CN114063004A - Novel method for realizing MLS scanning beam - Google Patents

Novel method for realizing MLS scanning beam Download PDF

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Publication number
CN114063004A
CN114063004A CN202111330373.1A CN202111330373A CN114063004A CN 114063004 A CN114063004 A CN 114063004A CN 202111330373 A CN202111330373 A CN 202111330373A CN 114063004 A CN114063004 A CN 114063004A
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signal
milliseconds
time slot
scanning beam
scanning
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CN114063004B (en
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王士岩
王洪迅
程嗣怡
白冰
姜亚华
王建
马洪平
李小跃
陈游
王星
陈相
宋彦博
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Pla 93286
Air Force Engineering University of PLA
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Air Force Engineering University of PLA
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • G01S1/08—Systems for determining direction or position line
    • G01S1/14—Systems for determining direction or position line using amplitude comparison of signals transmitted simultaneously from antennas or antenna systems having differently oriented overlapping directivity-characteristics
    • G01S1/16—Azimuthal guidance systems, e.g. system for defining aircraft approach path, localiser system

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Abstract

The invention discloses a new method for realizing MLS scanning beam, which deeply and carefully analyzes the basic format of MLS signals, and is realized by adopting GNUradio software simulation and HackRF one hardware of software radio technology. The method adopts a quadratic form of a Gaussian function, can be used as a new algorithm for forming scanning beams, so that the MLS scanning beams can meet the requirements of the international civil aviation convention on the scanning beams in a baseband signal stage, the realization in engineering is easier, and development resources are saved.

Description

Novel method for realizing MLS scanning beam
Technical Field
The invention belongs to the technical field of aviation, and relates to a novel method for realizing MLS scanning beam.
Background
The Microwave Landing System (MLS) is an all-weather and accurate aviation radio navigation system with advanced technical system. The MLS system is mainly composed of an azimuth guidance station and an elevation guidance station, and provides azimuth information and elevation information of approach and landing for the airplane, which are collectively called angle guidance information. The angle guidance information of the airplane is obtained by measuring the time difference between two MLS scanning wave beams transmitted by a ground angle guidance antenna (comprising an azimuth antenna and an elevation angle antenna) after the two MLS scanning wave beams are received by an onboard receiver. Currently, the MLS scanning beam mostly adopts Sa function, taylor function, gaussian function or quasi-gaussian function as baseband signals, and the baseband signals generated by these functions do not meet the requirement of international civil aviation convention on the MLS scanning beam-3 dB spot width, i.e. the beam width of the scanning beam when the amplitude is-3 dB is half of the whole scanning beam width. In the engineering practice, a filtering hardware circuit is also needed to be designed to carry out smooth filtering on the radio frequency signals of the MLS scanning beam so as to change the-3 dB point width to meet the requirements.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a new method for realizing MLS scanning beams, and provides a new algorithm for realizing MLS scanning beams, wherein the algorithm enables the scanning beams to meet the requirements of the international civil aviation convention at the baseband signal stage.
The technical scheme is as follows:
a new method of implementing MLS scanning beams comprising the steps of:
(1) establishing a mathematical model of the scanning beam:
Figure BDA0003348590620000021
wherein, U (x) represents the mathematical model of the scanning beam, x represents the radian of the mathematical model of the scanning beam, and x has the value range of [ -pi, pi [ -pi [ ]]，e(.)Denotes the exponential operation with the natural constant e as base, K and b0All are constants, and when a specific value is taken, the-3 dB point of the scanning beam is half of the width of the scanning beam.
(2) Constructing an argument value of a scanning beam;
since the independent variable in the mathematical model of the scanning beam is the radian value, the independent variable is set as
Figure BDA0003348590620000022
The function period is [ -pi, pi [ -pi [ ]]. The scanning beam time period is set as T, the 0 moment corresponds to-pi, and the T moment corresponds to pi. Let a beam width be Δ T, then a beam width arc value be
Figure BDA0003348590620000023
Therefore, the argument x of the scanning beam with the start time 00Should be that
Figure BDA0003348590620000024
Wherein
Figure BDA0003348590620000025
Scanning beam self-encoding value x at any timenIs composed of
Figure BDA0003348590620000026
After finishing, the product is obtained
Figure BDA0003348590620000027
Wherein
Figure BDA0003348590620000028
t is the starting instant at which the scanned beam occurs.
