Hi Raja,
Quote:I know that if resister added in series with inductor will reduce the frequency and resister in series with var-actor will increase the frequency. But if you consider tank inductor resistance and varactor resistance are in series so how come they behave differently from frequency point of view?
The series circuit should be converted to its shunt equivalent and the L/C shunt equivalent is used for the resonant frequency calculation. For resistance in series with inductor, this increases the shunt inductance and hence frequency comes down. For resistance in series with capacitance, this decreases the shunt capacitance and hence frequency increases.