Coherent phase-synchronizing circuit
View Patent ↗Embodiments of the invention provide advances in liquid-crystal technology for use as tunable phase-delay lines. The amount of phase delay through the liquid crystal is adaptively tuned, in order to coherently combine two signals, regardless of their phase differences. By adaptively adjusting the phase delays in the two signal paths, maximum coherent power combining is ensured. This ability to coherently combine the power of two signals regardless of their initial phase differences can greatly simplify, for example, antenna-diversity techniques used in MIMO applications as well as other applications.
1. A circuit for coherent phase-synchronization configured to automatically synchronize phases of a first signal and a second signal that are out of phase with respect to one another, the circuit comprising:
a first liquid crystal voltage-controlled delay line configured to receive the first signal and propagate the first signal to a first output;
a second liquid crystal voltage-controlled delay line configured to receive the second signal and propagate the second signal to a second output;
a mixer configured to multiply the first and second signals received from the first and the second outputs to produce a phase-difference induced direct current (DC) voltage;
a first transistor;
a second transistor;
a first integrator; and
a second integrator,
wherein the DC voltage produced by the mixer causes an imbalance in the conduction of the first and second transistors, and
wherein the imbalance in the conduction causes a higher voltage of the imbalance to be applied to one of the first and second liquid crystal voltage-controlled delay lines thereby decreasing a propagation velocity through the one of the first and second liquid crystal voltage controlled delay lines, and
wherein the imbalance in the conduction causes a lower voltage of the imbalance to be applied to the other of the first and second liquid crystal voltage-controlled delay lines thereby increasing a propagation velocity through the other of the first and second liquid crystal voltage-controlled delay lines, and
wherein the first and second integrators are configured to hold the applied voltages to the respective first and second liquid crystal voltage-controlled delay lines.
2. The circuit of claim 1 , wherein each of the first and second liquid crystal voltage-controlled delay lines comprises a signal path passing through each respective liquid crystal.
3. The circuit of claim 2 , wherein each of the signal paths comprises a co-planar waveguide, stripline, microstrip, or any other transmission line that passes through a liquid-crystal medium.
4. The circuit of claim 1 , wherein the mixer additionally produces a high-frequency voltage, the circuit further comprising:
a low pass filter configured to eliminate the high-frequency voltage.
5. A method for automatically synchronizing phases of a first and a second signal that are out of phase with respect to one another, the method comprising:
receiving the first signal by a first liquid crystal voltage-controlled delay line configured to propagate the first signal to a first output;
receiving the second signal by a second liquid crystal voltage-controlled delay line configured to propagate the second signal to a second output;
detecting a phase difference between the first signal and second signal received from the first and the second outputs;
applying an increasing voltage to one of the first or second liquid crystal voltage-controlled delay line to decrease propagation of the first or second signal based on the detected phase difference;
simultaneously applying a decreasing voltage to the other of the first or second liquid crystal voltage-controlled delay lines to increase propagation of the other of the first or second signal based on the detected phase difference; and
holding voltage levels of the first and second liquid crystal voltage-controlled delay lines when the detected phase difference goes to zero.
6. A method for automatically synchronizing phases of a first signal and a second signal that are out of phase with respect to one another, the method comprising:
receiving the first signal by a first liquid crystal voltage-controlled delay line configured to propagate the first signal to a first output;
receiving the second signal by a second liquid crystal voltage-controlled delay line configured to propagate the second signal to a second output;
multiplying the first and second signals received from the first and second outputs with a mixer to produce a phase-difference induced direct current (DC) voltage, wherein the DC voltage produced by the mixer causes an imbalance in the conduction of a first and a second transistor;
applying a higher voltage of the imbalance to one of the first and second liquid crystal voltage-controlled delay lines thereby decreasing a propagation velocity through the one of the first and second liquid crystal voltage controlled delay lines;
applying a lower voltage of the imbalance to the other of the first and second liquid crystal voltage-controlled delay lines thereby increasing a propagation velocity through the other of the first and second liquid crystal voltage-controlled delay lines; and
holding the applied voltages to the first and second liquid crystal voltage-controlled delay lines with a respective first and second integrator.
7. The method of claim 6 , wherein the mixer additionally produces a high-frequency voltage, the method further comprising:
eliminating the high-frequency voltage with a low pass filter.