Cancellation Circuit Research Articles

A 3-V, 0.35-μm CMOS Bluetooth receiver IC

A fully integrated CMOS low-IF Bluetooth receiver is presented. The receiver consists of a radio frequency (RF) front end, a phase-locked loop (PLL), an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, and a frequency offset cancellation circuit. The highlights of the receiver include a low-power active complex filter with a nonconventional tuning scheme and a high-performance mixed-mode GFSK demodulator. The chip was fabricated on a 6.25-mm/sup 2/ die using TSMC 0.35-/spl mu/m standard CMOS process. -82 dBm sensitivity at 1e-3 bit error rate, -10 dBm IIP3, and 15 dB noise figure were achieved in the measurements. The receiver active current is about 65 mA from a 3-V power supply.

ＦＰＮキャンセル・積分機能内蔵対数変換形ＣＭＯＳイメージセンサ

A new CMOS image sensor featuring logarithmic conversion is described. The sensor has 654 (H) × 494 (V) pixels, and the cell size is 8μm (H) ×8μm (V). We previously developed logarithmic conversion CMOS image sensors with either an FPN cancellation circuit or an integration circuit. This one has both. The sensor shows clear images without FPN and without flicker noise in brightness fluctuation. Furthermore, the afterimage level was reduced by a new pixel driving method.

Front-end electronics for high rate, position sensitive neutron detectors

Advanced neutron detectors for experiments at new spallation sources will require greater counting rate capabilities than previously attainable. This necessitates careful design of both detector and readout electronics. As part of a new instrument for protein crystallography at LANSCE, we are constructing a detector whose concept was described previously (IEEE Trans. Nucl. Sci. NS-46 (1999) 1916). Here, we describe the signal processing circuit, which is well suited for 3He detectors with a continuous interpolating readout. The circuit is based on standard charge preamplification, transmission of this signal over 20 meters or so, followed by sample and hold using a second order gated baseline restorer. This latter unit provides high rate capability without requiring pole-zero and tail cancellation circuits. There is also provision for gain-adjustment. The circuits are produced in surface mounted technology.

A 500-Mb/s quadruple data rate SDRAM interface using a skew cancellation technique

A quadruple data rate (QDR) synchronous DRAM (SDRAM) interface processing data at 500 Mb/s/pin with a 125-MHz external clock signal is presented. Since the QDR interface has a narrower data timing window, a precise skew control on data signals is required. A salient skew cancellation technique with a shared skew estimator is proposed. The skew cancellation circuit not only reduces the data signal skews on a printed circuit board down to 250 ps, but also aligns the data signals with an external clock signal. The entire interface, fabricated in a 0.35-/spl mu/m CMOS technology, includes a high-speed data pattern generator and consumes 570 mW of power at 3.0-V supply. The active die area of the chip with the on-chip data pattern generator is 2.4 mm/sup 2/.

Low‐temperature poly‐Si TFT data drivers for an SVGA a‐Si TFT‐LCD panel

Abstract—Low‐temperature poly‐Si TFT data drivers for an SVGA a‐Si TFT‐LCD panel have been developed. The data drivers include shift registers, sample‐and‐hold circuits, and operational amplifiers, and drive LCD panels using a line‐at‐a‐time addressing method. To reduce the power consumption of the shift register, a dot‐clock control circuit has been developed. Using this circuit, the power consumption of the shift register has been reduced to 36% of that of conventional circuits. To cancel the offset voltage generated by the operational amplifier, an offset cancellation circuit for low‐temperature poly‐Si TFTs has been developed. This circuit is also able to avoid any unstable operation of the operational amplifier. Using this circuit, the offset voltage has been reduced to one‐third of the value without using the offset cancellation circuit. These data drivers have been connected to an LCD panel and have realized an SVGA display on a 12.1‐in. a‐Si TFT‐LCD panel.

誘導結合型プラズマにおけるアンテナ電流とプラズマパラメータの関係

Both the current flowing through an antenna coil and the voltage supplied to the coil were measured for Ar inductive coupled plasmas (ICP) at a pressure of 13 Pa. Since a large current flowed through the antenna coil even under no plasma condition, the difference of the antenna coil currents between under no plasma and ICP was measured by using the cancel circuit. Spatial distributions of the plasma density were also measured by Langmuir probes. The RF power dependence of the plasma density agreed to that of the antenna coil current when the cancel circuit was used. The radial distribution of the plasma density, np (r), had the peak below the antenna coil center. Positions of the charged particle generation in the plasmas were discussed based on np (r). The plasma density decreased as increasing the radial distance from the coil center. For the RF power of 150 W the decreasing rate was larger than that for the RF power of 300 W. The values of the coupling coefficient increased as increasing the RF power. The result could be explained based on the RF power dependence of np (r).

