The development of wake-up receivers (WuR) has recently received a lot of interest from both academia and industry researchers, primarily because of their major impact on the improvement of the performance of wireless sensor networks (WSNs). In this paper, we present the development of three different radiofrequency envelope detection (RFED) based WuRs operating at the 868 MHz industrial, scientific and medical (ISM) band. These circuits can find application in densely populated WSNs, which are fundamental components of Internet-of-Things (IoT) or Internet-of-Everything (IoE) applications. The aim of this work is to provide circuits with high integrability and a low cost-per-node, so as to facilitate the implementation of sensor nodes in low-cost IoT applications. In order to demonstrate the feasibility of implementing a WuR with commercially available off-chip components, the design of an RFED WuR in a PCB mount is presented. The circuit is validated in a real scenario by testing the WuR in a system with a pattern recognizer (AS3933), an MCU (MSP430G2553 from TI), a transceiver (CC1101 from TI) and a T/R switch (ADG918). The WuR has no active components and features a sensitivity of about −50 dBm, with a total size of 22.5 × 51.8 mm². To facilitate the integration of the WuR in compact systems and low-cost applications, two designs in a commercial UMC 65 nm CMOS process are also explored. Firstly, an RFED WuR with integrated transformer providing a passive voltage gain of 18 dB is demonstrated. The circuit achieves a sensitivity as low as −62 dBm and a power consumption of only 528 nW, with a total area of 634 × 391 μm². Secondly, so as to reduce the area of the circuit, a design of a tuned-RF WuR with integrated current-reuse active inductor is presented. In this case, the WuR features a sensitivity of −55 dBm with a power consumption of 43.5 μW and a total area of 272 × 464 μm², obtaining a significant area reduction at the expense of higher power consumption. The alternatives presented show a very low die footprint with a performance in line with most of the state-of-the-art contributions, making the topologies attractive in scenarios where high integrability and low cost-per-node are necessary.

This article presents the design of a low-power low noise amplifier (LNA) implemented in 45 nm silicon-on-insulator (SOI) technology using the ${\mathrm{g}}_m$/${\mathrm{I}}_D$ methodology. The Ka-band LNA achieves a very low power consumption of only 1.98 mW andis the first time the ${\mathrm{g}}_m$/${\mathrm{I}}_D$ approach is applied at such a high frequency. The circuit is suitable for Ka-band applications with a central frequency of 28 GHz, as the circuit is intended to operate in the n257 frequency band defined by the 3GPP 5G new radio (NR) specification. The proposed cascode LNA uses the ${\mathrm{g}}_m$/${\mathrm{I}}_D$ methodology in an RF/MW scenario to exploit the advantages of moderate inversion region operation. The circuit occupies a total area of 1.23 mm² excluding pads and draws 1.98 mW from a DC supply of 0.9 V. Post-layout simulation results reveal a total gain of 11.4 dB, a noise figure (NF) of 3.8 dB, and an input return loss (IRL) better than 12 dB. Compared to conventional circuits, this design obtains a remarkable figure of merit (FoM) as the LNA reports a gain and NF in line with other approaches with very low power consumption.

Wireless sensor network (WSN) applications are under extensive research and development due to the need to interconnect devices with each other. To reduce latency while keeping very low power consumption, the implementation of a wake-up receiver (WuR) is of particular interest. In WuR implementations, meeting high performance metrics is a design challenge, and the obtention of high-sensitivity, high data rate, low-power-consumption WuRs is not a straightforward procedure. The focus of our proposals is centered on power consumption and area reduction to provide high integrability and maintain a low cost-per-node, while we simultaneously improve circuit sensitivity. Firstly, we present a two-stage design based on a feedback technique and improve the area use, power consumption and sensitivity of the circuit by adding a current-reuse approach. The first solution is composed of a feedback amplifier, two op-amps plus a low-pass filter. The circuit achieves a sensitivity of –63.2 dBm with a power consumption of 6.77 µA and an area as low as 398 × 266 µm². With the current-reuse feedback amplifier, the power consumption is halved in the second circuit (resulting in 3.63 µA), and the resulting circuit area is as low as 262 × 262 µm². Thanks to the nature of the circuit, the sensitivity is improved to –75 dBm. This latter proposal is particularly suitable in applications where a fully integrated WuR is desired, providing a reasonable sensitivity with a low power consumption and a very low die footprint, therefore facilitating integration with other components of the WSN node. A thorough discussion of the most relevant state-of-the-art solutions is presented, too, and the two developed solutions are compared to the most relevant contributions available in the literature.

