Tracking receiver, antenna apparatus, and tracking method

A tracking method comprising:

• receiving a radio wave in which an antenna receives the radio wave from a radio wave source and outputs a sum signal and a difference signal;
• generating a complex sum signal by performing quadrature detection to the sum signal and then converting a resultant of performing quadrature detection into a digital value, or by converting the sum signal into a digital value and then performing quadrature detection;
• generating a complex difference signal by performing quadrature detection to the difference signal and then converting a resultant of performing quadrature detection into a digital value, or by converting the difference signal into a digital value and then performing quadrature detection;
• correcting a complex difference signal in which a corrected complex difference signal is calculated by correcting the complex difference signal based on the complex sum signal and a first correction coefficient represented by a complex number, the first correction coefficient being used when a leakage of the sum signal into the difference signal is estimated and corrected;
• calculating an orientation direction error in which an orientation direction error is calculated based on the corrected complex difference signal and the complex sum signal, the orientation direction error being a difference between an arrival direction and an orientation direction, the arrival direction being a direction from which the radio wave comes and arrives, the orientation direction being a direction in which the antenna is orientated;
• and
• changing the orientation direction of the antenna so that the orientation direction error approaches zero.