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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
Electronics and Telecommunications Research Institute
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Volume & Issues
Volume 35, Issue 6 - Dec 2013
Volume 35, Issue 5 - Oct 2013
Volume 35, Issue 4 - Aug 2013
Volume 35, Issue 3 - Jun 2013
Volume 35, Issue 2 - Apr 2013
Volume 35, Issue 1 - Feb 2013
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Packet-Reduced Ranging Method with Superresolution TOA Estimation Algorithm for Chirp-Based RTLS
Oh, Daegun ; Go, Seungryeol ; Chong, Jong-Wha ;
ETRI Journal, volume 35, issue 3, 2013, Pages 361~370
DOI : 10.4218/etrij.13.0112.0678
In this paper, a packet-reduced ranging method using a superresolution time of arrival estimation algorithm for a chirp-based real-time locating system is presented. A variety of ranging methods, such as symmetric double-sided two-way ranging (SDS-TWR), have been proposed to remove the time drift due to the frequency offset using extra ranging packets. Our proposed method can perform robust ranging against the frequency offset using only two ranging packets while maintaining almost the same ranging accuracy as them. To verify the effectiveness of our proposed algorithm, the error performance of our proposed ranging method is analyzed and compared with others. The total ranging performance of TWR, SDS-TWR, and our proposed TWR are analyzed and verified through simulations in additive white Gaussian noise and multipath channels in the presence of the frequency offset.
Combined ML and QR Detection Algorithm for MIMO-OFDM Systems with Perfect ChanneI State Information
You, Weizhi ; Yi, Lilin ; Hu, Weisheng ;
ETRI Journal, volume 35, issue 3, 2013, Pages 371~377
DOI : 10.4218/etrij.13.0112.0633
An effective signal detection algorithm with low complexity is presented for multiple-input multiple-output orthogonal frequency division multiplexing systems. The proposed technique, QR-MLD, combines the conventional maximum likelihood detection (MLD) algorithm and the QR algorithm, resulting in much lower complexity compared to MLD. The proposed technique is compared with a similar algorithm, showing that the complexity of the proposed technique with T=1 is a 95% improvement over that of MLD, at the expense of about a 2-dB signal-to-noise-ratio (SNR) degradation for a bit error rate (BER) of
. Additionally, with T=2, the proposed technique reduces the complexity by 73% for multiplications and 80% for additions and enhances the SNR performance about 1 dB for a BER of
An S-Band Multifunction Chip with a Simple Interface for Active Phased Array Base Station Antennas
Jeong, Jin-Cheol ; Shin, Donghwan ; Ju, Inkwon ; Yom, In-Bok ;
ETRI Journal, volume 35, issue 3, 2013, Pages 378~385
DOI : 10.4218/etrij.13.0112.0400
An S-band multifunction chip with a simple interface for an active phased array base station antenna for next-generation mobile communications is designed and fabricated using commercial 0.5-
GaAs pHEMT technology. To reduce the cost of the module assembly and to reduce the number of chip interfaces for a compact transmit/receive module, a digital serial-to-parallel converter and an active bias circuit are integrated into the designed chip. The chip can be controlled and driven using only five interfaces. With 6-bit phase shifting and 6-bit attenuation, it provides a wideband performance employing a shunt-feedback technique for amplifiers. With a compact size of 16
), the proposed chip exhibits a gain of 26 dB, a P1dB of 12 dBm, and a noise figure of 3.5 dB over a wide frequency range of 1.8 GHz to 3.2 GHz.
