Observed properties of an acoustic-surface-wave multistrip coupler

The properties of an acoustic-surface-wave multistrip coupler constructed on YZ LiNbO3 are reported. The device was made by standard photolithographic techniques and consisted of 100 separate aluminium strips at a repeat distance of 16 ?m. Over a bandwidth of at least 30% centred at 86 MHz, the coupling factor was less than 1 dB with a directivity of approximately 30 dB. Some applications of the coupler are discussed; in particular, it is shown that the device may be used as a filter to discriminate between bulk and surface acoustic waves.     

A VHF Microstrip Antenna With Wide-Bandwidth and Dual-Polarization for Sea Ice Thickness Measurement

A VHF microstrip patch antenna was developed to achieve a bandwidth of 45 MHz (30%) from 127 to 172 MHz with dual-linear-polarization capability. This microstrip antenna, having a size of 117 cm times 117 cm times 27 cm, used low-dielectric-constant foam substrates and dual-stacked patches with capacitive probe feeds to achieve the required wide bandwidth. Four such capacitive feeds were used to achieve dual polarizations with less than -20 dB of cross-polarization level. Twenty-four shorting pins were uniquely used here on the lower patch to achieve 40 dB of isolation between the two polarization ports. This antenna has a measured gain of 8.5 dB at 137 MHz and 10.3 dB at 162 MHz. One advantage observed here at the low frequencies of VHF is that more electrical structures can be easily integrated into the microstrip antenna to improve its performance.     

Compact microstrip parallel coupler with high isolation

A compact microstrip parallel coupler with high isolation is presented. Adopting the reflected power canceller approach, the developed coupler with dual transmission lines not only effectively enhances the directivity of the coupler, but also has compact size. For verification purposes, a proposed parallel coupler is fabricated and measured at 915 MHz. The proposed parallel coupler can obtain excellent isolation of -65 dB and directivity of -47.7 dB at 915 MHz. Simulated results are in good agreement with measured results, which verified the reliability of the designed coupler.     

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.     

Development of a Compact Broadband Folded Hybrid Coupler on Multilayer Organic Substrate

We present the design and fabrication of a wide bandwidth folded hybrid coupler on a multilayer organic substrate. The coupler is designed with a tandem connection of two 5-sections with a coupling of 8.34 dB. We propose a novel center coupling structure that achieves tight coupling while being compatible with printed circuit board fabrication processes. The folded coupler achieves a bandwidth of 2 to 18 GHz with 42% reduction in size.      

A 3-dB Quadrature Coupler Using Broadside-Coupled Coplanar Waveguides

A 3-dB quadrature coupler which combines the advantages of broadside-coupling and coplanar waveguide structure suitable for a single-layer printed circuit board (PCB) circuit design is proposed. Compared to the recently published broadside-coupled structures, the proposed coupler can easily be realized in a single-layer substrate by using PCB manufacturing processes to eliminate the effects of uncertain factors from a multi-layer substrate. With the operation bandwidth ranging from 2.1 to 2.7 GHz, the measured return loss and isolation are all better than 19dB, and the insertion losses and relative phase difference between the direct and coupled ports are at 3.2 plusmn 0.1 dB and 90 plusmn 0.6deg, respectively. The dimension of the coupler is 2.1 cm times 1.9 cm.     

Folded Half Mode Substrate Integrated Waveguide 3 dB Coupler

In this letter, novel compact 3 dB double-slot and single-slot couplers are proposed and implemented based on folded half mode substrate integrated waveguide (FHMSIW). The size of the FHMSIW coupler is reduced by nearly 50% and 75% compared with half-mode substrate integrated waveguide coupler and substrate integrated waveguide coupler, respectively. Prototype couplers at X-band are fabricated and measured and good performance in bandwidth, insertion loss, and balance are achieved.      

30-GHz-Band Periodic Branching Filter Using a Traveling-Wave Resonator for Satellite Applications

A periodic branching filter consisting of three directional couplers, a traveling-wave resonator, and connecting waveguides is used as a band diplexer with a broad 3-dB bandwidth and sharp selectivity for a satellite communication system application. This paper describes a theoretical analysis, a design method, and experimental results for this periodic branching filter. The fabricated periodic branching filter for separating the 30-GHz frequency band 27.0-29.2 GHz into two subbands of equal 3-dB bandwidth of about 900 MHz has sharp frequency selectivity. Measured branching losses and relative delay time are 0.35-0.5 dB and 0.4 ns, respectively, within each frequency subband (f /sub 1,2/ /spl plusmn/ 300 MHz). The 96-g diplexer is made of thin-walled aluminum. Its size is 15 x 9 x 4 cm.     

