Showing papers on "Amplifier published in 1993"

Method and apparatus for providing periodic subscription television services

Abstract: A method and apparatus of providing periodic subscription television services where a microprocessor (300) controls a service denying switch (389) and a high frequency amplifier (387) such that service may be denied using the service denying switch (389) or the high frequency amplifier (387). In addition, the high frequency amplifier (387) may be set by the microprocessor (300) at various amplitude levels depending upon the number of television receivers and VCR's at the subscriber location. Also, the high frequency amplifier (387) may include bandpass filter circuits under microprocessor control for limiting service to the subscriber.

Dual mode amplifier with bias control

Abstract: A dual mode transmitter with bias control is described wherein an RF signal from a system modulator is fed to a gain control circuit, which can be either a voltage controlled amplifier or attenuator. The ultimate transmitter output power level depends on the attenuation/gain of the gain control circuit. The output signal from the gain control circuit is fed to a driver amplifier which amplifies the signal and feeds it to a power amplifier circuit, which may be comprised of several stages of bipolar transistors or GaAs FETs. The modulated signal to be transmitted is then fed from the power amplifier circuit through a coupler to an antenna terminal. The coupler is connected to an RF detector and is used for RF level monitoring. The Rf level signal from the RF detector is applied to a comparator circuit. An improved combination is provided by incorporating a bias control circuit. A Vpwr signal is applied as one input to the bias control circuit and a mode signal is applied as the other input. When the mode signal is "on" or present it signifies that the digital transmission mode is to be employed. When the mode signal is " off" or at zero level, it indicates that the analog transmission mode is to be employed. The bias control circuit provides three bias signal outputs, Vb1 applied to the driver amplifier, and Vb2 and Vb3, applied to the power amplifier. The levels of Vb1, Vb2 and Vb3 are varied for the analog and digital transmission modes.

Method and apparatus for enhancing an operating characteristic of a radio transmitter

Abstract: In a radio transmitter (100) that includes a power amplifier (104) and an antenna (106), a method for enhancing an operating characteristic of the radio transmitter (100) can be accomplished in the following manner. The power amplifier (104) provides a signal (113) to a variable matching network (111), wherein the signal (113) comprises energy to be radiated by the antenna (106). The variable matching network (111) couples the signal (113) to a sampler (112) that is operably coupled to an output of the variable matching network (111 ) and the antenna (106). The sampler (112) samples a forward component (114) and a reflected component (115) of the signal (113). The radio transmitter (100) processes the sampled forward and reflected components (116, 118) to produce a feedback control signal (120). The feedback control signal (120) is used to adjust the variable matching network (111 ), such that an operating characteristic of the radio transmitter (100) is enhanced.

High-power, strained-layer amplifiers and lasers with tapered gain regions

Abstract: Laterally tapered gain regions designed to accommodate the diffraction of narrow single-lobe beams that have been used in both optical amplifiers and lasers are described. Amplifier output power of 3.5 W with 3.1 W in a 1.05 times diffraction-limited lobe and laser output power of over 4 W with approximately half the power in a 1.7 times diffraction-limited lobe have been achieved. >

Signal processing for microcalorimeters

Abstract: Most of the power in the signals from microcalorimeters occurs at relatively low frequencies. At these frequencies, typical amplifiers will have significant amounts of 1/f noise. Our laboratory systems can also suffer from pickup at several harmonics of the AC power line, and from microphonic pickup at frequencies that vary with the configuration of the apparatus. We have developed some optimal signal processing techniques in order to construct the best possible estimates of our pulse heights in the presence of these non-ideal effects. In addition to a discussion of our laboratory systems, we present our plans for providing this kind of signal processing in flight experiments.

High-Power GaAs FET Amplifiers

Abstract: Introduction and basic theory high-power GaAs FETs computer-aided design of GaAs FET power amplifiers high-power GaAs FET amplifier design thermal effects and reliability combining techniques systems applications of GaAs FET power amplifiers.

Current-mode Circuits From A Translinear Viewpoint: A Tutorial

Abstract: This chapter will describe many examples of translinear circuits, which come as close to true current-mode operation as any circuit can. These circuits were based on the remarkable fact that the trans conductance of a BJT is linearly proportional to its collector current, hence the term trans-linear. Further, the word carried with it the connation of “lying somewhere between familiar home territories of the linear circuit and the formidable terrains of the nonlinear”. Indeed, in addition to their well-known application in multipliers and other nonlinear circuits, translinear concepts are found embedded in many contemporary linear integrated circuits. The most familiar example is the current mirror; the classical four-transistor Class-AB output stage of almost any op-amp can be viewed in translinear terms; the current conveyor, used in the recently-rediscovered current-feedback amplifier, is yet another example.

