important
mixers basic formula is
rf signal * lo signal = (rf signal - lo signal) + (rf signal + lo signal)
______________________diff = IF signal__ sum = signal
along with the many harmonics .
consider
a dc component present in lo signal . the formula becomes
rf signal *(cont + lo signal) = cont *rf signal + (rf signal - lo signal) + (rf signal + lo signal)
this additional term called rf feed through,
to eliminate this lo stage should be diff one i.e double balanced.
a dc component present in rf signal . the formula becomes
(cont + rf signal) * lo signal = cont *lo signal + (rf signal - lo signal) + (rf signal + lo signal)
this additional term called LO feed through,
to eliminate this rf stage should be diff one i.e double balanced.
a result is come i.e thumb of rule is
To avoid
LO feed through : RF stage should be differential
RF feed through : LO stage should be differential
Thanx
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