A method of measuring an antenna directivity coefficient

Abstract

The application discloses a method for measuring antenna directivity coefficient. The method comprises the following steps: firstly, measuring the carrier power received by the antenna to be measured by using outdoor far field method; then, closing the radio frequency output of the signal source, rotating the antenna to be measured to zenith direction, sequentially placing the antenna to be measured into normal temperature load noise environment and zenith clear sky noise environment, and measuring the normalized noise power output by the system; then, calculating the normalized carrier-to-noise ratio according to the measured carrier power and the normalized noise power output by the system; finally, calculating the antenna directivity coefficient according to the measured normalized carrier-to-noise ratio. The method is simple and easy to implement, and has popularization and application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of antennas, in particular to a method for measuring antenna directivity coefficient. BACKGROUND

[0002] Antenna directivity coefficient is also called directivity gain, which is defined as the ratio of the radiation intensity of the antenna in the spatial spherical coordinate (θ, φ) direction to the radiation intensity of the ideal point source under the condition of the same radiation power. The antenna directivity coefficient can be understood as a measure of the degree of concentration of electromagnetic wave energy of the antenna, and is one of the core performance indicators of the antenna. Therefore, it is very important to accurately measure the antenna directivity coefficient. The traditional method for measuring the antenna directivity coefficient is to measure the spatial three-dimensional pattern of the antenna and calculate the antenna directivity coefficient by using numerical integration method. The traditional method for measuring the antenna pattern is far-field method. With the development of antenna measurement technology, near-field method and compact range method have also been widely used in antenna pattern measurement. The following limitations exist in determining the antenna directivity coefficient by measuring the antenna pattern:

[0003] 1. In the traditional far-field measurement method, measuring the complete three-dimensional pattern of the antenna requires the establishment of a complex test system, and the measurement efficiency is low. The multiple reflections of the ground and the test environment have a great influence on the far sidelobes of the antenna pattern.

[0004] 2. In the near-field measurement, the planar near-field and the cylindrical near-field cannot measure the complete spatial three-dimensional pattern, and the spherical near-field can measure the complete spatial three-dimensional pattern of the antenna, but the test system is very expensive.

[0005] 3. In the compact range, the principle of measuring the antenna pattern in the compact range is the same as that of the traditional far-field method, and the complete spatial three-dimensional pattern of the antenna is measured. The test system is complex, and the measurement efficiency is low. It is also very expensive to establish a compact range antenna test system. SUMMARY

[0006] The purpose of the present application is to avoid the shortcomings in the background art and to provide a method for measuring the antenna directivity coefficient. The method is simple, convenient and easy to implement, and is suitable for measuring the directivity coefficient of different types of antennas.

[0007] The technical solution adopted by the present application is as follows:

[0008] A method for measuring the directivity coefficient of an antenna, comprising the following steps:

[0009] Step 1: measuring the carrier power received by the antenna to be measured by using outdoor far-field method;

[0010] Step 2, turn off the signal source radio frequency output, rotate the antenna to be measured to the zenith direction, and sequentially place the antenna to be measured in the normal temperature load noise environment and the zenith clear sky noise environment, respectively measure the normalized noise power output by the system, and calculate the normalized carrier-to-noise ratio respectively;

[0011] Step 3, calculate the antenna directivity coefficient from the normalized carrier-to-noise ratio.

[0012] Further, the specific manner of step 1 is:

[0013] Under the far field condition, align the standard gain horn with the antenna to be measured, and match the polarization, measure the system carrier power with the spectrum analyzer, and use C to represent, the unit is dBm.

[0014] Further, the specific manner of step 2 is:

[0015] Turn off the radio frequency output of the signal source, rotate the antenna to be measured to the zenith direction, and place it in the normal temperature load to receive the environmental noise of the normal temperature load, measure the normalized noise power output by the system with the spectrum analyzer, and use N load to represent, the unit is dBm / Hz;

[0016] Then, place the antenna to be measured in the metal reflector, point to the zenith clear sky direction, receive the sky noise, and measure the normalized noise power output by the system with the spectrum analyzer, and use N sky to represent, the unit is dBm / Hz;

[0017] Calculate the normalized carrier-to-noise ratio according to the following formula:

[0018]

[0019]

[0020] In the formula:

[0021] C-the system carrier power measured by the far field method, the unit is dBm;

[0022] C-the system carrier power measured by the far field method, the unit is dBm;

[0023] N load -the normalized noise power output by the system when the antenna to be measured is placed in the normal temperature load, the unit is dBm / Hz;

[0024] -the normalized carrier-to-noise ratio output by the system when the antenna to be measured is placed in the zenith clear sky noise;

[0025] N sky -the normalized noise power output by the system when the antenna to be measured is placed in the zenith clear sky noise, the unit is dBm / Hz.

