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Time-varying networks, consisting of lumped elements, such as resistors, capacitors, and inductors, actively modulated in time, have introduced a host of novel wave phenomena and witnessed remarkable development during recent years. This paper investigates the scattering from a time-varying capacitor and how such a load can be fully reflectionless when the capacitance is suitably modulated in time. We analytically derive the required temporal dependence of the capacitance and show how in contrast to other techniques it avoids extreme and negative values and, as a result, can be implemented in a feasible way, when the capacitor is charged with a DC voltage source. We derive for the first time the energy balance of such a reflectionless time-varying capacitor. Such energy balance is general in the sense that it is not restricted to incoming pulses with specific temporal shapes. Also, it unveils the interesting feature that, although the reflected signal is canceled, the energy of the incoming pulse is completely transferred to the modulation source instead of being stored in the capacitor. Our findings clarify scattering of waves from time-varying capacitors and open up a new way to matching of broadband pulses and converting electromagnetic energy to a different form of energy such as mechanical energy.

This article presents analysis, design details, and simulation results of an impedance matching network designed for a 112 Gb/s pulse-amplitude-modulation-4 (PAM4) receiver using an LC- π structure. We designed the bonding wire as a part of the matching network, which reduced design pressure on the equalizer as there will be no need to compensate the loss of the chip package. To avoid robustness issues caused by the fluctuation of the bonding wire inductance, the matching network is designed to bw adjustable by the capacitance on PCB and the terminal resistance. We analyzed the parasitics in the layout and the influence of nearby and dummy metals and obtained reliable simulation results through electromagnetic field simulation. This matching network is designed with a 28 nm CMOS process. Post-layout simulation results show that with bonding wire inductance changing from 150 pH to 250 pH, it can always meet CEI-112G-XSR-PAM4 Extra Short Reach Interface requirements. [ABSTRACT FROM AUTHOR]

Acoustic logging while drilling (LWD) technology plays an important role in oil and gas exploration and development. Compared to traditional wireline logging, LWD must address more additional crucial problems, such as great noise confusions. This paper studies a series of technologies to improve the transmitting performances of LWD tools. First, we verified that the shear wave remote detection technology successfully adopted in wireline logging was also suitable for LWD, which could significantly expand its detection range. In addition, we calculated its dominant excitation frequency bands, which were different with wireline logging. Second, a class AB push–pull excitation circuit was designed. The results demonstrated that this circuit could obtain ideal excitation signals for LWD transmitting transducers. Furthermore, the signal shapes, excitation frequencies and cycle amounts are easily to adjust. In this study, we proposed a broadband impedance matching technology to solve the impedance mismatching problem between the excitation circuits and the excitation transducer. Acoustic experiments showed that this technology improved emitting powers of LWD transducers significantly. [ABSTRACT FROM AUTHOR]

Using ideas from Chu and Bode/Fano theories, we characterize the maximum achievable rate over the single-input single-output wireless communication channels under a restriction on the antenna size at the receiver. By employing circuit-theoretic multiport models for radio communication systems, we derive the information-theoretic limits of compact antennas. We first describe an equivalent Chu’s antenna circuit under the physical realizability conditions of its reflection coefficient. Such a design allows us to subsequently compute the achievable rate for a given receive antenna size thereby providing a physical bound on the system performance that we compare to the standard size-unconstrained Shannon capacity. We also determine the effective signal-to-noise ratio (SNR) which strongly depends on the antenna size and experiences an apparent finite-size performance degradation where only a fraction of Shannon capacity can be achieved. We further determine the optimal signaling bandwidth which shows that impedance matching is essential in both narrowband and broadband scenarios. We also examine the achievable rate in presence of interference showing that the size constraint is immaterial in interference-limited scenarios. Finally, our numerical results of the derived achievable rate as function of the antenna size and the SNR reveal new insights for the physically consistent design of radio systems. [ABSTRACT FROM AUTHOR]

Tight integration of capacitive micromachined ultrasonic transducer (CMUT) arrays with integrated circuits can make active impedance matching feasible for practical imaging devices. In this article, negative capacitance-based impedance matching for CMUTs is investigated. Simple equivalent circuit model-based calculations show the potential of negative capacitance matching for improving the bandwidth along with electrical power transfer and acoustic reflectivity, but the model has limitations especially for acoustic reflectivity evaluation. For more realistic results, an experimentally validated CMUT array model is applied to a small 1-D CMUT array operating in the 5–15 MHz range. The results highlight the difference between electrical power transfer and acoustic reflectivity as well as the tradeoffs in signal-to-noise ratio (SNR). According to the results, ideal negative capacitance termination matched to the CMUT capacitance provides the broadest bandwidth and highest SNR if acoustic or electrical reflections are of no concern. On the other hand, negative capacitance and resistance matching to minimize acoustic reflectivity provides both lower reflection and closer to ideal SNR as compared with electrical power matching. It is observed that acoustic matching also reduces acoustic crosstalk and improves array uniformity. While several challenges for integrated circuit implementation are present, negative capacitance-based impedance matching can be a viable broadband active impedance matching method for CMUTs operating in conventional and collapsed mode as well as other ultrasound transducers with mainly capacitive impedance. [ABSTRACT FROM AUTHOR]

