A compact bidirectional reconfigurable 2nd-order low-pass filter for 5G FR2 applications

This paper presents a novel architecture of a second-order bidirectional low-pass filter (LPF) and compares it with its conventional – (unidirectional) – version. In phased array systems, both of reception (RX) and transmission (TX) chains are physically separated in order to work alternatively – they operate in time division duplexing (TDD). Hence, each baseband analog LPF is usually alternatively addressed with switching components to operate within a selected mode. By doing so, the silicium is not efficiently used – when a given filter operates, the other is turned off. To address this issue, bidirectional architectures seem to be perfect candidates. They guarantee a bilateral operation mode sharing the same electrical nodes. A bidirectional filter was designed in GF22nm FDSOI (Fully Depleted Silicon-On-Insulator). It exhibits −0.54, −0.58, −0.69 and −0.9dB in-band gain, depending on the chosen bandwidth (BW) configuration (50-100-200 and 400MHz respectively), a DC power of 2mW, an output integrated noise (OIN) ranging from 485 to 325$\mu V_{rms}$, an IIP3 varying from 20.8 to 14.3dBm and occupies a silicium area of 0.0055mm
²
.