A doubly balanced
transceiver system having a transmit terminal (TX), a receive terminal (RX), and an an antenna terminal (ANTENNA), 180° hybrids (201, 240), 90° hybrids (204, 304, 235 and 335), a power
amplifier (230, 330) and a RX / TX switch (220) for disabling the power
amplifier so that signals received at the
transmitter are reflected to the receive terminal (RX). The 180° hybrids (201, 240) preferably split and re-combine signals into parallel paths. A
loopback test mode is preferably provided by use of an
antenna isolation switch (302) to enable a power detect terminal (POWER_DETECT). This eliminates pricey and problematic GaAs switches, and allows the use of low cost
silicon for the power
amplifier. The doubly balance architecture also has the
advantage of eliminating common-mode
noise, and reflection problems with the PA
gain stages. Additionally, greater power can be extracted from the power amplifier. Further the arrangement has less
insertion loss compared to a GaAs switch. Also, dependant upon
system specifications, it may be possible to eliminate
harmonic filtering at the power amplifier output.