A 1.4-dB Noise Figure (NF) four-stage K-band Monolithic Microwave Integrated Circuit (MMIC) Low-Noise Amplifier (LNA) in UMS 100 nm GaAs pHEMT technology is presented. The proposed circuit is designed to cover the 5G New Release n258 frequency band (24.25–27.58 GHz). Momentum EM post-layout simulations reveal the circuit achieves a minimum NF of 1.3 dB, a maximum gain of 34 dB, |S₁₁| better than –10 dB from 23 GHz to 29 GHz, a P_1dB of –18 dBm and an OIP3 of 24.5 dBm. The LNA draws a total current of 59.1 mA from a 2 V DC supply and results in a chip size of 3300 × 1800 µm² including pads. We present a design methodology focused on the selection of the active device size and DC bias conditions to obtain the lowest NF when source degeneration is applied. The design procedure ensures a minimum NF design by selecting a device which facilitates a simple input matching network implementation and obtains a reasonable input return loss thanks to the application of source degeneration. With this approach the input matching network is implemented with a shunt stub and a transmission line, therefore minimizing the contribution to the NF achieved by the first stage. Comparisons with similar works demonstrate the developed circuit is very competitive with most of the state-of-the-art solutions.

The implementation of a 0.38 V K-band low-power fully differential low-noise amplifier (LNA) in a 45 nm silicon-on-insulator (SOI) process is presented. The proposed architecture employs a two-stage approach with transformer-based interstage matching networks to minimize circuit area. The proposed LNA covers the frequency range from 20.3 to 24.1 GHz, it achieves a noise figure (NF) as low as 2.2 dB, and a gain of 12.9 dB, with a power consumption of 11.7 mW from a 0.38 V DC supply in a very compact area (0.15 mm²) excluding pads. Non-linearity simulations show the proposed circuit achieves a P_o1dB of −7.3 dBm, and an OIP3 (Output Third Order Intercept) of 7 dBm. The transformers allow improved area use since they are simultaneously used as matching networks, RF chokes to bias the active devices, baluns at the input and output terminals to convert the single-ended signal into differential mode, and vice versa, and facilitates the interconnection with the upcoming stages. We used a state-of-the-art tool that generates the desired inductances to perform impedance matching for a given frequency and coupling factor value. A comparison with similar works proves the proposed LNA achieves a very low NF and the lowest power consumption reported in a differential circuit.

In this paper, a wide-band noise-canceling (NC) current conveyor (CC)-based CMOS low-noise amplifier (LNA) is presented. The circuit employs a CC-based approach to obtain wide-band input matching without the need for bulky inductances, allowing broadband performance with a very small area used. The NC technique is applied by subtracting the input transistor’s noise contribution to the output and achieves a noise figure (NF) reduction from 4.8 dB to 3.2 dB. The NC LNA is implemented in a UMC 65-nm CMOS process and occupies an area of only 160 × 80 μm². It achieves a stable frequency response from 0 to 6.2 GHz, a maximum gain of 15.3 dB, an input return loss (S11) < −10 dB, and a remarkable IIP3 of 7.6 dBm, while consuming 18.6 mW from a ±1.2 V DC supply. Comparisons with similar works prove the effectiveness of this new implementation, showing that the circuit obtains a noteworthy performance trade-off.