Showing papers on "RF power amplifier published in 2016"

Optimal Design of Wireless Power Transmission Links for Millimeter-Sized Biomedical Implants

Abstract: This paper presents a design methodology for RF power transmission to millimeter-sized implantable biomedical devices. The optimal operating frequency and coil geometries are found such that power transfer efficiency (PTE) and tissue-loss-constrained allowed power are maximized. We define receiver power reception susceptibility (Rx-PRS) and transmitter figure of merit (Tx-FoM) such that their multiplication yields the PTE. Rx-PRS and Tx-FoM define the roles of the Rx and Tx in the PTE, respectively. First, the optimal Rx coil geometry and operating frequency range are identified such that the Rx-PRS is maximized for given implant constraints. Since the Rx is very small and has lesser design freedom than the Tx, the overall operating frequency is restricted mainly by the Rx. Rx-PRS identifies such operating frequency constraint imposed by the Rx. Secondly, the Tx coil geometry is selected such that the Tx-FoM is maximized under the frequency constraint at which the Rx-PRS was saturated. This aligns the target frequency range of Tx optimization with the frequency range at which Rx performance is high, resulting in the maximum PTE. Finally, we have found that even in the frequency range at which the PTE is relatively flat, the tissue loss per unit delivered power can be significantly different for each frequency. The Rx-PRS can predict the frequency range at which the tissue loss per unit delivered power is minimized while PTE is maintained high. In this way, frequency adjustment for the PTE and tissue-loss-constrained allowed power is realized by characterizing the Rx-PRS. The design procedure was verified through full-wave electromagnetic field simulations and measurements using de-embedding method. A prototype implant, 1 mm in diameter, achieved PTE of 0.56% ( $-$ 22.5 dB) and power delivered to load (PDL) was 224 $\mu{\rm W}$ at 200 MHz with 12 mm Tx-to-Rx separation in the tissue environment.

An Efficient Broadband Reconfigurable Power Amplifier Using Active Load Modulation

Abstract: A novel power amplifier (PA) architecture, the Load Modulated Balanced PA (LMBA), is presented. The LMBA is able to modulate the impedance seen by a pair of RF power transistors in a quadrature balanced configuration, by varying the amplitude and phase of an external control signal. This enables power and efficiency to be optimized dynamically at specific power backoff levels and frequencies. Unlike the Doherty PA, the load seen by the active devices can be modulated upwards or downwards, both resistively and reactively, with minimal loss of power combination efficiency. The LMBA is presented as a potentially disruptive technique which enables any specific amplifier characteristic to be controlled dynamically over wide signal amplitude and frequency ranges.

Sensitive and Efficient RF Harvesting Supply for Batteryless Backscatter Sensor Networks

Abstract: This work presents an efficient and high-sensitivity radio frequency (RF) energy harvesting supply. The harvester consists of a single-series circuit with one double diode on a low-cost, lossy FR-4 substrate, despite the fact that losses decrease RF harvesting efficiency. The design targeted minimum reflection coefficient and maximum rectification efficiency, taking into account not only the impedance matching network, but also the rectifier microstrip trace dimensions and the load. The simulated and measured rectenna efficiency was 28.4% for $-\hbox{20-dBm}$ power input. In order to increase sensitivity, i.e., ability to harvest energy and operate at low power density, rectennas were connected in series configuration (voltage summing), forming rectenna arrays. The proposed RF harvesting system ability was tested at various input power levels, various sizes of rectenna arrays, with or without a commercial boost converter, allowing operation at RF power density as low as 0.0139 $\mu \hbox{W/cm}^{2}$ . It is emphasized that the boost converter, whenever used, was self-started, without any additional external energy. The system was tested in supplying a scatter radio sensor, showing experimentally the effect of input power density on the operational cold start duration and duty cycle of the sensor.

Symmetrical Doherty Power Amplifier With Extended Efficiency Range

Abstract: A symmetrical Doherty power amplifier (PA) with an extended efficiency range is proposed. This paper proves the existence of a class of symmetrical Doherty PAs having efficiency peaks for back-off levels larger than 6 dB. A design technique is developed that maintains the full voltage and current swings of both the main and auxiliary transistors. The concept is experimentally verified in a 1.95-GHz 25-W circuit demonstrator fabricated using identical GaN HEMT devices. An average power-added efficiency of 50% and adjacent power leakage ratio of $-{\hbox{49 dBc}}$ is obtained with 9-dB peak-to-average power-ratio 20-MHz long-term evolution test signals.

