JP2000514924A - Differential ground station repeater - Google Patents

Abstract

(57) [Abstract] Using a plurality of transmitters, relay information from a single ground station located to receive satellite information to the aircraft, and the signal of any transmitter from which the aircraft is receiving signals A differential ground station repeater that transmits satellite and other information to a plurality of correction information transmitters that use a single frequency but transmit in differently described sub-time slots so that they can also be used.

Description

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present differential ground station repeater invention position using signals transmitted from a plurality of satellites, attitude, speed and the operation of the aircraft, such as the rate of change of these parameters A ground station apparatus for use with a differential global positioning system (DGPS) that determines various parameters and provides correction information for satellite-specific pseudorange errors. 2. Description of the Prior Art GPS systems are well known in the art. Examples of such prior art systems are U.S. Pat. No. 5,361,212 of the assignee and U.S. Pat. No. 4,948,655, assigned to LMT Radioprefessionnelle of Boulogne Billancourt, France. For simplicity, FIG. 1 of the present specification shows a simple prior art system. Here, an aircraft 10 is shown receiving signals from four distant satellites (FS1, S2, FS3, and FS4) via paths indicated by arrows 12, 14, 16, and 18, respectively. The GPS receiver mounted on the aircraft 10 can determine the desired aircraft parameters (such as position, attitude, speed, and rate-of-change parameters) useful for the navigation of the aircraft based on this signal. However, due to various factors, such as distortion in the troposphere and ionosphere, signals from satellites may include errors referred to herein as "satellite-specific pseudorange errors", which make aircraft parameter determinations impractical. Be accurate. Accordingly, more advanced prior art has utilized a DGPS receiver, shown as box 20 with antenna 22 in FIG. The receiver is in a known fixed position with very high accuracy. A DGPS receiver with a receiving antenna 22 for receiving information from the satellites in view, in this example the four satellites FS1, FS2, FS3 and FS4 via paths indicated by arrows 24, 26, 28 and 30. 20 is shown. Although a single antenna is shown in FIG. 1, multiple antennas, preferably three, can be used to minimize multipath distortion due to nearby objects (buildings, trees, etc.). The DGPS receiver 20 calculates the distance based on the signal transmitted from the satellite and sends this information to the microprocessor 34 via the connection indicated by arrow 32, which determines the exact position of the DGPS receiver. Then, pseudo-range errors unique to the satellite are determined, and information signals of these errors are generated to a transmitter 38 having a transmission antenna 40 via a line indicated by an arrow 36. The antenna 40 transmits to the aircraft 10 as shown by arrow 42 and to a locally fixed antenna 44 connected to a receiver 46. The receiver 46 returns a signal indicating the content transmitted to the aircraft 10 to the ground station 20 via a line indicated by an arrow 48. This return signal is called a data link wraparound and is transmitted to the aircraft 10 as a check to confirm that the ground station including 22, 20, 32, 34, 36, 38, and 40 maintains accuracy. The purpose is to notify the accurate signal obtained to the ground station. Thus, aircraft 10 can use the currently known error information to modify its own calculation of aircraft parameters and verify that the accuracy of the calculation is accurate. Systems such as that shown in FIG. 1 are used to guide and land aircraft at various airports nearby or around the world, and after landing, to guide the aircraft in gliding mode to the terminal via a ground path. This signal is valid for aircraft within a 100-mile radius circle centered on antenna 22. The ground station system of FIG. 1 has problems for the following reasons. 1) Not all parts of the aircraft landing site are visible from the antenna 40 due to obstacles such as buildings and the natural environment. 2) When several airports are close to each other, the signal transmitted to the aircraft cannot cover the full range. 3) Frequency congestion occurs because the current landing system (ILS) uses many frequencies in its band. To solve the last problem, the FAA specified the requirements for transmitting DGPS messages using the RTCA time slot assignment shown in FIG. 2 in Appendix F of Document DO-217 on May 10, 1994. FIG. 2 shows three transmission periods, denoted T1, T2 and T3, respectively, which are divided into a plurality of, for example, eight sub-time slots identified by Arabic numerals 1 to 8 in FIG. . FIG. 2 shows three different transmitters transmitting information to an aircraft from a location that can be duplicated so that the aircraft can receive multiple transmissions at the same time and that would cause confusion if their frequencies were the same. It is assumed that TX1, TX2, and TX3 are present. Thus, when using a single frequency, the FAA indicates that the first transmitter TX1 transmits its information only during sub-time slot 1 of each transmission period, and that the transmitter TX2 transmits sub-time slot 2 of each transmission period. It is proposed that transmitter TX3 transmit its information only during sub-time slot 3 of each transmission period. If there are eight sub-periods, use five more transmitters in the system