Phase difference measuring apparatus for measuring phase difference between input signals

A phase difference measuring apparatus for measuring a phase difference between two input signals having a same frequency, comprising:

• addition/subtraction means for obtaining and outputting one of a sum and a difference of said two input signals;
• A/D converter means for converting said two input signals and an output signal of said addition/subtraction means into discrete data;
• reference signal selection means for selecting one of said two input signals as a reference signal and outputting said reference signal to said addition/subtraction means and said A/D converter means;
• and
• calculation means for calculating the phase difference between said two input signals based on outputs of said A/D converter means, calculating transmission characteristics of at least one of said addition/subtraction means and said A/D converter means based on output signals of said A/D converter means corresponding to said reference signal if said reference signal selection means selects said reference signal, and correcting said calculated phase difference using said calculated transmission characteristics.

A phase difference measuring method for measuring a phase difference between two input signals having a same frequency, comprising the steps of:

• obtaining one of a sum and a difference of said two input signals and outputting a first signal;
• sequentially selecting said first signal and said two input signals and outputting a second signal;
• converting said second signal into discrete data;
• and
• calculating the phase difference between said two input signals based on said discrete data.

A phase difference measuring method for measuring a phase difference between two input signals having a same frequency, comprising the steps of:

• obtaining one of a sum and a difference of said two input signals and outputting a first signal;
• converting said first signal and said two input signals into discrete data;
• calculating the phase difference between said two input signals based on said discrete data;
• selecting one of said two input signals as a reference signal;
• calculating transmission characteristics of a device through which said reference signal passes based on said reference signal;
• and
• correcting said calculated phase difference using said calculated transmission characteristics.