Browsing by Author "Chang, Chia-Hung"

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A calibrated direct conversion front-end transmitter with resonant matching techniques for mobile WiMAX/WiBro applications
(2012-05-01)
Chang, Chia-Hung
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A direct conversion front-end transmitter with the properties of high linearity and high single sideband rejection ratio is described in this paper. The transmitter employs two resonant matching techniques to improve its operating bandwidth. The first resonant circuit design is applied at the inter-stage of the LO input buffer in order to achieve a wideband frequency response which ranges from dc to 6 GHz. The second resonant circuit is applied at the power amplifier (PA) driver output stage to increase the matching bandwidth and meet both the Worldwide Inter-operability for Microwave Access (WiMAX) and Wireless Broadband (WiBro) applications simultaneously. In addition, the sideband signal and carrier leakage of this transmitter are further minimized by a proposed calibration circuit design to achieve the error vector magnitude (EVM) specifications. The measured single sideband performance with calibration mechanism demonstrates approximately 15 dB improvement on sideband and carrier suppression. The rejected sideband and carrier signals can be up to 55.19 and 56.31 dBc, respectively. The measured dynamic gain range of the transmitter is 53 dB in 1-dB step with a maximum relative gain error lower than 0.4 dB. The transmitter delivers +0.766 dBm output power with EVM of -34.687 dB for the orthogonal frequency division multiple access (OFDMA) 64QAM-3/4 modulated signals. The measured constellation is minimized to be < 1.5% with output power from -2.3 to -36.2 dBm.
A charge accumulation-free voltage-controlled functional electrical stimulator with bi-phasic sinusoidal stimulation
(2019-11-01)
Chen, Wei-Hsien
;
Chang, Chia-Hung
;
Shih, Horng-Yuan
;
Chiu, Tzai-Wen
;
Kuo, Chien-Nan
This paper presents a charge accumulation-free voltage-controlled (VC) bi-phasic sinusoidal functional electrical stimulator (FES) for bioelectronic application. Traditionally, constant current (CC) pulse-shaped FESs with active or passive charge balancers are used to compensate for accumulated charges arise from process, voltage and temperature (PVT) variation as a result of long-term stimulation. Unlike the CC pulse-shaped FES, the VC sinusoidal-shaped FES is adopted here to avoid charge accumulation over time. The charge balancer is not required, substantially reducing system complexity and the chip area of the FES. To demonstrate the feasibility of concept, in this paper, four channels of VC bi-phasic sinusoidal-shaped FESs are integrated with the bio-potential recording circuit to compare with four channels of CC bi-phasic pulse-shaped FESs that are integrated with the same neural recording system for comparison. Measurements indicate an absence of charge accumulation as a result of the VC FESs. In addition, here we adopt the sinusoidal stimulation to reduce transient effects on tissue in comparison to a pulse-shaped method. The bio-potential activities of a cockroach leg that is stimulated for 50 s by the proposed bi-phasic sinusoidal stimulation are recorded. The measured bio-potential activities of a cockroach leg show that no stimulation-evoked leg movement occurs under stimulation by the sinusoidal waveform.
A Chebyshev-Response Step-Impedance Phase-Inverter Rat-Race Coupler Directly on Lossy Silicon Substrate and Its Gilbert Mixer Application
(2011-04)
Wei, Hung-Ju
;
Meng, Chinchun
;
Yu, Sheng-Wen
;
Chang, Chia-Hung
;
電機工程學系
This paper focuses on the analysis and the design methodology of the step-impedance phase-inverter rat-race coupler on a silicon-based process. The issues of impedance limitation and bandwidth are discussed in detail. Our proposed concept utilizes a high silicon dielectric constant, phase-inverter structure, step-impedance technique, and Chebyshev response to make the rat-race coupler more compact (similar to 64 reduction) and highly balanced over a wide operating bandwidth. Moreover, the inter-digital coplanar stripline used in the step-impedance section effectively reduces the characteristic impedance of the transmission line for large size shrinkage and insertion-loss reduction. The demonstrated step-impedance rat-race coupler directly on silicon substrate has 6- similar to 7-dB insertion loss from 5 to 15 GHz and small variations in amplitude/phase balance. Compared with our previous work, the proposed rat-race coupler achieves a 3-dB improvement in the insertion loss. Thus, a 0.13-mu m CMOS Gilbert down-converter with a miniature phase-inverter rat-race coupler at the RF path for wideband single-to-differential signal conversion achieves a noise figure of 16 dB.