When the broadband impedance matching techniques are applied to the Wilkinson power divider, it operates in a larger frequency range and covers many communication bands. In this study, an ultra‐wideband (UWB) multisection Wilkinson power divider (WPD) circuit has been designed. Euler method has applied to the circuit that had equal power dividing feature on its two output ways. In the three‐section of the WPD, the Euler function has been modeled as a reflection coefficient on the output branches. The Euler polynomials have been used to calculate the characteristic impedance of each section. The isolation resistors have been calculated by odd‐even mode analysis according to the line impedances. In the Euler WPD, center frequency was 2.45 GHz and the limits for the return loss and isolation was selected as 15 dB and 20 dB, respectively. The bandwidth was measured as 0.75 to 3.80 GHz. The percent bandwidth of the WPD was calculated as 124.5%. Along the operation band interval, the minimum insertion loss measured lower than 0.75 dB. The design has been compared with a quarter wave (QW) WPD. It has been shown that the Euler method can achieve higher bandwidth, lower return loss and better Isolation than the conventional WPD. [ABSTRACT FROM AUTHOR]

Featured Application: Miniaturized broadband antennas for wireless communication devices A non-Foster circuit (NFC) is known as an active broadband matching technique to improve the impedance matching bandwidth of an electrically small antenna (ESA). There has been a vast amount of papers that report the generation of negative impedance using an NFC and its effectiveness on broadband antenna matching. However, only a few discussed its impact on the signal-to-noise-ratio (SNR), which is one of the most important figures-of-merit for a wireless communication system. In this paper, the SNR enhancement due to an NFC was measured and discussed. An NFC was carefully designed to have a low dissipation loss and to meet the stability conditions. The optimized NFC design was fabricated and applied to an ESA length of λ⁄15 at a frequency range of 150 to 300 MHz. The measured results showed that the NFC enhanced the received power of the antenna system by more than 17 dB. However, due to the noise added by the NFC, the SNR enhancement was not guaranteed for some frequency points. Nevertheless, an average of 7.3 dB of SNR improvement over the frequency band of interest is possible based on the experiment result. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on the broad band impedance matching of an ultrawideband (UWB) antenna using multiple resonating structures. The initial structure of the antenna consists of a circular patch with radius 8.1 mm fed by 50 Ω strip line feed, which is modified further with multiple resonating structures to improve overall bandwidth, impedance matching, return loss, gain and radiation efficiency. The antenna is designed using FR4 substrate having relative permittivity of 4.4 and has a small size of 30 mm × 30 mm × 1.6 mm. Experimental results show that the designed antenna covers the entire unlicensed UWB range from 3.1 to 10.6 GHz with five resonating dips at 3.4 GHz, 5 GHz, 6.5 GHz, 7.7 GHz and 9.3 GHz along with low return loss values (below − 20 dB) and improved input impedance of approximately 50 Ω at all frequencies. Further the proposed antenna shows maximum gain and radiation efficiency values of 6.1 dB and 94% with stable radiation pattern over the entire band of operation. The proposed antenna is designed by using computer simulation technology software and then the prototype is fabricated and tested. Further the simulated results are verified with experimental results which are in good agreement. [ABSTRACT FROM AUTHOR]

In this paper, we describe the design, fabrication, and measurement results of a non-Foster circuit for improving the wideband matching and receiver power of small antennas. The antennas under consideration are a small monopole antenna and a small inverted F antenna. These antennas experience excessive C and L respectively; which makes it difficult to match their wideband impedance performance. To cancel out the excess C, a negative C non-Foster circuit is designed whereas a negative L non-Foster circuit is designed to cancel out the excess L. An important factor in the design of a non-Foster circuit is the stability, which is obtained by simultaneously considering the open circuit stability condition and transient response. According to the simulation, the optimized non-Foster circuit operates with negative C and L at 100～500 MHz, and it is fabricated with a PCB process and applied to the antennas. The reflection coefficients of the small monopole antenna and the inverted F antenna with non-Foster circuits are less than −10 dB at 150～400 MHz and 220～330 MHz, respectively. In addition, we measured the receiver power using antennas with non-Foster circuits. The small monopole antenna improved by 10.3 dB on average while the small inverted F antenna improved by 7.5 dB, at this frequency band. [ABSTRACT FROM AUTHOR]

