4.1 Antenna Configuration

Figure 5 shows the antenna array on the Cascade RF board with one master device and three slave devices. Together these devises create a total of 12 TX channels and 16 RX channels. Among the 12 TX channels, the three TXs (TX1/2/3) from the master device are placed in the vertical direction for elevation antenna estimation. The remaining 9 TXs (TX4 through TX12) and all 16 RX channels are placed in the horizontal plane for azimuth angle estimation. The relative distances between TXs and between RXs are shown in Figure 6. The three elevation antennas are placed to form a minimum redundancy array to improve elevation angle resolution. Every two azimuth TXs are spaced 2 wavelengths apart. RX array A and RX array C are placed 16-wavelengths apart. RX array C and RX array B are placed four-wavelengths apart. The virtual array in MIMO mode is shown in Figure 7, with 86 virtual antennas in azimuth direction. The overlapped antenna in azimuth is not shown in the figure. The elevation angle resolution is equivalent to the resolution achieved with 7 antennas.

The Cascade RF board can also be used in two chip cascade mode with 6 TX and 8 RX channels highlighted in Figure 6. Figure 8 shows the virtual MIMO array in 2-device cascade mode using TX ID of [1 2 3 10 11 12] and RX ID of [ 4 3 2 1 16 15 14 13], with 23 azimuth antennas and same elevation configuration with 4-device cascade.