Gigahertz Bandwidth Research Articles

A 40-GHz-bandwidth, 4-bit, time-interleaved A/D converter using photoconductive sampling

GaAs photoconductive switches have been integrated with two parallel 4-bit CMOS analog-to-digital (A/D) converter channels to demonstrate the time-interleaved sampling of wideband signals. The picosecond sampling aperture provided by low-temperature-grown-GaAs metal-semiconductor-metal switches, in combination with low-jitter short-pulse lasers, enables the optically-triggered sampling of electrical signals with tens of gigahertz bandwidth at low to medium resolution. A pair of parallel sampling paths, one for sampling and the second for feedthrough cancellation, generate a differential held signal that is quantized by a low-input capacitance, high-speed flash A/D converter. Dynamic offset averaging is employed to improve converter linearity. An experimental time-interleaved two-channel A/D converter provides about 3.5 effective bits of resolution for inputs up to 40 GHz when tested at an optically-triggered sampling rate of 160 MHz. The sampling rate was limited by the available optical source. Each A/D converter channel operates up to a 640-MHz conversion rate, dissipates 70 mW of power, and occupies an area of 150 μm × 450 μm in a 2.5-V, 0.25-μm CMOS technology.

5-Gbit/s BER performance on an all fiber-optic add/drop device based on a taper-resonator-taper structure

We present an all fiber-optic add/drop device based on a taper-resonator-taper structure with improved characteristics. Several gigahertz bandwidths are observed using microspheres having diameters ranging from 30 to 50 /spl mu/m. Extinction ratios as high as 26 dB of the dropped channel are obtained due to nearly ideal coupling and phase matching between the fiber tapers and the small resonator. This is the first time that bit-error rate (BER) measurements have been performed on such couplers. For a device with an optical bandwidth of 3.8 GHz, the BER shows less than 2-dB penalty at 5 Gbit/s and no signs of an error floor.

Broadband detection capability of ZnTe electro-optic field detectors

We present our measurements of the broadband detection capability of copropagating electro-optic ZnTe field detectors for the characterization of free-space pulsed electromagnetic radiation. To demonstrate ultrawide detection bandwidth, radiation from both gigahertz and terahertz bandwidth pulsed microwave sources has been characterized. The high frequency limitation of the sensor is the first TO phonon resonance (5.31 THz). The ultrashort temporal resolution is demonstrated by the detection of a 177 fs (full width at half-maximum) pulse generated via THz optical rectification in 〈111〉 GaAs.

ADVANCED COMMUNICATIONS TECHNOLOGY SATELLITE (ACTS): DESIGN AND ON‐ORBIT PERFORMANCE MEASUREMENTS

The Advanced Communications Technology Satellite (ACTS), developed and built by Lockheed Martin Astro space for the NASA Lewis Research Center, was launched in September 1993 on the shuttle STS 51 mission. ACTS is a digital experimental communications test bed that incorporates gigahertz bandwidth transponders operating at Ka band, hopping spot beams, on-board storage and switching, and dynamic rain fade compensation. This paper describes the ACTS enabling technologies, the design of the communications payload, the constraints imposed on the spacecraft bus, and the measurements conducted to verify the performance of the system in orbit.

ADVANCED COMMUNICATIONS TECHNOLOGY SATELLITE (ACTS): DESIGN AND ON-ORBIT PERFORMANCE MEASUREMENTS

The Advanced Communications Technology Satellite (ACTS), developed and built by Lockheed Martin Astro space for the NASA Lewis Research Center, was launched in September 1993 on the shuttle STS 51 mission. ACTS is a digital experimental communications test bed that incorporates gigahertz bandwidth transponders operating at Ka band, hopping spot beams, on-board storage and switching, and dynamic rain fade compensation. This paper describes the ACTS enabling technologies, the design of the communications payload, the constraints imposed on the spacecraft bus, and the measurements conducted to verify the performance of the system in orbit.

MMIC internal electric field mapping with submicrometre spatial resolution and gigahertz bandwidth by means of high frequency scanning force microscope testing

High frequency scanning force microscope (HFSFM) testing enables, among other measurements, the probing of device internal electric potential distributions within monolithic microwave integrated circuits (MMICs) with both high spatial and temporal resolution. Two planar components of the electric field can be calculated from this data and their local distribution can be mapped. For the first time 2-D distributions of electric field components on an interdigital capacitor within an MMIC at frequencies up to 6 GHz were evaluated from HFSFM potential measurements, demonstrating the submicrometre spatial resolution and gigahertz bandwidth of this new MMIC internal electric field mapping technique

A quantum-well inversion channel heterostructure as a multifunctional component for optoelectronic integrated circuits

An approach to optoelectronic integration utilizing a universal heterostructure with a single GaAs quantum-well active region is presented. The inversion channel forms the basis of a heterojunction field-effect transistor, a lateral current injection laser, a field-effect modulator, and a waveguide photodetector by simple reconfiguration of the electrodes and device geometry. The fabrication technology has been developed for gigahertz bandwidth applications by utilizing ion implantation techniques for interdevice electrical isolation and surface planarization, and reactive ion-etching to realize a self-aligned transistor-based heterostructure. The design, fabrication, and characterization of various heterostructures are discussed in the context of optoelectronic integration and the implementation of ion implantation disordering to realize low-loss self-aligned waveguides for on chip signal routing. The ultimate performance of the devices using a GaAs quantum well is considered, as well as the development of this technology for improved performance using strained InGaAs wells.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Integrated optical differential amplifier with large dynamic range for gigahertz bandwidth electrical signals

