Showing papers on "Wideband published in 1985"

Wideband photon counting and homodyne detection.

Abstract: Homodyne detection has been proposed as a means of detecting squeezed coherent radiation. Here the response of a balanced homodyne detector to wideband squeezed coherent states is presented. In order to carry out the analysis the theory of wideband photodetection is reviewed and in order to determine the ultimate performance limits of photoemissive detectors small terms of order \ensuremath{\Delta}\ensuremath{\omega}/${\ensuremath{\omega}}_{0}$ that are usually neglected, where ${\ensuremath{\omega}}_{0}$ is the optical carrier frequency and \ensuremath{\Delta}\ensuremath{\omega} is the electronics bandwidth, have been kept. It is shown that the ultimate noise reduction that can be achieved in the noise-power spectrum of a homodyne detector, detecting squeezed coherent radiation, is a factor of 2 worse when photoemissive detectors are used instead of power flux detectors.

Direction determination of wideband signals

Abstract: A computationally efficient sensor array processing method has been developed for estimating the bearings of multiple planewave sources with unknown frequency characteristics within a wideband. The method uses the zero-delay covariances of the complex analytic representations of the sensor signals of a planar array to estimate the wavenumber spectrum. This spectrum determines source bearings over the entire 360 degree range. The computational requirements of this method are of the same order as frequeney-wavenumber analysis on a planar array at a single frequency. In contrast to the single frequency analysis, this method provides wideband temporal frequency information above each plane-wave. The usefulness of this method for the bearing estimation of acoustic sources is demonstrated with experiments on real data.

Wideband multilayer coaxial-fed microstrip antenna element

Abstract: Electrically thick (and hence wideband) microstrip patch antenna elements are difficult to excite without adversely affecting their performance. A novel feeding technique is presented which circumvents the difficulties. A simple design theory is presented and a practical example is described which operates between 11 and 12 GHz.

Detection of temporal gaps in bandlimited noise: Effects of variations in bandwidth and signal‐to‐masker ratio

Abstract: Thresholds were measured for the detection of a temporal gap in a bandlimited noise signal presented in a continuous wideband masker, using an adaptive forced‐choice procedure. In experiment I the ratio of signal spectrum level to masker spectrum level (the SMR) was fixed at 10 dB and gap thresholds were measured as a function of signal bandwidth at three center frequencies: 0.4, 1.0, and 6.5 kHz. Performance improved with increasing bandwidth and increasing center frequency. For a subset of conditions, gap threshold was also measured as bandwidth was varied keeping the upper cutoff frequency of the signal constant. In this case the variation of gap threshold with bandwidth was more gradual, suggesting that subjects detect the gap using primarily the highest frequency region available in the signal. At low center frequencies, however, subjects may have a limited ability to combine information in different frequency regions. In experiment II gap thresholds were measured as a function of SMR for several signal bandwidths at each of three center frequencies: 0.5, 1.0, and 6.5 kHz. Gap thresholds improved with increasing SMR, but the improvement was minimal for SMRs greater than 12–15 dB. The results are used to evaluate the relative importance of factors influencing gap threshold.

Digitally controlled wideband phase shifter

Abstract: A digitally controlled wideband phase shifter is disclosed in which an input signal is resolved into two quadrature related components, the components are scaled in a stepped digital manner in proportion to the sine and cosine of the phase shifting angle, and then recombined to reconstitute a phase shifted replica of the input signal. The scalers are segmented MESFETS of a dual gate design in which each segment, has a predetermined transconductance and may be gated "ON" or "OFF" by a control signal to affect the overall transconductance of the scaler, and thereby the scaling factor. The phase shifter is implemented by a monolithic microwave integrated circuit technique in which the preferred substrate material is gallium arsenide, and in which all active device and circuit features are formed on the substrate by a photolithographic process. The phase shifter is adapted to scaling at stepped angles, typically 111/4 or 221/2 degrees, is broadband and is applicable to frequencies ranging from a fraction of a gigahertz to many gigahertz.

