A new digital predistortion (DPD) technique is presented for the linearization of RF power amplifiers (PAs) for wideband orthogonal frequency division multiplexing (OFDM) signals. The proposed DPD technique employs the phase correction term to compensate for the frequency dependent AM-PM distortion of PAs, considering the wide bandwidth of OFDM signal. The simulation shows that the proposed DPD technique can significantly improve the error vector magnitude (EVM) performance of RF PAs.
We have demonstrated terahertz (THz) passive imaging of room-temperature objects using a 4K-cryocooled THz photoconductive detector with background limited infrared performance (BLIP) at around 1.5-2.5THz. Images of a safety razor blade and a coin concealed in a plastic package or an envelope are successfully obtained with spatial resolutions of wavelength order using the THz passive imaging system. We have compared the measured THz intensity of several materials with emissivities calculated using the reported optical constants. The result shows that the THz intensity has a good linear relation to the emissivity, which means THz emissivity of an unknown material can be estimated at a room-temperature with the THz passive imaging system.
This paper presents a high-linear bootstrapped sampling switch for high-speed applications. The proposed switch utilizes bootstrapping technique of both NMOS and PMOS types simultaneously. Thus, results in a low-variation low-value on-resistance switch. Using this idea, the proposed switch considers reliability constrains, and operates in full-swing input range. Furthermore, it is suitable for standard n-well CMOS technology. Simulation results show that proposed switch achieves on-resistance variation of less than 4% through full-range input signal.
In this work, a rapid and simple approach is facilitating the design of Butler matrix beam-forming network (BMN). Generally, BMN structure is occupying huge area of printed circuit board and required large amount of mesh cells for better simulation accuracy. The proposed approach has reduced design steps and improves the simulation time. Although, designers can use better mainframe and graphics processing unit in order to improve the simulation time, the devices come with simulation cost. The entire BMN is divided into smaller and simple structure as the standard re-use electromagnetic model in order to study the parasitic elements and essential actual phase progression.
(2n-1) is one of the most commonly used moduli in Residue Number Systems. In this express, we propose a novel Booth encoding architecture. Based on the proposed Booth encoding architecture, we can design high speed and high-efficient modulo (2n-1) multipliers, which are the fastest among all known modulo (2n-1) multipliers. The performance and the efficiency of the proposed multipliers are evaluated and compared with the earlier fastest modulo (2n-1) multipliers, based on a simple gate-count and gate-delay model. These results reveal that the proposed multipliers lead to average approximately 14% faster than the fastest known modulo (2n-1) multipliers.
In this paper, an impedance change localization method for a live underground XLPE cable with a straight joint using the time-frequency domain reflectometry (TFDR) is proposed. To inject the reference signal to the live cable, an inductive coupler is used. Thus, the characteristics of the cable and the coupler are analyzed and the reference signal is designed to fit for the characteristics of the coupler and the cable. The on-voltage experiment using the TFDR is performed to localize the impedance change of cable. As a result, the accuracy of the TFDR for the on-voltage cables is proved.
A fundamental scheme, developed for implicit finite-difference time-domain methods, is utilized to reformulate the beam-propagation method based on the alternating-direction implicit scheme (ADI-BPM). A derivative-free formulation is performed in the right-hand sides of equations to be solved, leading to quite efficient implementation of the algorithm. Numerical results reveal that the computation time and memory requirements are reduced to ≅ 80%, providing the results equivalent to those of the conventional ADI-BPM.
This paper evaluates the allowable loss ranges of 1G / 10G dual-rate symmetric long-reach 10 gigabit Ethernet passive optical networks (10G-EPONs) that employ cascaded semiconductor optical amplifiers with fast automatic level controlled circuit (ALC-SOAs) for upstream transmission and a single SOA for downstream transmission. Experiments show that our optical amplifiers have the ability to achieve the maximum loss budget of 61dB with very wide loss ranges for both access and trunk spans; they support up to 80km transmission (60km trunk span and 20km access span).
It is desirable to maximize the WLAN usage in integrated heterogeneous network environment due to its high speed access and low access cost. We have modeled under geometry and mobility effects to dynamically estimate the distance of a mobile terminal from the access point at which the handover must be triggered to keep probability of handover failure within desired bounds while maximizing the WLAN usage. Monte-Carlo simulations are provided and they are in good conformance with our analytical findings.
Fundamental oscillations up to 1.08THz with the output power of 5.5 microwatts was achieved in GaInAs/AlAs resonant tunneling diodes (RTDs) at room temperature. The graded emitter, thin barriers, and high-indium-composition transit layers were introduced to reduce the tunneling and transit delays. The first two of these structures are the same as those in RTDs oscillating at 1.04THz reported recently, and the last structure provided for further reduction of the transit time and increase in frequency due to suppression of the Γ-L transition and increment of the launching velocity.
In this letter, a wideband push-push VCO using two types of phase shifters is presented. A positive feedback type push-push oscillator is used for the VCO. The phase shifters are connected in series in each feedback loop. Varactor diodes are used in the phase sifters for the frequency tuning. In the VCO, the oscillating frequency can be changed widely as much phase shift is achieved by the sum of phase shift of each phase shifter connected in series. In the experiment, the developed push-push VCO designed in K-band achieves wide tuning frequency range of 1.88GHz(relative bandwidth = 8.9%) in K-band with small variation of the output power.
The results of photon radiation testing of various microcontroller devices are described. This testing was useful to select the microcontroller in a 6DOF MEMS-based INS. This system is being developed for the in-vivo monitoring of tumour position during clinical radiotherapy treatments. This application requires a radiation-tolerant processor in order to perform appropriately in a radiotherapy environment. A phantom has been built to replicate the working conditions that the microcontroller devices are required to endure. Each time, a number of identical microcontrollers have been exposed, in turn, to X-ray doses in excess of 50Gy from a clinical radiotherapy LINAC.
Novel high-frequency bending fatigue test method for sputtered metallic thin films using PVDF microactuator is proposed. Thin film titanium specimen as an example and a PVDF piezoelectric microactuator are fabricated. The specimen is stamped on this actuator and the actuator is vibrated at its resonance frequency until the specimen fails by fatigue. The stress in the specimen is calculated from vibration amplitude. By using the proposed method, the stress-fatigue life cycle (S-N) curve of the thin film titanium is obtained over 50 times faster than conventional method.
We investigated fiber transmission characteristics of phase only pulses (POPs) that had constant intensity and pulse-shaped phase waveforms. A 10-ps-wide Gaussian-shaped POP was generated by an optical pulse synthesizer that generates arbitrary waveforms through a frequency-domain modulation. It was transmitted through a standard single mode fiber and a dispersion compensating fiber. The POP was nonlinearity-tolerant due to the constant intensity and, consequently, its initial pulse waveform was successfully regenerated by dispersion compensation even in a high power regime.
We demonstrate the electro-thermal tuning of a MEMS VCSEL with a thermally actuated SiO2/semiconductor cantilever. The wavelength-temperature dependence of the MEMS VCSEL could be increased as large as 0.46nm/K, which is 6 times larger than that of conventional single-mode lasers. A micro-heater is integrated nearby the cantilever structure. A continuous wavelength tuning range of 4.7nm is obtained with heating power of 29mW.