Compact Triple‐Band Monopole Antenna for WLAN/WiMAX‐Band USB Dongle Applications

A miniaturized triple‐band antenna suitable for wireless USB dongle applications is proposed and investigated in this paper. The presented antenna, simply consisting of a circular‐arc‐shaped stub, an L‐shaped stub, a microstrip feed line, and a rectangular ground plane has a compact size of and is capable of generating three separate resonant modes with very good impedance matching. The measurement results show that the antenna has several impedance bandwidths for of 260 MHz (2.24 GHz to 2.5 GHz), 320 MHz (3.4 GHz to 3.72 GHz), and 990 MHz (5.1 GHz to 6.09 GHz), which can be applied to both 2.4/5.2/5.8 GHz WLAN bands and 3.5/5.5 GHz WiMAX bands. Moreover, nearly‐omni‐directional radiation patterns and stable gain across the operating bands can be obtained.     

Adaptive Calibration Method in Multiport Amplifier for K‐Band Payload Applications

This letter proposes a novel calibration method for a multiport amplifier (MPA) to achieve optimum port‐to‐port isolation by correcting both the amplitude and phase of the calibration signals. The proposed architecture allows for the detection of the phase error and amplitude error in each RF signal path simultaneously and can enhance the calibrated resolution by controlling the analog phase shifters and attenuators. The designed and MPAs show isolation characteristics of 30 dB and 27 dB over a frequency range of 19.5 GHz to 22.5 GHz, respectively.     

Stopband‐Extended and Size‐Miniaturized Low‐Pass Filter with Three Transmission Zeros

This paper presents a compact structure composed of an upper high‐impedance transmission line, a middle extended parallel coupled line, and a pair of inter‐coupled symmetrical stepped impedance stubs. Detailed investigation into this structure based on an equivalent circuit analysis reveals that this proposed structure exhibits a quasi‐elliptic low‐pass filtering response with three transmission zeros. Moreover, the positions of the three transmission zeros can be tuned and reallocated flexibly by choosing the proper circuit parameters. Finally, the design concept is validated through the design, fabrication, and measurement of two exemplary low‐pass filters (LPFs) with one single unit and two cascaded asymmetric units. The measured results agree well with the simulated results. In addition, in the range of 1.42 f_c to 7.03 f_c, the fabricated quasi‐elliptic LPFs experimentally demonstrate a very wide upper‐stopband of 20 dB using a compact size of only , where λ_g is the guided wavelength of a 50 Ω transmission line at the central frequency.     

Cost Effective Silica‐Based 100 G DP‐QPSK Coherent Receiver

We present a cost‐effective dual polarization quadrature phase‐shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two 90° optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of 2%‐Δ. Two four‐channel spot‐size converter integrated waveguide‐photodetector (PD) arrays are bonded on PD carriers for transverse‐electric/transverse‐magnetic polarization, and butt‐coupled to a polished facet of the PLC using a simple chip‐to‐chip bonding method. Instead of a ceramic sub‐mount, a low‐cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans‐impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3‐dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of is achieved at a 112‐Gbps back‐to‐back transmission with off‐line digital signal processing.     

Mixed‐Domain Adaptive Blind Correction of High‐Resolution Time‐Interleaved ADCs

Blind mismatch correction of time‐interleaved analog‐to‐digital converters (TI‐ADC) is a challenging task. We present a practical blind calibration technique for low‐computation, low‐complexity, and high‐resolution applications. Its key features are: dramatically reduced computation; simple hardware; guaranteed parameter convergence with an arbitrary number of TI‐ADC channels and most real‐life input signals, with no bandwidth limitation; multiple Nyquist zone operation; and mixed‐domain error correction. The proposed technique is experimentally verified by an 400 MSPS TI‐ADC system. In a single‐tone test, the proposed practical blind calibration technique suppressed mismatch spurs by 70 dB to 90 dB below the signal tone across the first two Nyquist zones (10 MHz to 390 MHz). A wideband signal test also confirms the proposed technique.     

