Xiupu Zhang

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (89)101.53 Total impact

  • Ran Zhu, Xiupu Zhang
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    ABSTRACT: A linearization technique using two lasers with different wavelengths is further studied to improve output signal and suppress second and third order nonlinearities in radio-over-fiber (RoF) systems simultaneously, if an optical device or a subsystem generates nonlinear distortion and also has wavelength dependent transmission characteristic. In this paper, for an RoF system using an EAM that has wavelength dependent transmission, it is found that the optimum suppression of second order nonlinearity can be achieved by adjusting the power ratio of the two lasers. Compared to using single laser at 1552.6 nm, 1.6 dB improvement of signal power, 23 dB suppression of second order nonlinearity, and 2.1 dB suppression of third order nonlinearity are obtained experimentally. More than 11.5 dB improvement of spurious free dynamic range, 3 dB improvement of input power at 1 dB compression (P1dB), and 4 dB improvement of output P1dB are achieved.
    2014 IEEE/MTT-S International Microwave Symposium - MTT 2014; 06/2014
  • Xiupu Zhang, Ran Zhu
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    ABSTRACT: A broadband predistortion circuit is designed to remove 3rd order intermodulation distortion of electro-absorption modulator in radio-over-fiber system, resulting in spurious free dynamic range improvement of ~9 dB from 7 to 14 GHz.
    Optical Fiber Communication Conference; 03/2014
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    ABSTRACT: A short pulse train with pulsewidth was generated in a quantum dot mode-locked laser (QD MLL). Due to the short dispersion length, it is required to include group-velocity dispersion (GVD) in modeling pulse train generation and evolution from QD MLLs. On the other hand, Kerr effect is also required to consider due to high peak power density in the laser cavity, and its induced self-phase modulation (SPM) also contributes to the pulse evolution. In this paper, a time domain traveling wave model, including the effect of GVD and SPM, combined with rate equations, is established to model the pulse evolution in a single-section QD MLL. It is shown that the pulse evolution calculated by this model is in reasonable agreement with the experiments. The contribution to the pulse evolution by the GVD and SPM impact is discussed.
    IEEE Journal of Quantum Electronics 12/2013; 49(12):1008-1015. · 2.11 Impact Factor
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    ABSTRACT: The Mach-Zehnder modulator (MZM) has been widely used for broadband photonic analog links and high-speed digital optical fiber communication systems because it possesses large modulation bandwidth, low driving voltage, and low chirp. The MZM is a very important optical modulator for photonic applications. In an MZM, the input light is split into two paths, each of which is modulated by an electrical signal. Then the two arms are combined to generate an intensity-modulated light or a phase-modulated light at the output of the MZM. An MZM can be made of lithium niobate (LiNbO3), gallium arsenide (GaAs), or indium phosphide (InP), materials that exhibit some anisotropy in their dielectric properties. Theoretically, the relation of output optical field and driving voltage is a cosine function, i.e., nonlinear transfer function. For RF photonics, the MZM has typically two applications: optical harmonic generation for optical frequency multiplication and optical subcarrier modulation for optical signal modulation. For optical frequency multiplication, high transfer-function nonlinearity is preferred. In contrast, high transfer-function linearity is preferred for optical subcarrier modulation. It is well known that a cosine transfer function can present high or low nonlinearity dependent on operation voltage. Specifically, bias voltages determine the degree of nonlinearity or linearity of the MZM transfer function. For optical frequency multiplication such as millimeter-wave generation, the MZM should be biased at some specific bias points, such as minimum transmission, maximum transmission, and quadrature bias points, to enhance nonlinearity [1]?[2]. For optical subcarrier modulation, biasing an MZM in its linear region such as quadrature bias points allows transmitting broadband RF signals with multioctave bandwidth and improves spurious free dynamic range (SFDR). Therefore, care must be taken to maintain and control the MZM bias point for a specific applicat- on.