Iterative Learning Control for RF Power Amplifier Linearization

Abstract: This paper proposes a new technique to identify the parameters of a digital predistorter based on iterative learning control (ILC). ILC is a well-established control theory technique that can obtain the inverse of a system. Instead of focusing on identifying the predistorter parameters, the technique proposed here first uses an iterative learning algorithm to identify the optimal power amplifier (PA) input signal that drives the PA to the desired linear output response. Once the optimal PA input signal is identified, the parameters of the predistorter are estimated using standard modeling approaches, e.g., least squares. To this end, in this paper, we present a complete derivation of an ILC scheme suitable for the linearization of PAs, which includes convergence conditions and the derivation of two learning algorithms. The proposed ILC scheme and parameter identification technique were demonstrated experimentally and compared with the indirect learning architecture (ILA) and direct learning architecture (DLA). The experimental results show that, even for the most difficult cases, the proposed ILC scheme can successfully linearize the PA. The experimental results also indicate that the proposed parameter identification technique is more robust to measurement noise than ILA and can provide better linearity performance when the PA nonlinearities are strong. In addition, the proposed parameter identification technique can achieve similar or better linearity performance than DLA but with a simpler identification process.

A Broadband Doherty Power Amplifier Based on Continuous-Mode Technology

Abstract: In this paper, a novel broadband Doherty power amplifier based on the continuous-mode technique (C-DPA) is proposed. The amplifier is focused on manipulating harmonic components in a Doherty power amplifier (DPA) structure to achieve improved bandwidth and efficiency. In a conventional DPA, harmonic isolation is typically required between the two transistors to prevent them from modulating each other at harmonic frequencies. However, as presented in this paper, such isolation is not actually necessary. On the contrary, by allowing the two transistors to modulate each other at harmonic frequencies with the help of a properly designed postharmonic tuning network, a series of highly efficient DPA modes can be created over a continuous frequency band, leading to a broadband C-DPA. Based on the proposed method, an example of a C-DPA working from 1.65 to 2.75 GHz was designed. According to the measured results, the designed C-DPA exhibits a 52%–66% efficiency at a −6 dB power backoff and a power utilization factor higher than 1.08 over the 1.1-GHz band. In addition, when simulated by a 7.5-dB peak-to-average power ratio 20-MHz LTE signal, the example C-DPA exhibits an efficiency of 46%–62% while maintaining an adjacent channel power ratio below −45 dBc after linearization over the full 1.1-GHz band. To the best of our knowledge, this is the first proposed C-DPA and a state-of-the-art performance for broadband DPAs.

Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing

Abstract: We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone, we are able to generate parametric amplification using three-wave mixing (3WM). The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. We compare these results directly to the four-wave mixing amplification mode, i.e., without DC-biasing. We find that the 3WM mode allows operation with the pump at lower RF power and at frequencies far from the signal. We have used this knowledge to redesign the amplifiers to utilize primarily 3WM amplification, thereby allowing for direct integration into large scale qubit and detector applications.

A New Rectenna With All-Polarization-Receiving Capability for Wireless Power Transmission

Abstract: This letter presents a new rectenna with all-polarization-receiving capability for wireless power transmission applications. By utilizing a dual linearly-polarized antenna, the incident wave of arbitrary polarization can be totally collected at its two ports. To be connected with the antenna as a rectenna, a dual-input rectifier is designed so that the RF power supplied by the two ports of the antenna can be efficiently rectified. With a proper polarization of the incident wave, the proposed rectenna exhibits a maximum efficiency of 78% under the input power density of 295.3 $~\mu\hbox{W/cm}^{2}$ . Moreover, under the same power density, the rectenna’s efficiency can always stay higher than 61% regardless of the incident wave’s polarization.