(3) Obtaining scanning beam values
The scanning beam at any time is subjected to an argument xnThe scan beam value at any time can be obtained by substituting the mathematical model of the scan beam as follows.
Figure BDA0003348590620000031
Adjusting k and b in the above formula0Value, when k is 1.12, b 01/3, the requirement of the international civil aviation convention on the MLS scanning beam-3 dB point width is met.
(4) Acquiring specific parameter values in various microwave landing signals;
1) orientation signal
a. The preamble slot is allocated to 0 to 1.600 milliseconds, and mainly includes a reference time code and a function identification code.
b. The time slot allocation for the sector signal is 1.600 ms to 2.432 ms. Three OCI pulses are required to be generated by a sector signal, wherein the three OCI pulses are a left outer OCI, a right outer OCI and a rear OCI pulse respectively, and each OCI pulse occupies a 128 microsecond time slot; and simultaneously generating a 1-bit DPSK ground identification code and a 6-bit DPSK modulated airborne antenna selection pulse.
c. The scan signal slot allocation is 2.432 to 15.900 milliseconds. The scanning signal needs to generate amplitude-modulated forward and backward test pulses, and between two test pulses, the scanning beam value obtained in step (3) is applied to generate a forward scanning beam in a time slot of 2.560 milliseconds to 8.760 milliseconds and a backward scanning beam in a time slot of 9.360 milliseconds to 15.560 milliseconds.
2) Pitch signal
a. And in accordance with the azimuth signal, the lead code time slot is allocated to be 0 to 1.600 milliseconds and mainly comprises a reference time code and a function identification code.
b. The sector signal slots are allocated between 1.728 milliseconds and 1.856 milliseconds. In the sector signal, only one kind of OCI signal is generated, and the OCI pulse occupies a 128-microsecond time slot.
The c-scan signal slot allocation is 1.856 milliseconds to 5.600 milliseconds. Applying the scan beam values obtained in step (3), the "go" scan beam is generated in the 1.856 ms to 3.406 ms time slot, and the "return" scan beam is generated in the 3.806 ms to 5.356 ms time slot.
3) High speed azimuth signal
a. The high-speed azimuth signal is similar to the azimuth signal, and the preamble time slot is allocated to be the first 1.600 milliseconds and mainly comprises a reference time code and a function identification code.
b. The sector signal slot allocation is 1.600 ms to 2.432 ms, consistent with the azimuth signal allocation.
c. Applying the scan beam values obtained in step (3), the scan signal slot allocation is 2.432 ms to 11.900 ms, the "go" scan beam is generated in the 2.560 ms to 6.760 ms slot, and the "return" scan beam is generated in the 7.360 ms to 11.560 ms slot.
4) Flattening signals
a. Similar to the direction signal, the preamble slot is allocated to the first 1.600 milliseconds, and mainly includes a reference time code and a function identification code.
b do not generate sector signals and the scan signal time slot is allocated to 1.600 ms to 5.300 ms. The generated scanning signals only comprise a 'go' scanning signal and a 'return' scanning signal, and the scanning beam values acquired in the step (3) are applied to generate the 'go' scanning beam in a time slot of 1.856 milliseconds to 3.056 milliseconds and the 'return' scanning beam in a time slot of 3.856 milliseconds to 5.056 milliseconds.
5) Anti-azimuth signal
a. Similar to the direction signal, the preamble slot is allocated to the first 1.600 milliseconds, and mainly includes a reference time code and a function identification code.
b. The sector signal time slot allocation is 1.600 ms to 2.432 ms.
c. Applying the scan beam values obtained in step (3), the "go" scan beam is generated in the 2.560-6.760 ms slot and the "return" scan beam is generated in the 7.360-11.560 ms slot.