10-Gbit/s Wireless Communication System at 300 GHz
Chung, Tae Jin ; Lee, Won-Hui ;
ETRI Journal, volume 35, issue 3, 2013, Pages 386~396
DOI : 10.4218/etrij.13.0112.0351
A 10-Gbit/s wireless communication system operating at a carrier frequency of 300 GHz is presented. The modulation scheme is amplitude shift keying in incoherent mode with a high intermediate frequency (IF) of 30 GHz and a bandwidth of 20 GHz for transmitting a 10-Gbit/s baseband (BB) data signal. A single sideband transmission is implemented using a waveguide-tapered 270-GHz high-pass filter with a lower sideband rejection of around 60 dB. This paper presents an all-electronic design of a terahertz communication system, including the major modules of the BB and IF band as well as the RF modules. The wireless link shows that, aided by a clock and data recovery circuit, it can receive
-1 pseudorandom binary sequence data without error at up to 10 Gbit/s for over 1.2 m using collimating lenses, where the transmitted power is 10
Novel Spectrally Efficient UWB Pulses Using Zinc and Frequency-Domain Walsh Basis Functions
Chaurasiya, Praveen ; Ashrafi, Ashkan ; Nagaraj, Santosh ;
ETRI Journal, volume 35, issue 3, 2013, Pages 397~405
DOI : 10.4218/etrij.13.0112.0315
In this paper, two sets of spectrally efficient ultra-wideband (UWB) pulses using zinc and frequency-domain Walsh basis functions are proposed. These signals comply with the Federal Communications Commission (FCC) regulations for UWB indoor communications within the stipulated bandwidth of 3.1 GHz to 10.6 GHz. They also demonstrate high energy spectral efficiency by conforming more closely to the FCC mask than other UWB signals described in the literature. The performance of these pulses under various modulation techniques is discussed in this paper, and the proposed pulses are compared with Gaussian monocycles in terms of spectral efficiency, autocorrelation, crosscorrelation, and bit error rate performance.
Distributed Routing Based on Minimum End-to-End Delay for OFDMA Backhaul Mobile Mesh Networks
Chung, Jong-Moon ; Lee, Daeyoung ; Park, Jong-Hong ; Lim, Kwangjae ; Kim, HyunJae ; Kwon, Dong-Seung ;
ETRI Journal, volume 35, issue 3, 2013, Pages 406~413
DOI : 10.4218/etrij.13.0112.0450
In this paper, an orthogonal frequency division multiple access (OFDMA)-based minimum end-to-end delay (MED) distributed routing scheme for mobile backhaul wireless mesh networks is proposed. The proposed scheme selects routing paths based on OFDMA subcarrier synchronization control, subcarrier availability, and delay. In the proposed scheme, OFDMA is used to transmit frames between mesh routers using type-I hybrid automatic repeat request over multipath Rayleigh fading channels. Compared with other distributed routing algorithms, such as most forward within radius R, farthest neighbor routing, nearest neighbor routing, and nearest with forwarding progress, simulation results show that the proposed MED routing can reduce end-to-end delay and support highly reliable routing using only local information of neighbor nodes.
Bio-inspired Load Balancing Routing for Delay-Guaranteed Services in Ever-Changing Networks
Kim, Young-Min ; Kim, Hak Suh ; Jung, Boo-Geum ; Park, Hea-Sook ; Park, Hong-Shik ;
ETRI Journal, volume 35, issue 3, 2013, Pages 414~424
DOI : 10.4218/etrij.13.1812.0114
We consider a new load balancing routing for delay-guaranteed services in the network in which the traffic is dynamic and network topologies frequently change. For such an ever-changing network, we propose a new online load balancing routing called AntLBR, which exploits the ant colony optimization method. Generally, to achieve load balancing, researchers have tried to calculate the traffic split ratio by solving a complicated linear programming (LP) problem under the static network environment. In contrast, the proposed AntLBR does not make any attempt to solve this complicated LP problem. So as to achieve load balancing, AntLBR simply forwards incoming flows by referring to the amount of pheromone trails. Simulation results indicate that the AntLBR algorithm achieves a more load-balanced network under the changing network environment than techniques used in previous research while guaranteeing the requirements of delay-guaranteed services.
