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Ideally both of the ports, which is the PA output and the matching net input should be tested so as to know whether the ports are equally matched to your 50 ohms.
Assuming that the circuit before the matching circuit and the circuit after the PA output is also matched at 50 ohms, when combined, it will deliver its maximum possible power.
Hope these details might help.
mckinson said:
When I test the impedance by net analyser ,which terminal should I test , PA output or matching net input ?
thx your reply, but I think the shripline must be not 50 ohm ,If it is 50 ohms , we don't require the mattching net ,because PA output is 50 ohms,and antswitch input is 50 ohms .Do you think so ?
So I don't know how to make matching ?If someone have idea ,pls tell me the step ?
Find the input impedence of Ant sw. If it is not available in datasheet, you can measure the s11 of Ant sw input by network analyzer. Then just match it to 50 ohm(if it is PA output impedence)
1) It isn't clear if you have to design the output stage of a PA or you have to match a "working" PA to a "working" antenna.
2) Assuming the PA is Done, working and tested, you maust know its s22 at large signal. (usually is not far from s22 at low signal). Assuming |s22| is far from 0.
3) Assuming you want be free to know the exact length of the antenna cable.
4) assuming the |s11| of the antenna is far from 0.
5) Due to the assumption 2 & 3 & 4 you must match PA out to the cable and the cable to the antenna.
6) The matching network technology should be choose depending on Power handling, frequency, bandwidth. It span from lumped to distribuited.
7) plot the spar on smith chart and find on that quadrant the spar occur.
dependingg on quadrant design the network.
8) it is not easy describe here how to design. Refer to Agilent AN-154
9) WARNING ! If the transormation ratio is higth and you are handling hi power, pay attention. Voltages may reach dangerous values for human body and current may reach fire risk values.
Thx all , I describe my work . It's mobile design .
From PA to matching network is a 50 ohms stripline circuit ,(it's theorical ,but at fact it's not really 50 ohms ) , from matching networ to ANTSWITCH is a 50 ohms micro_strip circuit . Matching network is ∏ type . How can I design this matchig network ??
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