A Chebyshev-Response Step-Impedance Phase-Inverter Rat-Race Coupler Directly on Lossy Silicon Substrate and Its Gilbert Mixer Application
(2011-04)
Wei, Hung-Ju
;
Meng, Chinchun
;
Yu, Sheng-Wen
;
Chang, Chia-Hung
;
電機工程學系
This paper focuses on the analysis and the design methodology of the step-impedance phase-inverter rat-race coupler on a silicon-based process. The issues of impedance limitation and bandwidth are discussed in detail. Our proposed concept utilizes a high silicon dielectric constant, phase-inverter structure, step-impedance technique, and Chebyshev response to make the rat-race coupler more compact (similar to 64 reduction) and highly balanced over a wide operating bandwidth. Moreover, the inter-digital coplanar stripline used in the step-impedance section effectively reduces the characteristic impedance of the transmission line for large size shrinkage and insertion-loss reduction. The demonstrated step-impedance rat-race coupler directly on silicon substrate has 6- similar to 7-dB insertion loss from 5 to 15 GHz and small variations in amplitude/phase balance. Compared with our previous work, the proposed rat-race coupler achieves a 3-dB improvement in the insertion loss. Thus, a 0.13-mu m CMOS Gilbert down-converter with a miniature phase-inverter rat-race coupler at the RF path for wideband single-to-differential signal conversion achieves a noise figure of 16 dB.
A Direct Conversion Merged LNA-I/Q-Mixer With Noise Reduction Using Dual Cross Coupling for WiMAX/WiBro Applications
(2012-01-01)
Chang, Chia-Hung
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A direct conversion merged low noise amplifier (LNA) and I/Q-mixer with new noise reduction technique is presented in this letter. The merged LNA-I/Q-mixer employs a dual capacitor cross coupling (CCC) technique to improve the circuit noise performance. The first CCC is applied at the transconductance stage of the LNA to increase the effective transconductance, which in turn lowers the noise figure and decreases the current consumption. The second CCC connection is applied at the cascode stage of the LNA, which can reduce the influence of the noise current from cascode transistors. The simulation shows the proposed combination of the LNA and I/Q-mixer configuration with the dual CCC technique can achieve NF 3 dB better than that of conventional merged topologies in a wideband application. The measured NF is lower than 4.55 dB from 2.3 to 2.7 GHz. In addition, low-power and low-cost circuit is realized due to current-reused and inductor-less design at the interface of the LNA and I-Q mixer. The core circuit only consumes 16.83 mW and occupies 0.16 mm(2) area.
A direct conversion transmitter with digital-assisted DC offset and I/Q phase calibration
(2017-12-01)
Chang, Chia-Hung
;
Chen, Wei-Hsien
;
Gong, Cihun-Siyong Alex
;
Hu, Wei-Wen
;
電機工程學系
A direct conversion transmitter with auto-calibration mechanism is presented in this paper. Both the carrier leakage and in-phase/quadrature (I/Q) phase imbalance are compensated by a proposed calibration algorithm to improve transmitter's single-sideband performance. The digital-assisted correction circuits are implemented in a calibration feedback path to reduce the mismatches and variations, which in turn achieves properties of high linearity, high sideband, and carrier suppression ratio. The measured single-sideband performance with calibration applied to the transmitter demonstrates an over 40 and 50-dBc rejection on sideband and carrier signals at the desired frequency band, respectively. For linearity performance, the measured output 1-dB compression point (OP1dB) is 9.1dBm, while the highest voltage gain is from 4.3 to 6.2dB. Additionally, the error vector magnitude (EVM) of -37.082dB (< 1.4%) can be achieved under an orthogonal frequency division multiple access (OFDMA) 64 QAM-3/4 modulated signal test. The transmitter consumes 112.7mA under supply voltage of 3.3V using the TSMC SiGe BiCMOS technology. Copyright (c) 2017 John Wiley & Sons, Ltd.
