RF Impedance Matching Research Articles

Improved impedance matching speed with gradient descent for advanced RF plasma system

Plasma processes are widely used in the fabrication of integrated circuits for the smaller, faster, more powerful circuits demanded by new technology. High-performance semiconductor equipment is required for dynamic random-access memory and three-dimensional NAND flash memory in semiconductor manufacturing. To enhance the speed of RF impedance matching, this paper proposes a method for calculating the load impedance of the plasma chamber. To calculate the target value of the variable components, we employ the input impedance of the impedance-matching unit and the complex impedances of the variable components. In addition, the internal parameters are automatically tuned through the gradient-descent method of machine learning, which improves the accuracy of impedance matching. The new matching method achieved a fast matching time and high efficiency of the matching trajectories. Moreover, it avoids the increase of the reflected power during the matching process, which causes plasma instability, and prohibits significant matching delay in a specific area, which disadvantages the conventional matching algorithm. These advantages are expected to significantly expand the development of new plasma processes from that of conventional impedance matching.

A Comprehensive Review on High-efficiency RF-DC Converter for Energy Harvesting Applications

The design of radiofrequency energy harvesting (RFRH) circuit for wearable devices, wireless sensor networks, and IoT applications can be classified mainly into radio frequency to direct current (RF-DC) converter, a transmitter and receiver antenna, an impedance matching network, and a storage device or a load. By scavenging RF energy from the ambient environment, this developing technology allows low-power wireless devices to be self-sustaining and environment friendly. To eliminate the need for batteries, RFEH technology has become a dependable and promising alternative for extending the lifetime of power-constrained wireless networks. This paper mainly focused on the input and output power, Power conversion efficiency (PCE), and sensitivity. Due to the weak and limited signal strength of received RF power, high-efficiency state-of-the-art RF energy harvesters must be designed to provide sufficient DC supply voltage to wireless networks. We provide in-depth information on the system’s parameters. Optimum efficiency and maximum output power are the main concerns of an RFEH system. Therefore, RF Energy harvesting system review, antenna design, impedance matching, and RF-DC converter are presented in this paper to provide a deep insight into the design of the RFEH system. This article may help in identifying new research in the field of RF Energy Harvesting.

A 2.4-GHz 10-W Class Bridge Rectifier and Its Efficiency Analysis With the Behavioral Model

This article presents a 2.4-GHz band 10-W class bridge rectifier that achieves a high-measured efficiency of 90.2%. To clarify the mechanism for obtaining high efficiency, a theoretical analysis with the novel behavioral model of bridge rectifiers is demonstrated. The behavior model includes three functional blocks, namely; 1) impedance transform, which defines the RF impedance for the bridge diode; 2) RF impedance matching; and 3) rectification with the ideal current waveform of the bridge diode. Closed-form formulas for the rectification efficiency and the maximum input power are derived using the behavioral model. The RF impedance can be optimized to obtain high efficiency with the derived formulas, similar to source-pull operations in harmonic balance simulations or experiments. The fundamental limitation on the rectification efficiency is obtained for a bridge rectifier with the optimum RF impedance. In the experimental investigation of the 2.4-GHz 10-W class bridge rectifier, the measured efficiency of 90.2% agreed well with the theoretical value of 91.2% with represented formulas. Furthermore, the derived formulas are applied to the 5.8-GHz 1-W rectifier, and its effectiveness can be confirmed. It is evident that the analyzed efficiencies are close to the fundamental limitations.

Testing and Validation of Adaptive Impedance Matching System for Broadband Antenna

Broad RF impedance matching is challenging; however, the need for broadband matching is found frequently in modern RF and wireless systems with multiple wireless standards. Moreover, in 5G technology, multiple frequency bands are used, and these systems typically employ a broadband antenna or multiple antennas. Antenna impedances vary from design targets for many reasons including manufacturing process variations or antenna environment changes. An adaptive impedance matching system (AIMS) for testing and validation is introduced, and its implementation is shown in this paper. The AIMS can control impedance matching tuner settings to provide an arbitrary impedance frequency-varying load that meets user-defined conditions. This AIMS provides a testing and validation system for broadband antennas that can be characterized by various settings of the impedance matching tuner. As a device under test (DUT), a three-stub reconfigurable filter was used as the impedance matching tuner on a RT/Duroid 6010 RF board. It was integrated with a control circuit board. This AIMS implementation also included an antenna impedance tuner that can vary the distance between the antenna and the ground plane. This model represents practical antenna impedance variations. The AIMS controls a network analyzer and the impendence matching tuner. The adaptive control program on a PC was developed to perform an effective two-pass tuning strategy. This article presents the successful automated tuned results and their numerical evaluations of three cases that were generated by the antenna impedance tuner.

