Time Delay Circuit Research Articles

A synthetic time-delay circuit in mammalian cells and mice

Time-delay circuitries in which a transcription factor processes independent input parameters can modulate NF-kappaB activation, manage quorum-sensing cross-talk, and control the circadian clock. We have constructed a synthetic mammalian gene network that processes four different input signals to control either immediate or time-delayed transcription of specific target genes. BirA-mediated ligation of biotin to a biotinylation signal-containing VP16 transactivation domain triggers heterodimerization of chimeric VP16 to a streptavidin-linked tetracycline repressor (TetR). At increasing biotin concentrations up to 20 nM, TetR-specific promoters are gradually activated (off to on, input signal 1), are maximally induced at concentrations between 20 nM and 10 microM, and are adjustably shut off at biotin levels exceeding 10 microM (on to off, input signal 2). These specific expression characteristics with a discrete biotin concentration window emulate a biotin-triggered bandpass filter. Removal of biotin from the culture environment (input signal 3) results in time-delayed transgene expression until the intracellular biotinylated VP16 pool is degraded. Because the TetR component of the chimeric transactivator retains its tetracycline responsiveness, addition of this antibiotic (input signal 4) overrides biotin control and immediately shuts off target gene expression. Biotin-responsive immediate, bandpass filter, and time-delay transcription characteristics were predicted by a computational model and have been validated in standard cultivation settings or biopharmaceutical manufacturing scenarios using trangenic CHO-K1 cell derivatives and have been confirmed in mice. Synthetic gene circuitries provide insight into structure-function correlations of native signaling networks and foster advances in gene therapy and biopharmaceutical manufacturing.

Research and design of the protection circuits in LD controller

According to the parameters and applications of laser diode (LD), three protection circuits were designed: the time-delay soft-start protection circuit, the power-on impulse protection circuit and the limit-current protection circuit. In this article, the structure and the principle of every protection circuit have been detailed. From several tests and feedbacks from customers, the expected goals have been completed.

A DC to 10-GHz 6-b RF MEMS time delay circuit

A 6-b radio frequency (RF) microelectromechanical system (MEMS) time-delay circuit operating from dc to 10 GHz with 393.75-ps total time delay is presented. The circuit is fabricated on 250-/spl mu/m-thick alumina and uses metal contacting RF MEMS switches to realize series-shunt SP4T switching networks. The circuit demonstrates 1.8+/-0.6 dB of loss at 10 GHz and has linear phase response across the entire band with accuracy of better than a least significant bit for most states.

Neural Circuitry for Recognizing Interspike Interval Sequences

Sensory systems present environmental information to central nervous system as sequences of action potentials or spikes. How do animals recognize these sequences carrying information about their world? We present a biologically inspired neural circuit designed to enable spike pattern recognition. This circuit is capable of training itself on a given interspike interval (ISI) sequence and is then able to respond to presentations of the same sequence. The essential ingredients of the recognition circuit are (a) a tunable time delay circuit, (b) a spike selection unit, and (c) a tuning mechanism using spike timing dependent plasticity of inhibitory synapses. We have investigated this circuit using Hodgkin-Huxley neuron models connected by realistic excitatory and inhibitory synapses. It is robust in the presence of noise represented as jitter in the spike times of the ISI sequence.

A new approach of dead-time compensation for PWM voltage inverters

It is essential to insert a switching delay time in sinusoidal pulsewidth modulation (PWM) voltage-fed inverters to prevent a short circuit in the dc link. This causes the well known dead-time effect which is detrimental to the performance of the output voltage. Many compensation schemes were proposed to overcome the drawbacks. In this paper, based on a systematic approach, a new approach to accurately compensate the dead-time effect is presented. The system analysis and compensation synthesis are straightforward without averaging the output voltage deviation. The model of the PWM voltage inverter with a time delay circuit leads us to a systematic approach of compensation. The simulation responses and experimental results show the validity of the analysis and verify the effectiveness of the proposed compensation method.

Time-delay circuit model of high-speed p-i-n photodiodes

We have proposed an equivalent electric circuit model of p-i-n photodiode including the transit-time effect for performance evaluation of optical systems through the aid of a SPICE-like circuit simulator. No model-dependent close-form expression is necessary in our model. Its validity is shown for the analysis of frequency response in simplified p-i-n photodiodes with different lengths of i-region under uniform or nonuniform illumination. Its application to eye-diagram analysis is demonstrated also.

