Antenna Array Configuration
This week, I spent some time finalizing the configuration — spacing requirements and number of elements — of our antenna array. Through some research on 2.4 GHz WiFi signals, I found that we will need a spacing of 6.25 cm between each antenna. This requirement was determined based on the wavelength of 2.4 GHz WiFi, which is 12.5cm, which must be halved to avoid spatial aliasing. This is done in order to sample the WiFi signal at a rate twice as fast as its fastest frequency — the Nyquist rate.
The number of array elements was determined by plotting the theoretical directional sensitivity for our beamformer, where I increased the number of array elements and until the plot had the directional sensitivity characteristics from our proposal (~3 degrees squared main lobe width). In doing this, I found that 32 array elements satisifed this constraint.
Signal Processing Pipeline Implementation
I began working on a testbed for our signal processing platform in MATLAB. So far, the testbed implements the frequency domain beamforming algorithm from https://academic.oup.com/mnras/article/439/3/3180/1113793. Before implementing on the FPGA, we will feed our data into this MATLAB testbed to verify that we can perform the beamforming to the required specifications. After that, we will compile the MATLAB code into Verilog for use on the FPGA (MATLAB has the ability to do this automatically).
Progress Since Last Week
I have addressed many of the uncertainties in our antenna array design from last week. We are on track with our schedule (from the proposal slide deck).
Plans for Next Week
Per our proposed schedule (see slides), this next week will involve the critical first steps in two of our project divisions: PCB design and part specification. On the PCB design side, most of the contribution will be from Txanton and Enock, though I will try to lend a hand where necessary. On the part specifcation side, I will finalize the commodity antennas that we will use, incorporating their characteristics to obtain some more concrete theoretical calculations.