R.W. Ralston

A SAW/CCD programmable matched filter

A charge‐coupled device (CCD) has been integrated with a surface‐acoustic‐wave (SAW) piezoelectric delay line in a hybrid gap‐coupled structure to produce an electronically programmable analog matched filter in which the filter function is controlled by the charge pattern clocked into the CCD. This device allows analog‐analog correlation of SAW input signals of ≲40‐MHz bandwidth and ≲3.5‐μs duration. Programming time is 6 ms at a 100‐kHz clock rate, and the reference holding time is 1 s for a 3‐dB degradation of the correlation peak. Operation as a matched filter for a 3.25‐μs‐long 13‐bit Barker‐encoded signal yields a peak correlation level of −41 dB m.

Stable CW Operation of Gap-Coupled Silicon-on-Sapphire to LiNbO 3 Acoustoelectric Amplifiers

Abstract : Technological advances are detailed which improve the performance of gap-coupled acoustoelectric amplifiers for dc drift field operation. The amplifier configuration is a segmented 1-micrometer thick layer of 20 ohm cm n-type silicon-on-sapphire held in close proximity to a 21-microsecond (YZ) LiNbO3 delay line. The combination of ion-beam-etched spacer posts on the delay line surface and a simple packaging scheme utilizing the sapphire wafer as a pressurized diaphragm allow reproducible formation of uniform air-gaps of the order of 0.1 micrometers over a 1.5 mm x 2.5 cm area. Transverse dc fringing fields are effectively terminated both at the surface traps of the chemically-stripped and depleted Si surface and at the deep acceptor-donor pair traps within the Si film. Thus the electron-sheet homogeneity is preserved even at drift fields over 2 kV/cm and the theoretical S-shaped gain characteristic is observed. For an effective coupling gap of 0.17 micrometers a typical 1/2-cm long segment has peak electronic gain of over 21 dB at 140 MHz with a minimum acoustic noise figure of 7 dB near 1 kV bias. Intermodulation distortion products are more than 50 dB below signal for output sheet powers under 2 dBm/mm. Phase deviation relative to the delay line alone is only 0.7 deg rms for 4 cascaded segments. (Author)

A SAW/CCD accumulating correlator

A new analog‐signal‐processing device is reported in which a charge‐coupled device (CCD) is coupled to a piezoelectric surface acoustic wave (SAW) delay line across a 300‐nm gap. The CCD samples multiply, accumulate, and read out the cross‐correlation function of two wide‐band SAW input signals which counterpropagate on the delay line. A signal‐processing gain of 30 dB at a bandwidth of 20 MHz has been observed by correlating biphase modulated pseudonoise waveforms of 100‐μs duration in the presence of Gaussian noise. This compact hybrid structure provides 300 discrete samples of a 7‐μs segment of the correlation function.

An acoustic SAW/CCD buffer memory device

A SAW piezoelectric delay line has been integrated with a silicon charge‐coupled shift register device (CCD) across a 300‐nm gap to produce a fast‐in slow‐out buffer memory. A prototype with an input bandwidth of 40 MHz centered around 107 MHz, an input signal duration time of 3.5 μs, and an output clock rate of 100 kHz has been fabricated and tested. The basic configuration of this SAW/CCD consists of a lithium niobate (LiNbO3) delay line, in close proximity to an array of 300 sampling fingers connected to a 300‐stage buried‐channel CCD on a p‐type silicon susbtrate. The output of the CCD retains both amplitude and phase of the input signal.

