Patent ID: 7301405

Claim:
A phase locked loop circuit comprising: a first voltage controlled oscillator; a first frequency transform circuit to which the output of said first voltage controlled oscillator is connected; a first phase detector to a first input of which the output of said first frequency transform circuit is connected, and to a second input of which a first reference signal is connected; a first charge pump circuit to which the output of said first phase detector is connected; a first loop filter to which the output of said first charge pump circuit is connected, wherein the output of said first loop filter is connected to a frequency control terminal of said first voltage controlled oscillator; a first counter circuit to which the output of said first voltage controlled oscillator is input; a first accumulator circuit to which the output of said first counter circuit is input; and a first loop characteristics detection circuit that detects the loop characteristics of the phase locked loop circuit based on the result obtained by integrating the output of said first counter circuit through said first accumulator circuit.