6) Basic data word
a. The basic data word preamble slot is allocated to the first 1.600 milliseconds. A functional identification code of the 7-bit DPSK modulation is generated.
b. Unlike the azimuth signal, the basic data word signal only contains 20-bit DPSK modulated basic data signal, the time slot is allocated to 1.600 ms to 3.100 ms, the first 18 bits are information bits, and the last 2 bits are parity bits.
7) Auxiliary data word signal
a. The auxiliary data word preamble slot is allocated 1.600 milliseconds first. Containing a 7-bit DPSK modulation function identification code.
b. The auxiliary data signal time slots are allocated between 1.600 milliseconds and 5.900 milliseconds. A 64-bit DPSK modulated auxiliary data signal is generated.
(5) Generating various microwave landing signals;
according to the time slot allocation format of the microwave landing signal in the step (4), a time division multiplexing method is adopted, and a receiver reference time code, a function identification code, a station identification code, an antenna selection pulse, an OCI rear signal, an OCI left signal, an OCI right signal, a forward check pulse, a return check pulse, tail protection time, a forward scanning signal, a return scanning signal and other designated parameters are combined together to form a microwave landing azimuth signal, a pitching signal, a high-speed azimuth signal, a leveling signal, a reverse azimuth signal, a basic data word signal and an auxiliary data word signal with complete functions.
(6) Selecting a desired microwave landing signal
And selecting the required microwave landing signal according to the function identification code of each microwave landing signal.
(7) Generating a microwave landing sequence;
and performing time sequence control on the selected microwave landing signals by adopting a time division multiplexing method to generate a microwave landing sequence 1 and a microwave landing sequence 2.
(8) Generating a full-period microwave landing signal;
and (3) arranging time slots of the sequence 1 and the sequence 2 by adopting a time division multiplexing method, wherein the time slot intervals among the sequences are respectively 1ms, 13ms, 19ms, 2ms, 20ms, 6ms and 0ms, and generating microwave landing full-period digital baseband signals. The duration of the full-period signal is not more than 615ms, and the interval of each full-period signal is 18 ms.
Further, the method also comprises the following steps: (9) and (3) performing simulation verification on the GNUradio software high-speed full-period functional sequence digital baseband signal.
Further, the method also comprises the following steps: (10) HackRF one hardware test.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts a new algorithm to form the MLS scanning beam, so that the MLS scanning beam can meet the requirement of the international civil aviation convention at the baseband signal stage, the step of hardware debugging is omitted, the MLS scanning beam is easier to realize in engineering, and development resources are saved.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a high speed azimuth scanning beam;
FIG. 3 is a high speed full period signal intercept of an oscilloscope output MLS.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Take the generation of a high-speed full-cycle microwave landing signal as an example.
(1) Establishing a mathematical model of the scanning beam:
Figure BDA0003348590620000061
wherein, U (x) represents the mathematical model of the scanning beam, x represents the radian of the mathematical model of the scanning beam, and x has the value range of [ -pi, pi [ -pi [ ]]，e(.)Denotes exponential operation with a natural constant e as base, K is taken to be 1.12 and b 01/3 is taken.
(2) Constructing an argument value of a scanning beam;
since the independent variable in the mathematical model of the scanning beam is the radian value, the independent variable is set as
Figure BDA0003348590620000062
The function period is [ -pi, pi [ -pi [ ]]. The scanning beam time period is set as T, the 0 moment corresponds to-pi, and the T moment corresponds to pi. Let a beam width be Δ T, then a beam width arc value be
Figure BDA0003348590620000071
Therefore, the argument x of the scanning beam with the start time 00Should be that
Figure BDA0003348590620000072
Wherein
Figure BDA0003348590620000073
Scanning beam self-encoding value x at any timenIs composed of
Figure BDA0003348590620000074
After finishing, the product is obtained
Figure BDA0003348590620000075
Wherein
Figure BDA0003348590620000076
t is the starting instant at which the scanned beam occurs.
