A programmable bandpass array using floating-gate elements

In order to meet the demands of low-power real-time audio signal processing, we present a programmable array of bandpass filters using floating-gate transistors. This bank of analog bandpass filters can be placed before an analog-to-digital converter to perform a frequency decomposition of an audio signal and also allow for analog preprocessing before being transformed into the digital domain. Individual filter taps can easily be tuned to any given frequency and bandwidth because capacitively coupled current conveyers (C/sup 4/s) are used with floating-gate transistors as biasing elements. Offsets and mismatches within the circuit elements are shown to be inconsequential because they can be accounted for and programmed out.

1. ANALOG AUDIO PROCESSING ADVANTAGES

The tendency in the signal processing realm for dealing with incoming audio signals is immediately passing the analog audio signal to an analog-to-digital converter (ADC) so that the signal can be manipulated digitally. Typically, the FFT of the signal is performed digitally so that the individual subbands can be manipulated. Digital signal processing is invoked as early as possibly since it has many advantages, and the greatest is the ease of programming a digital system to meet the given requirements. Typically, the FFT of the signal is one of the first digital computations so that the individual subbands can be manipulated. Fig. 1. (a) Collaborative analog and digital signal processing blurs the boundary of where to place the conversion from analog to digital. Performing some of the signal processing with low-power real-time analog circuitry alleviates some of the burden of the DSP allowing the DSP to perform more complex computations or a smaller DSP to be used. (b) The analog signal processing (ASP) block we present in this paper consists of an array of programmable bandpass filters (shown in grey). Further signal processing can be performed on each subband signal before either recombining them or sending them through small ADCs and then on to the DSP