基于双偏振调制器的相位编码技术研究
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摘要
提出了一种新型的基于双偏振调制器(Polm)实现相位编码的方法,不仅可以保证编码信号180°相移,而且可以实现微波编码信号的宽带可调谐。当微波信号加载到第1个Polm时,从第1个Polm输出的信号是两路偏振垂直、相位互补的信号;该信号经过带通滤波器(BPF)滤除下边带,只留下两路偏振正交的载波和上边带,再调谐偏振控制器(PC),使得两路正交的信号进入到第2个Polm里,这时第2个Polm起着光开关的作用;根据加载的射频信号的幅度不同,经过检偏器(Pol)检偏,可以分别实现两路不同的偏振信号输出,由于两路上边带的相位是互补的,最终可以实现可调谐相位编码信号的产生。
A photonic approach to generating apreciselyπphase-shifted phase-coded millimeter-wave waveform with large frequency tunability based on dual-polarization modulators(PolMs)is firstly proposed and demonstrated.A pair of complementary phase-modulated signals is generated along the xand ydirections of PolM1,when a radio frequency signal is applied to the RF port of PolM1.As the modulated signals are complementary phase-modulated ones,the phase difference between first-order sidebands along the xand ydirections isπphase shift,obviously,the polarization of complementary phase-modulated signals is orthogonal,and that of the optical carrier and first order sideband is also orthogonal.Then the lower sideband is filtered by a bandpass filter.Thanks to the orthogonality between the optical carrier and higher first order sideband along xand ydirections,they can be adjusted to an angle of 45°and 135°relative to the principal axis of PolM2with a polarization controller(PC).When a switching pulse signal is applied to the PolM2,the polarization directions of the two orthogonal lightwaves at the output of PolM2will exchange,and the phase-coded millimeter-wave waveform with large frequency tunability and preciseπphase shift will be realized at the output of the polarizer.
A photonic approach to generating apreciselyπphase-shifted phase-coded millimeter-wave waveform with large frequency tunability based on dual-polarization modulators(PolMs)is firstly proposed and demonstrated.A pair of complementary phase-modulated signals is generated along the xand ydirections of PolM1,when a radio frequency signal is applied to the RF port of PolM1.As the modulated signals are complementary phase-modulated ones,the phase difference between first-order sidebands along the xand ydirections isπphase shift,obviously,the polarization of complementary phase-modulated signals is orthogonal,and that of the optical carrier and first order sideband is also orthogonal.Then the lower sideband is filtered by a bandpass filter.Thanks to the orthogonality between the optical carrier and higher first order sideband along xand ydirections,they can be adjusted to an angle of 45°and 135°relative to the principal axis of PolM2with a polarization controller(PC).When a switching pulse signal is applied to the PolM2,the polarization directions of the two orthogonal lightwaves at the output of PolM2will exchange,and the phase-coded millimeter-wave waveform with large frequency tunability and preciseπphase shift will be realized at the output of the polarizer.
引文
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[2]Seeds A J,Williams K J.Microwave photonics[J].Journal of Lightwave Technology,2006,24(12):4628-4641.
[3]Skolnik M.Role of radar in microwaves[J].IEEE Transactions on Microwave Theory and Techniques,2002,50(3):625-632.
[4]Zeitouny A,Stepanov S,Levinson O,et al,Optical generation of linearly chirped microwave pulses using fiber Bragg gratings[J].IEEE Photonics Technology Letters,2005,17(3):660-662.
[5]McKinney J D,Leaird D E,Weiner A M.Millimeter-wave arbitrary waveform generation with a direct space-to-time pulse shaper[J].Optics Letters,2002,27(15):1345-1347.
[6]Chi H,Yao J P.All-fiber chirped microwave pulse generation based on spectral shaping and wavelength-to-time conversion[J].IEEE Transactions on Microwave Theory and Techniques,2007,55(9):1958-1963.
[7]Chi H,Yao J P.An approach to photonic generation of high-frequency phase-coded RF pulses[J].IEEE Photonics Technology Letters,2007,19(10):768-770.
[8]MIAO Wang,YU Jin-long,WANG Ju,et al.Low phase noise microwave source based on regeneratively modelocked system[J].Journal of Optoelectronics·Laser,2012,23(9):1702-1707.苗旺,于晋龙,王菊,等.基于再生锁模系统的低相噪微波源[J].光电子·激光,2012,23(9):1702-1707.
[9]Chi H,Yao J P.Photonic generation of phase-coded millimeter-wave signal using apolarization modulator[J].IEEE Microwave and Wireless Components Letters,2008,18(5):371-373.
[10]Li Z,Li W,Chi H,et al.Photonic generation of phase-coded microwave signal with large frequency tunability[J].IEEE Photonics Technology Letters,2011,23(11):712-714.
[11]Li Z,Li M,Chi H,et al.Photonic generation of phase-coded millimeter-wave signal with large frequency tunability using apolarization-maintaining fiber Bragg grating[J],IEEE Microwave and Wireless Components Letters,2011,21(12):694-696.
[12]LI Ming,LI Ze,YAO Jian-ping.Photonic generation of preciselyπphase-shifted binary phase-coded microwave signal[J].IEEE Photonics Technology Letters,2012,24(22):2001-2004.
[13]Ghelfi P,Scotti F,Laghezza F,et al.Photonic generation of phase-modulated RF signals for pulse compression techniques in coherent radars[J].Journal of Lightwave Technology,2012,30(11):1638-1644.
[14]Bull J D,Jaeger N A F,Kato H,et al.40 GHz electro-optic polarization modulator for fiber optic communication systems[A].Proc.of SPIE[C].2004,5577:133-143.
[15]PAN Shi-long,YAO Jian-ping.Tunable subterahertz wave generation based on photonic frequency sextupling using apolarization modulator and a wavelength-fixed notch filter[J].IEEE Transactions on Microwave Theory and Techniques,2010,58(7):1967-1975.
[16]WEI Zhi-hu,WANG Rong,PU Tao,et al.Research of UWB pulse generation and transmission in fiber[J].Journal of Optoelectronics·Laser,2012,23(8):1482-1488.魏志虎,王荣,蒲涛,等.超宽带信号的产生及其光纤传输的研究[J].光电子·激光,2012,23(8):1482-1488.
[17]WANG Qing,YAO Jian-ping.A high speed 2×2 electrooptic switch using apolarization modulator[J].Optics Express,2007,15(25):16500-16505.