Smart TDI readout circuit for long-wavelength IR detector

A smart time delay and integration (TDI) readout circuit is suggested which performs background suppression, cell-to-cell non-uniformity compensation, and dead pixel correction. Using the smart TDI readout circuit, the integration capacitor area occupying almost the whole area of a unit-cell can be reduced to one-fifth and transimpedance gain can increase by five times. From measurement results, it is found that the skimming current error for a few hundred nA background current is <1.25 nA corresponding to LSB/2 of ADC and the non-uniformity introduced by cell-to-cell background current variation is reduced to 1.02 nA.

Noise Generation due to Time Delay Circuits

A quiet current with subshot noise is a regulated electron flow. When a time delay circuit, i.e. a low-pass filter is inserted into the flow, noise is generated in the high frequency region. By using a transistor circuit the noise generation due to the time delay is observed. A simple theoretical model explains the observed noise spectrum.

Generating chaos in Chua's circuit via time-delay feedback

A time-delay chaotification approach can be applied to the Chua's circuit by adding a small-amplitude time-delay feedback voltage to the circuit. The chaotic dynamics of this newly derived time-delay Chua's circuit is studied by theoretical analysis, verified by computer simulations as well as by circuit experiments.

August Toepler — The first who visualized shock waves

The scientific investigation of the nature of shock waves started 130 years ago with the advent of the schlieren method which was developed in the period 1859–1864 by August Toepler. At the very beginning applied to the visualization of heat and flow phenomena, he immediately turned to air shock waves generated by electric sparks, andsubjectively studied the propagation, reflection and refraction of shock waves. His new delay circuit in the microsecond time regime for the first time made it possible to vary electrically the delay time between a spark generating a shock wave and a second spark acting as a flash light source in his chlieren setup. In 1870 Toepler, together with Boltzmann, applied Jamin's interferometric refractometer and extended the visualization to very weak sound waves at the threshold of hearing. Toepler's pioneering schlieren method stimulated Ernst Mach and his team toobjectively investigate the nature of shock waves: they improved Toepler's time delay circuit; continued the study on the reflection of shock waves; introduced shadowgraphy as a modification of the schlieren method; photographed the propagation of shock waves generated by an electric spark and by supersonic projectiles, and improved interferometry. Based on a large number of original documents the paper illuminates the concomitant circumstances of the invention of the schlieren method and its first applications by others.

The combination of dual waveband (3?5um and 8?12um) thermal image

For the two colour (3∼5um and 8∼12um) sensor fusion, an optical method can replace the electric time delay and integration (TDI) circuit. During the fusion process, there exits an optimal relative gain setting between the two preamplifiers of the sensors. The optical method can provide a real time (30 frames) single enhanced dual band thermal image with an improved signal to noise ratio and better system performance.

System implementation of a serial array of sprite infrared detectors

The incorporation of a new SPRITE IR detector array in a scanning thermal imager is described. The new array contains an increased number of detectors in the along-scan direction. Use of the array, together with appropriate time delay and integration circuits, gives a theoretical improvement in thermal sensitivity of a factor of two. Experimental results demonstrating this improvement are presented.

A Wideband Sampling Wattmeter1

The design and operation of a wideband sampling wattmeter capable of measuring distorted power signals with fundamental frequencies from 1 Hz to 10 kHz and harmonics up to 100 kHz is described. The microprocessor control led wattmeter uses asynchronous sampling of the voltage and current signals. The errors associated with this type of operation are described as are various methods of correcting some of these errors. The wattmeter uses both a hardware multiplier-accumulator and a direct-memory-access unit to capture the data. Programmable time delay circuits are used to compensate for differential time delays between the input channels. Performance checks show that measurement uncertainties of less than ±0. 1 percent of full-scale range (FSR) are obtainable.

Electronically adjustable delay for Josephson technology

An electronically adjustable time delay circuit for superconducting technology is reported. In conjunction with a superconducting sampler on the same chip, the delay circuit has allowed measurement of waveforms with an apparent resolution of 8.5 ps. The delay circuit permits flicker-free oscilloscope displays of fast waveforms, and provides the circuitry needed for further speed advances in superconducting sampling and other ultra-fast measurement techniques.

