A communications device, comprising: a reference phase-locked loop, PLL, configured to provide a target signal; and a controller configured to calibrate the reference PLL such that the target signal tracks a reference signal when the communications device transitions from a first mode of operation to a second mode of operation, wherein the controller (120; 214) is further configured to calibrate the reference PLL by adjusting the target frequency by a predetermined amount, the predetermined amount representing a pre-known shifting of the target signal that results from transitioning between the first mode of operation and the second mode of operation; characterized in that the controller (120; 214) is further configured to further calibrate the reference PLL by further adjusting the target frequency to compensate for operational condition; wherein the reference PLL comprises: a voltage controlled oscillator, VCO, configured to provide the target signal in response to a tuning signal (168; 254) and a frequency control signal (166; 268), wherein the controller module (120; 214) is configured to adjust the frequency control signal (166; 268) by an amount based upon the tuning signal (168, 254) in order to adjust the target signal; the tuning signal (168, 254) being indicative of a difference between the reference signal and the target signal and the controller module (120; 214) being adapted to minimize an alternating current, AC, component of the tuning signal (168, 254) during calibration. a reference phase-locked loop, PLL, configured to provide a target signal; and a controller configured to calibrate the reference PLL such that the target signal tracks a reference signal when the communications device transitions from a first mode of operation to a second mode of operation, wherein the controller (120; 214) is further configured to calibrate the reference PLL by adjusting the target frequency by a predetermined amount, the predetermined amount representing a pre-known shifting of the target signal that results from transitioning between the first mode of operation and the second mode of operation; characterized in that the controller (120; 214) is further configured to further calibrate the reference PLL by further adjusting the target frequency to compensate for operational condition; wherein the reference PLL comprises: a voltage controlled oscillator, VCO, configured to provide the target signal in response to a tuning signal (168; 254) and a frequency control signal (166; 268), wherein the controller module (120; 214) is configured to adjust the frequency control signal (166; 268) by an amount based upon the tuning signal (168, 254) in order to adjust the target signal; the tuning signal (168, 254) being indicative of a difference between the reference signal and the target signal and the controller module (120; 214) being adapted to minimize an alternating current, AC, component of the tuning signal (168, 254) during calibration. a voltage controlled oscillator, VCO, configured to provide the target signal in response to a tuning signal (168; 254) and a frequency control signal (166; 268), wherein the controller module (120; 214) is configured to adjust the frequency control signal (166; 268) by an amount based upon the tuning signal (168, 254) in order to adjust the target signal; the tuning signal (168, 254) being indicative of a difference between the reference signal and the target signal and the controller module (120; 214) being adapted to minimize an alternating current, AC, component of the tuning signal (168, 254) during calibration.