MOSFET Based Absorber for Reflected Signal in 5G Massive MIMO Base Station - A Circuit Perspective

Abstract

A lossy transmission has negative effect on the overall performance and efficiency of base station subsystems. One key feature of 5G technologies is improved efficiency compared to 4G technology. The 5G massive-MIMO base station structure may suffer from these losses, which affect the inclusive performance and efficiency of the base substation. Furthermore, in the 5G technology, loss is anticipated due to the reflection of signals from the receiver (Rx) branch connected to the circulators in the 5G MIMO base station. This reflection loss is due to the mismatched load impedance of the Rx branch with the source impedance of transmitter (Tx) branch. The main objective of this research is to use MOSFET to absorb the reflected signal resulting from impedance mismatching between the Tx and Rx. After that, two comparisons have been made between source current and drain current of the MOSFET mathematically, whenever there is a reflection from the Rx branch of the base station. In addition, the proposed circuit model has been presented by connecting the Tx branch, antenna, Rx branch, and the MOSFET to each of the ports of a four-port circulator. A reflected RF power of 13 dBm at 1.4 V peak is rectified to its equivalent DC value 1.004 V. However, these values of current and voltage are pulsating and filtered at the output end of the rectifier with the use of an LC Filter.

Parametric Analysis of SiO₂MOSFET Based Absorber for 5G Massive MIMO Base Station

“…For the MOSFET device to function effectively, MOSFET input terminal current and voltages must be continuous instead of pulsating. absorber of reflected RF signal [5].…”

“…The modulated RF signal from the TX branch of the base station flows through port-1 of the circulator into the circulator. This signal is sent to the reception antenna connected to port-2 of the neighbouring base station's circulator via port-2 [5].…”

“…The reflected signal from port-3 of the adjacent base station exits the circulator via port-4, which has a rectifier and Nchannel MOSFET connected. More details have been discussed in the author's previous work [5,6].…”

“…From the values of simulation plots, IS, ID, VDS at source, and VDS at drain have been observed to be 0.4 mA, 0.4 mA, 0 V, and 1.6 V, respectively. Values from simulation, putting the values of voltages and current into the relationship IS ≤ ID and VDS = 0 at the source terminal, at 19 dBm reflected power from port-4 of the circulator, MOSFET's condition for absorption was satisfied for 19 dBm reflection condition from port-4 of the circulator [9]. Even though the value of reflected power is large, it has been used for testing and experimental purposes, which may not be the case in real-life applications.…”

“…When frequencies are too high, it becomes difficult for discrete capacitors and inductors to be practical. A combination of Schottky diode and distributed circuit will be employed for the rectification and filtration process during the physical implementation of the proposed model [5,9].…”