Abstract: This invention relates to a method of improving performance of a SODAR system adapted to locate discontinuities in the atmosphere by transmitting pulse compression signals such as a plurality of acoustic chirps, the method comprising: transmitting one or more acoustic chirps; receiving one or more acoustic echoes of the transmitted chirps; processing the acoustic echoes to provide an indication of the discontinuities in the atmosphere, thereby providing a wind shear profile; processing the wind shear profile to correct systematic Doppler errors associated with the acoustic echoes by: subtracting a first measured wind speed from the wind shear profile; and adding a second measured wind speed to the wind shear profile.

Abstract: This invention relates to a method of reducing error in a SODAR system adapted to locate discontinuities in the atmosphere over a range extending away from an acoustic transmitter and receiver, the method comprising the steps of: measuring wind to determine either a substantially upwind direction or a substantially downwind direction relative to the transmitter; transmitting one or more forward or reverse acoustic chirps in the substantially upwind or downwind direction; receiving one or more acoustic echoes of the transmitted chirps; and processing the acoustic echoes to provide an indication of the discontinuities in the atmosphere over the range, thereby providing a wind shear profile.

Abstract: This invention relates to a method of improving performance of a SODAR system adapted to locate discontinuities in the atmosphere by transmitting pulse compression signals such as a plurality of acoustic chirps, the method comprising: transmitting one or more acoustic chirps; receiving one or more acoustic echoes of the transmitted chirps; processing the acoustic echoes to provide an indication of the discontinuities in the atmosphere, thereby providing a wind shear profile; processing the wind shear profile to correct systematic Doppler errors associated with the acoustic echoes by: subtracting a first measured wind speed from the wind shear profile; and adding a second measured wind speed to the wind shear profile.

Abstract: A method is disclosed for detecting atmospheric turbulence including aircraft induced wake turbulence and/or wind shear within an aperture associated with an aircraft approach or departure corridor around an airport. The method comprises transmitting into the aperture acoustic signals having a waveform suitable for pulse compression and receiving backscattered acoustic echoes of the acoustic signals from the atmospheric turbulence and/or wind shear. The method further includes processing the acoustic echoes in a matched filter receiver to provide a measure of the atmospheric turbulence and discriminating the aircraft induced demise time, being a time taken for the aircraft induced wake turbulence and/or wind shear to fall below a set threshold at least in the aperture. A system for detecting atmospheric turbulence including aircraft induced wake turbulence and/or wind shear associated with an aircraft approach or departure corridor around an airport is also disclosed.

Abstract: A method is disclosed for improving performance of a Sodar system adapted to locate discontinuities in the atmosphere by transmitting pulse compression signals such as plural acoustic chirps. The method comprises transmitting the acoustic chirps, receiving acoustic echoes of the chirps, and processing the acoustic echoes to provide an indication of the discontinuities, wherein the processing includes correcting range or resolution error associated with the acoustic echoes.

Abstract: A method is disclosed for detecting atmospheric turbulence including aircraft induced wake turbulence and/or wind shear within an aperture associated with an aircraft approach or departure corridor around an airport. The method comprises transmitting into the aperture acoustic signals having a waveform suitable for pulse compression and receiving backscattered acoustic echoes of the acoustic signals from the atmospheric turbulence and/or wind shear. The method further includes processing the acoustic echoes in a matched filter receiver to provide a measure of the atmospheric turbulence and discriminating the aircraft induced demise time, being a time taken for the aircraft induced wake turbulence and/or wind shear to fall below a set threshold at least in the aperture. A system for detecting atmospheric turbulence including aircraft induced wake turbulence and/or wind shear associated with an aircraft approach or departure corridor around an airport is also disclosed.

Abstract: A method is disclosed for improving performance of a Sodar system adapted to locate discontinuities in the atmosphere by transmitting pulse compression signals such as plural acoustic chirps. The method comprises transmitting the acoustic chirps, receiving acoustic echoes of the chirps, and processing the acoustic echoes to provide an indication of the discontinuities, wherein the processing includes correcting range or resolution error associated with the acoustic echoes.

