Back Off Research Articles

A Wideband Efficiency-Enhanced Class-G Digital Power Amplifier for IoT Applications

This letter presents a wideband digital power amplifier (DPA) with Class-G technique to enhance back-off efficiency for Internet-of-Things (IoT) applications. The switched-capacitor power amplifier topology is adopted for high linearity performance. A wideband matching network is proposed to achieve 0.54–0.95-GHz frequency coverage for 802.11ah and narrowband IoT standards. The measurement results demonstrate a flat frequency response with only 0.5-dB power deviation over 0.54–0.95 GHz. The DPA achieves the peak output power of 23.5 dBm with 42.7% peak PAE and 32.8% PAE at 6-dB back off. When amplifying an 8-MHz 64 quadratic-amplitude modulation 802.11ah signal at 800 MHz, it obtains −28.4-dB error vector magnitude and 30.1% average PAE at 16.5-dBm average output power.

Economically Optimal Input Design Approach for Identification of Constrained Processes

Input design is the process of designing informative inputs which maximizes the information about system dynamics using minimal cost and resources in a system identification experiment. In this work, we focus on designing inputs based on the economic framework for identification of constrained processes. The process is nominally constrained and feasibility during identification is ensured by “backing off” (or moving away) from the active constraints. The economic cost or penalty due to the “back-off” is minimized while ensuring feasibility and satisfying constraints on the quality of the identified model. The proposed economic based formulation results in a nonconvex optimization problem. This problem can be solved using the bisection algorithm for single input–single output (SISO) systems. We present a two-stage iterative solution algorithm to solve for multi-input–multi-output (MIMO) systems where a convex optimization problem is solved at each stage. The optimal input is realized as a white noise passing through an M-tap filter. The filter coefficients are obtained by a noniterative spectral factorization technique. The efficacy of the proposed approach has been successfully demonstrated in a mass spring damper system as well as in a Van der Vusse reactor system.

Internal combustion engine efficiency enhancer by using hydrogen

ABSTRACTMost cars work by burning a liquid fuel with oxygen. Fuel is squirted into a chamber with air, it evaporates into a gaseous mixture, it lights, the burning gases expand, which in turn produces motive power. The car begins to move. The Problem is that becomes more expensive. With these rising costs of gasoline and diesel fuel, we decided to try using hydrogen as a means of alternative power for the car. With a hydrogen generator, the idea is to replace some of the gasoline with hydrogen. Gaseous hydrogen burns readily and produces loads of power. The idea is that the extra boost (not replacement) in gasoline power from the hydrogen would cause a gasoline-burning engine to back off on using so much gasoline. This in turn should result in less gas being burned. This paper brings about hydrogen fuel generator, whose fuel generated can be used as alternate source of fuel.

Postmatching Doherty Power Amplifier With Extended Back-Off Range Based on Self-Generated Harmonic Injection

In this paper, an asymmetric drain biased postmatching Doherty power amplifier (DPA) using harmonic injection is proposed for further back-off extension. The injected harmonic components are generated by the two active devices. Aided by the proposed harmonic injection network, drain waveform amplitude modulation for both devices can be achieved at saturation, which results in enhanced saturated power for both carrier and peaking devices, while carrier back-off power remains unchanged. As a consequence, the back-off region is extended. Moreover, the power utilization factor of the asymmetric drain biased DPA is also improved. A DPA for wideband code-division multiple access systems was designed and fabricated based on commercially available gallium nitride HEMT (Cree CGH 40010F) devices to validate the proposed technique. Measured results of the proposed DPA demonstrated that operation at 10-dB back off is possible between 1.6 and 1.9 GHz, with efficiency better than 46%.