Tunable characteristics of ferrite composite right/left handed coplanar waveguide coupled line coupler – Measurement and experimental verification

This paper presents the experimental verification of the tunable characteristics of a ferrite composite right/left handed coupled line coupler. The coupler is designed using two coupled CRLH-CRLH transmission lines. The coupler is designed to demonstrate equal through and backward coupling. The novel coupler has been designed and realized in coplanar waveguide configuration on a ferrite substrate. The tunable characteristics are achieved by changing the applied DC magnetic bias to the ferrite substrate. The measurement results reveal that the coupler’s fractional bandwidth can be tuned from 29% to 69% by varying the applied DC magnetic bias from 1000 Oe to 1750 Oe. Within the tunable bandwidth, the maximum backward coupling is −5 dB. The coupler has high forward coupling isolation, close to −30 dB at its centre operating frequency. In addition to its tuning capability, the coupler has the advantages of its compact size; it has the length of 11.5 mm and not-so-tight line separations of 2.5 mm. Furthermore the coupler only requires low DC magnetic bias.     

熔锥型宽带光纤耦合器的研究

为了探究非对称耦合器的特性, 利用具有折射率差异的两根光纤制作了宽带耦合器。采用数值计算模拟了不同折射率差光纤耦合器的光场分布以及输出光功率随拉伸长度的变化曲线, 并分析了两种宽带耦合器的带宽差异以及熔融度对功率转换比的影响; 采用光束传播法, 通过仿真模拟得到了理论带宽。结果表明, 耦合的功率转换比随两根光纤的不对称情况而变化, 功率转换比调节到耦合器分束比的大小时, 耦合器带宽最宽; 熔融度对宽带耦合器分束比有一定的调节作用; 3dB光纤耦合器在C+L波段波长响应平缓, 带宽范围达到150nm; 分束比3:7和1:9的耦合器带宽范围分别是210nm和330nm; 分束比1:99的耦合器带宽范围是420nm。此研究结果对制作非对称宽带耦合器提供了参考依据。     

C 波段LTCC 无通孔微型Lange 耦合器的研究

研究了一种C波段LTCC无通孔微型Lange耦合器,其结构紧凑,尺寸小。LTCC叠层技术是实现高性能、高可靠、微型化微波元件的主流技术之一,尤其是在提高电路集成度方面。Lange耦合器由于其特殊的结构使得其可以实现宽频带、高性能。设计、制作了一种中心频率为4GHz的宽带3dB Lange耦合器,尺寸仅为7.0mm×2.2mm×1.4mm。在2.0～6.0GHz频带内测试结果如下:插入损耗<0.3dB,反射损耗<21dB,隔离>27dB,相位平衡<90±3°,最大承受功率<40W(连续波)。测试与仿真结果较吻合,验证了研究结果的一致性。     

Super-Compact Substrate Integrated Waveguide Cruciform Directional Coupler

A super-compact substrate integrated waveguide (SIW) directional coupler is proposed and demonstrated. This coupler consists of a simple cross-over of two SIW sections with two inductive metallic posts in a square junction, showing a cruciform. Attractive features including compact size and planar form make this coupler structure easily integrable in microwave and millimeter-wave planar circuits, especially in beam-forming networks. A 3-dB coupler operating at 24GHz is designed using HFSS, fabricated and measured. Characteristics of 15dB isolation and 90deg phase shift between the output and coupled ports are achieved over 18% bandwidth. Design considerations and simulated as well as measured results are presented and discussed.     

MMIC implementation of non-reciprocal couplers using pHEMT devices

The distributed amplifier topology has been adapted to form a non-reciprocal coupler which is small in size and broadband. The coupler has been implemented in MMIC form using pHEMT devices and a coupling factor of 5 dB is demonstrated over 2-20 GHz bandwidth.     

High-speed modulation of an electrooptic directional coupler

A LiNbO3:Ti directional coupler driven by an RF signal has been tested at 1.06 μm over a large modulation bandwidth. An analytical model has been developed leading to simple usable expressions to describe the theoretical dependence of the frequency spectrum of sinusoidally modulated light. The frequency response has been measured with a scanning Fabry-Perot and also with a high-speed photodiode. Both methods provided results which are in good agreement. The 9 mm long switch exhibited a 2.5 GHz bandwidth; a 16 dB extinction ratio has been achieved with a driving power of approximately 50μW/MHz. The confirmation of practical modulation response expressions shows the advantage of the optical spectrum observation, which is a very simple measurement method without any bandwidth limitation. In addition, this method has the advantage of remaining quite accurate even for large modulation signals.     