Method and apparatus for reducing the peak-to-average power in multi-carrier RF communication systems

Abstract: Therefore a method and apparatus for controlling a linear amplifier processing a plurality of carrier signals of a multi channel carrier system alters the phases of one or more sources of the multi-channel signals in response to a detected peak envelope power or of a peak to average power ratio at regular scheduled intervals This reduces the peak envelope power to average envelope power ratio and enables the reduction in the power rating required by the amplifiers handling the multi-channel signal

Two-stage integrated SQUID amplifier with series array output

Abstract: A two-stage integrated DC superconducting quantum interference device (SQUID) amplifier has been fabricated which uses a compact series array of 100 DC SQUIDs as the readout device for a low-noise single SQUID. The output noise is dominated by the amplified noise of the input SQUID and substantially exceeds the input noise of a good room-temperature preamp. The input stage is a low-inductance double-loop SQUID with energy sensitivity of approximately 30-h (equivalent flux noise phi /sub n/ approximately=0.3 mu phi /sub 0// square root Hz), with an input transformer having input inductance L/sub in/ approximately=0.25 mu H and net coupling to the SQUID of k/sup 2/ approximately=0.1. The bandwidth extends from DC to about 390 kHz. The series array has an output voltage swing of 3-4 mV, providing a dynamic range of over 50 dB at full bandwidth. The results suggest the general utility of series SQUID arrays as readout devices for SQUIDs. >

Operating characteristics of a high-power monolithically integrated flared amplifier master oscillator power amplifier

Abstract: High-power monolithically integrated flared amplifier master oscillator power amplifiers (MFA-MOPAs) that operate up to 2 W continuous wave (CW) in a single diffraction-limited lobe have been fabricated. The spectral output of the MFA-MOPA is single longitudinal mode with a side-mode suppression ratio greater than 25 dB. Several operating characteristics of the MFA-MOPA, including the beam astigmatism, amplifier gain saturation, linewidth, far-field extinction ratio, and beam quality metrics are investigated and discussed. >

Optical Fiber Amplifiers: Design and System Applications

Abstract: Manufacturing of active fibers properties of rare-earth ions in glass host materials characterization measurements for rare-earth-doped fibers basics of 1550-nm fiber amplifiers optimization of er-doped fiber pump wavelength choice for 1550-nm amplifiers improved 1550-nm amplifiers in advanced configurations the 1300-nm amplifiers in advanced configurations the 1300-nm fiber amplifier fiber amplifiers in digital direct detection systems distributed fiber amplifiers amplifiers for AM-modulated systems

Stability analysis and numerical simulation of multidevice amplifiers

Abstract: Stability analysis of multidevice amplifiers is made on a generalized circuit comprising two n-ports with S-matrices S (active devices) and S' (passive networks) connected at n interface ports. Open-loop transfer functions defined for a signal-flow graph and its (n-1) subgraphs of incident and reflected waves at the interface ports are expressed in terms of det M/sub n/ and its minors, where M/sub n/=S'S-I/sub n/ and I/sub n/ is the n*n identity matrix. it is shown that the Nyquist plots of the n transfer functions completely characterize the number of right-half complex-frequency-plane zeros of det M/sub n/, and hence the amplifier stability. Insertion of an ideal circulator and isolators at the interface ports enables one to calculate the Nyquist plots and voltage distributions of possible instabilities using commercially available linear circuit simulators. Numerical simulations for two types of parallel-operated GaAs FET amplifiers are performed to verify the usefulness of the analysis in design-phase check of multidevice amplifier stability. >

Spread spectrum communication system particularly suited for rf network communication

Abstract: The transceiver (10) receives data for transmission via a microprocessor (14) by means of an interface (15) under the control of application software (16). The data are transformed into chip sequences by the data encoder (12) and the waveform generator (13). The data then pass through a bandpass filter (18), a baseband amplifier (20), a mixer (22) connected to a local oscillator (24), an RF amplifier (26), and antenna (28). Similarly, the received signal goes through an RF bandpass filter (30), an RF amplifier (32), a mixer (34) connected to a local oscillator (38), a bandpass filter (36), a limiter (40), and a correlator (40). The decoded data packets from the receiver are fed back to the microprocessor (15).

Dynamic equalizing of powered loudspeaker systems

Abstract: A powered loudspeaker system has a cabinet. The cabinet has at least one electroacoustical transducer and a power amplifier coupled to the electroacoustical transducer. Dynamic equalization circuitry coupled to the power amplifier provides a predetermined desired dynamic equalization for the electroacoustical transducer in the cabinet when normally positioned in a listening room.