(3) Obtaining scanning beam values
The scanning beam at any time is subjected to an argument xnThe scan beam value at any time can be obtained by substituting the mathematical model of the scan beam as follows.
Figure BDA0003348590620000077
(4) Acquiring specific parameter values in various microwave landing signals;
1) orientation signal
a. And differentially encoding the reference time code and the function identification code in the preamble by using an unmodulated carrier of the first 1.6 millisecond preamble signal as a segment synchronization head to generate a 5-bit DPSK modulated time reference code and a 7-bit DPSK modulated function identification code corresponding to the azimuth signal, wherein the time reference code time slot is allocated to be 0.832 milliseconds to 1.152 milliseconds, and the function identification code time slot is allocated to be 1.152 milliseconds to 1.600 milliseconds.
b. The time slot allocation for the sector signal is 1.600 ms to 2.432 ms. Wherein the device identification code occupies a time slot of 1.600 milliseconds to 1.664 milliseconds; the time slot occupied by the antenna selection pulse is 1.664-2.048 milliseconds; the sector signal needs to generate three OCI pulses, namely a left outer OCI, a right outer OCI and a rear OCI pulse, each OCI pulse occupying a 128 microsecond slot, wherein the rear OCI signal slot is allocated from 2.048 milliseconds to 2.176 milliseconds, the left OCI signal slot is allocated from 2.176 milliseconds to 2.304 milliseconds, and the right OCI signal slot is allocated from 2.304 milliseconds to 2.432 milliseconds.
c. The scan signal slot allocation is 2.432 to 15.900 milliseconds. Scanning signals need to generate amplitude-modulated forward and backward test pulses, the pulse width is 128 microseconds, the time interval between the two test pulses is 13000 +/-128 microseconds, the time slot occupied by the forward test pulse is 2.432 milliseconds to 2.560 milliseconds, and the time slot occupied by the backward test pulse is 15.560 milliseconds to 15.688 milliseconds; between two test pulses, the scan beam values obtained in step (3) are applied to generate an "outbound" scan beam in a time slot of 2.560 to 8.760 ms and an "inbound" scan beam in a time slot of 9.360 to 15.560 ms.
2) Pitch signal
a. The method is consistent with the azimuth signal, a carrier capture section in the preamble is used as a reference value in the first 1.6 milliseconds, a receiver reference time code and a function identification code in the preamble are differentially encoded, the preamble format and the time slot distribution of the elevation signal are similar to the azimuth signal, and the difference is that the generated function identification code modulated by 7-bit DPSK corresponds to the elevation signal;
b. the sector signal slots are allocated between 1.728 milliseconds and 1.856 milliseconds. In the sector signal, only one kind of OCI signal is generated, and the OCI pulse occupies a 128-microsecond time slot.
The c-scan signal slot allocation is 1.856 milliseconds to 5.600 milliseconds. Applying the scan beam values obtained in step (3), the "go" scan beam is generated in the 1.856 ms to 3.406 ms time slot, and the "return" scan beam is generated in the 3.806 ms to 5.356 ms time slot.
3) High speed azimuth signal
a. The high-speed azimuth signal is similar to the azimuth signal, the lead code time slot is distributed to the first 1.600 milliseconds, and only the generated 7-bit DPSK modulated functional identification code is different from the azimuth signal;
b. the time slot allocation for the sector signal is 1.600 ms to 2.432 ms. Wherein the device identification code occupies a time slot of 1.600 milliseconds to 1.664 milliseconds; the antenna selection pulse occupies a time slot of 1.664-2.048 milliseconds, each OCI pulse occupies a 128-microsecond time slot, and the left outer OCI, right outer OCI and rear OCI pulse time slot allocation and azimuth signal are completely consistent.
c. The scan signal time slot allocation is 2.432 to 11.900 milliseconds. The scanning signal needs to generate amplitude-modulated forward and backward test pulses, wherein the forward test pulse occupies a time slot of 2.432 milliseconds to 2.560 milliseconds, and the backward test pulse occupies a time slot of 11.560 milliseconds to 11.688 milliseconds; between two test pulses, the scan beam values obtained in step (3) are applied to generate an "outbound" scan beam in a time slot of 2.560 to 6.760 ms and an "inbound" scan beam in a time slot of 7.360 to 11.560 ms.