[0026] Furthermore, the antenna directivity coefficient is calculated in step 3 as follows:

[0027]

[0028] In the formula:

[0029] D – Antenna directivity coefficient, in dBi;

[0030] k – Boltzmann constant, k = 1.38 -23 J / K;

[0031] L p —Free-space propagation loss between a standard gain horn and the antenna under test, in dB;

[0032] G SGH —The gain of a standard gain speaker, measured in dBi;

[0033] P T —The input power of a standard gain speaker, measured in dBW;

[0034] T0—Noise temperature under normal temperature load, in K;

[0035] T sky —Night noise temperature at the zenith, in Kelvin.

[0036] Furthermore, the distance between the antenna under test and the standard gain horn satisfies the far-field test distance condition, that is, the distance R between the antenna under test and the standard gain horn ≥ 2d. 2 / λ, where d is the aperture of the antenna under test and λ is the operating wavelength.

[0037] Furthermore, the metal reflector in the normalized noise power measurement device, used to shield the influence of ground noise, should be large enough to ensure that the antenna under test is installed inside the metal reflector, and the angle subtended by the antenna under test to the edge of the metal reflector should be greater than or equal to one-tenth of the power beamwidth of the antenna under test.

[0038] Furthermore, the carrier power and normalized noise power were measured under clear weather conditions.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. This method measures the directivity of an antenna without requiring the measurement of the antenna's stereo pattern. It only requires measuring the normalized carrier-to-noise ratio of the system output under normal temperature load and clear zenith noise to determine the antenna's directivity, making it simple and convenient.

[0041] 2. This method is suitable for measuring the directivity coefficient of different types of antennas and has good promotion and application value. Attached Figure Description

[0042] Figure 1 This is a block diagram illustrating the principle of carrier power measurement.

[0043] Figure 2 This is a block diagram illustrating the principle of normalized noise power measurement. Detailed Implementation

[0044] A method for measuring the directivity of an antenna is disclosed. The test system consists of a signal source, a standard gain horn, an antenna under test (AUT), a low-noise amplifier, an RF test cable, a room-temperature load, a metallic reflector, and a spectrum analyzer. The method first measures the carrier power received by the antenna using an outdoor far-field method. Then, the RF output of the signal source is turned off, and the AUT is rotated to the zenith direction. The AUT is then placed in both a room-temperature load noise environment and a zenith clear-sky noise environment, and the normalized noise power output by the system is measured and the normalized carrier-to-noise ratio (CNR) is calculated. Finally, the antenna directivity is calculated from the CNR.

[0045] In one specific embodiment, the antenna under test is a planar array antenna with an operating frequency range of 3.4 GHz to 4.2 GHz and linear polarization. The standard gain horn is C-band, with a gain of 19.5 dBi at 4 GHz; the low-noise amplifier is C-band; during testing, the input power of the standard gain horn is -40 dBW, and the free-space propagation loss between the antenna under test and the standard gain horn is 64.5 dB; the noise temperature under normal temperature load is 300 K, and the clear-sky noise temperature at 4 GHz is 5 K in the zenith direction. The measurement process is as follows:

[0046] In the outdoor antenna far-field test field, a standard gain horn and the antenna under test are installed. The distance between the standard gain horn and the antenna under test must meet the far-field test distance conditions, and the axes must be aligned and the polarization matched.

[0047] The signal source transmits a single-carrier radio frequency signal, which is transmitted through the radio frequency test cable, emitted by a standard gain horn, propagates in free space, is received by the antenna under test, amplified by a low-noise amplifier, and the power of the carrier signal is measured using the code marking function of a spectrum analyzer.

[0048] Then, turn off the RF output of the signal source, point the antenna under test towards the zenith, place it in the ambient temperature load noise, receive the blackbody radiation noise of the microwave absorbing material, set the RF input attenuation of the spectrum analyzer to 0dB, and use the code noise measurement function of the spectrum analyzer to measure the normalized noise power output by the system after the ambient temperature load noise received by the antenna under test is amplified by the low noise amplifier.

[0049] Next, the antenna under test was placed in the metal reflector, pointed towards the clear sky at the zenith, and received sky noise. The normalized noise power output by the system was measured using a spectrum analyzer.

[0050] Finally, the normalized carrier-to-noise ratio is calculated based on the carrier power and the normalized noise power of the system output, and the antenna directivity coefficient is then calculated.

[0051] In another embodiment, the specific steps of the method are as follows:

[0052] Step 1: Normalized carrier-to-noise ratio measurement. For example... Figure 1 As shown, under far-field conditions, the standard gain horn is aligned with the antenna under test, polarization matched, and the system carrier power is measured using a spectrum analyzer, denoted by C, in dBm; then, as... Figure 2 As shown, the RF output of the signal source is turned off, the antenna under test is rotated to the zenith direction, placed in a room-temperature load, and the ambient noise of the room-temperature load is received. The normalized noise power of the system output is measured using a spectrum analyzer, and N is used as the reference. load The unit is dBm / Hz; finally, the antenna under test is placed in a metal reflector, pointed towards the clear sky at the zenith, and sky noise is received. The normalized noise power output by the system is measured using a spectrum analyzer, and N is used as the unit. sky The value is expressed in dBm / Hz. The normalized carrier-to-noise ratio of the system output is calculated using the following formula.