Effect of RF power on the structural, optical and gas sensing properties of RF-sputtered Al doped ZnO thin films

Abstract: The effect of Radio Frequency (RF) power on the properties of magnetron sputtered Al doped ZnO thin films and the related sensor properties are investigated. A series of 2 wt% Al doped ZnO; Zn0.98Al0.02O (AZO) thin films prepared with magnetron sputtering at different RF powers, are examined. The structural results reveal a good adhesive nature of thin films with quartz substrates as well as increasing thickness of the films with increasing RF power. Besides, the increasing RF power is found to improve the crystallinity and grain growth as confirmed by X-ray diffraction. On the other hand, the optical transmittance is significantly influenced by the RF power, where the transparency values achieved are higher than 82% for all the AZO thin films and the estimated optical band gap energy is found to decrease with RF power due to an increase in the crystallite size as well as the film thickness. In addition, the defect induced luminescence at low temperature (77 K) and room temperature (300 K) was studied through photoluminescence spectroscopy, it is found that the defect density of electronic states of the Al3+ ion increases with an increase of RF power due to the increase in the thickness of the film and the crystallite size. The gas sensing behavior of AZO films was studied for NO2 at 350 °C. The AZO film shows a good response towards NO2 gas and also a good relationship between the response and the NO2 concentration, which is modeled using an empirical formula. The sensing mechanism of NO2 is discussed.

Design of a Post-Matching Asymmetric Doherty Power Amplifier for Broadband Applications

Abstract: In this letter, the design of a broadband asymmetric Doherty power amplifier (ADPA) with an 800 MHz (41% fractional) bandwidth is presented. The post-matching structure and low-order impedance transformation networks (ITN) are employed to achieve the broadband performance. Meanwhile, different drain biases on the main and peaking devices are used to run the asymmetric operation. The proposed ADPA shows high-efficiency performance at 8–9 dB output power back-off (OBO) throughout the whole 800 MHz band. The ADPA has been designed and implemented using commercial GaN HEMTs to validate the OBO and broadband characteristics. Maximum output power ranges from 43.7 to 45.2 dBm, 50.4%-56.2% efficiencies at 8–9 dB OBO are measured from 1.55 to 2.35 GHz.

A Fully Integrated Bluetooth Low-Energy Transmitter in 28 nm CMOS With 36% System Efficiency at 3 dBm

Abstract: We propose a new transmitter architecture for ultra-low power radios in which the most energy-hungry RF circuits operate at a supply just above a threshold voltage of CMOS transistors An all-digital PLL employs a digitally controlled oscillator with switching current sources to reduce supply voltage and power without sacrificing its startup margin It also reduces 1/f noise and supply pushing, thus allowing the ADPLL, after settling, to reduce its sampling rate or shut it off entirely during a direct DCO data modulation The switching power amplifier integrates its matching network while operating in class-E/F2 to maximally enhance its efficiency at low voltage The transmitter is realized in 28 nm digital CMOS and satisfies all metal density and other manufacturing rules It consumes 36 mW/55 mW while delivering 0 dBm/3 dBm RF power in Bluetooth Low-Energy mode

Loading and Power Control for a High-Efficiency Class E PA-Driven Megahertz WPT System

Abstract: In this paper, the loading effect of a Class E power amplifier (PA) driven 6.78 megahertz (MHz) wireless power transfer (WPT) system is analyzed at both circuit and system levels. A buck converter is introduced and controlled to track an optimal equivalent load that maximizes the system efficiency under uncertainties in the relative position of coils and the final load. For power control, an additional degree of freedom is provided by adding an ultracapacitor bank. A control strategy is proposed to track the maximum efficiency and charge/discharge the ultracapacitor bank through the on/off control of the Class E PA. Thus, high system efficiency can be maintained under various uncertainties and load power demands. Finally, the theoretical analysis and the control scheme are validated in experiments. The results show that the proposed Class E PA-driven MHz WPT system can stably achieve a high efficiency under different coil distances and various constant/pulsed power profiles. The measured highest system efficiency can reach 72.1% at a load power level of 10 W.

