Phase synchronization circuit and in-phase distribution circuit
In a case where signals branched from a single reference signal source are transmitted via a plurality of cables, a phase synchronization circuit can be used to stabilize a phase of a signal to be outputted from each cable. However, the phases of signal to be outputted from each cable is affected by combination of a length of each cable and an amount of delay caused by feedback control, so that phases of synchronization signals to be outputted from a plurality of transmission paths are not always the same as each other. In the present invention, since a frequency multiplier that multiplies a frequency of a signal outputted from each transmission path by an even number is provided for a phase synchronization circuit, the phases of the synchronization signals to be outputted from the transmission paths are aligned even when signals are branched from one reference signal.
1. A phase synchronization circuit, comprising:
phase control circuitry to output a transmission signal to a transmission path for signal transmission, and control, on a basis of a control signal corresponding to a phase difference between the transmission signal and a return signal obtained by returning the transmission signal to the transmission path, a phase of a transmission signal to be outputted to the transmission path;
signal returning circuitry to return, as the return signal, part of the transmission signal outputted from the phase control circuitry to the transmission path; and
a frequency multiplier to multiply, by an even number, a frequency of the transmission signal that is outputted from the transmission path and is not returned by the signal returning circuitry, and output the transmission signal having the multiplied frequency.
2. The phase synchronization circuit according to claim 1 , wherein the phase control circuitry includes:
a signal separator to separate the transmission signal into two transmission signals, and output the two transmission signals,
a phase controller to control, when one of the two transmission signals outputted from the signal separator is inputted, a phase of the input transmission signal on a basis of the control signal, and output the input transmission signal of which the phase is controlled to the transmission path, and output the return signal returned by the signal returning circuitry to the signal separator, and
a phase comparator to output, to the phase controller, the control signal corresponding to the phase difference between the other one of the two transmission signals outputted by the signal separator and the return signal outputted by the phase controller to the signal separator.
3. The phase synchronization circuit according to claim 2 , wherein the signal separator includes a 90-degree hybrid coupler.
4. The phase synchronization circuit according to claim 1 , wherein the signal returning circuitry includes a 90-degree hybrid coupler.
5. An in-phase distribution circuit, comprising:
a reference signal source to generate a reference signal;
an in-phase distributor to divides the reference signal into a plurality of in-phase signals, and output the plurality of in-phase signals as transmission signals; and
a plurality of phase synchronization circuits to receive the respective transmission signals outputted from the in-phase distributor, wherein
the plurality of phase synchronization circuits each include:
phase control circuitry to control, on a basis of a control signal corresponding to a phase difference between the corresponding transmission signal outputted to a transmission path for transmission and a return signal obtained by returning the transmission signal to the transmission path, a phase of a transmission signal to be outputted to the transmission path;
signal returning circuitry to return, as the return signal, part of the corresponding transmission signal outputted from the phase control circuitry to the transmission path;
a frequency multiplier to multiply, by an even number, a frequency of the corresponding transmission signal that is outputted from the transmission path and is not returned by the signal returning circuitry, and output the transmission signal having the multiplied frequency.
6. The in-phase distribution circuit according to claim 5 , further comprising: a plurality of frequency synthesizer to each generate a signal that is higher in frequency than the reference signal on a basis of the signal outputted from the corresponding frequency multiplier.
7. The in-phase distribution circuit according to claim 5 , wherein the signal returning circuitry and the frequency multiplier are provided on a single board, for the corresponding transmission path of the in-phase distribution circuit.
8. The in-phase distribution circuit according to claim 6 , wherein the signal returning circuitry and the frequency multiplier are provided on a single board, for the corresponding transmission path of the in-phase distribution circuit.