Video moire cancellation filter for high-resolution CRTs

The appearance of moire limits the performance of high-resolution cathode ray tubes (CRTs). Until now, cancellation circuits have used a small alternating image shift (wobble) to disguise moire, but these circuits introduce other artefacts like flicker. We present a novel solution for suppressing video moire with a specific non-linear filter. Advantages include simple digital video signal processing and negligible degradation of the image quality, even in graphics with very fine detail.

Improving the accuracy and operating range of quartz microbalance sensors by a purposely designed oscillator circuit

A method is presented to measure accurately the resonant frequency and to increase the functioning range of quartz microbalance sensors subject to heavy acoustic loading, such as encountered in in-liquid operation and with viscoelastic coating films. The method is based on an electronic circuit for the active cancellation of the crystal electrical capacitance, inserted in a phaselocked loop oscillator, which enables the tracking of the quartz series resonance with virtually zero error irrespective of the load. The principle is discussed, and experimental results confirming its successful application are presented.

画素間固定パターンノイズキャンセル機能内蔵対数変換形ＣＭＯＳエリア固体撮像素子

Logarithmic-converting CMOS area image sensors with an FPN cancel circuit, fabricated using a conventional CMOS process, have been developed. The sensors have 540 (H) × 148 (V) pixels, each with a logarithmic-converting circuit and a simple FPN cancel circuit. Their cells are 7 μm (H) × 21 μm (V). They output a signal with a strength logarithmically proportional to the integrated amount of photo current generated by incident light. They can therefore capture bright and dark objects at the same time without using a frame memory. This sensor should thus find application in consumer (digital still cameras, digital video cameras, and so on) and industrial products.

A 2-V CMOS 455-kHz FM/FSK demodulator using feedforward offset cancellation limiting amplifier

This paper presents a low-voltage low-power IF 455-kHz signal processor that contains a three-stage limiting amplifier and an FM/FSK demodulator. The limiting amplifier uses an on-chip feedforward offset cancellation circuit. The FM/FSK demodulator employs a quadrature detector that is composed of an on-chip phase detector and an external tank phase shifter. The demodulation constant is 20 mV/kHz with masimum /spl plusmn/10-kHz frequency deviation. The IF signal processor that consumes 2.3 mW from a single 2-V power supply demonstrates a high sensitivity of -72 dBm. It occupies an active area of 0.2 mm/sup 2/ using 0.6-/spl mu/m digital CMOS technology.

Techniques for input ripple current cancellation: classification and implementation [in SMPS

Switching power supplies, due to their high-frequency switching operation, draw a substantial amount of input ripple current. Such ripple current manifests itself as electromagnetic interference (EMI). Active and passive ripple cancellation methods have been proposed in the past. This paper discusses the cancellation methods, and classifies the basic circuit configurations for ripple current cancellation. The basis of discussion is a nullification process, which can be described effectively in terms of the ideal circuit element nullor. The initial focus is on differential-mode noise cancellation, but the basic technique can be applied equally to cancelling common-mode noise. The classification provides a clear guideline for synthesizing practical cancellation circuits. Both active and passive implementation examples are given and experimentally demonstrated.

誘導結合型プラズマにおける高周波電流測定の改善とその応用

Both the current flowing through an antenna coil and the voltage supplied to the coil were measured for Ar inductive coupled plasmas (ICP) at a pressure of 13 Pa. By using the cancel circuit we measured the difference of the antenna coil currents between no plasma load and ICP. The measurement system was improved in order to reduce both radio frequency (RF) noises and waveform distortions. The impedance is presented when the cancel circuit is used. A simple method to obtain the value of the coupling coefficient is presented. The current measured with the cancel circuit could be related to the plasma current much better than that without the cancel circuit. The values of the coupling coefficient increased as the RF power increased, and ranged between 0.3 and 0.5 in our experiment.

Circuit for microbolometer bias-heating cancellation

A new circuit for microbolometer bias-heating cancellation is described. The circuit is based on the equivalence between the electrical and thermal capacitance. A replica of the bias-heating effect is generated on the electrical capacitance and is used to effectively cancel the bias heating of the microbolometer. The cancellation is tunable.

Low IMD, antenna combined, circularly polarised,integrated antenna

The cancellation of inter-modulation distortion (IMD) using linearisation techniques has traditionally been performed at the amplifier. The authors present a circular patch antenna operating at 1.93 GHz, which also functions as a four way combiner and an IMD cancellation circuit.