A Doherty Power Amplifier Design Method for Improved Efficiency and Linearity

Abstract: A novel Doherty power amplifier (PA) design method enabling high efficiency and high linearity simultaneously is proposed The output combiner network is treated as a black box, and its parameters, together with the input phase delay, are solved based on given transistor characteristics and design requirements This opens for new PA solutions with nonconventional Doherty behavior The increased design space enables new tradeoffs in Doherty PA designs, including solutions with both high efficiency and high linearity simultaneously A method utilizing the new design space is developed For verification, a 20-W 214-GHz symmetrical gallium nitride high electron mobility transistors Doherty PA is fabricated and measured The PA obtains an average power added efficiency of 40% and an adjacent power leakage ratio of −41 dBc without any linearization for an 86-dB peak to average power ratio 10-MHz-long term evolution signal, at an average output power of 355 dBm

Physical Mechanism and Theoretical Foundation of Ambient RF Power Harvesting Using Zero-Bias Diodes

Abstract: Estimating the amount of harvestable ambient RF and microwave power from the omnipresent electromagnetic sources is of vital importance when designing a wireless device that makes use of ambient microwave power harvesting (AMPH) as a power source. This paper studies and looks into the underlying RF and microwave rectification mechanism at low input ambient power levels, specifically −30 dBm and below. A fundamental theory is formulated and developed, which is able to correctly predict the efficiency of a rectifier including the effects of matching network insertion losses through an easy-to-understand analytical model. The suggested model provides a direct design guideline in determining and choosing the optimal diode for a predetermined application. Based on the developed theoretical framework, the diode characteristics that have a direct impact on the microwave power conversion efficiency are discussed in detail. Three different Schottky diode rectifiers were designed on the basis of the tools described in this paper, thereby validating the proposed model and highlighting the influence of critical diode parameters on its performances. The measured results are then compared with those predicted by the proposed model and state-of-the-art microwave power rectifiers, showing a good model accuracy and also a 10% improvement in the rectifying efficiency for the low input power levels of interest.

Plasma processing device

Abstract: This invention aims to improve the way of pulse modulation by which RF power utilized in plasma processing is switched alternately between a high level and a low level depending on the duty ratio of the modulated pulse. By using the plasma processing device according to this invention, in the case, for example, when high/low pulse modulation is performed with respect to RF power for plasma generation, if a weight variable K of the weighted average in a matching unit is set to be 0.5 < K < 1, a reflected wave is generated at a constant power PRH in a RF power feed line of a plasma producing system even during a PULSE,ON period Ton, while the power PRL of the reflected wave decreases during a PULSE,OFF period Toff. By adjusting the value of the weight variable K, balance between the power of the reflected wave during the PULSE,ON period Ton and that during the PULSE,OFF period Toff can be arbitrarily controlled.

High frequency GaN HEMTs for RF MMIC applications

Abstract: We provide an overview of key challenges and technical breakthroughs that led to development of highly scaled GaN HEMT's having ft > 400 GHz and fmax > 550 GHz and the corresponding IC process. These highly scaled GaN devices have 5 times higher breakdown voltage than transistors with similar high frequency RF power gain in other semiconductor systems (Si, SiGe, InP, GaAs). We also report performance of the first generation of MMIC power amplifiers (PAs) that utilize these highly scaled devices. The power added efficiency (PAE) of 59% measured at a frequency of 32 GHz, bias of 3 V and output power of 24.3 dBm of the first generation Ka-band MMIC PAs that were built using these highly scaled GaN devices, represent a significant improvement in PAE over values reported for other semiconductor technologies at this frequency band as well as for Ka-band MMICs built in lower frequency GaN nodes. Presented data suggest that highly scaled GaN transistors are excellent candidates for MMIC PAs for next generation 28 GHz, 39 GHz, and higher frequency 5G mobile bands, because they would greatly extend battery lifetime in mobile handsets, due to their superior PAE compared to competing semiconductor technologies.

Epidermal radio frequency electronics for wireless power transfer.

Abstract: Epidermal electronic systems feature physical properties that approximate those of the skin, to enable intimate, long-lived skin interfaces for physiological measurements, human-machine interfaces and other applications that cannot be addressed by wearable hardware that is commercially available today. A primary challenge is power supply; the physical bulk, large mass and high mechanical modulus associated with conventional battery technologies can hinder efforts to achieve epidermal characteristics, and near-field power transfer schemes offer only a limited operating distance. Here we introduce an epidermal, far-field radio frequency (RF) power harvester built using a modularized collection of ultrathin antennas, rectifiers and voltage doublers. These components, separately fabricated and tested, can be integrated together via methods involving soft contact lamination. Systematic studies of the individual components and the overall performance in various dielectric environments highlight the key operational features of these systems and strategies for their optimization. The results suggest robust capabilities for battery-free RF power, with relevance to many emerging epidermal technologies.

