This communication presents a new approach to implement planar antipodal Vivaldi antenna design. A nature fern inspired fractal leaf structure is implemented here. Impedance bandwidth (−10 dB) of the proposed antenna is around 19.7 GHz starting from 1.3 to 20 GHz. The lower operating frequency of this antenna is reduced by 19% with the second iteration as compared to the first iteration of fractal leaf structure. The prototype antenna is fabricated and tested in frequency as well as in time domains to obtain various transfer characteristics along with common antenna parameters. Experimental results show that good wideband feature, stable radiation pattern, and promising group delay of less than 1 ns signatures are obtained, which agree well with the simulated data. The miniaturized proposed antenna structure becomes an attractive choice in microwave imaging applications because of its ultrawide fractional bandwidth at 175%, high directive gain of 10 dBi, and finally appreciably large fidelity factor above (>90%).

A Fern Fractal Leaf Inspired Wideband Antipodal Vivaldi Antenna for Microwave Imaging System

A compact antipodal Vivaldi antenna (AVA) with the dimension of $42 \times 36 \times 1.6~\hbox{mm}{^3}$ is proposed in this letter. Structural modifications in the radiating fins have increased the electrical length thereby reducing the lower operating frequency from 5.2 GHz to 3.7 GHz. Proposed antenna maintains $-20~\hbox{dB}$ copolarization to cross-polarization ratio throughout the operating bandwidth. The prototype is fabricated and the measurement results are presented to validate the performance of the proposed AVA.

A Compact Antipodal Vivaldi Antenna for UWB Applications

A continuous-time (CT) radio frequency (RF) antenna array beamformer and analog circuit based on a discrete-space-continuous-time (DSCT) 2-D fan-filter having transfer function HF,A(zx,sct) is derived. The proposed transfer function is based on a 2-D FIR discrete domain fan filter. The discrete domain prototype is converted to the proposed mixed-domain DSCT analog filter by replacing unit sampled delays with CT analog first-order all-pass networks corresponding to the bilinear transform. First-order all-pass network Φ(st) is a poor approximation to a CT delay exp(-sT) . To address this, a novel broadband pre-warping method is proposed to exactly compensate for such “bilinear warping”. A 65 nm CMOS VLSI circuit for Φ(st) is proposed and an example fan filter with axis oriented at θ0=35°, half-fan-angle e = 5° and maximum frequency Fu = 2.6 GHz is simulated employing closed-form expressions, an ABCD parameter based model and 65 nm CMOS simulations in Cadence. A stop-band interference rejection of 38 dB is verified by BSIM4 based simulations. The proposed circuit for Φ(st) operates at 3.7 mA from a 1.2 V supply. The beamfomer is shown to operate correctly in the presence of PVT variations of Φ(st).

RF Analog Beamforming Fan Filters Using CMOS All-Pass Time Delay Approximations

In this paper, a new, complete, and comprehensive breast phantom measurement system is presented. A side slotted vivaldi antenna is used for breast phantom measurement. The radiating fins are modified by etching six side slots to enhance the electrical length and produce stronger directive radiation with higher gain. This approach reduces the lower operating frequency and increases the gain and efficiency without compromising the size of the antenna. The overall size of the antenna is 8.8 ( ${L}$ ) $\times7.5$ ( ${W}$ ) cm $^{{ {2}}}$ or approximately $0.4\lambda \times 0.5\lambda $ at the first resonant frequency of 1.79 GHz. The results show that the antenna has a fractional bandwidth of approximately 127% from 1.54 to 7 GHz for return loss less than 10 dB with a directional radiation pattern. The average gain of the proposed prototype is 8.5 dBi, and the radiation efficiency is approximately 92% on average over the operating bandwidth. The fidelity factor for face to face is 0.98, and that for side by side is 0.4479, which proves the directionality and lower distortion of the signal. The prototype is successfully simulated, fabricated, and analyzed. The radiating fins of the proposed prototype are optimized to achieve the desired properties for breast phantom measurement. The antenna is used as the transceiver in a breast phantom measurement system to detect unwanted tumor cells inside the breast. An automated electromechanical imaging system with the necessary data post processing makes it an easy and suitable tool for microwave imaging to detect breast tumors.