UHF wideband statistical model and simulation of mobile radio multipath propagation effects

Abstract: A local wideband statistical model is presented for UHF mobile multipath propagation. The complex echo-envelope statistics have been derived from 10 MHz wideband pulse soundings at 436 MHz over a large area in suburban and urban localities. In the proposed model, the effects of Doppler-induced RF phase shifts have been considered. Echo paths are shown to fit a Poisson distribution for the excess time delays, while the echo envelopes conform to Rayleigh fading statistics. Correlated scattering, evident from echo path clusters in time-delay and echo-amplitude correlation coefficients in neighbouring path delay bins, is shown to be significant for excess path time delays less than 0.3 μs. Disagreements observed for local and nonlocal scattering in different localities are discussed. The implementation of a wideband multipath simulator based on the statistical model is described. Digital computer simulation of DPSK is used as an illustrative example to demonstrate its usefulness.

Wideband 180-degree phase shifter bit

Abstract: A wideband 180-degree digital phase shifter bit is provided which is operable independently of input rf frequency over a predetermined bandwidth of interest. The phase shifter bit comprises a coupled transmission line segment and a pi network segment, with switching means for alternatively connecting the rf input and rf output first to the coupled transmission line segments, and then to the pi network.

Wideband feedback amplifier

Abstract: Current feedback is employed in differential and unbalanced input wideband feedback amplifiers to render bandwidth and transient response insensitive to closed loop gain over a wide range. In the differential amplifier, two NPN transistors (Qa, Qb) have their emitters connected by a resistor (Ra) and receive input signals (Va, Vb) at their bases. The collectors are connected to a current or voltage mirror, and gain means (A(s)) and a resistor (Rc) are connected between one of the collectors and the emitter of the transistor (Qa).

High speed analog/digital driver

Abstract: Apparatus for a driver, which handles both wideband analog and high speed digital signals through one common signal path into a low impedance load and is therefore particularly suited for use in automatic testing equipment (ATE), is described.

Antenna topics in my experience

Abstract: A brief account of some concepts and developments in my experience with antennas is presented under three headings: A-wide-band matching to a long line; B-small antennas; C-planar arrays. They cover the half-century from 1935 to date.

Wideband wing-conformal phased-array antenna having dielectric-loaded log-periodic electrically-small, folded monopole elements

Abstract: A compact, lightweight, wideband, wing-conformal phased-array antenna structure, the array elements of which are identical, log-periodic arrangements of electrically small, folded-monopole elements printed on both sides of a dielectric substrate A significant reduction in the height of the array elements makes this array configuration feasible for many airborne applications

Design and performance of millimeter-wave end-coupled bandpass filters

Abstract: The design and performance of millimeter-wave microstrip/suspended-stripline end-coupled bandpass filters are presented. Filters in Ka-band (26.5 to 40 GHz) and W-band (75 to 110 GHz) using suspended-stripline and microstrip have been designed. Good agreement between the experimental results and those predicted theoretically was observed. Measured passband insertion losses of less than 1 and 0.5 dB have been achieved in W- and Ka-band, respectively. An extremely wideband waveguide-to-microstrip transition with an insertion loss of 0.25 dB over the full W-band is also presented.

Ultrasonic Transducer Composed of Two Piezoelectric Layers with Variable Weighting

Abstract: Two different piezoelectric layers with alternate vibrating polarity are stacked to compose wideband ultrasonic transducers. With this construction, the amplitude and the phase of applied voltage for individual piezoelectric layers can be adjusted so that we can provide variable weighting for the transducers to obtain a wideband vibrating mode. In this paper, the construction of the transducer is proposed and its theoretical analysis is described. Experimental results performed at a frequency around 4 MHz are further demonstrated with a comparison of the theory.

Electromagnetic acoustic transducers as wideband velocity sensors

Abstract: The performance of electromagnetic acoustic transducers as wideband velocity sensors has been investigated, using a pulsed laser as a standard acoustic source.

Small wideband passive/active antenna

Abstract: An array of five, ridge waveguide horns provides monopulse operation over awo octave range. A unique coax-to-ridge waveguide input coupler and an extended ridge matching section at the radiating apertures provide the extended frequency range. The horn assembly is lightweight, compact and suitable for array applications. A five horn monopulse primary feed array is exemplified.

