An interactive evolutionary algorithm for MMIC low noise amplifier design

A layer-encoded interactive evolutionary algorithm (IEA) for optimization of design parameters of a monolithic microwave integrated circuit (MMIC) low noise amplifier is presented. The IEA comprises a combination of the genetic algorithm (GA) and the particle swarm optimization (PSO) technique. The layer-encoding structure allows human intervention in order to accelerate the process of evolution, whereas the GA and PSO technique are incorporated to enhance both global and local searches. With this combination of features, the proposed IEA has shown to be efficient in meeting all requirements and constraints of the MMIC. In addition, the IEA is able to optimize noise figure, current, and power gain of the MMIC amplifier design.

An interactive genetic algorithm approach to MMIC low noise amplifier design using a layered encoding structure

In this paper, an interactive genetic algorithm (IGA) approach is developed to optimize design variables for a monolithic microwave integrated circuit (MMIC) low noise amplifier. A layered encoding structure is employed to the problem representation in genetic algorithm to allow human intervention in the circuit design variable tuning process. The MMIC amplifier design is synthesized using the Agilent Advance Design System (ADS), and the IGA is proposed to tune the design variables in order to meet multiple constraints and objectives such as noise figure, current and simulated power gain. The developed IGA is compared with other optimization techniques from ADS. The results showed that the IGA performs better in achieving most of the involved objectives.

Peak to average power ratio analysis for LTE systems

The 3rd generation partnership project (3GPP) long term evolution (LTE) standard uses single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions and orthogonal frequency division multiplexing access (OFDMA) in downlink. SCFDMA uses DFT spreading prior to OFDMA modulation to map the signal from each user to a subset of the available subcarriers i.e., single carrier modulation. The efficiency of a power amplifier is determined by the peak to average power ratio (PAPR) of the modulated signal. In this paper, we analyze the PAPR in 3GPP LTE systems using root raised cosine based filter. Simulation results show that the SCFDMA subcarrier mapping has a significantly lower PAPR compared to OFDMA. Also comparing the three forms of SCFDMA subcarrier mapping, results show that interleave FDMA (IFDMA) subcarrier mapping with proposed root raised cosine filter reduced PAPR significantly than localized FDMA (LFDMA) and distributed (DFDMA) mapping. This improves its radio frequency (RF) power amplifier efficiency and also the mean power output from a battery driven mobile terminal.

PAPR reduction technique for LTE OFDMA systems

Long term evolution (LTE) is the final step toward the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile networks. LTE uses orthogonal frequency division multiple access (OFDMA) for the downlink transmission and single carrier-frequency division multiple access (SC-FDMA) for uplink. OFDMA meets the 4G requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. However, the potentially large peak-to-average power ratio (PAPR) of the transmitting signals has limited its application. This high PAPR causes interference when the OFDM signals are passed through an amplifier which does not have enough linear range. In this article, we investigate a clipping based PAPR reduction method for LTE OFDMA systems. Simulation results show that the clipping method is reduced PAPR significantly which decreases as the number of clip and filtering level is increased. As a results, increase the mean transmit power, and improve the power amplifier efficiency. This comes at the outlay of complexity, efficiency as well as cost.

Wireless instantaneous neurotransmitter concentration system-based amperometric detection of dopamine, adenosine, and glutamate for intraoperative neurochemical monitoring - laboratory investigation

Object  In a companion study, the authors describe the development of a new instrument named the Wireless Instantaneous Neurotransmitter Concentration System (WINCS), which couples digital telemetry with fast-scan cyclic voltammetry (FSCV) to measure extracellular concentrations of dopamine. In the present study, the authors describe the extended capability of the WINCS to use fixed potential amperometry (FPA) to measure extracellular concentrations of dopamine, as well as glutamate and adenosine. Compared with other electrochemical techniques such as FSCV or high-speed chronoamperometry, FPA offers superior temporal resolution and, in combination with enzyme-linked biosensors, the potential to monitor nonelectroactive analytes in real time.

