IWR1443BOOST: Resolution and accuracy of elevation angle for IWR1443BOOST

Hello,

TI's MIMO Radar App note explains the basic principles of angle estimation. As described in Appendix-A of this app note, the angular resolution for an antenna array with N total receive elements with an inter-antenna spacing of d=lambda/2 is given by the equation 

θres = 2/N (Please note that this is defined for θ = 0 i.e. bore-sight view.

Here N is the total number of receiver elements. For MIMO configuration, N is defined as the product of the number of physical TX and RX antennas. For example, for a system with 2Tx and 4RX, N = 8, i.e. it will have 8 receiver elements when used in MIMO configuration.

Resolution

The elevation estimation on IWR1443BOOST EVM is performed by using any two adjacent TX antennas (in TDM MIMO configuration) and any one of the 4 RX channels. This means that the number of virtual receiver elements, N, for elevation is 2x1 = 2.

Thus, Elevation angular resolution = 2/N i.e. 1 Radian (57.29 degrees)

Accuracy

Accuracy (range/velocity/angle) is dependent upon SNR and the corresponding resolution. The actual achieved accuracy would also depend upon the FFT size.

The formula for accuracy in general is Accuracy = Resolution / sqrt (2 x SNR). Angular accuracy is dependent upon the algorithm also but for an FFT based algorithm (which is used in OOB demos), this formula can be used.

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Angular angular resolution = 1 radian

Let's consider detection SNR = 12dB

So the theoretical elevation angle accuracy = 1 / sqrt (2x12) =0.204 radians i.e. 11.68 degrees. The OOB demo uses 64 FFT bins for angle estimation which can achieve 180/64 = 2.81 degrees accuracy but in this case the limiting factor (at this detection SNR) is the theoretical resolution .

Thanks

-Nitin