Impedance Matching Network Research Articles

Acoustic-Mechanical-Electrical (AcME) coupling between the linear compressor and the Stirling-type cryocoolers

Benefitting from invention of linear compressors, Stirling-type cryocoolers have been experiencing rapid development due to its’ compact structure and high reliability. However, the efficiency of cryocoolers still needs to be improved to meet the requirements of long-term space exploration. A state point named ‘sweet spot’ is proposed after analyzing the output characters of linear compressors, and the ‘sweet spot’ corresponds to a state when the highest efficiency and the maximum power output are achieved simultaneously. Acoustic-Mechanical-Electrical (AcME) coupling between linear compressors and cryocoolers is established by combining the dynamics of the piston and the displacer with the thermodynamics of regenerative cryocoolers.Two cases are provided to verify that the AcME coupling theory is a useful tool for designing and optimizing cryocoolers. Mismatching between the linear compressor and the cold finger is discussed, and some possible extra impedance matching methods are introduced based on the electrical impedance matching network.

An X-Band 40 W Power Amplifier GaN MMIC Design by Using Equivalent Output Impedance Model

This paper presents an X-band 40 W power amplifier with high efficiency based on 0.25 μm GaN HEMT (High Electron Mobility Transistor) on SiC process. An equivalent RC (Resistance Capacitance) model is presented to provide accurate large-signal output impedances of GaN HEMTs with arbitrary dimensions. By introducing the band-pass filter topology, broadband impedance matching networks are achieved based on the RC model, and the power amplifier MMIC (Monolithic Microwave Integrated Circuit) with enhanced bandwidth is realized. The measurement results show that this power amplifier at 28 V operation voltage achieved over 40 W output power, 44.7% power-added efficiency and 22 dB power gain from 8 GHz to 12 GHz. The total chip size is 3.20 mm × 3.45 mm.

Optimal Design of Broadband Matching Networks using Cuckoo Search Optimization Algorithm

In this work, a novel evolutionary optimisation algorithm is introduced for the design of broadband matching networks connecting a resistive source generator and a complex inductive load. Impedance matching networks are the key for full transfer of power to the load. They should offer matching over the entire frequency concerned band. A low noise amplifier (LNA) is also optimised to attain the target gain and noise figure specifications over a definite bandwidth, throughout lumped LC elements. Cuckoo search optimisation algorithm (CSOA) is inspired by the life of a bird family, called cuckoo, offers excellent results with simple tuning parameters compared to previous conventional and meta-heuristic optimisation algorithms. It is extremely powerful in solving engineering optimisation problems. Simulation results for broadband impedance matching networks are presented and analysed and the optimised matching network improves well the performances of the circuit.

Performance analysis of spinning magnet as mechanical antenna

Long wavelength results in the low radiation efficiency of a portable conventional antenna operating at very low frequency (VLF) and below. This has motivated one to develop an innovative approach to design an electrically small antenna in a frequency band lower than VLF. The time-varying electromagnetic fields can be generated by spinning a permanent magnet. In this way, the mechanical energy is converted to the electromagnetic energy, and the impedance matching networks with nonnegligible insertion loss are not required. Therefore, this mechanical antenna with spinning magnet can improve radiation efficiency in a low frequency band. In this paper, we give the detailed analysis procedure for the spinning magnet, which is seldom discussed in other published reports. In order to analyze the electromagnetic characteristics of the spinning magnet, in this paper we use the ampere return circuit theorem to investigate the equivalent relation between a spinning magnet and the orthogonal magnetic dipole. We introduce an initial spinning angle of the magnet into the dyadic green’s function. With this modification, we provide the rigorous analytic formula for field computation of the orthogonal magnetic dipole. Thus the electromagnetic characteristics of the spinning magnet and spinning magnet array can also be analyzed. For a spinning NdFeB magnet with a magnetization of <i>B</i><sub>r</sub> = 0.8 T and a volume of <i>V</i><sub>r</sub> = 270 cm<sup>3</sup> as well as 9600 revolutions per minute, the simulation results reveal that the magnetic field of 15 fT at 1 km in air space can be obtained. But the magnetic field of the spinning magnet decreases quickly to 1 fT at 250 m in sea water. Considering the potential demand for increasing the field strength in the near field region, we recommend to use a magnet array with small-sized elements. The magnet array can be used to control the near field pattern. We take two magnets as an example for studying the performance. It can be found from the simulation results that the magnetic near field is increased by 3 dB with the linear magnet array consisting of two elements. With the initial spinning angle of the magnet element adjusted, the near field pattern of the magnet array can be controlled. This is analogous to beam steering of traditional phased array for high band operation. It can be concluded from our study that the spinning magnet is a possible alternative solution for low frequency small transmitter antenna.