4) Flattening signals
a. And in accordance with the direction signal, the lead code time slot is allocated to the first 1.600 milliseconds, a section of intercepted unmodulated carrier is used as a section synchronization head, a time reference code modulated by 5 bits of DPSK is generated, and a function identification code modulated by 7 bits of DPSK is generated to correspond to a leveling signal.
b do not generate sector signals and the scan signal time slot is allocated to 1.600 ms to 5.300 ms. The generated scanning signals only comprise a 'go' scanning signal and a 'return' scanning signal, and the scanning beam values acquired in the step (3) are applied to generate the 'go' scanning beam in a time slot of 1.856 milliseconds to 3.056 milliseconds and the 'return' scanning beam in a time slot of 3.856 milliseconds to 5.056 milliseconds.
5) Anti-azimuth signal
a. The anti-azimuth signal is similar to the high-speed azimuth signal, the preamble time slot is allocated to the first 1.600 milliseconds, the difference is that the functional identification code is different, and the generated functional identification code symbol of 7-bit DPSK modulation is 1001001, which corresponds to the anti-azimuth signal.
b. The sector signal time slot is allocated to be 1.600 milliseconds to 2.432 milliseconds, wherein the device identification code occupies the time slot to be 1.600 milliseconds to 1.664 milliseconds; the antenna selection pulse occupies a time slot of 1.664-2.048 milliseconds, each OCI pulse occupies a 128-microsecond time slot, and the left outer OCI, right outer OCI and rear OCI pulse time slot allocation and azimuth signal are completely consistent.
c. Applying the scan beam values obtained in step (3), the "go" scan beam is generated in the 2.560-6.760 ms slot and the "return" scan beam is generated in the 7.360-11.560 ms slot.
6) Basic data word
a. The basic data word preamble slot is allocated to the first 1.600 milliseconds. A functional identification code for 7-bit DPSK modulation is generated, with a basic data word 1 having a symbol of 0101000, a basic data word 2 having a symbol of 0111100, a basic data word 3 having a symbol of 1010000, a basic data word 4 having a symbol of 1000100, a basic data word 5 having a symbol of 1101100, and a basic data word 6 having a symbol of 0001101
b. Unlike the azimuth signal, the basic data word signal only contains 20-bit DPSK modulated basic data signal, the time slot is allocated to 1.600 ms to 3.100 ms, the first 18 bits are information bits, and the last 2 bits are parity bits. The symbols for the information bits and parity bits may be set according to actual needs.
7) Auxiliary data word signal
a. The auxiliary data word preamble slot is allocated 1.600 milliseconds first. Contains a 7-bit DPSK modulation function identification code, wherein the symbols of the auxiliary data word a are 1110010, the symbols of the basic data word B are 1010111, and the symbols of the basic data word C are 1111000.
b. The auxiliary data signal time slots are allocated between 1.600 milliseconds and 5.900 milliseconds. The auxiliary data signal of 64-bit DPSK modulation is generated, the first 8 bits are address code, the middle 49 bits are information bits, and the last 7 bits are parity check bits. The code elements of the address code, the information bits and the parity check bits can be set according to actual needs.
(5) Generating various microwave landing signals;
according to the time slot allocation format of the microwave landing signal in the step (4), a time division multiplexing method is adopted, and a receiver reference time code, a function identification code, a station identification code, an antenna selection pulse, an OCI rear signal, an OCI left signal, an OCI right signal, a forward check pulse, a return check pulse, tail protection time, a forward scanning signal, a return scanning signal and other designated parameters are combined together to form a microwave landing azimuth signal, a pitching signal, a high-speed azimuth signal, a leveling signal, a reverse azimuth signal, a basic data word signal and an auxiliary data word signal with complete functions.
