The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Milad Kalantari - One of the best experts on this subject based on the ideXlab platform.
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a tunable reflection Transmission Coefficient circuit using a 45 hybrid coupler with two orthogonal variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali FotowatahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8–1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
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A Tunable Reflection/Transmission Coefficient Circuit Using a 45° Hybrid Coupler With Two Orthogonal Variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali Fotowat-ahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8-1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
Efstratios Skafidas - One of the best experts on this subject based on the ideXlab platform.
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comparison of corrected calibration independent Transmission Coefficient method to estimate complex permittivity
Sensors and Actuators A-physical, 2013Co-Authors: Chathurika D Abeyrathne, Malka N Halgamuge, P M Farrell, Efstratios SkafidasAbstract:a b s t r a c t The accuracy of estimation of the frequency dependent complex permittivity of dielectric materials is important for medical applications to perform in situ chemical analysis. The achieved accuracy depends on the measurement apparatus and the methods used for permittivity estimation. Calibrating the sensor before use is not always possible nor is it desirable. The Transmission Coefficient S21 method is usually used because it does not require accurate calibration of the measurement apparatus. In this paper we analyze the disparity, observed in the literature, in the estimated permittivity at lower frequencies when the Transmission Coefficient method and small embedded sensors are used to estimate permittivity. Our results indicate that the large disparity of the permittivity at lower frequencies in the Transmission Coefficient S21 method is caused by the fact that the method neglects the multiple reflections at the air material interfaces. Here we propose a new method, extending the Transmission Coefficient method, to contend with the large disparity at lower frequencies in the existing methods whilst preserving the desirable properties of the method, namely not requiring accurate calibration of the apparatus before use. The proposed method is compared with other calibration dependent and independent methods using Ansoft's HFSS simulation software. The accuracy of these methods is then also verified using on chip coplanar waveguides (CPW) measurements in 1-30 GHz. Results indicate that the accuracy in dielectric estimates can be improved by taking into account both Transmission and reflection Coefficients (multiple reflection model) and reducing the CPW metal layer thickness. Further improvement in the accuracy in this method for short CPW can be achieved if a material of known permittivity can be used as a reference.
Ali Fotowat-ahmady - One of the best experts on this subject based on the ideXlab platform.
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A Tunable Reflection/Transmission Coefficient Circuit Using a 45° Hybrid Coupler With Two Orthogonal Variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali Fotowat-ahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8-1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
Ali Fotowatahmady - One of the best experts on this subject based on the ideXlab platform.
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a tunable reflection Transmission Coefficient circuit using a 45 hybrid coupler with two orthogonal variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali FotowatahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8–1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
Xiangyu Meng - One of the best experts on this subject based on the ideXlab platform.
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a tunable reflection Transmission Coefficient circuit using a 45 hybrid coupler with two orthogonal variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali FotowatahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8–1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
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A Tunable Reflection/Transmission Coefficient Circuit Using a 45° Hybrid Coupler With Two Orthogonal Variables
IEEE Transactions on Microwave Theory and Techniques, 2019Co-Authors: Milad Kalantari, Xiangyu Meng, Ali Fotowat-ahmadyAbstract:This paper presents a tunable reflection/Transmission Coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/Transmission Coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/Transmission Coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced. The circuit is analyzed and closed-form derivations for designing the proposed hybrid coupler are extracted. A prototype of the proposed 45° hybrid and TRTC circuits are fabricated and measured on 1.6-mm FR-4 PCBs at 1 GHz. The measurement results show a fractional bandwidth of 50% for the proposed 45° hybrid and a coverage radius of larger than 0.3 on the Smith chart in a frequency range of 0.8-1.2 GHz for the proposed TRTC circuit, which are well matched to the simulation results.
