Techniques are presented for making transversal filters using charge-coupled devices and bucket-brigade devices. In a CCD transversal filter, the delayed signals are sampled by measuring the current flowing the clock lines during transfer, and the sampled signals are weighted by a split electrode technique. In a BBD transversal filter, the delayed signals are `tapped' with a source follower whose load determines the weighting coefficient. Examples are given of CCD and BBD filters that are `matched' to particular signalling waveforms, and the limitations of charge-transfer devices in matched filtering applications are discussed. Finally, the application of CTD transversal filters to other signal processing functions is discussed.

Transversal filtering using charge-transfer devices

The use of charge-coupled devices for delaying analog signals is discussed and demonstrated. Some of the relevant operational factors of the CCD, such as the effect of transfer inefficiency, maximum delay, signal-to-noise ratio and power dissipation are presented. These show that devices with delays in the range 10/SUP -1/-10/SUP -6/s operating at frequencies up to several megahertz and having wide dynamic ranges are possible. Measurements of device frequency response, harmonic distortion, and transfer noise for a 250-element 2-phase device are presented. The use of both a linear and an area CCD to delay Picturephone video signals is shown. In the latter case a device having a serial-parallel-serial organization and holding 13780 charge samples at any given time was operated with a delay of 16.7 ms.

Use of charge-coupled devices for delaying analog signals

A probe cap for use with an ultrasound probe including a head portion and an acoustic surface is disclosed. In one embodiment, the probe cap includes a body that defines a cavity sized for releasably receiving the head portion of the probe therein. The probe cap body further defines a hole that is proximate the acoustic surface of the head portion. A compliant spacer component is disposed in the hole. The spacer component can include a hydrogel and provides an acoustic path between the acoustic surface and a tissue surface of a patient. The spacer component includes a skin contact surface that defines a concavity and is deformable against the tissue surface. Additional embodiments disclose various probe cap and accompanying needle guide designs for use in assisting a clinician with ultrasound probe use and needle insertion into a patient.

Support and cover structures for an ultrasound probe head

A probe cap for use with an ultrasound probe including a head portion and an acoustic surface is disclosed. In one embodiment, the probe cap includes a body that defines a cavity sized for releasably receiving the head portion of the probe therein. The probe cap body further defines a hole that is proximate the acoustic surface of the head portion. A compliant spacer component is disposed in the hole. The spacer component can include a hydrogel and provides an acoustic path between the acoustic surface and a tissue surface of a patient. The spacer component includes a skin contact surface that defines a concavity and is deformable against the tissue surface.

Spacers for use with an ultrasound probe

A low power ultrasound system for use in sonography applications, including vascular imaging, is disclosed. In one embodiment, the low power ultrasound system comprises a base unit that includes an image processor and a display. An ultrasound probe is operably connected to the base unit. The probe includes a head portion including an array of crystal transducers. A plurality of pulser/receiver modules that cause the transducers to emit ultrasonic transmit pulses are also included in the probe. The pulser/receiver modules are further configured to receive analog signals relating to ultrasonic echo receive pulses detected by the transducers. The probe includes a singular low noise amplifier that amplifies the analog signals, and an analog-to-digital converter that converts the analog signals to a digital signal. A wireless interface is included for enabling the digital signal to be wirelessly transmitted from the probe to the image processor of the base unit.

Low power ultrasound system

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.

Practical considerations for analog operation of bucket-brigade circuits

The application of charge-transfer structures to signal processing is currently generating considerable interest. In this letter, the implementation of a moving-target indicator by means of bucket-brigade delay lines is described, and some experimental results are presented.

Implementation of a moving-target indicator by bucket-brigade circuits

The effect of inherent device limitations on the analog operating characteristics of a bucket-brigade delay line will be considered. In particular, the bandlimiting effect of cascading a large number of stages in series will be described, and the means of accommodating or compensating for such limitations discussed.

http://ieeexplore.ieee.org/iel6/8286/25918/01155099.pdf

Analog operating characteristics of bucket-brigade delay lines

As a result of net loss (or gain) of charge to the substrate, the signal component at the output of a bucket-brigade circuit is subject to a direct-voltage shift which reduces the dynamic range of the device. Compensation for such level-shifting (of either polarity) can be provided by means of single additional m.o.s. devices placed at suitable intervals along the delay line.

Level-shift compensation in m.o.s. bucket-brigade circuits operated in an analogue mode

The range of applications of bucket-brigade circuits is limited by inherent device limitations. At present, the most severe of these appears to be a relatively poor charge-transfer efficiency, which results in a limited signal bandwidth. In this letter, the bandwidth characteristics of bucket-brigade circuits are described, and close agreement between computed and experimental results is shown.

M.B. Barron

Papers

Practical considerations for analog operation of bucket-brigade circuits

Implementation of a moving-target indicator by bucket-brigade circuits

Analog operating characteristics of bucket-brigade delay lines

Level-shift compensation in m.o.s. bucket-brigade circuits operated in an analogue mode

Bucket-brigade bandwidth characteristics