Not Just a Phase: Outphasing Power Amplifiers

Abstract: Performing RF amplification in a way that is simultaneously linear and efficient has long been a challenge in power amplifier (PA) design. In short, single-transistor PAs can either be operated in a linear (but inefficient) current-source mode of operation or as efficient (but nonlinear) switches, but these two modes are mutually exclusive. The outphasing concept has been explored to address this tradeoff by using efficient but nonlinear elements in an architecture providing linear output power control.

A Methodology for Implementation of High-Efficiency Broadband Power Amplifiers With Second-Harmonic Manipulation

Abstract: This brief describes a methodology for designing broadband power amplifiers (PAs) based on the manipulation of second-harmonic impedance. The proposed approach starts from the inverse class-F (F−1) design specification and extends it to a family of specifications that allow achieving better than class-B performance in terms of output power and drain efficiency. It is shown that the achievable performance can be maintained over a wide frequency range reaching 57% of fractional bandwidth. As such, the proposed approach permits higher flexibility and offers relaxed matching constraints in implementing broadband high-efficiency PAs. For the experimental implementation, the proposed approach is adopted to implement a broadband PA using a 10-W gallium-nitride transistor. Peak drain efficiencies greater than 75% are measured over carrier frequencies between 500 and 900 MHz. The saturated output power levels, on the other hand, are higher than 10 W with a maximum of 13 W. Measured results are confirmed to be in good agreement with theory and simulations.

233 GHz high Power amplifier development at Northrop Grumman

Abstract: Northrop Grumman has developed a folded-waveguide vacuum electronic high power amplifier at 233 GHz. The amplifier demonstrates output power over 79 W (49 dBm) from 232.6–234.6 GHz, and greater than 50 W (47 dBm) over a 2.4 GHz instantaneous bandwidth. Saturated gain is approximately 23–24 dBm over this bandwidth, with an input drive of 26–27 dBm required for saturated output power. The device operating point is 20.95kV, 114mA for a frequency range centered at 233.6 GHz, but is capable of producing 50W at frequencies up to 237.8 GHz by varying the operating voltage. Typical instantaneous (3 dB) operating bandwidth ranges from 2.4– 3.0 GHz for a beam voltage range of 20.5–21 kV. The amplifier uses a compact permanent magnet solenoid for beam focusing and confinement, and typically achieves 95– 98% beam transmission through the folded-waveguide circuit and into the single-section depressed collector. This device has demonstrated operational duty cycles up to 50% with liquid cooling and using Northrop Grumman's Microwave Power Module compact integrated power conditioner technology. A more compact version of this power amplifier is being developed with emphasis on reducing the size of the permanent magnet solenoid.

Will Doherty continue to rule for 5G

Abstract: High data rate 5G systems are expected to operate at frequencies between 15GHz and 100GHz, and utilize large numbers of antennas in both base-stations and handsets. Representative power amplifier scenarios differ from those in commercial wireless today: there will be many more power amplifiers operating at much low power levels. Yet signal peak-to-average ratios will remain high, and efficiency will remain a critical consideration. Doherty amplifiers will be a prime contender for these applications, although they are not the only possibility. This paper reviews the emerging requirements for power amplifiers in mm-wave 5G systems, describes the status of mm-wave Doherty ICs in different device technologies, lists challenges for amplifier designs, and provides a glimpse of approaches other than Doherty amplifiers to meet the needs.

Handbook Of Rf And Microwave Power Amplifiers

Abstract: handbook of rf and microwave power amplifiers is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection hosts in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the handbook of rf and microwave power amplifiers is universally compatible with any devices to read.

