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.     

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.