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[TI Quadrature Demodulator] Issue of LO phase shift

Other Parts Discussed in Thread: TRF371125EVM

Hi, I'm Taeyeop.

I have a question about TRF371125EVM,

Now I'm using up-converter for TRF3702 and down-converter for TRF371125EVM.

Both LO signals are divided by 2-way power divider of one signal generator.

By the way, in real case, there will be a phse shift between LO for up-converter and down-converter.

Like this,

Up-converter : RF = (I+j*Q)exp(j*wc*t)

Down-converter : Baseband = RF * LO = RF*exp{-j*wc*(t+theta)}

I think that down-converter doesn't know the exact phase of LO signal.

If theta is not compensated, the term will be remained in demodulated signal like this I=I*cos(theta)+Q*sin(theta).

But, demodulated I/Q signals from TRF371125EVM have alomost no effect of theta.

How is this possible?

Can Down-converter detect phase of LO signals?

Thank you very much for reading.

  • The TRF3711 does not detect or compensate for the phase.  The internal mechanism for generating the quadrature LO is similar between the two devices.  Any LO phase shift between the LO signals will be translated through the system if operated in a loopback system.

    --RJH