    IEEE Microwave Magazine 11/2013; 14(7):102-107. · 1.50 Impact Factor
  • Guangtao Wang, Dongya Shen, Xiupu Zhang
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    ABSTRACT: A novel UWB antenna is presented, which is formed by the modified Sierpinski-carpet fractal with the 50Ω micro-strip. Four resonant frequencies and three operation frequency bands can be observed via measurement between 1GHz-20GHz when return loss is smaller than -10 dB. The bandwidth of lower frequency band is from 1.1GHz to 10.8 GHz.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
  • Dongya Shen, Jianpei Chen, Xiupu Zhang
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    ABSTRACT: A novel statistical model, called RM model, on the mobile channels is proposed. The envelope of the received signal is modeled as a Rician signal with exponent M. The Probability density function (PDF) in dB is derived by using signals in dB. The expectation of received signals (in dB) is in directly proportional to M.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
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    ABSTRACT: A novel high isolation MIMO antenna for WLAN and WiMax operation is proposed. The proposed antenna consists of two back-to-back G-shaped monopoles placed symmetrically with respect to a mushroom-like EBG structure. The measured results show that the proposed MIMO antenna covers WLAN (2350-2550 MHz) and WiMax (3500-3690 MHz) bands with high isolation. The antenna can provide pattern diversity to combat multipath fading.
    2013 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2013
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    ABSTRACT: In this article, an effective design method is presented to design a miniaturized UWB antenna with four band-notches. By carefully integrating C-shaped slots, L-shaped open circuit stub, and T-shaped parasitic strip onto the primitive miniaturized antenna, four band-notches (VSWR > 2) could be achieved at 3.38–3.65 GHz, 4.95–6.05 GHz, 7.42–7.78 GHz, and 8.1–8.9 GHz to reject WiMAX, WLAN, X-band satellite communication, and ITU 8 GHz band signals. Simulated and measured results show that this antenna could operate from 3.15–11.1 GHz (VSWR < 2), and maintain omnidirectional directivity patterns at H-plane. Moreover, the proposed antenna has a very compact size of 18.6 × 22 × 1.5 mm3. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1202–1206, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27546
    Microwave and Optical Technology Letters 06/2013; 55(6). · 0.59 Impact Factor
  • Source
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    ABSTRACT: In this paper, physically-based simulations are carried out to investigate and design broadband and high-output power uni-traveling carrier (UTC) photodiodes. The physical model is first verified by comparison to experimentally measured results. The graded-bandgap structure, which can induce potential gradient, is considered to be used in the absorption layers. It is shown that the electric field in the absorption layer is increased by the gradient, thus the performance of bandwidth and saturation current is improved by 36.6% and 40% respectively for our considered photodiode. Moreover, a modified graded-bandgap structure is proposed to further increase the electric field, and an additional 9.5% improvement in bandwidth is achieved. The final proposed UTC-PD structures will result in 399-GHz bandwidth and 49-mA DC saturation current.
    Optics Express 03/2013; 21(6):6943-54. · 3.55 Impact Factor
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    ABSTRACT: A low-cost broadband analog predistortion circuit (PDC) is designed and experimentally verified in a radio over fiber (RoF) system. A miniature hybrid microwave integrated circuit technique is used to reduce the size and parasitics of PDC. Only two zero bias GaAs beam lead detector diodes and capacitors are used in the PDC. The diodes can be biased at due to zero bias characteristic so that power consumption is reduced. No broadband matching network is required because of high series resistance of the zero bias diodes. The linearization performance is evaluated using an RoF system without and with the PDC. It is shown that the PDC improves the input 1-dB compression power by 0.4-2.2 dB from 7 to 18 GHz; and spurious free dynamic ranges are improved by ~ 10 dB from 7 to 14 GHz and ~ 6 dB from 15 to 18 GHz, limited by fifth order nonlinear distortion.
    IEEE Photonics Technology Letters 01/2013; 25(21):2101-2104. · 2.04 Impact Factor
  • B. Hraimel, Xiupu Zhang
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    ABSTRACT: We propose and investigate the suppression of RoF nonlinearity using a semiconductor optical amplifier combined with simplified mixed polarization. It is found that EVM of OFDM UWB can be improved by up to 10.2dB.
    Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2013; 01/2013
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    ABSTRACT: We investigate by theory and experiment the performance improvement of an orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) transmitted in a radio-over-fiber (RoF) system using a linearized mixed polarization single-drive X-cut Mach-Zehnder modulator (sd-xMZM). The third-order nonlinearity is suppressed due to the polarization dependent electrooptic coefficients of an X-cut MZM. It is found that the improvement of more than 4 dB in 1-dB compression RF power P1 dB is predicted in theory and verified experimentally. In addition, the adjacent channel power ratio and third-order intermodulation distortion to carrier power ratio of an OFDM UWB signal transmitted by an RoF link using mixed polarization sd-xMZM are expressed in closed forms. Finally, it is verified that the bias voltage can be optimized to improve the error vector magnitude by up to ~ 9 dB for an OFDM UWB signal transmission-over-fiber link using mixed polarization sd-xMZM.
    IEEE Transactions on Microwave Theory and Techniques 10/2012; 60(10):3328-3338. · 2.23 Impact Factor
  • Bouchaib Hraimel, Xiupu Zhang
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    ABSTRACT: We experimentally demonstrate a low-cost broadband predistortion circuit (PDC) for the linearization of a single-drive x-cut Mach-Zehnder modulator (sd-xMZM) in broadband analog radio-over-fiber (RoF) links over 3-5 GHz. By tuning the bias current, the nonlinear characteristic of the PDC can be adjusted to linearize different types of nonlinear components in broadband analog RoF links over 3-5 GHz. By adding the PDC in front of the sd-xMZM, input-refereed 1 dB compression point (P1dB) is improved by 2 dB. By evaluating with the two-tone signal, the PDC allows 14 dB improvement in spurious free dynamic range at 4 GHz, and the third-order intermodulation distortion is suppressed by more than 6 dB over 3-5 GHz. Moreover, the error vector magnitude of an orthogonal frequency division multiplexing ultra-wideband signal is improved by more than 2.5 dB.
    IEEE Photonics Technology Letters 09/2012; 24(18):1571-1573. · 2.04 Impact Factor
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    ABSTRACT: We propose and analyze a photonic-assisted periodic triangular-shaped pulses generator, in which a continuous wave (CW) laser is connected to a dual electrode Mach-Zehnder modulator (De-MZM), and then the De-MZM is connected with a normal dispersion fiber or element. A radio frequency (RF) sinusoid directly drives the De-MZM to obtain optical subcarrier modulation with optical carrier suppression. By carefully setting the physical parameters, the generated harmonics of optical intensity can be corresponding to the Fourier components of typical periodic triangular pulses. Numerical simulations reveal that modulation index must be set to 2.305 and bias voltage drift must be within a range from -2.5%-1.5% from the minimum transmission of the De-MZM. In addition, the dispersion must be set correctly to suppress the primary distortion of 4th order harmonics.
    Journal of Lightwave Technology 05/2012; 30(11):1617-1624. · 2.56 Impact Factor
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    ABSTRACT: A novel wideband planar fractal antenna is proposed. It is formed by the modified Sierpinski-carpet fractal with the 50 Ω micro-strip. Good input return loss performance is seen over a 2 to 4.5 GHz bandwidth, and acceptable patterns are seen over frequency range whose return loss is smaller than -10 dB.
    2012 International Conference on Microwave and Millimeter Wave Technology (ICMMT); 05/2012
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    ABSTRACT: Tunable terahertz beat signal generation is demonstrated by using a C-band InAs/InP quantum-dot (QD) mode-locked laser combined with external cavity of two fiber Bragg gratings (FBGs), where one of the FBGs is tunable in wavelength. Beat signals with ultra-high repetition rates quasi-continuously from 1 to 2.21 THz are observed between the two modes, which are phase-correlated due to intracavity four-wave mixing effect in the QD waveguide.