Back off Specialists

A New Spine Pathway 2016-2017 Advanced practice physiotherapy skills used prior to First Assessment Specialist referrals to orthopaedics Vision : accessibility, partnerships, excellent clinical outcomes, timely access. Previous model : Overloaded Orthopaedic services, fiscal restraints, unnecessary admissions/ tests, onsite underutilised expertise. Changes : Triage referrals. Orthopaedic specialists direct patients to Physiotherapist-led back clinic after paper triage only Data tracked. Educational tools Developed home program templates, back booklet, exercise sheets Integration and communication of pathways with other services Outcomes Keele STarT Back, VAS Target population : High needs communities, throughout Hawkes Bay Results : Reduced speicialist appointment/investigations: 87% avoided, 119 fewer MRIs 88 fewer spinal injections Accessible service : average interventions 3.4 Average wait time 41.6 days. 542 people offered assessment in first year Avoidable hospital admissions : trending down ( HRT data 2016) Client satisfaction high: 79% rate 10/10 Outcomes : at discharge 81% self managing well, minimal or no symptoms, 7% referred on to community support groups, 12% referred to FSA/specialist service Patient reported average Outcomes : Pain scores improved 23.9%, function 17.2%, self management improved 33.8% Sustainability : Further 0.5 equivalent advanced pracitioner employed mid 2016. data consistent over 18 months Enhancement of client services : more clinics opening in outlying community settings. Message for others : Expert Physiotherapists work with hospital specialists, staff, referrers, and community to ensure clients receive accessible appropriate expert care and back up. This service saves money, reduces diagnostic interventions, Orthopaedic Specialist time, while producing excellent outcomes. Treatment emphasising self-care, lifestyle change, supported by excellent educational tools, works for all stakeholders.

IW-MAC: a invite and wait MAC protocol for power efficient wireless sensor networks

Energy conservation in MAC protocol is a focal point for researchers for a long time. One of the main reasons is that sensor nodes are left unmonitored for a phase of time with only the inbuilt battery as the sole source of energy power. It’s the onus of MAC protocol to efficiently consume this available source of energy. It must be carefully designed in a way there is no wastage of energy source. Control packets in wireless sensor networks not only degrade packet transmission time but also suck out energy from the energy source built in the wireless sensor nodes. When the control packets collide and there is a need resend the control packets it adds up to further energy loss. A better energy efficient MAC protocol must aim at reducing the adoption of control packets following around the network instead give way for data packets to flow around. The energy efficient deteriorates when the nodes undergo too many overhead steps in MAC protocol thereby transmitting lesser packets in given time. In this paper a new protocol namely IWMAC-invite and wait MAC protocol which leverages efficient use of battery power in wireless sensor nodes. With IWMAC the nodes are enabled to transmit minimal control packets and deliver more data packets in a given time. The energy of the nodes are used primarily in actual data transmissions rather than succumbing to overhead of control packets, channel reservation, back off which drains out the energy source in sensor nodes.

A New Approach to Design a Broadband Doherty Power Amplifier via Dual-Transformation Real Frequency Technique

A novel dual-transformation simplified real frequency technique is proposed in this paper to synthesize a broadband Doherty power amplifier (DPA). The proposed method can realize the co-design of the carrier and peaking output matching networks to achieve dual-impedance transformation at back-off (BO) and saturation simultaneously. To realize this method, a generalized driving point function with different loads of the matching network is proposed, and weight factors are adopted to combine the separate target functions to form a united one. Compared with conventional designs, no initial guess is required and additional compensating lines are eliminated to improve the performance of the DPA. Based on the proposed technique, a broadband DPA is designed and fabricated across 2.2-3.7 GHz (51% fractional bandwidth). The measurement results show that the designed DPA has a 6-dB BO efficiency of 45%-53% and a saturated output power of 43-44.6 dBm over 1.5 GHz bandwidth. Various modulated signals including 80-MHz long-term evolution-advanced signal and concurrent dual-band signal are employed to validate the DPA. In this way, the DPA can achieve an average efficiency of 45.3%-55.9% at 6.5-dB BO with the adjacent channel leakage ratio levels better than -48.6 dBc by utilizing digital predistortion.

The state of land seismic

It has been said that when the oil and gas industry catches a cold, geophysical contractors get the flu, and the equipment manufacturers get pneumonia. This metaphor describes the leveraged financial impact of the periodic collapses in the price of oil. The oil companies cut back on exploration, and the contractors reduce the number of active crews. Surplus equipment is warehoused and the contractors stop buying hardware altogether. Why buy gear when you have it on the shelf? The low oil prices have decimated seismic system sales. With a few exceptions, hardly anyone is buying anything except in less-developed nations where oil is essential to the economy. This is happening during what would normally be exciting times in the industry. For example, in the last few years the average number of channels on a seismic crew has increased from a few thousand to tens of thousands. Bigger and denser spreads have become common as new processing algorithms have been developed to give interpreters better looks at the subsurface. Are things getting better? If you follow the daily news from industry magazines, it appears that the oil companies are learning to live with $50 oil. For many, profits and cash flow are positive while reserves are declining. The inventory of drillable prospects is diminishing and geophysical contracting is looking up. Some are profitable and a few crews are being brought back off furlough. Will the equipment manufacturers be next for improved performance?