Design and Experiment Results of High‐Speed Wireless Link Using Sub‐terahertz Wave Generated by Photonics‐Based Technology

Using a sub‐terahertz (sub‐THz) wave generated using a photonics‐based technology, a high‐speed wireless link operating at up to 10 Gbps is designed and demonstrated for realization of seamless connectivity between wireless and wired networks. The sub‐THz region is focused upon because of the possibility to obtain sufficient bandwidth without interference with the allocated RF bands. To verify the high‐speed wireless link, such dynamic characteristics as the eye diagrams and bit error rate (BER) are measured at up to 10 Gbps for non‐return‐to‐zero pseudorandom binary sequence data. From the measurement results, a receiver sensitivity of –23.5 dBm at is observed without any error corrections when the link distance between the transmitter and receiver is 3 m. Consequently, we hope that our design and experiment results will be helpful in implementing a high‐speed wireless link using a sub‐THz wave.     

Design Space Exploration for NoC‐Style Bus Networks

With the number of IP cores in a multicore system‐on‐chip increasing to up to tens or hundreds, the role of on‐chip interconnection networks is vital. We propose a networks‐on‐chip‐style bus network as a compromise and redefine the exploration problem to find the best IP tiling patterns and communication path combinations. Before solving the problem, we estimate the time complexity and validate the infeasibility of the solution. To reduce the time complexity, we propose two fast exploration algorithms and develop a program to implement these algorithms. The program is executed for several experiments, and the exploration time is reduced to approximately 1/22 and 7/1,200 at the first and second steps of the exploration process, respectively. However, as a trade‐off for the time saving, the time cost (TC) of the searched architecture is increased to up to and , respectively, at each step compared with that of the architecture obtained through full‐case exploration. The reduction ratio can be decreased to 1/4,000 by simultaneously applying both the algorithms even though the resulting TC is increased to up to when compared with that obtained through full‐case exploration.     

Highly Simplified and Bandwidth‐Efficient Human Body Communications Based on IEEE 802.15.6 WBAN Standard

This paper presents a transmission method for improving human body communications in terms of spectral efficiency, and the performances of bit‐error‐rate (BER) and frame synchronization, with a highly simplified structure. Compared to the conventional frequency selective digital transmission supporting IEEE standard 802.15.6 for wireless body area networks, the proposed scheme improves the spectral efficiency from 0.25 bps/Hz to 1 bps/Hz based on the 3‐dB bandwidth of the transmit spectral mask, and the signal‐to‐noise‐ratio (SNR) by 0.51 dB at a BER of with an reduction in the detection complexity of the length of the Hamming distance computation. The proposed preamble structure using its customized detection algorithm achieves perfect frame synchronization at the SNR of a BER of by applying the proposed pre‐processing to compensate for the distortions on the preamble signals due to the band‐limit effects by transmit and receive filters.     

New Time‐Domain Decoder for Correcting both Errors and Erasures of Reed‐Solomon Codes

A new time‐domain decoder for Reed‐Solomon (RS) codes is proposed. Because this decoder can correct both errors and erasures without computing the erasure locator, errata locator, or errata evaluator polynomials, the computational complexity can be substantially reduced. Herein, to demonstrate this benefit, complexity comparisons between the proposed decoder and the Truong‐Jeng‐Hung and Lin‐Costello decoders are presented. These comparisons show that the proposed decoder consistently has lower computational requirements when correcting all combinations of ν errors and μ erasures than both of the related decoders under the condition of , where d_min denotes the minimum distance of the RS code. Finally, the (255, 223) and (63, 39) RS codes are used as examples for complexity comparisons under the upper bounded condition of . To decode the two RS codes, the new decoder can save about 40% additions and multiplications when as compared with the two related decoders. Furthermore, it can also save 50% of the required inverses for .     

Low‐Power Channel‐Adaptive Reconfigurable 4×4 QRM‐MLD MIMO Detector

This paper presents a low‐complexity channel‐adaptive reconfigurable QR‐decomposition and M‐algorithm‐based maximum likelihood detection (QRM‐MLD) multiple‐input and multiple‐output (MIMO) detector. Two novel design approaches for low‐power QRM‐MLD hardware are proposed in this work. First, an approximate survivor metric (ASM) generation technique is presented to achieve considerable computational complexity reduction with minor BER degradation. A reconfigurable QRM‐MLD MIMO detector (where the M‐value represents the number of survival branches in a stage) for dynamically adapting to time‐varying channels is also proposed in this work. The proposed reconfigurable QRM‐MLD MIMO detector is implemented using a Samsung 65 nm CMOS process. The experimental results show that our ASM‐based QRM‐MLD MIMO detector shows a maximum throughput of 288 Mbps with a normalized power efficiency of 10.18 Mbps/mW in the case of MIMO with 64‐QAM. Under time‐varying channel conditions, the proposed reconfigurable MIMO detector also achieves average power savings of up to 35% while maintaining a required BER performance.     

