A method for measuring antenna loss

Abstract

The invention discloses a method for measuring antenna loss, belonging to the field of antenna technology. The invention firstly measures the normalized carrier-to-noise ratio of the antenna system by using the far-field method under the condition of a microwave darkroom environment; then measures the power radiation pattern of the E-plane and the H-plane of the antenna by using the far-field method, and calculates the directivity coefficient of the antenna by using the numerical integration method; finally, the loss of the antenna is calculated based on the measured normalized carrier-to-noise ratio of the antenna system and the antenna directivity coefficient. The method of the invention is simple and feasible, and has the value of promotion and application.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a method for measuring antenna loss. Background Art

[0002] Antenna loss is defined as the ratio of antenna radiated power to input power. It is an important performance parameter of the antenna. Antenna loss not only reduces antenna gain or efficiency, but also increases system noise temperature, affecting the sensitivity of the receiving system. It is important to accurately measure antenna loss. Antenna loss is usually measured by the short-circuit method or the gain directivity method. The short-circuit method is to short-circuit the antenna and determine the antenna loss by measuring the reflection loss; the gain directivity method is to determine the antenna loss by measuring the antenna power gain and directivity coefficient. The traditional measurement method for determining antenna loss has the following limitations:

[0003] 1. In the traditional short-circuit method, the measurement method is suitable for measuring the loss of horn or aperture antennas. For linear antennas such as vibrators, antenna arrays, and microstrip antennas, it is impossible to short-circuit the antenna surface, so this method is not suitable for measuring the loss of such antennas.

[0004] 2. In the traditional short-circuit method, the antenna surface is short-circuited, and the measurement error caused by multiple reflections is large;

[0005] 3. In the traditional gain directivity method, it is necessary to measure the antenna power gain and directivity coefficient. Due to the limitation of the measurement accuracy of the antenna power gain, this method is not suitable for the measurement of small-loss antennas. Summary of the invention

[0006] The purpose of the present invention is to avoid the shortcomings of the above-mentioned background technology and propose a method for measuring antenna loss. The method does not need to short-circuit the antenna aperture, does not need to measure the power gain of the antenna, overcomes the influence of multiple reflections of the traditional short-circuit method, eliminates common error terms, and improves measurement accuracy.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for measuring antenna loss comprises the following steps:

[0009] (1) Measurement of the normalized carrier-to-noise ratio of the system: In the far field of a microwave darkroom, align the standard gain horn with the antenna to be tested and perform polarization matching. Use a spectrum analyzer to measure the carrier power received by the antenna to be tested, represented by C in dBm. Then turn off the RF output of the signal source, rotate the antenna to be tested 90°, and point it toward the absorbing material on the side wall of the microwave darkroom to receive the ambient noise of the microwave darkroom. Use a spectrum analyzer to measure the normalized noise power of the system, represented by N0 in dBm / Hz. Calculate the normalized carrier-to-noise ratio of the system in decibels:

[0010]

[0011] Where:

[0012] ——System normalized carrier-to-noise ratio, dB / Hz;

[0013] C - the total carrier power received by the antenna under test, dBm;

[0014] N0 - system normalized noise power, dBm / Hz;

[0015] (2) Measurement of the directivity coefficient of the antenna under test: Under the far-field conditions of a microwave darkroom, measure the E-plane power pattern P of the antenna under test within the angle range of ±180°. E (θ) and H-plane power pattern P H (θ); use the following formula to calculate the directivity coefficient of the antenna:

[0016]

[0017]

[0018]

[0019] Where:

[0020] D E ——Antenna E-plane directivity coefficient;

[0021] D H ——Antenna H-plane directivity coefficient;

[0022] D – antenna directivity coefficient, dBi;

[0023] (3) Calculation of antenna loss: The antenna loss is calculated using the following formula based on the measured system normalized carrier-to-noise ratio and antenna directivity coefficient:

[0024]

[0025] Where:

[0026] L ant —antenna loss, dB;

[0027] G S —Gain of standard gain speaker, dBi;

[0028] P T —Input power of standard gain speaker, dBW;

[0029] L p—Free space propagation loss between the standard gain horn and the antenna under test, dB;

[0030] T0—ambient noise temperature of microwave darkroom, K;

[0031] T LNA —Noise temperature of the low noise amplifier, K;

[0032] Complete the antenna loss measurement.

[0033] Furthermore, the specific method of step (1) is:

[0034] A far-field test system is established in a microwave darkroom, and a standard gain horn and an antenna to be tested are installed. The distance between the standard gain horn and the antenna to be tested meets the antenna far-field test distance condition. The antenna axis is aligned and polarization matching is performed.

