ADF4360-7_output impedance-2

Document created by analog-archivist Employee on Feb 23, 2016
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In ADF4360-7's datasheet, it says: "Experiments have shown that the circuit
shown in Figure 30 provides an excellent match to 50 Ω over a limited operating
range of the ADF4360-7 (850 MHz to 950 MHz). " Here the value of the inductor
is 7.5 nH. But in the "ADF4360 impedance match.xls ", When the frequency is
0.8GHz~0.9GHz, the Inductor value is about 40~50. So I am not sure which
inductor should should be the series L, is it the 47nH or 7.5 nH in the Figure
30?

 

In the table, the R and X value shows the idea impedance due to frequency. The
Series L column just shows if you want to tune the X to 0, the series
inductor's value that you need to add. (It is NOT means the shunt L 47nH)
But in real case, the bond wire and PCB parasitic capacitance will change the
output impedance, the final impedance before the inductor may become totally
different. For example, Z0=63-j240, if PCB parasitic capacitance equal to shunt
1pF, the final impedance is about 10-j100.
So experiments are very important here, as we have no way to accurate count all
the factors.

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