A novel 4-element UWB MIMO (multiple-input multiple-output) slot antenna with triple band-notched characteristics is designed and fabricated. It is composed of four rectangular slot antennas with two C-slots and a T-slot. To improve the isolation, cross-shaped branches are added. The measured results demonstrate that the antenna can operate ranging 2.51-11.07 GHz with the impedance bandwidth (S11 < -10 dB) of 856 MHz except three rejected bands, including 3.02-4.07 GHz, 4.54-5.83 GHz and 7.88-9.38 GHz, and the inter-element isolation of antenna in the range of UWB band is higher than 21 dB. The presented antenna can filter the interference of WiMAX (3.3-3.7 GHz), WLAN (5.15-5.825 GHz) and X-band (7.9-8.4 GHz). What's more, the parameters of diversity performance like envelope correlation coefficient (ECC), diversity gain (DG), efficiency, gain, channel capacity loss (CCL), mean effective gain (MEG) and total active reflection coefficient (TARC) have been analyzed. Based on the analysis on simulated and measured results, the proposed MIMO antenna is competent for UWB applications with notched bands for WiMAX, WLAN and X-band.
Low power, near-field (NF) radar imaging techniques have been proposed for breast cancer detection and long-term monitoring. It is important to optimize the data processing paths required for NF image reconstruction given the inherent resolution limitations of microwave compared to MRI or X-ray imaging. A key limitation in obtaining internal tumour and breast feature information is the reflection from the skin surface physically close to the antenna. Typically, algorithms to remove this dominant reflection involve subtracting an estimate of the time domain signal for the skin reflection from one antenna location using information from other locations. A key challenge in these approaches is determining the portion of the signal, the skin dominant window (SDW), to use to determinethe weights applied to nearby antenna signals when calculating the skin reflection estimate. Equipment limitations and breast characteristics impact the amount of data that can be captured, leading to the well-known Gibbs' ringing distortionsin the time domain signals. We suggestthat the Gibbs' ringing from the magnitude larger skin reflection has caused the length of the SDW to be over-estimated in previous determinations. Since this distorted signal now overlaps the time signals from the tumour and breast responses, removing the skin reflection estimatemay result in attenuation of tumour responses. In this contribution, two alternative strategies for designing the SDW are proposed. One minimized the first skin peak in the SDW, i.e., the furthest from the breast feature signals, and the other minimized the main, i.e., largest, skin peak within the SDW. Both new approaches were shown to effectively suppress the skin signal on simulated and patient data while allowing recovery of the missing portions of the desired internal breast feature signals leading to an increase in the overall intensity of the images and preserving the tumour response. However, we provided reasons why we considered that basing the suppression on the largest skin signal peak would provide a more consistent improvement in the breast feature signals.
In recent years, additive manufacturing has found increasing interest in fabrication of dielectric antennas. Using additive manufacturing brings significant advantages such as design flexibility, compactness, fast and low-cost manufacturing compared to traditional fabrication methods. Dielectric antennas having dense material allow high power transfer efficiency through the lens. However, a successful 3D printing process with dense dielectric materials is a great challenge. In this paper, impact of main process parameters during 3D printing; namely printing speed, process temperature and layer height on the resulted relative electrical permittivity values of a dense dielectric material is investigated. Test samples are printed with a dielectric material having εr = 10, and relative permittivity variations of these samples are measured with a vector network analyzer in X-band (8.2-12.4 GHz). In this way, optimum printing parameters are determined. Influence of dielectric constants of printed materials on the antenna radiation characteristics are inspected for an extended hemispherical lens antenna by a full-wave computer-aided design tool. Results demonstrate that an additively manufactured dense dielectric antenna will act as a traditionally manufactured dielectric antenna if and only if it is manufactured with optimum printing parameters.
As the advanced technology in the Internet of Things (IoT), ultra-high frequency radio frequency identification (UHF RFID) tag has broad application prospects and significant research value. However, the transmission performance of UHF RFID on the metal surface and embedded in metal is severely impaired, bringing new challenges to its application for long-distance reading and writing. On this basis, an embedded metal UHF RFID tag design method is proposed in this paper. A planar inverted F antenna (PIFA) structure is optimized to enhance the anti-metal performance of the tag. The embedded feed design is adopted to achieve preferable impedance matching between antenna and chip. Besides, a series of electromagnetic simulations were investigated to optimize the performance of the tag, which can ultimately achieve the maximum gain of -9.7 dB in the metal groove, with the reduced volume of 19.8 mm×25.8 mm×2 mm by employing the meandering technology and the method of adding metal via holes. Finally, when the self-made tag is embedded in the metal groove, the experimental results demonstrate that the maximum reading distance can reach 1.26 m, indicating that the tag developed in this paper has significant practical value in the case of embedded metal.
