When an oscillator is perturbed by a periodic injection signal having a frequency close to the oscillator's natural frequency, it synchronizes with the injection frequency. This phenomenon is called as injection locking. When a common periodic injection signal perturbs non-coupled oscillators, these oscillators lock to the injection signal. In this case, the non-coupled oscillators are mutually synchronized. On the other hand, common noise can induce a synchronization phenomenon known as noise-induced phase synchronization in non-coupled oscillators. The noise consists of many frequency components. One of the objectives of this thesis is to analyze these frequency components and their corresponding amplitudes, to facilitate achieving synchronization. Recent studies have attempted to achieve synchronization by using a non-periodic signal such as an environmental signal as an injection signal and to apply this signal for wireless communications. To realize the condition for achieving synchronization by an environmental signal, establishing the relationship between the signal component and the synchronization phenomenon is required. Furthermore, in veri cation experiments, the individual differences of the oscillators are also considered. In the previous study, circuit experiments that consider the individual differences of multiple oscillators were not conducted. These individual differences cannot be ignored in actual oscillators and hence, their in uence is con rmed by examining the implementation circuits of the oscillators having individual differences.