The applet demonstrates the design trade-offs and performance of a two DLVA + RF amplifier, wide dynamic range log-video receiver.
The two lower plots allow modification of the RF amplifier gain and noise figure by aligning the mouse on the subband centre black spots and clicking/dragging these vertically to new required values. Signal frequency is adjusted by the Frequency scrollbar and moves the green indicating marker in sympathy along the frequency axis.
The number of subbands is fixed at 20, but nominal (lower band-edge) gain, nominal noise figure, video bandwidth, and video TSS are adjustable by the relevant scrollbars.
The RF band cover required is entered in the Input Frequency range text boxes at the bottom of the applet.
The top two plots depict the DLVA outputs and errors from ideal over relevant ranges of input power. The errors are referenced to the input coupler loss (for DLVA D1) and the RFA nominal gain+output coupler loss (for DLVA D2).
The RFA Output scrollbar limits the amplifier maximum output power to the figure set.
Spot signal input power is adjusted with a scrollbar moving the blue marker along the Input Power axis.
The SNR readouts below the marker show the ideal detector SNRO and the Apparent SNRO; as measured at the output of the working DLVA.
The top drop-down menu suggests three initial RFA parameter examples; all may be modified interactively. The bottom drop-down menu allows choice of a standard 45-dB DLVA component or a 50-dB extended range device. The DLVA characteristics are based on 1-dB peak-peak error limiting summation video compression design showing the corresponding ripples in the magnified error plots.
Video noise is modeled and is more apparent at the lower levels of DLVA drive, and is resampled on mouse-clicking the display space.
Data corresponding to the mouse x-axis position and plot region are displayed at the top.
This applet applies the RF subband technique described in Chapter 7, that restricts the video bandwidth to half the subband width.

User Notes:
The high gain, log-error curve is corrected only by the nominal gain figure, gain offsets from this are assumed uncalibrated.
Scrolling the (green) signal frequency marker across any RF gain ripples causes a corresponding offset error in the high gain DLVA D2. The resulting DLVA data offset would normally need calibration if continuous amplitude measurement data is required.
Normally, the RF nominal gain is adjusted to allow some overlap of DVLA responses to cope with RF gain variations. RF power (saturated) output variations can also affect the overlap.
The Apparent SNRO is calculated dynamically at the DLVA output; it differs from the ideal SNRO, as it uses the DLVA instantaneous slope that is affected by the modeled ripples.