Low-cost Wireless Systems Research Articles

An OCARI-Based Wireless Sensor Network for Heat Measurements during Outdoor Fire Experiments.

This study presents a new wireless measurement system for outdoor fire experiments based on an OCARI wireless sensor network (WSN). The open-source radio communication OCARI stack (‘Open Communication Protocol for Ad Hoc Reliable Industrial Instrumentation’) allows to overcome the limitations of the previous wireless solutions for fire measurements, especially those based on proprietary systems, such as Zigbee, wherein users cannot control energy consumption and timestamping. This paper presents the design of an Atmel/ARM-based platform compatible with the wireless OCARI stack, adapted to record and communicate data from heat transducers—namely, a K-type thermocouple and heat fluxmeter. A 5-node WSN using heat sensors faces a 10 m natural fire of excelsior (pine wood) in outdoor conditions. Measurements from the OCARI-WSN were compared with the same measurements simultaneously recorded on a datalogger, a standard wired solution in fire science. Thus, six fire experiments were performed for different fuel loads, and the incident heat radiation varies with the fire size under variable wind conditions. The technological breakdown of timestamping identified in previous low-energy consumption and low-cost wireless systems is overcome by the present solution.

Terahertz Terabit Wireless Communication

Recently, terahertz (THz) technology has attracted a great deal of interest from academia and industry. This is due to a number of interesting features of THz waves, including the tens and hundreds of gigahertz bandwidths available, and the fact that this frequency band poses only a minor health threat. Also, as millimeter-wave communication systems mature, the focus of research is, naturally, moving to the THz range. According to Shannon theory, the broad bandwidth of the THz frequency bands can be used for terabit-per-second (Tb/s) wireless indoor communication systems (see Versus Terahertz). This enables several new applications, such as cordless phones with 360° auto stereoscopic displays, optic-fiber replacement, and wireless Tb/s file transferring. All of these applications provide higher quality and a better user experience. Although THz technology could satisfy the demand for an extremely high data rate, a number of technical challenges need to be overcome or better understood before its development. This article provides an overview the state-of the-art in THz wireless communication and it is also a tutorial for an emerging application in Terabit radio systems. The objective is to construct robust, low-cost wireless systems for THz terabit communications.

Frequency-Domain Analysis of Super-Regenerative Amplifiers

Since its invention in 1922, the super-regenerative amplifier (SRA) has been used in a variety of short-range, low-power, and/or low-cost wireless systems due to its simple implementation and excellent performance for a given power budget. Growing demand for ultralow-power receivers for short-range radios has recently reawakened an interest in the theory and design of SRAs. Building on recent work and using reasonable assumptions and approximations, we present a frequency-domain model for analyzing SRAs. We then use these models to predict the response of an SRA to arbitrary deterministic and stochastic signals including sinusoids, pulsed-sinusoids, and additive white Gaussian noise. Using the results, we present formulas for calculating the sensitivity and selectivity of SRAs. We also introduce the concept of a trigger-time that is particularly useful for accurately determining the optimal threshold in on-off keying (OOK) receivers and helps avoid the problems introduced by nonlinearity in SRAs. Finally, we present a prototype OOK SRA that achieves a sensitivity of -90 dBm at a bit rate of 300 kbps (BER of 10-3) while consuming 500 ?W, and show that its measured sensitivity matches theory within 1 dB.

A dual-gate FET subharmonic injection-locked self-oscillating active integrated antenna for RF transmission

A planar subharmonic injection-locked GaAs dual-gate MESFET (DGMESFET) self-oscillating active integrated antenna (AIA) is presented for RF transmission. The oscillation is obtained with one gate of the DGMESFET at 2.052 GHz, and the stabilization of the oscillation is achieved by injecting a small subharmonic low-noise signal into the other gate of the DGMESFET. Phase noise was measured to be -98 dBc/Hz at the 10 KHz offset. The structure was shown to have the potential in performing triple functions of radiation, low noise oscillation and mixing (or modulation), a capability required for low cost wireless systems such as RFID tags and indoor positioning systems.

Linear and nonlinear characteristics of the silicon CMOS monolithic 50-Ω microwave and RF control element

Radio-frequency (RF) control elements using silicon CMOS technology are investigated as an alternative to traditional PIN diode and GaAs MESFET control devices. Silicon CMOS RF control elements are attractive because of their potential in all-silicon monolithic CMOS solutions for completely integrated baseband and RF functions in low-cost wireless systems. Results of the study show that silicon CMOS switches can be designed to rival the insertion loss and isolation of gallium arsenide switches at low frequencies. Data are presented that show less than 1 dB insertion loss and isolation of greater than 50 dB at low frequencies for a variety of silicon CMOS fabrication technologies. A model for a distortion intercept point in MOS switches is presented and validated with experimental measurements.