Off-channel frequency discriminator circuit for use in a precision distance measuring equipment (DME/P) receiver

Abstract: A precision distance measuring equipment (DME/P) receiver for detecting an RF signal including at least one interrogation pulse is described. The DME/P receiver includes first and second signal processing channels. The first processing channel includes a wideband filter, of bandwidth BW1, for receiving the processed RF signal and in response thereto generating a wideband (FA) mode signal proportional to the logarithm thereof. The second signal processing channel includes a narrowband filter, of bandwidth BW2, for receiving the processed RF signal and in response thereto generating a narrowband (IA) mode signal proportional to the logarithm thereof, the bandwidth BW2 of the narrowband filter being within the bandwidth BW1 of the wideband filter. A frequency discriminator circuit receives samples of the FA and IA mode signals from the first and second signal processing channels, and in response thereto generates a control signal when the pulse has a frequency within the bandwidth BW1 but outside the bandwidth BW2, the control signal representing an "off-channel" condition. In operation, gating circuits are connected to receive the control signal from the frequency discriminator circuit and operate to inhibit further processing of the FA and IA mode signals in the receiver during the "off-channel" condition.

Wideband Voltage-Current Converter Circuit

Abstract: A wideband voltage-current converter circuit with nonlinearity-error compensation has been developed. Bandwidth is 100 MHz (?3dB) or 30 MHz (?1%). The circuit was realized with a new bipolar cell-based semicustom array intended for use in training as well as for industrial prototyping and custom IC production.

Fast acquisition circuit for synchronous digital receiver operating in wideband noise

Abstract: A signal acquisition circuit for a synchronous receiver that requires frequency sweep to acquire a digitally modulated signal but tends to false lock onto data sidebands or for a receiver that cannot use a frequency discriminator because of wideband noise. The receiver must provide a phase error output signal and also a signal-acquired indication that does not assert during false locks. The circuit comprises an integrator selectively coupled either to the phase error signal or to a square wave sweep waveform used for signal acquisition. The integrator is controlled by a detector output analysis circuit that compares the envelope of the signal received during frequency sweeps with the peak of the envelope determined from successive sweeps by a peak detector with a long time constant. The circuit avoids false locks and continues to sweep through successive false locks until the signal-acquired indication asserts to indicate true lock.

Sensitivity and performance analysis of coherent signal-subspace processing for multiple wideband sources

Abstract: This paper presents some of the statistical properties of a new signal-subspace approach to the estimation of the angles-of-arrival (AOA) of several wideband plane waves received in noise. This approach is denoted as the Coherent Signal-Subspace Method (CSM). The statistics that are presented include the bias and variance of the AOA estimates as well as a statistical measure of the similarity between the true and estimated coherent signal-subspaces.

Wideband Electronically Tunable GaAs Gunn VCO's at W-Band (75-110GHz)

Abstract: A series tuned GaAs VCO employing a second harmonic radial disk circuit has provided up to 10 percent electronic tuning bandwidth (ETB) at 94GHz. Packaged GaAs Gunn and Hyperabrupt Varactor Diodes are employed. Analysis of the series equivalent circuit provides insight into methods of controlling trade-off between output power and tuning bandwidth, e.g. by restricting the ETB to 1.5GHz around 92.3GHz an output power of 18 to 22mW was achieved; with tighter coupling an output power of 11 to 12.8mW from 91.5 to 95.5GHz resulted.

Applications of SAW Convolvers to Spread-Spectrum Communication and Wideband Radar

Abstract: Surface acoustic wave (SAW) convolvers and support circuitry have been developed to provide matched filtering of wideband waveforms having lime-bandwidth products exceeding IO3 and continu- ously changing spreading codes for both spread-spectrum communication and wideband radar applications. For spread-spectrum Communication, additional signal processing techniques have been developed to provide correlation of waveforms having time-bandwidth products of IO6 or more with a search window of microseconds for a 100-MHz signal as well as to perform antimultipath processing for data demodulation and for ranging. For wideband radar, high-speed optoelectronic track-and-hold circuits for range gating as well as buffering and charge-coupled-device matrix- matrix-product chips for Doppler processing are being incorporated along with a SAW convolver to provide 0.75-m range resolution and 32 Doppler bins for each of 1280 range bins.

Performance evaluation of whole-body NMR scanner antenna systems.

