Gaofeng Guo

University of Electronic Science and Technology of China, Chengdu, Sichuan Sheng, China

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Publications (13)3.04 Total impact

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    ABSTRACT: A pair of spot-focusing horn lens antenna is the key component in a free-space measurement system. The electromagnetic constitutive parameters of a planar sample are determined using transmitted and reflected electromagnetic beams. These parameters are obtained from the measured scattering parameters by the microwave network analyzer, thickness of the sample, and wavelength of a focused beam on the sample. Free-space techniques introduced by most papers consider the focused wavelength as the free-space wavelength. But in fact, the incident wave projected by a lens into the sample approximates a Gaussian beam, thus, there has an elongation of the wavelength in the focused beam and this elongation should be taken into consideration in dielectric and magnetic measurement. In this paper, elongation of the wavelength has been analyzed and measured. Measurement results show that the focused wavelength in the vicinity of the focus has an elongation of 1%–5% relative to the free-space wavelength. Elongation's influence on the measurement result of the permittivity and permeability has been investigated. Numerical analyses show that the elongation of the focused wavelength can cause the increase of the measured value of the permeability relative to traditionally measured value, but for the permittivity, it is affected by several parameters and may increase or decrease relative to traditionally measured value.
    Review of Scientific Instruments 01/2014; 85(9):094702-094702-8. · 1.60 Impact Factor
  • Juan Wang, Gaofeng Guo, Hu Zheng, En Li
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    ABSTRACT: In this paper, the effects of semi-spherical radome and nose radome enclosed on the characteristics of antenna are investigated in detail by the means of aperture-integration and surface-integration (AI-SI). The AI-SI method is superior to ray tracing when the radome curvature varies significantly. Besides, this algorithm is simply and can be appropriate for any aperture. Calculated far-field patterns enclosed semi-spherical using this numerically technique agree well with the exact pattern for an aperture antenna radiating. In the presence of nose radome with εr=5.2–0.08j, the energy transmission is 73.7%.
    01/2012;
  • Fanghai Xu, Gaofeng Guo, En Li, Ju Wu
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    ABSTRACT: An ultra-broadband power divider based on conventional Wilkinson power divider which operates at 2GHz to 8GHz is designed in this paper. HFSS is used to accelerate the design process. Finally an ultra-broadband 3dB power divider with four impedance transformers is designed and manufactured, and its size is 31mm × 30mm ×0.5mm. The measured results agree well with the electromagnetic simulation that proves the feasibility of the proposed design.
    Millimeter Waves (GSMM), 2012 5th Global Symposium on; 01/2012
  • Minhui Zeng, En Li, Gaofeng Guo
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    ABSTRACT: With the widespread application of electronic products, the hazards of electromagnetic radiation has been drawn much attention. Thus, electromagnetic shielding materials are widely used to suppress electromagnetic radiation. In this paper, test methods of shielding effectiveness of materials ware reviewed. A microstrip-based test system for shielding effectiveness measurement was proposed. Measurement results of S21 parameter for two special shielding materials in the 10 MHz–3 GHz ware derived by this test system. It is shown that this test system can be used to estimate shielding effectiveness (SE) of some plane materials.
    01/2012;
  • Zhenghua Wei, En Li, Gaofeng Guo, Ju Wu
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    ABSTRACT: The paper present a three-section quadrature directional coupler which is bandwide coupled though a slot. In the middle region of the slot, a small ellipticall conducting disk is used to extend bandwidth and increase return loss and isolation. Result of simulation show that the coupler exhibits a coupling equal to 3.3dB±0.9dB accomanied by the return loss and isolation of more than 20dB across the band 2.5GHz–9.2GHz.
    01/2012;
  • Yi Ge, Gaofeng Guo
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    ABSTRACT: The main method of analyzing coupled stripline is using odd and even mode characteristics of stripline. Calculation of even and odd mode impedances for the stripline is the most important issues, and it is the key in the design of broadband coupler. In this paper, using coupled transmission line with Chebyshev form, I designed a broadband stripline directional coupler with 2~18 GHz bandwidth, 10 ± 1dB coupling, VSWR;15dB, and the insertion loss is less than 1dB.
    Millimeter Waves (GSMM), 2012 5th Global Symposium on; 01/2012
  • Xueling Li, En Li, Gaofeng Guo
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    ABSTRACT: This paper presents an approach to the design of three-port H-plane waveguide Y-junction circulator with two partial height ferrite posts in the junction region which has the advantages of high isolation and low insertion loss. With 9.375GHz center frequency and 400MHz bandwidth, the X-band waveguide circulator designed with the approach could be used in microwave measurement systems, whose VSWR is less than 1.2, insertion loss is less than 1dB and isolation is more than 20dB, which could be used in medium power systems and high power systems.
    01/2012;
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    ABSTRACT: A microwave test system to measure the complex permittivity of a low-loss material as a function of temperature has been developed, and it is based on the short-circuited line method. The calibration method for the microwave loss and the phase of the waveguide holder which vary with temperature is discussed in detail. Induction heating is employed to shorten the heating and cooling time of the sample and waveguide. The test system was built at 10 GHz and over the temperature range from room temperature to 2000 °C. The feasibility of the system has been verified by measuring the complex permittivity of quartz at high temperatures.
