9) How to tune with chip inductors

1. Initial chip inductors L1, L2, and L3
Measure initial resonance frequency and impedance (minimum VSWR value) for initial inductor values.
・ Our standard evaluation board values of L1=24nH, L2=220nH, and L3=27nH may be a good starting point. The size of your PCB and location of other components will affect it, but you should be at about 430 ± 50MHz in most circustances. Note if the resonance frequency is higher or lower than your target and how much larger the minimum VSWR is.

 

2. Tuning frequency with L1 and L2
L3 has little effect on frequency so you will be optimizing L1 and L2 to tune the frequency.
・ If the tested resonance frequency is higher than the target, replace initial L1 or L2 with a higher value. Replace L1 or L2 with a lower value if frequency is too low. Fig. 8-4 shows the resonance frequency being dependent on L1 and L2.

 

3. Tuning impedance with L3
After optimizing L1 and L2, the VSWR will have a minimum peak at the target frequency. If VSWR isn't less than 1.2, the impedance is not tuned to 50 ohms and L3 will optimize it.
・ Fig. 8-2 shows how L3 value affects the VSWR.

 

 

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