Tunable Matching Network Research Articles

Resonant Measurement of Coaxial Probe Based on Tunable Impedance Matching Network

In this work, we first present a tunable impedance matching network (IMN) to produce an outstanding resonance for improving the sensitivity of coaxial probes. A two-port network based on a three-line coupled (TLC) structure along with a tunable phase shifter is designed to realize conjugate matching. The calculated shape factor for characterizing the sharpness of resonance can be up to 1.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{5}$</tex-math> </inline-formula> when deionized (DI) water is loaded. The minimum measurable concentration level of ethanol is 0.005 mole fraction. The conventional probe’s sensitivity is enhanced to be comparable with those achieved by other resonance-based sensing methods. Using calibration liquids, the complex permittivity of a liquid can be extracted.

Arbitrary Termination Complex Impedances Tunable Bandpass Filter Using Single and Dual-Mode Resonators

This paper presents a design of microstrip line tunable bandpass filter (BPF) with a transmission zero (TZ) that can accommodate arbitrarily terminated input and output port impedances ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z_s</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z_L</i> ≠ 50 Ω). We extracted a new coupling matrix to design the proposed tunable BPF and presented intuitive circuit-level implementation using a single dc-bias controlled single and dual-mode resonators. The proposed tunable BPF integrates the function of tunable filter and matching network into a single circuit. To validate the design, three filter prototypes with different input and output port termination impedances (filter A: 50-to-50 Ω, filter B: 20-to-50 Ω, and filter C: (25+j10)-to-50 Ω) are manufactured and their performances were measured. The experimental results are consistent with the simulation showing that the passband frequency of the BPF can be tuned from 1.65 GHz to 2.08 GHz (23.06%) with the insertion loss variation from 3.40 dB to 4.69 dB. The proposed tunable BPFs achieved frequency selectivity characteristics by locating the TZ at a lower stopband. The proposed arbitrary terminated tunable BPF can allow direct connection between power amplifier (PA)/low noise amplifier (LNA) and antenna without extra matching networks, resulting in smaller circuit size and can enhance overall performance of RF front-end.

Impedance Compressing Matching Network Based on Two-Port Network Analysis for Wireless Power Transfer System

This article proposes a new design method of impedance matching networks for wireless power transfer (WPT) systems. In WPT systems, the input impedance of resonator varies over a wide range rather than having a fixed value due to coupling variation. In conventional systems, tunable matching networks have been commonly used to match the variable impedance to a fixed impedance. Three-port impedance compression networks have also been proposed to eliminate the mechanical tuning processes. In this article, a two-port impedance compressing matching network (ICMN) is proposed that addresses the load variations without the need for any mechanical tuning. In impedance matching, a two-port network can have a low design degree-of-freedom for load variation. In order to overcome this limitation, this article analyzes the general model of a two-port network and proposes a systematic design procedure. The effectiveness of the proposed method is verified with a design example that constructs an ICMN <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> .

Closed-Loop Antenna Impedance Tuning via Transfer Function Learning for 5G Sub-6 GHz User Equipment

Closed-Loop Antenna Impedance Tuning (CL-AIT) is a technique to adaptively reduce the antenna impedance mismatch by monitoring changes in the antenna impedance and adjusting a tunable matching network (or tuner). This work presents a data-driven CL-AIT solution to find the optimal code for configuring the tuner in order to maximize the power transferred to the antenna; it also minimizes the need for extensive antenna characterization required normally for tuners. A key idea is to learn a transfer function representing the reflection coefficient from data by utilizing the tuner topology. Once the data-driven cost function becomes available, the optimal tuner code is efficiently found with the help of hill-climbing (HC) search. Experimental results demonstrate that the proposed solution sufficiently reduces the impedance mismatch under various antenna conditions and maximum power is delivered to antenna.