[0035] The single carrier signal emitted by the signal source is transmitted through the RF cable, emitted by the standard gain speaker, propagated through free space, received by the antenna under test, amplified by the low noise amplifier, and the power of the carrier signal received by the antenna under test is measured using the code engraving function of the spectrum analyzer;

[0036] Then, turn off the RF output of the signal source, rotate the antenna to be tested by 90°, and point the main beam of the antenna to be tested to the absorbing material on the side wall of the microwave darkroom. In this way, the antenna to be tested is in the room temperature environment of the microwave darkroom and receives the environmental noise of the microwave darkroom. Set the RF input attenuation of the spectrum analyzer to 0dB, and use the code noise function of the spectrum analyzer to measure the normalized noise power of the system after the environmental noise received by the antenna to be tested is amplified by the low-noise amplifier;

[0037] The system normalized carrier-to-noise ratio is calculated based on the measured carrier power and system normalized noise power.

[0038] Furthermore, the specific method of step (2) is:

[0039] Drive the antenna to be tested to align with the axis of the standard gain horn, set the polarization of the standard gain horn to horizontal polarization, adjust the polarization matching between the antenna to be tested and the standard gain horn, drive the azimuth of the antenna to be tested, and measure the azimuth power pattern of the antenna to be tested within the range of ±180°, so as to obtain the E-plane power pattern of the antenna to be tested;

[0040] Then, the antenna to be tested is adjusted to align with the standard gain horn, the polarization of the standard gain horn is set to vertical polarization, the polarization matching of the antenna to be tested and the standard gain horn is adjusted, and the azimuth power pattern of the antenna to be tested is measured within the range of ±180°, so as to obtain the H-plane power pattern of the antenna to be tested;

[0041] The directivity coefficient of the antenna under test is calculated using the numerical integration method based on the measured E-plane and H-plane power patterns of the antenna under test.

[0042] Furthermore, the distance between the antenna to be tested and the standard gain horn meets the far-field test distance condition, that is, the distance between the antenna to be tested and the standard gain horn R ≥ 2d 2 / λ, where d is the aperture of the antenna to be tested and λ is the operating wavelength.

[0043] Furthermore, the gain of the standard gain speaker and the noise temperature of the low noise amplifier are precisely known.

[0044] Compared with the background technology, the present invention has the following advantages:

[0045] 1. This method measures antenna loss without short-circuiting the antenna surface, overcoming the influence of multiple reflections in the traditional short-circuit method.

[0046] 2. This method measures antenna loss without measuring the power gain of the antenna. By measuring the system-normalized carrier-to-noise ratio, the common error term is eliminated and the measurement accuracy is improved.

[0047] 3. This method is suitable for measuring different types of antenna loss and has good promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the measurement principle of the present invention. DETAILED DESCRIPTION

[0049] A method for measuring antenna loss, the specific steps are as follows:

[0050] (1) Measurement of the normalized carrier-to-noise ratio of the system. Under the far-field conditions of a microwave darkroom, align the standard gain horn with the antenna to be tested, and match the polarization. Use a spectrum analyzer to measure the carrier power received by the antenna to be tested, represented by C, in dBm. Then turn off the RF output of the signal source, rotate the antenna to be tested 90°, point it at the absorbing material on the side wall of the microwave darkroom, receive the ambient noise of the microwave darkroom, and use a spectrum analyzer to measure the normalized noise power of the system, represented by N0, in dBm / Hz. The following formula is used to calculate the normalized carrier-to-noise ratio of the system in decibels.

[0051]

[0052] Where:

[0053] ——System normalized carrier-to-noise ratio, dB / Hz;

[0054] C - the total carrier power received by the antenna under test, dBm;

[0055] N0 - System normalized noise power, dBm / Hz.

[0056] (2) Measurement of the directivity coefficient of the antenna under test. Under the far-field condition of the microwave darkroom, measure the E-plane power pattern and H-plane power pattern of the antenna under test within the angle range of ±180°. The E-plane power pattern is expressed as P E (θ) represents the H-plane power pattern, and P H (θ). Use the following formula to calculate the directivity coefficient of the antenna.

[0057]

[0058]

[0059]

[0060] Where:

[0061] D E ——Antenna E-plane directivity coefficient;

[0062] D H ——Antenna H-plane directivity coefficient;

[0063] D – Antenna directivity coefficient, dBi.

