A /spl Sigma/-/spl Delta/ fractional-N frequency synthesizer using a wide-band integrated VCO and a fast AFC technique for GSM/GPRS/WCDMA applications

A fractional-N frequency synthesizer (FNFS) in a 0.5-/spl mu/m SiGe BiCMOS technology is implemented. In order to operate in a wide-band frequency range, a switched-capacitors bank LC tank voltage-controlled oscillator (VCO) and an adaptive frequency calibration (AFC) technique are used. The measured VCO tuning range is as wide as 600 MHz (40%) from 1.15 to 1.75 GHz with a tuning sensitivity from 5.2 to 17.5 MHz/V. A 3-bit fourth-order /spl Sigma/-/spl Delta/ modulator is used to reduce out-of-band phase noise and to meet a frequency resolution of less than 3 Hz as well as agile switching time. The experimental results show -80 dBc/Hz in-band phase noise within the loop bandwidth of 25 kHz and -129 dBc/Hz out-of-band phase noise at 400-kHz offset frequency. The fractional spurious is less than -70 dBc/Hz at 300-kHz offset frequency and the reference spur is -75 dBc/Hz. The lock time is less than 150 /spl mu/s. The proposed synthesizer consumes 19.5 mA from a single 2.8-V supply voltage and meets the requirements of GSM/GPRS/WCDMA applications.     

A Balun-BPF Using a Dual Mode Ring Resonator

In this letter, a Balun-bandpass filter (BPF) is proposed by using a dual-mode ring resonator. The Balun-BPF is not a simply combined or integrated component of a BPF and a Balun but a single BPF with the balun function. We obtained the proper balanced outputs and two-pole BPF characteristic by symmetrically placing the output ports at lambda/2 distance from each other on the dual-mode ring resonator. The fabricated Balun-BPF has a bandwidth of 40 MHz and an insertion loss of 2.4 dB at a center frequency of 2.45 GHz. The differences between the two outputs are 180-184deg in phase and within 1dB in magnitude. The measured frequency responses agree well with simulated ones.     

A 3 Gb/s transmitter with a tapless pre-emphasis CML output driver

A 3 Gb/s wireline transmitter (Tx) with a tapless pre-emphasis current-mode logic output driver is presented in this paper. The proposed output driver can support 2.5, 6 and 10 dB pre-emphasis without any additional current tap. It can reduce the current consumption of the output driver by 30 %. The 1.5 GHz phase-locked loop (PLL), multi-phase generator, and 26-to-1 serializer are utilized to serialize 26-bit parallel data to 1-bit 3 Gb/s serial data stream. The rms and peak-to-peak jitters of PLL are 2.97 and 22.5 ps, respectively. The eye opening of the proposed output driver at 3 Gb/s is 0.8UI with a 10 dB loss channel. The current consumption of the output driver is only 5.14 mA, and the Tx is 9 mA. The area of the Tx is 0.72 mm² using the 0.11 μm CMOS process.     

An X-band high-efficiency MMIC power amplifier with 20-dBreturn losses

Describes the design principles and measured performance of an X-band high-efficiency monolithic-microwave-integrated-circuit (MMIC) power amplifier and discuss pertinent factors of the ion-implantation process. Also presented is a worst-case power prediction of the chip performance and a large-signal design using small-signal simulation. This balanced amplifier is fully monolithic with input and output return losses of better than 20 dB provided by Lange couplers. These return losses make it very convenient to cascade with other components. For high-efficiency operation, the drain voltage is 6 V. Across the 40% bandwidth from 8 to 12 GHz, the amplifier produces 1.6 to 2.1 W of output power at 33 to 40% power-added efficiency. For high-power operation, the drain voltage is 8.5 V. The amplifier can produce 2.4 to 2.8 W of output power at 26 to 29% power-added efficiency across the same 40% bandwidth     

Compact Circularly Polarized Antenna with a Capacitive Feed for GPS/GLONASS Applications

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual‐feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are 28 mm × 28 mm × 4 mm, which is the most compact size among the dual‐band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).     

Reverse link capacity analysis of a CDMA cellular system with mixedcell sizes

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are unavoidable to increase the capacity of the cellular system. Cell splitting makes a cellular system have mixed cell sizes. For cell planning, it is necessary to analyze the reverse link capacity of a code-division multiple-access (CDMA) cellular system with mixed cell sizes. In this paper, we propose a method to calculate the reverse link capacity of a CDMA cellular system with mixed cell sizes. When a macro cell is split into three micro cells, as an example, we calculate the reverse link capacities for the three micro cells and the neighboring macro cells. The results show that as the radius of a micro cell decreases, the reverse link capacity of the micro cell increases, while those of the neighboring macro cells decrease     

A dynamic quarantine scheme for controlling unresponsive TCP sessions

In addition to unresponsive UDP traffic, aggressive TCP flows pose a serious challenge to congestion control and stability of the future Internet. This paper considers the problem of dealing with such unresponsive TCP sessions that can be considered to collectively constitute a Denial-of-Service (DoS) attack on conforming TCP sessions. The proposed policing scheme, called HaDQ (HaTCh-based Dynamic Quarantine), is based on a recently proposed HaTCh mechanism, which accurately estimates the number of active flows without maintenance of per-flow states in a router. We augment HaTCh with a small Content Addressable Memory (CAM), called quarantine memory, to dynamically quarantine and penalize the unresponsive TCP flows. We exploit the advantage of the smaller, first-level cache of HaTCh for isolating and detecting the aggressive flows. The aggressive flows from the smaller cache are then moved to the quarantine memory and are precisely monitored for taking appropriate punitive action. While the proposed HaDQ technique is quite generic in that it can work with or without any AQM scheme, in this paper we have integrated HaDQ and an AQM scheme to compare it against some of the existing techniques. For this, we extend the HaTCh scheme to develop a complete AQM mechanism, called HRED. Simulation-based performance analysis indicates that by using a proper configuration of the monitoring period and the detection threshold, the proposed HaDQ scheme can achieve a low false drop rate (false positives) of less than 0.1%. Comparison with two AQM schemes (CHOKe and FRED), which were proposed for handling unresponsive UDP flows, shows that HaDQ is more effective in penalizing the bandwidth attackers and enforcing fairness between conforming and aggressive TCP flows.     

Systematic Generation of Current-Mode Linear Transformation Filters Based on Multiple Output CCIIs

A transformation called current-mode linear transformation (CMLT) and its filter applications using multiple output second-generation current conveyors (MOCCIIs) are presented. The systematic method is developed to realize CMLT MOCCII-based filters efficiently. Based on the proposed design tables, we can synthesize high-order current-mode all-pole and elliptic filters with MOCCIIs, grounded resistors and capacitors. Moreover, the high-frequency elliptic filter can also be efficiently realized by adding capacitors to the relative all-pole filter, although floating capacitors are needed. Third-order Chebychev and elliptic lowpass filters are described in this paper. Experimental results that confirm the theoretical analysis are obtained. Furthermore, the proposed circuits can be extended to higher-order filters.     

Classification of pixels in a noisy grayscale image of polar ice

Often, in synthetic aperture radar (SAR) images of polar ice, one encounters shadow-like features across the images. Such features make it difficult to classify pixels into ice and water. Accordingly, it becomes a challenge to determine the true size and boundaries of ice floes in an SAR image of polar ice. We develop a simple statistical procedure which classifies pixels of an image by eliminating the effects of shadow-like features. Methodology developed in this paper is illustrated using some noisy SAR images of ice floes in the Arctic sea.