Methods  The WINCS design incorporated a transimpedance amplifier with associated analog circuitry for FPA; a microprocessor; a Bluetooth transceiver; and a single, battery-powered, multilayer, printed circuit board. The WINCS was tested with 3 distinct recording electrodes: 1) a carbon-fiber microelectrode (CFM) to measure dopamine; 2) a glutamate oxidase enzyme–linked electrode to measure glutamate; and 3) a multiple enzyme–linked electrode (adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase) to measure adenosine. Proof-of-principle analyses included noise assessments and in vitro and in vivo measurements that were compared with similar analyses by using a commercial hardwired electrochemical system (EA161 Picostat, eDAQ; Pty Ltd). In urethane-anesthetized rats, dopamine release was monitored in the striatum following deep brain stimulation (DBS) of ascending dopaminergic fibers in the medial forebrain bundle (MFB). In separate rat experiments, DBS-evoked adenosine release was monitored in the ventrolateral thalamus. To test the WINCS in an operating room setting resembling human neurosurgery, cortical glutamate release in response to motor cortex stimulation (MCS) was monitored using a large-mammal animal model, the pig.

Results   The WINCS, which is designed in compliance with FDA-recognized consensus standards for medical electrical device safety, successfully measured dopamine, glutamate, and adenosine, both in vitro and in vivo. The WINCS detected striatal dopamine release at the implanted CFM during DBS of the MFB. The DBS-evoked adenosine release in the rat thalamus and MCS-evoked glutamate release in the pig cortex were also successfully measured. Overall, in vitro and in vivo testing demonstrated signals comparable to a commercial hardwired electrochemical system for FPA.

Conclusions  By incorporating FPA, the chemical repertoire of WINCS-measurable neurotransmitters is expanded to include glutamate and other nonelectroactive species for which the evolving field of enzyme-linked biosensors exists. Because many neurotransmitters are not electrochemically active, FPA in combination with enzyme-linked microelectrodes represents a powerful intraoperative tool for rapid and selective neurochemical sampling in important anatomical targets during functional neurosurgery.

An ultra low power OTA with improved unity gain bandwidth product

An operational transconductance amplifier (OTA) using dynamic threshold MOS (DTMOS) and hybrid compensation technique is presented in this paper. The proposed topology is based on a bulk and gate driven input differential pair. Two separate capacitors are employed for the OTA compensation where one of them is used in a signal path and the other one in a non-signal path. The circuit is designed in the 0.18μm CMOS TSMC technology. The proposed design technique shows remarkable enhancement in unity gain-bandwidth and also in DC gain compared to the bulk driven input differential pair OTAs. The Hspice simulation results show that the amplifier has a 92dB open-loop DC gain and a unity gain-bandwidth of 135kHz while operating at 0.4V supply voltage. The total power consumption is as low as 386nW which makes it suitable for low-power bio-medical and bio-implantable applications.

Highly linear low voltage low power CMOS LNA

A highly linear, low voltage, low power, low noise amplifier (LNA) using a novel nonlinearity cancellation technique is presented in this paper. Parallel Inductor (PI) matching is used to increase LNA gain by 3dB at the desired frequency. The linear LNA was designed and simulated in a TSMC 0.18μm CMOS process at 5GHz frequency. By employing the proposed technique, the IIP3 is improved by 12dB in contrast to the conventional folded cascode LNA, reaching −1dBm without having any significant effect on the other LNA parameters such as gain, NF and also power consumption. The proposed LNA also delivers a voltage gain (S21) of 12.25dB with a noise figure of 3.5dB, while consuming only 1.28mW of DC power with a low supply voltage of 0.6V.

A new gm-boosting current reuse CMOs folded cascode LNA

In this paper, a new gain enhancement technique which is recommended for folded cascode LNA structures at low voltage and low power applications is presented. In order to increase power gain, a new modified version of gm-boosting technique is employed which increases the power gain while consuming no extra power. The new topology shares its DC current at the folded stage in order to reduce power dissipation associated with the gm-boosting technique. The proposed technique reduces power dissipation almost 27%, additionally; other parameters such as power gain and noise figure have been slightly improved. In the proposed LNA, power gain and noise figure are15dB and 3.2dB respectively. It consumes 1.3mW under 0.6 supply voltage.