A constant modulus constrained multicarrier direction finding method

Abstract

The present application belongs to the field of electronic information technology, and particularly relates to a constant modulus constrained multi-carrier direction finding method. The problem to be solved by the present application is how to determine the direction of departure by using the carrier frequency and amplitude of the signal transmitted by the transmitting antenna and the constant modulus constraint of the carrier of the signal received by the single receiving antenna in the case that the single receiving antenna receives the multi-carrier signals synchronously transmitted by two transmitting antennas. The method provided by the present application can realize the direction finding of departure by only using the single receiving antenna to receive the multi-carrier signals synchronously transmitted by two transmitting antennas, which can not only reduce the volume and weight of the receiving end, and the complexity of the receiving end and the maintenance cost of different application occasions, but also improve the portability of the positioning terminal.

Description

Technical Field

[0001] This invention belongs to the field of electronic information technology, and specifically relates to a constant mode constrained multi-carrier off-wave direction finding method. Background Technology

[0002] Radio positioning and navigation often relies on global satellite positioning systems such as GPS and BeiDou. However, in complex geographical environments such as indoor environments with obstructions or densely built-up urban areas, satellite signal reception conditions and positioning accuracy often fail to meet the application requirements of navigation. In order to avoid dependence on global satellite positioning systems, it is necessary to develop local autonomous positioning and navigation technologies to meet the navigation needs of the growing Internet of Things (IoT) and vehicle-to-everything (V2X) applications in indoor and urban environments.

[0003] Among various radio positioning technologies, radio direction finding is a mature and frequently used positioning parameter measurement technique in positioning systems. However, the direction of the radio signal measured is mainly the direction of arrival (DOA), which typically requires an array of multiple antennas to receive the radio signal. The installation and calibration of the antenna array for receiving the signal are complex, and the power consumption and cost are high, limiting the application of this positioning technology that utilizes DOA measurement. Therefore, it is necessary to develop a method that uses only a single antenna to receive radio signals and obtain directional information.

[0004] Compared to arrival wave direction finding, which requires an array of antennas to receive signals, off-wave direction finding only requires a single antenna to receive radio signals and achieve the direction measurement needed for positioning. This reduces the size and weight of the radio signal receiver, improving portability. Furthermore, since the radio signal receiver only needs a single antenna, channel correction is eliminated, thus reducing not only the complexity of the radio signal receiver but also the cost of use in various environments.

[0005] In the problem of azimuth measurement using radio signals, it is theoretically impossible to complete the measurement if one omnidirectional transmitting antenna transmits the radio signal and another omnidirectional receiving antenna receives the signal. However, if two omnidirectional transmitting antennas transmit radio signals simultaneously, and the signal received by the other omnidirectional receiving antenna is an overlap of the radio signals transmitted by both antennas, it is possible to determine the direction of the radio signal as it leaves the two transmitting antennas, i.e., the departure direction, through specific signal processing. Summary of the Invention

[0006] The problem to be solved by this invention is how to determine the departure direction by using the carrier frequency and amplitude of the transmitted signal from the transmitting antenna and the constant mode constraint of the received signal from the single receiving antenna when a single receiving antenna receives a multi-carrier signal transmitted synchronously by two transmitting antennas.

[0007] The technical solution of this invention is as follows:

[0008] A constant-mode-constrained multi-carrier off-wave direction finding method is defined as follows: one antenna receives multi-carrier signals simultaneously transmitted by two transmitting antennas. The distance between the two transmitting antennas is d, the number of carriers in the transmitted signal is N, and the frequency of the nth carrier is f. n The amplitude of the nth carrier wave of the signal transmitted by the first transmitting antenna is α. n The amplitude of the nth carrier wave of the signal transmitted by the second transmitting antenna is β. n n = 1, 2, ..., N; the number of digital signal samples input to the digital-to-analog converters of the two transmitting antennas is K, and the digital-to-analog conversion rate is f. st The analog-to-digital conversion rate of the signal received by the receiving antenna is f. sr The number of wave-departure directions searched is M, θ m Let m be the wave-departing direction for the m-th search, where m = 1, 2, ..., M, and the search sequence for wave-departing directions is {θ1, θ2, ..., θ...}. M The method for determining the direction of departure from the wave is characterized by the following steps:

[0009] S1. Define the digitally transmitted signal of the first transmitting antenna as (the digital-to-analog converter according to the digital-to-analog conversion rate f). st The input digital signal sample is:

[0010]

[0011] The digital transmission signal of the second transmitting antenna is (the digital-to-analog converter operates at a digital-to-analog conversion rate f). st The input digital signal sample is:

[0012]

[0013] Where k = 0, 1, 2, ..., K-1;

[0014] S2. Define the digital received signal of the receiving antenna as (the analog-to-digital converter according to the analog-to-digital conversion rate f). sr The sampled digital received signal is x(t), where t = 0, 1, 2, ..., K-1;