[0064] (3) Calculate antenna loss. The antenna loss is calculated using the following formula based on the measured system normalized carrier-to-noise ratio and antenna directivity coefficient.

[0065]

[0066] Where:

[0067] L ant —antenna loss, dB;

[0068] G S —Gain of standard gain speaker, dBi;

[0069] P T —Input power of standard gain speaker, dBW;

[0070] L p —Free space propagation loss between the standard gain horn and the antenna under test, dB;

[0071] T0—ambient noise temperature of microwave darkroom, K;

[0072] T LNA —Noise temperature of the low noise amplifier, K;

[0073] Complete the antenna loss measurement.

[0074] Specifically, the method for measuring the system normalized carrier-to-noise ratio in step (1) is:

[0075] A far-field test system is established in a microwave darkroom, and a standard gain horn and an antenna to be tested are installed. The distance between the standard gain horn and the antenna to be tested is required to meet the antenna far-field test distance condition, the antenna axis is aligned, and the polarization is matched. The single carrier signal emitted by the signal source is transmitted through the RF cable, emitted by the standard gain horn, propagated through free space, received by the antenna to be tested, amplified by a low-noise amplifier, and the power of the carrier signal received by the antenna to be tested is measured using the code-engraving function of the spectrum analyzer; then, the RF output of the signal source is turned off, the azimuth of the antenna to be tested is rotated 90°, and the main beam of the antenna to be tested points to the absorbing material on the side wall of the microwave darkroom, so that the antenna to be tested is in the room temperature environment of the microwave darkroom and receives the ambient noise of the microwave darkroom. The RF input attenuation of the spectrum analyzer is set to 0dB, and the code-engraving noise function of the spectrum analyzer is used to measure the normalized noise power of the system after the ambient noise received by the antenna to be tested is amplified by the low-noise amplifier. The size of the normalized carrier-to-noise ratio of the system is calculated from the measured carrier power and the normalized noise power of the system.

[0076] The method for measuring the antenna directivity coefficient in step (2) is:

[0077] Drive the antenna to be tested to align with the axis of the standard gain horn, set the polarization of the standard gain horn to horizontal polarization, adjust the polarization matching of the antenna to be tested and the standard gain horn, drive the azimuth of the antenna to be tested, measure the azimuth power pattern of the antenna to be tested within the range of ±180°, and obtain the E-plane power pattern of the antenna to be tested; then, adjust the antenna to be tested to align with the standard gain horn, set the polarization of the standard gain horn to vertical polarization, adjust the polarization matching of the antenna to be tested and the standard gain horn, and similarly measure the azimuth power pattern of the antenna to be tested within the range of ±180°, and obtain the H-plane power pattern of the antenna to be tested. The directivity coefficient of the antenna to be tested is calculated using the numerical integration method based on the measured E-plane and H-plane power patterns of the antenna to be tested.

[0078] In this method, the distance between the antenna to be tested and the standard gain horn meets the far-field test distance condition, that is, the distance between the antenna to be tested and the standard gain horn R ≥ 2d 2 / λ, where d is the diameter of the antenna to be tested and λ is the operating wavelength. In addition, the gain of the standard gain horn and the noise temperature of the low noise amplifier should be accurately known.

[0079] Here is a more specific example:

[0080] Reference Figure 1The test system consists of a microwave darkroom, a signal source, a transmitting bracket, a standard gain horn, an antenna to be tested, a turntable, a low noise amplifier, a RF test cable, a turntable servo controller and a spectrum analyzer. In the microwave darkroom environment, the normalized carrier-to-noise ratio of the antenna system is measured using the far-field method; then the power radiation pattern of the E-plane and H-plane of the antenna is measured using the far-field method, and the directivity coefficient of the antenna is calculated using the numerical integration method; finally, the loss of the antenna is calculated based on the measured normalized carrier-to-noise ratio of the antenna system and the antenna directivity coefficient.

[0081] In the specific embodiment, the antenna to be tested is a flat satellite TV receiving antenna, the operating frequency range is 3.4GHz to 4.2GHz, and the antenna polarization is linear polarization. The standard gain horn is C-band, and the gain at a frequency of 4GHz is 19.5dBi; the low noise amplifier is C-band, and the noise temperature at 4GHz is 50K. During the test, the input power of the standard gain horn is -40dBW, the free space propagation loss between the antenna to be tested and the standard gain horn is 64.5dB; the ambient noise temperature of the microwave darkroom is 295K.

