A Consolidated-Cell Attenuator (CCA) Replacing Three Cascaded Cells for Compact Broadband CMOS Variable Attenuators

Abstract

This paper proposes a consolidated-cell attenuator (CCA) that replaces three conventional cascaded attenuation cells with a single integrated cell for compact broadband CMOS variable attenuators. Unlike conventional designs where multiple cells are cascaded to achieve fine resolution, the proposed CCA incorporates 1-dB, 2-dB, and 4-dB attenuation functions within a single cell by independently controlling three transistors, thereby achieving 3-bit attenuation (0–7 dB in nominal 1-dB steps) without cascading. Combined with an additional 8-dB π-type cell, the complete attenuator provides 0–15 dB range with nominal 1-dB resolution. Fabricated in 65-nm RFCMOS technology, the proposed CCA achieves a core area of only 0.0039 mm², which is significantly smaller than previously reported CMOS attenuators with comparable attenuation range. Measurements over DC–40 GHz demonstrate RMS gain and phase errors below 0.57 dB and 2.02°, respectively, with insertion loss of 1.1–2.9 dB—the lowest among comparable designs. These results confirm that the proposed CCA effectively addresses the area and loss penalties of conventional cascaded architectures.