A silicon monolithic phase-inverter rat-race coupler using spiral coplanar striplines and its application in a broadband Gilbert mixer
(2008-08-01)
Tseng, Sheng-Che
;
Meng, Chinchun
;
Chang, Chia-Hung
;
Chang, Shih-Hsien
;
Huang, Guo-Wei
This paper realized a broadband uniplanar phase-inverter rat-race coupler using a standard silicon process, and then analyzed this coupler under a lossy condition. A phase inverter is employed in this coupler, not only to extend the operation bandwidth, but also to generate balanced outputs by providing equal lossy paths, while symmetrical spiral-shaped coplanar striplines (CPSs) are also utilized to shrink the coupler size, as well as to construct a phase inverter in the middle of one of spiral CPSs. The lossy CPS, when designed as a distortionless line, has a real characteristic impedance, and thus, perfect port matching of the coupler can be achieved at the center frequency. The operation frequency of this silicon monolithic rat-race coupler with the size of 0.5 mm(2) is extremely wide and ranges from 5 to 23 GHz. The dissipated loss, transmission coefficient, and isolation of the rat-race coupler are approximately 5.5, -8, and below -25 dB, respectively. In addition, a wideband Gilbert micromixer with an integrated uniplanar phase-inverter rat-race coupler at the local oscillator port is demonstrated using 0.35-mu m SiGe BiCMOS technology. This mixer works from 2.5 to 13 GHz with 12-dB conversion gain, -16-dBm IP(1) (dB), -4-dBm IIP(3), and 14-dB noise figure. The chip size of the mixer with an integrated coupler is approximately 1.4 mm x 1.4 mm.
A study of grid artifacts formation and elimination in computed radiographic images
(2006-12-01)
Lin, Chih-Yang
;
Lee, Wen-Jeng
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Chen, Shyh-Jye
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Tsai, Ching-Hwa
;
Lee, Jei-Han
Computed radiography (CR) has many advantages such as filmless operations, efficiency, and convenience. Furthermore, it is easier to integrate with the picture archiving and communication systems. Another important advantage is that CR images generally have a wider dynamic range than conventional screen film. Unfortunately, grid artifacts and moire pattern artifacts may be present in CR images. These artifacts become a more serious problem when viewing CR images on a computer monitor when a clinic grade monitor is not available. Images produced using a grid with higher frequency or a Potter-Bucky grid (i.e., a moving grid, Bucky for short) can reduce occurrence but cannot guarantee elimination of these artifacts [CR & PACS (2000); Detrick F (2001), pp 7-8]. In this paper, the formation of the artifacts is studied. We show that the grid artifacts occur in a narrow band of frequency in the frequency domain. The frequency can be determined, accurately located, and thus removed from the frequency domain. When comparing the results obtained from the proposed method against the results obtained using previous computer methods, we show that our method can achieve better image quality.
A Variable Gain Envelope Modulator with Hybrid Topology for High Linearity/Efficiency Polar Transmitter Application
(2015)
Hung, Wei-Ping
;
Chang, Chia-Hung
;
傳播研究所
;
Institute of Communication Studies
An envelope modulator with hybrid topology for a high linearity and efficiency polar transmitter is described in this paper. The hybrid configuration exhibits a high speed and high efficiency combination by a linear amplifier and a switching amplifier, respectively, thereby improving the power added efficiency(PAE) of the polar transmitter. Moreover, to achieve wideband requirement, an operational trans-conductance amplifier with class AB output stage and variable gain function is designed in the linear amplifier. The switching amplifier adopts a buck converter design. The output dynamic range of envelope modulator shows a 5 dB variable gain with 1 dB resolution. The measured output voltage is from 0 similar to 3.5 V under the supply voltage of 3.5 V. The maximum driving power is 0.991 W for a 20 ohm loading.