and broadcast from them all on the same frequency so that the aircraft can determine which transmitter is using which sub-time slot Can avoid confusion. The use of prior art systems at multiple locations requires a considerable degree of equipment redundancy. BRIEF DESCRIPTION OF THE INVENTION The present invention proposes to use a single ground station for the entire area instead of using multiple ground stations, one for each location. The invention proposes to connect a data link between a single ground station and multiple transmitters. Since each transmitter operates on the same frequency, it can utilize the same information with the only difference being that the information transmitted to the receiver is transmitted to the appropriate time slot assigned to that receiver. This has the great advantage that the number of DGPS receivers used can be reduced and the equipment and complexity can be greatly reduced. Furthermore, the only requirement with this method is that the data link wraparound antennas can receive the signal from each transmit antenna so that a return signal can be provided to the ground station indicating what was transmitted to the aircraft. Can reduce the number of data link wraparound antennas and receivers, such as 44 and 46 in FIG. The system also simplifies the design of an onboard aircraft RX when signals need to be received from two receivers, such as during gliding guidance. The system also improves the system integrity of the precision approach by providing a redundant active path for transmission reliability without having to change the receiver frequency. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a prior art ground station system. FIG. 2 shows a FAA proposal that utilizes a single frequency transmission from multiple transmitters with specific time slot assignments. FIG. 3 shows a layout diagram of the present invention. Detailed Description of the Preferred Embodiment Referring to FIG. 3, four satellites via the paths indicated by arrows 12, 14, 16, and 18, similar to the example of FIG. 1, which may be the same as aircraft 10 of FIG. An aircraft 10 receiving signals from FS1, FS2, FS3, and FS4 is shown. The DGPS receiver 20, which may be the same as the DGPS receiver 20 of FIG. 1, transmits signals from the four satellites FS1, FS2, FS3, and FS4 via paths 24, 26, 28, and 30 as in the example of FIG. It is found in a fixed and known position with a receiving antenna 22 for receiving. As in the example of FIG. 1, the DGPS receiver 20 generates a signal on the line indicated by arrow 32 to the microprocessor 34. The .mu. processor computes a satellite-specific pseudorange error signal and transmits that information to the remote transmitters TX1, TX1,. Transmit to TX2 and TX3. The transmission lines 52, 54 and 56 can be selected from the wired connection, optical fiber, or wireless link that is most suitable for the site. Remote transmitters 58, 60, and 62 may all be located at a single airport to provide visibility of all aircraft from various angles, to ensure ground coverage, and It can also be located at various airports around the central area to ensure the best coverage. For example, if the transmitter's transmission range is 100 miles and there are three large airports in that area, transmitter 58 is located at the first of such airports and transmitter 60 is located at such a plurality of airports. Located at a second airport of the airport, transmitter 62 may be located at a third of such airports. Transmitter 58 may be more than one transmitter located at a single airport to avoid the problem of communication failure at individual airports, and the same applies to transmitters TX2 and TX3. Thus, the desired area can be covered with up to eight separate transmitters using the FAA model shown in FIG. Of course, if more transmitters are required, more frequency types are required. As in the example of FIG. 1, the transmitter TX1 using the antenna 68 transmits pseudorange error information specific to the satellite to the aircraft 10 indicated by an arrow 70. Similarly, transmitter 60 using antenna 74 transmits error information to aircraft 10 as indicated by arrow 76, and transmitter 62 using antenna 80 transmits error information to aircraft 10 as indicated by arrow 82. As shown in FIG. 3, all antennas 68, 74 and 80 use the same frequency, but use different sub-time slots. Thus, aircraft 10 can receive a single frequency signal from any one or all of these sources and determine which transmitter is transmitting the signal, thereby using the received information to determine Aircraft parameters can be accurately determined. To provide data link wraparound, receive the transmit information from all antennas 68, 74, and 80 via the paths indicated by arrows 86, 88, and 90, respectively, shown as antenna 84 in FIG. Can be placed where possible. In most cases, a single antenna will be used for this purpose; otherwise, multiple antennas may be employed. The signal received by antenna 84 is connected to receiver 86 and returned to ground station 20 via the connection indicated by arrow 94. Thus, there is provided a ground station repeater for a differential GPS system that can use a single frequency for transmission even when a plurality of transmitters simultaneously transmit signals to an aircraft while minimizing the number of required ground stations. I've been. Numerous modifications to the apparatus described with respect to the preferred embodiments will occur to those skilled in the art. The invention is not limited to the specific disclosures used in connection with the preferred embodiments, but only by the appended claims.