Cooperating on superconductivity

The results to date of a cooperative effort begun by AT&T, IBM, and MIT, called the Consortium for Superconducting Electronics (CSE), are reviewed. The goal is to bring high-temperature superconductivity to market rapidly. Of primary importance in these early years is the CSEs materials and processing program, which develops and evaluates substrate materials and film-deposition techniques for specific applications. Programs in junctions, microwave networks, and circuits are also underway. The aims and accomplishments of all four programs are examined. A successful trilayer approach is discussed. New members of the CSE are noted, and funding sources are indicated.<<ETX>>

Gap‐coupled InSb/LiNbO3 acoustoelectric convolver operating at 77 K

A gap‐coupled InSb/LiNbO3 acoustoelectric convolver has been fabricated and tested at 77 K. The results suggest the possibility of using a similar structure with a high‐density InSb diode array as an acoustically scanned infrared imaging device. Measurements indicate that near optimum bias, the convolution efficiency was −63 dBm, the convolution output was uniform along the device length to within 1.5 dB, the insertion loss was 26 dB, the 1‐dB compression point occurred at 18 dBm power input, and the efficiency was constant to ⩽ 3 dB over the range 66–70 MHz.

A CCD-Programmable SAW Matched Filter

A charge-coupled device (CCD) has been integrated with a SAW delay line to produce an electronically programable analog matched filter in which the filter function is controlled by the charge pattern clocked into the CCO. A prototype with an input signal bandwidth of 40 MHz centered around 107 MHz, a correlation time of 3.5 us and an analog input reference clock rate of 100 kHz has been fabricated and tested. This device consists of a LiNb03 delay line coupled across a gap to a silicon substrate. An output e lectrode on the LiNb03 is capacitively coupled to an array of 300 conducting fingers connected to a 300-stage CCD shift register on the silicon substrate. Nonlinearities in the silicon multiply the RF fields accompanying a SAW signal with dc potentials programed on the f ingers by the CCD, and the local product terms are summed on the o utput electrode to produce the d esired cross-corrdation between reference and signal waveforms. Operation as a matched filter for a 3.25-us-long 13-bit Barker-encoded signal yields a peak correlation level of -41 dBm.

A surface‐acoustic wave/metal‐oxide‐silicon field‐effect transistor memory correlator

An array of metal‐oxide‐silicon field‐effect transistors has been integrated with a surface‐acoustic wave (SAW) delay line in a hybrid gap‐coupled structure to produce a SAW‐programmable memory correlator. This device allows analog‐analog correlation of SAW input signals of 40‐MHz bandwidth and 3.5‐μs duration. Operation with a 1.8‐μs‐long rectangular pulse at a carrier frequency of 100 MHz yields a peak correlation output of about ‐46 dBm.

Four-Wave Interactions in Acoustoelectric Integrating Correlators

Device Structure Four-wave acoustoelectric interactions have been observed in an integrating correlator device. use of the four-wave process provides both signifi- cantly improved device performance over that achieved with three-wave interactions and makes possible a unique signal-processing function: triple-product c orrelation. These electric-field interactions involve the differential delay, mixing, and time-integration of two surface acoustic waves (SAWs) at frequencies w1 and 9 counter- propagating on a LiNb03 delay line in the presence of a uniform pump at a frequency w1 + w2 applied to a PtSi diode array. A narrow (%350-nm) air gap provides coupling of the array to the evanescent RF fields accompanying the SAWs. Nonlinearities in the silicon provide local mixing of the three input RF fields to create a quasi-static field of finite wavevector. Time-integration of this field produces a stationary wave of charge which is stored in the diode array. A similar four-wave process is used to scan this charge pattern. The two interactions have been cascaded to demonstrate the correlation of a waveform with a time-bandwidth product in excess of 10,000.

Nonreciprocal acoustoelectric interaction of surface waves and fluorine plasma-treated AlGan/GaN 2DEG

This paper demonstrates acoustoelectric (AE) effects for surface acoustic waves (SAWs) propagating in an AlGaN/GaN 2DEG, where a fluorine based plasma has been used to tune the carrier concentration. Incorporation of fluorine ions in the AlGaN barrier is shown to reduce sheet carrier density in the 2D layer, which is required to prevent screening of piezoelectric fields. Tuning of the 2DEG channel is also observed with a progressive shift of the threshold voltage for co-fabricated HEMT structures. The monolithic gain devices exhibit nonreciprocal insertion losses under applied DC bias for higher-order Rayleigh modes in GaN on sapphire at 728 MHz and 1.48 GHz. This constitutes a first step in implementing the carrier control required for AE gain in 2D semiconductors with intrinsically high sheet density.