A Design Approach to Maximize the Efficiency <italic>vs.</italic> Linearity Trade-Off in Fixed and Modulated Load GaN Power Amplifiers

This paper proposes a design method to minimize the phase distortion (AM/PM) in gallium nitride (GaN) power amplifiers (PAs) without significantly worsening other key features such as efficiency, amplitude distortion, and gain. The design strategy consists in the adoption of a smart two-stage architecture, in which the driver stage is devised to act as a sort of “analogue AM/PM predistorter” for the final one. Accounting for the actual trend in PA solutions, the proposed approach has been fine-tuned to implement a two-way class AB PA and a Doherty PA (DPA) for backhaul radio links. Both circuits, realized on the same 0.25- $\mu \text{m}$ GaN technology and in monolithic form, have fully been characterized with continuous wave and modulated signals. At 7 GHz, the DPA shows 38 dBm of saturated output power and less than 3° of phase distortion with a power-added efficiency (PAE) higher than 41% in 6 dB of power back off. The class AB PA achieves almost the same level of saturated output power and maximum PAE, with an inevitable lower efficiency in back-off operation, whereas the registered AM/PM is lower than 1.5°. Moreover, when tested with modulated signals, at 32 dBm of average output power and without any digital predistortion, the DPA shows a spectral regrowth of around 36 dBc and a PAE of 40%, whereas the class AB PA achieves 40 dBc and 30%, respectively.

Throughput Analysis of LAA and Wi-Fi Coexistence Network With Asynchronous Channel Access

The licensed-assisted access (LAA) technology has been proposed as a promising solution to increase the network capability by extending the frequency bands for long term evolution networks. The performance evaluation of the LAA systems has been extensively studied in recent years. However, most existing works did not consider the fact that Wi-Fi stations and LAA equipments are typically not synchronized in such a heterogeneous network. They are not aligned in time domain because of different time-slot durations, channel access back off, and contention window sizes. Therefore, in this paper, we investigate the throughput performance of the LAA and Wi-Fi coexisting networks with asynchronous channel access. To deal with the asynchronism, we first introduce the concept of the heterogeneous network superframe based on the fact that the timing relation between LAA and Wi-Fi systems will be restored to a fixed pattern after a busy slot. Thereafter, we model the LAA and Wi-Fi channel access behaviors in superframes as 2-D Markov chains, respectively. Based on the Markov chains and the structure of the superframe, we analyze the throughput performance by fully considering the asynchronism of the heterogeneous channel access. The accuracy of our theoretical analysis is validated by numerical results. Meanwhile, we have also investigated the effects of the number of LAA equipments, Wi-Fi stations, and the maximum contention window size upon the system throughput.

2.4 GHz Class- $\text{F}^{-1}$ GaN Doherty Amplifier With Efficiency Enhancement Technique

An enhancement in the efficiency of an inverse Class F (Class $\text{F}^{-1})$ Doherty power amplifier (DPA) using a proposed triple-level supply modulator (SM) is presented. A three-level SM provides a lower supply voltage at a low input voltage, while providing the maximum level beyond the power back off. By adjusting the supply voltage in terms of the magnitude of the input signal, the efficiency of the main amplifier of the DPA over a wide input range is extended. For verification, a 2.4-GHz GaN Class $\text{F}^{-1}$ DPA was designed and fabricated. Using a 10 MHz 8.6 dB peak-to-average power ratio signal, at an average output power of 34.1 dBm, the fabricated Class $\text{F}^{-1}$ DPA achieves an efficiency level of 49%, which is 7.1% higher than that of a conventional amplifier. Under this condition, the measured adjacent channel leakage ratio (ACLR) is below −30 dBc.

