Coupled Microstrip Research Articles

A Compact, High Power Capable, and Tunable High Directivity Microstrip Coupler

A coupler is an indispensable component to sample the forward and reflected power for the real-time radio frequency (RF) power monitoring system. The directivity of a coupler is a critical factor to achieve accurate RF power measurements. This paper proposes a microstrip coupler with a tunable high directivity circuit to accurately measure the reflected RF power. The directivity tuner composed of passive components adjusts phase and amplitude of the coupled RF signal, and cancel out the leakage signal from the RF input port at the coupled reflection port. The experimental results, which agree with simulation results, show that the microstrip coupler with the directivity tuner circuit has a compact size (~ 0.07 λg x 0.05 λg), high power capability (up to 1 kW), and high directivities (more than 40 dB) at operating frequency bands (f = 297.3 MHz, 400 MHz, and 447 MHz, respectively) for magnetic resonance imaging (MRI) applications.

Broadband capacitively grounded coplanar to coupled microstrip transition for planar microwave photonic components

Broadband transitions are presented in this paper for capacitively grounded coplanar waveguide to coupled microstrip (CMS) lines. These transitions are realized on both thick Rogers RO3003 substrate (thickness of 10 mils) and a thin benzocyclobutene (BCB) polymer film (thickness of 20 µm). A flat bandwidth of 4–20 GHz and 3.2 to over 40 GHz are measured for the RO3003 and BCB polymer substrates, respectively. These performances are obtained without making via-hole in the substrate or patterning the bottom ground plane, which makes this broadband transition easier to fabricate compared with the via-hole-based grounded CPW–CMS transitions.

Compact diplexer using microstrip half‐ and quarter‐wavelength resonators

This Letter presents a compact microstrip diplexer. The high-frequency signal path is constructed by two electrically-coupling half-wavelength resonators, its external coupling adopts the tapped line structure. The low-frequency signal path is formed by two magnetically-coupling quarter-wavelength resonators, its external coupling is accomplished by microstrip coupling lines, which are formed from the tapped line structure and resonator of the high-frequency signal paths. The novel combination of the two signal path removes the need of T-junction in conventional diplexers. Meantime, the coupling strength of the two pass bands at the input port can be separately designed. A diplexer with Chebyshev frequency response at both signal paths with the central frequencies of 1.8/2.4 GHz is designed, fabricated and measured. The measured results give a good agreement with the simulated ones, which verifies the effectiveness of the diplexer.

Dual-Band Proximity Coupled Feed Microstrip Patch Antenna with ‘T’ Slot on the Radiating Patch and ‘Dumbbell’ Shaped Defected Ground Structure

<p>This paper presents Dual-Band proximity coupled feed rectangular Microstrip patch antenna with slots on the radiating patch and Defected Ground Structure. Initially a simple proximity coupled feed rectangular Microstrip patch antenna resonating at 2.4 GHz is designed. Etching out a ‘Dumbbell’ shaped defect from the ground plane and ‘T’ shaped slot from the radiating patch of the proximity coupled feed rectangular Microstrip patch antenna, results in a Dual-Band operation, i.e., resonating at 2.4 GHz and 4.5 GHz; with 30.3 % and 18.8% reduction in the overall area of the patch and the ground plane of the reference antenna respectively. The proposed antenna resonates in S-band at frequency of 2.4 GHz with bandwidth of 123.6 MHz and C-band at frequency of 4.5 GHz with bandwidth of 200 MHz, and a very good return loss of -22.1818 dB and -19.0839 dB at resonant frequency of 2.4 GHz and 4.5 GHz respectively is obtained. The proposed antenna is useful for different wireless applications in the S-band and C-band.</p>

Bandwidth Enhancement of Rectangular Microstrip Patch Antenna using Defected Ground Structure

<p>This paper presents the bandwidth enhancement of a Proximity Coupled Feed Rectangular Microstrip Patch Antenna using a new Defected Ground Structure - an ‘inverted SHA’ shaped slot on the ground plane of the proximity coupled feed rectangular Microstrip patch antenna. The parameters such as Bandwidth, Return loss, VSWR and Radiation efficiency are improved in the proposed antenna than simple proximity coupled feed rectangular Microstrip patch antenna without Defected Ground Structure. A comparison is also shown for the proposed Microstrip patch antenna with the antenna structure without Defected Ground Structure. The proposed antenna resonates in S-band at frequency of 2.4 GHz with bandwidth of 180 MHz. A very good return loss of -47.9223 dB is obtained for the Microstrip patch antenna with an ’inverted SHA’ shaped Defected Ground Structure. Implementing an ‘inverted SHA’ shaped defect in the ground plane of the proximity coupled feed rectangular Microstrip patch antenna results in 5.3% improvement in bandwidth with 16.01% reduction in the overall area of the ground plane as compared to the Microstrip patch antenna without Defected Ground Structure.</p>