Generation and Detection of Terahertz Waves Using Low‐Temperature‐Grown GaAs with an Annealing Process

In this letter, we present low‐temperature grown GaAs (LTG‐GaAs)‐based photoconductive antennas for the generation and detection of terahertz (THz) waves. The growth of LTG‐GaAs and the annealing temperatures are systematically discussed based on the material characteristics and the properties of THz emission and detection. The optimum annealing temperature depends on the growth temperature, which turns out to be 540°C to 580°C for the initial excess arsenic density of to .     

Microstrip Lowpass Filter with Very SharpTransition Band Using T‐Shaped,Patch, and Stepped Impedance Resonators

A compact microstrip lowpass filter (LPF) with an elliptic function response is proposed. A high equivalent capacitance and inductance between the structures of the resonator result in the sharp transition band of 0.04 GHz from 4 GHz to 4.04 GHz with an attenuation level of ?3 dB and ?20 dB, respectively. To improve the LPF rejection band, multiple open stubs are connected to the proposed resonator. A filter with a 3‐dB cut‐off frequency at 4 GHz is designed, fabricated, and measured, and agreement between the measured and simulated results is achieved. The results show that a stopband bandwidth of 131% with a suppression level better than ?20 dB is obtained while achieving a compact size with a wide stopband.     

Implementation of Real‐Time Post‐Processing for High‐Quality Stereo Vision

We propose a novel post‐processing algorithm and its very‐large‐scale integration architecture that simultaneously uses the passive and active stereo vision information to improve the reliability of the three‐dimensional disparity in a hybrid stereo vision system. The proposed architecture consists of four steps — left‐right consistency checking, semi‐2D hole filling, a tiny adaptive variance checking, and a 2D weighted median filter. The experimental results show that the error rate of the proposed algorithm (5.77%) is less than that of a raw disparity (10.12%) for a real‐world camera image having a resolution and maximum disparity of 256. Moreover, for the famous Middlebury stereo image sets, the proposed algorithm's error rate (8.30%) is also less than that of the raw disparity (13.7%). The proposed architecture is implemented on a single commercial field‐programmable gate array using only 13.01% of slice resources, which achieves a rate of 60 fps for stereo images with a disparity range of 256.     

A Transparent Logic Circuit for RFID Tag in a‐IGZO TFT Technology

This paper proposes a transparent logic circuit for radio frequency identification (RFID) tags in amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) thin‐film transistor (TFT) technology. The RFID logic circuit generates 16‐bit code programmed in read‐only memory. All circuits are implemented in a pseudo‐CMOS logic style using transparent a‐IGZO TFTs. The transmittance degradation due to the transparent RFID logic chip is 2.5% to 8% in a 300‐nm to 800‐nm wavelength. The RFID logic chip generates Manchester‐encoded 16‐bit data with a 3.2‐kHz clock frequency and consumes 170 μW at . It employs 222 transistors and occupies a chip area of 5.85 mm².     

Supercapacitive Properties of Composite Electrode Consisting of Activated Carbon and Di(1‐aminopyrene)quinone

Di(1‐aminopyrene)quinone (DAQ) as a quinone‐containing conducting additive is synthesized from a solution reaction of 1‐aminopyrene and hydroquinone. To utilize the conductive property of DAQ and its compatibility with activated carbon, a composite electrode for a supercapacitor is also prepared by blending activated carbon and DAQ (3:1 w/w), and its supercapacitive properties are characterized based on the cyclic voltammetry and galvanostatic charge/discharge. As a result, the composite electrode adopting DAQ exhibits superior electrochemical properties, such as a higher specific capacitance of up to at , an excellent high‐rate capability of up to , and a higher cycling stability with a capacitance retention ratio of 82% for the 1,000th cycle.     