A Class-G Voltage-Mode Doherty Power Amplifier

This paper presents the combination of two back-off efficiency enhancement techniques, the voltage-mode Doherty and the class-G switched-capacitor power amplifier (PA), to achieve efficiency peaking at both 6 and 12 dB back off without introducing the mode-switching glitches present in previous architectures. The proposed technique enables transmission of high peak-to-average-power ratio (PAPR) signals with high efficiency while maintaining excellent linearity. The PA is fabricated in 45-nm CMOS SOI with integrated balun for power combining and matching. At 3.5 GHz a saturated output power of 25.3 dBm is measured with 30.4%/25.3%/17.4% power added efficiency (PAE) at 0/6/12 dB back off. With memoryless, non-adaptive linearization, the PA achieves 19.2% PAE with −35.8 dB error vector magnitude (EVM) while transmitting a 40 MHz 256-QAM 10.1 dB PAPR 802.11ac modulation. Significant efficiency improvement compared to class-B and EVM better than −34 dB is maintained over more than 1 GHz bandwidth.

Design Approach for Implementation of Class-J Broadband Power Amplifiers Using Synthesized Band-Pass and Low-Pass Matching Topology

A new synthesis method for the design of broadband impedance matching network has been introduced to match the transistor input. The proposed matching network would be a realistic alternative to those that are frequently designed in low-pass structure. Easy-to-use design equations are given for this filter-based matching network. The required impedance of the stubs and the connecting lines can be directly calculated from the equations. This synthesis method simplifies the implementation of the network in the distributed form as compared with the LC low-pass matching network where equivalences are necessarily required in the rough conversion from lumped-to-distributed elements. The high-efficiency mode of operation is guaranteed by the constructed output low-pass matching network, since the LC low-pass network can provide the prescribed load terminations at fundamental frequencies and at harmonics. A commercially available 10-W GaN HEMT device (CGH40010) was used in this investigation. The proposed broadband power amplifier exhibits band-pass Chebyshev response in S-parameter measurements, and yields good gain flatness (±0.5 dB) and input return loss (>13 dB). Power-added efficiency of 58%-72% has been measured in large-signal measurements. After digital predistortion, the measured adjacent channel leakage power ratio is below -50 dBc at ±5- and ±10-MHz offset, when driven by 5- and 10-MHz WCDMA signals at 7-dB power back off.

Sexy yellow frogs and hot red snow

Frog sex gets colorful For some species of frogs, sex gets pretty chaotic. The amphibians gather in large groups near bodies of water—a preferred egg-laying spot—and the males go into a frenzy, trying to grab onto any female they can. The resulting sexual mayhem can lead to cases of mistaken identity. “There are a lot of reports of frogs grabbing onto inanimate objects,” says Rayna C. Bell of the Smithsonian Institution’s National Museum of Natural History. Bell and two Australian colleagues now think these species have evolved a way to cut down on carnal confusion. The males of many species that mate via these amphibian orgies tend to change color during the breeding season to possibly differentiate themselves from females (J. Evol. Biol. 2017, DOI: 10.1111/jeb.13170 ). These bright colors may serve as a way for the male frogs to tell others, “Back off” or “Don’t grab onto me,” Bell

Back off! The effect of emotion on backward step initiation

The distance regulation (DR) hypothesis states that actors are inclined to increase their distance from an unpleasant stimulus. The current study investigated the relation between emotion and its effect on the control of backward step initiation, which constitutes an avoidance-like behavior. Participants stepped backward on a force plate in response to neutral, high-arousing pleasant and high-arousing unpleasant visual emotional stimuli. Gait initiation parameters and the results of an exploratory analysis of postural sway were compared across the emotion categories using significance testing and Bayesian statistics. Evidence was found that gait initiation parameters were largely unaffected by emotional conditions. In contrast, the exploratory analysis of postural immobility showed a significant effect: highly arousing stimuli (pleasant and unpleasant) resulted in more postural sway immediately preceding gait initiation compared to neutral stimuli. This suggests that arousal, rather than valence, affects pre-step sway. These results contradict the DR hypothesis, since avoidance gait-initiation in response to unpleasant stimuli was no different compared to pleasant stimuli.