A MIMO antenna for smartphones with radiation diversity is presented in this article. The proposed design consists of dual-fed Complementary Split Ring Resonator metamaterial antenna components design, which is located at the edges of an FR-4 substrate. The total dimension is 75 mm x 150 mm x 1.6 mm. 50-ohm dual microstrip feed lines placed orthogonal to each other are used to feed the SRR. Due to this orthogonality, radiation diversity is easily achieved. The proposed structure is operated in dual bands from 3.43 GHz to 3.62 GHz and 4.78 GHz to 5.04 GHz. In both, the band's good impedance bandwidth with a reasonable gain is achieved. The entire structure is simulated using CST EM software. All the simulated results are presented, which clearly show that the proposed structure is a good candidate for the future smartphone massive MIMO application.
A multiband circularly polarized microstrip patch antenna including a Minkowski fractal slot for wireless communication applications in the frequency bands 1.39 GHz, 2.45 GHz (WLAN band), 3.48 GHz (Mobile Wi-Max), 5.8 GHz (U-NII high-band) and 6.29 GHz has been proposed. The proposed antenna consists of two substrates mounted on top of the ground plane. The antenna has been fed with a 50 Ω microstripline which is etched on top of the lower substrate. The second iteration Minkowski fractal slot is etched on the truncated square patch which is on top of the upper substrate. The substrate has a size of 80 mm x 82 mm x 1.6 mm. The measured results show that the proposed antenna could excite for five resonant bands of 1.35 GHz, 2.45 GHz, 3.5 GHz, 5.8 GHz and 6.25 GHz and has reflection coefficients of -15 dB for 1.35 GHz, -16 dB for 2.45 GHz, -22 dB for 3.5 GHz, -23 dB for 5.8 GHz and -13 dB for 6.25 GHz as well as an axial ratio bandwidth of 3.42 GHz-3.47 GHz. The maximum gains of the antenna are 5.92 dBi for 1.39 GHz, 6.15 dBi for 2.45 GHz, 8.36 dBi for 3.48 GHz, 9.64 dBi for 5.8 GHz and 6.69 dBi for 6. 29 GHz. The simulations and optimizations have been carried through Computer Simulation Technology Microwave Studio (CST-MWS) software.
A compact pot-shaped Multiple Input Multiple Output (MIMO) Antenna with Triple notched band characteristics is presented for Ultra Wide Band (UWB) Applications. The comprehensive dimension of the presented antenna is 17×32 mm2. The presented antenna has two identical pot-shaped radiators, 7-shaped stubs, T-shaped strips, M and C-shaped slots. Two novel 7-shaped stubs are connected to the antenna ground plane to obtain -22 dB enhanced isolation. The presented antenna works from 2.95 to 12.1 GHz with triple stopped WiMAX, WLAN, and X bands. A novel T-shaped strip is connected to the antenna ground plane to stop the WiMAX band (3.3-4.4) GHz. C and M-shaped slots are etched in the antenna radiators to stop WLAN (5.20-6.12) GHz and X (7.6-8.15) GHz bands respectively. The peak gain of the proposed antenna is from 1.5 to 5 dB with a radiation efficiency of 80-90%. The Envelope Correlation Coefficient (ECC) of the proposed antenna is less than 0.01 with a Diversity Gain greater than 9.99 except for the notched bands.
