In this work, a simple method for extracting MOSFET threshold voltage, effective channel length and channel mobility by using S-parameter measurement is presented. In the new method, the dependence between the channel conductivity and applied gate voltage of the MOSFET device is cleverly utilized to extract the threshold voltage, while biasing the drain node of the device at zero voltage during measurement. Moreover, the effective channel length and channel mobility can also be obtained with the same measurement. Furthermore, all the physical parameters can be extracted directly on the modeling devices without relying on specifically designed test devices. Most important of all, only one S-parameter measurement is required for each device under test (DUT), making the proposed extraction method promising for automatic measurement applications.

The intermodulation distortion (IMD) due to laser diode (LD) nonlinearity of an asynchronous direct-sequence code division multiple access (DS/CDMA) system in optical transmission is analyzed. A third-order polynomial without memory is used to present LD nonlinearity. In DS/CDMA systems, only one harmonic of the third-order inter-modulation term falls on the signal frequency band and influences the system performance. The average distortion is derived with only the information of autocorrelation functions. The results are useful for CDMA system design and performance analysis. With LD nonlinearity it is necessary to select an optimal modulation index that provides a maximum signal-to-noise ratio (SNR). The analytical method is applicable to other general nonlinearities in CDMA systems.

Dynamic analysis is frail and insufficient to find hidden paths in environment-intensive program. By analyzing a broad spectrum of different concolic testing systems, we conclude that a number of them cannot handle programs that interact with the environment or require a complete working model. This paper addresses this problem by automatically identifying and modifying outputs of the data input interface function(DIIF). The approach is based on fine-grained taint analysis for detecting and updating the data that interacts with the environment to generate a new set of inputs to execute hidden paths. Moreover, we developed a prototype and conducted extensive experiments using a set of complex and environmentally intensive programs. Finally, the result demonstrates that our approach could identify the DIIF precisely and discover hidden path obviously.

Atmospheric optical communication (AOC) system using subcarrier PSK modulation is proposed and its superiority to OOK modulation in the presence of scintillation is discussed theoretically. An experimental AOC setup with a subcarrier modulated by 155.52(Mb/s) DPSK at light wave-length λ=0.83(µm) over an 1.8(km) outdoor path is employed to show the performance. Theoretical and experimental results are compared under scintillation in clear weather and a good agreement is observed. Finally, AOC systems using subcarrier M-ary PSK and multiple subcarriers are proposed and discussed.

A novel divide-by-3 injection-locked frequency divider (ILFD) is proposed. The ILFD circuit is realized with a cross-coupled n-core MOS LC-tank oscillator embedded with a push-push signal generator and two injection MOSFETs for coupling the injection signal into the resonator. The ILFD uses the linear mixer to extend the locking range and has been implemented in a standard 0.18 µm CMOS process. The core power consumption of the ILFD core is 3.12 mW. The divider's free-running frequency is tunable from 4.26 GHz to 4.9 GHz by tuning the varactor's control bias, and at the incident power of 0 dBm the locking range of the ILFD used as a divide-by-3 divider is 1.5 GHz, from 12.5 GHz to 14.0 GHz.

A 5.2 GHz 1 dB conversion gain, IP1 dB = -19 dBm and IIP3= -9 dBm double quadrature Gilbert downconversion mixer with polyphase filters is demonstrated by using 0.35 µm SiGe HBT technology. The image rejection ratio is better than 47 dB when LO=5.17 GHz and IF is in the range of 15 MHz to 45 MHz. The Gilbert downconverter has four-stage RC-CR IF polyphase filters for the image rejection. Polyphase filters are also used to generate LO and RF quadrature signals around 5 GHz in the double quadrature downconverter.

High-frequency characteristics of SiGe heterojunction bipolar transistors with different emitter sizes are studied based on pulsed measurements. Because the self-heating effect in transistors will enhance the Kirk effect, as the devices operate in high current region, the measured cutoff frequency and maximum oscillation frequency decrease with measurement time in the pulsed duration. By analyzing the equivalent small-signal device parameters, we know the reduction of cutoff frequency and maximum oscillation frequency is attributed to the reduction of transconductance and the increase of junction capacitances for fixed base-emitter voltage, while it is only attributed to the degradation of transconductance for fixed collector current. Besides, the degradation of high-frequency performance due to self-heating effect would be improved with the layout design combining narrow emitter finger and parallel-interconnected subcells structure.

