This calculator solves for the Signal-to-Noise ratio (`SNR_"image"`) of a Synthetic Aperture Radar. Two versions of the Radar Equation are presented, along with auxiliary equations to help the calculation of different parameters. This page heavily draws on Sandia National Laboratories's Performance Limits for Synthetic Aperture Radar– second edition, which only considers the monostatic case (where the same antenna is used for TX and RX operations). The findings were also checked against Skolnik's Radar Handbook.
If there's a drop-down box next to the input text field when you click on a button, then you may choose any of those units from the list. The equations will adapt. If there is no drop-down box, then please enter the field in the units requested. If no units are mentioned, then the parameter is dimensionless.
The red buttons are two versions of the Radar Equation. They are equivalent in the context of SAR.
Briefly, SNR is the ratio between the signal and noise. Higher SNR means that the radar has a better picture of the target. Lower, worse picture.
`SNR_"radar" = P_r / N`, where:
The two versions of the Radar Equation in the calculator will look more complicated since they substitute in for `P_r`, and `N`. There are more details about the Radar Equations below.
In case the data you have doesn't precisely match either of these equations, the blue buttons are there to try and solve for certain parameters in terms of others. For example, the `A_e` button calculates the effective area of the calculator given the antenna's actual area and aperture efficiency.
The "`alpha` lookup" button provides estimated two-way atmospheric loss factors from a computer model. As such, the numbers are a little squishy - don't rely on them being perfectly accurate.
Typically, a maximum duty factor(`d`) needed by a radar is less than 50%, and usually less than 35% or so. Consequently, a reasonable duty factor limit of 35% might be imposed on power amplifiers that could otherwise be capable of more.
This calculator has two versions of the Radar Equation. This first Radar Equation is:
Where the parameters are:
The second version of the Radar Equation has many substitutions that assume a Synthetic Aperture Radar.
Where the new parameters are: