Shao Yong Zheng

Broadband Phase Shifter Using Loaded Transmission Line

This letter presents a novel loaded transmission line, which has a constant phase shift over a wide bandwidth, referenced to a uniform transmission line. Compared with the conventional coupled line phase shifter, the configuration shows good performance with simplicity in both design and fabrication. The optimal design parameters for different phase shift values up to 120° are also presented to allow for a quick design process. To verify the configuration, a 90° phase shifter using a T shaped open stub loaded transmission line is designed, fabricated and measured. Excellent performance is achieved with small insertion loss and phase deviation over a bandwidth of 82%.

An Analytical Design Method for a Novel Dual-Band Unequal Coupler With Four Arbitrary Terminated Resistances

A new design concept of a generalized dual-band branch-line coupler with unequal power division and four arbitrary terminated resistances is proposed in this paper. By using an external frequency-dependent impedance transformer, a novel dual-band branch-line coupler is obtained with a detailed analytical design method. For ease of design, maximum power-dividing ratio with varying frequency ratio for different terminated impedance values is provided. Owing to the additional design freedom, the calculation of parameters becomes much more flexible. Finally, for experimental validation and convenient measurement, a dual-band unequal microstrip branch-line coupler with four standard ports is designed, fabricated, and measured. Good agreement between the simulated and measured results can be observed.

Dual-Band Rectangular Patch Hybrid Coupler

This paper presents, for the first time, the design of a rectangular patch hybrid coupler that can operate at two arbitrary frequency bands with the same quadrature phase relation between the two outputs. The design procedure of the hybrid coupler is presented. For demonstration, a dual-band rectangular patch hybrid coupler is designed to operate in the 2.4- and 5-GHz bands corresponding to the IEEE 802.11 a/b/g bands. The measured result shows 9.3% and 18.2% bandwidth for the lower and upper frequency bands.

Reconfigurable RF Quadrature Patch Hybrid Coupler

A highly reconfigurable radio frequency patch hybrid coupler with a simple topology is presented for the first time. Due to the introduction of lumped equivalent circuit and flexibility of varactor loaded patterned ground plane, the complex reconfigurability in port arrangement and coupling coefficient can be implemented. Varying the capacitance across different planes allows the electronic switching between different operating modes of the patch hybrid coupler. When the auxiliary patch and patterned ground plane is placed closer to the two output ports, tunable coupling coefficient can also be implemented by changing the capacitance. This results in wide band reconfigurability for the coupling coefficient range. For demonstration purposes, a patch hybrid coupler operating at 2.4 GHz is designed and measured to validate the port reconfigurable concept. Also, a patch hybrid coupler with tunable coupling coefficient operating at 3.5 GHz is designed, fabricated, and measured. This circuit gives a reconfigurable coupling coefficient ranging from -4.2 to -10 dB while maintaining good performance.

Size-Reduced Rectangular Patch Hybrid Coupler Using Patterned Ground Plane

This paper presents, for the first time, the design of a size-reduced rectangular patch hybrid coupler. Different types of compact rectangular patch hybrid couplers with different ground plane patterns are described. For demonstration, two compact rectangular patch hybrid couplers are designed to operate at 3.5 GHz. They are measured to have 30.1% and 33.3% bandwidth with 67.3% and 72.3% size reduction compared with the optimized one without patterned ground plane.

Circular Sector Patch Hybrid Coupler With an Arbitrary Coupling Coefficient and Phase Difference

This paper presents, for the first time, a patch coupler configuration that can be designed with an arbitrary coupling coefficient and phase difference at the output ports. Four circular sector patches are combined to form the patch coupler resulting in ease of design and fabrication. To demonstrate and verify this, a patch quadrature coupler configuration is proposed to realize a wide range of coupling coefficients by adjusting the radii of each quadrant. To extend this concept of an arbitrary coupling coefficient for 180

Quasi-Arbitrary Phase-Difference Hybrid Coupler

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Multifolded bandwidth banch line coupler with filtering characteristic using cou-pled port feeding

patch couplers, different patterns are etched underneath the circular patch to realize the required power division ratio while maintaining good impedance matching and desired phase characteristics at the input/output ports. Finally, a circular patch coupler is demonstrated to exhibit an arbitrary phase difference between output ports maintaining an equal power division.

Dual-Band Hybrid Coupler With Arbitrary Power Division Ratios Over the Two Bands

Previous hybrid couplers have output phase difference that have either been 0°, 90°, or 180°. Other phase differences could only be realized using additional phase-shift elements. This increased circuit size and cost, and also degraded overall performance due to interconnecting mismatch losses. The proposed uniplanar arbitrary phase-difference coupler eliminates these additional components, thereby maintaining small size and good performance. Theoretical analysis is presented here together with measured results for two microstrip couplers for verification.

Compact Filtering Rat-Race Hybrid With Wide Stopband

A new uni-planar structure branch-line coupler with broad bandpass response is proposed. Single section branch line couplers (SSBC) are popular due to their simplicity and ease of use but sufier from narrow return loss bandwidth and poor out of band rejection characteristics. The work presented here overcomes these limitations with the use of coupled port feeding. Through the study of input impedance of feeding network and single section branch line coupler, the bandwidth of the new coupler increased by almost 6-times. In addition, the coupler exhibited band-pass flltering characteristics. Measured results exhibited low insertion loss (• 4-dB), small magnitude difierence (• 1-dB), good return loss and isolation (‚ 10-dB) and small phase variation (90 - § 5) within the passband. A measured bandwidth of 58% was achieved with this single section coupled port fed branch line coupler at a centre frequency of 1-GHz. Its two output ports achieved rejection levels better than 25dB in the stopband.