CMOS Power Amplifier Integrated Circuit With Dual-Mode Supply Modulator for Mobile Terminals

Abstract: A CMOS power amplifier integrated circuit with an optimized dual-mode supply modulator is presented. The dual-mode supply modulator, based on a hybrid buck converter consisting of a wideband linear amplifier and a highly efficient switching amplifier, provides two operation modes: envelope tracking (ET) for high average output power and average power tracking (APT) for low output power. For the APT mode, the linear amplifier is switched off and the switching amplifier operates as a normal buck converter to supply DC voltage to the power amplifier according to the average output power. The optimum switch sizes of the switching amplifier were analyzed and applied for each operation mode for higher efficiency. An integrated circuit with a power amplifier and the dual-mode supply modulator was designed and fabricated using a 0.18- $\mu\mbox{m}$ CMOS process for LTE applications at a frequency of 0.78 GHz. For the 16-QAM uplink LTE signal, the measured efficiency with an ET mode is as high as 45.4%, which is 7.0% higher than that from the stand-alone power amplifier at an average output power of 24 dBm. An efficiency of 14.1% was achieved with an APT mode at an average output power of 9 dBm. This is 3.2% higher than that with the ET mode.

Wide-Range Adaptive RF-to-DC Power Converter for UHF RFIDs

Abstract: A wide-range, differential, cross-coupled rectifier is proposed with an extended dynamic range of input RF power that enables wireless powering from varying distances. The proposed architecture mitigates the reverse-leakage problem in conventional, cross-coupled rectifiers without degrading sensitivity. A prototype is designed for UHF RFID applications, and is implemented using 0.18 $\mu\text{m}$ CMOS technology. On-chip measurements demonstrate a sensitivity of −18 dBm for 1 V output over a 100 $\text{k}\Omega$ load and a peak RF-to-DC power conversion efficiency of 65%. A conventional, fully cross-coupled rectifier is fabricated alongside for comparison and the proposed rectifier shows more than 2× increase in dynamic range and a 25% boosting in output voltage than the conventional rectifier.

Flexible superconducting Nb transmission lines on thin film polyimide for quantum computing applications

Abstract: We describe progress and initial results achieved towards the goal of developing integrated multi-conductor arrays of shielded controlled-impedance flexible superconducting transmission lines with ultra-miniature cross sections and wide bandwidths (dc to >10 GHz) over meter-scale lengths. Intended primarily for use in future scaled-up quantum computing systems, such flexible thin-film niobium/polyimide ribbon cables could provide a physically compact and ultra-low thermal conductance alternative to the rapidly increasing number of discrete coaxial cables that are currently used by quantum computing experimentalists to transmit signals between the several low-temperature stages (from ~4 K down to ~20 mK) of a dilution refrigerator. We have concluded that these structures are technically feasible to fabricate, and so far they have exhibited acceptable thermo-mechanical reliability. S-parameter results are presented for individual 2-metal layer Nb microstrip structures having 50 Ω characteristic impedance; lengths ranging from 50 to 550 mm were successfully fabricated. Solderable pads at the end terminations allowed testing using conventional rf connectors. Weakly coupled open-circuit microstrip resonators provided a sensitive measure of the overall transmission line loss as a function of frequency, temperature, and power. Two common microelectronic-grade polyimide dielectrics, one conventional and the other photo-definable (PI-2611 and HD-4100, respectively) were compared. Our most striking result, not previously reported to our knowledge, was that the dielectric loss tangents of both polyimides, over frequencies from 1 to 20 GHz, are remarkably low at deep cryogenic temperatures, typically 100× smaller than corresponding room temperature values. This enables fairly long-distance (meter-scale) transmission of microwave signals without excessive attenuation, and also permits usefully high rf power levels to be transmitted without creating excessive dielectric heating. We observed loss tangents as low as 2.2 × 10−5 at 20 mK, although losses increased somewhat at very low rf power levels, similar to the well-known behavior of amorphous inorganic dielectrics such as SiO2. Our fabrication techniques could be extended to more complex structures such as multiconductor cables, embedded microstrip, 3-metal layer stripline or rectangular coax, and integrated attenuators and thermalization structures.