(6) Selecting a desired microwave landing signal
According to the function identification code of each microwave landing signal, an azimuth signal, an elevation signal, an anti-azimuth signal, a high-speed azimuth signal, a leveling signal, a basic data word 1, a basic data word 2, a basic data word 4, a basic data word 6, an auxiliary data word A1, an auxiliary data word A2, an auxiliary data word A3 and an auxiliary data word A4 are selected.
(7) Generating a microwave landing sequence;
and performing time sequence control on the selected microwave landing signals by adopting a time division multiplexing method. The high speed sequence 1 signal comprises an elevation angle, a high speed approach azimuth and basic data word signals, and the total time sequence is arranged to be 64.9 milliseconds. The high-speed sequence 1 signal time sequence arrangement format is as follows: elevation signal (5.600 ms), high speed azimuth signal (11.900 ms), basic data word (3.100 ms), high speed azimuth signal (11.900 ms), elevation signal (5.600 ms), high speed azimuth signal (11.900 ms), elevation signal (5.600 ms).
The high speed sequence 2 signal consists of elevation, high speed approach bearing, anti-bearing and basic data word 2 signals, with a total timing alignment of 67.5 milliseconds. The high-speed sequence 2 signal arrangement format is: elevation signal (5.600 ms), high speed azimuth signal (11.900 ms), basic data word 2(3.100 ms), anti-azimuth signal (11.900 ms), high speed azimuth signal (11.900 ms), elevation signal (5.600 ms), high speed azimuth signal (11.900 ms), elevation signal (5.600 ms).
(8) Generating a full-period microwave landing signal;
and arranging the time slots of the sequence 1 and the sequence 2 by adopting a time division multiplexing method, wherein the time slot intervals among the sequences are respectively 1ms, 13ms, 19ms, 2ms, 20ms, 6ms and 0ms, and generating the microwave landing full-period digital baseband signal. The time length of the full-period signal is not more than 615ms, and the interval of each full-period signal is 18 ms.
Further, the method also comprises the following steps: (9) performing simulation verification on a GNUradio software high-speed full-period functional sequence digital baseband signal;
and (3) performing simulation verification on the digital baseband signal of the high-speed full-period functional sequence of the MLS by using a custom module of a C + + language in GNUradio software. According to the steps (1) to (8), the C + + language in GNUradio software is applied to self-define an azimuth signal module, an elevation signal module, an anti-azimuth signal module, a high-speed azimuth signal module, a leveling signal module, basic data words 1, 2, 3, 4, 5 and 6 modules and an auxiliary data word A, B, C, D module, according to the function identification code, the required high-speed azimuth signal module, the elevation angle signal module, the reverse bit angle signal module, the basic data word 1 module, the basic data word 2 module, the basic data word 4 module, the basic data word 6 module, the auxiliary data word A1 module, the auxiliary data word A2 module, the auxiliary data word A3 module and the auxiliary data word A4 module are obtained through function selection, and all function signals are arranged in different time sequences through time sequence control, so that the sequence 1 and the sequence 2 are generated. The two sequences are arranged in different time slots with the interval of 1ms, 13ms, 19ms, 2ms, 20ms, 6ms and 0ms to generate high-speed full-period digital baseband signals for microwave landing, and the interval of each full-period signal is 18 ms.
(10) HackRF one hardware testing
Based on the MLS high-speed full-period functional sequence digital baseband signal generated by the gnu radio software in step (9), a HackRF one is selected as a hardware implementation carrier, the baseband signal is converted into a radio frequency signal, a carrier frequency is set to 410MHz in a test for facilitating waveform observation by an oscilloscope, a scanning beam width of the high-speed azimuth signal in the test is set to 300us, a width between half-power points (-3dB) of a measured rising edge and a measured falling edge is 150us, and a requirement of the international civil aviation convention on the microwave landing scanning beam width is met, as shown in fig. 2. The result of the high-speed full-period functional sequence digital baseband signal partial interception test is shown in fig. 3; the carrier frequency of the HackRF one hardware is set to be the same as that of airborne microwave landing equipment, azimuth and elevation indication tests and station identification sound function tests are carried out on the HackRF one hardware, azimuth and elevation indication is correct, and station identification sound in the earphone is clear.
