A 77-dB Dynamic-Range Analog Front-End for Fine-Dust Detection Systems with Dual-Mode Ultra-Low Noise TIA

This paper presents an analog front-end for fine-dust detection systems with a 77-dB-wide dynamic range and a dual-mode ultra-low noise TIA with 142-dBΩ towards the maximum gain. The required high sensitivity of the analog signal conditioning path dictates having a high sensitivity at the front-end while the Input-Referred Noise (IRN) is kept low. Therefore, a TIA with a high sensitivity to detected current bio-signals is provided by a photodiode module. The analog front end is formed by the TIA, a DC-Offset Cancellation (DCOC) circuit, a Single-to-Differential Amplifier (SDA), and two Programmable Gain Amplifiers (PGAs). Gain adjustment is implemented by a coarse-gain-step using selective loads with four different gain values and fine-gain steps by 42 dB dynamic range during 16 fine steps. The settling time of the TIA is compensated using a capacitive compensation which is applied for the last stage. An off-state circuitry is proposed to avoid any off-current leakage. This TIA is designed in a 0.18 µm standard CMOS technology. Post-layout simulations show a high gain operation with a 67 dB dynamic range, input-referred noise, less than 600 fA/√Hz in low frequencies, and less than 27 fA/√Hz at 20 kHz, a minimum detectable current signal of 4 pA, and a 2.71 mW power consumption. After measuring the full path of the analog signal conditioning path, the experimental results of the fabricated chip show a maximum gain of 142 dB for the TIA. The Single-to-Differential Amplifier delivers a differential waveform with a unity gain. The PGA1 and PGA2 show a maximum gain of 6.7 dB and 6.3 dB, respectively. The full-path analog front-end shows a wide dynamic range of up to 77 dB in the measurement results.

A Highly Efficient Dual-Band Transmitarray Antenna Using Cross and Square Rings Elements

In this paper, a highly efficient dual-band transmitarray antenna using cross and square rings elements is presented for X and Ku bands. The dual-band transmitarray is designed for downlink/uplink frequencies of Ku band satellite communications. The transmitarray element consists of four metal patches and two dielectric substrates. The metal patch is printed on both sides of the substrate. By optimizing the parameters, the transmitarray element can achieve a transmission phase coverage greater than 360° and work independently in both frequency bands. Then, a method to select the size of the element is proposed, so that all the elements in the array can realize the transmission phase of the two frequencies as much as possible. A 201-elements transmitarray antenna is fabricated and measured and the band ratio of the antenna is 1.13. The measured maximum gain at 11.5 GHz is 22.4 dB, corresponding to the aperture efficiency is 52.7%. The measured maximum gain at 13 GHz is 24.2 dB, corresponding to the aperture efficiency is 62.4%. The 1-dB gain bandwidths are 9.7% (10.8-11.9 GHz) at X band and 9% (12.6-13.8 GHz) at Ku band.

WAVEGUIDE FEED NETWORK FOR HORN ANTENNA WITH CIRCULAR POLARIZATION

The article presents the methodology for designing and optimizing of feed network for a circularly polarized horn antenna. A horn antenna has a metal structure and consists of a waveguide that has a variable cross-section and an open radiating end. Electromagnetic waves in such antenna are excited by a waveguide that is connected to a horn antenna in through the narrow wall. The proposed feed network of the horn antenna consists of a rectangular waveguide with a slot. In order to obtain the excitation of signals with circular polarization at the output, a slot was cut in the waveguide at an angle of 45º. As a result, the network makes it possible to form the signals with right-hand circular polarization and left-hand circular polarization. The presented design of the horn antenna feed network eliminates the need to develop a separate waveguide device of polarization processing. The designed feed network of the circularly polarized horn antenna can be used at an operating frequency of 8.0 GHz. At these frequency the reflection coefficient is less than −19 dB. The proposed horn antenna provides a maximum gain of 21 dB for right-hand circular polarization and a maximum gain of 10 dB for left-hand circular polarization. Cross-polarization isolation is higher than 10 dB. Therefore, the developed feed network of the horn antenna provides narrowband operating mode at the circular polarization with satisfying electromagnetic polarization characteristics and matching at the frequency of 8 GHz. Developed feed network of the horn antenna with circular polarization can be used in radio engineering systems, which carry out polarization processing of signals.

Deformable Bowtie Antenna Realized by 4D Printing

4D printing is utilized to fabricate of thermo-deformable bow-tie antenna to fulfill some special applications with limited space or changing antenna property. In this paper, 4D printing is used to manufacture nylon and carbon fiber laminated composite material. The bow-tie antenna is installed on the surface of the composite material, and the carbon fiber is energized and heated, which causes thermal deformation of the substrate to reconfigure the antenna feature. The deformation mechanism of the composite material is explained, the characteristics of the thermally deformed bow-tie antenna with power applied to carbon fiber are analyzed. The results show that the energized carbon fiber heats up, causing the structure to stretch to a flat, with a maximum gain of 2.37 dBi and the −10 dB bandwidth being 4.28–4.64 GHz and 5.16–5.52 GHz, and the half-power beamwidth is greater than 60°. The structure bends at a 30° angle with a maximum gain of 3.58 dBi in the absence of external power, delivering a −10 dB bandwidth range of 4.12–5.6 GHz and a half-power beamwidth close to 45°. The customization of antenna radiation patterns and antenna gain can be readily tuned with power control.

