Greenhouse cultivation technology has greatly contributed to the development of agriculture in Malaysia. Understanding how to monitor the greenhouse environment with high efficiency and low power consumption is particularly important. In this research, a wireless sensor network for agricultural greenhouses based on the improved Zigbee protocol is designed. Its hardware consists of various sensors and Zigbee nodes commonly used in agricultural greenhouses. On the basis of this hardware, this research designed the network topology of WMN (Wireless mesh network) by comparing the advantages and disadvantages of various topologies, and combined with this structure, proposed an improved ZigBee routing protocol EMP-ZBR to solve the question regarding energy loss and the network congestion of wireless networks. After testing EMP-ZBR and traditional Zigbee routing protocols, the improved EMP-ZBR protocol is superior to traditional Zigbee routing in terms of the end-to-end average delay, packet delivery rate, routing control overhead and routing discovery frequency, which were optimized about 1.1%, 15.2%, 15.2%, 8.1 ms in different mobile pause times, and 9.8%, 19.3%, 15.7% and 121 ms in different packet sending rates. The agreement proves that EMP-ZBR can more effectively alleviate the impact of congestion and improve the overall performance of the data monitoring system for agricultural greenhouses.

Wireless communication systems have undergone significant development in recent years, particularly with the transition from fourth generation (4G) to fifth generation (5G). As the number of wireless devices and mobile data usage increase, there is a growing need for enhancements and upgrades to the current wireless communication systems. CMOS transceivers are increasingly being explored to meet the requirements of the latest wireless communication protocols and applications while achieving the goal of system-on-chip (SoC). The radio frequency power amplifier (RFPA) in a CMOS transmitter plays a crucial role in amplifying RF signals and transmitting them from the antenna. This state-of-the-art review paper presents a concise discussion of the performance metrics that are important for designing a CMOS PA, followed by an overview of the trending research on CMOS PA techniques that focuses on efficiency, linearity, and bandwidth enhancement.

In recent years, the development of healthcare monitoring devices requires high performance and compact in-body sensor antennas. A normal-mode helical antenna (NMHA) is one of the most suitable candidates that meets the criteria, especially with the ability to achieve high efficiency when the antenna structure is in self-resonant mode. It was reported that when the antenna was placed in a human body, the antenna efficiency was decreased due to the increase of its input resistance (R_in). However, the reason for R_in increase was not clarified. In this paper, the increase of R_in is ensured through experiments and the physical reasons are validated through electromagnetic simulations. In the simulation, the R_in is calculated by placing the NMHA inside a human’s stomach, skin and fat. The dependency of R_in to conductivity (σ) is significant. Through current distribution calculation, it is verified that the reason of the increase in R_in is due to the decrease of antenna current. The effects of R_in to bandwidth (BW) and electrical field are also numerically clarified. Furthermore, by using the fabricated human body phantom, the measured R_in and bandwidth are also obtained. From the good agreement between the measured and simulated results, the condition of R_in increment is clarified.

This Brief reports a Class-C mode-switching single-ended-complementary (MS-SEC) VCO for wideband operation. Unlike the existing wideband VCOs that utilize NMOS-only -gm transistors operating in the Class-B mode to maximize the oscillation amplitude, our MS-SEC VCO combines the advantages of class-C mode, which delivers a tall current pulse, together with current-reuse to maximize the current efficiency while lowering the phase noise (PN). The -gm transistors are preserved within the saturation region to avoid the inherent trade-off between PN and power consumption for a wideband VCO, as well as the reliability concerns. The VCO prototyped in 130-nm CMOS occupies a die area of 0.33 mm2 and consumes 5.1-to-7.3 mW at 1.2 V, while covering 2.4-to-5 GHz and meeting the stringent PN specification of the GSM standard with no SAW filter. The results correspond to a Figure-of-Merit (FoM) of >190 dBc/Hz throughout the tuning range.

The research on high-efficient non-radiant wireless power transmission (WPT) system using high-quality factor resonant coupled coils has become remarkable for powering various portable household devices, biomedical implants, and electrical vehicles since last decade. Therefore, practical WPT must be able to support complicated coil configurations and keep following magnetic resonant conditions with maximum power transfer capability during coupling distance variation. In this paper, an adaptive two-side impedance matching technique using self-tuned L-matching circuits at both the transmitting and receiving sides is proposed for maximizing transmission efficiency in resonant coupled WPT system. The tuning value of inductance and capacitance for matching networks are derived based on the Q-based design principle, and extracted impedance ratios and S-parameters. The feasibility of the theoretical model is testified against simulation and measured data. The developed model shows that using two-side matching technique maximizes transmission efficiency over 80% for a range of 15–35 cm. The proposed technique also successfully retains the resonant frequency and is much more potential to provide maximum efficiency for the resonant coupled WPT system.

Radio frequency energy harvesting (RFEH) is one form of renewable energy harvesting currently seeing widespread popularity because many wireless electronic devices can coordinate their communications via RFEH, especially in CMOS technology. For RFEH, the sensitivity of detecting low-power ambient RF signals is the utmost priority. The voltage boosting mechanisms at the input of the RFEH are typically applied to enhance its sensitivity. However, the bandwidth in which its sensitivity is maintained is very poor. This work implements a tunable voltage boosting (TVB) mechanism fully on-chip in a 3-stage cross-coupled differential drive rectifier (CCDD). The TVB is designed with an interleaved transformer architecture where the primary winding is implemented to the rectifier, while the secondary winding is connected to a MOSFET switch that tunes the inductance of the network. The TVB enables the sensitivity of the rectifier to be maintained at 1V DC output voltage with a minimum deviation of −2 dBm across a wide bandwidth of 3 to 6 GHz of 5G New Radio frequency (5GNR) bands. A DC output voltage of 1 V and a peak PCE of 83% at 3 GHz for −23 dBm input power are achieved. A PCE of more than 50% can be maintained at the sensitivity point of 1 V with the aid of TVB. The proposed CCDD-TVB mechanism enables the CMOS RFEH to be operated for wideband applications with optimum sensitivity, DC output voltage, and efficiency.