A 19.7 MHz, Fifth-Order Active-RC Chebyshev LPF for Draft IEEE802.11n With Automatic Quality-Factor Tuning Scheme

A fifth-order LPF with a quality factor (Q) tuning circuit has been implemented for draft IEEE802.11n in a 0.13 CMOS technology. The proposed Q tuning technique realizes a low-power 19.7 MHz, active-RC Chebyshev LPF. The filter has dB gain, 30 nV/Hz^1/2 input-referred noise, 113 dBmuV input , P 1dB,draws 7.5 mA current from 1.5 V supply, and occupies an area of 0.2 mm².     

Quantum-well SEED optical oscillators

Oscillation at 110 MHz in a GaAs-GaAlAs quantum-well SEED (self-electrooptic effect device) optical oscillator is considered. Optimization of device length and optical pump wavelength for high-frequency oscillation is discussed. Frequency tuning is obtained by adjusting the oscillator bias voltage or optical pump power, and the oscillator can be injection locked to modulated optical signals. Frequency fluctuations caused by perturbative Gaussian noise and 1/f frequency noise are observed; the 1/f noise in an 8.5-MHz oscillator limited the minimum frequency variance to 230 Hz²     

Maximum dynamic range operation of a microwave external modulationfiber-optic link

We fully analyze the analog performance of an external modulation fiber-optic link. We express relevant figures of merit-including gain, noise figure, third-order intermodulation distortion, AM compression, and dynamic range-in terms of the microwave scattering matrices of the modulator and detector circuits, and we predict the modulator bias condition promoting optimum link performance. Our predictions match the measured gain, noise figure, and dynamic range of an experimental 870-930 MHz external modulation fiber-optic link. Maximum spurious-free dynamic range-77 dB·MHz^2/3 (117 db·Hz^2/3 )-occurs when the modulator is biased at its halfwave voltage, where the optical throughput is nearly pinched off     

Effect of laser phase noise in Sagnac interferometers

A theoretical analysis of the responsivity and the noise caused by backscattering in a Sagnac interferometer used as a sensor for reciprocal measurands, such as acoustic waves, is presented. Both Rayleigh backscattering and reflections from splices are taken into account. The noise power is found to increase proportionally to the source coherence time, and a noise equivalent phase shift in the range of 0.1×10^-6 rad r.m.s./Hz^1/2 is predicted for typical fibers and diode lasers. Experimentally, a noise equivalent phase shift of 2.5×10^-7 rad r.m.s./Hz^1/2 at 10 kHz was observed, with a detector current of 3 μA     

An ultrasonic fiber-optic hydrophone incorporating a push-pulltransducer in a Sagnac interferometer

A theoretical and experimental analysis of a push-pull acoustic transducer incorporated in a Sagnac interferometer is presented. The transducer is optimized for detection of ultrasonic signals in the frequency range 0.4-1.5 MHz. Two different configurations are investigated. In one, the sensing fiber forming the transducer constitutes the total loop length, and in the second an additional delay coil is included in the middle section of the Sagnac loop. In the latter we demonstrate experimentally noise-equivalent pressures of 36-43 dB re. 1 μPa/Hz^1/2 in the frequency range 0.4-1.0 MHz. An approximate theoretical model is presented, and we obtain reasonable agreement between theory and experiment for both the frequency-dependent noise equivalent pressure and the directional responsivity of this push-pull acoustic fiber-optic sensor     

Injection-locked 1.55 μm VCSELs with enhanced spur-free dynamicrange

Injection locking is demonstrated to improve the analogue performance of long wavelength VCSELs. The third-harmonic spur-free dynamic range was improved by 9 dB/Hz^2/3 to be 93 dB/Hz^2/3, and the modulation bandwidth was increased twofold     

Broad-band electronic linearizer for externally modulated analogfiber-optic links

Linearization of analog fiber-optic links using a novel CMOS linearization circuit is reported. A 17-dB suppression of the third-order intermodulation product (IMP3) has been achieved at the modulation index of 49.6 % and over a broad-band frequency range from dc to 1.3 GHz. In an experimental link with a noise floor of -124 dBm/Hz, the spurious free dynamic range (SFDR) is improved by 14 dB from 85 dB/Hz^2/3 to 99 dB/Hz^2/3     