Microwave Breast Phantom Measurement System With Compact Side Slotted Directional Antenna

A digital beamformer that can synthesize array factors (AFs) with multiple, ultrawideband (UWB), frequency-independent beams at lower computational complexity is proposed. The beamformer is based on a novel 3-D infinite impulse response (IIR) transfer function $H_{\rm MC}\left({\bf z}\right)$ having multiple cone-shaped passbands in the 3-D spatio–temporal (ST) frequency-domain $\mmb{\omega}\in\BBR^{3}$ . The magnitude frequency response and the AF of $H_{\rm MC}\left({\bf z}\right)$ are simulated for dual- and single-passband cases. An element pattern of a broadband Vivaldi antenna is simulated at 1.4 GHz and is used to obtain the total array pattern. Computational complexity of $H_{\rm MC}\left({\bf z}\right)$ for single-passband (1Cone) case and that of the conventional phased array (PA) beamformer are derived. The magnitude frequency response of the proposed beamformer for 1Cone case and that of the PA beamformer are compared using the mean square error (MSE). For the given selectivity specified by the half cone angle $\epsilon={\hbox {5}}^{\circ}$ , proposed beamformer provides around 60% lower MSE for the same complexity and around 90% lower complexity for the same MSE compared with the PA beamformer.

Broadband Multiple Cone-Beam 3-D IIR Digital Filters Applied to Planar Dense Aperture Arrays

A type of antipodal Vivaldi antenna is designed in this paper, which can be used for pulse radiation in UWB communication. Vivaldi antenna is a special tapered slot antenna with planar structure and is easy to be integrated with transmitting elements and receiving elements to form a compact structure. The antenna designed has good performance in the band 3.1GHz to 10.6GHz, which is assigned to Ultra Wide Band (UWB) wireless communication by FCC. The antenna proposed can radiate or receive UWB pulses with little distortion and a good directivity and a high efficiency.

Analysis and Design of UWB Vivaldi Antenna

The level of linked N-acetylglucosamine (O-GlcNAc) has been proved to be a sensor of cell state, but its relationship with hyperoxia-induced alveolar type 2 epithelial cells injure and bronchopulmonary dysplasia (BPD) has not been clarified. In this study, we evaluated if these effects ultimately led to functional damage in hyperoxia-induced alveolar cells.We treated RLE-6TN cells at 85% hyperoxia for 0, 24 and 48 h with Thiamet G (TG), an OGA inhibitor; OSMI-1 (OS), an OGT inhibitor; or with UDP-GlcNAc, which is involved in synthesis of O-GlcNAc as a donor. The metabolic rerouting, cell viability and apoptosis resulting from the changes in O-GlcNAc glycosyltransferase levels were evaluated in RLE-6TN cells after hyperoxia exposure. We constructed rat Park2 overexpression and knockdown plasmmids for in vitro verification and Co-immunoprecipitation corroborated the binding of Parkin and O-GlcNAc. Finally, we assessed morphological detection in neonatal BPD rats with TG and OS treatment.We found a decrease in O-GlcNAc content and levels of its metabolic enzymes in RLE-6TN cells under hyperoxia. However, the inhibition of OGT function with OSMI-1 ameliorated hyperoxia-induced lung epithelial cell injury, enhanced cell metabolism and viability, reduced apoptosis, and accelerated the cell proliferation. Mitochondrial homeostasis was affected by O-GlcNAc and regulated Parkin.The results revealed that the decreased O-GlcNAc levels and increased O-GlcNAcylation of Parkin might cause hyperoxia-induced alveolar type II cells injurys. 

https://respiratory-research.biomedcentral.com/counter/pdf/10.1186/s12931-022-02287-0

O-linked N-acetylglucosamine affects mitochondrial homeostasis by regulating Parkin-dependent mitophagy in hyperoxia-injured alveolar type II cells injury

Li Tianming

Papers

Analysis and Design of UWB Vivaldi Antenna

O-linked N-acetylglucosamine affects mitochondrial homeostasis by regulating Parkin-dependent mitophagy in hyperoxia-injured alveolar type II cells injury