A novel charge sensitive preamplifier without the feedback resistor

Abstract: A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF.

Wavelength conversion at 10 Gb/s using a semiconductor optical amplifier

Abstract: Data at 10 Gb/s has been translated from an input signal wavelength to another wavelength, either longer or shorter, using gain compression in a 1.5- mu m semiconductor optical amplifier for wavelength conversion. To achieve operation at such high bit rates, the probe (shifted) input must be intense enough to compress the gain of the amplifier significantly. This reduces the gain recovery time of the amplifier because of probe stimulated emission. A consequence of the intense probe is an extinction ratio deduction. Using moderate input powers, wavelength conversion is achieved over a 17-nm (2-THz) range, with 0.7-3-dB power penalties. >

Infrared readout electronics for space-science sensors: state of the art and future directions

Abstract: A review of infrared readout electronics for space science sensors is presented. General requirements for scientific IR FPA readout are discussed. Specific approaches to the unit cell electronics are described with respect to operation, complexity, noise and other operating parameters. Recent achievements in IR FPA readout electronics are reviewed. Implementation technologies for realization of IR FPA readout electronics are discussed. Future directions for addressing NASA and other scientific users' needs are suggested.

2.0 W CW, diffraction-limited operation of a monolithically integrated master oscillator power amplifier

Abstract: The authors fabricated a monolithically integrated master oscillator power amplifier, M-MOPA, with a flared power amplifier region which radiates in a single diffraction limited lobe to an output power in excess of 2 W CW. The radiation pattern is stable with increasing drive current. The spectral output of the M-MOPA is a single longitudinal mode with a side-mode suppression ratio greater than 25 dB. >

Control system for display panels

Abstract: A control apparatus for an active matrix liquid crystal display device is fabricated with the active matrix as a single integrated SOI circuit. The control apparatus and the active matrix are lifted from a silicon substrate and transferred to a glass substrate as a single piece. The control apparatus comprises a video interface, a column driver, and dual row drivers. The video interface operates the active matrix as a multiple-frequency scanning display device. The polarities of the display pixels are reversed on every frame by a polarity switch coupled to a video signal amplifier. The control apparatus further comprises sensors for generating a gray-scale feedback signal to adjust the gain of the video amplifier. User control of the display is provided by a user interface.

Wavelength flattened saturated erbium amplifier using multiple side-tap Bragg gratings

Abstract: By writing several loss-inducing photosensitive side-tap Bragg gratings in a short length of optical fibre, the gain variation of ±1.6 dB over a bandwidth of 33 nm in a saturated erbium doped fibre amplifier is reduced to ±0.3 dB. It is shown for the first time that these gratings may be written with predictable ease.

A CMOS low-distortion fully differential power amplifier with double nested Miller compensation

Abstract: A four-stage fully differential power amplifier using a double-nested Miller compensated structure is presented. The multiple-loop configuration used results in a lower harmonic distortion, at least in the audio band, compared to conventional three-stage amplifiers with nested Miller compensation. Design criteria and stability conditions for good stability of amplifiers using a multiple- (greater than two) loop topology are presented. The amplifier operates with a single power supply which has a minimum value of 3 V. With a 5-V supply, power dissipation is 10 mW and total harmonic distortion (THD) is -83 dB for a -V/sub p-p/ differential output signal at 10 kHz and a load of 50 Omega . With an 8 Omega load and for a 10-kHz, 4-V/sub p-p/ output signal, THD is -68 dB. The chip area is 0.625 mm/sup 2/ in a 1.5- mu m single-poly, double-metal, n-well CMOS technology. >

An ultrasonic surgical handpiece and an energy initiator to maintain the vibration and linear dynamics

Abstract: An ultrasonic oscillator (46) drives a tool at a set frequency. An amplitude control runs the oscillator (46) to set the vibration level. A frequency regulator joins the amplitude and the oscillator (46). A control feedback loop (49), in the frequency regulator, keeps handpiece linear dynamics. An operational transconductance amplifier (52), in the oscillator (46), governs gain of the loop (49). A circuit (55) connects to the control to retard the rate of current application over time to the amplifier (52). The circuit (55) has switching to either retard the rate or reset for start up. The amplifier (54) is a current output device with current directly proportional to the bias current and input voltage with bias as gain change for the loop (49). The circuit (55) limits the bias to the amplifier (54) to modify frequency response and output current. A capacitor delays application of the bias to the amplifier (54). Replaceable tools of various lengths or shapes positioned along an axis vibrate for surgery at the frequency and a wave length. Tools longer than one wavelength and of configurations tuned to oscillate around the frequency resonate as a function of their material, length and configuration. A flue (17) surrounds the tool and has a hollow elongate semi rigid central body (28) about an axis with a funnel (29), at one end thereof and a nozzle (30), at the other to direct annular irrigant/coolant flow therethrough. The funnel (29) and nozzle (30) are resilient. Reinforcing ridges (32), inside the nozzle (30), act to maintain concentricity between the flue (17) and nozzle tip and channel irrigant thereabout.

