Transmit modulation testing

An apparatus comprising:

• an LC oscillator having a varactor array with a plurality of slices;
• an oscillator signal coupled to an output of the LC oscillator;
• a plurality of voltages respectively coupled to capacitors of one of slices when the one of the slices is enabled;
• a control voltage coupled to the capacitors of the one of the slices;
• control logic to vary voltage values of the plurality of voltages respectively coupled to the capacitors of the one of the slices that is enabled while other ones of the slices are disabled and the control logic is further configured to set the control voltage to a plurality of control voltage values;
• a frequency measuring circuit coupled to the output of the LC oscillator and configured to measure a frequency of the oscillator signal for each combination of control voltage values and variation in the voltage values of the plurality of voltages supplied to each slice and to supply measured frequency values;
• and
• wherein the apparatus is configured to analyze linearity of oscillator gain (frequency/voltage) based on the measured frequency values for each combination of the voltage values of the plurality of voltages and the control voltage values for each slice.