RFin impedance

Question

Fig 11 of ADF4108 datasheet suggest input impedance is 500R at RFinA or RFinB. What might the input impedance look like at 1.7GHz? Or what is capacitance? I can't imagine the impedance is solely real at 1.7GHz.

JudeOsems · Accepted Answer

Hi Mamborocks, 
 The input impedance remains the same regardless the input frequency, there is a 100pF bypass decoupling capacitor on the RFinB path to help filter out noise and stabilize signal power, while the signal in RFinA is AC-coupled for same purpose. I hope this answers your question? 
 Cheers, 
 Jude)

bakcil · Answer

Hi, 
 There is an RFIN S-parameters table in the datasheet in Figure 4. I was looking for a separate S1P file and could not find that. I am sorry for this misinformation. In an S-parameter simulation tool on the Smith Chart, you can use this table to simulate the reactance behavior and complex impedance for a specific frequency.

Regards, Burhan

bakcil · Answer

Similar to the question above, Input sensitivity is also for the single-ended mode, if you want to use only the RFınA and terminate the RFınB, you can use the sensitivity data as -5dBm to +5dBm max. I can suggest checking Figure 5, it shows the sensitivity level related to operating frequency. Regards, Burhan

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RFin impedance