Junyu Shen

Compact Wideband Circularly Polarized Patch Antenna for CNSS Applications

A compact wideband circularly polarized (CP) patch antenna utilizing a quad-feed network (QFN) and quadruple semi-fan-annulus (QSFA) patches is proposed. For using a coupled-line dual-band power divider (PD) and improved phase shifter (PS) with stepped-impedance-open-stub (SIOS), the QFN has a compact size and exhibits the electromagnetic (EM) simulated bandwidth over 96% for the power distribution -6.5±0.5 dB, return loss (RL) > 14 dB, and a consistent 90° (±9°) phase deviation. Moreover, the QSFA patches can expand the CP bandwidth and reduce the size of the antenna effectively. Measurement results show that the proposed antenna achieves CP bandwidth of 72% from 1.15 to 2.45 GHz for RL > 10 dB, axial ratio dB, and 3-dB gain variation (gain > 4.4 dBi). Therefore, the proposed antenna is a good candidate for Compass Navigation Satellite System (CNSS) applications.

A GENERALIZED COUPLED-LINE DUAL-BAND WILKINSON POWER DIVIDER WITH EXTENDED PORTS

A generalized two-way coupled-line power divider with extended ports for dual band is proposed in this paper. The power divider is composed of two section coupled-lines, one conventional transmission line, and an isolation resistor, and employs extension of a transmission line or coupled-line at each port. The design equations are obtained based on even- and odd-mode analysis, and analytical ideal closed-form scattering parameter expressions derived. Because the traditional ring structure is a special case of coupled line, four cases of this generalized power divider are discussed and compared. In addition, the six power dividers simulated results of three special cases are shown. Finally, three fabricated power dividers measurements are used to certify this proposed structure and corresponding design parameters.

Wideband Single-Layer 90

This letter proposes a novel design approach of wideband 90 ° phase shifter, which comprises a stepped impedance open stub (SIOS) and a coupled-line with weak coupling. The result of analyses demonstrates that the bandwidths of return loss (RL) and phase deviation (PD) can be expanded by increasing the impedance ratio of the SIOS and the coupling strength of the coupled-line. For RL > 10 dB, insertion loss (IL) 1.1 dB, and PD of ±5°, the fabricated microstrip single-layer phase shifter exhibits bandwidth of 105% from 0.75 to 2.4 GHz.

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In this paper, a planar miniaturized arbitrary phase-difference coupler with arbitrary coupling coefficients is proposed. The proposed coupler consists of three coupled-line sections which achieves a compact circuit layout in microstrip implementation. The circuit parameters of this novel coupler can be easily determined by the derived closed-form equations and the corresponding performance analysis in terms of the bandwidth and miniaturization requirement is provided. Two prototypes with this proposed structure, operating at 2 GHz, have been designed and implemented using microstrip technology. One has a 45° phase difference with - 3-dB coupling coefficient and the other demonstrates a 60° phase difference with - 4.77-dB coupling coefficient. In addition, over 20% fractional bandwidth, which is defined as 5° phase error and 0.5-dB magnitude imbalance, is obtained in both of the two prototypes.

Phase Shifter Using Stepped Impedance Open Stub and Coupled-Line With Weak Coupling

A novel hybrid coupler aiming for wide-band applications is proposed in this paper. This hybrid coupler consists of a broadband Wilkinson coupled-line power divider and an improved wide-band coupled-line phase shifter. Taking advantage of the coupled-line section, the power divider achieves both compact circuit configuration and wide-band performance. In lieu of patterned ground plane and lumped capacitors, the coupled-line phase shifter can be constructed on a single-layer printed circuit board for wide-band operation. For this proposed phase shifter, the scattering parameters (S-parameters) expressions are derived and the optimal structural design parameters for achieving zero reflection coefficients are highlighted. After carefully choosing the circuit parameters, a new wide-band hybrid is constructed by combining a power divider and the proposed phase shifter. To verify against the theoretical calculation in terms of S parameters and phase information, a hybrid operating at 3 GHz is designed, simulated, and fabricated through microstrip technology. Close agreement is obtained between simulation and measurement results.

