Narrow-band Amplifier Research Articles

InAs HEMT narrowband amplifier with ultra-low power dissipation

The design, fabrication and performance of a prototype narrowband amplifier using InAs-channel HEMTs are reported. The amplifier, which is realised on an RT/Duroid circuit board with a combination of transmission lines and lumped components, is intended for a long-life battery-powered application. The two-stage amplifier has 20 dB of gain with a bandwidth of 4% in S-band and dissipates a total power of only 365 µW.

A monolithically integrated optical heterodyne receiver

We demonstrate a monolithically integrated optical heterodyne receiver consisting of an input fiber waveguide, a single frequency distributed Bragg reflector (DBR) laser, a multimode interferometer-based 3-dB coupler, and a pair of semiconductor optical amplifier (SOA)/p-i-n modules using a single epitaxial growth based on asymmetric twin-waveguide (ATG) technology. The input signal was coupled into a fiber waveguide and mixed with the DBR local oscillator laser through the 3-dB coupler, and then coupled into the SOA/p-i-n modules for detection. Using this monolithically integrated optical receiver with a wide-band rectifier narrow-band amplifier receiver, a 3-GHz frequency modulated coherent analog optical link is demonstrated.

A 16-GHz linear analog heterodyne RF optical link employing a WIRNA receiver

We demonstrate a 16-GHz analog heterodyne optical link operating at 1.55-/spl mu/m wavelength with a noise figure of (40/spl plusmn/1) dB and spurious-free dynamic range of (108/spl plusmn/2) dB /spl middot/ Hz/sup 2/3/. The wide-band rectifier narrow-band amplifier receiver architecture is employed with improvements over previous work to minimize the number of components in the link. The link performance is compared with that of an intensity modulated direct detection link. We show that further improvements in noise figure can be realized using balanced photodetector receivers. To our knowledge, this is the highest reported bandwidth of a linear analog optical link reported to date, and shows the advantages of employing heterodyne versus direct detection for such applications.

Matched coupled microstrip transistor amplifier methodology

In this paper, we present a generalized methodology for synthesizing narrowband amplifiers in coupled microstrip systems and detail a novel narrowband amplifier in a three-coupled microstrip topology utilizing chip capacitors for matching networks. The purpose of such a configuration is to validate the synthesis of microwave amplifiers in coupled microstrip technology (the ground plane being common to many fabrication technologies) where the planarity inherent to coplanar designs alleviates the need for vias, thereby reducing fabrication cost.

Design of narrowband amplifiers with conditionally stable transistors

AbstractA technique to design narrowband amplifiers by using conditionally stable transistors is presented. The proposed analytical approach allows us to design lossless matching networks, by providing power matching at one port and minimum mismatch at the other port. The use of this technique leads to high gain as well as proper stability margins. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 208–210, 2001.

Millimeter-wave long-wavelength integrated optical receivers grown on GaAs

Compact monolithically integrated narrow-band photoreceivers with a high responsivity at millimeter-wave frequencies were realized. In these receivers, a 1.3-1.55-/spl mu/m wavelength In/sub 0.53/Ga/sub 0.47/As p-i-n photodiode, grown lattice relaxed on GaAs, is conjugately matched to a two-stage narrow-band amplifier based on 0.15-/spl mu/m GaAs based dual-gate PHEMTs. A first receiver, designed for operation around 42 GHz, obtains an optical responsivity of 7 A/W. This is a 38-dB increase in comparison with the measured responsivity of a terminated p-i-n photodiode. For a second receiver, operating at 58 GHz, a responsivity of 2.5 A/W is obtained. These receivers are, to our knowledge, the first high-gain millimeter-wave long-wavelength photoreceivers monolithically integrated on GaAs. Their high responsivity makes them attractive for use in various microwave and millimeter-wave-over-fiber applications.

Self-aligned GaAs JFETs for low-power microwaveamplifiers and RFICs at 2.4 GHz

Self-aligned GaAs JFET narrowband amplifiers operating at 2.4 GHz were designed and fabricated with both discrete WETS as a hybrid amplifier and as RFICS. Enhancement-mode JFETs were used in order to be compatible with complementary digital logic. Hybrid amplifiers achieved 8-10 dB of gain at 2.4 GHz and 1 mW DC bias level. The RFIC achieved 10 dB of gain at 24 GHz and 2 mW DC bias level.

