Analog Delay Line Research Articles

A 380H × 488V CCD Imager with Narrow Channel Transfer Gates

When the channel width of an FET becomes of the same order of magnitude as the depth of the gate depletion region, an increase of threshold voltage is observed. This narrow-channel effect has been applied successfully in creating an asymmetric potential well under an electrode for two phase CCD operations. The feasibility of this new structure has been confirmed in a 242 element analog delay line and the application is now extended to a 380H × 488V CCD Imager. In the constructed B/W CCD camera.

Responses of single units in laminae 2 and 3 of cat spinal cord

333 units were recorded in laminae 2 and 3 of lumbar cord in decerebrate cats. Recording of small-amplitude spikes was made possible by the use of platinum-surfaced tungsten microelectrodes, continuously varible filters and an analogue delay line display. Stimulation of the lateral Lissauer tract showed that a sample of the units sent axons into this tract. Using iron-plated electrodes, recording sites were marked and shown to be within laminae 2 and 3. Axons of peripheral afferent axons were excluded from the sample, as were long-range descending axons. By using one electrode placed close to a cell body in lamina 4 and a roving electrode in the dendritic region dorsal to the cell body, it was possible to show that the recorded units wer not field spread of deeper cells. Of the units 94% had peripheral receptive fields, RF; 30% had small RFs less than 2 sq.cm, intermediate in size between RFs of peripheral axons and RFs of large cells in dorsal horn. These small RF cells occurred in clusters and their RFs constituted a fraction of the larger RF of nearby large cells. Of the units 56% responded to brush and touch, 19% to brush, touch and pressure, while 19% required pressure on skin to exite them. Latency of response to electrical stimulation showed that all cells were excited by myelinate afferents. While no cells were detected exclusively by C afferents, may may have been excited by both A and C afferents. Eighteen per cent of the cells showed a prolonged discharge lasting more than 5 sec after a single stimulus. Some of these long discharge cells continued firing for minutes. Another unusual class, 14% of all cells, habituated very powerfully to intermittant natural or electrical stimuli, and remained unresponsive for many seconds after responding to the first stimulus.

Computer controlled bidirectional phasing for real time echosonography.

A bidirectional phasing scheme for a real time B-mode ultrasonic imager is described. The system uses a PDP-11 digital computer and analog delay lines to focus an ultrasonic transducer array. Preliminary transmit field patterns, obtained using the system suggest the resolution will be Rayleigh limited.

A Simple Active-RCDelay Line

A new easy to realize active-RC analogue delay line with tap outputs available at every half-bit delay intervals has been described. The basic delay section, comprising of only two transistors and a few RC elements, has a delay to rise-time ratio of 1.3 and works upto a frequency range of 500 kHz. A tapped delay line of lengths upto 15 can be easily made by cascading the basic delay sections. This delay line is particularly useful in the audio and lower frequency ranges where other types of delay lines are more cumbersome. Even in the discrete form, it is quite compact and can be further miniaturized by using IC/thin/thick-film hybrid techniques.

Two Phase CCD with Narrow-Channel Transfer Regions

When the channel width of a FET becomes of the same order of magnitude as the depth of the gate depletion region, an increase of threshold voltage is observed. This narrow-channel effect has been applied successfully in creating an asymmetrical potential well under an electrode for two phase CCD operations. The basic performance of this new structure has been evaluated in a 242 element analog delay line with 60 µm channel width and 36 µm element length. Observed inefficiencies per transfer are in the low 10-4 for surface channel versions and in the low 10-5 for buried channel version.

High-performance digitally programmable analogue transversal filter

An electrically programmable transversal filter is presented, based on a tapped analogue delay line. The experimental results presented here highlight the large dynamic range capability of the filter structure. The approach is highly suitable for monolithic implementation using standard c.t.d. technology.

A c.t.d. adaptive inverse filter

An inverse filter, incorporating a charge-transfer-device (c.t.d.), tapped analog delay line and digitally programmed tap weights, is reported. This computer controlled analog processor performs a zero-forcing algorithm under software control. The inverse filter (or transversal equaliser) is demonstrated with an LC resonator as the distorting medium. The results show that this processor permits partially overlapping distorted impulses to be clearly discriminated.

Phase equalisation of analogue magnetic recorders by transversal filtering

The ‘time-reversed-impulse-response’ method of phase equalisation is explained theoretically. Experimental results are presented, showing the impulse response of an analogue magnetic recorder before and after phase equalisation. The transversal-filter equaliser (32-tap analogue delay line of 320 μs length) is adjusted in the time domain so that actual phase-response measurements are not necessary.

Transversal filtering of analog signals with a tapped analog delay line

Transversal filtering of analog signals with a tapped analog delay line

Electronic demonstrations for the teaching of acoustics

Courses in elementary acoustics taught at many universities provide introductions to the following six topics: physical acoustics, environmental acoustics, the physiology of hearing, auditory psychophysics, musical acoustics, and the nature of human speech. Electronic demonstrations can be used to enhance instruction in each of the six areas. For example, the modules of an electronic music synthesizer together with an audio system and conventional electronic instrumentation form a versatile laboratory for experiments in sound. Among the demonstrations which can be done are the following. Wave interference can be demonstrated by extracting the separate signals from a stereo recording of signals A + B and A − B. Tone and noise bursts can be used to find the speed of sound, echo and reverberation times. Filter banks, set according to mean audiometric presbycusis data, can show the effects of aging on the frequency response of human hearing. Gently nonlinear electronic devices aid the recognition of combination tones normally generated by the inner ear. Analog delay lines can create repetition pitch from a source of white noise. Sine wave signals from many oscillators can be summed and varied to study the perception of pitch of an inharmonic tone complex like that of a chime. The phase variation of a single rectangular wave with pseudorandom pulse width modulation simulates chorus effect. Much of the effect of nonlinear mode mixing in conventional musical instruments can be simulated by patched of linear electronic components, transient generators and voltage controlled signal processing modules. Three resonant filters allow the synthesis of vowel sounds. Frequency shifted or ring modulated speech sounds can exhibit the importance of vowel formant transitions. Intelligibility experiments with chopped speech serve as an introduction to redundancy, autocorrelation and information theory. We note that one does not pursue this informal experimenting with signal processing equipment for long before one discovers effects which are hard to understand. Further pursuit can lead to new results. For example, our intelligibility experiments with chopped speech suggest that redundancy, measured in spoken English text agrees with that found by Shannon for written text.

