Which statement best describes the angular resolution of a phased-array radar and the factors that limit it?

Which statement best describes the angular resolution of a phased-array radar and the factors that limit it?

• A. Angular resolution is approximately λ / D; limits include array aperture, element spacing, mutual coupling, calibration errors, and scan strategy.
• B. Angular resolution is approximately D / λ; limits include transmitter power and antenna gain.
• C. Angular resolution is approximately λ * D; limits include weather conditions.
• D. Angular resolution is approximately √(λ/D); limits include processing speed.

Answer: (A)

Angular resolution in phased-array radar is about how finely you can separate two objects in angle, i.e., the sharpness of the beam. The guiding relation is that the main-beam width scales with wavelength divided by the aperture size, so the angular resolution is on the order of λ / D. This captures the idea that a larger aperture (D) or a shorter wavelength (smaller λ) improves your ability to distinguish close directions. The limits come from several practical factors that shape what you can actually realize. The array’s aperture size sets the potential resolution—the larger the aperture, the narrower the main lobe. How you populate and space the elements matters too; element spacing influences the risk of grating lobes and how evenly the aperture is illuminated. Mutual coupling between elements can distort the overall pattern, often widening the beam or introducing distortions that hurt angular discrimination. Calibration errors in phase and amplitude across the array degrade beam quality, effectively broadening the main lobe. Finally, the scan strategy—the way you steer the beam—can change the beam shape and resolution across the field, especially away from boresight. The other statements mix up the relationship or bring in factors that don’t set the fundamental angular discrimination. The key idea here is the λ / D scaling with the stated limiting factors, not D/λ, λ·D, or √(λ/D), and not primarily weather or transmitter power for angular resolution.

Angular resolution in phased-array radar is about how finely you can separate two objects in angle, i.e., the sharpness of the beam. The guiding relation is that the main-beam width scales with wavelength divided by the aperture size, so the angular resolution is on the order of λ / D. This captures the idea that a larger aperture (D) or a shorter wavelength (smaller λ) improves your ability to distinguish close directions.

The limits come from several practical factors that shape what you can actually realize. The array’s aperture size sets the potential resolution—the larger the aperture, the narrower the main lobe. How you populate and space the elements matters too; element spacing influences the risk of grating lobes and how evenly the aperture is illuminated. Mutual coupling between elements can distort the overall pattern, often widening the beam or introducing distortions that hurt angular discrimination. Calibration errors in phase and amplitude across the array degrade beam quality, effectively broadening the main lobe. Finally, the scan strategy—the way you steer the beam—can change the beam shape and resolution across the field, especially away from boresight.

The other statements mix up the relationship or bring in factors that don’t set the fundamental angular discrimination. The key idea here is the λ / D scaling with the stated limiting factors, not D/λ, λ·D, or √(λ/D), and not primarily weather or transmitter power for angular resolution.