Very high gain, high sensitivity, 40 GHz narrowbandphotoreceiver for clock recovery

A 40 GHz photoreceiver has been implemented by cascading on a single alumina substrate a fast side-illuminated AlGaInAs/InP pin photodiode, and three narrow-band amplifier chips, based on a 0.2 µm gate length GaAs pHEMT technology. The package was especially designed to suppress parasitic cavity-resonances. The photoreceiver current-gain is 57 dB, and the average input noise is < 30 pA/√Hz over the –3 dB bandwidth of 40.4 – 41.4 GHz. This is believed to be the highest photoreceiver gain ever reported in a single compact metal package at such a high frequency.

Er-doped integrated optical devices in LiNbO/sub 3/

The state-of-the-art of Er-doped integrated optical devices in LiNbO/sub 3/ is reviewed starting with a brief discussion of the technology of Er-indiffusion. This technique yields high-quality waveguides and allows a selective surface doping necessary to develop optical circuits of higher complexity. Doped waveguides have been used as single- and double-pass optical amplifiers for the wavelength range 1530 nm</spl lambda/<1610 nm. If incorporated in conventional, lossy devices loss-compensating or even amplifying devices can be fabricated. Examples are an electrooptically scanned Ti:Er:LiNbO/sub 3/ waveguide resonator used as an optical spectrum analyzer and an acoustooptically tunable filter used as a tunable narrowband amplifier. Different types of Ti:Er:LiNbO/sub 3/ waveguide lasers are presented. Among them are free running Fabry-Perot lasers for six different wavelengths with a continuous-wave (CW)-output power up to 63 mW. Tunable lasers could be demonstrated by the intracavity integration of an acoustooptical amplifying wavelength filter yielding a tuning range up to 31 nm. With intracavity electrooptic phase modulation modelocked laser operation has been obtained with pulse repetition frequencies up to 10 GHz; pulses of only a few ps width could be generated. With intracavity amplitude modulation Q-switched laser operation has been achieved leading to the emission of pulses of up to 2.4 W peak power (0.18 /spl mu/J) at 2 kHz repetition frequency. Distributed Bragg reflector (DBR) lasers of emission linewidth /spl les/8 kHz have been developed using a dry-etched surface grating as one of the mirrors of the laser resonator. Finally, as an example for a monolithic integration of lasers and extracavity devices on the same substrate, a DBR-laser/modulator combination is presented.

Complementary Hfet Technology for Low-Power Mixed-Mode Applications

AbstractDevelopment of a complementary heterostructure field effect transistor (CHFET) technology for low-power, mixed-mode digital-microwave applications is presented. An earlier digital CHFET technology with independently optimizable transistors which operated with 319 ps loaded gate delays at 8.9 fJ is reviewed. Then work demonstrating the applicability of the digital nJFET device as a low-power microwave transistor in a hybrid microwave amplifier without any modification to the digital process is presented. A narrow band amplifier with a 0.7 × 100 μm nJFET as the active element was designed, constructed, and tested. At 1 mW operating power, the amplifier showed 9.7 dB of gain at 2.15 GHz and a minimum noise figure of 2.5 dB. In addition, next generation CHFET transistors with sub 0.5 μm gate lengths were developed. Cutoff frequencies, ftof 49 GHz and 11.5 GHz were achieved for n- and p-channel FETs with 0.3 and 0.4 μm gates, respectively. These FETs will enable both digital and microwave circuits with enhanced performance.

Single-wavelength dispersion measurement for multiple-fiber section connected with narrow-band optical amplifiers

This paper deals with the chromatic dispersion measurement of multiple-fiber sections concatenated with narrow-band linear amplifier repeater(s). This scheme sinusoidally modulates the phase, not the light amplitude, at the transmitter in order to suppress undesirable nonlinear effects. At the receiver, relative amplitude of transformed intensity modulation directly indicates the dispersion value for the entire span of the multiple-fiber section. The limit of measurability is analyzed, and an experimental demonstration is presented.

High power single mode radiation by narrowband amplification of a diode laser

A laser system is described which uses a modeless laser as a narrowband amplifier to pulse amplify the output of a c.w. single mode diode laser. A power gain of 10 8 was observed leading to output pulses of 120 kW peak power at 10 Hz repetition rate. The pulse amplified linewidth was measured to be less than 330 MHz. The extension of the system to produce higher powers and other wavelengths is briefly discussed.