    Measurement Science and Technology 03/2011; 22(4):045707. · 1.44 Impact Factor
  • Wang Yi, En Li, Gaofeng Guo, Ruixing Nie
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    ABSTRACT: In this letter, a novel design of X-band coaxial-to-rectangular waveguide transitions is presented. The transition includes an original waveguide-to-coaxial mode converter and modified impedance transformer.� Detailed design concept is presented. Feasible way to optimize performance of the transition is analyzed and verified. Very good performance (S11 lower than -30dB) of the transitions was achieved via multy parametric optimization. Index Terms—coax, rectangular waveguide, X-band, transition. oaxial-to-waveguide transitions are necessary and critical microwave components which are widely applied in antenna and waveguide dielectric test technique. Design of transitions from coaxial to waveguide applicable to commercial and military microwave system is of valuable importance. In the dielectric material permittivity test system, the performance of components is critical to the accuracy of the test result. Main aim for the designers is to achieve low levels of return loss during transformation of TEM mode in coaxial to TE-mode in waveguide in operating frequency band. In the case of coaxial-to-ridged waveguide construction, the author of [1] proposed an original mode converter with multistep impedance transformer for the purpose of improving characteristics (bandwidth and return loss). Two cascaded portions of TEM transmission lines compose the cavity of the converter. To reduce in size, the fourth step does two jobs: A mode conversion function together with an impedance matching. It is more difficult for the design of transition from coaxialto-rectangular wave guide than to ridged waveguide because of lager input/output impedance ratio (table I) than ridged waveguide in the same operating frequency band. Generally speaking, additional space consuming section is required for the design of broadband high impedance waveguide structures, such as impedance transformers and mode converter. In this letter, the design of mode converter is based on the utilization of a rectangular cavity and a cylinder probe with conical part, a 4-step Chebyshev-response impedance transformer was designed using the combination construction with single ridge waveguide and reduced size rectangular waveguide. Design formulas resulting in an equal ripple or Chebyshev-type response were given by Cohn [2], Collin, [3] and Riblet, and were experimentally verified.
    01/2011;
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    ABSTRACT: We describe a broadband microwave test system that can measure dielectric properties of microwave low-loss materials at high temperatures using circular cavity method. The dielectric constants and loss tangents of samples at different temperatures were calculated from measured shifts of resonant frequencies and unloaded quality factors of the multimode cavity with and without sample. Detailed design and fabrication of the circular cavity capable of working at temperatures up to 1500◦C are discussed. The measurement theory and new calculation method of the radius and length of the cavity at different temperatures are presented. The hardware system was built to measure dielectric properties at wide frequency band from 7 to 18 GHz and over a temperature range from room temperature to 1500◦C. Measurement results of the dielectric properties of quartz samples are given and show a good agreement with the reference values.
    Progress in Electromagnetics Research-pier - PROG ELECTROMAGN RES. 01/2009;
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    ABSTRACT: Complex permittivity is one of the most important parameters of microwave dielectrics. When the dielectrics work in high temperature environments, the complex permittivity as a function of temperature should be measured while designing dielectrics and applying in microwave devices or radome. A test cavity used at temperature up to 1500degC is designed and fabricated, and the test system for complex permittivity measurement at high temperatures is also built. Some typical samples are measured.
    01/2008;
  • En Li, Gaofeng Guo, Qishao Zhang
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    ABSTRACT: In this paper, the complex permittivity of low loss microwave dielectric disk is measured in broad frequency band by applying cylindrical cavity. The measurement frequency band covers 7-18 GHz by using only one cavity which works in multimode. The paper mainly discusses the design of the cavity, measurement theory and mode search method after the sample is loaded. The length of the cavity does not need to be tuned during the process of measurements.
    Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings; 01/2006
  • Y Zhou, E Li, G Guo, Y Gao, T Yang
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    ABSTRACT: A system has been developed for measuring the complex permittivity of low loss materials at frequencies from 500 MHz to 7 GHz and over a temperature range up to 1500 • C using stripline resonator cavity method. Details of the design and fabrication of the cavity were discussed. Particular features related to high-temperature operation were described. An improved resonance method at high temperature for determining complex dielectric properties of low-loss materials was developed. The calculation process was given by a physical model of the stripline resonator cavity at high temperature. The paper brought forward the method of segmentation calculation according to the temperature changes over the cavity, which matched the actual situation of high temperature measurements. We have verified the proposed method from measurements of some typical samples with the available reference data in the literature.