On the Design of Broadband Hybrid Amplifiers Using Non-Uniform Transmission Lines as Impedance Matching Networks

In this paper, an approach for the practical design of broadband amplifiers in hybrid technology is presented. It is based on the use of non-uniform transmission lines to implement impedance matching networks, which are synthesized exploiting the powerful optimization tools available in the most common computer-aided design software packages. The versatility of the proposed technique makes it suitable for the design of a wide variety of broadband amplifiers. Furthermore, it is easily implementable in most microwave simulators and allows a considerable design time reduction, since it can be applied in a systematic way and avoids the use of external tools. To validate the technique, it is applied to the design of a low noise amplifier using a single encapsulated transistor. A prototype was implemented, providing 10-dB flat gain from 1 to 12 GHz, noise figure under 2.5 dB, and acceptable input and output matching, which agrees with the simulation data.

Theory and Design of Impedance Matching Network Utilizing a Lossy On-Chip Transformer

In this paper, we present a study on a transformer-based impedance matching network. We use a simplified transformer model comprising two magnetically coupled coils, which are driven by a source and terminated by a load. The formulae of the load and the source impedance for conjugate matching of both sides of the transformer are presented, and a figure of merit is proposed for the evaluation of the power transfer efficiency of the transformer under conjugate matching conditions. Analytical expressions are provided for constructing the widely used transformer network consisting of a resistive load and a parallel tuning capacitor. To verify the proposed work, we examined various on-chip transformers implemented in 0.18 μm CMOS technology. Simulation and measurement results for a matching network synthesized using the aforementioned analytical expressions corresponded well with the result of analysis for operating frequencies up to 72% of the self-resonant frequency of the transformer. The presented results confirm that the proposed analytical formulae based on the simplified transformer model are useful for the design and optimization of transformer-based impedance matching networks in the microwave and millimeter-wave regimes.

Slotted Folded Patch Antenna With Double-T-slots for Platform-Insensitive UHF Tag Design

A compact folded patch antenna, which has a dimension of 42 mm $\times50$ mm $\times1.6$ mm ( $0.128\lambda \times 0.152\lambda \times 0.0049\lambda $ ) is proposed. Multiple C-shaped slotlines are incorporated for tuning down the resonant frequency of the folded patch. A pair of double-T-slots, which acts as the impedance matching network, is etched at the center of the patch for achieving conjugate match between the antenna and the chip. By combining the analytical method and the particle swarm optimization algorithm, an equivalent circuit model is constructed for analyzing the impedance characteristics of the proposed tag antenna. With the use of 4 W EIRP, a maximum read distance of 11.5 m is achievable by placing the proposed tag antenna on a dielectric object. Also, the tag antenna is found to be able to reach ~5.2 m on metal. The operating frequency of the proposed tag antenna is very stable for both the dielectric and metallic objects, which is very desirable for practical applications.

Low-Profile Independently- and Concurrently-Tunable Quad-Band Antenna for Single Chain Sub-6GHz 5G New Radio Applications

This paper presents a quad-band frequency agile antenna, with independent and concurrent frequency tunability in each band, for a tunable, concurrent, quad-band single chain radio receiver for 5G New Radio (NR). More specifically, the antenna comprises of four planar slots etched in a ground plane and fed through a single microstrip feedline, without any impedance matching network. The structure is optimized to maximize isolation between the individual slots and their respective resonant frequencies. Furthermore, a novel high order harmonic suppression method is demonstrated, which controls the current distribution via creating a fictitious short circuit in the slot antenna–enabling the antenna to achieve a much wider tuning range. Numerical simulations are verified using experimental implementation and measurements, with good agreement observed. The four slots resonate around the 830 MHz, 1.8 GHz, 2.4 GHz and 3.4 GHz frequency bands, which are independently tuned (using a varactor diode in each slot) to achieve tuning ranges of approximately 64%, 66%, 27% and 33%, respectively. More importantly, the contiguous four bands covers a total frequency tuning from 0.6 to 3.6 GHz i.e. a tuning range of approximately 143%. Finally, far-field measurements are performed and the antenna is evaluated in over-the-air testbed (quad-band radio receiver), which measures the Error Vector Magnitude performance for the individual channels. Good performance is observed, confirming acceptable isolation performance between the four bands. The data reported in this paper is available, from ORDA-The University of Sheffield Research Data Catalogue and Repository, at https://doi.org/10.15131/shef.data.11219000.v1 .