A novel dual mode configurable and tunable high-gain, high-efficient CMOS power amplifier for 5G applications

This paper presents a novel dual mode configurable and tunable power amplifier (PA) that achieves a wide-bandwidth and high gain across a operational frequency spectrum of 20 to 30 GHz. The proposed PA used two-stage tunable PA which can be configured as a tunable synchronous mode or tunable stagger-tuned mode PA. PA is implemented by using a distortion-free varactor at the input and output tank of PA. The designed PA includes a high-Q CMOS active inductor (CAI) which provides a widely tunable output matching network. The resistive feedback is used for self-biasing in the designed PA which helps to enhance the linearity, stability of common source (CS) amplifier. The inter-stage impedance matching network consists of shunt and series resonance circuits are employed for maximum power added efficiency (PAE). Furthermore, the capacitive coupled reuse technique is implemented in each stage between the cascaded transistor to reduce the power consumption. A proposed PA is designed using a 65 nm CMOS technology. A measured power gain at the synchronous operation of PA is 28.4 ±0.5 dB with 1.31 GHz bandwidth while power gain at staggered operation is 22.1 ±0.5 dB with 3.71 GHz bandwidth. The measured saturated power (Psat) is 14.21 dBm and the noise figure (NF) is 5.2 dB. The group delay (GD) variation for staggered operation is 57 ±10 ps from 20-30 GHz. A proposed PA exhibits good linearity (IIP3) of 14.5 dBm and PAE is 47.5 % at 24 GHz. The power consumption of a designed PA is 48.56 mW with a supply voltage of 1.2 V.

A Low-Loss Load Correction Technique for Self-Healing Power Amplifiers Using a Modified Two-Tap Six-Port Network

This article presents a low-loss correction technique for a self-healing load-insensitive power amplifier (PA) using a modified two-tap six-port network, wherein the varying (complex) load is first compensated for its unwanted susceptance part, followed by adjustment of the transistor output stage to the ohmic load variation, by modifying its supply voltage and drive level. This two-step approach avoids the high-Q conditions that occur in tunable matching network solutions, which aims to correct for both the real and imaginary load deviations, such as providing lower insertion loss and voltage stress. Next, to facilitate a fully automated load mismatch correction without the need for calibration, a modified two-tap six-port network for impedance detection and control loop approach is proposed. As proof of principle, a prototype 900-MHz class-AB PA featuring the proposed correction technique, as well as, the six-port reflectometer and the control loop, has been implemented as a PCB demonstrator. Measurement results show that the self-healing load-insensitive PA in the events of load mismatch significantly improves the performance and approaches the 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> performance. On a 2:1 VSWR 360° mismatch trajectory and driven by a 64-QAM 3.86-MHz signal, the PA achieves a linear output power of 22 dBm with only ±0.1-dB variation and better than −45-dBc adjacent channel power ratio (ACPR).

Tunable Impedance-Matching Filters

In this letter, we present a general design method for tunable matching networks that have a prescribed filter characteristic over a range of complex port impedances. The approach enables prediction of the achievable tunable impedance range, given a filter topology and tuning element values. As experimental validation, a 2.5-GHz second-order Chebyshev filter is designed using Skyworks SMV2205-040LF varactor diodes to tune the filter resonator and inverter. It is shown that the filter can match port impedances in a region that spans a range of real and imaginary parts of the impedance between 10 and 150 Ω with an insertion loss of 1.5 dB.

A Wideband 62-mW 60-GHz FMCW Radar in 28-nm CMOS

This article presents an ultralow-power 60-GHz indoor frequency-modulated continuous-wave (FMCW) radar in 28-nm CMOS. The radar front end employs a tunable matching network (TMN), which tracks the chirp frequency and supports a 17% fractional bandwidth, covering unlicensed 60-GHz bands (57-66 GHz). A frequency sixtupler chain (x6) in the transmitter (TX) provides an output power of 8.1 dBm while achieving >20% dc-to-RF efficiency. A mixer-first receiver (RX) front end followed by a source degenerated high-pass (HP) filter suppresses TX-to-RX leakage (spillover) and induces minimal spillover-to-target intermodulation. The RX exhibits a 10.5-dB noise figure (NF) at 60 GHz with only 5.6-mW power consumption, making it suitable for an MIMO array. The radar IC with its DSP platform fully demonstrates its capability in indoor sensing scenarios. The duty-cycling compatible design enabled by the 1- μs radar startup time consumes 62 mW/18 mW in continuous mode/6.25% duty-cycled mode, a record low dc power compared to the state-of-the-art radars in this frequency range.