A Chopping Switched-Capacitor RF Receiver With Integrated Blocker Detection

A 0.1–0.6 GHz chopping switched-capacitor (SC) RF receiver (RX) with an integrated blocker detector features a tunable center frequency, a programmable filter order, and a high out-of-band (OB) linearity. RF impedance matching, high-order OB interferer filtering, and flicker-noise chopping are achieved with passive SC circuits only. The 34–80 mW 65-nm RX achieves 35-dB gain, +31 dBm OB-third-order input intercept point, +15 dBm B1dB, and 4.6–9 dB NF. The 0.2-mW integrated blocker detector detects large OB blockers with only 1- $\mu \text{s}$ response time. The filter order can be adapted to blocker power with the blocker detector.

Novel Planar and Waveguide Implementations of Impedance Matching Networks Based on Tapered Lines Using Generalized Superellipses

For the practical implementation of RF and microwave impedance matching networks, a widely employed solution—alternative to the use of classical impedance transformers—is based on tapered lines. This paper shows a simple method to design smooth tapers that take into account the dispersion of the line and the required design bandwidth simultaneously. A planar taper has been designed in microstrip technology with the same length of classical ones but improving their performances. A waveguide prototype has also been designed with similar performance to a commercial one but with one third of its length. Both tapered structures have been obtained through the optimization of very few parameters using the same design strategy. As a result, the reflection coefficient of the tapers can be optimally adapted to a given specific mask using the prescribed value of physical length. Experimental results for both tapers are included for the validation of the proposed topologies and the related design method.

Design and Simulation of Testing Circuit for Radio Frequency Chip

RF technology is widely used in wireless communication. Due to the small size, high density and high frequency, RF IC testing based on ATE faces many challenges. This paper took a LNA chip fabricated by a GaAs process as an example, simulated the test circuit and studied two methods of RF impedance matching by using the software of Agilent ADS. The results show that it solves the impedance mismatch of the input and output ports in RF test, providing the theoretical support to the design and production of RF test board.

0.18-μm CMOS wideband passive mixer

A 0.18-μm CMOS wideband passive mixer fully integrated with baluns in IBM7HP process is reported. The mixer exhibits wideband operation, despite the intrinsic narrow-band magnitude balance of passive baluns. Very low DC offset, of less than 3 mV, is achieved without any DC cancellation circuits, due to high LO–RF isolation. At the RF frequency of 2.4 GHz, the combined IF differential outputs provide conversion loss (CL) of 7.5 dB, input 1 dB compression point (IP1dB) of 6.2 dBm, and input third-order intercept point (IIP3) of 15.5 dBm. This mixer exhibits broad-band RF impedance matching with reflection coefficient magnitude better than −9.6 dB through the RF frequency range from 1 to 12 GHz. The CL of 10.1–12.9 dB, IP1dB of 8.6–14.4 dBm, and IIP3 of 16–22.2 dBm are achieved at this frequency range for broad-band applications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:23–27, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27226

A comparative study of c‐shaped, e‐shaped, and u‐slotted patch antennas

AbstractA class of popular linearly polarized slotted antennas are compared with respect to their RF mechanism, radiation mechanism, impedance matching, and cross polarization characteristics for wireless communication frequency band 1.9–2.4 GHz.It is found that C‐shaped and double C‐shaped patch antennas, even though miniaturized, suffer from narrow bandwidth and high cross polarization level, due to its orientation of slot. U‐slotted and E‐shaped patch antennas show high bandwidth with minor penalty in size and cross polarization level. In order to understand the effect of slot on the radiation in these antennas, a novel strategy of looking at the near‐field of these antennas has been presented. These near‐field plots are analyzed to explain certain far‐field radiation characteristics in these antennas such as‐ cross‐pol level. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1746–1757, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26894

Characteristics of 60 GHz Analog RF-Optic Transceiver Module

Using an electro-absorption duplexer (EAD) we presented a transceiver (TRx) module for dual function of both electrical-to-optical (E/O) and optical-to-electrical (E/O) conversion at 60 GHz band. The EAD chip was fabricated by monolithically integrating both a waveguide photodiode (PD) and an electro-absorption modulator (EAM) in association with traveling wave electrodes. We also investigated the issues of RF packaging in which the optoelectronic and electronic amplifier devices were co-packaged in a single housing. The RF impedance matching was accomplished in assistance with a microstrip bandpass filter.

