Study On Photonic-assisted Non-uniform Bandpass Sampling

To ensure the efficient operation of the follow-up devices,the down frequency conversion technology is widely used in the signal receiver in many communication systems.Microwave photonic technology has characteristics of wide bandwidth,low loss and strong abiliy to anti-interference.Non-uniform bandpass samping frequency conversion has advantages of simple structure and no need of the local oscillator signal.This paper mainly researches on how to relize the down frequency conversion by the photonic-assisted non-uniform sampling technique which combines the advandages of microwave photonics and non-uniform bandpass sampling.In summary,further study and innovation in three aspects are made in this paper based on the current achievements.First,expanded range of frequency conversion using photonic-assisted non-uniform sampling and interference suppression can be realized simultaneously.Second,picosecond level of ultrashort optical pulses are used as the sampling signal to obtain a better effect of frequency conversion.Third,design and calculation principles of the non-uniform sampling sequence and sampling frequency are described in detail,with two examples for analysis.The ultrashort optical pulses controlled by a non-uniform binary sequence are adopted as the sampling signal whose spectrum width of main lobe is large enough to make sure that sampling frequency conversion can be carried out smoothly.The lack of spectral lines of non-uniform sampling sequences provides the possibility to suppress interference so the way to forcast the spectral distribution of the sequences and the relationship between the spectral distribution and alias spectrum are worthy of investigation.The selection principle of samling sequences,the calculation method of the sampling frequency and the basic theories of some optical techniques are the focuses of this paper.Calulating the sampling frequencies in two cases of WiFi and satellite communication verifies that this scheme of frequency conversion can be applied to variety of communication systems.The stronger ability of interference suppression can be obtained by replacing the binary sampling sequence or the sampling frequency to face the more complicated actual situation,which has more flexibility,portability and practical significance.