A Simple and Adjustable Technique for Effective Linearization of Power Amplifiers Using Harmonic Injection

A simple and effective method for linearization of power amplifiers (PAs) is proposed. The method is based on the second harmonic injection into the input of the PA. The second harmonic is generated in a feedback path by taking the low-power transistors of a pseudo-differential pair amplifier to their nonlinear regime. The amplitude and phase of the second harmonics are controlled by tunable matching networks of the pseudo-differential pair which include trimmer capacitors. Using a theoretical analysis, we show that the proposed method is capable of canceling the third-order intermodulation signal at the PA output. As a proof of concept, a 10-W PA in a frequency band of 1.4 - 1.6 GHz is designed and linearized. By fabricating both the reference and linearized PAs and performing measurements under several conditions, it is experimentally demonstrated that applying the proposed scheme, thanks to its adjustability, highly linearizes the PA in a wide bandwidth and a wide range of output power.

A wideband reconfigurable analog predistorter based on a new wideband tunable impedance matching network

AbstractA wideband reconfigurable analog predistorter (APD), which can maintain the tuning capability in wideband frequency, is proposed in this letter. First, the requirements of tunable impedance matching network (TIMN) used in the wideband reconfigurable APD is given. Second, a new wideband TIMN is analyzed, and the coverage the proposed TIMN is given. Then the circuit parameters of the TIMN can be appropriately selected to maintain the coverage of the TIMN meeting the requirement at needed frequencies. To validate the proposed TIMN, a wideband reconfigurable APD operating at Q‐band (46.5–51.5 GHz) is designed, fabricated, and measured. The measured results show good agreement with the analysis. The minimum tuning range of gain and phase conversions are 12.5 dB and 46.5, respectively.

A Millimeter-Scale Crystal-Less MICS Transceiver for Insertable Smart Pills.

This paper presents a millimeter-scale crystal-less wireless transceiver for volume-constrained insertable pills. Operating in the 402-405 MHz medical implant communication service (MICS) band, the phase-tracking receiver-based over-the-air carrier recovery has a ±160 ppm coverage. A fully integrated adaptive antenna impedance matching solution is proposed to calibrate the antenna impedance variation inside the body. A tunable matching network (TMN) with single inductor performs impedance matching for both transmitter (TX) and receiver (RX) and TX/RX mode switching. To dynamically calibrate the antenna impedance variation over different locations and diet conditions, a loop-back power detector using self-mixing is adopted, which expands the power contour up to 4.8 VSWR. The transceiver is implemented in a 40-nm CMOS technology, occupying 2 mm2 die area. The transceiver chip and a miniature antenna are integrated in a 3.5 × 15 mm2 area prototype wireless module. It has a receiver sensitivity of -90 dBm at 200 kbps data rate and delivers up to - 25 dBm EIRP in the wireless measurement with a liquid phantom.

An Impedance Matching Strategy for Micro-Scale RF Energy Harvesting Systems

Radio frequency (RF) energy harvesting is widely adopted as an alternative source of energy to power a wireless sensor node or an Internet of Things (IoT) node. In order to extract maximum power from an RF energy source, variations in an RF to DC converter (RDC) input impedance with input power should be taken into account. This brief demonstrates that a tunable impedance matching strategy is essential to track the changes in input impedance to ensure maximum power transfer across the desired input power levels. A two-state tunable matching network is proposed to track variations in input impedance with the input power of an RDC with a load of 10 kΩ, and at an operating frequency of 953 MHz. The proposed impedance matching network and the RDC are designed using 0.18-μm CMOS technology node. Circuit simulations demonstrate that the proposed matching strategy extends the input power range over which maximum power transfer occurs by 5 dBm and 13 dBm in comparison to a fixed matching network designed at -24 and -18 dBm, respectively.

