Compact Wireless Sensor Nodes Research Articles

Wearable Electromyography Classification of Epileptic Seizures: A Feasibility Study.

Accurate diagnosis and classification of epileptic seizures can greatly support patient treatments. As many epileptic seizures are convulsive and have a motor component, the analysis of muscle activity can provide valuable information for seizure classification. Therefore, this paper present a feasibility study conducted on healthy volunteers, focusing on tracking epileptic seizures movements using surface electromyography signals (sEMG) measured on human limb muscles. For the experimental studies, first, compact wireless sensor nodes were developed for real-time measurement of sEMG on the gastrocnemius, flexor carpi ulnaris, biceps brachii, and quadriceps muscles on the right side and the left side. For the classification of the seizure, a machine learning model has been elaborated. The 16 common sEMG time-domain features were first extracted and examined with respect to discrimination and redundancy. This allowed the features to be classified into irrelevant features, important features, and redundant features. Redundant features were examined with the Big-O notation method and with the average execution time method to select the feature that leads to lower complexity and reduced processing time. The finally selected six features were explored using different machine learning classifiers to compare the resulting classification accuracy. The results show that the artificial neural network (ANN) model with the six features: IEMG, WAMP, MYOP, SE, SKEW, and WL, had the highest classification accuracy (99.95%). A further study confirms that all the chosen eight sensors are necessary to reach this high classification accuracy.

Wearable and Compact Wireless Sensor Nodes for Measuring the Temperature of the Base of a Calf's Tail

Wearable and Compact Wireless Sensor Nodes for Measuring the Temperature of the Base of a Calf's Tail

Development of Novel 3-D Cube Antennas for Compact Wireless Sensor Nodes

3-D antennas for narrow band, wireless sensor node applications are described herein. The antennas were designed on the surface of a cube which makes available the cube interior for sensor electronics placement. The layout of each antenna consists of a dipole fabricated on two sides of the cube and connected to a balanced-to-unbalanced line transition on the third side. The base of the cube serves as a ground plane for the microstrip feed line. The first cube antenna was designed for an operating frequency of 2.4 GHz and its 10 dB return loss bandwidth is 2%. Ka of the proposed design is 0.55 and its measured gain is 1.69 dBi with 78% measured radiation efficiency. The second cube antenna is similar to the first one but it was loaded with high dielectric constant superstrates. Ka of the second proposed antenna is 0.45, its measured gain is 1.25 dBi with 73% measured radiation efficiency and the bandwidth is 1.5%. The designs compare well with high efficiency, electrically small antennas that have been described in the open literature. A Wheeler Cap was used to measure the efficiency and the 3-antenna method was used for measuring the gain.

Development of Impedance-Based Miniaturized Wireless Water Ice Sensor for Future Planetary Applications

Keeping in view the future in situ space applications, to study planetary surface science, we have designed and developed an impedance-based extremely compact wireless sensor node to infer the presence of water/ice in a soil sample and reported in this paper. Although reflectometry-based soil moisture sensors are available commercially, they have slightly longer probe, needing more volume, from the payload point of view. The reported wireless impedance sensor reproduced in space-qualified form can be useful to measure the permittivity of lunar regolith and infer the presence of water ice. It works in the frequency domain with capability to sweep the frequency in a given measurement range. The sensor does not necessarily have long probe, and it needs only electrical contact with the soil surface, thus eliminating extra energy for insertion by the rover on the lunar surface, in one of its possible space applications. The sensor has been made to operate in wireless mode, which is a basic need in any space applications. The data are transmitted at 2.4 GHz to the aggregator. We have tested sand-type terrestrial soil and lunar soil simulant JSC-1A. To verify the performance of the sensor, we have also tested Milli-Q water. All these experimental results are reported in this paper. Results of Milli-Q water, whose permittivity is known, agree with those reported in the literature, verifying excellent performance of the sensor. Thus, the sensor can be very useful for space applications, where size and weight are critical issues. A wireless impedance sensor can also be quite useful for terrestrial applications, for example, in agriculture, and also in other impedance-based applications.

Low Noise 24 GHz CMOS Receiver for FMCW Based Wireless Local Positioning

This work demonstrates a fully integrated 24 GHz CMOS receiver targeted for low power and compact wireless sensor nodes utilizing FMCW radar for wireless local positioning. The receiver incorporates a highly integrated low noise amplifier, passive mixer and on-chip transformer balun for single-to-differential conversion of LO. The receiver chip has been realized in a 130 nm CMOS technology. At 24 GHz RF the measured receiver performance includes a power conversion gain of 16.5 dB, a noise figure of 5.3 dB, an input power at 1 dB compression point of -26 dBm and an IIP3 of -15 dBm. The complete receiver chip consumes 18 mW from a 1.2 V power supply with 13 mW for the LNA and 5 mW for the output IF buffer. The chip area is 0.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The realized receiver compares the best 24 GHz CMOS receiver realizations published so far.

Design and Comparison of 24 GHz Patch Antennas on Glass Substrates for Compact Wireless Sensor Nodes

Three patch antennas suitable for integration and operation in a compact 24 GHz wireless sensor node with radar and communication functions are designed, characterized, and compared. The antennas are manufactured on a low loss glass wafer using thin film (BCB/Cu) wafer level processing (WLP) technologies. This process is well suited for 3D stacking. The antennas are fed through a microstrip line underneath a ground plane coupling into the patch resonator through a slot aperture. Linear polarization (LP), dual mode (DM) operation, and circular polarization (CP) are achieved through the layout of the slot aperture and rectangular patch dimensions. Antenna gain values of ∼5.5 dBi are obtained in addition to the 10 dB impedance bandwidths of 900 MHz and 1.3 GHz as well as 500 MHz CP bandwidth with a 3 dB axial ratio for the LP, DM, and CP patch antennas, respectively.