Abstract: A monostatic sodar system (10) for atmospheric sounding includes a processor and display unit (12) that generates a set of acoustic chirps for transmission by transmitter 20. Discontinuities (22, 24 and 26) result in echoes (28, 30 and 32) being returned to a receiver (38) of system (10). Receiver (38) outputs extracted echo signals on line to the processor (12) for analysis. Detector (36) implements a Fourier domain matched-filter to extract echo signals from noise. By using a set of multiple chirps of increasing length with increasing intervals between them, substantially any feasible range can be accommodated using send-then-listen techniques with the benefit of high s/n performance.

Abstract: A monstatic sodar system using long chirps and send-while-listening techniques employs transmitter-receiver pairs (Tw, Rw; Tv, Rv; Te, Re) that have coincident main lobes (Twm, Rwm; Tvm, Rvm; Tem, Rem). The system uses digital time domain matched filters and frequency modulated or digitally modulated (eg, BPSK) chirps. Digital frequency domain matched filtering may also be used. The matched filters generate sample streams indicative of the phase and amplitude of echo signals returned from the atmosphere after the transmission of a chirp into the atmosphere.

Abstract: A bi-static sodar system and method are used to measure and monitor the wake vortices of aircraft in the flight path of an airport runway. A loudspeaker (16) is arranged on one side of the flight path (12) and transmits a series of acoustic pulses to illuminate portion of the flight path. Multiple microphones (18, 20 and 22) are arranged on the opposite side of the flight path (12) so as to receive direct signals from the loudspeaker (16) and forward-scattered echo signals from an echo source (26) within the illuminated portion of the flight path. The microphones (18, 20 and 22) are arranged at different distances from the loudspeaker so that the time intervals between the receipt of the direct and echo signals from each pulse will vary because of the different locations of the microphones. This variation is used to assist in identifying the location and other characteristics of the echo signals and in generating an output indicative of a wake vortex (28).

Abstract: A monstatic sodar system using long chirps and send-while-listening techniques employs transmitter-receiver pairs (Tw, Rw; Tv, Rv; Te, Re) that have coincident main lobes (Twm, Rwm; Tvm, Rvm; Tem, Rem). The system uses digital time domain matched filters and frequency modulated or digitally modulated (eg, BPSK) chirps. Digital frequency domain matched filtering may also be used. The matched filters generate sample streams indicative of the phase and amplitude of echo signals returned from the atmosphere after the transmission of a chirp into the atmosphere.

Abstract: Means for masquerading IP addresses for non-IP devices are disclosed, enabling non-IP devices or sub-networks having incompatible address spaces to be connected to an IP network and appear as addressable network objects. In one embodiment, the means may be a remote system controller (RSC) that has a block of IP addresses assigned to it for use with connected sub-networks or devices. Normally each assigned address will be associated with a management information base (MIB) containing data about the associated device, and each MIB will be associated with a protocol converter and I/O port connectable to the respective device or sub-network.

Abstract: A bi-static sodar system and method are used to measure and monitor the wake vortices of aircraft in the flight path of an airport runway. A loudspeaker (16) is arranged on one side of the flight path (12) and transmits a series of acoustic pulses to illuminate portion of the flight path. Multiple microphones (18, 20 and 22) are arranged on the opposite side of the flight path (12) so as to receive direct signals from the loudspeaker (16) and forward-scattered echo signals from an echo source (26) within the illuminated portion of the flight path. The microphones (18, 20 and 22) are arranged at different distances from the loudspeaker so that the time intervals between the receipt of the direct and echo signals from each pulse will vary because of the different locations of the microphones. This variation is used to assist in identifying the location and other characteristics of the echo signals and in generating an output indicative of a wake vortex (28).

Abstract: A monostatic sodar system (10) for atmospheric sounding includes a processor and display unit (12) that generates a set of acoustic chirps for transmission by transmitter 20. Discontinuities (22, 24 and 26) result in echoes (28, 30 and 32) being returned to a receiver (38) of system (10). Receiver (38) outputs extracted echo signals on line to the processor (12) for analysis. Detector (36) implements a Fourier domain matched-filter to extract echo signals from noise. By using a set of multiple chirps of increasing length with increasing intervals between them, substantially any feasible range can be accommodated using send-then-listen techniques with the benefit of high s/n performance.