Rapid simulation‐driven design of miniaturised dual‐band microwave couplers by means of adaptive response scaling

One of the major challenges in the design of compact microwave structures is the necessity of simultaneous handling of several objectives and the fact that expensive electromagnetic (EM) analysis is required for their reliable evaluation. Design of multi-band circuits where performance requirements are to be satisfied for several frequencies at the same time is even more difficult. In this work, a computationally efficient design of dual-band microstrip couplers is demonstrated by means of an adaptive response scaling (ARS) technique. ARS is a surrogate-assisted method that exploits a fast surrogate of the high-fidelity EM-simulation model of the coupler at hand constructed from its corrected equivalent circuit. ARS identifies nonlinear frequency and amplitude response scaling that accommodates the misalignment between the low- and high-fidelity models. Due to exploiting the knowledge embedded in the low-fidelity model ARS surrogate exhibits excellent generalisation capability. It is demonstrated here by optimisation of a dual-band microstrip coupler with enhanced bandwidth, working at 1 GHz and 2 GHz frequencies. The optimised design has been obtained at the cost of just a few high-fidelity EM simulations of the structure. Numerical comparisons indicate superiority of ARS over competitive surrogate-assisted techniques. Experimental validation is also provided.

Coupled microstrip line Wilkinson power divider with open‐stubs for compensation

Coupled microstrip line section is a well-known technology for various circuits miniaturisation. Because the phase velocity difference of coupled microstrip line section exists in practical circuit, compensation method is needed to maintain circuit performance. In this Letter, extra open-stubs are newly inserted between coupled microstrip line section and two output ports for compensation. Compared with previous work, by using open-stubs, a novel and flexible compensation method is newly presented, where, both Γev and Γod are adjusted for compensation at the same time, the proposed circuit not only provides simple structure and easy fabrication but also compensates arbitrary coupling strength without soldering parasitic effect in high frequency operation. Through even- and odd-mode analysis, design equations are derived and discussed in Smith chart. In experiment, one circuit was fabricated, the measurement results showed good agreement with theoretical results.

Low-cost surrogate-assisted statistical analysis of miniaturized microstrip couplers

ABSTRACTIn this work, a technique for low-cost yield estimation of compact microwave couplers has been presented. The analysis is carried out at the level of a fast surrogate model representing selected characteristic points of the coupler response that are critical to determine satisfaction/violation of the design specifications. Due to less nonlinear dependence of the characteristic points on geometry parameters (compared to the original response, i.e. S-parameters vs. frequency), a small number of training points is necessary to setup the surrogate. Our approach is demonstrated using a compact rat-race microstrip coupler. Numerical verification involving direct Monte Carlo analysis of the EM simulation model of the coupler confirms reliability of our approach.

기판 크기가 H-평면 5소자 선형 개구면 결합 패치 배열 안테나의 방사 특성에 미치는 영향

개구면 결합 마이크로스트립 패치 안테나(aperture coupled microstrip patch antenna; ACMPA)를 단위 소자로 가지는 H-평면 5소자 선형 배열 안테나의 기판 크기 변화가 방사 특성에 미치는 영향에 대하여 연구하였다. 단일 ACMPA 와 ACMPA를 단위 안테나로 가지는 H-평면 5소자 선형 배열 안테나의 전방방사 이득이 최대가 되는 패치 중심에서 E 평면 방향의 기판 가장자리까지의 길이(dSUBE/SUB)와 H 평면 방향의 기판 가장자리까지의 길이(dSUBH/SUB)는 서로 같음을 볼 수 있었다. 또한 선형 배열 안테나와 단일 ACMPA의 전방방사 이득이 최소가 되는 dSUBE/SUB와 dSUBH/SUB도 거의 같음을 볼 수 있었다. H-평면 선형 배열 안테나의 기판 크기에 따른 전방방사 이득의 변화는 dSUBE/SUB에 의해서 큰 영향을 받음을 볼 수 있었다. H-평면 선형 배열 안테나의 방사 이득이 최적화된 기판 크기는 선형 배열 안테나를 구성하는 단위 안테나의 전방방사 이득이 최적화된 기판 크기로부터 도출할 수 있음을 볼 수 있었다.