A selectively ion-implanted collector (SIC) is implemented in a 0.8 µm BiCMOS process to improve the RF characteristics of the BJT devices. The SIC BJT device has better ft and fmax than the FIC (fully ion-implanted collector) BJT device because the extrinsic base-collector capacitance is reduced by the SIC process. The ft is 7.8 GHz and fmax is 9.5 GHz for the SIC BJT device while the ft is 7.2 GHz and fmax is 4.5 GHz for the FIC BJT device when biased at Vce=3.6 V and Jc=0.07 mA/µm2. The noise parameters are the same for both BJT devices but the associated gain is higher for the SIC BJT device.

Residents living in a nursing home usually have established medical histories in multiple sources, and most previous medicine management systems have only focused on the integration of prescriptions and the identification of repeated drug uses. Therefore, a comprehensive medicine management system is proposed to integrate medical information from different sources. The proposed system not only detects inappropriate drugs automatically but also allows users to input such information for any non-prescription medicines that the residents take. Every participant can fully track the residents' latest medicine use online and in real time. Pharmacists are able to issue requests for suggestions on medicine use, and residents can also have a comprehensive understanding of their medicine use. The proposed scheme has been practically implemented in a nursing home in Taiwan. The evaluation results show that the average time to detect an inappropriate drug use and complete a medicine record is reduced. With automatic and precise comparisons, the repeated drugs and drug side effects are identified effectively such that the amount of medicine cost spent on the residents is also reduced. Consequently, the proactive feedback, real-time tracking, and interactive consulting mechanisms bind all parties together to realize a comprehensive medicine management system.

The port-to-port isolation of the micromixer is studied using three different p-type downconversion micromixers in 0.35-µm CMOS technology. Both the body effect and the well isolation influence the port-to-port isolation significantly. The body effect degrades the LO-to-IF isolation and also deteriorates the LO-to-RF isolation. Without the well isolation, the LO-to-RF isolation drops. However, the RF-to-IF isolation is independent of the body effect and well isolation. The p-type micromixer with a separate N-well and without body effect has the best port-to-port isolation properties; its LO-to-IF, LO-to-RF, and RF-to-IF isolations are -59 dB, -58 dB, and -30 dB, respectively.

A channel coding which combines convolutional coding and M-ary PSK/orthogonal multi-carrier (MPSK/OMC) transmission is proposed. A coding gain is achieved without sacrificing the data rate or occupying extra bandwidth. The proposed coding formula is that the imformation data bits of bit interval Ts are serial to parallel converted to P parallel branches where each branch has a bit interval Tp = PTs. The data bits of the parallel branches are encoded through a rate nP/(n + 1)(2P - 1) convolutional encoding process and the total (n+1)(2P-1) symbol of the encoder output is transmitted by 2P - 1 OMCs where each carrier is modulated by MPSK/OMC (M = 2n + 1). Following performance analysis of a coding form using rate P/(2P - 1) convolutional encoder and BPSK/OMC modulation, a general channel coding combining convolutional coding and MPSK/OMC modulation is discussed.

Arterial spin labeling (ASL) is a non-invasive magnetic resonance imaging (MRI) method that can provide direct and quantitative measurements of cerebral blood flow (CBF) of scanned patients. ASL can be utilized as an imaging modality to detect Alzheimer's disease (AD), as brain atrophy of AD patients can be revealed by low CBF values in certain brain regions. However, partial volume effects (PVE), which is mainly caused by signal cross-contamination due to voxel heterogeneity and limited spatial resolution of ASL images, often prevents CBF in ASL from being precisely measured. In this study, a novel PVE correction method is proposed based on pixel-wise voxels in ASL images; it can well handle with the existing problems of blurring and loss of brain details in conventional PVE correction methods. Dozens of comparison experiments and statistical analysis also suggest that the proposed method is superior to other PVE correction methods in AD diagnosis based on real patients data.

Direct parameter extraction is believed to be the most accurate method for equivalent-circuits modeling of heterojunction bipolar transistors (HBT's). Using this method, the parasitic elements, followed by the intrinsic elements, are determined analytically. Therefore, the quality of the extrinsic elements extraction plays an important role in the accuracy and robustness of the entire extraction algorithm. This study proposes a novel extraction method for the extrinsic elements, which have been proven to be strongly correlated with the intrinsic elements. By utilizing the specific correlation, the equivalent circuit modeling is reduced to an optimization problem of determining six specific extrinsic elements. Converting the intrinsic equivalent circuit into its common-collector configuration, all intrinsic circuit elements are extracted using exact closed-form equations for both the hybrid-π and the T-topology equivalent circuits. Additionally, a general explicit equation on the total extrinsic elements is derived, subsequently reducing the number of optimization variables. The modeling results are presented, showing that the proposed method can yield a good fit between the measured and calculated S parameters.

