In this paper, a compact two ports Multiple Input Multiple Output (MIMO) antenna for Ultra Wide Band (UWB) application has been proposed. The presented antenna consists of two symmetrical radiators, developed on an FR4 substrate with overall size of 34 × 18 × 1.6 mm³. The proposed antenna is fed with a 50 Ω microstrip line. The antenna has good impedance matching in the range of UWB band. The isolation is lower than -15 dB from 3.1 to 5 GHz and < -18 dB from 5 GHz to 11 GHz. Envelope Correlation Coefficient (ECC) < 0.01 and Diversity Gain (DG) > 9.96 dB. The performance of the proposed antenna is analyzed and examined in term of return loss, gain, radiation efficiency, ECC, DG, and isolation between two ports.

This paper presents the design and analysis of a wideband circularly polarized resonant cavity antenna (RCA). The antenna structure consists of dual-layer Jerusalem cross type partially reflective surface (PRS) above a two-port wideband circularly polarized patch antenna. The PRS enhances the gain of the feeding patch antenna over wide range of frequencies. The structure provides left hand as well as right hand circular polarizations. Parametric analysis of the structure is also presented. The measured 10 dB return loss bandwidth and 3 dB axial ratio bandwidth of the RCA are 25 % (8.24-10.63 GHz) and 28.8% (8.3 GHz-11.1 GHz), respectively. Isolation more than 10 dB is obtained for the frequency range 9.15-10.61 GHz. Measured results show peak realized gain of 9 dBi in the operating band.

The retrieval of soil moisture in presence of vegetation has received relatively less attention than bare land when observations are made with Global Navigation Satellite System (GNSS). In plane bare land, the reflected GNSS signal is affected by the land characteristics which is dielectric constant of soil. However, in vegetated land, the reflected signal is affected by dielectric constant of soil as well as the characteristics of vegetation which makes the retrieval of soil moisture a cumbersome task in presence of vegetation. Monitoring soil moisture in vegetated land is important for soil health and its suitability for agriculture purposes. Therefore, analysis of soil moisture in presence of vegetation has been studied in this manuscript by utilising the Navigation with Indian Constellation (NavIC) which is a very new entry in GNSS domain by Indian Space Research Organization (ISRO). NavIC receiver setup was installed in a wheat agriculture land situated in Dehradun, India. The wheat crop was sown in the month of November, and it was harvested in the month of April. In situ measurement of soil moisture, crop height, humidity, soil temperature and air temperature were made. Fixed frequency method and Lomb–Scargle Periodogram (LSP) method have been analysed to determine the sensitivity of soil moisture in presence of vegetation. 15° to 30° elevation angle was utilised in the study. The sensitivity analysis was carried out by categorizing the crop based on crop height. Three crop categories have been considered which are 0 to 20 cm, 20 to 80 cm, and greater than 80 cm. The correlation coefficient in the first stage of crop growth using the fixed frequency method was 0.76, which decreased to 0.42 in second stage of crop growth and finally to 0.35 in final stage of crop growth. The correlation coefficient using LSP method was -0.68, -0.65, and -0.50 for the first, second, and third stages of crop growth, respectively. It was observed that for lower crop height (< 20 cm) fixed frequency method is more useful than LSP method. However, for higher crop height (> 20 cm) LSP method is better suited.

This paper discusses the variation of ionospheric Total Electron Content (TEC) over low latitude Indian region, Hyderabad station (Lat: 17.39^oN, Lon: 78.31^oE) for geomagnetic quiet and disturbed days during the low solar activity period (2017 year) of the 24th solar cycle using global ionospheric models and experimental NavIC (Navigation with Indian Constellation) data. The work mainly focuses on the performance of the IRI Plas 2017 (International Reference Ionosphere) model with and without assimilation of TEC input, GIM TEC (Global Ionospheric Maps) and IRI 2016 models. In order to evaluate the performance of the models, the diurnal, monthly, and seasonal variations of Vertical TEC (VTEC) are predicted and compared with Indian regional NavIC data. From the result analysis it is observed that smaller Root Mean Square Errors (RMSEs) between NavIC VTEC and modelled VTEC are found in June and December solstice months than March and September equinox months. The VTEC predicted by the IRI Plas with assimilation of TEC input option produced smaller estimation errors than IRI Plas without assimilation of TEC input and IRI 2016 model. The same analysis has been tested for geomagnetic storm occurred during 7-9 September, 2017 for different locations. The IRI Plas 2017 with TEC input option exhibits better performance than IRI Plas and IRI 2016 models. Therefore, the VTEC predictions by assimilation of optional inputs will be helpful in applications of ionspheric studies to predict the dynamics in the ionosphere particularly for the period of disturbed geomagnetic conditions.