Electrodynamic Analysis and Synthesis of Shielded Coupled Microstrip Lines

We develop the mathematical model of shielded coupled microstrip lines on the basis of a numericalanalytical method for calculating eigenwaves of strip structures, which was earlier proposed by the author. This model allows one to solve the problems of both analysis and synthesis of such lines with high speed and accuracy. The dependence of the main electrodynamic parameters of such lines on the shield sizes is studied. The possibility to equalize the slowing factors of the inphase and antiphase waves is confirmed in a wide range of variations in the physical and geometrical parameters of the lines. The results of calculating the line sizes, which are determined on the basis of solving synthesis problems under the condition of equality of the slowing factors, are presented.

DESIGN OF CONTINUOUS BEAM STEERABLE AND SCALABLE UNIT MODULE FOR WIRELESS POWER TRANSMISSION USING INJECTION-LOCKED OSCILLATOR ARRAY

Long-range wireless power transmission (WPT) is implemented with the beamforming using the phased array transmitter technology, which has been extensively applied in the radar systems. The cost of a conventional phased array transmitter module scales up in proportion to the number of antenna elements, as the massive number of transmit channels results in the increasing complexity of hardware and feeding antenna elements. Besides, the conventional phase-shifting transmitter architecture has lower DC to RF power conversion efficiency due to the insertion loss of power combining network at microwave frequency. In this paper, the concept of spatial power combining transmitter is utilized, and the upconversion circuit is greatly simplified to an injection locked oscillator. Our WPT system is implemented with the technology of oscillator array antenna at 2.4 GHz, which converts DC power to RF power and radiates into the air directly. The feedback voltage controlled oscillator (VCO) is implemented as the microwave source using a off-the-shelf bandpass filter, and the external signal is injected to the oscillator via a microstrip coupler. The oscillator core shows the DC-to-RF conversion efficiency of 45.87% with the injected power of 0 dBm at 2.4 GHz. Then the digital phase shifter is used to phase shifting the injected signal to extend the beam coverage. From the link budget analysis, the overall DC-to-DC efficiency of our highly-integrated system shows 1.5 times (0.22%) of the conventional phased array (0.15%) when the separation between the transmit array and the receive horn antenna is 1.2 meters. Therefore, as an modularized array, the proposed system demonstrates the promising capability of upscaling to an efficient massive array with greatly reduced bill-of-materials (BOM).

An ANN-Based Synthesis Model for Parallel Coupled Microstrip Lines with Floating Ground-Plane Conductor and Its Applications

To directly obtain physical dimensions of parallel coupled microstrip lines with a floating ground-plane conductor (PCMLFGPC), an accurate synthesis model based on an artificial neural network (ANN) is proposed. The synthesis model is validated by using the conformal mapping technique (CMT) analysis contours. Using the synthesis model and the CMT analysis, the PCMLFGPC having equal even- and odd-mode phase velocities can be obtained by adjusting the width of the floating ground-plane conductor. Applying the method, a 7 dB coupler with the measured isolation better than 27 dB across a wide bandwidth (more than 120%), a 90° Schiffman phase shifter with phase deviation ±2.5° and return loss more than 17.5 dB covering 63.4% bandwidth, and a bandpass filter with completely eliminated second-order spurious band are implemented. The performances of the current designs are superior to those of the previous components configured with the PCMLFGPC.

A Novel Design of Dual-Band Coupler with Stepped-Impedance Open Stubs

This paper presents a novel dual band coupler design that can operate at two frequency bands. It is accomplished by modifying the length and impedance of the branch lines in the conventional structure. Open stubs are used to achieve dual band branch line coupler with compact size and improve the performances. The dimensions of a conventional BLC “Branch Line coupler” occupy large area, according to the length of the transmission line which is always (g/4 of the operating frequency, ( is so long at low frequencies. When we use open ended stubs the dimensions of the new BLC is reduced compared to the conventional design. The proposed model was shown to reduce the size of the dual-band BLC around 61% based on the proposed topology. It was designed and simulated using EM solver tools for both DCS and WIMAX systems. The final optimized microstrip coupler was fabricated and measured. The simulation and measurement results are in good agreements.

Analysis of Proximity Coupled Microstrip Patch Antenna for Wireless Applications

Analysis of Proximity Coupled Microstrip Patch Antenna for Wireless Applications

Compact Multiband Antenna for Handsets With a Conducting Edge

This communication proposes a compact multiband antenna fed by microstrip coupling for handsets with conducting edge applications. The antenna is composed of a U-shaped loop, an inserted open-end T-shaped slot, and a feed line with a compact antenna area. Three types of resonant modes are excited, namely loop mode, slot mode, and monopole mode. Parametric studies have been performed. After the related parameters are controlled, the bandwidth of this antenna has the potential to cover the mobile bands of GSM (824–960 MHz), DCS (1710–1880 MHz), PCS (1850–1990 MHz), UMTS (1920–2170 MHz), LTE bands (FDD–LTE bands 1–10, 15, 16, 18–20, 22, 23, 25–27, and 30 and TDD–LTE bands 33–43). Good radiation characteristics, such as gain and radiation efficiency, are obtained with these operating bands. In addition, the structure of the inserted slot antenna reduced the user’s hand effects on the radiation efficiency.