Application of Smart Appliances to Wireless Area Network and Module Development
(2017-01-01)
Hung, Wei-Ping
;
Lee, Tsern-Huei
;
Chang, Chia-Hung
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we implement the Wi-Fi hardware architecture. The core chip designed by the MediaTek Corporation is used to develop its peripheral circuits. The chip supports USB Type and can control the lighting circuit through the APP on the mobile phone, so as to simulate the switch of household electrical appliances. In the future, consumers can purchase home appliances with built-in communication modules and integrate them with the Home Energy Management System (HEMS), which can be used to control wireless energy-saving.
Broadband Gilbert micromixer with an LO Marchand balun and a TIA output buffer
(2006)
Tseng, Sheng-Che
;
Meng, Chinchun
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Chang, Chia-Hung
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Wu, Chih-Kai
;
Hung, Guo-Wei
A single-ended wideband downeonversion Gilbert micromixer is demonstrated in this paper using 0.35-um SiGe BiCMOS technology. Because of the wideband matching property of the micromixer, it can perform broad frequency translation. The TIA is utilized in the IF stage while a broadband Marchand balun is employed not only to generate differential LO signals but also to reserve the wideband operation of the mixer. This singleended wideband mixer has the conversion gain of 15 dB, IP(1dB) of 17 dBm, and IIP(3) of -6.5 dBm and works from 3.5 to 14.5 GHz. The input return loss is below -14 dB and the chip size is 1x1 mm(2).
Differential LC Ladder LNA with Proposed third-Order Active Notch Filter for UWB Band Group1
(2009)
Tsou, Yu-Lin
;
Shih, Horng-Yuan
;
Kuo, Chien-Nan
;
Chang, Chia-Hung
;
電子工程學系及電子研究所
A proposed third-order active notch filter was developed for a LC ladder Low Noise Amplifier (LNA) applied for UWB band group1 in standard 0.13 mu m CMOS technology. The notch filter eliminated interfering signal at 5.85 GHz and improved third-order input intercept point (IIP3) by 4.7 dB under interferences of 802.11a test. The measured maximum power gain was 15.87 dB at 4488MHz, minimum NF was 3.19 dB at 3960MHz that performs FOM of 1.3 (/mW) and measured P1dB was -16.82 dBm at 4488 MHz.
Dual cross-coupling LNA with forward body bias technique
(2012-08-30)
Chang, Chia-Hung
;
Wang, Tao
;
Jou, Christina F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
A fully integrated low-power LNA with dual cross-coupling and forward body bias (FBB) techniques is presented. The first cross-coupling circuit is applied at the transconductance stage. By connecting body nodes to each other's source terminals, the body cross-coupling network forms the gate-driven and body-driven simultaneously input stage to gain its effective transconductance, which in turn improves the noise performance and decreases current consumption. In addition, the second capacitor cross-coupling configuration is applied at the input stage to form a feed-forward connection, which results in not only boosting the effective transconductance, but also reducing the influence of the gate noise from the input transistors as well. Moreover, to decrease the overall power consumption further, the FBB technique is employed to lower the supply voltage. The measured noise figure is lower than 3.38 dB and the core circuit consumes only 2.16 mW.
Electron transport in high-resistance semiconductor nanowires through two-probe measurements
(2010)
Lin, Yen-Fu
;
Chen, Tzu-Han
;
Chang, Chia-Hung
;
Chang, Yu-Wei
;
Chiu, Yi-Cheng
Since the successful fabrication of semiconductor nanowires, various techniques have been developed to contact these nanowires and to probe their intrinsic electrical properties. Although many novel quasi one-dimensional materials such as Pb(1-x)Mn(x)Se nanoarrays were recently produced, their intrinsic electron transport properties have not been extensively studied so far. In this work, we demonstrate that an ordinary source-drain configuration of field-effect transistors or the two-probe measurement can be applied to the exploration of the intrinsic properties of nanowires. This two-probe measurement approach also works on highly resistive nanowires without an Ohmic contact issue. By using this method, electron transport behavior, resistivity, and carrier concentrations of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se semiconductor nanowires have been investigated. Due to the tiny cross-section and few conducting channels, a nanomaterial usually reveals an ultra high resistance. This technique demonstrates a two-probe characterization of nanostructures, paving the simplest way toward electrical characterizations of all high-resistance nanomaterials such as deoxyribonucleic acid (DNA), molecules and organics.