A nonoverlapping gate charge-coupling technology for serial memory and signal processing applications

Of the many technologies available to implement efficient and stable charge-coupled devices (CCD's), most employ a multilevel metal, overlapping gate approach. As a consequence, the CCD process becomes generally more complex and the resulting overlap capacitance can be embarrassing for serial memory applications. This paper describes a single level aluminium gate process, the notable features of which are simplicity, extremely high yield, low interphase capacitance, and very high packing density. Interelectrode spacings in the range 2000 /spl Aring/-5000 /spl Aring/ are achieved. The performance capability is described in the context of an analog delay line.

A nonoverlapping gate charge-coupling technology for serial memory and signal processing applications

Of the many technologies available to implement efficient and stable charge-coupled devices (CCD's), most employ a multilevel metal, overlapping gate approach. As a consequence, the CCD process becomes generally more complex and the resulting overlap capacitance can be embarrassing for serial memory applications. This paper describes a single level aluminium gate process, the notable features of which are simplicity, extremely high yield, low interphase capacitance, and very high packing density. Interelectrode spacings in the range 2000 A-5000 A are achieved. The performance capability is described in the context of an analog delay line.

Low-frequency correlator using a bucket-brigade analogue delay line

The paper describes a low-frequency correlator in which a continuously varying delay of a signal is obtained by means of a bucket-brigade analogue delay line. Experimental results of the successful application of the correlator to the areas of autocorrelation, impulse response and signal recovery are given.

High-speed m sequence generation

A method is described that enables maximal-length sequences to be generated over limited ranges of clock rates, at speeds in excess of those normally obtained. The technique uses an analogue delay line to compensate for the delay inherent in the feedback network used in m sequence shift-register generators.

The Segmented Aperture Synthetic Aperture Radar (SASAR)

A new concept in synthetic aperture radar, called SASAR, which uses a segmented aperture, is described. Use of the segmented aperture allows appreciable extra receiving antenna gain to be realized. Each subarray of the receive antenna is equal in length to the transmit antenna; the system performance is increased approximately by a factor equal to the number of subarrays. To allow array combination of the subarray signal outputs requires a phase-shift factor (varying with azimuth) to be applied to each subarray signal. A digital implementation of this preprocessor is sketched out; it uses a push-down storage stack to store the range histories for a synthetic aperture from each subarray. Appropriate phase shifts are added to the stacks and a sum of stack values then provides the combined output range history sequence. Possibilities of using analog delay lines for preprocessing are also discussed. Pattern errors due to subarray size and receive array near field are examined and constraints are given.

The effects of bulk traps on the performance of bulk channel charge-coupled devices

The effects of bulk traps on the transfer effciency and transfer noise in bulk channel charge-coupled devices (BCCD's) are calculated for different charge packet sizes and operating frequencies. These predictions are compared with experimental results and the distribution and density of bulk states in actual devices are thereby measured. The measured low transfer inefficiency of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> per transfer with no intentionally introduced background charge and low transfer noise are shown to be due to a low bulk state density of 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . A detailed comparison of estimated noise in both surface and bulk channel versions of an image sensor and an analog delay line show that BCCD's are very attractive for low-light level imaging but not as attractive for analog signal processing.

Computer-aided analysis of solid-state analog delay lines using conventional circuit analysis programs

A method is described for analyzing the two-dimensional behavior of minority carriers in a solid-state analog delay line by applying, without modification, existing computer-aided circuit analysis programs to a lumped model. Development of the model in two dimensions is based on an approximate solution of the minority carrier partial differential equation using an analogous electrical network. The model includes injecting and collecting junction nonlinearities and thereby permits the study of responses to arbitrary external excitations. Several examples of the use of the model are given.

Practical considerations for analog operation of bucket-brigade circuits

The bucket-brigade circuit offers a means of implementing a clock-controlled analog delay line in monolithic form. Operating in the sampled-data domain, it combines some of the advantages of both analog and digital circuits and appears to have a strong application potential in analog signal processing systems. In this paper, the analog operation of bucket-brigade circuits is described with respect to such practical operating considerations as bandwidth, dynamic range, linearity, power dissipation, baseband, signal recovery, a clock waveform noise. Experimental results from p-channel MOSFET and n-channel JFET brigades are presented.

New monolithic high-speed analog delay lines

Bucket-brigade circuit implementation with junction or metal-silicon field-effect switching elements provides good low- and high-frequency performance at low clocking voltages with high packing density, simple processing, and good stability.

Charge-coupled imaging devices: Experimental results

The design and fabrication of a 96-element 3-phase linear charge-coupled device are described. A transfer efficiency of ∼95 percent over 288 transfers at a 1-MHz clock rate was measured. The use of the device as an analog delay line is demonstrated and its imaging properties are illustrated with reproductions of black and white text and a picture with gray scale. The results demonstrate the feasibility of using self-scanned imaging devices in practical applications. Configurations are presented for both an improved linear and an area imaging device. In both cases the problem of image smear, which occurs if stored charge is transferred along the light-sensitive region and if significant light integration takes place during this transfer, can be avoided.