Electrical Characteristics of Triple-Gate RSO Power MOSFET (TGRMOS) with Various Gate Configurations and Bias Conditions
Na, Kyoung Il ; Won, Jongil ; Koo, Jin-Gun ; Kim, Sang Gi ; Kim, Jongdae ; Yang, Yil Suk ; Lee, Jin Ho ;
ETRI Journal, volume 35, issue 3, 2013, Pages 425~430
DOI : 10.4218/etrij.13.0112.0246
In this paper, we propose a triple-gate trench power MOSFET (TGRMOS) that is made through a modified RESURF stepped oxide (RSO) process, that is, the nitride_RSO process. The electrical characteristics of TGRMOSs, such as the blocking voltage (
) and on-state current (
), are strongly dependent on the gate configuration and its bias condition. In the nitride_RSO process, the thick single insulation layer (
) of a conventional RSO power MOSFET is changed to a multilayered insulator (
). The inserted
layer can create the selective etching of the TEOS layer between the gate oxide and poly-Si layers. After additional oxidation and the poly-Si filling processes, the gates are automatically separated into three parts. Moreover, to confirm the variation in the electrical properties of TGRMOSs, such as
, simulation studies are performed on the function of the gate configurations and their bias conditions.
are controlled from 87 V to 152 V and from 0.14 mA to 0.24 mA at a 15-V gate voltage. This
variation indicates the specific on-resistance modulation.
RMS Detector of Multiharmonic Signals
Petrovic, Predrag B. ;
ETRI Journal, volume 35, issue 3, 2013, Pages 431~438
DOI : 10.4218/etrij.13.0112.0433
This paper presents a new realization of the implicit root-mean-square (RMS) detector, employing three second-generation current conveyors and MOS transistors. The proposed circuit can be applied in measuring the RMS value of complex, periodic signals, represented in the form of the Fourier series. To verify the theoretical analysis, circuit Simulation Program with Integrated Circuit Emphasis simulations and experiment results are included, showing agreement with the theory.
A Very Efficient Redundancy Analysis Method Using Fault Grouping
Cho, Hyungjun ; Kang, Wooheon ; Kang, Sungho ;
ETRI Journal, volume 35, issue 3, 2013, Pages 439~447
DOI : 10.4218/etrij.13.0112.0467
To increase device memory yield, many manufacturers use incorporated redundancy to replace faulty cells. In this redundancy technology, the implementation of an effective redundancy analysis (RA) algorithm is essential. Various RA algorithms have been developed to repair faults in memory. However, nearly all of these RA algorithms have low analysis speeds. The more densely compacted the memory is, the more testing and repair time is needed. Even if the analysis speed is very high, the RA algorithm would be useless if it did not have a normalized repair rate of 100%. In addition, when the number of added spares is increased in the memory, then the memory space that must be searched with the RA algorithms can exceed the memory space within the automatic test equipment. A very efficient RA algorithm using simple calculations is proposed in this work so as to minimize both the repair time and memory consumption. In addition, the proposed algorithm generates an optimal solution using a tree-based algorithm in each fault group. Our experiment results show that the proposed RA algorithm is very efficient in terms of speed and repair.
Generalized Hardware Post-processing Technique for Chaos-Based Pseudorandom Number Generators
Barakat, Mohamed L. ; Mansingka, Abhinav S. ; Radwan, Ahmed G. ; Salama, Khaled N. ;
ETRI Journal, volume 35, issue 3, 2013, Pages 448~458
DOI : 10.4218/etrij.13.0112.0677
This paper presents a generalized post-processing technique for enhancing the pseudorandomness of digital chaotic oscillators through a nonlinear XOR-based operation with rotation and feedback. The technique allows full utilization of the chaotic output as pseudorandom number generators and improves throughput without a significant area penalty. Digital design of a third-order chaotic system with maximum function nonlinearity is presented with verified chaotic dynamics. The proposed post-processing technique eliminates statistical degradation in all output bits, thus maximizing throughput compared to other processing techniques. Furthermore, the technique is applied to several fully digital chaotic oscillators with performance surpassing previously reported systems in the literature. The enhancement in the randomness is further examined in a simple image encryption application resulting in a better security performance. The system is verified through experiment on a Xilinx Virtex 4 FPGA with throughput up to 15.44 Gbit/s and logic utilization less than 0.84% for 32-bit implementations.
