A 500-stage CCD transversal-filter for spectral analysis

The operation and design of 500-stage charge-coupled device (CCD) transversal filters are described. The filters have been mask programmed for implementing two spectral analysis techniques: 1) bandpass filtering and 2) Fourier analysis using the chirp z transform (CZT) algorithm. The bandpass filter has a measured fractional 3 dB bandwidth of 0.0108 and 38 dB sidelobe rejection. The dynamic range is 75 dB with less than 45 dB total harmonic distortion. A sliding transform is defined which is useful for calculations of the power spectral density and is shown to be particularly advantageous in a CCD-CZT implementation. Using the sliding transform, a 500-point spectrum is calculated using CCD´s with resolutions which can be varied from 1-200 Hz. The dynamic range of the power spectral output was measured to be 80 dB. A discussion is given of the performance limitation of a general CCD filter due to the inherent characteristics of the device. The results are evaluated for the 500-stage devices described above and indicate that sample rates from 25 Hz to 10 MHz are possible with a dynamic range approaching 100 dB while retaining high linearity.