Monostatic vs bistatic radar geometries: which is true?

• A. Monostatic cannot detect moving targets; bistatic can.
• B. Monostatic uses two separate receivers; bistatic uses a single receiver.
• C. Monostatic has transmitter and receiver co-located; bistatic has separated transmitter and receiver, which changes path lengths and Doppler and can affect target detectability.
• D. Monostatic always has higher resolution than bistatic.

Answer: (C)

In radar geometry, the key difference is where the transmitter and receiver are located relative to each other. In a monostatic setup, transmitter and receiver are co-located (often the same antenna), so the transmitted wave travels to the target and returns to the same site. In a bistatic setup, the transmitter and receiver are separated, sometimes on different platforms, so the signal goes from transmitter to target and then to a distant receiver.

That separation changes the path lengths and the Doppler effect. The total distance the signal travels is the sum of the transmitter-to-target and target-to-receiver distances, which affects range measurements and timing. More importantly, Doppler depends on how the target’s velocity projects onto both lines of sight: the transmitter–target direction and the target–receiver direction. In bistatic geometry these projections are different from the monostatic case, so the observed Doppler shift can be different, and the target’s detectability can be impacted by the geometry, SNR, and potential ambiguities in range and angle.

So the statement that accurately describes the true difference is that monostatic radar has transmitter and receiver co-located, while bistatic radar has them separated, which changes path lengths and Doppler and can affect how easily a target is detected.