A novel Artificial Neural Network (ANN) based two Substrate integrated waveguide (SIW) bandpass filters comprising Complementary Split Ring Resonators (CSRRs) are proposed in this paper. These CSRRs are modelled on the upper layer of the SIW cavity. A feed forward multilayer perceptron (FF-MLP) neural network is used to optimize the physical dimensions of the proposed filters. To validate the analytical results, physical prototypes of the proposed filters are fabricated, and a measurement is carried out with a Combinational Network Analyzer (Anritsu-MS2037C), and the obtained experimental results agree well with the estimated results using full wave analysis. Within the passband from 8.22 to 8.95 GHz, S₁₂ of the first filter shows better than -0.5 dB insertion loss (IL) and a fractional bandwidth of 8.5%, and within the passband from 8.21 to 8.73 GHz, the second filter shows IL about -0.8 dB and a fractional bandwidth of 6.1%.

A compact and hexagon-shaped microstrip patch antenna operating in three bands is described in this paper. Multiband functionality of the antenna is achieved by adding two inclined strips and cutting modified slots on the radiating patch. The antenna consists of a hexagonal patch and partial ground plane, has the total dimensions of 15×17 ×1.6 mm³, operates over three frequencies 5.40 GHz, 6.76 GHz, and 8.82 GHz for WLAN, TV satellite broadcasting, WiMAX (5250-5850 MHz), IEEE 802.11a (5.47-5.725 GHz), 5G Unlicensed band (5.2-5.7 GHz), weather monitoring, and radar applications. This antenna has the novelty that it can also be used as a reconfigurable antenna, and the notched bands can be controlled. Simulation of the proposed antenna is carried out using HFSS-15 software. To verify the simulated results, and a prototype of the proposed antenna is fabricated. After measurement, simulated and measured results are in good agreement.

A compact triple-band antenna of size 20×13×1.6 mm³ for WLAN (2.4/5 GHz) and WiMAX (3.5 GHz) applications and a metamaterial slab for Specific Absorption Rate (SAR) reduction are proposed in this paper. The antenna comprises a rectangular patch with two conjoint square split rings, attached along its top edge, to excite two resonances in the 2.5 GHz and 5.5 GHz range. The antenna is also backed with a slotted ground plane structure to achieve miniaturization. The radiator is subsequently slotted to yield the third tone around 3.5 GHz. Several parameters are tuned independently to achieve the desired bands of resonance around (2.2-2.6) GHz, (3.40-3.60) GHz, and (5.0-6.9) GHz with impedance bandwidths of 17%, 5.5%, and 46%, respectively. To validate the simulated results, the designed antenna is fabricated and measured experimentally. Later, a metamaterial slab composed of a 5×3 array of pentagonal split-rings printed on a 20×13×1.6 mm³ FR-4 substrate is placed above the antenna at a suitable distance to increase the gain as well as to reduce the SAR. Inclusion of this slab improved the maximum radiation efficiency and gain of the proposed antenna from 65% and 2.7 dB to 80% and 3 dB. A cubical tissue model is designed and used for simulation. SAR reduction of 84.5% is inferred with the metamaterial slab. This paper has taken a cubical tissue model for SAR calculation, which can be further enhanced by taking a human phantom model in future.

A problem of scattering of electromagnetic waves by thin impedance biconical vibrators in а free space and in a rectangular waveguide is solved by an asymptotic averaging method and a generalized method of induced electromotive forces (EMF). An influence of the change of vibrator radius upon energy and spatial characteristics is numerically studied. Theoretical results are compared with the experimental data.

This article presents a textile dual band antenna printed on an artificial heart (AH) bag for various Wireless Body Area Network (WBAN) communications. The textile dual band antenna operates at two different operating frequencies 2.4 GHz and 5 GHz. The two operating frequencies are reserved for IEEE 802.11b/g/n/ax and IEEE 802.11j WLAN standard. The designed antenna has a frequency bandwidth of (2.3642-2.5375 GHz) for the lower frequency of 2.4 GHz and (4.598-5.1683 GHz) for the upper frequency of 5 GHz. The dual band antenna is integrated with the proposed AH bag that is made from textile material. The effects of both different materials and dimensions of the proposed AH bag in the characteristics of the proposed antenna are investigated. The effect of the human body on the electrical performance of the proposed antenna integrated with the AH bag is presented. The amount of electromagnetic absorbed energy through the human body is also determined in terms of the specific absorption rate (SAR). The obtained SAR value is less than 0.12 W/Kg. This value meets the IEEE standards. Experimental verification for antenna integrated with AH bag and human body is presented.

In this paper, we present a broadband flexible RFID sensor tag antenna to detect the concentration of aqueous solutions. The proposed RFID tag antenna sensor with a T matching network is based on a printed dipole whose arms are loaded with circular disk patches. The structure is printed on a Kapton polyimide flexible substrate. The sensing mechanism of the RFID tag antenna is based on the change of sensitivity of the RFID tag antenna that occurs with the variation of aqueous solution concentration. The proposed sensor is designed using CST Microwave studio, and its various parameters are optimized in order to have a broadband impedance matching that covers the entire RFID band (860-960 MHz). The experimental setup is small, rapid, contactless, and inexpensive. Results are presented for NaCl and sugar aqueous solutions with concentrations ranging from 0% to 80%.

The ideality of operating environment of radar systems is extremely scarce while the demand for these systems is growing at a rapid pace. Technology of adaptation is therefore of primary concern in the design of their future strategies. The difficulty in finding a solution based on a single adaptive algorithm to deal with diverse noise environments has led to the development of composite adaptive procedure. Therefore, fusion of particular decisions of the single adaptive variants through appropriate rules provides a better final detection. This paper is intended to analyze the fusion strategy of cell-averaging (CA), order statistics (OS) and trimmed-mean (TM) schemes in heterogeneous environments. The tested target and the spurious ones are assumed to follow χ²-distribution with two- and four-degrees of freedom in their fluctuations. A closed form processor performance is derived. The results show that for the heterogeneous operation, this approach is more realistic. Particularly in multi-target situations, it exhibits higher robustness than CA, OS, or TM architecture. Additionally, our results reveal that it exhibits a homogeneous performance outperforming that of the Neyman-Pearson (N-P) detector which is the yardstick in the world of adaptive detection.

In this paper, a modified planar balanced Vivaldi antenna with endfire characteristics near the metal surface is proposed for 6-18 GHz applications. The proposed antenna structure consists of three copper layers, among which two external layers locate on the two outsides of two dielectric substrates, and the central layer is sandwiched by these two dielectric substrates. To further enhance the end-fire radiation characteristic, a number of novel techniques are proposed, including elongation and shaping of the supporting substrate of a conventional balanced antipodal Vivaldi antenna beyond its aperture, using an I-shaped slot loaded radiation patch and cutting a triangle on the edge of three copper layers. Measured and simulated results show that the proposed antenna not only exhibits good impedance bandwidth, but also improves the end-fire performance in the operational frequency of 6-10 GHz and achieves high gain in the end-fire direction, low cross-polarization and high front-to-back (F-to-B) ratio.

In this paper, two microstrip antennas with a U-slot on the patch are presented for base station applications to provide simultaneous communications for uplink and downlink respectively. The intended antennas are expected to operate in triple bands, i.e., to cover GSM and LTE bands. The three designated bands for uplink antenna are from 823 MHz to 830 MHz for lower band, 1.738 GHz to 1.761 GHz for middle band and 2.321 GHz to 2.355 GHz for upper band. Similarly, the antenna which is designed for downlink operates in three bands from 872 MHz to 880 MHz for lower band, 1.81 GHz to 1.85GHz for middle band, and 2.338 GHz to 2.375 GHz for upper band. These frequency band(s) satisfy the requirements of GSM850, GSM1800, and LTE2300 bands. Comparisons among designed, simulated and measured results are presented. Isolation parameters and the Envelope Correlation Coefficient (ECC) values of Multiple Input Multiple Output (MIMO) antenna in all specified bands are also presented.

We present a pin-Traveling wave Photodetector (TWPD) on semi-insulating (SI) InP substrate at 1.55 μm wavelength window with an electrical bandwidth of more than 120 GHz, a line characteristic impedance of about 50 W, and microwave index matched to the optical group index. The internal quantum efficiency more than 99% for a 200μm long device is determined. The layer stack of the TWPD has previously utilized in a semiconductor optical amplifier (SOA). The TWPD can be monolithically integrated with passive and active components such as arrayed waveguide grating (AWG), Mach-Zehnder Interferometer (MZI), laser and modulator.

The track-before-detect (TBD) methodologies jointly process more consecutive scans and show superior detection performance for the low signal-to-noise ratio (SNR) targets over the conventional methods. A TBD algorithm based on improved Randomized Hough Transform for dim target detection is proposed in this paper. This algorithm uses the sequence numbers of scans to make sure that the point pairs are selected from different scans, avoiding the unreasonable situation that the point pairs may be selected from the same scan in the traditional Randomized Hough Transform (RHT). Second, it introduces a new voting method. Based on the minimum Euclidean distance criterion, this voting method finds the optimal parameter cell to vote, making the voting result better than the traditional RHT. In addition, we not only increase score of the optimal parameter cell but also update the corresponding parameter, thus suppressing the deviation between the recovered track and the target's track. Simulation results demonstrate the proposed algorithm can detect the dim target more rapidly and accurately than traditional RHT, especially under the background of low SNR.

