An SDR duplex filter in SOI technology

A Software-Defined Radio (SDR) mobile handset must cover multiple frequency bands with different frequency division duplex distances. This calls for an adaptive duplexer, which needs a low-isolation device to create an initial isolation. Such a device is implemented in a 130 nm Silicon-on-Insulator (SOI) process. Its performance benefits from a high-Q laminated PCB inductor which has a measured inductance and Q-factor at 2 GHz of 1.19 nH and 125, respectively. The tunable low-isolation device provides an isolation exceeding 30 dB at both transmit and receive frequencies of each targeted four LTE frequency bands. The insertion loss from PA to antenna is below 2 dB in LTE band I. The implemented circuit occupies an area of 2.4 mm
²
.