According to the Doppler equation, for any given velocity, the frequency shift will increase by increasing the:

According to the Doppler equation, for any given velocity, the frequency shift will increase by increasing the:

• A. Doppler angle
• B. Transmit frequency
• C. Pulse length
• D. Pulse repetition frequency

Answer: (B)

The Doppler frequency shift is proportional to the transmit frequency, the velocity component along the beam, and a cosine of the angle, expressed in the common form fD ≈ (2 f0 v cos θ) / c. So, for a fixed velocity, raising the transmit frequency f0 scales the shift up directly. In other words, higher transmitted frequency means the same moving scatterer produces a larger frequency shift. The angle matters too because of the cos θ term, but increasing the angle tends to reduce cos θ (since cos θ decreases as θ increases), which would decrease the shift rather than increase it. Pulse length and pulse repetition frequency don’t change the actual magnitude of the Doppler shift; pulse length affects spectral broadening and resolution, while PRF affects the sampling rate and potential aliasing but not the shift value itself.

The Doppler frequency shift is proportional to the transmit frequency, the velocity component along the beam, and a cosine of the angle, expressed in the common form fD ≈ (2 f0 v cos θ) / c. So, for a fixed velocity, raising the transmit frequency f0 scales the shift up directly. In other words, higher transmitted frequency means the same moving scatterer produces a larger frequency shift.

The angle matters too because of the cos θ term, but increasing the angle tends to reduce cos θ (since cos θ decreases as θ increases), which would decrease the shift rather than increase it. Pulse length and pulse repetition frequency don’t change the actual magnitude of the Doppler shift; pulse length affects spectral broadening and resolution, while PRF affects the sampling rate and potential aliasing but not the shift value itself.