A non-contact, non-invasive monitoring system to measure and estimate the heart and breathing rate of humans using a frequency-modulated continuous wave (FMCW) mm-wave radar at 77 GHz is presented. A novel diagnostic system is proposed which extracts heartbeat phase signals from the FMCW radar (reconstructed using Fourier series analysis) to test a three-layer artificial neural network model to predict the presence of arrhythmia in individuals. The effect of person orientation, distance of measurement and movement was analyzed with respect to a reference device based on statistical measures that include number of outliers, mean, mean squared error (MSE), mean absolute error (MAE), median absolute error (medAE), skewness, standard deviation (SD) and R-squared values. The individual oriented in front of the radar outperformed almost all other orientations for most distances with an expected d = 90 cm and d = 120 cm. Furthermore, it was found that the heart rate that was measured while walking and the breathing rate which was measured for a motionless individual generated results with the lowest SD and MSE. An artificial neural network (ANN) was trained using the MIT-BIH database with a training accuracy of 93.9 % and an R² value = 0.876. The diagnostic tool was tested on 15 subjects and achieved a mean test accuracy of 75%.

In this paper, machine learning models for an effective estimation of soil moisture content using a microwave short-range and wideband radar sensor are proposed. The soil moisture is measured as the volumetric water content using a short-range off-the-shelf radar sensor operating at 3–10 GHz. The radar captures the reflected signals that are post processed to determine the soil moisture which is mapped to the input features extracted from the reflected signals for the training of the machine learning models. In addition, the results are compared and analyzed with a contact-based Vernier soil sensor. Different machine learning models trained using neural network, support vector machine, linear regression and k-nearest neighbor are evaluated and presented in this work. The efficiency of the model is computed using root mean square error, co-efficient of determination and mean absolute error. The RMSE and MAE values of KNN, SVM and Linear Regression are 11.51 and 9.27, 15.20 and 12.74, 3.94 and 3.54, respectively. It is observed that the neural network gives the best results with an R2 value of 0.9894. This research work has been carried out with an intention to develop cost-effective solutions for common users such as agriculturists to monitor the soil moisture conditions with improved accuracy.

A small zero-order resonant antenna based on the composite right-left-handed (CRLH) principle is designed and fabricated without metallic vias at 30 GHz to have patch-like radiation. The mirror images of two CRLH structures are connected to design the antenna without via holes. The equivalent circuit, parameter extraction, and dispersion diagram are studied to analyze the characteristics of the CRLH antenna. The antenna was fabricated and experimentally verified. The measured realized gain of the antenna is 5.35 dBi at 30 GHz. The designed antenna is free of spurious resonance over a band width of 10 GHz. A passive beamforming array is designed using the proposed CRLH antenna and the Butler matrix. A substrate integrated waveguide is used to implement the Butler matrix. The CRLH antennas are connected to four outputs of a $4\times 4$ Butler matrix. The scanning angles are ${12}^{\circ }$, ${-68}^{\circ }$, ${64}^{\circ }$, and ${-11}^{\circ }$ for excitations from port 1 to port 4 of the $4\times 4$ Butler matrix feeding the CRLH antenna.

A novel wide band matching circuit for the series fed patch array antenna at 80 GHz is proposed in this paper. The series fed patch array is designed with amplitude tapered configuration. First, the series fed patch array is matched using stub loaded transmission line (TL) with narrow band. Later, it is converted to wide band matching circuit using three quarter wave transformers and two half wavelength stubs. The sizes of these half wavelength stubs are reduced using the stub loaded and step impedance TLs. The simulated results of the series fed patch array with and without the connector are presented. The simulated -10 dB reflection coefficient bandwidth with connector is from 77.125 GHz to 83.95 GHz and the simulated co-polarized gain with connector is 13.73 dBi. The designed antenna array is fabricated along with the matching circuit and tested experimentally. The measured -10 dB reflection coefficient bandwidth is from 76.73 GHz to 86.08 GHz with the measured gain of the antenna is 13.3 dBi at 81.44 GHz.

The uniplanar implementation of double periodic composite right/left‐handed (DPCRLH) symmetric unit cell is realized using coplanar waveguide and its analysis with parameter extraction are studied. DPCRLH symmetric unit cell is then experimentally validated. The open‐circuited DPCRLH resonator is formed from the DPCRLH unit cell which exhibited five resonance points. The simulated resonant frequencies of the resonator are 1.5494, 2.1968, 3.5072, 5.0438 and 6.089 GHz. A triple‐band antenna is designed from the last three resonant frequencies of the resonator. The antenna is horizontally polarized in all three bands. The measured co‐polarized gain of the antenna at the central frequencies of the three bands are 1.52 dBi (3.59 GHz), 3.67 dBi (5.1694 GHz) and 1.78 dBi (6.0925 GHz), respectively.

A new dual polarized Huygens unit cell of 0.14 λ₀ thickness with two metal layers at W-band frequency range is designed, simulated and experimentally tested. The proposed unit cell has an electric dipole and a magnetic dipole for both horizontal and vertical polarizations to generate the Huygens resonance. The electric dipole has a metal strip with slot on the top and a strip on the bottom. The magnetic dipole has metal strips on the top and bottom surfaces. The electric surface admittance and magnetic surface impedance confirms the Huygens resonance at 78.49 GHz. A planar Huygens lens is designed by arranging twenty-one different unit cells whose parameters are varied to realize 360° transmission phase range. The Huygens lens increased the simulated realized gain of the horn antenna to 23.3 dBi in vertical polarization and to 20.6 dBi in horizontal polarization at 78.5 GHz when simulated with the horn antenna of gain 13.8 dBi. The simulated 3 dB beam widths are reduced to 3.48° for vertical polarization and 4.36° for horizontal polarization at 78.5 GHz. The Huygens lens is tested experimentally, and the measured realized gain of the horn antenna is increased to 24.42 dBi for vertical polarizations and 18. 74 dBi for horizontal polarization at 78.7 GHz when the horn antenna gain is 20.2 dBi at 78. 7 GHz. The measured beam widths are reduced to 2.66° for the vertical polarization and 2.7° for the horizontal polarization from 13.06°of the feed horn antenna.