Transparent OLED Lighting Panel Design Using Two‐Dimensional OLED Circuit Modeling

In this work, we develop a simulation method to predict a two‐dimensional luminance distribution method using a circuitry simulation. Based on the simulation results, we successfully fabricate large area transparent organic light‐emitting diode panels with high luminance uniformity.     

Pseudo Optical PAM‐N Signal Using Externally Modulated Lasers

We propose a pseudo optical N‐level pulse‐amplitude modulation (PO PAM‐N) signal using a few externally‐modulated lasers (EMLs) operating at different wavelengths, which is suitable for upgrading the transmission speed over an optical link of ＜ 10 km single‐mode fiber with low‐cost components. To compare a PO PAM‐N signal with that of a standard optical PAM‐N signal, we perform experiments for evaluating the performance of a 51.56‐Gb/s PO PAM‐4 signal and standard 51.56‐Gb/s optical PAM‐4 signal. The receiver sensitivity (at ) of the PO PAM‐4 signal is 1.5 dB better than the receiver sensitivity of a standard optical PAM‐4 signal. We also investigate the feasibility of PO PAM‐N signals operating at 103.12 Gb/s, considering relative intensity noise, timing jitter, extinction ratio (ER) of EMLs, and dispersion. From the results, a PO PAM‐8 signal performs better than PO PAM‐4 and PO PAM‐16 signals at 103.12 Gb/s. Finally, we suggest a timing control method to suppress the effect of dispersion in a PO PAM‐N signal. We show that the tolerance to dispersion of a 103.12‐Gb/s PO PAM‐8 signal can be improved to ±40 ps/nm by applying a proposed scheme.     

Microwave Orbital Angular Momentum Mode Generation and Multiplexing Using a Waveguide Butler Matrix

In this paper, we propose a convenient microwave orbital angular momentum (OAM) mode generation and multiplexing method operating in the 18 GHz frequency band, based on a uniform circular array and a Butler matrix. The three OAM modes ?1, 0, and +1 were generated and verified using spatial S‐parameter measurements; the measured back‐to‐back mode isolation was greater than 17 dB in the full 17 GHz to 19 GHz range. However, the radiated OAM beam centers were slightly dislocated and varied with both frequency and the mode index, because of the non‐ideal characteristics of the Butler matrix. This resulted in mode isolation degradation and transmission distance limitations.     

Design of Multi‐time Programmable Memory for PMICs

In this paper, a multi‐time programmable (MTP) cell based on a 0.18 μm bipolar‐CMOS‐DMOS backbone process that can be written into by using dual pumping voltages — VPP (boosted voltage) and VNN (negative voltage) — is used to design MTP memories without high voltage devices. The used MTP cell consists of a control gate (CG) capacitor, a TG_SENSE transistor, and a select transistor. To reduce the MTP cell size, the tunnel gate (TG) oxide and sense transistor are merged into a single TG_SENSE transistor; only two p‐wells are used — one for the TG_SENSE and sense transistors and the other for the CG capacitor; moreover, only one deep n‐well is used for the 256‐bit MTP cell array. In addition, a three‐stage voltage level translator, a VNN charge pump, and a VNN precharge circuit are newly proposed to secure the reliability of 5 V devices. Also, a dual memory structure, which is separated into a designer memory area of and a user memory area of , is newly proposed in this paper.     

Simplified Bilayer White Phosphorescent Organic Light‐Emitting Diodes

We report on highly efficient blue, orange, and white phosphorescent organic light‐emitting diodes consisting only two organic layers. Hole transporting 4, 4,’ 4”‐tris (N‐carbazolyl)triphenylamine (TcTa) and electron transporting 2‐(diphenylphosphoryl) spirofluorene (SPPO1) are used as an emitting host for orange light‐emitting bis(3‐benzothiazol‐2‐yl‐9‐ethyl‐9H‐carbazolato) (acetoacetonate) iridium ((btc)2(acac)Ir) and blue light‐emitting iridium(III)bis(4,6‐difluorophenyl‐pyridinato‐N,C2’) picolinate (FIrpic) dopant, respectively. Combining these two orange and blue light‐emitting layers, we successfully demonstrate highly efficient white PHOLEDs while maintaining Commission internationale de l'éclairage coordinates of (, ). Accordingly, we achieve a maximum external quantum, current, and power efficiencies of 12.9%, 30.3 cd/A, and 30.0 lm/W without out‐coupling enhancement.