A 100-element HBT grid amplifier

Abstract: A 100-element 10-GHz grid amplifier has been developed. The active devices in the grid are chips with heterojunction-bipolar-transistor (HBT) differential pairs. The metal grid pattern was empirically designed to provide effective coupling between the HBTs and free space. Two independent measurements, one with focusing lenses and the other without, were used to characterize the grid. In each case, the peak gain was 10 dB at 10 GHz with a 3-dB bandwidth of 1 GHz. The input and output return losses were better than 15 dB at 10 GHz. The maximum output power was 450 mW, and the minimum noise figure was 7 dB. By varying the bias, a signal could be amplitude modulated with a modulation index as large as 0.65. Tests show that the grid was quite tolerant of failures-the output power dropped by only 1 dB when 10% of the inputs were detuned. The grid amplifier is a multimode device that amplifies beams of different shapes and angles. Beams with incidence angles up to 30 degrees were amplified with less than a 3-dB drop in gain. >

1.5 mu m multiquantum-well semiconductor optical amplifier with tensile and compressively strained wells for polarization-independent gain

Abstract: A multiquantum-well optical amplifier for 1.5- mu m wavelength operation using alternating tensile and compressively strained wells in the active region is described. For each bias level measured, the polarization sensitivity of the amplifier gain is 1 dB or less averaged over the gain bandwidth. This amplifier is suitable for integration with other optical devices in photonic integrated circuits which require polarization-independent gain. >

AM-FM transmitter power amplifier

Abstract: A power amplifier used in a portable, radio frequency transmitter is switched between different modes of operation when transmitting differently modulated carriers. The first mode of operation corresponds to amplitude modulation (AM), while a second mode corresponds to angle modulation techniques such as frequency modulation (FM). A switching network alters the impedance of the power amplifier to match network for matching the impedance of the transmitter antenna in order to achieve maximum efficiency in each mode of operation. Various switching methods and impedance matching circuits are disclosed.

Polarization insensitive multiple quantum well laser amplifiers for the 1300 nm window

Abstract: A polarization insensitive (less than 1 dB gain difference over the 3 dB gain bandwidth) multiple quantum well laser amplifier for the 1300 nm window is reported for the first time. The amplifiers employ a single active layer containing three tensile strained and four compressively strained quantum wells and show a fiber to fiber gain of 16 dB at 1310 nm and 200 mA driving current. Furthermore at the same wavelength these devices have a record low fiber coupled noise figure of 6.5 dB and a conveniently high fiber coupled saturation output power of 13 dBm for both polarizations.

Complex bioelectric impedance measurement system for the frequency range from 5 Hz to 1 MHz

Abstract: Analytic techniques that have been successfully employed in materials science, and to a lesser extent in the study of biologic systems, have potential for improving the application of bioelectric impedance provided that both real and imaginary impedance components can be measured with sufficient accuracy over a given frequency range. Since biologic tissue, particularly animal tissue, is typically highly conductive, phase angles are small, making accurate measurements difficult. A practical four-terminal system employing commercial lock-in amplifiers is described and error sources and corrective tech-niques are discussed.

Quantum optical cloning amplifier

Abstract: We demonstrate experimentally that a type-II pulsed optical parametric amplifier can duplicate (or, clone) a signal in the quadrature it amplifies. Although this device is an amplifier with large gain, it meets the quantitative criteria for quantum nondemolition measurements and, thus, operates in the nonclassical regime. It can be used as a noiseless amplifying optical tap which, at the same time, can overcome the noise introduced downstream by propagation and detection losses.

Digital liquid level sensing apparatus

Abstract: A digital liquid level sensing apparatus for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array including a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of a fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages. The controller converts each of the peak voltage signals into a corresponding digital value and stores each of the digital values in an on-board memory. The controller then sequentially compares each of the values against at least one predetermined reference value indicative of an output produced by an input plate disposed in air until a predetermined difference is detected between the reference value and any one of the stored digital values. This indicates a predetermined difference in the dielectric, thus indicating that a corresponding input plate is at least partially submerged in fluid.