To obtain qualified logging while drilling (LWD) data, a new acoustic LWD tool was designed. Its overall design is introduced here, including the physical construction, electronic structure, and operation flowchart. Thereafter, core technologies adopted in this tool are presented, such as dominant exciting wave bands of dipole source, a sine wave pulse excitation circuit, broadband impedance matching, and an intellectualized active reception transducer. Lastly, we tested this tool in the azimuthal anisotropy module well, calibration well, and normal well, working in the model of the cable, sliding eye, and logging while drilling. Experiments showed that the core technologies achieved ideal results and that the LWD tool obtained qualified data.

A non-Foster circuit (NFC) is known as an active broadband matching technique to improve the impedance matching bandwidth of an electrically small antenna (ESA). There has been a vast amount of papers that report the generation of negative impedance using an NFC and its effectiveness on broadband antenna matching. However, only a few discussed its impact on the signal-to-noise-ratio (SNR), which is one of the most important figures-of-merit for a wireless communication system. In this paper, the SNR enhancement due to an NFC was measured and discussed. An NFC was carefully designed to have a low dissipation loss and to meet the stability conditions. The optimized NFC design was fabricated and applied to an ESA length of λ⁄15 at a frequency range of 150 to 300 MHz. The measured results showed that the NFC enhanced the received power of the antenna system by more than 17 dB. However, due to the noise added by the NFC, the SNR enhancement was not guaranteed for some frequency points. Nevertheless, an average of 7.3 dB of SNR improvement over the frequency band of interest is possible based on the experiment result.

This paper presents a new methodology for synthesis of broadband matching networks based on Clonal Selection Algorithms (CSA). This metaheuristic uses the hypermutation as only variation operator resulting in a gradual evolving of the network topology. A closed form expression for the transducer power gain (TPG) sensitivity with respect to the component values is employed, in such a way that the effects of the components tolerance on the matching network performance can easily be quantified. The evolvable function proposed is single-objective and eliminates the difficult task of assigning appropriate weights to parameters. The evaluation of the TPG sensitivity enables the designer to identify and remove irrelevant components of the circuit, simplifying it. The efficiency of the methodology is tested in two cases found in the literature: the traditional project of impedance matching for a simple RLC load proposed by Fano [1]; and a real synthesis of impedance matching network for a monopole whip antenna, proposed in [2]. The results are compared with other existing methods. [ABSTRACT FROM PUBLISHER]

This paper describes a fully integrated E-band power amplifier (PA) in 40-nm CMOS. The design and layout of the unit PA stage is optimized to achieve high output power while maintaining high power gain. A broadband parallel-series power combiner is proposed to provide the PA stage optimum load impedance across the complete E-band. The complete PA achieves a measured saturated output power of 20.9 dBm with more than 15-GHz small-signal -3-dB bandwidth and 22% power-added efficiency (PAE) at 0.9-V supply. The in-band variation of -1-dB compressed power (P1\ {dB}) is only \pm0.25 dB. This is the first reported silicon-based PA that covers both 71–76- and 81–86-GHz bands with uniform gain, output power, and PAE. [ABSTRACT FROM AUTHOR]

Traditional radio receivers were narrowband and dedicated to a single frequency band exploiting LC tanks, whereas software defined radios target a flexibly programmable frequency. The broadband noise cancelling circuit technique has proven useful to achieve this target, as it breaks the traditional trade-off between low noise and broadband impedance matching. Different variants exist, with noise cancellation in the voltage or current domain, either at RF or after frequency translation to baseband. This article reviews the development of the noise cancelling technique and its role in inductorless interference robust software defined radio receivers. [ABSTRACT FROM AUTHOR]

A new Doherty amplifier configuration with an intrinsically broadband characteristic is presented based on the synthesis of key ideas derived from the analyses of the load modulation concept and the conventional Doherty amplifier. Important building blocks to implement the proposed Doherty amplifier structure are outlined, which include the quasi-lumped quarter-wave transmission line, as well as the Klopfenstein taper for broadband impedance matching. A 90-W GaN broadband Doherty amplifier was designed and fabricated and achieved an average peak output power of 49.9 dBm, an average gain of 15.3 dB, and average peak and 6-dB back-off efficiencies of 67.3% and 60.6%, respectively, from 700 to 1000 MHz (35.3% bandwidth). The amplifier is shown to be highly linearizable when driven with 20-MHz WCDMA and long-term evolution signals, achieving adjacent channel power ratio of better than -48 dBc after digital predistortion. [ABSTRACT FROM AUTHOR]

