Post Go back to editing

LO Feedthru of LTC5588-1 EVM

As for LTC5588-1 board, Since I had no single-ended to differential converter, The single ended signals I and Q connected to BBIP and BBQP ports with BBIN and BBQN 50 ohm terminated.
The component f0+fIQ is highly removed, but LO feedthrough is high. I would like to know why this feedthrough is large. Does this come from the unbalanced drive of I and Q ???

Parents
  • FormerMember
    0 FormerMember
on Jul 7, 2021 1:22 PM

The unused differential input pins still need to biased to 0.5V common-mode voltage and bypassed with 10nF to ground. LO feedthru is a function of DC offset voltages on I and Q inputs. It should be as small as possible. 

Reply
  • FormerMember
    0 FormerMember
on Jul 7, 2021 1:22 PM

The unused differential input pins still need to biased to 0.5V common-mode voltage and bypassed with 10nF to ground. LO feedthru is a function of DC offset voltages on I and Q inputs. It should be as small as possible. 

Children
No Data