[0015] S3, the frequency f of the digitally received signal x(t) and the nth carrier. n The complex amplitude of the nth carrier of the received signal is determined as follows:

[0016]

[0017] Where n = 1, 2, ..., N;

[0018] S4, by α n βn , and y(f n ), the mth departure direction θ m of the search is determined as follows:

[0019]

[0020] S5, the constant modulus sequence {z(1, θ m ), z(2, θ m ), …, z(N, θ m )} of the mth departure direction θ m of the search is determined as follows: m

[0021]

[0022] wherein m = 1, 2, …, M; and the spectral value of the mth departure direction θ m of the search is determined as follows:

[0023]

[0024] wherein m = 1, 2, …, M;

[0025] S6, the minimum value g(θ p ) in the spectral value sequence {g(θ1), g(θ2), …, g(θ M )} of the search is determined, and the departure direction finding is θ p .

[0026] The present application has the advantages that: using the method provided by the present application, the departure direction finding can be realized by receiving the multi-carrier signals transmitted by two transmitting antennas simultaneously with a single receiving antenna, which can reduce the volume and weight of the receiving end, reduce the complexity of the receiving end and the maintenance cost of different application scenarios, and improve the portability of the positioning terminal. DETAILED DESCRIPTION

[0027] The practicability of the present application is analyzed below in combination with an embodiment.

[0028] Embodiment

[0029] In this example, the distance between the two radio transmitting antennas is half a wavelength, i.e. d = 0.5, the number of the carrier of the transmitted signal is N = 121, the frequency of the nth carrier is f n = -600 + 10(n-1) kHz, the amplitude of the nth carrier of the first transmitting antenna is α n = e j2π(n-1) / 121 , and the amplitude of the nth carrier of the second transmitting antenna is β​n =1, n=1, 2, …, N; the sampling number of the input signal of the digital-to-analog converter is K=3000, and the rate of the digital-to-analog conversion and the analog-to-digital conversion is 3MHz; the actual departure direction is a random number uniformly distributed between 25 degrees and 26 degrees, and the search sequence of the departure direction is {θ m =21+0.01(m-1)} degrees, m=1, 2, …, M, and M=901.

[0030] In the case that the ratio of the carrier power of the signal received by the receiving antenna to the noise power spectral density is 24dB, 2000 independent experiments are conducted. The statistical result shows that the standard deviation of the measured departure direction is 0.3673 degrees by using the method.

[0031] It can be seen that the application provides a constant modulus constrained multi-carrier departure direction finding method, a single receiving antenna is used to receive the multi-carrier signals synchronously transmitted by two transmitting antennas, the carrier frequency and amplitude of the signal transmitted by the transmitting antenna and the constant modulus constraint of the carrier of the signal received by the single receiving antenna are used, and the purpose of measuring the departure direction is achieved.

Claims

1. A constant-mode-constrained multi-carrier off-wave direction finding method, defined as using one antenna to receive multi-carrier signals simultaneously transmitted by two transmitting antennas, the distance between the two transmitting antennas being d, the number of carriers in the transmitted signal being N, and the frequency of the nth carrier being f. n The amplitude of the nth carrier wave of the signal transmitted by the first transmitting antenna is α. n The amplitude of the nth carrier wave of the signal transmitted by the second transmitting antenna is β. n n = 1, 2, ..., N; the number of digital signal samples input to the digital-to-analog converters of the two transmitting antennas is K, and the digital-to-analog conversion rate is f. st The analog-to-digital conversion rate of the signal received by the receiving antenna is f. sr The number of wave-departure directions searched is M, θ m Let m be the wave-leaving direction for the m-th search, where m = 1, 2, ..., M, and the search sequence for wave-leaving directions is {θ1, θ2, ..., θ...}. M }; characterized in that, The direction finding method includes the following steps: S1. Define the digitally transmitted signal of the first transmitting antenna as: Where k = 0, 1, 2, ..., K-1; the digital transmission signal of the second transmitting antenna is: S2. Define the digital received signal of the receiving antenna as x(t); S3, the frequency f of the digitally received signal x(t) and the nth carrier. n The complex amplitude of the nth carrier of the received signal is determined as follows: S4, by α n β n 、 and y(f n Determine the m-th off-wave direction θ of the search. m The value of the nth constant modulus sequence is: S5, from the m-th wave departure direction θ m The constant modulus sequence {z(1, θ)} m ), z(2, θ m ), ..., z(N, θ m Determine the m-th off-wave direction θ of the search. m The average modulus of the constant modulus sequence is: Therefore, by utilizing constant mode constraints, the m-th departure direction θ of the search can be determined. m The spectral value is: S6. Determine the sequence of off-wave direction spectral values ​​to be searched {g(θ1), g(θ2), ..., g(θ)}. M The minimum value in )} is g(θ) p Thus, the θ corresponding to the out-of-wave direction finding is obtained. p .

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