A quadrature oscillator based on two RC oscillators with capacitive coupling is proposed and analyzed. The capacitive coupling has the advantages of being noiseless and not increasing the power dissipation. Simulation results show that the oscillation frequency increases proportionally to the coupling capacitances, which is the opposite of what happens in capacitive coupled LC oscillators. Measurements on a 130 nm CMOS circuit prototype validate the theory of the coupling mechanism. The phase-noise is −115 dBc/Hz @ 10 MHz offset, and the FoM is −155.3 dBc/Hz, which is comparable to the best state-of-the art RC oscillators, yet the dissipated power is about four times less.

A LoRaWAN application architecture comprises three functional components: (i) nodes, which convert and wirelessly transmit data as LoRaWAN messages; (ii) gateways, which receive and forward these transmissions; and (iii) network servers, which process the received data for application delivery. The nodes convert data into LoRaWAN messages and transmit them wirelessly with the hope that one or more LoRaWAN gateway will receive the messages successfully. Then, the gateways pass on the received messages to a distant network server, where various processing steps occur before the messages are forwarded to the end application. If none of the gateways can receive the messages, then they will be lost. Although this default behaviour is suitable for some applications, there are others where ensuring messages are successfully delivered at a higher rate would be helpful. One such scenario is the application in this paper: monitoring maritime vessels and fishing equipment in offshore environments characterised by intermittent or absent shore connectivity. To address this challenge, the Custodian project was initiated to develop a maritime monitoring solution with enhanced connectivity capabilities. Two additional features are especially welcome in this scenario. The most important feature is the transmission of messages created in offshore areas to end users who are offshore, regardless of the unavailability of the ground network server. An example would be fishermen who are offshore and wish to position their fishing equipment, also offshore, based on location data transmitted from nodes via LoRaWAN, even when both entities are far away from the mainland. The second aspect concerns the potential use of gateway-to-gateway communications, through gateways on various ships, to transmit messages to the coast. This setup enables fishing gear and fishing vessels to be monitored from the coast, even in the absence of a direct connection. The functional constraints of conventional commercial gateways necessitated the conceptualisation and implementation of C-Mesh, a novel relay architecture that extends LoRaWAN functionality beyond standard protocol implementations. The C-Mesh integrates with the Custodian ecosystem, alongside C-Beacon and C-Point devices, while maintaining transparent compatibility with standard LoRaWAN infrastructure components through protocol-compliant gateway emulation. Thus, compatibility with both commercially available nodes and gateways and those already in deployment is guaranteed. We provide a comprehensive description of C-Mesh, describing its hardware architecture (communications, power, and self-monitoring abilities) and data processing ability (filtering duplicate messages, security, and encryption). Sea trials carried out on board a commercial fishing vessel in Sesimbra, Portugal, proved C-Mesh to be effective. Location messages derived from fishing gear left at sea were received by an end user aboard the fishing vessel, independently of the network server on land. Additionally, field tests demonstrated that a single C-Mesh deployment functioning as a signal repeater on a vessel with an antenna elevation of $15m$ above sea level achieved a quantifiable coverage extension of 13 km (representing a 20% increase in effective transmission range), demonstrating the capacity of C-Mesh to increase LoRaWAN’s coverage.

We present a new RC relaxation oscillator with pulse self biasing, to reduce power consumption, and with harmonic filtering and resistor feedback, to reduce phase-noise. A circuit prototype in the hundreds of MHz range, designed in a 130 nm CMOS technology has a very low phase-noise, -132.6 dBc/Hz @ 10 MHz offset, and the power consumption is only 1 mW, which leads to a figure of merit (FOM) of -159.1 dBc/Hz.

In this paper we present the analysis of two-integrator oscillator. The main characteristics of this oscillator are its wide tuning range (about a decade), the inherent quadrature outputs, and the low power requirements in comparison with other inductorless oscillators. Using the transistors nonlinearities to limit the amplitude, allows one to avoid the use of extra circuits for automatic amplitude control and, therefore, also reduces the power requirements of the oscillator. We focus the study on the quasi-linear regime where the outputs are sinusoidal. The motivation and main focus of the research is to determine the impact of the components mismatches on the frequency, amplitude- and phase-error. The equations for the amplitude mismatches and the quadrature error are derived. The theory is validated by simulation using the parameters of standard 130 nm CMOS technology. Simulations confirm the amplitude and phase error equations, and show that the quadrature error can be reduced with no impact on the phase noise. The amplitude and quadrature errors may be reduced increasing the transconductance amplifiers gains. The amplitude mismatch is dependent on the ratio of the transconductances and capacitances mismatches. Therefore, with an independent adjustment of the transconductances, the amplitude mismatch can be eliminated even with a mismatch in the capacitances.

The big proliferation of mobile communication systems has caused an increased concern about the interaction between the human body and the antennas of mobile handsets. In order to study the problem, a multiband antenna was designed, fabricated and measured to operate over two frequency sub bands 900 and 1800 MHz. After that, we simulated the same antenna, but now, in the presence of a human head model to analyze the head's influence. First, the influence of the human head on the radiation efficiency of the antenna has been investigated as a function of the distance between the head and the antenna and with the inclination of the antenna. Furthermore, the relative amount of the electromagnetic power absorbed in the head has been obtained.