MH/T 4045-2017Civil aviation technical requirements for Ground. Based Augmentation System ground equipment. Category I precision approach (English PDF)

3.1 Terms and definitions

The following terms and definitions apply to this document.

3.1.1

Alarm

The system does not meet integrity/continuity requirements, or an indication that the service is unavailable.

3.1.2

Protection level

Envelope the actual error value with a certain degree of confidence.

3.1.3

Availability

The ability of the navigation system to provide the required functions and performance during the expected operation period.

3.1.4

Continuity

Ground equipment can provide horizontal and vertical guidance for class I precision approach services, or provide warning information for airborne systems within a 15 s period the average probability.

3.1.5

Signal in space integrity risk the ground equipment did not prompt the airborne system of the unavailable space signal information in time, resulting in the probability that the horizontal and vertical relative position error exceeded the tolerance limit.

rate.

3.1.6

Category I precision approach the minimum standard meets a precision approach with a decision height not less than 60 m, visibility not less than 800 m, or runway visual range not less than 550 m.

3.1.7

Ground-Based Augmentation System the ground-based augmentation system consists of the space part, the ground part and the aircraft part. The space part consists of one or more satellite navigation constellations, the ground part is installed in or near the airport, and the satellite navigation enhancement information is sent directly from the ground-based transmitter to the aviation user, and the corresponding aircraft is equipped.

Equipment-carrying aircraft can obtain Class I precision approaches or even higher levels of service.

3.1.8

Pseudo-range

The distance obtained by the receiver by measuring the time interval between the local time of the arrival of the navigation signal and the time of the satellite transmitting the signal Distance, including the geometric distance and clock difference between the two.

3.1.9

B value

After deducting the broadcast pseudorange correction, the reference receiver measures the residual error of the pseudorange.

3.1.10

Glide path intercept point the intersection of the final approach path and the runway level.

3.2 Abbreviations

The following abbreviations apply to this document.

4.1 Composition

GB AS ground equipment consists of a reference receiving subsystem, a processing subsystem, a very high frequency data broadcasting (VDB) subsystem and a monitoring and maintenance subsystem and other composition.

4.2 General requirements

4.2.1 The electromagnetic radiation of the equipment shall meet the limit requirements of the electromagnetic radiation protection for personnel specified in GB 8702.

4.2.2 The reference receiving subsystem usually consists of 3 to 4 GNSS reference receivers; the transceiver unit and processing subsystem of the VDB subsystem the processing unit should adopt a dual redundant structure.

4.2.3 The location configuration data of GB AS ground equipment uses the WGS-84 coordinate system.

4.2.4 GB AS ground equipment should have the following functions.

--Provide local related pseudorange correction;

--Provide relevant data of GB AS station;

--Provide final approach segment data;

--Provide the availability forecast data of the ranging source;

--Provide GNSS ranging source integrity monitoring.

4.2.5 The maintainability requirements are.

--The MTBF of the equipment should be greater than 20 000 h;

--The MTTR of the field replaceable unit should not exceed 30 min.

4.2.6 The power supply shall meet the following requirements.

a) The equipment should have both AC and DC power supply modes. Under normal circumstances, AC power is the main power supply; when the main power supply is cut off, it should be able to Automatically switch to the standby DC power supply without interruption; when the main power supply is restored, it should be able to automatically switch back to the AC power supply state;

b) The AC power source used by the equipment should be single-phase 220 V±15%, 45 Hz~63 Hz;

c) The rated voltage of the standby DC power supply (battery) used by the equipment should be 24 V, and the allowable range of variation is specified by the product specification;

d) The AC power supply should float the standby DC power supply while supplying power to the equipment normally;

e) Each power circuit should have protection circuits such as overcurrent and overvoltage;

f) The voltage and current of each part of the power supply should be able to be measured and displayed on the equipment;

g) The input end of the AC power supply should have a reliable lightning protection device.

4.2.7 The environmental conditions of the equipment shall meet the following requirements.

a) Indoor equipment should be able to operate normally in the following environment.

1) Working temperature. -10 °C~50 °C;

2) Relative humidity. 0%~95%;

3) Maximum working altitude. not less than 5 000 m above sea level;

b) Outdoor equipment should be able to operate normally in the following environment.

1) Working temperature. -40 °C~70 °C

2) Wind speed. 0~36 m/s;

3) Relative humidity. 0%~100%

4) Rainfall. 0~100 mm/h (wind speed is 18 m/s);

5) Snowfall. 0~195 kg/m2;

6) Ice coating. 0~50 mm (except radome);

7) Hail diameter. 0~13 mm;

8) Maximum salt spray concentration. not less than 5% (within continuous 48 hours);

9) Maximum working altitude. not less than 5 000 m above sea level;

10) Maximum vibration acceleration. not less than 4.9 m/s2 (frequency range 10 Hz~500 Hz).