The modeling and design is presented of a new kind of circuit analogue absorber, which intercepts the electromagnetic waves through a two-dimensional periodic array of microstrip lines loaded with lumped circuit elements. For a plane wave incidence of polarization perpendicular to the strips, virtual magnetic walls are formed between the strips, and the geometry can be divided into many identical unit-cells. We first study the propagation characteristics of the unit-cell using the singular integral equation method. An RC network is then proposed to match this array with the free space and to dissipate the intercepted energy over a wide frequency range. The complete design procedure is explained through a design example that exhibits a bandwidth of 113% while the absorber thickness is less than 10% of the free space wavelength at the lowest operating frequency. [ABSTRACT FROM AUTHOR]

In a proximity-coupled microstrip antenna, when a laminate used is too thick for the antenna layer, the coupling will be decreased. And it is hard to achieve broadband impedance matching. The authors present a method to optimize impedance matching through narrow cavity backed configuration. A prototype antenna is designed with this method and fabricated. Simulation and measurement results indicate that the bandwidth of the antenna exceeds 40% (VSWR < 2.0. The antenna has a larger effective coupling as compared with the conventional proximity-coupled antenna without the narrow cavity backed configuration. It is easier to enhance the bandwidth with a thicker laminate. Meanwhile, this antenna is benefit for manufacturing and assembling to an array due to its simple configuration. [ABSTRACT FROM AUTHOR]

A compact broadband quasi‐planar rectangular ring‐cavity (RRC) power divider is presented. To realise the broadband impedance matching, the novel inserted ground waveguide probe structure is used. The equivalent circuit is given. The presented RRC power divider has been designed, fabricated and measured. The measured 15 dB return loss bandwidth is about 7.5 GHz (from 6.6 to 14.2 GHz). The measured results show reasonable agreement with the simulated one. [ABSTRACT FROM AUTHOR]

A simple and compact ultrawideband (UWB) aperture antenna with extended band-notched designs is presented. The antenna consists of a rectangular aperture on a printed circuit board ground plane and a T-shaped exciting stub. The proposed planar coplanar waveguide fed antenna is easy to be integrated with radio-frequency/microwave circuitry for low manufacturing cost. The antenna is successfully designed, implemented, and measured. A compact aperture area of 13 times23mm2 is obtained with promising performances, including broadband matched impedance, stable radiation patterns, and constant group delay. The correlation between the mode-based field distributions and radiation patterns is discussed. Extended from the proposed antenna, three advanced band-notched (5-6 GHz) designs are also presented as a desirable feature for UWB applications [ABSTRACT FROM PUBLISHER]

This paper presents a sub-mW ultra-wideband (UWB) fully differential CMOS low-noise amplifier (LNA) operating below 960 MHz for sensor network applications. By utilizing both nMOS and pMOS transistors to boost the transconductance, coupling the input signals to the back-gates of the transistors, and combining the common-gate and shunt-feedback topologies, the LNA achieves 13 dB of power gain, a 3.6 dB minimum noise figure, and -10 dBm of 11P3 with only 0.72 mW of power consumption from a 1.2 V supply. [ABSTRACT FROM AUTHOR]

A new design framework for implantable antennas to reduce detuning effects due to various dielectric properties is presented. Conventionally, in order to overcome the detuning effects, it is highly demanded to have a broadband impedance matching to compensate the frequency shift. However, achieving a wider impedance bandwidth leads to larger antenna dimensions, and lack a mathematical treatment to optimise implantable antennas against the variation of tissue properties to date. A new methodology based on robust parameter design is proposed to cope with the detuning effects. Instead of designing the antenna in one single tissue environment, the proposed technique analyses the variation of dielectric properties in distinct tissue environments. The optimised performances show that robust impedance matching in the medical implant communication services band is achieved, although the dielectric constant varies from 35 to 55. Simulated and measured results are presented to demonstrate the validity of the proposed design methodology. [ABSTRACT FROM AUTHOR]

To obtain qualified logging while drilling (LWD) data, a new acoustic LWD tool was designed. Its overall design is introduced here, including the physical construction, electronic structure, and operation flowchart. Thereafter, core technologies adopted in this tool are presented, such as dominant exciting wave bands of dipole source, a sine wave pulse excitation circuit, broadband impedance matching, and an intellectualized active reception transducer. Lastly, we tested this tool in the azimuthal anisotropy module well, calibration well, and normal well, working in the model of the cable, sliding eye, and logging while drilling. Experiments showed that the core technologies achieved ideal results and that the LWD tool obtained qualified data. [ABSTRACT FROM AUTHOR]