 fre- quency. Radar applications with large bandwidths in particular suffer inaccuracies due to this effect. The latter equation can be expressed in time domain using time delays instead of frequency offsets T = d/c sin 0. This means that the frequency dependency is elimi- nated, if the setup is fitted with delay lines instead of phase shifters. The performance of the analog architecture can be further improved by additionally changing the magnitude of the signals feeding the antennas [56]. Analog signal processing typically implies that beamforming is carried out on a per-carrier basis. For the downlink transmission, this implies that it is not possible to frequency- multiplex beamformed transmissions to devices located in different directions relative to the base station. In other words, beamformed transmissions to different devices located in dif- ferent directions must be separated in time. 4.1.9.3.2 Digital Beamforming While analog beamforming is generally restricted to one RF chain even when using large number of antenna arrays, digital beamforming in theory supports as many RF chains as there are antenna elements. If suitable precoding is performed in the digital-domain base- band, this would yield higher flexibility regarding the transmission and reception. The additional degree of freedom can be leveraged to perform advanced techniques such as multi-beam MIMO. These advantages result in the highest theoretical performance possible compared to other beamforming architectures. Fig. 4.64 illustrates the high-level digital beamforming transmitter architecture with multiple RF chains. Uneven beam is a problem Data stream 1 RF chain Data stream 2 Digital RF chain baseband processing precoding Data stream N RF chain Figure 4.64 Digital beamforming transmitter architecture. New Radio Access Physical Layer Aspects (Part 2) 567 of analog beamforming architectures using phase shifters. This is a drawback considering 5G plans to make use of large bandwidths in the mm Wave bands. Digital control of the RF chain enabl