The applet allows three of the commonest amplitude comparison DF algorithms to be compared under realistic conditions. Example patterns are included, but there is a facility for the user to input own antenna patterns for evaluation.
The number of ports is selectable over the range 4 to 24.
The model is based on a wideband detector-video receiver. Log-video amplification is assumed for amplitude ratio and quadratic fit DF algorithms, but a square-rooting video is modelled for the arc-tangent algorithm. These video compression amplifiers are modelled with a successive-limiting chain with an equivalent input RF dynamic range to the detector of −40dBm to 0dBm. The detector tangential signal sensitivity TSS can be varied by adjusting the noise level scrollbar. (Note TSS = −40dBm is equivalent to a noise level of −44dBm.) Video SNR performance is displayed with other key data on the main display. Compression amplifier error ripple performance (typically <1dB peak-to-peak for a successive-limiting log-video approximation) can be input as an adjustable parameter. The signal power level can be adjusted to ascertain the effect of low- and high-level threshold and limiting effects on DF performance.
The effect of port gain imbalances is assessed by adjusting the port gain error parameter. This chooses random peak-to-peak gain errors for the ports over the decibel range set. Values chosen for each port are indicated at the bottom of the display with the antenna pointing directions. The random gain errors are updated each time parameters are modified, but not when polarisations or display plots are being changed. The antenna element boresight gain is referred to 0dBm. Invariably the DF processor digitises the DF signals. Quantisation effects on DF performance are assessed by adjusting this entry. Should the antenna patterns squint, which does occur in practice, V and H polarisation adjust mean offsets can be input and used for calibration purposes. The polarisation radio buttons select between vertical and horizontally polarised antenna patterns.

User data is entered via the data console (Control+V) and activating the load button. A loadable example file is test file. This can either be edited once opened or used as a data formatting guide to the load file specification. There is a test field in the antenna drop-down menu for viewing user own data.
The main display shows three coloured error plots for the three DF algorithms with summary analyses. The vertical error axis automatically scales and adjusts to the data. The effects of noise, quantisation, DLVA ripple, port gain errors, signal amplitude, and noise level are readily apparent.
Antenna pointing directions are indicated relative to the azimuth axis by the red chevrons at the lower edge of the display.
The error mode button Fourier analyses the error plots and prints the mode results to the data console. Mouse movement in the azimuth - error space displays plotted data values with respect to the x-axis, azimuth position.

User Notes:
The example patterns are optimised for a six-port system, whilst the Gaussian pattern example adjusts its beamwidth optimally with the number of ports selected.
The display rescales as adjustments are made, but the error data summary displayed gives clearer evidence of the error magnitudes.