http://ieeexplore.ieee.org/iel5/5/31324/01456901.pdf

Microelectronic circuits

https://calhoun.nps.edu/bitstream/10945/24839/1/singlesidebandtr00elli.pdf

Single sideband transmission by envelope elimination and restoration.

Traditionally employed human-to-human and human-to-machine communication has recently been replaced by a new trend known as the Internet of things (IoT). IoT enables device-to-device communication without any human intervention, hence, offers many challenges. In this paradigm, machine’s self-sustainability due to limited energy capabilities presents a great challenge. Therefore, this paper proposed a low-cost energy harvesting device using rectenna to mitigate the problem in the areas where battery constraint issues arise. So, an energy harvester is designed, optimized, fabricated, and characterized for energy harvesting and IoT applications which simply recycles radio-frequency (RF) energy at 2.4 GHz, from nearby Wi-Fi/WLAN devices and converts them to useful dc power. The physical model comprises of antenna, filters, rectifier, and so on. A rectangular patch antenna is designed and optimized to resonate at 2.4 GHz using the well-known transmission-line model while the band-pass and low-pass filters are designed using lumped components. Schottky diode (HSMS-2820) is used for rectification. The circuit is designed and fabricated using the low-cost FR4 substrate ( ${h}$ = 16 mm and $\varepsilon _{r} = 4.6$ ) having the fabricated dimensions of 285 mm $\times \,\,90$ mm. Universal software radio peripheral and GNU Radio are employed to measure the received RF power, while similar measurements are carried out using R&S spectrum analyzer for validation. The received measured power is −64.4 dBm at the output port of the rectenna circuit. Hence, our design enables a pervasive deployment of self-operable next-generation IoT devices.

Energy Harvesting Using a Low-Cost Rectenna for Internet of Things (IoT) Applications

A scalable electrothermal large-signal AlGaN/GaN HEMTs model for both fundamental and multiharmonics is presented based on the modified Angelov model. To obtain accurate scalability of the electrothermal model, a simple empirical expression is proposed for the geometric and power-dissipation-dependent nonlinear thermal resistance $R_{{\mathrm {th}}}$ . Only one additional parameter with linear scaling rule is needed in the drain-source current ( $I_{{\mathrm {ds}}}$ ) model for a scalable large-signal multiharmonic model. The proposed model has been validated by different AlGaN/GaN HEMTs characterized by on-wafer measurements. It shows that the presented scalable model can well predict the dc $I$ – $V$ , pulsed $I$ – $V$ , scattering (S) parameters, and large-signal performance up to third harmonic. Furthermore, to further validation, a C-band power amplifier is designed. The amplifier is realized using the second-harmonic tuned approach to enhance the efficiency. Measurement results show that the GaN high power amplifier (HPA) microwave monolithic integrated circuit (MMIC) exhibits more than 40% power-added efficiency and 60-W output power ( $P_{{\mathrm {out}}}$ ) with associated gain of 25 dB in 5–6 GHz measured at 28-V drain voltage and pulse signal with 100- $\mu \text{s}$ pulsewidth and 10% duty cycle. The area of the chip is 3.2 mm $\times5.3$ mm (16.96 mm2). These results show that the proposed model will be useful for high-efficiency HPA MMIC design.

A Scalable Large-Signal Multiharmonic Model of AlGaN/GaN HEMTs and Its Application in C-Band High Power Amplifier MMIC

In this paper, we present a fast failover mechanism and a fast switchover mechanism to deal with link failure and congestion problems. In the fast failover mechanism, the controller pre-establishes multiple paths for each source-destination pair in the related OpenFlow-enabled (OF) switches. When a link becomes faulty, OF switches are able to failover the affected flows to another path. Based on the pre-established paths, in the fast switchover mechanism, the controller periodically monitors the status of each port of each OF switch. When the average transmission rate of a port consistently exceeds the rate threshold, the controller would decrease the transmission rate of the port by iteratively switching the flow with the minimum rate to another path. The emulation on Ryu controller and Mininet emulator shows the average recovery time of the fast failover mechanism is less than 40 ms, compared to hundreds of ms in the fast restoration mechanism. And, the fast switchover mechanism can reduce 47.5%-72.5% sustained time of link congestion depending on the parameter setting.