Adaptive 5G Architecture for an mmWave Antenna Front-End Package Consisting of Tunable Matching Network and Surface-Mount Technology

Adaptive 5G architecture consisting of three functional sections (four antenna components, tunable matching network (TMN), and radio frequency (RF) front-end package) is proposed, analyzed, and verified. In the 5G millimeter-wave (mmWave) spectrum, the RF performance is highly dependent on the specific antenna package technology. However, compact antenna packages, oftentimes, result in undesired interference between the antenna elements. This eventually leads to severe RF performance degradation. For the first time in the literature, an mmWave 5G RFIC and the TMN are integrated for efficient operation that is applicable to real-life 5G mobile devices. Moreover, the proposed antenna-in-package (AiP) architecture enables independent frequency control at multiple frequencies. The proposed solution is simulated and measured at the system level. As a result, the devised AiP solution exhibits a simulated effective isotropic radiated power (EIRP) of 22.05–23.96 dBm at the cumulative distribution function (CDF) of 50% by applying the conducted power of 17 dBm (per channel), and the peak gain of the antenna exhibits 13.7 dBi at 27 GHz (state A) and 12.6 dBi at 28 GHz (state B) with an amplifier having an output power of 5 dBm.

Dynamically Reconfigurable Microwave Circuits Leveraging Abrupt Phase-Change Material

This article proposes a concept for dynamically reconfigurable distributed microwave circuits by leveraging the abrupt conductivity transition in phase-change materials (PCM). Metallic surface-inclusions (<<$\lambda$) are embedded in the PCM film$-$vanadium dioxide (VO2)$-$to provide low-loss and reconfigurability. To validate this concept, a variety of co-planar waveguide transmission lines are designed and fabricated with metallic surface-inclusions in VO2 films, and the lines' performance are characterized up to 50 GHz. The measured results are used to develop a transmission-line based model and an equivalent circuit model of the VO2 with surface-inclusions to aid in the rapid design of new structures. Additionally, an electromagnetic model was developed and indicates that loss can be close to that of conventional metallic distributed circuits with 100 to 200 nm thick VO2 films. With these thicker films, two practical realizations of this concept were designed and simulated: a tunable dipole from 2.13 to 9.07 GHz and a tunable triple-stub matching network from 5 to 40 GHz with high $|\Gamma|$. Therefore, the proposed method appears viable for the realization of arbitrary programmable distributed circuits and antennas in the microwave and low-millimeter-wave bands.

A reconfigurable analog predistorter using tunable impendence matching network

A reconfigurable analog predistoter (APD) based on tunable impedance matching network (TIMN) is proposed in this brief. Firstly, a design method to specific gain and phase conversions is introduced. The equivalent circuit parameters of the impedance matching network (IMN) can be computed for the desired gain and phase conversions. To simplify the design, these parameters can be transformed to the terminal impedance of the IMN. Then the complicated nonlinear circuits design can be transformed to the IMN design. Secondly, a reconfigurable APD using the proposed method is presented for high tuning capability. By designing the coverage area of the TIMN, an experimental reconfigurable APD for traveling-wave tube amplifiers (TWTAs) & solid-state power amplifiers (SSPAs) is designed and fabricated. The fabricated APD shows more than 21 dB tuning range of gain conversion and 114° tuning range of phase conversion in 5.7–6.3 GHz. Good linearity improvement has been obtained for a 45 W C-band TWTA and a 5 W SSPA only by changing the APD bias voltage.

Tunable Matching Networks Based on Phase-Switched Impedance Modulation1

The ability to provide accurate, rapid, and dynamically controlled impedance matching offers significant advantages to a wide range of present and emerging radio-frequency (RF) power applications. This article develops a new type of tunable matching network (TMN) that enables a combination of much faster and more accurate impedance matching than is available with conventional techniques and is suitable for use at high power levels. This implementation is based on a narrow-band technique, termed here phase-switched impedance modulation (PSIM), which entails the switching of passive elements at the RF operating frequency, effectively modulating their impedances. The proposed approach provides absorption of device parasitics and zero-voltage switching (ZVS) of the active devices, and we introduce control techniques that enable ZVS operation to be maintained across operating conditions. A prototype PSIM-based TMN is developed that provides a 50-Ω match over a load impedance range suitable for inductively coupled plasma processes. The prototype TMN operates at frequencies centered around 13.56 MHz at input RF power levels of up to 200 W.

