摘要:
A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restored range resolution, but the long pulse results in a large minimum range within which targets cannot be detected. A second can is provided at low elevation angles with a short transmitter pulse to fill in the short-range coverage. Beams at higher elevation angles transmit pulse widths which are shorter than beams at low elevation angles, so that the minimum range requirement is met without a second scan, which also reduces the time required for volumetric scan. The number of pulses which are integrated to produce a return increases off-axis, to restore system margin lost due to off-axis power gain reduction. The volumetric scan rate is increased by a dynamic scan regimen by which subsets of beams are pulsed with a high transmitter PRF but with a low effective beam PRF to reduce range ambiguity and preserve Doppler resolution without the usual increase of scan time. For best range resolution, Doppler processing is used, with range sidelobe pulse suppression applied separately to each Doppler frequency bin.
摘要:
A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected. A second scan is provided at low elevation angles with a short transmitter pulse to fill in the short-range coverage. Beams at higher elevation angles transmit pulse widths which are shorter than beams at low elevation angles, so that the minimum range requirement is met without a second scan, which also reduces the time required for volumetric scan. The number of pulses which are integrated to produce a return increases off-axis, to restore system margin lost due to off-axis power gain reduction. The volumetric scan rate is increased by a dynamic scan regimen by which subsets of beams are pulsed with a high transmitter PRF but with a low effective beam PRF to reduce range ambiguity and preserve Doppler resolution without the usual increase of scan time. For best range resolution, Doppler processing is used, with range sidelobe pulse suppression applied separately to each Doppler frequency bin.
摘要:
A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected. A second scan is provided at low elevation angles with a short transmitter pulse to fill in the short-range coverage. Beams at higher elevation angles transmit pulse widths which are shorter than beams at low elevation angles so that the minimum range requirement is met without a second scan, which also reduces the time required for volumetric scan. The number of pulses which are integrated to produce a return increases off-axis, to restore system margin lost due to off-axis power gain reduction. The volumetric scan rate is increased by a dynamic scan regimen by which subsets of beams are pulsed with a high transmitter PRF but with a low effective beam PRF to reduce range ambiguity and preserve Doppler resolution without the usual increase of scan time. For best range resolution, Doppler processing is used, with range sidelobe pulse suppression applied separately to each Doppler frequency bin.
摘要:
A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with .+-.45.degree. coverage in azimuth, from 0.degree. to 60.degree. in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected. A second scan is provided at low elevation angles with a short transmitter pulse to fill in the short-range coverage. Beams at higher elevation angles transmit pulse widths which are shorter than beams at low elevation angles, so that the minimum range requirement is met without a second scan, which also reduces the time required for volumetric scan. The number of pulses which are integrated to produce a return increases off-axis, to restore system margin lost due to off-axis power gain reduction. The volumetric scan rate is increased by a dynamic scan regimen by which subsets of beams are pulsed with a high transmitter PRF but with a low effective beam PRF to reduce range ambiguity and preserve Doppler resolution without the usual increase of scan time. For best range resolution, Doppler processing is used, with range sidelobe pulse suppression applied separately to each Doppler frequency bin.
摘要:
An emergency bulk liquid cargo handling system for marine vessels when storage tanks for those liquids have been ruptured and flooded with sea water wherein the liquid cargo handling system is adjustable to provide liquid cargo removal from the flooded tanks regardless of the level of the liquid cargo/water interface in the flooded tank.
摘要:
A device for determining the relative properties of stratified fluids, such as the interface between oil and water having plural fluid character recording stations with sensors on an elongated member. Means are provided to clear the recording stations to preclude contamination of the sensors by fluid from other strata.
摘要:
The drag-reducing bulbous bow of a seagoing vessel is provided with energy-absorbing structure including a controllably released fluid to reduce damage imparted by that vessel upon collision with another vessel or with an object.
摘要:
A connector for elements of floating pollution containment booms having a sliding tongue-in-groove joint with members formed to direct transverse forces, generated by tension in the joint, inwardly of the joint to affect stronger interconnection between the elements.
摘要:
A radar transmits dispersed pulses in which the subpulses are modulated by first and second mutually complementary code sequences, the autocorrelation functions of which are selected so that, in the sum of their autocorrelation functions, the main range lobes add, and the range sidelobes cancel. The received pulses with their Doppler sidebands are applied to a plurality of channels, each of which (except one) contains a mixer-oscillator combination that removes a specific Doppler phase shift along the range dimension at a different channel frequency. One channel has no mixer-oscillator because it is centered at a zero channel frequency. Within each channel, the received signals modulated by the first and second codes are matched-filtered by filters matched to the first and second codes, respectively, to produce first and second time-compressed pulses, each including (a) a main lobe representing the target range, and (b) undesirable range sidelobes. The first and second time compressed pulses are added together in each channel, to produce range pulses with suppressed range sidelobes. The channel signals, after pulse compression, delay, and addition, are each applied to one channel of a pulse-to-pulse Doppler filter bank. The outputs from the pulse-to-pulse Doppler filter bank are applied for further radar signal processing.
摘要:
A radar system transmits dispersed pulses, and receives echoes from targets. The echo signals are digitized and applied over a number of signal paths. In each signal path except one, the digitized signal is multiplied by one of a plurality of differential exponential signals, for converting the echo signal of different exponential signals, for converting the echo signal in each path to baseband, with the baseband frequency representing a particular Doppler which depends upon the exponential signal. In the one remaining signal path, no multiplier is used, and the echo signal is deemed to be at baseband. The signals in each path are applied through a cascade of a pulse compressor and a range sidelobe suppressor. Since Doppler filtering has not yet taken place, full compression and range sidelobe reduction is not achieved, because of extraneous pulse-to-pulse phase shifts. The signals in each signal path are applied to a filter element of a pulse-to-pulse Doppler filter bank, which removes the extraneous phase shifts, and thereby provides full suppression of the range sidelobes.