A BiCMOS front-end system with binary delay line for capacitivedetector read-out

As part of the entire readout chip, a low-power high-gain transresistance amplifier has been developed, followed by a high-speed, low-power small offset comparator and a binary delay line. The amplifier is balanced, fully differential in circuit topology, and symmetrical in layout, making it radiation tolerant and relatively insensitive to varying magnetic fields. Also, the comparator is fully symmetrical with a balanced input stage. Before irradiation (pre-rad) the transresistance amplifier has a measured differential gain of 110 mV/4 fC, an average 10/90% rise time (t_10/90%) of 20 to 50 ns depending on the bias conditions, a noise figure of 433⊕93.(C_t)^1.08 (where the symbol ⊕ stands for √(()²+() ²)) electrons (e^-), and a power consumption of 750 μW. The comparator uses bipolar transistors in the regenerative stage resulting in a small offset, a sensitivity <1.5 mV, and a power consumption of ≈350 μW at 40 MHz. The maximum pre-rad frequency at which the comparator is still functioning correctly is ≈100 MHz. Pre-rad, the binary delay line has a delay of 2.1 μs at 40 MHz and a power consumption of ≈450 μW/channel for a four-channel design. The complete readout channel-amplifier, comparator, and binary delay line-consumes ≈1.5 mW. The entire readout system was implemented in the radiation-hard 0.8-μm SOI-SIMOX BiCMOS-PJFET technology of DMILL     

CO2pulsed laser radiation tellurium detectors

Subnanosecond detectors and beam monitors for pulsed CO2laser radiation using the photon drag and optical rectification effects in tellurium are presented. Tellurium devices at 10.6 μ have a response of the order of 80 μV/kW . cm^-2with an NEP of8 times 10^{-4}W . Hz^1/2andD*of 500 cm . Hz^1/2/W which is superior to commercially available photon drag detectors and monitors. It is also expected and experimentally demonstrated that the responsivities of large area monitors can be multiplied by cutting the original area into multi-element strips and electrically connecting them in series.     

Interfaces for high speed fiber-optic links: analysis andexperiment

An analysis of directly and externally modulated fiber-optic links is presented. The theoretical analysis is based on the signal flow diagram of the interface circuits to the laser diode, Mach-Zehnder electro-optic modulator, and p-i-n photodiode. System parameters such as gain, noise figure, two-tone intermodulation distortion, and spurious free and compression dynamic range are expressed as a function of frequency and operating point of the laser and external modulator. Two directly and externally modulated fiber-optic links were designed and fabricated to verify the analytical models. The direct modulation FO link was developed at the Ku-band (11.6-12.4 GHz), whereas the external modulation link was at L-band (875-925 MHz). Spurious-free dynamic ranges of 95.8 dB Hz^2/3 and 113 dB Hz ^2/3, respectively, were achieved. The predictions based on the analytical models match the measured results     

Molecular-beam growth of homoepitaxial InSb photovoltaic detectors

Molecular-beam epitaxy has been used for the first time to fabricate np junctions in InSb grown onto p-type InSb (100) substrates. Diodes formed by the epitaxial growth of a silicon-doped layer on undoped homoepitaxial material exhibited a bulk generation-recombination-limited R₀A value of 10⁵ Ω cm² and D_λpk * of 3×10¹² cm Hz^1/2 W^-1 at liquid nitrogen temperature     

HgCdTe photoconductive detector array

An Hg0.8Cd0.2Te photoconductive array of 200 elements has been developed. The array has uniform detectivity and the mean value of D^*(12 µm, 1000, 1) field of view (FOV) 50° at 77 K is 3.2 × 10¹⁰cm. Hz^1/2. W^-1. The array was successfully fabricated under severe control of thermal flow during crystallization, carrier control by doping of indium impurity, and assembly of four chips each with 50 elements.     

Temperature Dependence of High Frequency and Noise Performance of Sb-Heterostructure Millimeter-Wave Detectors

The temperature dependence of the microwave and noise performance of zero-bias Sb-heterostructure backward diodes for millimeter-wave detection have been investigated experimentally. Both the junction capacitance and junction resistance were found to decrease with decreasing temperature, while the intrinsic cutoff frequency and sensitivity are observed to increase as the temperature is lowered. A simple physical model that captures these effects is described. The directly measured voltage sensitivity at 50 GHz for a 2times2 mum ² device increased from 3650 V/W at room temperature to 7190 V/W at 4.2 K. The measured noise equivalent power (NEP) decreased from 4.2 to 0.2 pW/Hz^1/2 as the temperature was lowered from 298 K to 4.2 K when driven from a 50- Omega source. Based on the measured RF sensitivity, S-parameters, and noise spectrum, a NEP of 0.3 pW/Hz^1/2 is projected for room-temperature operation at zero bias using a conjugately matched RF source     

Monolithic silicon mosaics for far-infrared imaging

Monolithic detector mosaics were constructed for image sensing at wavelengths from three to 30 µm. The mosaics use impurity photoconduction in silicon to sense infrared radiation. Operation in the 25 to 40°K temperature range is obtained with closed-cycle cooling. Photosensor elements, spaced on 32 mil centers, are formed by solid-state diffusion, and a junction diode is constructed in series with each photoresistor to reduce crosstalk. The integrated 30-by-30 mosaics have crossedX-Yelectrodes for direct-wire readout of picture elements. Performance of individual elements is described. At 25°K, a detectivity of 1 × 10⁸cm Hz^1/2/W per element is found using 10.6 µm CO2laser radiation. The quantum efficiency at 10.6 µm is about 7 percent, and the response time is observed to be less than 0.2 µs. Uniformity and crosstalk data on prototype arrays are presented, and the integration of these arrays with cryogenic amplifier and scanning circuits is discussed.     