Proposal and Analysis of Distributed Reflector-Laser Diode Integrated with an Electroabsorption Modulator
Kwon, Oh Kee ; Beak, Yong Soon ; Chung, Yun C. ; Park, Hyung-Moo ;
ETRI Journal, volume 35, issue 3, 2013, Pages 459~468
DOI : 10.4218/etrij.13.0112.0305
A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single-mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time-domain transfer-matrix-based laser model is developed. Based on this model, we perform steady-state and large-signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10-Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.
Computation Controllable Mode Decision and Motion Estimation for Scalable Video Coding
Zheng, Liang-Wei ; Li, Gwo-Long ; Chen, Mei-Juan ; Yeh, Chia-Hung ; Tai, Kuang-Han ; Wu, Jian-Sheng ;
ETRI Journal, volume 35, issue 3, 2013, Pages 469~479
DOI : 10.4218/etrij.13.0112.0421
This paper proposes an efficient computation-aware mode decision and search point (SP) allocation algorithm for spatial and quality scalabilities in Scalable Video Coding. In our proposal, a linear model is derived to allocate the computation for macroblocks in enhancement layers by using the rate distortion costs of the base layer. In addition, an adaptive SP decision algorithm is proposed to decide the number of SPs for motion estimation under the constraint of the allocated computation. Experiment results demonstrate that the proposed algorithm allocates the computation resource efficiently and outperforms other works in rate distortion performance under the same computational availability constraint.
Architectural Design Issues in a Clockless 32-Bit Processor Using an Asynchronous HDL
Oh, Myeong-Hoon ; Kim, Young Woo ; Kwak, Sanghoon ; Shin, Chi-Hoon ; Kim, Sung-Nam ;
ETRI Journal, volume 35, issue 3, 2013, Pages 480~490
DOI : 10.4218/etrij.13.0112.0598
As technology evolves into the deep submicron level, synchronous circuit designs based on a single global clock have incurred problems in such areas as timing closure and power consumption. An asynchronous circuit design methodology is one of the strong candidates to solve such problems. To verify the feasibility and efficiency of a large-scale asynchronous circuit, we design a fully clockless 32-bit processor. We model the processor using an asynchronous HDL and synthesize it using a tool specialized for asynchronous circuits with a top-down design approach. In this paper, two microarchitectures, basic and enhanced, are explored. The results from a pre-layout simulation utilizing 0.13-
CMOS technology show that the performance and power consumption of the enhanced microarchitecture are respectively improved by 109% and 30% with respect to the basic architecture. Furthermore, the measured power efficiency is about 238
/MHz and is comparable to that of a synchronous counterpart.
Best Combination of Binarization Methods for License Plate Character Segmentation
Yoon, Youngwoo ; Ban, Kyu-Dae ; Yoon, Hosub ; Lee, Jaeyeon ; Kim, Jaehong ;
ETRI Journal, volume 35, issue 3, 2013, Pages 491~500
DOI : 10.4218/etrij.13.0112.0545
A connected component analysis from a binary image is a popular character segmentation method but occasionally fails to segment the characters owing to image noise and uneven illumination. A multimethod binarization scheme that incorporates two or more binary images is a novel solution, but selection of binarization methods has never been analyzed before. This paper reveals the best combination of binarization methods and parameters and presents an in-depth analysis of the multimethod binarization scheme for better character segmentation. We carry out an extensive quantitative evaluation, which shows a significant improvement over conventional single-method binarization methods. Experiment results of six binarization methods and their combinations with different test images are presented.
Preserving User Anonymity in Context-Aware Location-Based Services: A Proposed Framework
Teerakanok, Songpon ; Vorakulpipat, Chalee ; Kamolphiwong, Sinchai ; Siwamogsatham, Siwaruk ;
ETRI Journal, volume 35, issue 3, 2013, Pages 501~511
DOI : 10.4218/etrij.13.0112.0327
Protecting privacy is an important goal in designing location-based services. Service providers want to verify legitimate users and allow permitted users to enjoy their services. Users, however, want to preserve their privacy and prevent tracking. In this paper, a new framework providing users with more privacy and anonymity in both the authentication process and the querying process is proposed. Unlike the designs proposed in previous works, our framework benefits from a combination of three important techniques: k-anonymity, timed fuzzy logic, and a one-way hash function. Modifying and adapting these existing schemes provides us with a simpler, less complex, yet more mature solution. During authentication, the one-way hash function provides users with more privacy by using fingerprints of users' identities. To provide anonymous authentication, the concept of confidence level is adopted with timed fuzzy logic. Regarding location privacy, spatial k-anonymity prevents the users' locations from being tracked. The experiment results and analysis show that our framework can strengthen the protection of anonymity and privacy of users by incurring a minimal implementation cost and can improve functionality.