一种带有反相单元的小型化宽带双面平行带线混合环

本文研究了一种利用双面平行带线(Double-Sded Parallel Strip Line,DSPSL)反相器和加载微带分支电路来设计的混合环.文中首先介绍了设计理论和思路,并给出了设计实例和测试结果.结果表明:该混合环的尺寸可缩小为常规混合环的11%,相对带宽达到了82%,中心频率点处反射损耗在-20dB以下,通...     

A comparison of power requirements of traveling-wave LiNbO3optical couplers and inteferometric modulators

It is shown that a coupler and interferometer may be considered two extremes of a generalized two-guide coupler device in which electrode length is less than a coupling length. For electrode lengths less than half of a coupling length, the generalized device looks more like an interferometer than a coupler. The impedance and electrical loss of asymmetric-stripe and coplanar-waveguide transmission lines on LiNbO3for thick as well as thin electrodes are then presented. The effects of the electrical loss on the bandwidth and drive requirements of traveling-wave LiNbO3couplers and interferometric devices are discussed, and it is shown that electrical loss in the transmission line is more detrimental to a coupler than to an interferometer. These results are then used to compare the drive power requirements of coupler and interferometric devices, and it is shown that for the same bandwidth and same optical guide dimensions, an interferometric device with a coplanar transmission line can require a lower drive power than a coupler with an asymmetric-stripe line.     

Wide-band rotary transformer—Unbalanced current analysis

Performance of a wide-band rotary transformer with approximately 1000:1 bandwidth (80 kHz-80 MHz) is described. A previous paper [1] gave theoretical analysis and experimental results based upon lossless balanced, transmission line theory. This paper extends the results to the case of a shielded transformer, and uses a combination of balanced and unbalanced line theory to account for losses and predict frequency response. Theoretical results are confirmed by data measured on a prototype coupler.     

Miniaturised broadside coupler using coupled slow-wave artificial lines

A miniaturised broadside coupled-line coupler is presented. The coupler is fabricated on a six-layered printed circuit board and consists of a 90° coupled slow-wave artificial transmission line section. Compared with previous works on printed circuit boards, the proposed design features the smallest occupied size. It also demonstrates a comparable operating bandwidth of 85%. The design concept, methodology and results are investigated.     

A 3-dB Quadrature Coupler Suitable for PCB Circuit Design

A quadrature 3-dB coupler, which combines the advantages of a coplanar waveguide and microstrip line structure suitable for single-layer substrate printed circuit board (PCB) circuit design is proposed. As compared to the conventional Lange coupler, the proposed coupler with the advantages of increasing the coupled linewidths and coupling spacing without using extra bonding wires can solve the drawbacks of Lange coupler. In addition, the proposed structure can easily be realized in a single-layer substrate by PCB manufacturing processes to eliminate the effects and uncertain factors from a multilayer substrate. Good agreements between the simulation and measurement in the frequency range from 0.45 to 5 GHz can be seen. With the operation bandwidth ranging from 1.8 to 2.8 GHz, the measured results of the return loss are better than 18.2 dB and insertion losses of coupled and direct ports are approximately$hbox 3 pm hbox 0.1~hbox dB$; the relative phase difference is approximately 89.8$^circ$. The dimension of the circuit is 2.7 cm$times,$1.6 cm$times,$0.08 cm.     

Synthesis of Symmetrical TEM-Mode Directional Couplers

Exact synthesis procedures are derived for symmetrical three-section and five-section TEM-mode directional couplers. These synthesis procedures are based on the equivalence between the theory of directional couplers and stepped quarter-wavelength filters as previously described by Levy and Young. Explicit formulas for the parameters of three-section couplers are presented. A realizable insertion-loss function is derived for the five-section coupler resulting in an equal-ripple response. Although this function has an equal-ripple characteristic, it is not expressible in terms of Chebyshev polynomials. Results obtained for the five-section coupler show considerable improvement in bandwidth over a three-section coupler. For example, a five-section coupler of -3 /spl plus mn/ 0.5 dB has a bandwidth of 9.6:1 as compared with 5.8:1 for a three-section coupler of -3 /spl plus mn/0.5 dB. A five-section coupler of -10 /spl plus mn/ 0.5 dB was designed on this theoretical basis for the 555-4000 Mc band, and the measured shows good agreement with the theoretical coupling sponse, yielding a minimum directivity of 18.0 dB at 3.7 Gc.