Optically-controlled microwave beam forming networks

Abstract

Optically controlled microwave beam forming networks comprise 2N single frequency DFB lasers of different wavelengths, , 2N electro-optic intensity modulators, 2N *1 passive wavelength division multiplexers, an optical fiber, 1*2N optical beam splitter, 2N fiber collimator, a time delay network module, 2N coupled lenses, 2N photoelectric detectors and 2N low noise amplifiers, wherein N is an integer larger than 2. The optically controlled microwave beam forming networks have the advantages of the high signal to noise ratio, good dynamic performance, high time delay precision, continuous adjustability, and good stability, and are easy to be extended in the system array size.

Description

technical field [0001] The invention relates to a broadband optically controlled phased array radar, in particular to an optically controlled microwave beamformer. Background technique [0002] The beamformer (BFN-Beam Forming Networks) is the core of phased array radar and smart antenna. It controls the phase difference or true delay difference of each microwave link in the array to make the radiation field of each microwave radiation source in the far field The specific direction of the interference is extremely large, and the purpose of energy directional emission (or reception) is achieved. Change the phase difference or true delay difference between microwave links to control the direction of the beam. [0003] Beamforming, essentially processing multi-element reception (transmission) to obtain a specific pattern, is the premise and basis for good tactics and performance of modern radar and electronic countermeasure equipment. [0004] The Optically Controlled Microwa...

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Problems solved by technology

[0005] Traditional beamforming networks using phase shifters have beam tilt effects [see literature [1]Michael Y.Frankel and Ronald D.Esman,True Time-Delay Fiber-optic Control of an ultrawideband Array Transmitted Receiver with Multibeam Capability],, The noise figure of the optical multi-beamformer using a wide-spectrum light source is more than 30dB higher than that of an external modulation link using a single-frequency light source, which seriously affects the signal-to-noise ratio of the system and limits the dynamic range of the system. It is not suitable for transmitting vector signals and other objects. For occasions with high noise requirements (see literature [2] Reconfigurable Optical Beamformer for Simplified Time Steered Arrays, US2002 / 0181874A1, Dec.5, 2002), this system uses a single-frequency light source, and the signal modulation method adopts an external modulation method; The delay network part of the available beamformer mostly adopts the dispersion characteristics of the medium (see literature [3] Photonic dual RF beam reception of an X band phased array antenna using a photonic crystal fiber-based true-time-delay beamformer, Harish subbaraman, Applied Optics, 47, 6448, 2008) and optical switch generation time delay (see literature [2] Reconfigurable Optical Beamformer for Simplified Time Steered Arrays, US2002 / 0181874A1, Dec.5, 2002; literature [4] Optical beam former for high frequency antenna arrays), for time-delay networks using dispersion characteristics, it is difficult to effectively and quickly control beam scanning, beam scanning speed is slow, response speed is slow, delay accuracy is not high, real-time performance is poor, and operability is not strong; due to optical Switches are relatively expensive. For a 4x4 optical beamformer, the number of optical switches that need to be used is 16 to generate different delays, and the delay cannot be continuously adjusted. Using optical switches to form a delay array will result in high costs. The control structure is complicated, and only partial beam scanning can be realized, so the practical value is not high;

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