Robust Watermarking Scheme Based on Radius Weight Mean and Feature-Embedding Technique
Yang, Ching-Yu ;
ETRI Journal, volume 35, issue 3, 2013, Pages 512~522
DOI : 10.4218/etrij.13.0112.0480
In this paper, the radius weight mean (RWM) and the feature-embedding technique are used to present a novel watermarking scheme for color images. Simulations validate that the stego-images generated by the proposed scheme are robust against most common image-processing operations, such as compression, color quantization, bit truncation, noise addition, cropping, blurring, mosaicking, zigzagging, inversion, (edge) sharpening, and so on. The proposed method possesses outstanding performance in resisting high compression ratio attacks: JPEG2000 and JPEG. Further, to provide extra hiding storage, a steganographic method using the RWM with the least significant bit substitution technique is suggested. Experiment results indicate that the resulting perceived quality is desirable, whereas the peak signal-to-noise ratio is high. The payload generated using the proposed method is also superior to that generated by existing approaches.
Subquadratic Space Complexity Multiplier for GF(
) Using Type 4 Gaussian Normal Bases
Park, Sun-Mi ; Hong, Dowon ; Seo, Changho ;
ETRI Journal, volume 35, issue 3, 2013, Pages 523~529
DOI : 10.4218/etrij.13.0112.0596
Subquadratic space complexity multipliers for optimal normal bases (ONBs) have been proposed for practical applications. However, for the Gaussian normal basis (GNB) of type t > 2 as well as the normal basis (NB), there is no known subquadratic space complexity multiplier. In this paper, we propose the first subquadratic space complexity multipliers for the type 4 GNB. The idea is based on the fact that the finite field GF(
) with the type 4 GNB can be embedded into fields with an ONB.
Miniaturization of Dual-Band PIFA for Wireless LAN Communication
Liu, Yang ; Lee, Jaeseok ; Jeon, Sinhyung ; Jung, Kyung-Young ; Kim, Hyunghoon ; Kim, Hyeongdong ;
ETRI Journal, volume 35, issue 3, 2013, Pages 530~533
DOI : 10.4218/etrij.13.0212.0436
In this letter, a simple method for reducing the size of a dual-band planar inverted-F antenna (PIFA) is described. This method is based on a coupling capacitor connected in parallel to the PIFA feed conductor. The proposed antenna occupies a small ground clearance of
and is able to provide -10-dB impedance bandwidths of 120 MHz and 760 MHz for 2.45-GHz and 5.5-GHz wireless local area network applications, respectively. The measured antenna efficiencies are 71.8% and 73.6%, averaged over the 2.45-GHz and 5.5-GHz frequency bands, respectively.
Compact Folded Monopole Antenna Excited by a Conductor-Backed Coplanar Waveguide with Vias
Kim, Jin Hyuk ; Hwang, Keum Cheol ;
ETRI Journal, volume 35, issue 3, 2013, Pages 534~537
DOI : 10.4218/etrij.13.0212.0485
A compact monopole antenna excited by a conductor-backed coplanar waveguide (CBCPW) is developed for wireless USB dongle applications. The proposed antenna has a compact dimension of
, which is suitable for a USB dongle housing. A slotted elliptical patch and a CBCPW with vertical vias are employed to achieve a further size reduction and an improved impedance bandwidth. The measurement result demonstrates that the fabricated antenna resonates from 2.25 GHz to 10.9 GHz, which covers all of the important wireless communication bands, including WiBro (2.3 GHz to 2.4 GHz), Bluetooth (2.4 GHz to 2.484 GHz), WiMAX (2.5 GHz to 2.7 GHz and 3.4 GHz to 3.6 GHz), satellite DMB (2.605 GHz to 2.655 GHz), 802.11b/g/a WLAN (2.4 GHz to 2.485 GHz and 5.15 GHz to 5.825 GHz), and ultra-wideband (3.1 GHz to 10.6 GHz) services. The radiation characteristics of the proposed antenna when attached to a laptop are tested to investigate the influence of the keypad and the LCD panel of the laptop.
