Low-voltage low-power CMOS RF low noise amplifier

In this paper, a 1 V, 2 GHz CMOS low-noise amplifier (LNA) was developed intended for use in the front-end receiver. The circuit is simulated in standard $0.25\mathrm{\mu }\mathrm{m}$ CMOS MOSIS. The LNA gain is 25.675 dB, noise figure (NF) is 4 dB, reverse isolation $(S_{12})$ is $-134.3\mathrm{dB}$, input return loss $(S_{11})$ is $-14.6\mathrm{dB}$, output return loss $(S_{22})$ is $-13.34\mathrm{dB}$, and the power consumption is 5.13 mA from a single 1 V power supply. One of the features of the proposed design is using a three-component cascode limitation, one of it is a transistor, to reduce the supply voltage.     

Low complexity PAPR reduction techniques for clipping and quantization noise mitigation in direct-detection O-OFDM systems

We present different distortionless peak-to-average power ratio (PAPR) reduction techniques that can be easily applied, without any symmetry restriction, in direct-detection (DD) optical orthogonal frequency division multiplexing (O-OFDM) systems based on the fast Hartley transform (FHT). The performance of DD O-OFDM systems is limited by the constraints on system components such as digital-to-analog converter (DAC), analog-to-digital converter (ADC), the Mach–Zehnder modulator (MZM) and electrical amplifiers. In this paper, in order to relax the constraints on these components, we propose to symmetrically clip the transmitted signal and apply low complexity (LC) distortionless PAPR reduction schemes able to mitigate, at the same time, PAPR, quantization and clipping noise. We demonstrate that, applying LC-selective mapping (SLM) without any additional transform block, the PAPR reduction is $1.5\text{dB}$ with only one additional FHT block using LC-partial transmit sequence (PTS) with random partitions; up to $3.1\text{dB}$ reduction is obtained. Moreover, the sensitivity performance and the power efficiency are enhanced. In fact, applying LC PAPR reduction techniques with one additional transform block and a 6 bit DAC resolution, the required receiver power for 8 dB clipping level and for a ${10}^{-3}\text{BER}$ is reduced by $5.1\text{dB}$.     

Mutual coupling between identical planar inverted-F antennas

Mutual coupling between two identical planar inverted-F antennas (PIFA) located on an infinite ground plane is studied numerically. Several arrangements of side-by-side, collinear, parallel-in-echelon, and orthogonal PIFA antennas with element spacing varying from $0.06\lambda$ to $1.20\lambda$ are investigated at the design frequency of 1.9 GHz, and in the $-6\mathrm{dB}$ bandwidth between 1.8 and 2.0 GHz. It is found that choosing configurations that maximizes the separation between the open-end of the PIFAs reduces the mutual coupling.     

A current-mode analog multiplier/divider based on CCCDTA

A novel simple current-mode analog multiplier/divider, based on current-controlled current-differencing transconductance amplifier (CCCDTA), is presented. The proposed circuit employs only single CCCDTA without any external passive element requirement and it can work as multiplier and divider without changing its topology. In addition, the proposed circuit can work as gain-controllable current amplifier. The circuit performances are depicted through PSPICE simulations. The simulated results show that: for $\pm 1.5\mathrm{V}$ power supply, the total harmonic distortion is about 0.1%, the $-3\mathrm{dB}$ bandwidth is more than 26.94 MHz, maximum input range is about $100\mathrm{\mu }A$ and the output current is low sensitive to temperature variations.     

Epitaxial lateral overgrowth of InP/GaAs (1 0 0) heterostructures by metalorganic chemical vapor deposition

Epitaxial lateral overgrowth (ELOG) was used to grow InP on GaAs(1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). The selectivity of InP by ELOG is excellent and the regrowth InP epilayers have good morphology without polycrystalline on SiO₂ mask. The [$0\overline{1}1$] directional mask stripes and high V/III ratio are benefit to InP lateral growth. Compared to conventional direct growth, ELOG is effective in reducing the dislocation density, relaxing compressing strain in epilayers. In addition, the full width at half maximum (FWHM) of X-ray diffraction (XRD) ω scans and room temperature (RT) photoluminescence (PL) for a 3 μm thick epilayer by ELOG are 198 arcsec and 44 meV, respectively.     

A miniaturized broadband bow-tie antenna with improved cross-polarization performance

In this paper, a modified broadband bow-tie antenna with low cross-polarization level and miniaturization is presented. The cross-polarization in both E- and H-planes are suppressed by defecting the antenna flares using rectangular slots. The proposed modified antenna demonstrated a cross-polarization improvement over $\pm 120°$ around the boresight from 2 to 5 GHz. In addition, an overall 23.5% of miniaturization compared to conventional bow-tie antenna is achieved. A tapered feed transition between microstrip-to-parallel stripline is designed to match 50 ohm SMA connector to the antenna flares. A prototype of the modified antenna is fabricated on RO4003 substrate ($\epsilon$_r = 3.38, tan $\delta$ = 0.0027, h = 0.813 mm), and its performance is experimentally studied. The antenna’s characteristics including return loss, gain and radiation pattern are measured, along with the time domain characteristics, and showed reasonable agreement with the simulated results.     

Structural,electrical and optical properties of N-doped ZnO films synthesized by SS-CVD

N-doped p-type ZnO films have been synthesized on α-Al₂O₃ (0 0 0 1) substrate by solid-source chemical vapor deposition using Zn(CH₃COO)₂·2H₂O as the precursor and CH₃COONH₄ as the nitrogen source. The properties for ZnO films are dependent greatly on the growth conditions. Results show that the best electrical properties of the p-type film, such as carrier density $\text{N=9.8×10}{}^{17}\text{cm}{}^{\mathrm{-3}}$, resistivity $\text{ρ=20}\text{Ω}\text{cm}$ and Hall mobility $\text{μ=0.97}\text{cm}{}^2\text{/}\text{V}\text{s}$, were induced at the substrate temperature of 500°C with a precursor temperature of 250°C and a nitrogen source of 150°C, under which the highest mixed orientation for (1 0 0) and (1 1 0) planes of films was also achieved. The p-type ZnO films possess a transmittance of about 90% in visible region and a band gap of about $\text{3.20}\text{eV}$ at room temperature.