A Lumped Component Programmable Delay Element for Ultra-Wideband Beamforming

We introduce a ladder filter based programmable time delay element for beamforming in Ultra-Wideband (UWB) systems. When compared to conventional methods based on the tapped delay line architecture, our technique achieves lower power dissipation, better area efficiency, and finer delay and gain resolution more efficiently. The proposed architecture is more scalable, has better parasitic absorption capability and highly programmable with delay and gain resolution dependent only on transconductor resolution. A prototype delay line designed for the 3.1-10.6 GHz UWB range achieves a delay range of 80 ps with 0.5 ps resolution and a gain range of -30 dB to +10 dB with 0.15 dB step. Fabricated in a 0.25 mu m SiGe BiCMOS process, the delay element occupies an active area of 1mm(2) and consumes 47mW from a 2.5V supply. A four antenna beamforming system using the delay element can achieve scanning range of +/- 51 degrees with resolution of 0.86. for antenna spacing of 10mm.