important about rf mixer

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

Knows can reply