 01/01/70 00:00 | |
| a little more.. | 01/01/70 00:00 | |
| Don't take the values too seriously,... | 01/01/70 00:00 | |
| fair enough | 01/01/70 00:00 | |
Electrodynamics instead of electrostatics... | 01/01/70 00:00 |