Time to digital converter, radio communication device, and radio communication method

A radio communication device comprising:

• an RF unit;
• and
• a baseband unit,
• wherein the RF unit comprises transmitting circuitry and receiving circuitry,
• the receiving circuitry comprises:
• an oscillator to generate an oscillation signal in accordance with a phase difference;
• a time to digital converter to detect the phase difference between the oscillation signal and a reference signal;
• PLL circuitry to perform feed-back control of the oscillation signal so that the phase difference is canceled;
• and
• a reception RF unit to perform reception processing by using the oscillation signal,
• wherein the time to digital converter comprises:
• a counter to measure the number of cycles of a first signal;
• a first phase difference detector to generate a phase difference signal having a pulse width in accordance with a phase difference between the first signal and a second signal having a frequency twice or more as low as a frequency of the first signal;
• a first capacitor to be charged with an electric charge in accordance with the pulse width of the phase difference signal;
• a second capacitor having capacitance N times a capacitance of the first capacitor, the N being a real number larger than 1;
• a comparator to compare a charge voltage of the first capacitor with a charge voltage of the second capacitor;
• a first charge controller to continue to charge the second capacitor until the comparator detects that the charge voltage of the second capacitor is equal to or more than the charge voltage of the first capacitor;
• a first phase difference arithmetic unit to operate the phase difference between the first signal and the second signal, based on a value obtained by dividing a count value of the counter during a charge period of the second capacitor, by the N;
• a second phase difference detector to generate a phase difference signal having a pulse width in accordance with the phase difference between the first signal and the second signal when the first charge controller continues to charge the second capacitor and the comparator detects that the charge voltage of the second capacitor is equal to or more than the charge voltage of the first capacitor;
• a second charge controller to continue to charge the second capacitor until the comparator again detects that the charge voltage of the second capacitor is equal to or more than the charge voltage of the first capacitor after the first capacitor is charged based on the pulse width of the phase difference signal generated by the second phase difference detector;
• a second phase difference arithmetic unit to operate the phase difference between the first signal and the second signal, based on a value obtained by dividing the count value of the counter during the charge period of the second capacitor, by the N squared;
• and
• a third phase difference arithmetic unit to detect a fractional phase difference between the first signal and the second signal, based on the phase difference operated by the first phase difference arithmetic unit and the phase difference operated by the second phase difference arithmetic unit,
• wherein the first phase difference arithmetic unit operates the phase difference between the first signal and the second signal, based on a reference phase, when the counter suspends a measurement operation.

A radio communication method comprising:

• measuring the number of cycles of a first signal by a counter;
• generating a phase difference signal having a pulse width in accordance with a phase difference between the first signal and a second signal having a frequency twice or more as low as a frequency of the first signal;
• charging, into a first capacitor, an electric charge in accordance with the pulse width of the phase difference signal;
• comparing a charge voltage of a second capacitor having capacitance N times a capacitance of the first capacitor, the N being a real number larger than 1, with a charge voltage of the first capacitor;
• continuing to charge the second capacitor until the charge voltage of the second capacitor becomes equal to or more than the charge voltage of the first capacitor;
• operating, by a first phase difference arithmetic unit, the phase difference between the first signal and the second signal, based on a value obtained by dividing a count value of the counter during a charge period of the second capacitor, by the N;
• generating a phase difference signal having a pulse width in accordance with the phase difference between the first signal and the second signal when the second capacitor continues to be charged and it is detected that the charge voltage of the second capacitor is equal to or more than the charge voltage of the first capacitor;
• continuing to charge the second capacitor until it is again detected that the charge voltage of the second capacitor is equal to or more than the charge voltage of the first capacitor after the first capacitor is charged based on the pulse width of the phase difference signal;
• operating, by a second phase difference arithmetic unit, the phase difference between the first signal and the second signal, based on a value obtained by dividing the count value of the counter during the charge period of the second capacitor, by the N squared;
• and
• detecting a fractional phase difference between the first signal and the second signal, based on the phase difference operated by the first phase difference arithmetic unit and the phase difference operated by the second phase difference arithmetic unit,
• wherein the first phase difference arithmetic unit operates the phase difference between the first signal and the second signal, based on a reference phase, when the counter suspends a measurement operation.