Lumped-equivalent circuit model for multi-stage cascaded magnetoelectric dual-tunable bandpass filter**Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

A lumped-equivalent circuit model of a novel magnetoelectric tunable bandpass filter, which is realized in the form of multi-stage cascading between a plurality of magnetoelectric laminates, is established in this paper for convenient analysis. The multi-stage cascaded filter is degraded to the coupling microstrip filter with only one magnetoelectric laminate and then compared with the existing experiment results. The comparison reveals that the insertion loss curves predicted by the degraded circuit model are in good agreement with the experiment results and the predicted results of the electromagnetic field simulation, thus the validity of the model is verified. The model is then degraded to the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates. It is revealed that if the applied external bias magnetic or electric fields on the two magnetoelectric laminates are identical, then the passband of the filter will drift under the changed external field; that is to say, the filter has the characteristics of external magnetic field tunability and electric field tunability. If the applied external bias magnetic or electric fields on two magnetoelectric laminates are different, then the passband will disappear so that the switching characteristic is achieved. When the same magnetic fields are applied to the laminates, the passband bandwidth of the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates becomes nearly doubled in comparison with the passband filter which contains only one magnetoelectric laminate. The bandpass effect is also improved obviously. This research will provide a theoretical basis for the design, preparation, and application of a new high performance magnetoelectric tunable microwave device.

Detection of Voids in Fiber Reinforced Plastics Using Magnetoinductive Coupled Microstrip Sensor

This letter proposes a novel method of noninvasive detection of voids in fiber reinforced plastics (FRPs). An ideal nondestructive evaluation method for the detection of subsurface defects that utilizes the capabilities of a magnetoinductive planar microstrip sensor is examined through a finite-integration-based model in this letter. A combination of magneto inductive waveguide as (MIW) and a patch radiator is used as the sensing element. The magnetoinductive waveguide increases the sensitivity of the patch to the presence of voids in the FRP.

Design and realization of high directivity microstrip coupler

ABSTRACTA method to improve the directivity of the microstrip coupler is presented. The structure of the coupler is modified for variable coupling coefficient. Using this structure, the power coupled to the isolated port can be controlled which results in high directivity. Using this procedure, 15‐dB couplers are designed and fabricated at 0.9 GHz. A high directivity of 43 dB is measured. The validity of the design concept is verified by simulations and measurements. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1078–1081, 2015

임피던스 정합기를 이용한 근접 결합 급전 패치 안테나의 대역폭 확장

근접 결합 급전 방식을 이용한 마이크로스트립 패치 안테나의 급전 선로에 임피던스 정합기를 집적하여 대역폭을 확장하는 방법에 대하여 연구하였다. 여러 가지 유전상수와 두께를 가지는 기판을 사용한 근접 결합 급전을 이용한 패치 안테나에 임피던스 정합기를 집적한 경우와 임피던스 정합기를 사용하지 않은 경우의 대역폭과 방사특성을 비교하였다. 임피던스 정합기를 사용한 경우가 사용하지 않은 경우에 비하여 방사특성의 저하 없이 대역폭이 크게 증가함을 볼 수 있었다.

Compact second‐order dual‐ and quad‐band bandpass filters using asymmetrical stub‐loaded resonator and uniform‐impedance resonator

AbstractIn this article, a second‐order dual‐band bandpass filters (BPF) operating at 1.8 GHz GSM and 5.2 GHz WLAN is first proposed by using asymmetrical stub‐loaded resonators (SLRs). Then, a set of half‐wavelength resonators (HWRs) are embedded into asymmetrical SLRs to produce a passband at 3.5 GHz, and the other set of HWRs are coupled with high‐impedance parallel coupling microstrip lines to generate a passband at 6.8 GHz, so that a second quad‐band BPF is successfully designed. The fabricated dual‐band BPF and quad‐band BPF have compact sizes of 0.052λg × 0.17λg and 0.054λg × 0.195λg, respectively. In addition, high band‐to‐band isolation, good in‐band return loss, and wide stopband can be also observed. Good agreement is shown between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:997–1003, 2015