Signal-to-noise ratio of thermoacoustic enhanced photoacoustic spectrometers

The quality factor, Q, of plane or radial wave resonators can be increased and controlled using thermoacoustics. When such a resonator is used in photoacoustics, a laser beam passes through it and sound is produced when light absorption occurs. Sound amplitude is proportional to the coefficient for light absorption, to the resonator Q, and to the laser beam power. Traditionally, resonator dimensions have determined both the coupling strength of the laser beam to a particular mode and the quality factor. High coupling strength is desirable, but implies use of a narrow resonator where most of the interior is filled with laser. On the other hand, high Q traditionally implied need for a wide resonator. Thermoacoustics can be used to increase the Q of the narrow resonator to optimize the acoustic signal. Our theory and measurements show that the thermoacoustically enhanced photoacoustic spectrometer can be viewed as an analog narrow-band amplifier for sound where the resonance frequency is f0, the bandwidth is f0/Q, the gain is Q, and the signal-to-noise ratio for discrimination against Gaussian acoustic noise in the resonator is Q1/2. [Work supported by the EPA, ONR.]

Calibrated measurements and nonlinearity compensation of narrowband amplifiers

A vectorial nonlinear-network analyzer (VNNA) is absolutely calibrated in amplitude and phase for narrowband measurements of nonlinearities. Calibration is performed with a reference generator, characterized with a calibrated sampling oscilloscope. The reference signal, consisting of an upconverted baseband signal, is optimized for high signal-to-noise ratio measurements. Using the calibrated VNNA, narrowband amplifiers can be measured, enabling compensation of intermodulation and crossmodulation.

Variable impedance tuner for MMIC's

A monolithic structure is presented for the tuning of MMIC's. With this tuner, either process deviations can be compensated or circuit parameters can be altered to meet different requirements. Measured results of a realized tuner agree well with the simulated model. Key design parameters are listed and a theoretical application for a narrow band amplifier at 27 GHz is simulated. >

Static and dynamical characteristics of narrow-band tunable resonant amplifiers as active filters and receivers

The static and dynamical characteristics of semiconductor narrowband tunable resonant optical amplifiers as active filters and receivers are theoretically studied. Device performance at different cavity length, electrical bias level, incoming signal level, frequency detuning, and signal bandwidth is calculated for both amplitude-shift keyed and frequency-shift keyed input. Nonlinear dynamical effects under high-Q conditions and high input power are also discussed. Through the coupled field and carrier dynamics, the amplifier response can be monitored by the amplifier terminal voltage. The calculations are compared with experimental results where the amplifier is used as tunable receiver. >

CW and pulse Doppler diagnostic system

In an interlaced pulse-echo and range-gated Doppler system, an ultrasound transmitter generates a train of constant repetition rate echo pulse interlaced with a Doppler pulse train of plural bursts. The time duration between each burst and the preceding range gate opening is held constant while the time to the successive range gate opening is automatically varied to provide a continuously variable PRF tracking of the console range gate depth setting. The power of the transmitted signal is internally varied in the same sense and the cutoff frequency of the receiver low pass tracking filters is varied in the opposite sense to optimize signal-to-noise ratio at various tissue inspection depths. Selectable turnable high pass filters normalized to low velocity roll-off eliminate artifact for peripheral or central vascular probes. The detection system operates in quadrature and includes a synchronous demodulator and a peak detector, and a level detector operative on peak detected signals. Transducer probes interchangeably usable in the system include within each probe a narrow band amplifier critically turned to the respective probe crystal to provide further S/N ratio improvement. The system is operable in CW or pulsed Doppler modes dependent on switch setting on the split crystal probe.

Performance of a WDM network based on stimulated Brillouin scattering

The use of stimulated Brillouin scattering as a tunable narrowband amplifier to demodulate, amplify, and select channels in a densely packed WDM (wave-division multiplexed) network is discussed. A 128-channel system configuration is tested with channel separation as small as 1.5 GHz and error rates below 10/sup -10/. Direct FSK (frequency-shift-keyed) modulation of AlGaAs lasers and direct detection receivers are used. The experimental margin and noise analysis indicate that a 1000-channel system can be constructed with only these same components.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical demodulation and amplification of FSK signals using AlGaAs lasers

Stimulated Brillouin scattering is used as a narrowband amplifier to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s. Gain of as much as a factor of 1000 is obtained for a pump power of 12mW. Both pump and signal lasers are simple AlGaAs lasers.

Noise factor of resonant amplifiers with distributed interaction

The problem of electron beam shot and thermal noise conversion in resonant systems with distributed interaction is solved in a self-consistent formulation. Expressions are obtained for output oscillation amplitude and phase fluctuation spectra. The noise figure is minimized. The perspectives for developing narrow-band low-noise amplifiers based on such systems are discussed.