Claims (1)

[Claims] 1. Information that may include errors due to distortion in the path transmitted from multiple satellites to the object Information to determine one or more parameters of an object associated with the earth Differential global positioning system   A receiver that receives information from satellites and a microphone that determines error information due to path distortion A ground receiving station fixed to the earth at a known location, including a   At a first location remote from the receiver, connected to the receiver, and providing error information First transmitter means for receiving and transmitting the information to the object;   At a second location remote from the receiver, connected to the receiver, and providing error information Second transmitter means for receiving and transmitting the information to the object; Including system. 2. The first and second transmitting means are in different time slots at the same frequency The apparatus of claim 1, transmitting error information to an aircraft. 3. The object is an aircraft receiver and the first and second transmitting means are in proximity to the first airport. The first and second positions are selected and error information can be obtained without causing a communication failure due to an obstacle. 3. The apparatus according to claim 2, wherein the information can be transmitted to an aircraft. 4. The object is a receiver of an aircraft, and the first and second transmitting means are mutually in a normal transmission range. Located at a separate airport in the surrounding area, and the aircraft locates the transmitter without using multiple frequencies. Error information is provided at different times so that the An apparatus according to claim 2. 5. The distance error and distance the aircraft uses to land at the airport and glide to the terminal. 4. The method according to claim 3, wherein the parameter includes a separation error rate and other airport data. On-board equipment. 6. Aircraft landing at a selected one of the airports and gliding to the terminal The parameters include distance error, distance error rate and other airport data used for 5. The device according to claim 4, wherein the device comprises: 7. A transmission station configured to receive transmission information from the first and second transmitters; A data link wraparound connected to return the transmitted information The apparatus of claim 1, further comprising a receiving antenna. 8. Information from multiple satellites is received and processed by the ground station and all of the information in that information is The determined and processed information is transmitted to aircraft within the transmission range of the ground station and processed. All transmitted information is transmitted on a single frequency from several distant locations within the transmission range. Method for use with an improved differential global positioning system,   A. Multiple transmitters at least one remote from a single ground station Connecting to   B. Separate time slots for transmission of processed information to each transmitter Steps   C. The information processed by each transmitter during its assigned time slot Transmitting on a single frequency A method that includes 9. The transmission of the processed information between each time slot by the transmitter periodically 9. The method of claim 8, wherein the method is repeated. 10. Unobstructed from at least one transmitter to the aircraft at all aircraft locations Further comprising the step of arranging the transmitter so that transmission can be performed on the transmitter. The method according to claim 8. 11. A step of monitoring transmission information from a plurality of transmitters and returning the transmission information to a ground station. The method of claim 8, further comprising a loop. 12. If one or the other transmitter is masked or interfered The receiver simultaneously receives correction information from the two transmitters at a single frequency so that the signal can be retained. 9. The method according to claim 8, wherein the method is capable of receiving 13. If a highly reliable link is used in the CAT1116 approach, The receiver has a single round so that it can hold the signal when it needs to maintain the active state. 9. The apparatus according to claim 8, wherein the correction information can be received simultaneously from the two transmitters at the wave numbers. The method described in.