Abstract: Whole-body NMR imaging antennas (probes) are strongly affected by the inevitable magnetic and controllable dielectric losses. Using a convenient parallelepiped model, the magnetic losses are evaluated. By introducing the "ideal power gain," the best possible antenna performance is delimited as a function of the frequency and the patient examined. By using a cylindrical model and introducing the "electrostatic quality factor" (EQF), the dielectric loss of any antenna can be estimated. With the help of the wideband field measurer described, a simple experimental arrangement, and the analysis developed, the performance of whole-body NMR antennas can be compared and/or evaluated. An example is given for the application of this model at 6.4, 21, and 64 MHz for three typical patients.

Electrode Reflections, Directionality, and Passband Ripple in Wideband SAW Chirp Filters

Abstract: Abstmct-Experimental and theoretical studies have revealed several effects in surface-acoustic-wave chirp filters that arise from electrode reflections. One effect is that down-chirp filters have lower loss than up-chirp filters, which is shown to be caused by asymmetric phasing of reflections by near-synchronous electrodes. The most prominent effect is large amplitude ripple in the passband of broadband down-chirp mters, occurring at frequencies above the second harmonic of the synchronous frequency of the lowest-frequency electrodes, and caused by surface wave reflections by electrodes with a synchronous frequency that is half the operating frequency. The large amplitude ripple is halved in nondispersive chirp filters and does not occur in up-chirp filters. A further effect is enhanced triple-transit ripple, which is also due to “second harmonic” reflections, and occurs in both upand down-chirp filters. A design procedure that suppresses the large amplitude ripple is described and is found experimentally to be effective. Relations are given for the estimation of directionality, and single and triple transit ripple amplitudes due to second harmonic reflections, for chirp filters with arbitrary chirp law, bandwidth, and dispersion time.

Plural input television receiver having peaking circuit and chrominance band reject filter in a video signal channel

Abstract: A television receiver responsive to broadcast television signals in a normal operating mode includes a video channel with high frequency peaking circuits, followed by a wideband display driver to which auxiliary R, G, B color image signals are applied in an auxiliary operating mode of the receiver. A low pass filter restricts the high frequency response of the video channel in the normal mode so that the combination of the high frequency peaking circuits and the wideband display driver does not result in a condition of excessive signal bandwidth and attendant unwanted spurious high frequency signal effects.

Adaptive automatic scan tracking system

Abstract: A servo loop for an automatic scan tracking arrangement for a helical-scan videotape playback machine includes a wideband relatively low-gain portion for fast acquisition and correction of mistracking errors. In order to provide high gain for reducing mistracking which recurs from scan to scan, a second path in the servo loop in parallel with the wideband path includes a commutating filter which accumulates the average error signal generated by the wideband system in a commutating filter and reinserts the averaged error to provide adaptive systematic correction having a comb-like response. This reinsertion reduces the magnitude of the systematic errors which the wideband portion of the servo must correct, and therefore reduces the amount of closed-loop mistracking which repeats from scan to scan.

Wideband Array Processing For Acoustic Detection and Tracking Of Aircraft/sup */

Abstract: The Distributed Sensor Network Program, sponsored by DAFPA, has as its goal the development of technology to enable the construction of defensive systems of geographically separated sensors and distributed computational resources. In general such a system would consist of autonomous nodes that would work cooperatively to detect and track targets of interest and would report interesthg situations to a user (or set of users) through some interface. Each node would consist of appropriate sensors and processors (hardware and software) to permit it to perform some tasks independently of other nodes and communications to permit it t o work cooperatively with other nodes to form a viable distributed system.

Television receiver with display driver amplifier and input video filter having inversely related bandwidths

Abstract: A television receiver responsive to a broadcast television signal in a normal operating mode includes a television signal channel with high frequency peaking circuits, followed by a display driver to which an auxiliary video signal may be applied. A low pass filter is connected between the output of the television signal channel and the display driver, which exhibits a wide bandwidth when the receiver is intended to display auxiliary video information. The bandwidth of the low pass filter is inversely related to the bandwidth of the driver such that the low pass filter exhibits a narrow bandwidth relative to the bandwidth of a wideband display driver. In addition, the low pass filter exhibits a trapping characteristic at the second harmonic frequency of the chrominance signal in a color television receiver.