An optoelectronic differential amplifier for gigahertz-bandwidth electrical signals using fiber optics and integrated optical devices is presented. In the amplifier presented the signal subtraction is done while still in the optical domain. The differential gain is a function of the electrical-to-optical and optical-to-electrical conversion factors. The common-mode rejection ratio of the differential amplifier at 1 GHz is greater than 30 dB. The common-mode rejection ratio depends on the time difference between the differential amplifier inputs. This device could be used as an integrated module in radar and communications systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Extremely low threshold current operation in 1.5- mu m MQW-DFB laser diodes with semi-insulating InP current blocking region

Threshold current operation of 1.5 mA was achieved for 1.5- mu m multiple-quantum-well distributed feedback (MQW-DFB) laser diodes (LDs) with semi-insulating current blocking layers entirely grown by metalorganic vapor phase epitaxy (MOVPE). Such low-threshold current is attained by reducing leakage current and mirror loss in the laser structure. The required bias current for achieving several gigahertz bandwidth is markedly reduced due to the enhanced differential gain and low threshold current. Due to the reduced lasing delay time in such low threshold LDs, up to 5-GHz zero-bias current modulation, with a clear eye opening, is successfully demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A novel integrated acoustooptic frequency shifter

An integrated optical frequency shifter that utilizes guided-wave acoustooptic Bragg diffractions in cascade from two tilted- and counterpropagating-surface acoustic waves is reported. The doubly and frequency-shifted diffracted light propagates in a fixed direction, but spatially resolved from the incident light, irrespective of the magnitude of frequency tuning. A device fabricated in a Y-cut LiNbO/sub 3/ planar waveguide has demonstrated desirable characteristics, including single-sideband suppressed-carrier properties, a frequency shift centered at 1 GHz, a tunable bandwidth of 165 MHz, a linear dynamic range greater than 41 dB, and high efficiency at the optical wavelength of 0.63 mu m. These preliminary results suggest that a compact integrated acoustooptic frequency shifter module capable of multigigahertz center frequency and gigahertz bandwidth can be realized in a common LiNBO/sub 3/ substrate 0.2 cm*1.0 cm*1.5 cm in size.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design of wide-band optical heterodyne balanced mixer receivers

The optical heterodyne balanced mixer, or dual-detector receiver, offers significant advantages over a single detector receiver. Balanced mixer receivers are particularly attractive for use in optical heterodyne communication systems because they conserve local oscillator power and cancel excess intensity noise present in the local oscillator. Simple circuit models that illustrate the noise performance, small signal gain, and bandwidth of a balanced mixer receiver are developed. A figure-of-merit for receiver noise performance is also derived. An example design of a gigahertz bandwidth optical heterodyne balanced mixer receiver and the techniques used to characterize near-quantum-limited receiver performance are discussed.

A Design and Packaging Technique for a High-Gain, Gigahertz-Band Single-Chip Amplifier

Equalizing amplifiers for gigabit optical fiber transmission systems requires a 65-dB gain (S21) with a gigahertz bandwidth. However, this gain has the potential to cause significant parasitic oscillation. Consequently, developing a useful stabilization design technique is a very important factor in attaining practical design. In this paper, stabilization design techniques are described for circuit configurations, packaging, and stability assessment. In addition, fabrication results of amplifier IC based on bipolar super self-aligned process technology (SST) and new wide-band high isolation package with coaxial-like 50-/spl Omega/ signal lines are also shown. A 65-dB gain, 1.3-GHz bandwidth single-chip amplifier has been successfully fabricated.

Measurements of transients in high-voltage systems

The constant call for increased measurement accuracy has resulted in a strong demand for recording instruments with a wider bandwidth and a higher sensitivity. The resultant use of recording instruments with gigahertz bandwidths for measurements in high-voltage (HV) systems has created a situation in which the distributed character of field-structure interaction needs to be considered. An overall view of this problem, including theoretical modeling and practical measurements, is presented.

Performance of a Correlator Filter in Betatron Tune Measurements and Damping on the NSLS Booster

A "compensated correlator filter", described by Kramer, et al.[1] has been used for measurement and damping of betatron oscillations in the NSLS booster. The filter consists of a zero-degree power splitter, a 180-degree splitter, a length of 7/8" air dielectric coaxial cable, and a short length of RG-58 cable. Connected to a beam position monitor, the output of the filter is proportional to the difference in transverse position of each bunch on subsequent turns. The useful bandwidth of the filter for damping rigid bunch oscillations extends from 10 MHz to 250 MHz, in contrast with the gigahertz bandwidth requirements for stochastic cooling, for which the filter was originally proposed. Attenuation of all rotation harmonics in this bandwidth is 40-60 dB.

A Review of Single Transient Oscillographic Recorders with Gigahertz Bandwidth

This paper has reviewed the status of gigahertz bandwidth single transient oscillographic recording instruments and their CRT's. I would like to emphasize again the ideal recording instrument from a fusion experiments, target diagnostics, point of view shown in figure 2. The French work appears to be addressing this concept most closely. We are waiting to see and evaluate the actual recording instruments that emerge during the next few years.

Gigahertz bandwidth measurements of photodetectors and fibers using picosecond pulses generated by semiconductor lasers

A picosecond variable pulse width method has been found to be very useful in the bandwidth determination of Gbit/s photodetectors and fibers. Bandwidths up to 5 GHz have been measured with this technique using picosecond pulses generated from a semiconductor laser.

Gigahertz bandwidths in multimode, liquid-core, optical fibre waveguide

An attenuation of 7 dB/km has been achieved over kilometre lengths of liquid-core, multi-mode optical fibre waveguide. The measured pulse dispersion depends on the mode distribution launched and on mode conversion which is a function of bend radius. Using a laser source a dispersion corresponding to a bandwidth ≈ 1 GHz has been achieved and does not appear to be limited by fibre imperfections.