Wake-up receivers (WuRXs) offer a potentially energy-efficient means to enable asynchronous wake-up of higher power and higher performance radios without needing frequent (often energy-expensive) synchronization. Since WuRXs are typically on for a large percentage of the time, keeping their power consumption very low is critical to minimizing the total energy draw. However, this is difficult while maintaining good sensitivity, interference resiliency, and robustness, all with application-appropriate wake-up latencies and form factors. This article reviews the main challenges facing WuRXs, outlines the most popular WuRX architectures, and details essential design techniques and tradeoffs toward enabling utility in emerging applications.
Lithium, a silver-white alkali metal, with significantly high energy density, has been exploited for making rechargeable lithium-ion batteries (LiBs). They have become one of the main energy storage solutions in modern electric cars (EVs). Cobalt, nickel, and manganese are three other key components of LiBs that power electric vehicles (EVs). Neodymium and dysprosium, two rare earth metals, are used in the permanent magnet-based motors of EVs. The operation of EVs also requires a high amount of electricity for recharging their LiBs. Thus, the CO2 emission is reduced during the operation of an EV if the recharged electricity is generated from non-carbon sources such as hydroelectricity, solar energy, and nuclear energy. LiBs in EVs have been pushed to the limit because of their limited storage capacity and charge/discharge cycles. Batteries account for a substantial portion of the size and weight of an EV and occupy the entire chassis. Thus, future LiBs must be smaller and more powerful with extended driving ranges and short charging times. The extended range and longevity of LiBs are feasible with advances in solid-state electrolytes and robust electrode materials. Attention must also be focused on the high-cost, energy, and time-demand steps of LiB manufacturing to reduce cost and turnover time. Solid strategies are required to promote the deployment of spent LiBs for power storage, solar energy, power grids, and other stationary usages. Recycling spent LiBs will alleviate the demand for virgin lithium and 2.6 × 1011 tons of lithium in seawater is a definite asset. Nonetheless, it remains unknown whether advances in battery production technology and recycling will substantially reduce the demand for lithium and other metals beyond 2050. Technical challenges in LiB manufacturing and lithium recycling must be overcome to sustain the deployment of EVs for reducing CO2 emissions. However, potential environmental problems associated with the production and operation of EVs deserve further studies while promoting their global deployment. Moreover, the combined repurposing and remanufacturing of spent LiBs also increases the environmental benefits of EVs. EVs will be equipped with more powerful computers and reliable software to monitor and optimize the operation of LiBs.
The Wireless Power Consortium (WPC) Energy Star Task Force (ESTF), comprised of engineers from major cellphone and consumer electronics manufacturers, test houses, and others, developed a proposed efficiency-test protocol for the U.S. Environmental Protection Agency (EPA), intended to rank Qi wireless power transmitters on the basis of power-transfer efficiency. Key to this test protocol is the assumption that a single, optimally designed test receiver may be used to accurately assess transmitter efficiency and enable ranking. The possibility exists that phones using different power receiver designs (e.g., different “friendly metal” profiles, different electrical designs) will interact with transmitters and report different rankings for a given transmitter, thus invalidating the proposed test protocol. Experiments to prove or disprove the assumption that a single optimized receiver can be used as a proxy to fairly compare and rank the real-world power-transfer efficiency performance of Qi wireless power transmitters were conducted. As a result of these experiments, the WPC has concluded that because of receiver–transmitter interaction, it is not possible to rank transmitters by efficiency for more than one receiver design but decreasing the transmitter’s standby power could save as much energy over a 24-h period as improving full-power efficiency by 10%.
The frequency-domain analysis method by Mirzaei et al. (2012) offers a systematic way to analyze the RF input impedance of $M$ -phase bandpass high-Q filters. The article also provides the mathematical expressions of the RF input impedance for $M$ -phase filters in both single-ended and differential realizations. However, the expression for the differential RF input impedance is off by a factor of two compared to simulations. In this article, we derive the corrected expression.
An Electrical Balance Duplexer (EBD) supports dual-band TX-RX isolation enabling FDD operation at 5–7 GHz for Wi-Fi 6/6E. A programmable network in the EBD can balance the antenna impedance ( $Z$ ANT) in the TX channel and RX channel independently. The EBD provides > 40 dB isolation in an 80 MHz channel bandwidth in the TX band (5–6 GHz), for any $Z_{\text{ANT}}(f_{\text{TX}})$ within $\text{VSWR} =2$ , and independently in the RX band (6–7 GHz) when $Q_{\text{ANT}}< 4.3$ . The EBD is designed for < 4 dB RX IL and < 3.8 dB TX IL, and it supports +29 dBm TX output.