Abstract: A method of determining the latency of a route in a packet-switched network, a packet switch for use in such a method and network and a packet-switched network are disclosed. Preferably, each switch maintains a routing table that records the latency of the routes accessible by that switch. Each switch also preferably has a GPS-based universal time clock which it employs to time the transmission and arrival of identifiable timing packets, these times being used to compute route latency and to up-date the routing tables. In one example (FIG. 1) a packet-switched network has a plurality of switches (S1-S6) interconnected by links or trunks (T1-T7). A local GPS-base clock (GPS CLK) is connected to each switch (S1-S6) to enable the accurate timing of transmission and reception of identifiable timing packets in accordance with a system-wide universal timing standard.

Abstract: Sodar systems and methods for acoustically sounding air are disclosed in which chirps longer than 300 ms—and preferably with durations of tens of seconds—are used along with matched filter and/or Fourier processing methods to derive phase signals indicative of air characteristics in range. A listen-while-transmit strategy is preferred, the direct signal being removed by subtracting the phase signals from two or more receivers located near the transmitter so as to be in the same noise environment. The resultant differential signals can be related to cross-range wind with range distance. In one example, apparatus (100) is employed comprising a reflector dish (102) over which one central loudspeaker (110) and four microphones (112, 114, 130 and 132) are mounted, the microphones preferably being located on cardinal compass points and having their axes (124, 126) slightly angled with respect to the vertical transmission axis (122).

Abstract: Two SODAR systems (12a and 12r) for detecting and characterizing vortices (16) shed from landing or departing aircraft (14) as at an airport (10) are positioned so that one, the active system (12a) is located beneath the likely vortices (16) and the other, the reference system (12r) is located away from the vortices but in the same ambient environment. Thus, where a wind duct or thermal inversion (18) is present, both SODAR systems will detect echoes (22 and 28) generated thereby, whereas only the active system (12a) will detect echoes (24) from wake vortices (16). By differencing the outputs of the reference and active systems, better vortex identification and discrimination is achieved. Only one SODAR system need be used where sufficiently normal conditions prevail between aircraft activity, since readings taken in the absence of aircraft can be used as reference data for subtraction from ‘active’ data recorded during the presence of aircraft.

Abstract: A method and system for acoustically sounding the lower atmosphere involves the transmitting of an acoustic chirp and the processing of returned echoes and interference using wavelet and matched filter techniques. A single transmitter and four receivers may be used, with receivers located equidistant from the transmitter on the cardinal points of the compass. N, S, E, & W inputs are digitized and input to a wavelet filter (50) together with the transmitter chip signal (R or D) for the attenuation of the direct signal and ambient noise signals. The interference-attenuated signals are then processed in a matched filter (52) to extract phase and amplitude outputs (54 and 56), the phase output being unwrapped (70). The N and S phase signals and the E and W phase signals are then separately differenced (74 and 80) and the results used to compute (86 and 92) wind speed and bearing.

Abstract: Sodar systems and methods for acoustically sounding air are disclosed in which chirps longer than 300 ms—and preferably with durations of tens of seconds—are used along with matched filter and/or Fourier processing methods to derive phase signals indicative of air characteristics in range. A listen-while-transmit strategy is preferred, the direct signal being removed by subtracting the phase signals from two or more receivers located near the transmitter so as to be in the same noise environment. The resultant differential signals can be related to cross-range wind with range distance. In one example, apparatus (100) is employed comprising a reflector dish (102) over which one central loudspeaker (110) and four microphones (112, 114, 130 and 132) are mounted, the microphones preferably being located on cardinal compass points and having their axes (124, 126) slightly angled with respect to the vertical transmission axis (122).

Abstract: A method of determining the latency of a route in a packet-switched network, a packet switch for use in such a method and network and a packet-switched network are disclosed. Preferably, each switch maintains a routing table that records the latency of the routes accessible by that switch. Each switch also preferably has a GPS-based universal time clock which it employs to time the transmission and arrival of identifiable timing packets, these times being used to compute route latency and to up-date the routing tables. In one example (FIG. 1) a packet-switched network has a plurality of switches (S1-S6) interconnected by links or trunks (T1-T7). A local GPS-base clock (GPS CLK) is connected to each switch (S1-S6) to enable the accurate timing of transmission and reception of identifiable timing packets in accordance with a system-wide universal timing standard.