Charles M. Puckette

The design and operation of practical charge-transfer transversal filters

Some of the design considerations for charge-transfer split-electrode transversal filters are discussed. Clock frequency, filter length, and chip area are important design parameters. The relationship of these parameters to filter performance and accuracy is described. Both random and tap weight quantization errors are considered, and the optimum filter length is related to tap weight error. A parallel charge-transfer channel, which balances both capacitance and background charge, and a coupling diffusion between split electrodes greatly improves accuracy. A one-phase clock is used to simplify the readout circuitry. Two off-chip readout circuits are described, and the performance of two low-pass filters using these readout circuits is given. Signal to noise ratios of 90 dB/kHz and an overall linearity of 60 dB have been achieved with this readout circuitry.

A VLSI demodulator for digital RF network applications: theory and results

An all-digital demodulator/detector which is suitable for both analog FM and digital phase/frequency modulations is presented. The system uses complex sampling, which employs a single A/D (analog/digital) converter to sample the signal at an intermediate frequency (IF) and produce baseband in-phase (I) and quadrature phase (Q) signals, and a simplified technique for reducing the effect of the I/Q timing misalignment usually associated with this approach. The system also includes two detectors which operate simultaneously to provide noncoherent and differentially coherent detection, as well as automatic gain control (AGC) and automatic frequency control (AFC). The flexibility afforded by the two concurrent detectors in this all-digital system is shown to make it suitable for a wide range of applications. The theory behind the demodulator/detector system is described, and an implementation using a 1.25- mu m bulk CMOS VLSI process is presented. Methods are shown for extending and improving the I/Q sampling misalignment correction technique, as well as for reducing the A/D sampling rate for a given IF frequency. Simulation and experimental results illustrate system performance for both analog and digital modulations. >

Active bandpass filtering with bucket-brigade delay lines

Bucket-brigade delay lines have been used to build a tunable active bandpass filter. Experimental results showing the dependence of center frequency and bandwidth on the delay-line clock frequency, and the dependence of the center frequency and the Q of the filter on internal gain parameters are presented.

Programmable Bandpass Filter and Tone Generator Using Bucket-Brigade Delay Lines

Bucket-brigade devices have been used to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion. The filter response characteristics, i.e., center frequency and bandwidth, depend on the circuit parameters of gain and clock frequency, both of which may be electronically controlled. By using a variable clock signal, 1023 frequencies can be accurately selected by the proper setting of ten switches. The selected clock frequency uniquely determines the center frequency of the bucket-brigade filter. The programmable feature of the clock circuit, therefore, allows the convenient selection of the center frequency of the bandpass filter. A slight modification to the programmable bandpass filter converts it into a programmable oscillator. Thus, any one of 1023 tones can be generated by the proper setting of the switches. A device that exhibits both filter and oscillator functions has been demonstrated in the laboratory.

Bucket-brigade transversal filters

The bucket-brigade delay line (BBDL) is a sampled data circuit in which signal samples are stored and manipulated as packets of charge under the control of a digitally generated clock. The clock-controllable time delay function that is realized by the BBDL may be used to implement a number of signal processing functions. The tapped delay line or transversal filter structure is of particular interest, however, since it has wide application in the field of signal processing. The implementation of transversal filters via BBDLs is examined. The impact of nonideal delay line parameters on filter performance is considered and the results of computer simulations are presented. The practicability of monolithic transversal filters is demonstrated and the performance of experimental filters is described.

High predictive accuracy for detection of left main coronary artery disease by antilog signal processing of two-dimensional echocardiographic images

Two-dimensional echocardiography has been used to image the left main coronary artery. We have successfully imaged the left main coronary artery in 16 of 19 patients with left main coronary artery disease (LMCAD) and in 14 of 18 control patients using a dynamically focused 3-1/2 MHz experimental phased array sector scanner. Images were displayed with standard logarithmic compression grey scale allocation and with a modified antilog curve which enhances high intensity echoes. All of the 16 patients with LMCAD were identified from the antilog processed image. Only 1 of the 18 control patients had a false positive study. Modified antilog processed images provide high sensitivity (100%) and specificity (93%) for detecting LMCAD. This noninvasive technique could be used to screen patients for the presence or absence of LMCAD.

Bucket-Brigade Transversal Filters

The bucket-brigade delay line (BBDL) is a sampled data circuit in which signal samples are stored and manipulated as packets of charge under the control of a digitally generated clock. The clock-controllable time delay function that is realized by the BBDL may be used to implement a number of signal processing functions. The tapped delay line or transversal filter structure is of particular interest, however, since it has wide application in the field of signal processing. The implementation of transversal filters via BBDLs is examined. The impact of nonideal delay line parameters on filter performance is considered and the results of computer simulations are presented. The practicability of monolithic transversal filters is demonstrated and the performance of experimental filters is described.

Charge-transfer analog memories for radar and ECM systems

Charge-transfer devices (CTDs) offer new opportunities in analog signal processing since they provide analog memory in integrated circuit form. In this paper the successful application of serial charge-transfer structures to radar and to electronic countermeasure systems is described. The design and operation of a three-pulse, 50 dB clutter-suppression charge-transfer radar moving target indicator (MTI) and the implementation of a charge-transfer memory for radar electronic countermeasures (ECM) are discussed, and experimental results are presented.

An experimental TV ghost-suppressor circuit using charge-transfer devices

The rapid development of charge-transfer technology has fostered many new applications of charge-transfer devices (CTDs) in the field of analog-signal processing. In this paper, the realization of a TV ghost-suppressor circuit by means of a pair of 64-stage p-channel MOS bucket-brigade circuits is described and experimental results are reported.

A programmable bandpass filter and tone generator using bucket-brigade delay lines

Bucket-brigade devices have been used to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion. The x It) filter response characteristics, i.e., center frequency and bandwidth, + I depend on the circuit parameters of gain and clock frequency, both e2(t- U of which may be electronically controlled. + By using a variable clock signal, 1023 frequencies can be ac- I e0%, curately selected by the proper setting of ten switches. The selected clock frequency uniquely determines the center frequency of the bucket-brigade filter. The programmable feature of the clock circuit, DELAND therefore, allows the convenient selection of the center frequency u It-T,) of the bandpass filter. A slight modification to the programmable bandpass filter converts it into a programmable oscillator. Thus, any one of 1023 tones can be generated by the proper setting of the switches. A device that ex- D hibits both filter and oscillator functions has been demonstrated in the laboratory.