4.2.8 The flexibility of equipment installed near the runway shall meet the airport regulations.

4.3 Performance requirements

4.3.1 Coverage

4.3.1.1 Coverage

4.3.1.2 Field strength

The effective radiation power field strength in the coverage area should be between -99 dBW/m2 and -35 dBW/m2.

4.3.2 Continuity requirements

The continuity of GB AS ground equipment should not be less than (1-8.0×10-6)/15 s.

4.3.3 Integrity requirements

4.3.3.1 The risk of GB AS space signal integrity should not be greater than 2×10-7/approach, and its allocation is as follows.

--The space signal integrity risk caused by the protection level integrity risk is not greater than the approach;

--GB AS The space signal integrity risk caused by ground equipment is not greater than the approach.

4.3.3.2 The lateral warning limit of the final approach segment shall not exceed 40 m.

4.3.3.3 The vertical warning limit of the final approach segment shall not exceed 10 m.

4.3.3.4 When GB AS ground equipment broadcasts Type 1 telegrams, the maximum alarm time should not exceed 3 s.

4.3.3.5 The probability of not detecting a single reference receiver failure (affecting the reference processing function) should be less than the approach.

4.3.3.6 The broadcast time delay of alarm data that causes the position error to exceed the protection level under normal measurement conditions should not be greater than 3 s.

4.3.3.7 When the unallocated time slot transmits a signal greater than -105 dBc within 1 s, the risk of not being detected shall be less than that.

4.3.4 Accuracy requirements

When the confidence probability is 95%, the horizontal accuracy of GB AS ground equipment should be better than 16.0 m, and the vertical accuracy should be better than 4.0 m.

4.3.5 Availability requirements

4.3.5.1 The availability of GB AS ground equipment (excluding satellite constellations) is not less than 0.9992.

4.3.5.2 When providing the same level of performance as the instrument landing system (ILS) category I precision approach, the availability of GB AS equipment should be greater than 0.9975.

4.4 Technical requirements for reference receiving subsystem

4.4.1 Requirements for reference receivers

4.4.1.1 Receiving, tracking and decoding GNSS satellite space signals.

4.4.1.2 Measure the pseudorange observations from the receiver to each visible GNSS satellite, as well as the Doppler observations.

4.4.1.3 Output time-stamped satellite information (pseudorange measurement data, ephemeris data, almanac data, etc.) and satellite status data.

4.4.1.4 The update rate of pseudorange measurement data is 2 Hz.

4.4.2 Reference receiving antenna requirements.

4.4.2.1 The radio frequency index is as follows.

a) 3 dB bandwidth (typical value). 1 150 MH z~1 650 MH z;

b) Gain, the indicators are as follows.

1) Zenith gain. 2 dBic;

2) Gain change from zenith to level. -10 dB~-15 dB;

3) Out-of-roundness. less than 1 dB;

c) Phase center stability. less than 2 mm;

d) Standing wave ratio. less than 2.0;

e) Rated impedance. 50 ohm.

4.4.2.2 The low noise amplifier indicators are as follows.

a) Noise figure. less than 1.5 dB;

b) Bandwidth. 1 100 MH z~1 700 MH z;

c) Gain (typical value). 25±2 dBi;

d) Group delay. less than 5 ns;

e) Standing wave ratio. less than 2.0;

f) Rated impedance. 50 ohm;

g) Interface. TNC.

4.5 Technical requirements for processing subsystems

4.5.1 The processing subsystem can process at least 12 satellites.

4.5.2 The processing subsystem shall have the following functions.

a) It should be possible to eliminate invalid ranging sources;

b) It should be able to generate type 1, 2, and 4 messages (see Appendix A for details);

c) Should support FAS data maintenance and management;

d) It should be able to monitor GNSS ranging sources, ephemeris, ground pseudorange standard deviation, B value, GNSS navigation data;

e) It should be able to verify the content and format of all types of messages transmitted to VDB;

f) It should be able to monitor the content and format of all types of messages.

4.5.3 The processing system should generate and send differential correction data and correction change rate data at a rate of at least 2 times per second.

4.6 Technical requirements for VDB subsystem

4.6.1 VDB transmitter

4.6.1.1 The working frequency range of VDB is from 108 MH z to 117.975 MH z, and the interval between two adjacent frequencies (channel spacing) is 25 kHz, the tolerance of the operating frequency should not exceed ±2×10-6 Hz of the selected frequency.

4.6.1.2 The maximum output power (average value) of the VDB transmitter is not less than 50 W, and the output power is adjustable.

4.6.1.3 The rise time of the VDB transmitter output power level should not be greater than 190.5 µs, and the steady-state output level duration should not be less than 476.2 µs.

