power consumption is a concave function of array size except few exceptions that will be discussed in later paragraphs. The concavity comes from the trade-off between PA power and processing power in other circuits blocks for different antenna array sizes. In the figures, the range of antenna element number N for all scenarios is chosen to be close to green point, one that minimizes system power consumption. Taking a closer look at Dense Urban MBB use case in Figure 9, we have the following conclusions. Firstly, DA and FH have similar green point of array size when the same number of streams U is used, while green point of SA is much larger. This is due to the inefficiency of array gain (5) when SA splits antenna with sub-groups. The exception occurs in SA with U = 32 streams. When SA uses small antenna number and high multiplexing level, it effectively becomes a digital array. In fact, the green point for SA with U = 32 streams occurs at N = 32. It requires RF-chain to be connected to one antenna which makes SA a fully digital array. DA Processing IC LO/Buffer To PA DAC DAC SerDes DAC/ LPF Circuits Block PreDriver Mixer Port/ T-Line Gain/IL (dB) - - 13 -2 Output (dBm) -14 -6 7 5 OP1dB (Bm) - - 17 - (a) SA Processing IC LO/Buffer Splitter and IL Compensation 0 dBm DAC D/A SerDes Circuits Block To PA 1:4 1:4 DAC/ Wilk.+ RF Wilk.+ Mixers LPF T-Line Amp. T-Line VM Pre- T-Line/ Driver Port Gain/IL (dB) - - -(8+2) 10 -(8+2) 2 21 -2 Output (dBm) -14 -6 -16 -6 -16 -14 7 5 OP1dB (dBm) - - - 4 - -4 17 - (b) FH Processing IC LO/Buffer SerDes Circuits Block FH Combining IC With Multi-Stage IL Compensation Multi-Stage IL Compensation 1:4 DAC DAC 1:4 1:4 Wilk. Wilk. Wilk. DAC/ RF RF IQ and and and LPF Mixer T-Line Amp. T-Line Amp. T-Line 2:1 PS To PA 4:1 Wilk. Port/ RF RF Port/ Wilk. and and T-Line T-Line Amp. T-Line Amp. T-Line Gain/IL (dB) - - -(8+4) 12 -(8+3) 12 -(8+2) 2 -3 -(8+2) 12 -(8+2) 31 -2 Output (dBm) -14 -6 -18 -6 -17 -5 -15 -13 -16 -26 -14 -14 7 5 OP1dB (dBm) - - - 4 - 5 - -3 - - -4 - 17 - (c) Figure 8. the signal distribution budget example of three array architectures. (a) Distribution Budget in DA Architecture, (b) Distribution Budget in sA Architecture, (c) Distribution Budget in Fh Architecture. 50 ieee circuits AND sYstems mAGAziNe secoND QuArter 2019