A VHF switched-capacitor band-pass filter using GaAs MESFET IC technology

The authors describe the design of a narrowband, high-frequency GaAs IC switched-capacitor filter-based on a commutating RC circuit topology. They present measured performance of a two-section band-pass filter circuit with a center-frequency tunable to over 220 MHz with a -3 dB bandwidth of less than 2.6 MHz. The tuning frequency is controlled by a single-phase external clock signal at about two or four times the center-frequency, from which four-phase clock switching signals are generated on-chip. These results demonstrate that the broad tuning range and frequency stability of switched-capacitor filters is achievable well into the VHF frequency region. Such circuits can provide higher level of integration for fixed-frequency filters, clock recovery circuits, and for agile filtering in broadband communications and radar systems.<>