Broadband class-E power amplifier design using tunable output matching network

This paper presents a design of a broadband high-efficiency Class-E power amplifier (PA) with a tunable output matching network (OMN). The OMN contains two main parts: The first part is a Tunable Band-Pass Filter (T-BPF) that determines the center frequency of the PA’s operational bandwidth. And the first part is a fixed matching network that transforms the input impedance of the second part (50 Ω) to an optimum impedance value of transistor’s drain. The tuning process of the BPF is realized using a Varactor Diode Stack. By changing the bias voltage of the varactor diodes, the center frequency of T-BPF can move throughout 1–2.55 GHz bandwidth. The GaN HEMT CGH40010F from Cree has been selected due to its wide bandwidth, high efficiency, and high achievable gain for PA design. Simulation results show an output power of 40–41.5 dBm, Drain Efficiency (DE%) of 57.2–81.2% and transducer power gain of 10–12.5 dB across 1–2.55 GHz (87.3% fractional bandwidth). The proposed design outperforms previous tunable and fixed power amplifiers regarding bandwidth and efficiency.

A 1.5 kW Radio-Frequency Tunable Matching Network Based on Phase-Switched Impedance Modulation

Dynamically-tunable impedance matching is a key feature in numerous radio-frequency (RF) applications at high frequencies (10 s of MHz) and power levels (100s–1000 s of Watts and above). This work develops techniques that enable the design of high power tunable matching networks (TMN) that can be tuned orders of magnitude faster than with conventional tunable impedance matching techniques, while realizing the high power levels required for many industrial applications. This is achieved by leveraging an emerging technique – known as phase-switched impedance modulation (PSIM), which involves switching passive elements at the rf operating frequency – that has previously been demonstrated at rf frequencies at up to a few hundred Watts. In this paper, we develop design approaches that enable it to be practically used at up to many kilowatts of power at frequencies in the 10 s of MHz. A detailed analysis of the factors affecting the losses as well as the tradeoffs of a basic PSIM-based element is provided. Furthermore, it is shown how incorporating additional stages to the PSIM-based element, including impedance scaling and / or the addition of series or shunt passive elements, influences the losses and enables the efficient processing of high power levels given the limitations of available switches. A PSIM-based TMN that matches load impedances to 50 $\,\Omega$ and delivers up to 1.5 kW of power at frequencies centered around 13.56 MHz is implemented and tested over a load impedance range suitable for various industrial plasma processes.

A Real-Time Range-Adaptive Impedance Matching Utilizing a Machine Learning Strategy Based on Neural Networks for Wireless Power Transfer Systems

In this article, the implementation of a machine learning (ML) strategy based on neural networks for the real-time range-adaptive automatic impedance matching of wireless power transfer (WPT) applications is discussed. This approach for the effective prediction of the optimal parameters of the tunable matching network and the selection of range-adaptive transmitter coils (Tx) is introduced in this article, aiming to achieve an effective automatic impedance matching over a wide range of relative distances. We propose a WPT system consisting of a tunable matching circuit and three Tx coils that have different radii and are simultaneously controlled by trained neural network models, returning an output set of matching capacitances as well as the optimal single transmitter among the three transmitters. In addition, a proof-of-concept prototype of the entire real-time range-adaptive automatic impedance-matching system is built and characterized. Finally, the proposed approach achieves a power transfer efficiency (PTE) of around 90% for ranges within 10–25 cm.

Position-Insensitive Wireless Power Transfer Based on Nonlinear Resonant Circuits

Near-field resonant-based wireless power transfer (WPT) technology has a significant impact in many applications ranging from charging of biomedical implants to electric vehicles (EVs). The design of robust WPT systems is challenging due to its position-dependent power transfer efficiency (PTE). In this paper, a new approach is presented to address WPT's strong sensitivity to the coupling factor variation between the transmit and receive coils. The introduced technique relies on harnessing the unique properties of a specific class of nonlinear resonant circuits to design position-insensitive WPT systems that maintain a high PTE over large transmission distances and misalignments without tuning the source's operating frequency or employing tunable matching networks, as well as any active feedback/control circuitry. A nonlinear-resonant-based WPT circuit capable of transmitting 60 W at 2.25 MHz is designed and fabricated. The circuit maintains a high PTE of 86% over a transmission distance variation of 20 cm. Furthermore, transmit power and PTE are maintained over a large lateral misalignment up to ±50% of the coil diameter and angular misalignment up to ±75°. The new design approach enhances the performance of WPT systems by significantly extending the range of coupling factors over which both load power and high PTE are maintained.