Optimal design of broadband matching networks using cuckoo search optimisation algorithm

In this work, a novel evolutionary optimisation algorithm is introduced for the design of broadband matching networks connecting a resistive source generator and a complex inductive load. Impedance matching networks are the key for full transfer of power to the load. They should offer matching over the entire frequency concerned band. A low noise amplifier (LNA) is also optimised to attain the target gain and noise figure specifications over a definite bandwidth, throughout lumped LC elements. Cuckoo search optimisation algorithm (CSOA) is inspired by the life of a bird family, called cuckoo, offers excellent results with simple tuning parameters compared to previous conventional and meta-heuristic optimisation algorithms. It is extremely powerful in solving engineering optimisation problems. Simulation results for broadband impedance matching networks are presented and analysed and the optimised matching network improves well the performances of the circuit.

Design and realization of an ultra-low power sensing RF energy harvesting module with its RF and DC sub-components

Herein, design, development, and analysis of ultra-low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero-bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super-capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low-power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super-capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra-low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as −50 dBm. The system can be used for battery free applications or expanding battery life for ultra-low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems.

Implementation of Flat Gain Broadband Power Amplifier With Impedance Rotation Compensation

The conventional broadband impedance matching network in low-pass structure cannot present adequate broadband impedance rotation for the optimum broadband operation of the power amplifier (PA), resulting in performance variations and degradations. The underlying constraint is the phenomenon of opposite impedance rotation. Against such a backdrop, this paper presents a methodology using the band-pass topology to compensate the frequency-variable response of the PA. The CGH40010F from Cree is used to verify the effectiveness of this compensation method. The experimental results are in good agreement with the simulation. The proposed PA yields good gain flatness (±0.5 dB), input/output return loss (>13 dB), and high power added efficiency (>60 %) over the band from 1.7 to 2.7 GHz. After digital predistortion, the measured adjacent channel power ratio is about −55 and −50 dBc at ±5 and ±10 MHz offset when the PA is driven by 5- and 10-MHz WCDMA signals at 6.5 ~ 7 dB power back-off.

Influence of wire-based impedance-matching on Helical antenna radiation and limitations of equivalent model

We investigate the influence of a wire-based impedance-matching network for an axial-mode helical antenna on the radiation pattern. This network, proposed in our previous work, comprises a single wire attached to the helix. We show that the matching wire, mounted on a tubular dielectric support and attached to the helix close to the reflector, does not degrade the antenna radiation pattern. We also investigate limitations of the equivalent thin-wire model proposed in our previous work.

A passive isolator realized by magnetoelectric laminate composites

This work demonstrates a passive isolator realized by magnetoelectric laminate composites. The proposed isolator consists of a magnetoelectric gyrator, two impedance matching networks, and a load impedance. The equivalent circuit model of the isolator is developed. Good agreement has been obtained between the measured and computed results based on the proposed equivalent circuit model. The measured forward insertion loss and reverse isolation of the proposed isolator are 4.7 dB and 19 dB, respectively. A figure-of-merit which determines the performance of the isolator is proposed, which can be used to guide the design of such isolators.

An Online Impedance Analysis and Matching System for Ultrasonic Transducers.

Electrical impedance matching of ultrasonic transducers is important in optimizing the energy consumption as well as guaranteeing equipment safety for ultrasonic systems in both laboratories and industries. The existing solutions usually rely on expensive instruments to conduct off-line impedance measurements and deploying static impedance matching networks for each specific transducer across a target frequency band. Here, we present an initial prototype of an online impedance analysis and matching system (OIAMS). In this system, an improved voltage-current method and a phase-difference method were integrated for online impedance measurement in real time, and an L-type matching circuit with variable components helped to achieve dynamic impedance matching. A feedback protocol was embedded in a microcontroller to adjust the matching strategies based on dynamic measurements, while the whole system was controlled through a software interface developed on a LabVIEW platform. Online measurement results showed that OIAMS conducted accurate impedance measurements with a relative error within 3.90% for amplitude and 13.11% for phase across the 100% bandwidth of the tested transducers. After matching, the reflected acoustic power of a 1.00-MHz transducer was reduced by over 50%, increasing the generated sound pressure level by over 2.8 dB across its 70% bandwidth.

