Long-distance RF frequency and time transfer

An apparatus for distribution of frequency reference to a receiving end over a transmission medium, the apparatus comprising

• a first mixer, preferably of an up-conversion type, adapted to mix a frequency reference signal having a reference frequency with a local oscillator signal having a local oscillator frequency, wherein a mixing product of the first mixer represents a forward frequency reference signal;
• a communication section adapted to transmit the forward frequency reference signal over the transmission medium to the receiving end and adapted to receive a first backward frequency reference signal over the transmission medium from the receiving end, the first backward frequency reference signal being formed by a portion of the forward frequency reference signal reflected back from the receiving end or by replicating the forward frequency reference signal in the receiving end and transmitting the replicated forward frequency reference signal back from the receiving end;
• a second mixer being adapted to mix the first backward frequency reference signal with the local oscillator signal having the local oscillator frequency, wherein a mixing product of the second mixer represents a second backward frequency reference signal;
• and
• a phase comparator and control circuit adapted to adjust the local oscillator frequency based on a phase shift of the second backward frequency reference signal so as to compensate for a phase shift of the forward frequency reference signal that occurs in the transmission medium.