12.2 Extended Feature Set Application Schematic

Application circuit for extended RF front end functions.

SAM R30 has build in hardware support for antenna diversity and active range extension front end circuits. The digital control signal outputs from RF212B are multiplexed to SAM L21 port pins. The Front End Control Signal Interface allows the free selection of six alternative IO pins for the four RF212B DIG signals. For that reason no particular pin number had been assigned in the schematic drawing. The internal multiplexer allows a pin selection for best application match instead.

A large number of higher integrated front end modules are available in the market for many different application scenarios. The schematic drawing below shows a contrived front end that would make use of all four DIG signals. DIG4 is an inverted signal of DIG3 and in the same way DIG2 is an inverted signal of DIG1. For DIG2 there is also a function as a time stamping trigger or interrupt available.

With the signals DIG1 and DIG2 provision is made for antenna diversity operation. The detailed description for the antenna diversity function and its configuration can be found in the extended feature set section for the RF212B. RF switch ICs do often require a signal pair with one line inverted. Such switches can be directly controlled without additional glue logic. The switch on/off time should be selected to be below 100ns.

The signals DIG3 and DIG4 are designated to switch the front end functions in between receive and transmit. Typical functions are path selection as well as PA or LNA enable and disable functions.