**2. PA-antenna Co-design architecture**

The principle of the Co-Design of a PA-Antenna block is based on the fact that the junction of the antenna and the amplifier must be done with as little loss as possible, which is why it is very objective for us to work on each one. Equipment with a reference impedance which will facilitate the junction of the two because the option of designing a matching network no longer becomes a necessity. So let us say the stages of Co-design illustrated in the figure below (**Figure 1**).

In the chain of transmission of wireless communication systems, the proposed Co-Design Block is of capital importance because the amplifier will have the role of taking a weak signal as input and producing a high intensity signal at the output.

**Figure 1.** *PA-antenna block Co-design principle.*

*Co-Design Block PA (Power Amplifier)-Antenna for 5G Application at 28 GHz Frequency Band DOI: http://dx.doi.org/10.5772/intechopen.98653*

This signal will be recovered at the output by the antenna and radiates by it in the free space.