4.6.1.4 The time for the steady-state output level of the VDB transmitter to decay below 30 dB of this level should not be longer than 285.7 µs.

4.6.1.5 The error vector magnitude (EVM) of the VDB transmitted signal shall not be less than 6.5% rms.

4.6.1.6 Unwanted emission should meet the values specified in Table 1, and the total power of any VDB harmonic or discrete signal should not be greater than -53 dBm.

Table 1 Unwanted emission regulations

Frequency relative unwanted radiation level Maximum unwanted radiation level 9 kHz~150 kHz -93 dBc -55 dBm/1 kHz 150 kHz~30 MH z -103 dBc -55 dBm/10 kHz

4.6.1.7 The power output of the VDB transmitter should not be less than -3 dB of the rated value, and the power value of the adjacent channel transmission should not exceed the value specified in Table 2.

4.6.1.8 Relative to the power on the allocated time slot, the power radiation on the unallocated time slot shall not be greater than -105 dBc.

4.6.1.9 Intermodulation attenuation shall not be less than 10 dB of the decoupling value.

4.6.1.10 When the VDB transmitter detects the following conditions, the ground equipment should stop data broadcasting within 0.5 s.

--The duration of the transmit power being 3 dB higher than the nominal value exceeds 1 s;

--VDB transmitter has not transmitted for more than 3 s.

4.6.2 VDB receiver

4.6.2.1 The working frequency range of VDB receiver is 108 MH z~117.975 MH z.

4.6.2.2 The sensitivity range of VDB receiver is -87 dBm~-1 dBm.

4.6.2.3 The uncorrected bit error rate of the VDB receiver shall not be greater than 10-4 in the following cases.

- Within the dynamic range of the VDB receiver;

--Symbol rate deviation ±5.0×10-5;

--The frequency shift is in the range of nominal frequency ±236 Hz;

--There are signals not greater than 15 dBm on different time slots of the same channel;

--There is an interference signal smaller than 26 dB of the useful signal on the same time slot of the same channel.

4.6.2.4 The VDB receiver shall have the ability to suppress the first, second and third adjacent channels.

4.6.2.5 VDB receivers should have out-of-band suppression capabilities.

4.6.2.6 The spurious radiation level of the VDB receiver should not be greater than -57 dBm in the frequency range of 50 kHz~108 MH z and 137 MH z~1 215 MH z.

The frequency range of 108 MH z~137 MH z should not be greater than -64 dBm.

4.6.2.7 The linear relationship of the VDB receiver should ensure that the third-order intermodulation point is at least 0 dBm.

4.6.2.8 When the VDB receiver detects the following conditions in the RF signal of the received VDB transmitter, it shall stop data broadcasting within 0.5 s.

- More than 0.2% of the messages have not been sent within the last 1 hour;

--The detection lasted more than 3 s without sending any message type;

-Any inconsistency between the application data to be transmitted within 3 s and the application data saved or extracted by the monitoring system before transmission.

4.6.3 Access Technology

4.6.3.1 RF characteristics are as follows.

--Data should use octal differential phase shift keying (D8PSK) modulation method, the rate is 10 500 characters per second;

--GB AS messages should be combined into symbols, each containing 3 consecutive message bits;

--The output of the differential phase encoding of the baseband signal should be filtered through a pulse shaping filter.

4.6.3.2 The nominal bit rate is 31 500 bit/s.

4.6.3.3 TDMA shall use a fixed frame structure and consist of 8 time slots.

4.6.3.4 The timing structure of data broadcasting shall be based on frames and time slots. Each frame shall last for 500 ms. Each 1 s UTC time point shall contain two Time frame, the first frame starts from the beginning of UTC time, and the second frame starts from 0.5 s after UTC time.

4.6.3.5 Each allocated time slot shall contain at most one burst; in order to initialize the time slot use, the equipment shall be specified in 5 consecutive time frames.

Broadcast a burst in a fixed time slot; for used time slots, the device should broadcast a burst at least once in one of every 5 consecutive time frames pulse.

4.6.3.6 Each burst pulse shall be contained in a 62.5 ms time slot; the burst pulse starts at 95.2 µs after the beginning of the time slot.

4.6.3.7 The organization and coding requirements of burst pulses are as follows.

--The elements of each burst include. burst start, power stabilization, synchronization and fuzzy resolution, data reordering, filling bits, burst End;

--The coding of information sent to the airborne subsystem shall be carried out in the following order. application of data formatting, generation of training sequence FEC, generation of Complete application FEC, bit check;

--Synchronization and ambiguity resolution fields should contain a 48-bit sequence. 010 001 111 101 111 110 001 100 011 101 100 000 011 110 010 000, and continuously transmit from the lower position first.

