The Tapped Analog Delay

Abstract

The tapped analog delay (TAD) unit is a newly developed MOS integrated circuit designed specifically for the realization of nonrecursive filters. Such a device greatly simplifies the design of low-frequency filters. One such device has twelve delay taps, each tap separated from its neighbor by two sample periods. The analog input signal is sampled and each sample sequentially stored on one of a group of capacitive storage cells from which it is read out 2k sample periods later, where k is the tap number. Such a design avoids the problems of signal degradation and sampling-rate sensitivity which occur with charge-transfer devices. Outputs are buffered to provide flexibility and freedom from interaction. The basic function performed by a tapped line is that of convolution. As the incoming signal propagates down the line, it is convolved with the tap-weight function. The timedomain output is a measure of the correlation between the input and the function described by the tap weights.Device characteristics are reviewed and performance illustrated in a variety of filter designs including lowpass and bandpass designs. 'Design procedures are reviewed and a comparison made between theoretical and realized performance. INTRODUCTION,

Charge-Coupled Device (CCD) Adaptive Discrete Analog Signal Processing

“…The CCD analog shift register processes discrete analog samples of input data by the propagation of charge packets in synchronization with a signal clock [lo]. SCD transversal filters with fixed analog tap weights have been implemented with the split-electrode weighting technique [l I] and fixed conductance methods [12] - [14]. In the former, a CCD delay line becomes a transversal filter by splitting one of the electrodes in each stage delay and placing a differential current or charge amplifier in the clock line.…”

Mass spectrometer ion multiplier noise filter based on an analog delay device

“…The recent introduction of the tapped analog delay device offers the possibility of effecting digital-type filtering in hardware. Such devices allow running, weighted averages of an input analog signal to be calculated in real time, and output in analog form (for general background see references [6][7][8]. In this report, we detail how a tapped analog delay device can be used to remove the noise on the output line of the ion multiplier of a gas chromatograph/mass spectrometer.…”

Audio signal processing with transversal filters

“…The contemporary transversal filter is physically realized either as a tapped analog delay line sampled synchronously at discrete times (7) or in completely digital format. For use in conjunction rith analog systems, the former configuration avoids the penalties of A/D and D/A conversions at the possible expense of dynamic range or signal-to-noise ratio.…”