1. Introduction

It is worth mentioning that an array with N elements used both at the TX and at the RX side does provide \(N^3\) benefit in the link budget if and only if compared to a single antenna with an area A / N. Such a comparison is obviously not fair. When an antenna with the same area of the full array is used in combination with an ideal big PA that delivers N times larger output power, the \(N^3\) benefit disappears. However, (1) phased arrays enable electrical beam steering and do not need a mechanical actuator. Therefore, highly directive communication between the base station and the user equipment would be possible, enabling spacial reused. This technique in combination with the classical frequency and time reuse is expected to significantly increase the capacity of the whole wireless system. And, (2) as it will be discussed in Chap. 7, implementing a big PA that delivers N times larger output power at mm-Wave might not be possible or may result in unacceptably low efficiency.

Low frequency with respect to the modulation bandwidth of the signal \(BW_{RF}\).

In this design example we consider a modulated signal bandwidth of 500 MHz. However, when the \(BW_{RF}\) is increased to 4.75 GHz, the SNR degradation due to PN does not change significantly.

It is worth mentioning that in this study we consider the effect of the PN of a single PLL on the SNR of the full system. When two PLLs with the same phase noise profile are used for the TX and RX paths, 3 dB better PN is needed to keep the same SNR.