Miniaturization of Microstrip Branch-Line Coupler With Dual Transmission Lines

The dual transmission lines are proposed to replace conventional quarter-wavelength transmission lines for a compact microstrip branch-line coupler in this study. The developed coupler can be easily fabricated on the printed circuit board without lumped element; moreover, its size is greatly reduced compared to the conventional branch-line coupler. Furthermore, simulated and measured frequency responses match well to validate the proposed coupler with dual transmission lines.     

A Compact Slow-Wave Microstrip Branch-Line Coupler With High Performance

One compact slow-wave microstrip branch-line coupler is presented. The new structure not only effectively reduces the occupied area to 28% of the conventional branch-line coupler at 2.0 GHz, but also has high second harmonic suppression performance. The measured results indicate a bandwidth of more than 200 MHz has been achieved while the phase difference between S₂₁ and S₃₁ is within 90deg plusmn 1deg. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.     

Dual-Band, Unequal Length Branch-Line Coupler With Center-Tapped Stubs

A new dual-band branch-line coupler scheme is proposed based on the unequal length branch-line coupler structure and the center-tapped stub lines. The unequal length structure reduces the size of the dual-band branch-line coupler using center tapped stubs. Also, it offers the possibility of the stubless dual-band operation for some special cases, and the same phase relation can be obtained between the two output signals at the two frequency bands.     

A Novel Triple-Band Microstrip Branch-Line Coupler With Arbitrary Operating Frequencies

This letter presents a novel microstrip branch-line coupler operating in three frequency bands. The design methodology of the triple-band branch-line coupler is established by using a compensation technique to improve the matching property within each passband region. The proposed coupler with compact size is realized by folded microstrip open-circuited and short-circuited stubs. The measured, full-wave simulated and equivalent-circuit modeled results illustrate good agreement among them, which validates the design method and shows the advantages of deep rejection between each operating frequency, and the dc grounded input and output ports.      

Synthesizing Microstrip Branch-Line Couplers With Predetermined Compact Size and Bandwidth

A new method for designing the microstrip branch- line couplers with predetermined compact size and bandwidth is proposed in this paper. With the proposed approach, the size of the quarter-wavelength transmission line in the branch-line coupler can be reduced greatly. In addition, the proposed couplers can be easily fabricated on the printed circuit board without any lumped element. A chart concludes the relationship between bandwidth and size reduction rate. It shows that open stubs with low impedance perform better than those with high impedance; moreover, the more open stubs with low impedance utilized, the broader the bandwidth will be. Furthermore, the measured frequency responses show good agreement with the theoretical results.     

一种新型小型化双频分支线耦合器的设计

设计了一款新型的小型化双频分支线耦合器。通过在端口处加载一段扩展的传输线实现分支线耦合器的双频工作。使用微带过渡结构连接不同介质层中的两个微带线电路以降低耦合器的尺寸。利用传输线理论将传统的λ/4 传输线等效为T 型传输线结构,并将端口处的扩展部分进行折叠处理,达到进一步缩减器件尺寸的目的。本文设计了一个工作频率在0. 97/1. 8GHz 的双频分支线耦合器,并进行实物加工,仿真结果性能良好,实测与仿真数据非常吻合。     

具有谐波抑制特性的小型化分支线耦合器

提出了一种具有谐波抑制特性的小型化分支线耦合器。通过分析枝节加载传输线的传输特性,发现可以采用小型化的枝节加载传输线去等效替换传统分支线耦合器中的四分之一波长传输线,此方法可以极大地减小分支线耦合器的电路尺寸。同时,由于枝节引入传输零点,耦合器的谐波响应也得到抑制。为了验证理论分析的有效性,建立了等效电路模型和传输线方程,对电路性能进行分析,最后进行了仿真以及实验验证。     

A Stub Tapped Branch-Line Coupler for Dual-Band Operations

This letter presents a stub tapped branch-line coupler for dual-band applications. In the new design, a tapped stub is used to realize 90deg phase change at two frequencies. Both the characteristic impedance and the length of the proposed branch lines are adjusted accordingly compared with the conventional structure. Explicit design equations are derived using the ABCD-matrix. To verify the design concept, a microstrip coupler operating at 0.9 and 2GHz is fabricated and measured on a Rogers' RO4003 board     

毫米波空间行波管输能结构的设计

本文采用分段设计的方法,将一个完整的盒型窗输出耦合结构分解为三部分,然后对这三部分分别进行匹配设计,最后将设计好的各部分组合成整体。利用HFSS软件对各段结构以及整体结构进行了仿真,结果表明这样设计出的盒型窗输出耦合结构在工作频带内可以很好的满足设计要求。     

Line Width and Bandwidth of Millimeter-Wave Resonance Isolators

A theoretical derivation is made of bandwidth as a function of resonant frequency of a single crystal ferrite resonance isolator at millimeter wavelengths. The derivation takes into account the ferrite isolator as a bounded system. Using the derived relation of bandwidth and resonant frequency, and Kittel's relation between resonant frequency and applied field, equations are derived which relate line width to resonant frequency, line width to the applied magnetic field, and line width to frequency bandwidth. These resulting equations are compared with experimental data obtained with a single crystal barium ferrite isolator from 58 to 59 kMc. The theoretical relations agreed closely with the experimental data within the accuracy of the measuring equipment at these frequencies. In general, the results showed that for small frequency ranges (1 kMc) bandwidth and line width increase almost linearly with frequency, bandwidth and line width are linearly related, and line width is a fairly complicated but increasing function of applied field.     