The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and any simple modifications or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are within the scope of the present invention.

Claims (3)

1. A new method for implementing MLS scanning beams, comprising the steps of:
(1) establishing a mathematical model of the scanning beam:
Figure FDA0003348590610000011
wherein, U (x) represents the mathematical model of the scanning beam, x represents the radian of the mathematical model of the scanning beam, and x has the value range of [ -pi, pi [ -pi [ ]]，e(.)Denotes the exponential operation with the natural constant e as base, K and b0All are constants, and when a specific value is taken, the-3 dB point of the scanning beam is half of the width of the scanning beam;
(2) constructing an argument value of a scanning beam;
the independent variable in the mathematical model of the scanning beam is an arc value and is set as
Figure FDA0003348590610000018
The function period is [ -pi, pi [ -pi [ ]](ii) a Setting the scanning beam time period as T, wherein the 0 moment corresponds to-pi, and the T moment corresponds to pi; let a beam width be Δ T, then a beam width arc value be
Figure FDA0003348590610000012
Argument x of scanning beam with start time 00Should be that
Figure FDA0003348590610000013
Wherein
Figure FDA0003348590610000014
Scanning beam self-encoding value x at any timenIs composed of
Figure FDA0003348590610000015
After finishing, the product is obtained
Figure FDA0003348590610000016
Wherein
Figure FDA0003348590610000017
t is the starting moment when the scanning beam appears;
(3) obtaining scanning beam values
The scanning beam at any time is subjected to an argument xnThe mathematical model of the scanning beam is substituted to obtain the scanning beam value at any time, as follows:
Figure FDA0003348590610000021
adjusting k and b in the above formula0Value, when k is 1.12, b01/3, the requirement of the international civil aviation convention on the MLS scanning beam-3 dB point width is met;
(4) acquiring specific parameter values in various microwave landing signals;
1) orientation signal
a. The lead code time slot is distributed to be 0-1.600 milliseconds, and mainly comprises a reference time code and a function identification code;
b. the time slot allocation of the sector signal is 1.600 ms to 2.432 ms; three OCI pulses are required to be generated by a sector signal, wherein the three OCI pulses are a left outer OCI, a right outer OCI and a rear OCI pulse respectively, and each OCI pulse occupies a 128 microsecond time slot; simultaneously generating a 1-bit DPSK ground identification code and a 6-bit DPSK modulated airborne antenna selection pulse;
c the scanning signal time slot is allocated to 2.432 to 15.900 milliseconds; the scanning signal needs to generate amplitude-modulated forward and backward test pulses, and between the two test pulses, the scanning beam value obtained in the step (3) is applied to generate a forward scanning beam in a time slot from 2.560 milliseconds to 8.760 milliseconds and generate a backward scanning beam in a time slot from 9.360 milliseconds to 15.560 milliseconds;
2) pitch signal
a. The same direction signal is consistent, the lead code time slot is distributed to be 0 to 1.600 milliseconds, and the lead code time slot mainly comprises a reference time code and a function identification code;
b. sector signal time slot allocation is 1.728 milliseconds to 1.856 milliseconds; in the sector signal, only one kind of OCI signal is generated, and the OCI pulse occupies a 128 microsecond time slot;
c the scanning signal time slot is distributed to 1.856 milliseconds to 5.600 milliseconds; applying the scan beam values obtained in step (3), generating a forward scan beam in a 1.856-3.406 ms time slot, and generating a backward scan beam in a 3.806-5.356 ms time slot;
3) high speed azimuth signal
a. The high-speed azimuth signal is similar to the azimuth signal, the lead code time slot is distributed to be the first 1.600 milliseconds, and the lead code time slot mainly comprises a reference time code and a function identification code;
b. the time slot allocation of the sector signals is 1.600-2.432 milliseconds, and is consistent with the allocation of the azimuth signals;