Demonstration of a rapidly strain tuned Er^3+-doped fiber laser for sensitive gas detection

We describe a novel combination of a diode-pumped, wavelength-modulated Er(3+)-doped fiber laser light source with a sensitive noise cancellation circuit for detection of acetylene and ammonia. The laser tuning element, a fiber Bragg grating, was mounted in such a way that it could be strained controllably and rapidly, allowing noise cancellation techniques to be applied to the wavelength-modulated output of the fiber laser. The experimental setup is relatively simple and can be extended to other fiber laser wavelengths for which semiconductor lasers are not readily available by selection of a different fiber Bragg grating and gain medium.

新手法による誘導結合型プラズマのインピーダンス測定

We developed a new measurement system for the antenna current to obtain a plasma impedance that was hardly measured due to the low inductance of the antenna coil. When a conventional measurement system was used, the phase angle between the voltage and current was 81° for a high density Ar plasma (1011 cm-3 plasma density at 6.7 Pa). With new cancel circuit that subtracts the current flow to the coil inductance, the current was down to ten times smaller and the phase angle decreased to 54°. Both the power dissipation and the plasma density measured by the Langmuir probe were almost direct proportional to the current. It was also demonstrated theoretically that the new system is useful for the measurement of the impedance and power dissipation in plasmas.

A 450-Mb/s analog front end for PRML read channels

The high user densities and data rates supported by today's hard-disk drives (HDD) demand complex read channel ICs. High-performance analog front-end (AFE) circuits provide automatic gain control (AGC), programmable band limiting and pulse shaping prior to signal sampling and further processing of the data in the digital domain. A 450 Mb/s analog front-end, integrated into a 16/17 code rate EPR4 read channel, contains an AGC loop, which includes a programmable gain stage (PGA), an exponential variable-gain amplifier (VGA), a 7/sup th/-order 120 MHz lowpass filter (LPF), an active dc offset cancellation circuit, and digital feedback. Utilizing multilevel qualification and a variable loop time constant, the AGC acquires a 12 dB gain change within 5 data bytes. Thermal asperity (TA) and amplitude asymmetry compensation make the analog front-end ideally suited for magnetoresistive (MR) head-based applications. Implemented in 5V/3.3V dual voltage 0.35 /spl mu/ BiCMOS, the complete circuit occupies 2.29 mm/sup 3/ and dissipates 232 mW.

An active circuit for cancellation of common-mode voltage generated by a PWM inverter

This paper proposes an active common-noise canceler (ACC) that is capable of eliminating the common-mode voltage produced by a pulsewidth modulation (PWM) inverter. An emitter follower using complementary transistors and a common-mode transformer are incorporated into the ACC, the design method of which is also presented in detail. Experiments using a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-mode voltage in a 3.7 kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show that the ACC makes significant contributions to reducing a ground current and a conducted electromagnetic interference (EMI). In addition, the ACC can prevent an electric shock on a nongrounded motor frame and can suppress motor shaft voltage.

8-channel CMOS preamplifier and shaper with adjustable peaking time and automatic pole-zero cancellation

An 8-channel preamplifier-shaper circuit for use with detectors having a capacitance in the range 20–50pF has been designed in 1.2μ CMOS AMS technology. The shaper is designed so that the peaking time can be adjusted, by steps, in the range 200ns–2μs by simple digital control. The pole-zero cancellation circuit uses an original method of sensing the preamplifier feedback capacitor discharging current and producing an identical current to discharge the capacitance of the pole-zero cancellation circuit. The series noise resistance rs=415Ω has been measured (270Ω of which is the protection resistor). The input capacitance of the preamplifier is 10pF + the strays of the test box 10pF for a total of 20pF. The input PMOS transistor has a gm of 5mA/V (from simulation) at 210μA drain current. The cross-talk between channels is less than 1%.

Sustaining devices for stringed musical instruments

A sustaining device for prolonging the vibration of a string of a stringed musical instrument having a magnetic pickup means responsive to vibration of a string, and an electromagnetic string driver means to provide a magnetic drive force to the string. A cancellation circuit is provided for reducing electromagnetic feedback between the pickup and driver by adjusting the relative phase and amplitude between a first and second pickup signal and combining the signals so that the responses to electromagnetic interference cancel. One embodiment of the cancellation circuit includes a second electromagnetic driver that generates an amplitude-adjusted and phase-adjusted electromagnetic field to cancel electromagnetic interference. The driver may be a section of toroidal solenoid that is shaped so that its endpoles are in close proximity to the string for concentrating magnetic flux along the string. The strings are provided with electrical current which interacts with magnetic flux generated by the driver for driving the string in a second orthogonal plane of vibration. Electromagnetic interference between separate sustain devices is reduced by placing the components of each pickup means equidistant to each of the drivers. Automatic level control means is provided to each of a plurality of sustain devices to minimize the effects of magnetic damping on the strings. A hand-held sustaining device is provided with an encapsulating means for separating the driver from other elements of the device.