The object of this applet is to demonstrate the operation and performance of the basic compressive receiver under various design parameter conditions.
The upper left display shows the input RF pulse and relative timing together with input noise, while the lower left display shows the spectrum of the chirped pulse and the filter response of the Dispersive Delay Line (DDL).
The center left display shows the frequency modulated LO chirp cycle (frequency versus time). In the default condition, this is set to double the DDL bandwidth. The blue star indicator follows the pulse frequency and timing offsets.
The right-hand display shows the resulting compressed output pulse envelope plus noise (blue) and the noise background (red) with no signal present.
The lower left display plots the DDL filter response (red), the chirped signal spectrum (blue), and the DDL filter spectrum (green). The upper group of scrollbars control the pulse width, rise time, and pulse frequency and timing offset relative to the chirp cycle and band centers; while the lower scrollbars control the DDL and RF band parameters.
The RF/DDL BW ratio scrollbar controls the RF bandwidth that is scanned by the chirp LO. The wider the RF bandwidth, the lower the probability that the pulse chirp falls within the DDL bandwidth as noted by the probability of intercept (POI) data display.
The main displays are normalized to improve the presentation, but at large negative SNR the high noise level can obscure some detail.
The resulting performance data are indicated and updated below the main display.
Above the compressed pulse display, the expected SNRO is calculated, while the indicated value is obtained from the DDL processed and displayed data. Actual intercept and sensitivity interaction is examined using the pulse width, pulse offset and RF Offset scrollbars.
The input SNR is variable via the SNRI scrollbar to demonstrate the effects of receiver noise levels.
CP Scale radio buttons expand the compressed pulse timebase in defined increments.
Data readouts correspond to the mouse x-axis position, although more accurate data is saved to the data console.

User Notes:
Compressive receivers indicate signal frequency as position in time relative to the chirp scan. Frequency/time response can be observed by adjusting the signal frequency RF Offset scrollbar. The compressed pulse amplitude is further reduced as the RF is tuned outside the RF band.
Accurate timing for video peak detection and frequency estimation requires a broad video analysis bandwidth.
Input pulse dwells longer than the LO sweep time have 100% probability of intercept and achieve the maximum compression gain.
If the pulse length is equal to or less than the dispersion, the compression gain is both frequency and time offset dependent.
Start with a high SNR and then lower it to examine the performance at low SNR's.