Long-Term Performance Studies of a LoRaWAN-based PM2.5 Application on Campus
(2018-01-01)
Wang, Shie-Yuan
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Zou, Ji-Jhe
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Chen, Yo-Ru
;
Hsu, Chun-Chia
;
Cheng, Yu-Hsiang
Recently, LoRa/LoRaWAN has been proposed as a promising LPWAN technology for Internet-of-Things (IoT) applications. For monitoring the long-term PM2.5 air quality on our campus, starting from February 1 2017, we have set up a LoRaWAN-based PM2.5 air quality monitoring system on our campus. In total, twenty-two PM2.5 sensor devices have been operating at the rooftop of buildings or on the lamp poles since then. Each of these PM2.5 sensor devices uses a LoRaWAN module to send its most recent PM2.5 value to the LoRaWAN gateway every 72 seconds. After being received successfully by the LoRaWAN gateway, the packets carrying these values were stored into a database with their SNR/RSSI information. With the sequence numbers added by our PM2.5 application running on each device, the packets stored in the database provide many important information about the long-term packet loss rate performance of LoRaWAN on campus. In this paper, we process these data to report real long-term performance of LoRaWAN when used on campus.
Monolithic broadband Gilbert micromixer with an integrated Marchand balun using standard silicon IC process
(2006-12-01)
Tseng, Sheng-Che
;
Meng, Chinchun
;
Chang, Chia-Hung
;
Wu, Chih-Kai
;
Huang, Guo-Wei
A single-ended wideband downconversion Gilbert micromixer is demonstrated in this paper using 0.35-mu m SiGe BiCMOS technology. A transimpedance amplifier with resistive feedback is utilized in the IF stage while a broadband Marchand balun is employed to generate wideband differential local oscillator signals. The planar Marchand balun topology employed in this paper can generate truly balanced signals even in the presence of the lossy low-resistivity (similar to 10 Omega (.) cm) silicon substrate. A systematic approach to measure the frequency response of each individual stage in a Gilbert mixer is developed in this paper. This single-ended wideband mixer has the conversion gain of 15 dB, IP1dB of -19 dBm, IIP3 of -7 dBm, and the noise figure of 13 dB. The mixer works from 3.5 to 14.5 GHz.
Nanocontact disorder in InP nanowire devices for the enhancement of visible light and oxygen gas sensitivities
(2017-01-01)
Lin, Yen-Fu
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Chang, Chia-Hung
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Hung, Tsu-Chang
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Liu, Zhaoping
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Fang, Jiye
InP nanowires, synthesized through a self-seeded growth approach, are used in the fabrication of field-effect transistors which consist of source, drain, and back-gate electrodes. The weak gating voltage dependence implies low carrier concentrations whereas its behavior reveals native n-type doping in InP nanowires. These InP nanowire devices exhibit a vast variation of room-temperature resistance that raises a question about contact resistance. For devices of low room-temperature resistance, electron transport in InP nanowires is investigated using temperature dependent resistance in the temperature range between 80 and 300 K, and it can be analyzed using the model of thermal activation. For other devices of high room-temperature resistance, we take into account nanocontact resistance. Models of both Schottky contact and Mott's variable range hopping (VRH) are considered. The two resistances are connected in parallel to give total contact resistance of InP nanowire devices. After fitting experimental data by the proposed model, we estimate effective Schottky barriers and disorder contributions to nanocontact resistance. The effective Schottky barrier, and the nanocontact Schottky and Mott's VRH resistances are plotted as a function of the device room-temperature resistance which indicates the scale of disorder. Using room-temperature resistance of InP nanowire devices, the devices are classified into nanowire-or contact-dominated devices. The two different class of devices are used to check their photo-and gas-sensitivities. The contact-dominated InP nanowire devices show low dark current and low photocurrent as usual, but these contact-dominated devices give high ratio of photo-to dark-current. That result reveals a high photo-sensitivity for those devices of high nanocontact resistance. On the other hand, for gas sensing experiments, the contact-dominated devices show as well a high ratio of resistance under O-2 to that under N-2 gas exposure. (C) 2017 The Authors. Published by Elsevier B.V.
