I see four ADF7024 radio boards available to order. What is the difference between these boards?
There are four daughter board models as described in the following table. Two board layouts are used; one which uses a separate transmit and receive match, and one which uses a combined transmit and receive match. Two frequency ranges are covered: 862-928MHz and 431-435MHz. Also note that the ADF7024 daughter boards require the EVAL-ADF7xxxMB4Z mother board for evaluation.
Combined Tx/Rx Match (EVAL-ADF7024DB2Z and EVAL-ADF7024DB4Z)
The combined Tx and Rx matching configuration is shown in the following figure.
The ADF7024 is equipped with an internal Tx/Rx switch that facilitates the use of a simple, combined, passive Tx/Rx matching network where the transmit and receive paths can be connected together without the need for an external switch. While this offers a simple and cost effective solution it makes optimization of the matching network more complex as the off impedances of the PA and LNA must be considered. The off impedances can lead to a small loss in transmit power and degradation in receiver sensitivity in comparison with a separate Tx/Rx match. On the EVAL-ADF7024DB2Z and EVAL-ADF7024DB4Z, the typical loss in transmit power is <1 dB, and the degradation in sensitivity is <1 dB, when compared with the separate Tx/Rx matching topology.
Separate Tx/Rx Match (EVAL-ADF7024DB1Z and EVAL-ADF7024DB3Z)
The separate Tx and Rx matching configuration is shown in the following figure.
In designing this matching network, it is not necessary to consider the off impedances of the PA and LNA; therefore, achieving an optimum match is less complex than with the combined PA and LNA match. An external transmit and receive antenna switch can be used to combine the transmit and receive paths to allow connection to an antenna.