In this paper, a rectangular eight shaped Electromagnetic Band Gap (EBG) structure at 5.8 GHz Industrial, Scientific and Medical (ISM) band for wearable application is proposed with intent to improve impedance bandwidth of antenna. The unit cell of an EBG structure is formed using eight shape on outer ring with inner square patches. The simulation of the eight shape EBG unit cell is carried out using eigen mode solution of Ansys High Frequency Structure Simulator (HFSS). Simulated results are validated by experimental results. The application of proposed EBG for an inverse E-shape monopole antenna at 5.8 GHz is also demonstrated. Band stop property of EBG structure reduces surface waves, and therefore, the back lobe of a wearable antenna is reduced. The frequency detuning of antenna takes place due to high losses in human body. Suitably designed EBG structure reduces this undesirable effect and also improves front to back ratio. The proposed compact antenna with designed EBG has observed the impedance bandwidth of 5.60 GHz to 6.15 GHz which covers 5.8 GHz ISM band. Evaluation of antenna performance under bending condition and on-body condition is carried out. Effectiveness of EBG array structure for Specific Absorption Rate (SAR) reduction on three layer body model is demonstrated by simulations. Calculated values of SAR for tissue in 1 g and 10 g are both less than the limitations. In conclusion, it is appropriate to use the proposed antenna in wearable applications.
Cross polarization (X-pol) effect is the undesired radiation of an antenna which wastes bandwidth (BW) and power of the communication system. Especially in the miniaturized microstrip antenna (MSA) the X-pol level is more. The observed X-pol level of the classical MSA at the direction of maximum radiation (φ =0˚) is -49.72 dB, whereas X-pol level of miniaturized H shaped MSA (MHMSA) is -39.96 dB. This paper presents miniaturized complementary split ring resonators loaded H shaped microstrip antenna (CSRR-MHMSA) and slots and CSRRs loaded MHMSA (S-CSRR-MHMSA) with reduced X-pol level. An array of CSRRs and slots are placed at the ground of the proposed antenna. Due to slots, the antenna is miniaturized and the polarizability of the electric field along the desired direction is increased by CSRRs. The CP-XP (Co-pol X-pol) isolation of CSRR-MHMSA and S-CSRR-MHMSA at φ =0˚ are measured. The measured E plane CP-XP isolation for CSRR-MHMSA and S-CSRR-MHMSA is 29.00 dB and 26.73 dB respectively. The measured CP-XP H plane isolation for CSRR-MHMSA and S-CSRR-MHMSA is 27.00 dB and 24.5 dB, respectively. While bandwidth (BW), gain G and radiation efficiency η are improved.
This work presents high isolation UWB-MIMO antenna with a bandwidth of up to 8.6 GHz based on a Minkowski fractal structure. The proposed antenna is fed by microstrip and be comprises two orthogonal monopole antennas, which delivers a decent isolation effect. Moreover, the ground is designed as two separated blocks with an I-shaped branch for improving the isolation degree between the units. The resultant isolation degree of this antenna is greater than 25 dB. Besides, the electromagnetic interference in the partial frequency band (such as Wi-Max band (3.45-4.45 GHz), WLAN band (5.1-5.8 GHz) and X-band (7.25-7.75 GHz)) is further prevented through etching a split-ring resonator (SRR) and C-slot on the unit. The antenna reflection coefficient of the UWB-MIMO antenna at the notch is 3.5 dB, which indicates that the antenna has a conspicuousness anti-interference effect. Through the above judicious design, the proposed UWB-MIMO antenna possesses a relative bandwidth of 113% (up to 8.6 GHz), and the envelope correlation coefficient between antenna units is less than 0.005, and the antenna radiation efficiency is up to 80%. The results indicate that the proposed MIMO antenna meets UWB applications.
In this paper, a novel design of a small printed Ultra-Wideband (UWB) Multi-Input Multi-Output (MIMO) antenna with a wide impedance bandwidth from 3.05 GHz to 11.65 GHz is introduced. The newly designed UWB MIMO antenna has an isolation enhancement of more than -15 dB between the two elements. This isolation is achieved by inserting a three-line stub on the ground plane between the two radiating elements. In addition, these parallel lines improve the impedance matching and the bandwidth of this structure. Dual band notched characteristics are achieved for the 5G band (3.6 GHz) and the Wi-fi 6E application (6 GHz), by loading the split ring resonator (SRR) on the ground plane at the back of antenna and etching a complementary split ring resonator (CSRR) in both the truncated square patch elements, respectively. The SRR and its complement are metamaterials structures, showing the behavior of an LC resonator circuit. The hybrid technique improves impedance matching, bandwidth, minimizes the mutual coupling in UWB frequency range, and delivers dual-notch characteristics. The simulation and measurement results of the proposed antenna with a good agreement are presented. The proposed structure exhibits high performances in terms of envelope correlation coefficient (ECC), diversity gain (DG), efficiency, total active reflection coefficient (TARC), and channel capacity loss (CCL) except the notched band.