Miniaturized Arbitrary Phase-Difference Couplers for Arbitrary Coupling Coefficients

High-performance dual-band Doherty power amplifler and non-uniform circularly polarized antenna array require impedance- transforming unequal dual-band 90 - branch-line couplers for power dividing and phase shifting in the feed networks. In this paper, an analytical design methodology of generalized impedance-transforming dual-band branch-line couplers for arbitrary coupling levels is proposed. The coupler features wide range of realizable frequency ratio, multiple ∞exible selections of open- or short-circuited and pi- or T-network topologies. For demonstration, four numerical examples with difierent parameters are presented. Furthermore, two microstrip couplers based on open-circuited pi- and T-network topologies were fabricated and measured. The measured results show good performance at dual 1.8/3.45GHz bands. The fractional bandwidths deflned by the ∞uctuation of the coupling level and the phase difierence less than §0:5dB and §5 - are up to 17% and 18%, 18% and 2% for open-circuited pi- and T-network topologies, respectively.

A novel wide-band hybrid coupler using coupled-line power divider and improved coupled-line phase shifter

Abstract A novel arbitrary asymmetric branch-line coupler structure terminated by one group of complex impedances is proposed. Two left ports of the proposed branch-line coupler are terminated by equal arbitrary complex impedances, and the other two right ports are terminated by equal real impedances. Arbitrary power division ratios are feasible for the proposed structure. Using rigorous even- and odd-mode analysis and scattering parameters theory based on complex impedances, the closed-form design formulas for designing the proposed branch-line coupler is obtained. To validate the proposed structure and the given design equations, a microstrip branch-line coupler operating at the center frequency of 2.5GHz and terminated by 20 and 30 − 6j Ohm impedances is designed, simulated and measured. There is a good agreement between the simulated and measured results.

Generalized Impedance-Transforming Dual-Band Branch-Line Couplers for Arbitrary Coupling Levels

A simple and analytical design methodology for a novel planar four-port structure to implement power divider (PD) or balun with variable power division is proposed in this paper. It consists of two difierent 3dB branch-line couplers and one coupled-line phase shifter whose length can be changed to implement variable power division. Difierent from the previous designs, the power divider and balun with variable power division can be realized in only one circuit by changing the electrical length µ0 of the coupled line when the impedance ratio g is selected. According to the ABCD parameters and linear algebra calculation, closed-form mathematical equations for the circuit electrical values and scattering parameters can be obtained. A prototype with this proposed circuit, operating at 2GHz, has been designed and fabricated using microstrip technology. Good agreements between the calculated and measured results verify our design.

An Asymmetric Arbitrary Branch-Line Coupler Terminated By One Group Of Complex Impedances

In this paper, a novel substrate integrated waveguide (SIW) to substrate integrated coaxial line (SICL) transition using the 3dB SIW power divider (PD) and SIW 180 - phase shifter (PS) is proposed. The SIW-to-SICL transition realizes the easy integration of SIW, SICL, and active device in the same microwave communication system based on the substrate-integrated technology (SIT). To validate the design concept, the prototype has been fabricated and measured. Measurements are in good agreement with simulations, and shows that the SIW-to-SICL transition features ultra-low insertion loss lower than 0.25dB and with a fractional bandwidth over 10%.

A Novel Planar Structure for Implementing Power Divider or Balun with Variable Power Division

Abstract The purpose of this article is to propose a novel design method for miniaturized tri-band Wilkinson power dividers with independently controllable center frequencies and a simple structure. Different from the traditional circuit of tri-band power dividers using three-section transmission-line transformers, this proposed structure consists of three-section coupled lines and three isolation resistors. Due to flexible even- and odd-mode parameters and inherent small size features of parallel coupled lines, this compact divider not only provides arbitrary tri-band operation but also increases the degrees of freedom in determining isolation performances. Furthermore, the simplified design equations for electrical parameters are obtained, and several ideal examples are demonstrated for initial theoretical verifications. As a remarkable example, a compact microstrip power divider operating at three industrial, scientific, and medical bands, namely, (0.92, 2.45, and 5.8 GHz), is designed, fabricated, and measured. There are good return loss (lower than −15.9 dB), small insertion loss (better than −3.8 dB), and excellent isolation (larger than 23.18 dB) performances at these desired triple bands in both the calculated and measured results.