Design And Implementation Of Photonic Beamforming Network Based On Wavelength Division Multiplexing True Time Delay

Optically controlled phased array antennas can realize microwave photonics phase shift among antenna elements with optical true time delay(TTD) line technology, which can effectively offset the restriction of radar bandwidth by aperture transition time and achieve broad-band and wideangle beam scanning. With the implementation of optical TTD line technology, photonic beamforming network has a series of advantages, such as large instantaneous bandwidth, low loss and no beam squint.One novel multi-channel multi-bit programmable photonic beamforming network(PBFN) is proposed in this thesis. Firstly, the thesis has an introduction about research status of PBFN and indicates the development trend of optically controlled phased array radar. Secondly, we theoretically analyze the beam scanning principle of phased array antenna and discuss the optical fiber delay line(OFDL) technology for compensation of microwave photonics phase shift. Finally, we propose two kinds of structures of PBFN based on wavelength division multiplexer. Intensive research works start from following four aspects: requirement analysis of OFDL, fabrication of high-precision OFDL, parameter measurement of TTD unit and performance measurement of PBFN.Main contents of the thesis are summarized as follows:(1) Research status of PBFN at home and abroad are compared. Based on latest research, it is pointed out that the integrated scheme of large phased array antenna and the development of fully photonicsbased phased array radar are two significant research directions in the future.(2) Theoretical analysis is carried out on beam steering principle ofphased array antenna. Optical fiber TTD line technology is applied to overcome beam squint problem and to make up photonic beamforming networks. In addition, the impact of antenna elements number on radiation patterns are discussed.(3) A PBFN based on dense wavelength division multiplexers(DWDMs) is proposed. We introduce the fabrication process of OFDL in detail. The method to realize online fabrication and measurement of high-precision OFDL with optical low coherence interferometer(OLCI) is proposed and experimentally demonstrated. A vector network analyzer(VNA) is applied to measure the microwave transmission performance of DWDMbased PBFN. Finally, the radiation patterns are simulated according to the experimental results.(4) An improved PBFN based on array waveguide grating(AWG) is proposed. With the optimization of optical devices, the performance of the AWG-based PBFN is largely improved. OFDL online fabrication and measurement of TTD unit are performed by a VNA. Through the analysis of the experimental data, we have discussed the level of amplitude ripples and phase ripples between channels. Finally, we design an 8-channel 3-bit PBFN and finish the package design of the prototype.