Suppression of insertion loss by slit patterning of a magnetic film in a CoFeB/polyimide hybrid thin-film coplanar line for a rf impedance matching device

A hybrid thin-film coplanar line with a slit-patterned CoFeB magnetic film for a rf impedance matching was fabricated, and an effect of the loss reduction by introducing a slit-patterned magnetic film was investigated. The fabricated hybrid thin-film coplanar-line device consisted of the top and bottom 5μm thick copper conductors and an inner (0.5μm thick polyimide)/(0.15μm thick CoFeB)/(0.5μm thick polyimide) trilayer. A signal linewidth was 6μm. The total width of the slit-patterned magnetic film was about 200μm. The devices with some kinds of the width of the magnetic film stripe were fabricated. As a result, insertion loss per unit line length decreased greatly above 1.5GHz with decreasing width of the magnetic film. The loss suppression was due to an effect of reducing the in-plane eddy current of the magnetic film. On the other hand, the propagation signal wavelength of the device increased with decreasing width of the magnetic film, which was due to a decrease of distributed inductance. When applying the device to a quarter-wavelength impedance matching device, the slit-patterned magnetic film was effective for decreasing the insertion loss at high frequencies beyond 1.8GHz.

XPS Evaluation of Samples Surface Cleaned by the XEI Evactron®

Abstract With the advent of field emission gun equipped SEMs and TEMs with clean vacuum systems, it has been shown repeatedly that the surface cleanliness of samples exposed to the small, high current density electron beam available in these instruments is critical with respect to controlling hydrocarbon contamination under the electron beam. in previous studies of dedicated plasma cleaners for TEM samples by one of the authors (SDW), it was shown that surface analytical techniques are the best methods for determining the effectiveness of such cleaners in removing hydrocarbons from the samples’ surfaces. in the current study, some of the experiments that were used in these previous studies were repeated using the XEI Evactron® system in order to compare the relative effectiveness of this system for surface cleaning of EM samples. Figure 1 shows a picture of the sample introduction chamber of a VG Scientific ESCALAB Mkll system (XPS) with the Evactron® in place. The Evactron® system consists of an RF head unit that attaches to the vacuum chamber with an adaptable flange, an RF impedance matching unit, and an RF generator/vacuum controller. Although a 100% O2 system can be used and is recommended, for safety reasons, a 20%O2/80%Ar by volume gas mixture was selected because of the hydrocarbon oil used in the mechanical pump. Cleaning was also performed using laboratory air. The major difference between the dedicated plasma cleaners and the Evactron® configuration is that the sample is not immersed in the plasma but is exposed to the activated oxygen species in the downstream flow.

High performance modules of 2.5 Gbps modulator integrated DFB lasers using new RF impedance matching technique

We report the improvement of frequency response characteristics of 2.5 Gbps modulator integrated distributed feedback (MI-DFB) laser modules using new impedance matching technique. Frequency responses for the fabricated module using the '+' shaped microstrip line for impedance matching have been significantly improved such as the RF return loss of 11 dB and the 3 dB frequency bandwidth of 4.1 GHz, compared to 6 dB return loss and 1.5 GHz bandwidth for the conventional module. These results can also be predicted by the simulation of frequency responses for the modules, From the fabricated MI-DFB laser modules, good transmission performance has been obtained up to 640 km.

Resonant cavity excitation system for radial array slab CO2 lasers

A rf excitation system that can drive a gas laser constructed of multiple wide, but narrow-gap (slab), discharge volumes is presented. Resonant cavity techniques adopted from microwave applications are employed to provide uniform rf power division and impedance matching into each electrode channel. This approach when applied to a large radial array of gain channels can be used to create a very high-power laser system in an unusually compact package.

140 GHz GaAs double-Read IMPATT diodes

CW GaAs double-Read IMPATT diodes for D-band frequencies are designed and tested. For reproducible RF impedance matching, the module encapsulation technique is applied. Ohmic losses of the active device are reduced by a titanium-Schottky contact instead of an alloyed ohmic n/sup +/-contact. At 144 GHz 100 mW RF power with a conversion efficiency of 5% is realised.

4897604 Method and apparatus for selective adjustment of RF coil size for magnetic resonance imaging

A bridge conductor (104) for the turns of an MRI RF coil may be connected serially within a connector joint area of an inductive coil (100) so as to selectively increase its physical size (e.g., so as to accommodate larger patient volumes to imaged therewithin). Serial capacitance may be included in at least one of the bridging conductors so as to substantially reduce the net inductive impedance of the added bridge conductors such that the standard coil RF tuning and impedance matching circuits may still operate within their normal predetermined adjustable ranges.

Reduced insertion loss of X-band RF fiber-optic links

The insertion loss of an experimental high-frequency fiberoptic link is reduced to 7 dB with an 800-MHz (9%) 3-dB bandwidth at 9 GHz by improving the link optical performance and by using reactive passive RF impedance matching. The link signal-to-noise ratio is measured and found to be about 125 dBc/Hz over the 800-MHz bandwidth. This is a significant improvement from the typical X-band RF link insertion loss of 40 dB and could help to open the way to many microwave applications of fiberoptic links in radar and avionics systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>