4.6.3.8 The requirements for reordering data are as follows.

--Content should include. SSID, data length, training sequence FEC, application data and application FEC;

--SSID corresponds to the code number of the time slot allocated by the ground station, 0 represents the A time slot, and 7 represents the H time slot;

--Data length is the total number of bits of application data and application FEC;

--The training sequence FEC should calculate the SSID and data length fields, using a (25,20) block coding;

-Application data should be composed of one or more information blocks;

--Application FEC should be calculated by using fixed-length Reed-Solomon (RS) (255,249) 28-ary block coding.

4.6.3.9 Filling bits should be used to supplement the entire symbol when transmitting, and data scrambling may not use filling bits.

4.6.3.10 VDB shall have the function of using pseudo noise scrambler for bit scrambling.

4.6.3.11 TDMA monitoring.

- TDMA time slot for data broadcasting;

--When detecting that the transmission duration outside the time slot exceeds 1 s, the ground equipment should stop data broadcasting within 0.5 s.

4.6.4 VDB antenna

4.6.4.1 The VDB antenna provides VHF data broadcasting with horizontal polarization or elliptical polarization.

4.6.4.2 The VDB antenna shall have the ability to suppress ground radiation, and the signal attenuation loss caused by ground radiation shall not exceed 10 dB.

4.6.4.3 The input impedance of the VDB antenna is 50 ohm.

4.6.4.4 VDB antenna VSWR is not greater than 2.0.

4.6.5 Data broadcasting requirements

4.6.5.1 The coding of broadcast data shall follow the coding regulations in Appendix A.

4.6.5.2 All static parameters of the broadcast shall be stored in the device database.

4.6.5.3 The signed parameter in the broadcast data shall be 2's complement, and the unsigned parameter shall be an unsigned fixed-point number.

4.6.5.4 The frequency of telegram broadcasting shall meet the requirements of Table 3.

4.7 Technical requirements for monitoring and maintenance subsystems

4.7.1 Local/remote monitoring and maintenance

4.7.1.1 Control should include.

--Normal/maintenance/test mode, with mode selection function;

--VDB launch control;

--Manually reset and shut down, automatically restart the device;

--Indicating test;

--switch;

--Switch between AC power and battery;

--Continuous wave mode selection of VDB transmitter test state.

4.7.1.2 The status display shall include.

- "Normal" indication;

- "Alarm" indication;

- "Maintenance alert" indication;

--"Test status" indication;

--"Power status" indication;

-Indicate the status of the main ground subsystem components (processors, transmitters, etc.), including duplicate and redundant components.

4.7.1.3 Maintenance shall include.

--The management subsystem should at least be able to configure GNSS antenna coordinates, VDB frequency, allocated time slots, and VDB transmit power;

--Automatically or manually start component diagnosis;

--Display internal storage data;

--Display internal parameters;

--Password protection of operation;

--Manage users and passwords;

--Display all alarm status;

--Alarm/configuration change history record, including monitoring integrity and satellite trigger events, and monitoring parameter status during shutdown/conversion;

--Display the status of each subsystem and active module;

--Display and modify the alarm threshold;

--FAS data loading and reasonableness check;

--Display FAS data and the status of each FAS approach supported by the equipment.

4.7.1.4 The function of local/remote monitoring and maintenance terminal can be configured according to user requirements.

4.7.2 Tower control and status display

4.7.2.1 The control functions of tower control include.

--Disable some or all of the FAS data provided by the device;

--Tower control and status display unit index test.

4.7.2.2 The status display functions of the tower control include.

--Display device mode status;

--Display the actual satellite constellation warning information;

--Display satellite constellation warning prediction information;

--Provide status indication and sound alarm selection function.

4.7.2.3 The functions of tower control and status display can be configured according to control requirements.

4.7.3 Record

4.7.3.1 It shall be able to record the date, time, internal temperature, login, logout, alarm, service alarm, alarm event within 90 days, and can display, export, and print record information on the maintenance terminal.

4.7.3.2 It should be possible to use the data from the monitor to indicate hourly, daily, monthly, and yearly error characteristics in the broadcast correction amount.

4.7.3.3 It should be able to record the output data of the equipment not less than 30 days old. The output data includes the time stamp, the reference receiver data, and the transmitted data.

There is VDB information.

4.7.3.4 It should be able to record the raw data output by all reference receivers not less than 30 days old.

4.7.4 Interface

Should have a universal standard output data interface.

Appendix A

(Normative appendix) GB AS message format and usage A.1 Application layer message content A.1.1 Message block all data broadcast information is composed of message block identification, message and 32-bit cyclic redundancy check code, and its structure is shown in Table A.1 Said.

Note. All binary numbers are from the most significant bit (MSB) to the least significant bit (LSB) from left to right.