c. applying the scanning beam values obtained in the step (3), wherein the scanning signal time slot is allocated to 2.432 milliseconds to 11.900 milliseconds, the forward scanning beam is generated in the time slot of 2.560 milliseconds to 6.760 milliseconds, and the return scanning beam is generated in the time slot of 7.360 milliseconds to 11.560 milliseconds;
4) flattening signals
a. Similar to the direction signal, the lead code time slot is allocated to be the first 1.600 milliseconds and mainly comprises a reference time code and a function identification code;
b, no sector signal is generated, and the time slot of the scanning signal is distributed to 1.600 milliseconds to 5.300 milliseconds; generating a scanning signal which only comprises a forward scanning signal and a backward scanning signal, applying the scanning beam value acquired in the step (3), generating a forward scanning beam in a time slot of 1.856-3.056 milliseconds, and generating a backward scanning beam in a time slot of 3.856-5.056 milliseconds;
5) anti-azimuth signal
a. Similar to the direction signal, the lead code time slot is allocated to be the first 1.600 milliseconds and mainly comprises a reference time code and a function identification code;
b. sector signal time slot allocation is 1.600 ms to 2.432 ms;
c. applying the scan beam values obtained in step (3), generating a forward scan beam in a time slot of 2.560 ms to 6.760 ms, and generating a backward scan beam in a time slot of 7.360 ms to 11.560 ms;
6) basic data word
a. The lead code time slot of the basic data word is distributed to be the first 1.600 milliseconds; generating a function identification code of 7-bit DPSK modulation;
b. different from azimuth signals, basic data word signals only comprise basic data signals modulated by 20-bit DPSK, time slot distribution is 1.600-3.100 milliseconds, the first 18 bits are information bits, and the second 2 bits are parity check bits;
7) auxiliary data word signal
a. The auxiliary data word preamble time slot is allocated to the first 1.600 milliseconds; the method comprises the steps of containing a 7-bit DPSK modulation function identification code;
b. the auxiliary data signal time slot is allocated between 1.600 milliseconds and 5.900 milliseconds; generating a 64-bit DPSK modulated auxiliary data signal;
(5) generating various microwave landing signals;
according to the time slot allocation format of the microwave landing signal in the step (4), a time division multiplexing method is adopted, and a receiver reference time code, a function identification code, a station identification code, an antenna selection pulse, an OCI rear signal, an OCI left signal, an OCI right signal, a forward check pulse, a backward check pulse, tail protection time, a forward scanning signal and a backward scanning signal are jointly synthesized into a microwave landing azimuth signal, a pitching signal, a high-speed azimuth signal, a leveling signal, a reverse azimuth signal, a basic data word signal and an auxiliary data word signal with complete functions;
(6) selecting a desired microwave landing signal
Selecting a required microwave landing signal according to the function identification code of each microwave landing signal;
(7) generating a microwave landing sequence;
performing time sequence control on the selected microwave landing signals by adopting a time division multiplexing method to generate a microwave landing sequence 1 and a microwave landing sequence 2;
(8) generating a full-period microwave landing signal;
arranging time slots of the sequence 1 and the sequence 2 by adopting a time division multiplexing method, wherein the time slot intervals among the sequences are respectively 1ms, 13ms, 19ms, 2ms, 20ms, 6ms and 0ms, and generating microwave landing full-period digital baseband signals; the duration of the full-period signal is not more than 615ms, and the interval of each full-period signal is 18 ms.
2. The method of claim 1 further comprising the steps of: (9) and (3) performing simulation verification on the GNUradio software high-speed full-period functional sequence digital baseband signal.
3. The method of claim 2 further comprising the steps of: (10) HackRF one hardware test.
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