Device for producing chorus effects

A device for producing a chorus effect for an electronic musical instrument. The device has two sets of parallel time delay modulating circuits with each set having two circuits therein and the circuits being adapted to have the musical tones from the electronic musical instrument supplied thereto. Saw-tooth wave generators are coupled to the respective time delay modulating circuits for supplying the respective time delay circuits in each set with a saw-tooth modulating wave having a gradually increasing slope and a sharply decreasing slope, the saw-tooth wave supplied to one circuit in the set having the gradual slope increasing in the positive direction and the saw-tooth wave supplied to the other circuit in the set having the gradual slope increasing in the negative direction so that the waves in the set have opposite polarities, and the saw-tooth waves for one set of modulating circuits being 180° out of phase with the saw-tooth waves for the other set of time delay modulating circuits. A plurality of amplitude modulating circuits are provided, one coupled to each of the time delay modulating circuits, and modulating wave generators are coupled to the amplitude modulating circuits for supplying modulating waves to the amplitude modulating circuits for making the output from the respective time delay modulating circuits a minimum when the direction of the saw-tooth waves for the corresponding time delayed modulating circuits is sharply decreasing. Mixing means mixes the outputs of the amplitude modulating circuits.

Quantitative schlieren visualization

Using a closed circuit television camera (CCTV), a method is developed to obtain quantitative sound pressure measurements directly from the sound field imaged in a schlieren system. By using the exact time format of the composite video signal and a series of time delay circuits, it is possible to take vertical intensity scans of a schlieren image at any position on the TV raster. The method uses the camera's horizontal blanking pulse to trigger a broadband, high-speed sample-hold amplifier. This amplifier is triggered to sample each horizontal scan line at a selected time in the horizontal scan sweep and to feed this value into a transient recorder. The signal is digitized, and a continuous analog voltage signal corresponding to the black-white information from a schlieren image is displayed on a scope. The same analog signal is also plotted on an X-Y recorder. The schlieren system can be operated using only a single calibration curve at each frequency. The curves plotted applied transducer voltage against the video output level. Thus, by comparing the video output levels for several vertical image intensity scans on a schlieren image, relative sound pressure measurements are routinely obtained.

Quantitative schlieren visualization

Using a closed circuit television camera (CCTV), a method was developed to directly obtain quantitative sound pressure measurements from the sound fields imaged in a Schlieren system. By using the exact timed format of the composite video signal and a series of time delay circuits, it was possible to take vertical intensity scans of a Schlieren image at any position on the television raster. The method used the camera's horizontal blanking pulse to trigger a broadband, high-speed sample-hold amplifier. This amplifier was triggered to sample each of the horizontal scan lines at a selected time in the horizontal scan sweep and to feed this value into a transient recorder. The signal was digitized and a continuous analog voltage signal corresponding to the black-white information from a Schlieren image was displayed on a scope. The same analog signal was also plotted on an X-Y recorder. The ease with which the Schlieren system can be operated is evident from the fact that only a single calibration curve at each frequency was needed. The curves plotted applied transducer voltage against the video output level. Thus, by comparing the video output levels for several vertical image intensity scans on a Schlieren image, relative sound pressure measurements were routinely obtained.

A Novel Trigger Scheme for Thyristor Operating Under Variable-Frequency Anode Supply

A novel trigger control scheme for thyristors operating under variable-frequency anode supply is described. The scheme uses a zero crossing detector and a novel time delay circuit. A few applications are suggested.

A Wide-Range Voltage-to-Time Converter

The principle of operation of a novel linear time-delay circuit is described. The circuit is based on the Miller integrator principle and incorporates the ramp-generating function, the amplitude comparison, and the resetting action into a gate-generating circuit. The linearity of the sweep voltage is the highest possible that can be obtained with one transistor ramp generator. Wide delay range with a single timing capacitor and high duty cycle is obtained.

Generalised-phase-comparator techniques for distance protection. Basis of their operation and design

The basic theory and principle of operation of a new method of phase comparison for use in distance protection schemes is outlined. It is shown that the angular limits of comparison between signal pairs are determined by the setting of time-delay circuits, and that the new device is extremely variable. Comparator circuitry based on transistor logic is described in detail, and the effect of setting errors is analysed. The output from the device progresses from a short-duration pulse at the threshold to one of fixed duration, and the implications of such a response with regard to the overall performance are established. An introduction to generalised multi-input comparators is given, which, unlike conventional multisignal techniques, can be adjusted to give dissimilar limits of comparison between each signal pair.