The phase control in microwave circuits is an important process for many applications. Especially, inthe phase array antennas, this is the main principle of operation. In the array antennas, each array element is fedby an individual oscillator. The radiation pattern and the radiated power of the antenna can be adjusted bycontrolling the phase of the oscillators. In such applications, the phase shifters have been used frequently.However, their high costs, difficulties in efficiency and design are important disadvantages. Another newtechnique for microwave phase control is called the “Injection locking”. In this method, a single reference signal(injection signal) is connected (injected) in parallel to each microwave oscillator. When the certain conditionsare met, the phase of the each oscillator can be controlled by the signal amplitudes, oscillator’s free runningfrequencies and their quality factors (Q). Thus, the new method offers more cost effective and precise phasecontrol than the phase shifters in microwave applications. In this paper, this new phase control technique isexamined in the theory and in the original application of a 1-GHz oscillator system.
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