Side lobe artifacts occur where side lobes reflect sound from a strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam. These radial beams are called side lobe beams.
What is the side lobe effect?
The other lobes are called “side lobes”, and usually represent unwanted radiation in undesired directions. In receiving antennas, side lobes may pick up interfering signals, and increase the noise level in the receiver. The power density in the side lobes is generally much less than that in the main beam.
What are the 3 different types of false echoes?
Many types of false radar echoes are observed on a ship-mounted radar scope, including side lobe echoes, interference echoes, second trace echoes, and others.
What causes side lobe artifact?
Secondary lobe artifacts arise from reflections of unwanted ultrasound energy directed off-axis from the main beam and include side lobes and grating lobes. Most of the sound energy is transmitted within the center of the primary beam.
What is false echo?
Indirect or false echoes are caused by reflection of the main lobe of the radar beam off ship’s structures such as stacks and kingposts. When such reflection does occur, the echo will return from a legitimate radar contact to the antenna by the same indirect path.
What Causes Second trace echoes?
Second-trace echoes (multiple-trace echoes) are echoes received from a contact at an actual range greater than the radar range setting. Second-trace echoes are unusual except under abnormal atmospheric conditions, or conditions under which super-refraction is present.
What are side lobes in ultrasound?
Transducer side lobes consist of multiple low-intensity sound beams located outside of the main ultrasound beam. Although the echoes generated by side lobes originate outside of the main beam, they appear as specular or diffuse artifactual echoes within the beam.
What is side lobe suppression?
Sidelobe suppression has been implemented in many radar systems, including ATCRBS, to solve a common problem. This problem occurs due to signal leakage in the directional antenna. When interrogation signals are transmitted with a directional antenna, the signal often leaks through the sides of the antenna.
What are second trace echoes?
Second-trace echoes (multiple-trace echoes) are echoes received from a contact at an actual range greater than the radar range setting. If an echo from a distant target is received after the following pulse has been transmitted, the echo will appear on the radarscope at the correct bearing but not at the true range.
What is a multiple echoes?
The successive reflection of a sound wave from a number of obstacles, causes us to hear echo of the sound transmitted one after other. When a sound is repeatedly reflected between two parallel distant buildings or cliffs, multiple echos are produced.
What is a lobe in ultrasound?
Side lobes and grating lobes are both unwanted parts of the ultrasound beam emitted off axis that produce image artifacts due to error in positioning the returning echo.
What is a side lobe artifact?
Side lobe artifacts occur where side lobes reflect sound from strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam.
What is a side lobe ultrasound transducer?
Ultrasound transducer crystals expand and contract to produce primary ultrasound beams in the direction of the expansion and contraction. Secondary beams also occur because the crystals also expand and contract radially. These radial beams are called side lobe beams. Side lobe beams are low-intensity beams that surround the central beam.
What are the characteristics of indirect echo?
Characteristics by which indirect echoes may be recognized are summarized as follows: Indirect echoes will often occur in shadow sectors. They are received on substantially constant bearings, although the true bearing of the radar contact may change appreciably. They appear at the same ranges as the corresponding direct echoes.
What is a second trace Echo?
A second or third or more echoes may be observed on the radarscope at double, triple, or other multiples of the actual range of the radar contact . Second-trace echoes (multiple-trace echoes) are echoes received from a contact at an actual range greater than the radar range setting.
