4.2.2 Chirp Configuration for TX Beamforming Radar

For the TX beamforming application, the chirp configuration in Table 3 is used.

With this chirp configuration the TXBF performance shown in Table 1 is achieved. The primary goal was to achieve a maximum distance of about 350 m and maximum velocity around +/-130 km/h. See Programming Chirp Parameters in TI Radar Devices for more details.

The amount of phase value to program to each TX channel is computed as a function of array factor and target angle. Assuming N TX channels, with TX1 as a reference, the distance between every other antenna and TX1 is the known distance when the antenna array is designed during board development. As shown in Figure 9 for TI cascade EVM, the distance between any two adjacent TX channels is two times the wavelength.

Given the notation in Figure 9, the phase value for each TX channel is calculated as:

The ideal phase value is further quantified by the allowed phase step size of 5.625 degree to calculate the integer value to be programed to the registers (TX calibration phase value will also be added as shown in the next section).

As an example, for TI cascade EVM, 9 azimuth TX antennas can be used for beam steering, with [d2 = 2λ,d3 = 4λ,…,d9 = 16λ]. If the desired steering angle is 30 degrees, then the phase vector is as shown in degrees in Equation 3.

The TX beamforming application supports both chirp based beam steering and frame based beam steering. Advanced frame configuration is used for either case.