Pll oscillation circuit, polar transmitting circuit, and communication device

A PLL oscillation circuit which includes a reference frequency oscillator, a phase comparator, a loop filter, and a voltage-controlled oscillator;

• the PLL oscillation circuit comprising:
• a PM-PM table that is utilized for compensating a nonlinearity of the voltage-controlled oscillator;
• a variable current source connected in between the voltage-controlled oscillator and a supply potential terminal;
• an amplitude detector that detects an output amplitude of the voltage-controlled oscillator;
• an amplitude controller that controls a current value of the variable current source so as to have the output amplitude of the voltage-controlled oscillator detected by the amplitude detector to be a desired amplitude;
• a LPF connected in between the amplitude controller and the variable current source;
• and
• a switch that connects or disconnects the LPF between the amplitude controller and the variable current source, and
• when switching an output frequency of the voltage-controlled oscillator, a connection of the switch is turned on, so as to connect the amplitude controller to the variable current source through the switch, and to update a setting value in the PM-PM table to be a value that corresponds to an output frequency after the switching, and
• when the voltage-controlled oscillator outputs a desired frequency signal, the connection of the switch is turned off and the amplitude controller is connected to the variable current source through the LPF.