Microstrip Lowpass Filter with Very SharpTransition Band Using T-Shaped, Patch, and Stepped Impedance Resonators
Hayati, Mohsen ; Sheikhi, Akram ;
ETRI Journal, volume 35, issue 3, 2013, Pages 538~541
DOI : 10.4218/etrij.13.0212.0307
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.
Transform Coding Based on Source Filter Model in the MDCT Domain
Sung, Jongmo ; Ko, Yun-Ho ;
ETRI Journal, volume 35, issue 3, 2013, Pages 542~545
DOI : 10.4218/etrij.13.0212.0368
State-of-the-art voice codecs have been developed to extend the input bandwidth to enhance quality while maintaining interoperability with a legacy codec. Most of them employ a modified discrete cosine transform (MDCT) for coding their extended band. We propose a source filter model-based coding algorithm of MDCT spectral coefficients, apply it to the ITU-T G.711.1 super wideband (SWB) extension codec, and subjectively test it to validate the model. A subjective test shows a better quality over the standardized SWB codec.
A Ka-Band 6-W High Power MMIC Amplifier with High Linearity for VSAT Applications
Jeong, Jin-Cheol ; Jang, Dong-Pil ; Yom, In-Bok ;
ETRI Journal, volume 35, issue 3, 2013, Pages 546~549
DOI : 10.4218/etrij.13.0212.0407
A Ka-band 6-W high power microwave monolithic integrated circuit amplifier for use in a very small aperture terminal system requiring high linearity is designed and fabricated using commercial 0.15-
GaAs pHEMT technology. This three-stage amplifier, with a chip size of 22.1
can achieve a saturated output power of 6 W with a 21% power-added efficiency and 15-dB small signal gain over a frequency range of 28.5 GHz to 30.5 GHz. To obtain high linearity, the amplifier employs a class-A bias and demonstrates an output third-order intercept point of greater than 43.5 dBm over the above-mentioned frequency range.
Joint Optimization for Congestion Avoidance in Cognitive Radio WMNs under SINR Model
Jia, Jie ; Lin, Qiusi ; Chen, Jian ; Wang, Xingwei ;
ETRI Journal, volume 35, issue 3, 2013, Pages 550~553
DOI : 10.4218/etrij.13.0212.0297
Due to limited spectrum resources and differences in link loads, network congestion is one of the key issues in cognitive radio wireless mesh networks. In this letter, a congestion avoidance model with power control, channel allocation, and routing under the signal-to-interference-and-noise ratio is presented. As a contribution, a nested optimization scheme combined with a genetic algorithm and linear programming solver is proposed. Extensive simulation results are presented to demonstrate the effectiveness of our algorithm.
2.4-GHz Power Amplifier with Power Detector Using Metamaterial-Based Transformer-Type On-Chip Directional Coupler
Dang, Trung-Sinh ; Tran, Anh-Dung ; Lee, Bomson ; Yoon, Sang-Woong ;
ETRI Journal, volume 35, issue 3, 2013, Pages 554~557
DOI : 10.4218/etrij.13.0212.0350
This letter presents a power amplifier (PA) with an on-chip power detector for 2.4-GHz wireless local area network application. The power detector consists of a clamp circuit, a diode detector, and a coupled line directional coupler. A series inductor for an output matching network in the PA is combined with a through line of the coupler, which reduces the coupling level. Therefore, the coupler employs a metamaterial-based transformer configuration to increase coupling. The amount of coupling is increased by 2.5 dB in the 1:1 symmetric transformer structure and by 4.5 dB from two metamaterial units along the coupled line.