Fast failover and switchover for link failures and congestion in software defined networks

Modulation of load impedance is an effective way to maintain efficient power amplifier (PA) operation over high dynamic range modulated signals. For high efficiency, a load modulation approach can be applied to inherently efficient classes of PAs such as those with harmonic tuning: Class J, Class F, and Inverse Class F. This paper presents an analysis of harmonically tuned (HT) amplifiers operating under load modulation conditions, deriving the optimal loading trajectories for these multiple classes of operation. Because these load trajectories are complex, it is then shown—through a series of analysis, simulations, and measurements—that HT amplifiers are better suited for outphasing systems, than conventional amplifiers such as Class B. A design methodology is proposed and validated through design and measurement of a 900-MHz outphasing system, comprising of two Gallium Nitride Class J branch PAs, delivering 44.6 dBm with 75% PAE at saturation, while mantaining PAE above 60% over a 7-dB output power back-off.

/pdf/load-modulation-of-harmonically-tuned-amplifiers-and-4ucmtyurx7.pdf

Load Modulation of Harmonically Tuned Amplifiers and Application to Outphasing Systems

A reactance-compensation technique has been introduced recently for the design of wideband class-E power amplifiers (PAs). With this technique, the load resistance can be transformed to an optimal complex drain impedance in a broad frequency band. One potential problem of this technique is that an additional network is often needed to transform 50 $\Omega$ to the optimum load resistance, which is typically at a lower value. This paper proposes a method to improve the reactance compensation technique. By using the proposed method, the required low-value load resistance is up to four times the original value. This is achieved not by adding more components, but by simply changing the order and values of them. With the proposed method, the additional resistance matching network is no longer needed in many cases, or can be significantly simplified in other cases. To validate the theory, two broadband class-E amplifiers were designed using the original technique and the proposed method, respectively. The performances of the two amplifiers are compared. By using similar complexity of matching networks, the PA designed using the original method can achieve better than 70% power-added efficiency for a fractional bandwidth of 42%. The PA designed using the proposed method can achieve above 70% efficiency for a bandwidth of 51%. The proposed method can be used in the design of many other types of amplifiers.

/pdf/improved-reactance-compensation-technique-for-the-design-of-55npeuwi4j.pdf

Improved Reactance-Compensation Technique for the Design of Wideband Suboptimum Class-E Power Amplifiers

This study investigates the feasibility of ambient radio frequency (RF) energy harvesting for powering low-power electronic devices, in domestic environments. An RF spectrum survey was carried out in a variety of locations around the city of Bristol, UK between 500 MHz and 6 GHz. Locations are limited to indoor residential environments, and as a comparison an office. The measurement setup consists of an omnidirectional, broadband, discone antenna and a handheld spectrum analyser. On the basis of the measured power consumption of a number of low-power electronic devices and the analysed results, the required harvesting time to power each device is calculated. The results show that in order to harvest enough energy to power-up a small calculator (2 μW) for 1 s, an antenna array covering 1.7–2.5 GHz with effective area of 1 m2 requires on average about 10 min of harvesting.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2014.0406

Ambient RF energy harvesting trial in domestic settings

Achieving fast wireless access speeds in an already restricted bandwidth (as the frequency spectrum is a finite resource) necessitates highly spectrally efficient communications standards that combine both amplitude-modulation (AM) and phase-modulation (PM). The resulting complex modulation schemes require that the RF power amplifier (PA) be highly linear to preserve the modulation and, hence, the transmitted data (in-band linearity) and simultaneously avoid interfering with users of the rest of the spectrum (out-of-band linearity). Unfortunately, in PA design, linearity and efficiency are contradictory goals; typically, highly linear PAs demonstrate low efficiency and, hence, reduced battery life [1].

How Not to Rely on Moore's Law Alone: Low-Complexity Envelope-Tracking Amplifiers

This paper reports the design of a class-E envelope elimination and restoration (EER) based amplifier for a wideband code division multiple access handset application that attains 60% power-added efficiency at peak power output. Emphasis is placed on the envelope modulator that employs a novel split-frequency approach in order to attain an efficiency of 80% for this part of the system. In contrast to standard EER systems, the carrier is not amplitude limited, but rather predistorted to maintain both linearity and power efficiency. Performance in terms of efficiency, spectral output, and error vector magnitude is reported.

/pdf/a-60-pae-wcdma-handset-transmitter-amplifier-3r8kuxtjio.pdf

Gavin T. Watkins

Papers

Load Modulation of Harmonically Tuned Amplifiers and Application to Outphasing Systems

Improved Reactance-Compensation Technique for the Design of Wideband Suboptimum Class-E Power Amplifiers

Ambient RF energy harvesting trial in domestic settings

How Not to Rely on Moore's Law Alone: Low-Complexity Envelope-Tracking Amplifiers

A 60% PAE WCDMA Handset Transmitter Amplifier