    IEEE Photonics Technology Letters 03/2012; 24(6):518-520. · 2.04 Impact Factor
  • Ran Zhu, Bouchaib Hraimel, Xiupu Zhang
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    ABSTRACT: We present theoretical analysis of simultaneous photonic frequency downconversion, based on four-wave mixing (FWM), and optical subcarrier modulation in an electroabsorption modulator (EAM) for broadband millimeter wave (mm-wave) over fiber uplinks. A model of FWM generation in an EAM is established. The FWM efficiency with an EAM at dc bias with and without RF modulation is analyzed, including the impact of bias voltage, modulation voltage, and frequency detuning. The calculated FWM efficiency agrees well with the measured. The signal-to-noise ratio (SNR) of photonic frequency downconverted RF signal is also analyzed, considering the nonlinear distortion due to the EAM nonlinearities. Moreover, calculated error vector magnitude using theoretical SNR is compared with the measured for multiband orthogonal frequency division multiplexing ultrawideband mm-wave signals.
    Journal of Lightwave Technology 01/2012; 30(3):344-354. · 2.56 Impact Factor
  • Jie Xu, Dongya Shen, Xiupu Zhang, Ke Wu
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    ABSTRACT: A compact disc ultrawideband (UWB) antenna with quintuple band rejections is proposed and demonstrated, which has a portrait shape and is therefore “portrait antenna.” The quintuple band-notched functions are achieved by utilizing C-shaped slots, nested C-shaped slots, U-shaped slots, and open-circuit stubs. It is demonstrated that the portrait antenna operating from 2.45 to 12 GHz (VSWR <; 2) has omnidirectional radiation patterns with a gain greater than 2 dBi, and also five stopbands (VSWR >; 2) of 3.27-3.57, 5.01-5.45, 5.55-6.05, 7.05-7.45 and 7.83-8.19 GHz are implemented simultaneously for rejecting WiMAX, WLAN, downlink of X-band satellite communication, and ITU 8-GHz band signals. Moreover, the antenna has a simple structure and a compact size.
    IEEE Antennas and Wireless Propagation Letters 01/2012; · 1.67 Impact Factor
  • B. Hraimel, Xiupu Zhang, Luo Ma
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    ABSTRACT: We experimentally investigate the impact of out of band interferers on the performance of multiband OFDM UWB signal transmission in RoF systems. An acceptable EVM and ACPR of -17 dB and -20 dB can be achieved even after shifting by 30% from the optimum quadrature bias. Further improvement of EVM and ACPR can be achieved by using mixed polarization technique even under strong interference level when the bias is shifted near minimum transmission.
    Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2012 and the National Fiber Optic Engineers Conference; 01/2012
  • Source
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    ABSTRACT: A novel class of low-cost, small-footprint and high-gain antenna arrays is presented for W-band applications. A 4 $\times$ 4 antenna array is proposed and demonstrated using substrate-integrated waveguide (SIW) technology for the design of its feed network and longitudinal slots in the SIW top metallic surface to drive the array antenna elements. Dielectric cubes of low-permittivity material are placed on top of each 1 $\times$ 4 antenna array to increase the gain of the circular patch antenna elements. This new design is compared to a second 4 $\times$ 4 antenna array which, instead of dielectric cubes, uses vertically stacked Yagi-like parasitic director elements to increase the gain. Measured impedance bandwidths of the two 4 $\times$ 4 antenna arrays are about 7.5 GHz (94.2–101.8 GHz) at 18 $\pm$ 1 dB gain level, with radiation patterns and gains of the two arrays remaining nearly constant over this bandwidth. While the fabrication effort of the new array involving dielectric cubes is significantly reduced, its measured radiation efficiency of 81 percent is slightly lower compared to 90 percent of the Yagi-like design.
    IEEE Transactions on Antennas and Propagation 01/2012; 60(3):1648-1653. · 2.33 Impact Factor

Publication Stats

348 Citations
101.53 Total Impact Points


  • 2004–2013
    • Concordia University Montreal
      • Department of Electrical and Computer Engineering
      Montréal, Quebec, Canada
  • 2011
    • McGill University
      • Department of Electrical & Computer Engineering
      Montréal, Quebec, Canada
  • 2010
    • Beijing University of Posts and Telecommunications
      • State Key Laboratory of Information Photonics and Optical Communications
      Beijing, Beijing Shi, China
  • 2007
    • Polytechnique Montréal
      Montréal, Quebec, Canada
  • 2006
    • Harbin University of Science and Technology
      Charbin, Heilongjiang Sheng, China
  • 2005
    • University of Ottawa
      Ottawa, Ontario, Canada