2.4 GHz Bi-Directional Amplifier

The project illustrates how a bi-directional 2.4 GHz amplifier can be added to a Proxim Symphony that may sell at a cheaper price.

Bi-directional refers to the amplifier being mounted at the antenna in order to help reduce any cable loss while the amplifier automatically switches between receive and transmit modes. The use of readily available materials and components reduces the cost. A logic level indication of transmit is sent to the amplifier through a length of low cost coaxial cable instead of a complicated RF sensing transmit/receive switch.

This amplifier has a final RF power output around 1.3W while the receive gain is around 16dB. The overall power gain should be lowered when the device is used on direct sequence spread spectrum systems so as to keep the RF power amplifier in its linear region. This can be done by slightly attenuating the RF input power.

A suitable waterproof casing encloses the entire amplifier board while the whole device is mounted right next to the antenna installation. The DC power for the amplifier is inserted to the RF input feed line which runs LMR-400 coaxial cable which require the modification of Symphony.