Patent ID: 8467748

Claim:
A wireless communication unit for compensating for voltage controlled oscillator modulation sensitivity variation comprises: a frequency generation circuit employing a phase locked loop (PLL) circuit comprising a voltage controlled oscillator having a modulation port for directly modulating a signal output from the voltage controlled oscillator, wherein the voltage controlled oscillator is operably coupled to at least one switch and a capacitor bank comprising a plurality of varactors; wherein the wireless communication unit comprises a controller arranged to switch in one or more varactors of the capacitor bank associated with the modulation port of the voltage controlled oscillator via the at least one switch, such that a number of varactors connected to the modulation port varies in a piecewise inverse cubic relationship with respect to a voltage controlled oscillator centre frequency, wherein the piecewise inverse cubic relationship between the number of varactors and the voltage controlled oscillator centre frequency causes a gain of the modulation port to be maintain at a substantially constant value.