Enhanced Frequency Reconfigurable Antenna for LTE Implementations

The design is focused on fabrication and testing of frequency reconfigurable antenna designed to operate in LTE and Wi-Fi implementations. The reconfigurable mechanism is governed by three PIN diodes and the operating bandwidth (1.38 GHz - 3.24 GHz) is efficiently controlled by diode’s different operating states. The antenna’s working principle is elucidated with the reflection coefficient, VSWR, gain and directivity characteristics. The antenna exhibits a maximum gain of 2.23 dBi and the VSWR of less than 1.5 throughout the bandwidth. The ON and OFF conditions of the diode go well with the desired operation and it does not induce the cross polarization. This work aims to design the simulations which are conceded using ANSYS HFSS full wave EM simulator and the measurements are in accordance with the simulated one.

Estimating the Academic Performance of Secondary Education Mathematics Students: A Gain Lift Predictive Model

Several socioeconomic, environmental, ethnic, family, and educational factors influence an individual’s academic performance and can determine their school performance in mathematics. Mathematical competence is one of the skills that allow students to build visions of the future from performance in the present. However, the perception that students have of mathematics, in addition to the teacher–student relationship, the classroom, gender, teaching–learning, and motivation are crucial factors for achieving an optimal academic performance and preventing school failure. The aim of the present study was: (1) to examine which variables of the dimensions “Learning Mathematics” and “School Environment” significantly contribute to the marks in the second quarter and quantify their relative importance; (2) to determine the optimal algorithm model for predicting the maximum gain in students’ marks in the second quarter and quantifying it; and (3) to analyze the maximum gain in terms of gender. A total of 2018 high school students in Melilla were included in this cross-sectional study. Mathematical learning and the school environment were assessed using a validated 14-item questionnaire. Gain lift was employed to quantify the improvement in students’ performance. The role of the classroom and teacher–student relationship had a greater influence on mathematics scores than affinity indicators, teaching, study time, teaching resources used, study aids, and motivation.

Design of Compact High Gain Multilayer Stacked Patch Antenna

In this paper a compact multilayer stacked patch antenna with high gain is proposed. The structure is composed of stacked patches with U slots and shorting pins. The proposed antenna is capable for resonating at the center frequency of 2.25 GHz. The performance of the antenna is characterized by the simulated result of bandwidth, gain and reflection coefficient. The antenna has reflection coefficient of less than -10 dB with a maximum gain of 7.07 dBi. The proposed antenna has bandwidth of nearly 400MHz and has less size with an overall height of 10.3 mm. The designed frequency range occupies S band which is used for various applications like weather radar, surface ship radar, Bluetooth and ZigBee.

Pass-Through and C Corp Outputs under TCJA

Corporate finance research focuses on C corps (CCs) neglecting pass-throughs (PTs). We answer this neglect by examining PT outputs for the categories of debt choice, valuation, and leverage gain. In the process, we expand on the nongrowth PT research and supplement the recent CC research on the same outputs. Before the Tax Cuts and Jobs Act (TCJA) became effective in January 2018, PTs had an after-tax valuation advantage over CCs. Under TCJA, we demonstrate this advantage has been reverse. This suggests that, ceteris paribus, a typical PT can now find it advantageous to switch to the CC ownership form. More importantly, we show that nongrowth firm values are comparable to growth firm values unless we assume a rise in growth consistent with projections under TCJA where tax rates are lower. We demonstrate this projected growth increase is the key to make businesses more profitable. Additionally, we show PTs achieve optimal debt-to-firm value ratios (ODVs) well below those for CCs; PTs generally attain slightly higher quality credit ratings at their ODVs compared to CCs; and, PTs have lower leverage gains outputs (in the form of the maximum gain to leverage and the percentage increase in unlevered firm value) compared to CCs.

QUADRIFILAR HELIX ANTENNA FOR WEATHER SATELLITE RECEPTION

The study designed and implemented quadrifilar helix antenna (QHA) for weather satellite signal reception. The antenna design and optimization were done by varying the element diameter, the radial lengths, the axial lengths, and element materials on adopted model. The simulated QHA has far-field radiation pattern in the upper hemisphere with maximum gain of 4.14dBi at 0o and omnidirectional coverage, half-power beamwidth of 140o, bandwidth of 6.5MHz, and VSWR of 1.13. The implemented QHA has major lobe in conformity with the simulated QHA with maximum gain of 10.75dB at 0o, and half-power beamwidth of 104o.