Gold-Plated Micromachined Millimeter-Wave Resonators Based on Rectangular Coaxial Transmission Lines

Resonators based on microfabricated rectangular coaxial (recta-coax) transmission lines are presented. The resonators were fabricated using a multilayered nickel electroplating process that enables the fabrication of three-dimensional structures. As a method to improve performance, gold was plated on the resonators using an electroless process. A model for predicting the effect of the plating on a resonator quality (Q) factor is presented and verified by measurements. Measured resonators show that the plating can increase the Q factor of nickel resonators by over 50% at frequencies above 44 GHz. Utilizing gold plating, 50-Omega resonators are demonstrated at 44 and 60 GHz with unloaded Q factors of 213.1 and 242.3, respectively     

基于小孔耦合的毫米波宽带定向耦合器研究

基于小孔耦合理论和电磁场全波分析法,根据正向叠加和反向抵消原则,确定耦合孔半径、间距和数量,并通过HFSS 软件进行仿真设计,实现了毫米波段定向耦合器的工作频段展宽;提出了一种新颖的波导腔体三层结构设计方案,解决了波导接触面缝隙切割电流引起的毫米波辐射问题,实现了波导无辐射装配,提高了器件的稳定性和可靠性。成功研制的毫米波W 波段宽带、高耦合度定向耦合器在88 ~102 GHz 频段传输损耗0.6 dB,两路输出幅度误差优于±0.3 dB,隔离度大于18 dB。     

Design of Multipassband Microstrip Branch-Line Couplers With Open Stubs

The microstrip branch-line coupler with multiple passbands is proposed; moreover, the design equations are provided in this paper. In order to obtain multiple passbands, open stubs are added to the conventional branch-line coupler's ports; in addition, these open stubs' impedance and electrical length need to be properly chosen. The proposed couplers can be easily fabricated on the printed circuit board without any lumped element. The agreement between measured results and the theoretical prediction validates the feasible configuration of the proposed coupler.     

Analysis and Design of Bridged NRD-Guide Coupler for Millimeter-Wave Applications

A new nonradiative-dielectric (NRD)-guide directional coupler using two NRD waveguides interconnected with a bridge is proposed and demonstrated. Propagation constants of the bridged NRD-guide couplers are investigated with an electric-field integral-equation method, and modeling results show that there is a maximum of coupling coefficient when the thickness of the bridge is made around 0.68 of the plate separation. In this case, the coupling length is reduced approximately 60% and the bandwidth under the tolerance limits of$pm$0.5 dB of deviation for 3-dB coupling is nearly doubled with reference to its conventional counterparts. The use of a bridge not only improves the mechanical stability, but also makes the coupler performance reproducible. Experimental prototypes are fabricated with two 90$^circ$elbow bends that are used for the arms and the bridge-connected coupler section is terminated at both ends by tapered half-circle sections. A calibration procedure is used to remove mismatch effects between the NRD-guide and the rectangular waveguide in the measured results. Advantages of the new coupler as a passive component are shown for millimeter-wave integrated circuits.     

Silicon Micromachined W-Band Hybrid Coupler and Power Divider Using DRIE Technique

In this letter, a silicon micromachined W-band hybrid coupler and a power divider using deep-reactive ion etching (DRIE) technique are presented. They are designed in the H-plane of rectangular waveguide to utilize DRIE technique. The hybrid coupler adopts a ridged waveguide 90deg phase shifter and a joint waveguide. The power divider utilizes a T-shape configuration. The simulated and measured response of each circuit are presented in this letter where good agreement between them is achieved. Then, the measured combining efficiency is reported by cascading the power divider and the hybrid coupler.     

Ultra-wide Bandwidth Inter-Chip Interconnects for Heterogeneous Millimeter-Wave and THz Circuits

Heterogeneous chip-to-chip interconnects with low loss and ultra-wide bandwidths have been demonstrated. Coplanar waveguide-based interconnects between GaAs and Si die have been fabricated and characterized and the results compared to expectations from full-wave electromagnetic simulation. Broadband transmission characteristics were obtained, with insertion losses below 0.3 dB at 100 GHz and below 0.8 dB at frequencies up to 220 GHz demonstrated experimentally. The measured return loss exceeded 11.5 dB at all frequencies up to 220 GHz. The interconnects offer low latency, with a measured group delay of 0.69 ps. The measured results are in good agreement with full-wave simulations, indicating that the measured results do not suffer from significant impairments compared to theoretical predictions. The demonstrated interconnects offer an alternative to conventional approaches to millimeter-wave circuit and system integration, by enabling the compact realization of circuits in the microwave, millimeter-wave, sub-millimeter-wave, and THz frequency regimes in heterogeneous device technologies with very low chip-to-chip insertion loss.     

A Novel 94-GHz MHEMT Resistive Mixer Using a Micromachined Ring Coupler

In this letter, we present a high performance 94-GHz millimeter-wave monolithic integrated circuit resistive mixer using a 70-nm metamorphic high electron mobility transistor (MHEMT) and micromachined ring coupler. A novel three-dimensional structure of a resistive mixer was proposed in this work, and the ring coupler with the surface micromachined dielectric-supported air-gap microstrip line structure was used for high local oscillator/radio frequency (LO–RF) isolation. Also, the LO–RF isolation was optimized through the simulation. The fabricated mixer has excellent LO–RF isolation, greater than 29 dB, in 2-GHz bandwidth of 93–95GHz. The good conversion loss of 8.9dB was measured at 94GHz. To our knowledge, compared to previously reported W-band mixers, the proposed MHEMT-based resistive mixer using a micromachined ring coupler has shown superior LO–RF isolation and conversion loss.