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modulation scheme

Thread Summary

The user asks about the AD8307's response to different modulation schemes. The final answer confirms that the AD8307 data is based on un-modulated sine waves, and the intercept changes with modulation. An RMS responding RF detector is recommended for modulated signals. The slope remains constant, but the intercept varies with the modulation scheme.
AI Generated Content
Category: Hardware
Product Number: AD8307

Hello

My customer chosen AD8307 for their RF comm. 2026 product.

I am sorry to so fundamental question, but would you please advise again?

------------

Q1

Customer think the test condition of the graphs ; Fig 5, Fig 6, Fig 33 are no-modulation ( just sin inputs).
Is this understanding correct?

Q2

Could you please let us know whether the ERROR(dB) in Fig 5, Fig 6 will be worsen, or not changed in case following modulation scheme(*) ?

Q3

Could you please let us know whether the Fig33 graph will be changed? or not changed , in case of following modulation scheme(*)?

( Is it depend on  average-magnitude of input and if maginitude had increased, graph goes left? )

(*)Customers Modulation scheme

*QPSK
*PI by 4 shift - QPSK
*16QAM
*64QAM

I am sorry to bother you again..., but please advise.

Best Regards

  • All of the data in the AD8307 datasheet is collected using an un-modulated sine wave. If the you plan to apply signals with different modulation schemes (e.g. psk, QAM, etc), then AD8307 is the wrong choice. For each modulation scheme, you  will get a different response. The slope of the response will always be the same but the intercept will change with modulation scheme. This is explained in the AD8313 datasheet in the section called “Effect of Waveform Type on Intercept”.  

    A better choice would be an rms responding rf detector

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