Comments on Dual-Band Design Theory for Dual Transmission-Line Transformer

In the above paper [1] , Wang et al. proposed a dual-band parallel transmission line (TL), real-to-real impedance matching network (RRIMN). However, the possible solutions discussed in [1, eqs. (11)–(18)] are incomplete. The incompleteness is due to the selection of the positive-definite region of impedances $Z_{1}$ and $Z_{2}$ . The positive-definite region of impedances $Z_{1}$ and $Z_{2}$ in [1] are chosen as $\theta _{1}$ in the first coordinate and $\theta _{2}$ in the second coordinate. However, there exist several positive-definite regions of $Z_{1}$ and $Z_{2}$ . Hence, selecting one positive-definite region will lead to a limited solution. Here, we will provide two different possible solutions and their physical significance in terms of transmission phase shift [2] .

A Reader Antenna for UHF Near-Field RFID Applications Based on the Segment-Line Oppositely Directed Currents

A reader antenna based on the segment-line oppositely directed currents is proposed in this letter for the ultrahigh frequency near-field (NF) radio frequency identification applications. The proposed antenna consists of two identical electrically large dipole elements without additional impedance matching network. To keep the surface currents along the dipole elements in-phase, the segmental and loaded method is adopted. Through the dispersion analysis, the maximum length of the dipole elements is one and a half guide wavelength with 12 segments and 0.7 pF lumped capacitors at 920 MHz. Subsequently, adjusting an appropriate distance between the dipole elements can form the oppositely directed currents, resulting in a strong, uniform, and large NF magnetic field distribution. The measured results show that the bandwidth is 53 MHz from 884.5 to 937.5 MHz covering the FCC standards. The interrogation zone is approximately equal to 480 mm × 250 mm under the observing height of 50 mm above the antenna surface. Thus, the proposed antenna is suitable to be used for the smart showcases and shelves.

Design and Performance Evaluation of 13.56-MHz Passive RFID for E-Skin Sensor Application

In this letter, a 13.56-MHz passive RFID is proposed as a wireless communication method for an e-skin sensor. Planar coils for RFID antenna were designed on a flexible printed circuit board. An impedance matching network for the coil antenna was optimized to minimize signal loss between coil antennas. Signal loss was measured after attaching the designed antennas to the arm of a human subject. The performance of the proposed method was then evaluated by measuring a read range. The results showed that the proposed method has sufficient read range to wirelessly receive data from an e-skin sensor located on an arm. The proposed method can be effectively used to realize wireless data communication for an e-skin sensor.

A coupled‐fed dual‐band impedance matching network for small long‐term evolution smartphone antennas

AbstractA coupled‐fed dual‐band impedance matching network is presented for the small antennas in long‐term evolution (LTE) smartphones. The impedance matching network consists of two distributed capacitors and two distributed inductors, also functioning as a coupled‐fed structure to feed the planar inverted‐F antenna (PIFA). An equivalent circuit of the impedance matching network is presented to reveal the mechanism of the impedance matching enhancement of the PIFA and the generation of an additional resonant mode operating at the lower band around 720 MHz. Both simulated and measured results show that the printed PIFA with the volume of 50 × 13.5 × 1.6 mm3 achieves the total antenna efficiency larger than 70% over the two operating bands of 690‐1088 MHz and 1690‐2500 MHz for |S11| ≤ ‐10 dB.

A tunable reflective analog predistorter based on variable impedance matching network

This paper presents a modified reflective analog predistortion circuit to enable the tuning capability of gain and phase conversions. A variable impedance matching network based on varactor diode is introduced in the circuit to achieve the tuning function by changing its bias voltage. Based on this modified circuit, a tunable predistorter for traveling wave tube amplifier (TWTA) is designed and fabricated. The fabricated predistorter shows more than 5.5 dB tuning range of gain conversion and 49.0° tuning range of phase conversion in 29–31 GHz with the bias voltage varies from 0 V to 20 V. Good linearity enhancement has been obtained for a Ka-band TWTA with this predistorter.

Reconfigurable Impedance Matching Networks With Controllable Phase Shift

Two kinds of reconfigurable impedance matching networks with controllable phase shift are proposed. The reconfigurable networks can match different loads with desired phase shift at center frequency and no extra phase shifter is needed. The two networks are realized by using varactor diodes and switches, respectively. The design equations and achievable phase shift range of the two networks are derived. Two prototypes working at 1 GHz were fabricated for verification. The measured results show good return loss response and precise phase shift value.