Walter J. Butler

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.

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.

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.

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.

Analog operating characteristics of bucket-brigade delay lines

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.

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.