Large Bandwidth Digital Phase Shifters With All-Pass, High-Pass, and Low-Pass Networks

Large bandwidth phase shifters using a combination of an all-pass network (APN), a high-pass network (HPN), and a low-pass networks (LPN) are presented. An exact equiripple phase-shift response is first derived for an infinite series of an APN using phase superposition. However, the realization is impractical and the topology is modified by truncating the series of the APN. A pair of properly designed HPN and LPN is added to compensate for the phase error introduced by the truncation. To verify the topology, phase-shifting networks of 90
$^\circ$
and 180
$^\circ$
with a bandwidth from less than 100 MHz to more than 2 GHz are designed and measured. A frequency ratio of 35 and 25 has been achieved by the 90
$^\circ$
and 180
$^\circ$
phase-shifting networks, respectively.