[0053]

[0054]

[0055] In this embodiment, the antenna under test (DUT) is aligned with a standard gain horn and polarization matched. The carrier power measured by a spectrum analyzer is +20.5 dBm. With the RF output of the signal source turned off, the DUT is rotated to the zenith direction and placed in a room-temperature load. The normalized noise power of the system output measured by the spectrum analyzer is -125.7 dBm / Hz. With the room-temperature load removed, the DUT is placed in a metal reflector, pointing towards the clear zenith, and receives sky noise. The normalized noise power of the system output measured by the spectrum analyzer is -133.6 dBm / Hz. The normalized carrier-to-noise ratio (CNR) of the system output is calculated using the following formula:

[0056]

[0057]

[0058] Step 2: Calculation of antenna directivity. The antenna directivity is calculated using the normalized carrier-to-noise ratio of the system output, obtained by placing the antenna under test in both normal temperature load and clear sky noise environments, using the following formula.

[0059]

[0060] In this embodiment, the antenna directivity is calculated by measuring the normalized carrier-to-noise ratio of the system output when the antenna under test is placed in both a normal temperature load environment and a clear zenith noise environment.

[0061]

[0062] The working principle of this invention is as follows:

[0063] The method first uses the outdoor far-field method to measure the carrier power received by the antenna under test; then, the RF output of the signal source is turned off, the antenna under test is rotated to the zenith direction, and the antenna under test is placed in a normal temperature load noise environment and a zenith clear sky noise environment in turn, and the normalized noise power output by the system is measured respectively; next, the normalized carrier-to-noise ratio is calculated from the measured carrier power and the normalized noise power output by the system; finally, the antenna directivity coefficient is calculated from the measured normalized carrier-to-noise ratio.

[0064] In summary, this method is simple, convenient, easy to implement, suitable for measuring the directivity coefficient of different types of antennas, and has good potential for widespread application.

Claims

1. A method for measuring the directivity coefficient of an antenna, characterized in that, Includes the following steps: Step 1: Measure the carrier power received by the antenna under test using the outdoor far-field method; Step 2: Turn off the RF output of the signal source, rotate the antenna under test to the zenith direction, and place the antenna under test in a normal temperature load noise environment and a zenith clear sky noise environment in turn. Measure the normalized noise power of the system output in each environment, and calculate the normalized carrier-to-noise ratio in each environment. In the formula: —The normalized carrier-to-noise ratio of the system output when the antenna under test is placed in a normal temperature load; C – System carrier power measured by the far-field method, in dBm; N load —The normalized noise power output by the system when the antenna under test is placed in a normal temperature load, in dBm / Hz; —The normalized carrier-to-noise ratio of the system output when the antenna under test is placed in clear sky noise at the zenith; N sky —The normalized noise power output by the system when the antenna under test is placed in clear sky noise at the zenith is expressed in dBm / Hz. Step 3: Calculate the antenna directivity coefficient from the normalized carrier-to-noise ratio: In the formula: D – Antenna directivity coefficient, in dBi; k – Boltzmann constant, k = 1.38 -23 J / K; L p —Free-space propagation loss between a standard gain horn and the antenna under test, in dB; G SGH —The gain of a standard gain speaker is measured in dBi; P T —The input power of a standard gain speaker, measured in dBW; T0—Noise temperature under normal temperature load, in K; T sky —Night noise temperature at the zenith, in Kelvin.

2. The method for measuring the directivity coefficient of an antenna according to claim 1, characterized in that, The specific method for step 1 is as follows: Under far-field conditions, align the standard gain horn with the antenna under test and perform polarization matching. Use a spectrum analyzer to measure the system carrier power, denoted by C, in dBm.

3. The method for measuring the directivity coefficient of an antenna according to claim 2, characterized in that, The specific method for step 2 is as follows: Turn off the RF output of the signal source, rotate the antenna under test to the zenith direction, place it in a room-temperature load, receive the ambient noise of the room-temperature load, and measure the normalized noise power of the system output using a spectrum analyzer. Use N... load It indicates that the unit is dBm / Hz; Then, the antenna under test was placed in the metal reflector, pointed towards the clear sky at the zenith, and received sky noise. The normalized noise power output by the system was measured using a spectrum analyzer, and N was used as the reference. sky It indicates that the unit is dBm / Hz.

4. The method for measuring the directivity coefficient of an antenna according to claim 2, characterized in that, The distance between the antenna under test and the standard gain horn satisfies the far-field test distance condition, i.e., the distance R between the antenna under test and the standard gain horn ≥ 2d. 2 / λ, where d is the aperture of the antenna under test and λ is the operating wavelength.

5. The method for measuring the directivity coefficient of an antenna according to claim 3, characterized in that, The metal reflector in the normalized noise power measurement device is used to shield the influence of ground noise. Its size should be large enough to ensure that the antenna under test is installed inside the metal reflector, and the angle subtended by the antenna under test to the edge of the metal reflector should be greater than or equal to one-tenth of the power beamwidth of the antenna under test.

6. The method for measuring the directivity coefficient of an antenna according to claim 1, characterized in that, The carrier power and normalized noise power were measured under clear weather conditions.

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