Tropical cyclone (TC) is part of the most serious natural disasters. Western Pacific is the region with the highest frequency of tropical cyclones (TCs). By simulating and correcting the brightness temperatures (TBs) of the microwave humidity and temperature sounder (MWHTS) onboard the Fengyun-3C (FY-3C) satellite, a method is proposed to observe the TCs in the Western Pacific. The Weather Research and Forecasting Model (WRF) and the fast Radiative Transfer model for TOVS (RTTOV) are adopted in our method. Then, simulated TBs are linearly corrected based on the field-of-views (FOVs), channels and latitude bands. After that, the biases of all channels are within 2 K and close to zero, and the RMSEs are less than 10-K except Channels 10 and 15. Therefore, this WRF/RTTOV method can be implemented in other TCs in the Western Pacific region. In addition, a precipitation detection algorithm is proposed and used to detect precipitation in the TC area. Compared with the FY-3C MWHTS and Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) precipitation products, the results indicate that our precipitation detection algorithm has reached better indicators. The potential application can lay a foundation for precipitation rate retrieval and further research.

The efficacy of including a defected ground structure (DGS) for mobile communication on a mobile phone PCB in improving the multiple input multiple output (MIMO) system performance is evaluated and demonstrated in the context of single and multiple-element two-port planar inverted-F antennas (PIFAs). The proposed scheme designed and developed for operation in the 3.5 GHz long term evolution (LTE) and future 5G frequency bands demonstrates efficiency improvement by 15% and capacity improvement by around 7% because of the significant reduction in mutual coupling between the antenna ports. Results in free space as well as next to a human head and hand phantom are presented.

This paper details the work of the LAPLACE Electromagnetism Research Group to develop an original measuring setup dedicated to the detection of an EMDrive like force. Recent peer-reviewed experimental results [1, 2] were obtained using similar setups based on a torsion pendulum combined with an optical sensor. These very accurate measurement setups are appropriate for measuring such an extremely weak force. They also appear costly, which may discourage other research teams from working on this topic. Our main goal is then to provide an alternative configuration, based on a commercial precision balance, in order to build a measuring setup more affordable, handy, and accurate enough to measure an EMDrive like force. Our experimental system is capable of feeding a truncated cone shaped 2.45 GHz resonant cavity with power up to 140 W. To calibrate the EMDrive force and avoid false positive thrusts, an original setup has been proposed and evaluated. It allows us to really consider that the parasitic effects do not alter the hypothetical force measurement by the use of force direction switching during the measurement.

This paper presents the performance of an Adaptive transmit beamspace beamformer (ATBBF) in a dynamic channel for Multiple input single output (MISO) per user wireless system. ATBBF consists of a of several transmit beamformers on the Transmit antenna array (TAA). The antenna weights of each Transmit beamformer (TB) are held constant while input to a TB is weighted by an adaptive beamspace weight. An algorithm that updates beamspace weights of all transmit beamformers of an ATBBF at the base station is described. It updates on the basis of a single feedback from the mobile. The feedback consists of one bit that indicates which of the two normalized perturbed beamspace weights that were time multiplexed onto the pilot signal from the base station delivered more power to the mobile. This algorithm is named Beamspace gradient sign feedback algorithm (BGSF) as its feedback mechanism is similar to that of Gradient sign feedback (GSF) algorithm that updates antenna weights of a TB. Performance metric of ATBBF is derived and analyzed in a dynamic channel undergoing Rayleigh fading. Performance comparison between an ATBBF with BGSF algorithm and a TB with GSF is made in terms of convergence and tracking of various slow and fast fading channels by simulations. Both full dimension (FD) and Reduced dimension (RD) ATBBF are considered. Comparisons show that FD ATBBF gives equivalent performance to that of TB and outperforms RD ATBBF.

A novel high performance four-port multiple input multiple output antenna is suggested for 5G application functioning at 3.4 GHz band. The antenna design measures an inclusive volume of 32 mm x 32 mm x 0.8 mm³. The broad frequency bandwidth, excellent gain, decreased interelement gap, and effective isolation within the MIMO components of the proposed system are clearly novel. Each antenna in the four-element MIMO system has been situated orthogonally to the others while maintaining a small size and good result. The antenna has exceptional average total efficiency in the 5G Sub-6 GHz spectrum and is in good agreement with the measured results. It also offers a high realized gain compared to prior MIMO antennas. The antenna has a high impedance matching whose isolation is about -28 dB, computed envelope correlation coefficient smaller than 0.10, channel capacity loss average value less than 0.2\,bits per second per hertz, and the diversity gain about 10 dB. The typical peak realized antenna gain of the offered MIMO antenna is also delivered with a high radiation efficiency at the frequency of 3.4 GHz. The reflection coefficient, mutual coupling, radiation pattern, current distribution, and gain of antennas are all measured and explained. The design has a compact high volume and adequate bandwidth with good accomplished gain making the antenna very strong for 5G application.