In this paper, an accurate and low-cost method for on-wafer noise figure measurement, specifically designed for low-noise amplifiers (LNAs), will be proposed. An experiment conducted on a 5 GHz LNA demonstrates that a good agreement can be reached between the measurement result of the proposed method and that of a commercial noise parameter measurement system.

RF MOSFET's are usually measured in common source configuration by a 2-port network analyzer, and the common gate and common drain S-parameters cannot be directly measured from a conventional 2-port test structure. In this work, a 4-port test structure for on-wafer measurement of RF MOSFET's is proposed. Four-port measurements for RF MOSFET's in different dimensions and the de-embedded procedures are performed up to 20 GHz. The S-parameters of the RF MOSFET in common source (CS), common gate (CG), and common drain (CD) configurations are obtained from a single DUT and one measurement procedure. The dependence of common source S-parameters of the device on substrate bias are also shown.

This paper demonstrates a small compact 5.7 GHz upconversion Gilbert micromixer using 0.35 µm SiGe HBT technology. A micromixer has a broadband matched single-ended input port. A passive LC current combiner is used to convert micromixer differential output into a single-ended output and doubles the output current for single-ended-input and single-ended-output applications. Thus, a truly balanced operation of a Gilbert upconversion mixer with a single-ended input and a single-ended output is achieved in this paper. The fully matched upconversion micromixer has conversion gain of -4 dB, OP1 dB of -9 dBm and OIP3 of 4 dBm when input IF=0.3 GHz, LO=5.4 GHz and output RF=5.7 GHz. The IF input return loss is better than 18 dB for frequencies up to 20 GHz while RF output return loss is 25 dB at 5.7 GHz. The supply voltage is 3.3 V and the current consumption is 4.6 mA. The die size is 0.90.9 mm2 with 3 integrated on-chip inductors.

Several problems in built-in-jitter-measurement (BIJM) system designs have been identified in recent years. The problems are associated with the external low-jitter sampling clock, chip area, timing resolution, or the measurement range via the process voltage temperature (PVT) variation effect. In this work, there are three proposed approaches and one conventioanl method that improve BIJM systems. For the system level, a proposed real equivalent-signal sampling technique is utilized to clear the requirement of the external low-jitter sampling clock. The proposed Vernier caliper structure is applied to reduce chip area cost for the designated timing resolution. At the circuit level, the proposed auto focus technique eliminates the PVT variation effect for the measurement range. The stepping scan technique is the conventional method that employed to minimize the area cost of counter circuits. All of these techniques were implemented in the 0.35 µm CMOS process. Furthermore, these techniques are successfully verified in 14 ps circuit resolution and a 500*750 µm chip area for the 100-400 MHz measurement range.

In data center networks, Quantized Congestion Notification (QCN) has been ratified as the standard congestion management mechanism in the link layer. Since QCN nonlinearly switches between the rate increase and decrease stages, it is very difficult to understand QCN in depth and provide theoretical guidelines on setting the buffer size of the QCN switch. This paper gives an explicit formula for the boundary of buffer occupancy of the QCN switch. Specifically, based on the fluid model of QCN, we first derive the uniformly asymptotic stability condition of the QCN system. Then, under the condition that QCN is uniformly asymptotically stable, we analyze the buffer occupancy of the QCN switch theoretically and show that the classic rule-of-thumb for buffer sizing is not suitable for QCN. Finally, simulations validate the accuracy of our theoretical results.

Microcellular radio direct-sequence code division multiple access (DC-CDMA) system using optical link to connect their base stations to a central station is a solution of cost-effective and efficient spectrum reuse to meet the growing demand for mobile communications. In addition to the inherent multiuser interference (MUI) of CDMA signals, the system capacity is significantly reduced by a nonlinear distortion (NLD) due to the nonlinearity of optical link. In this paper, a two-stage cancellation technique is introduced into the system to cancel both the MUI and the NLD. It is performed at the receiver of the central station where the random ingredients of all user signals are estimated, and the MUI and the NLD are rebuilt and removed from the received signal. The validity of the cancellation technique is theoretically analyzed and shown by the numerical results. The analytical method and its results are also applicable to other general nonlinear CDMA.

There is increasing interest using CMOS circuits for highly integrated high frequency wireless telecommunications systems. This paper reviews recent works in transceiver architectures, circuits and devices technology for CMOS RFIC application. A number of practical problems those must be resolved in CMOS RFIC design are also discussed.