一种适用于传感器信号检测的斩波运算放大器

提出一种适合传感器微弱信号检测应用的全差分低噪声、低失调斩波运算放大器。采用两级折叠共源共栅运放结构,基于斩波稳定及动态元件匹配技术,通过在运放低阻节点的电流通路上添加斩波开关的设计方式,增加了运放的输入信号带宽和输出电压摆幅。芯片采用TSMC 0.18μm 1P6MCMOS工艺实现。测试结果表明,在1.8V电源电压,25kHz输入信号和300kHz斩波频率下,斩波运放输入等效失调电压小于120μV,在10Hz～1kHz之间,输入等效噪声为5nV/Hz^1/2,最高开环增益为84dB,单位增益带宽为4MHz。     

A compact fiber-optic magnetometer employing an amorphous metalwire transducer

A compact fiber-optic magnetometer constructed using a short piece of amorphous metal wire (5-cm long×100-μm diameter) as the magnetostrictive transducer is discussed. The inherently large ratio of length to cross-sectional area results in a low demagnetization along the axial direction. A magnetostrictive constant of 5×10^-5 /Oe², which is 10-50 times larger than the reported values for transducers made from Metglas ribbons, was measured. Minimum detectable magnetic fields on the order of 10^-5 Oe/Hz^1/2 at 1 Hz were achieved using a 5-cm-long sensing fiber     

32×32 ultraviolet Al0.1Ga0.9N/GaN p-i-nphotodetector array

We report the fabrication and performance of a 32×32 Al_0.1Ga_0.9N-GaN ultraviolet p-i-n photodetector array. The devices exhibit very low dark current, the mean dark current density is ~4 nA/cm² at 5-V reverse bias, and the dark current distribution is very uniform (~98% of the devices exhibit dark current density <90 nA/cm²). Owing to the design of the p-Al_0.13Ga_0.87N window layer, the external quantum efficiency is as high as 72% at 357 nm. The photocurrent distribution is also presented. The detectivity is estimated to be as high as 8×10 ¹⁴ cm·Hz^1/2·W^-1     

Room-Temperature p-n-p AlGaAsSb–InGaAsSb Heterojunction Phototransistors With Cutoff Wavelength at 2.5 $mu$ m

Novel p-n-p AlGaAsSb-InGaAsSb heterojunction phototransistors (HPTs) grown by solid-source molecular beam epitaxy have been proposed and demonstrated. The p-n-p phototransistor structure provides a higher emitter injection ratio than its n-p-n counterpart, due to the large conduction band offset and almost continuous valence band edges between InGaAsSb and AlGaAsSb quaternary alloys. The resulting HPT devices exhibit high responsivities under a bias voltage above 0.3 V. A high room-temperature spectral responsivity of 2984 A/W is achieved at 2.24 mum, corresponding to an optical gain of 1652. The 50% cutoff wavelength of spectral photoresponse at room temperature is 2.50 mum. A room-temperature specific detectivity (D^*) of 8.3times10 ¹¹ cm middot Hz^1/2/W is obtained     

Uncooled InAs-GaSb type-II infrared detectors grown on GaAssubstrates for the 8-12-μm atmospheric window

We report on the growth and characterization of type-II infrared detectors with an InAs-GaSb superlattice active layer for the 8-12-μm atmospheric window at 300 K. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. Photoconductive detectors fabricated from the superlattices showed 80% cutoff at about 12 μm at room temperature. The responsivity of the device is about 2 mA/W with a 1-V bias (E=5 V/cm) and the maximum measured detectivity of the device is 1.3×10⁸ cm.Hz^1/2/W at 11 μm at room temperature. The detector shows very weak temperature sensitivity. Also, the extracted effective carrier lifetime, τ=26 ns, is an order of magnitude longer than the carrier lifetime in HgCdTe with similar bandgap and carrier concentration     

New digital closed-loop processor for a fiber-optic gyroscope

An all-digital closed-loop (ADCL) signal processor is developed for optically open-loop fiber-optic gyroscope. The processor is designed to provide high performance of more than 30 bits of phase resolution over 2π and unlimited measurement range. The random walk of the processor was measured to be about 0.57 μrad/Hz^1/2