Nanocontact Disorder in Nanoelectronics for Modulation of Light and Gas Sensitivities
(2015-08-11)
Lin, Yen-Fu
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Chang, Chia-Hung
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Hung, Tsu-Chang
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Jian, Wen-Bin
;
Tsukagoshi, Kazuhito
To fabricate reliable nanoelectronics, whether by top-down or bottom-up processes, it is necessary to study the electrical properties of nanocontacts. The effect of nanocontact disorder on device properties has been discussed but not quantitatively studied. Here, by carefully analyzing the temperature dependence of device electrical characteristics and by inspecting them with a microscope, we investigated the Schottky contact and Mott's variable-range-hopping resistances connected in parallel in the nanocontact. To interpret these parallel resistances, we proposed a model of Ti/TiOx in the interface between the metal electrodes and nanowires. The hopping resistance as well as the nanocontact disorder dominated the total device resistance for high-resistance devices, especially at low temperatures. Furthermore, we introduced nanocontact disorder to modulate the light and gas responsivities of the device; unexpectedly, it multiplied the sensitivities compared with the intrinsic sensitivity of the nanowires. Our results improve the collective understanding of electrical contacts to low-dimensional semiconductor devices and will aid performance optimization in future nanoelectronics.
Non-contact Pulse-based Radar with an Excited RF Pulse Generator for Vital-sign Application
(2019-01-01)
Chen, Wei-Hsien
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Chang, Chia-Hung
;
Kuo, Chien-Nan
;
Hsu, Chia-Chin
;
電子工程學系及電子研究所
This paper presents a pulse-based investigation to generate a serial of sensing pulses for probing the reciprocal movements of heartbeat and chest, respectively. An excited self-contained RF pulse generator with digital assisted controller is used for pulse shaping and performing nanosecond sensing pulses. In addition, the generator is implemented by a common source field-controlled transistor and a contour circuit by micro-strip line. Hence, in this paper, probing pulses and receives the echoes from the investigated subject back and forth by the whole sensing radar based on the monostatic antenna system. The demodulator is utilized to perform the multiplication of the reference probing waves and the return echoes delayed by the time interval between the emitted signal and reflected waves back to the radar module. The following analog baseband processing circuits with 3-stage topology for further amplifying and filtering the received physiological information help to increase the overall signal-to-noise ratio (SNR). The measured results demonstrate that the radiated RF pulses and vital signs are expected.
Non-invasive Detection of Object by UWB Radar
(2017-01-01)
Hung, Wei-Ping
;
Lee, Tsern-Huei
;
Chang, Chia-Hung
;
電信工程研究所
;
Institute of Communications Engineering
The use of UWB system front-end matching with the antenna from the VCO side adjustment, the key in the vicinity of the VCO circuit matching adjustment; because eight antennas, each antenna will have some slight differences in matching, resulting in the received DC value is not Will be in the same level, and the switch circuit in the switch antenna, it will allow a peak level (about 100ms), and switch the antenna when switching about 420ms similar to 480ms or so. In order to improve the above problem, when switching to the antenna, a variable of the calculation time is used as the current switching antenna, and the time of the switching of the antenna is changed, The time at the time of the operation is changed by 60 ms due to the switching time. As mentioned above, the calculated time will not be a constant value. Therefore, the remainder is divided by a constant, since the value of the first 100 ms can not be used, So to take the signal between 200ms similar to 400ms in order to correctly reflect the antenna front of the object of the reflected signal; After modifying the above problem, the software interface can detect whether there are metal objects in front of the antenna, and L-shaped steel plate to do experiments, The results show that the L pattern can be displayed on the screen; follow-up planning of a variety of different materials of the metal material corresponding to the DC level, and the use of statistical methods can be further accurate analysis of different metal types, the future can be extended application of Homeland Security Survey, Metal material detection and other areas