A 70–80-GHz SiGe Amplifier With Peak Output Power of 27.3 dBm

Abstract: This paper presents a fully integrated 16-way power-combining amplifier for 67–92-GHz applications in an advanced 90-nm silicon germanium HBT technology. The 16-way amplifier is implemented using three-stage common-emitter single-ended power amplifiers (PAs) as building blocks, and reactive $\lambda $ /4 impedance transformation networks are used for power combining. The three-stage single PA breakout has a small-signal gain of 22 dB at 74 GHz, and saturation output power ( $P_{\mathrm{ sat}}$ ) of 14.3–16.4 dBm at 68–99 GHz. The power-combining PA achieves a small-signal gain of 19.3 dB at 74 GHz, and $P_{\mathrm{ sat}}$ of 25.3–27.3 dBm at 68–88 GHz with a maximum power added efficiency of 12.4%. The 16-way amplifier occupies 6.48 mm2 (including pads) and consumes a maximum current of 2.1 A from a 1.8 V supply. To the best of our knowledge, this is the highest power silicon-based $E$ -band amplifier to date.

Supply-Scaling for Efficiency Enhancement in Distributed Power Amplifiers

Abstract: Distributed amplifiers (DAs) feature large bandwidth but relatively low gain and power efficiency. This paper presents a supply-scaling technique to improve the efficiency of a mm-wave DA while maintaining a broadband $50\Omega $ match. An analysis of interstage load modulation and the effects of shunt dc-feed inductors on distributed operation is provided. A single-ended, eight-stage DA is designed in a 90 nm SiGe BiCMOS process. The fabricated amplifier has a gain of 12 dB over a 3 dB bandwidth from 14–105 GHz. The measured peak output power is 17 dBm with a peak power-added efficiency (PAE) of 12.6% at 50 GHz and 3 dB power bandwidth greater than 70 GHz. The DA occupies an area of 2.65 mm $\times 0.57$ mm, and total dc power consumed from four scaling voltage supplies is 297 mW.

Improved Doherty Amplifier Design with Minimum Phase Delay in Output Matching Network for Wideband Application

Abstract: This letter presents an improved Doherty power amplifier (DPA) for high-efficiency and wideband operations. To achieve the impedance transformations both in the low power region and at saturation, a design approach is proposed to determine the desired minimum phase delays of the carrier and peaking output matching networks, which can simplify the load modulation network of the DPA and extend the bandwidth. For verification, a 1.6–2.2 GHz asymmetric DPA was designed and measured. The designed DPA can deliver an efficiency of 51%–55% at 10 dB back-off power over the whole band. For a 20 MHz LTE signal, an average efficiency of higher than 50% can be achieved at 36 dBm average output power with the linearity of–48 dBc after linearization across the band.

System-Level Analysis of Far-Field Radio Frequency Power Delivery for mm-Sized Sensor Nodes

Abstract: Millimeter-sized and low-cost sensor nodes can enable future applications of the Internet of Things (IoT), for which the number of sensors is projected to grow to a trillion within the next decades. RF far-field power transfer is a potential technique for wirelessly powering these sensors since it offers flexible configuration of sensor networks, beamforming capability and a large power transfer range compared to near-field approaches. However, system design for RF power transfer needs to be completely rethought to enable this new paradigm of a trillion IoT sensors. This paper, therefore, presents a comprehensive, system-level analysis strategy and a modular framework for investigating the fundamental efficiency components in an RF power transfer chain. Through this detailed analysis, it is demonstrated that the optimal frequency is primarily determined by the antenna size and the quality factors $(Q)$ of components in the matching network. Millimeter-wave frequencies are shown to be optimal for powering mm-sized sensors for practical matching component $Q$ values. An intuitive explanation of our results is also provided, along with insights for the design and practical implementation of RF power transfer systems for the IoT space.

Doherty Goes Digital: Digitally Enhanced Doherty Power Amplifiers

Abstract: Efficiency enhancement techniques for high-power amplification systems are now mature technologies, with Doherty power amplifiers (PAs) being widely used in field-deployed wireless base stations. A typical Doherty PA consists of two parallel amplifiers (a carrier amplifier, biased in class-AB, and a peaking amplifier, biased in class-C), an input analog splitter, and a nonisolated output power combiner. The operation of the Doherty PA is based on an active load modulation mechanism, which allows the carrier and peaking amplifiers to operate into optimal load-impedance trajectories that vary according to the amplitude of the input signal. This, in principle, results in increasing the average efficiency of the Doherty PA without compromising its linearity.