Frequency model of dual-loop optoelectronic oscillators

Optoelectronic oscillators (OEO for short) can generate RF and microwave signals with high spectral purity and low phase noise. They are widely used in wireless communication and radar systems. According to the number of loops, OEO can be divided into three structures, including single loop, double loop and multi-loop. The double-loop OEO has the advantages of relatively simple structure, high side mode rejection ratio and good stability, and is widely used. However, there is no accurate frequency model yet, which limits the accuracy of frequency modulation and further optimization of parameters. In this paper, the transfer function of double loop photoelectric oscillator is established based on the theory of single loop photoelectric oscillator. On this basis, the frequency model of the double loop photoelectric oscillator is proposed, and the simulation of the model under different parameters is carried out. At last, parameter selection is briefly discussed. The results show that when the power distribution factor of the two loops is the same, the frequency of the double-loop OEO has a simple corresponding relationship with the change of the loop length. At this time, the double-loop OEO is equivalent to the special single-loop OEO, which is convenient for frequency modulation. The frequency model can be used for frequency tuning, parameter design and optimization of photoelectric oscillator, and has high application value.