An acoustic charge transport digitally programmable transversal filter

A monolithic 64-tap digitally programmable analog transversal filter is described that uses an acoustic charge transport (ACT) tapped delay line and integrated GaAs MESFET circuits for coefficient storage and tap weight circuitry. The device has 6-b tap weights, an input sampling rate of 360 MHz, and an output tap spacing corresponding to an output sampling rate of 130 MHz. This results in the effective execution of 8×10⁹ multiply and sum operations per second in a 38-mm² chip that dissipates less than 2 W. This effective computational rate is limited in the present design by the spacing of the ACT delay line taps, which is dictated by the geometry of the tap weight circuits. The chip uses fully random-access tap weight memory, which is easier to interface to typical digital controllers than the usual shift-register storage approach. Tap address and tap weight data are applied as parallel 6-b words, and the data work is clocked into the address location by the application of an enable pulse. The tap weight circuits use monolithic capacitors and GaAs MESFET analog switches to realize a multiplying converter based on a C/2C ladder configuration with a sign-and-magnitude tap weight word format. A ladder accuracy of 7 b is achieved by compensating the ladder component values for parasitics