Gender role asymmetry and stock market participation – evidence from four European household surveys

ABSTRACTThis study investigates the importance of social norms for shaping women's and men's decision to participate in the stock market, aiming to disentangle the different channels playing a role in this decision. Gender role asymmetry is indicated by the country's rank in the gender equality index of the World Economic Forum. Using data from four national household surveys, we find that in Italy – the country with highly asymmetric gender role prescriptions – women's risk-taking behavior responds to this non-supportive environment. Consistent with the theory of social identity, Italian women refrain from stock market participation more than their self-reported risk tolerance levels would suggest. In contrast, in the three countries with a lower asymmetry in gender role prescriptions, no exaggerated female backing off from investing in stocks is observable. The result is robust to separately analyzing sub-samples of singles and couples. However, women who self-select into stock market participation invest the same portfolio share in stocks as do their male peers – independent of the society's degree of gender role divergence.

A High Slew-Rate Adaptive Biasing Hybrid Envelope Tracking Supply Modulator for LTE Applications

A linear-switch mode hybrid envelope tracking (ET) supply modulator utilizing adaptive biasing and gain enhanced current mirror operational transconductance amplifier (OTA) with class AB output stage in parallel with a switching regulator is presented. In comparison to a conventional OTA design with similar quiescent current consumption, proposed approach improves positive and negative slew rate from 50 to 93.4 V/ $\mu \text{s}$ and −87 to −152.5 V/ $\mu \text{s}$ , respectively, dc gain from 45 to 67 dB while consuming same amount of quiescent current. The proposed hybrid supply modulator achieves 83% peak efficiency, power-added efficiency (PAE) of 42.3% at 26.2 dBm for a 10-MHz 7.24-dB peak-to-average power ratio (PAPR) long-term evolution (LTE) signal and improves PAE by 8% at 6 dB back off from 26.2-dBm power amplifier (PA) output power with respect to fixed supply. With a 10-MHz 7.24-dB PAPR quadrature-phase shift keying LTE signal the ET PA system achieves adjacent channel leakage ratio (ACLR) of −37.7 dBc and error vector magnitude (EVM) of 4.5% at 26.2-dBm PA output power, while with a 10-MHz 8.15-dB PAPR 64QAM LTE signal the ET PA system achieves ACLR of −35.6 dBc and EVM of 6% at 26-dBm PA output power without digital predistortion. The proposed supply modulator core circuit occupies 1.1-mm2 die area, and is fabricated in a 0.18- $\mu \text{m}$ CMOS technology.

A Bayes Interpretation of Stacking for M-Complete and M-Open Settings

In M-open problems where no true model can be conceptualized, it is common to back off from modeling and merely seek good prediction. Even in M-complete problems, taking a predictive approach can be very useful. Stacking is a model averaging procedure that gives a composite predictor by combining individual predictors from a list of models using weights that optimize a cross-validation criterion. We show that the stacking weights also asymptotically minimize a posterior expected loss. Hence we formally provide a Bayesian justification for cross-validation. Often the weights are constrained to be positive and sum to one. For greater generality, we omit the positivity constraint and relax the ‘sum to one’ constraint. A key question is ‘What predictors should be in the average?’ We first verify that the stacking error depends only on the span of the models. Then we propose using bootstrap samples from the data to generate empirical basis elements that can be used to form models. We use this in two computed examples to give stacking predictors that are (i) data driven, (ii) optimal with respect to the number of component predictors, and (iii) optimal with respect to the weight each predictor gets.

Judgment and Agency

<i>Judgment and Agency</i>

A 28-GHz SiGe BiCMOS PA With 32% Efficiency and 23-dBm Output Power

In this paper, we present a two-stage, four-way combined power amplifier (PA) operating in the 27–31-GHz frequency range in 180-nm SiGe BiCMOS technology. The output network of the PA employs spiral transformers and a microstrip T-combiner to realize low-loss two-way series, two-way parallel power combining. With the help of a lumped-element transformer model, we present a co-optimization technique for the transformer and the adjoining matching components to minimize the power loss of the full output network. The design methodology is applicable for realizing an arbitrary impedance at the device plane with a K-way series, M-way parallel combiner. The efficacy of this technique is demonstrated by the realization of a PA, which has 27.6-dB gain, 23.2-dBm, 1-dB compressed output power, 32.7% power-added efficiency (PAE) at 1-dB compression, and 15% PAE at 6-dB back off. Linearity measurements show less than 4° amplitude-modulation to phase-modulation distortion below 3-dB back off and less than −32-dBc intermodulation product at 6-dB back off.