[0082] The specific steps of the antenna loss measurement method are as follows:

[0083] Step 1: Measurement of the normalized carrier-to-noise ratio of the system. Under the far-field conditions of the microwave darkroom, align the standard gain horn with the antenna to be tested, and match the polarization. Use a spectrum analyzer to measure the carrier power received by the antenna to be tested, represented by C, in dBm. Then turn off the RF output of the signal source, rotate the antenna to be tested 90°, point it at the absorbing material on the side wall of the microwave darkroom, receive the ambient noise of the microwave darkroom, and use a spectrum analyzer to measure the normalized noise power of the system, represented by N0, in dBm / Hz. Then use the following formula to calculate the normalized carrier-to-noise ratio of the system expressed in decibels.

[0084]

[0085] In the embodiment, the antenna to be tested is aligned with the standard gain horn, polarization matching, and the carrier power received by the antenna to be tested is measured by a spectrum analyzer to be +20.5dBm; the RF output of the signal source is turned off, and the antenna to be tested is pointed to the side wall of the microwave darkroom to receive the ambient noise of the microwave darkroom. The system normalized noise power measured by the spectrum analyzer is -125.7dBm / Hz. The measured system normalized carrier-to-noise ratio is:

[0086]

[0087] Step 2: Measure the directivity coefficient of the antenna under test. Under the far-field condition of the microwave darkroom, measure the E-plane power pattern and H-plane power pattern of the antenna under test within the angle range of ±180°. The E-plane power pattern is expressed as P E (θ) represents the H-plane power pattern, and PH (θ). Use the following formula to calculate the directivity coefficient of the antenna.

[0088]

[0089]

[0090]

[0091] In the embodiment, the E-plane and H-plane directivity coefficients of the antenna are calculated using the numerical integration method based on the measured ±180° E-plane power pattern and H-plane power pattern. The calculated antenna directivity coefficient is:

[0092]

[0093]

[0094]

[0095] Step 3: Calculate antenna loss. Calculate antenna loss using the following formula based on the measured system normalized carrier-to-noise ratio and antenna directivity.

[0096]

[0097] In the embodiment, the measured normalized carrier-to-noise ratio is 141 dB / Hz and the antenna directivity coefficient is 28.5 dBi. The antenna loss is:

[0098] L ant =228.6+28.5+19.5-40-146.2-64.5-10×lg(295+50)=0.52dB

[0099] In summary, the present invention firstly measures the normalized carrier-to-noise ratio of the antenna system by using the far-field method under the microwave darkroom environment; then measures the power radiation pattern of the E-plane and H-plane of the antenna by using the far-field method, and calculates the directivity coefficient of the antenna by using the numerical integration method; finally, the loss of the antenna is calculated by using the measured normalized carrier-to-noise ratio of the antenna system and the antenna directivity coefficient. The method of the present invention is simple and feasible, and has the value of promotion and application.

Claims

1. A method for measuring antenna loss, characterized in that: The following steps are involved: (1) Measurement of the normalized carrier-to-noise ratio of the system: In the far field of a microwave darkroom, align the standard gain horn with the antenna to be tested and perform polarization matching. Use a spectrum analyzer to measure the carrier power received by the antenna to be tested, which is represented by C in dBm. Then turn off the RF output of the signal source, rotate the antenna to be tested 90°, point it at the absorbing material on the side wall of the microwave darkroom, receive the ambient noise of the microwave darkroom, and use a spectrum analyzer to measure the normalized noise power of the system, represented by N0, in dBm / Hz; calculate the normalized carrier-to-noise ratio of the system expressed in decibels: Where: ——System normalized carrier-to-noise ratio, dB / Hz; C - the total carrier power received by the antenna under test, dBm; N0 - system normalized noise power, dBm / Hz; (2) Measurement of the directivity coefficient of the antenna under test: Under the far-field conditions of a microwave darkroom, measure the E-plane power pattern P of the antenna under test within the angle range of ±180°. E (θ) and H-plane power pattern P H (θ); use the following formula to calculate the directivity coefficient of the antenna: Where: D E ——Antenna E-plane directivity coefficient; D H ——Antenna H-plane directivity coefficient; D – antenna directivity coefficient, dBi; (3) Calculation of antenna loss: The antenna loss is calculated using the following formula based on the measured system normalized carrier-to-noise ratio and antenna directivity coefficient: Where: L ant —antenna loss, dB; G S —Gain of standard gain speaker, dBi; P T —Input power of standard gain speaker, dBW; L p —Free space propagation loss between the standard gain horn and the antenna under test, dB; T0—ambient noise temperature of microwave darkroom, K; T LNA —Noise temperature of the low noise amplifier, K; Complete the antenna loss measurement.

2. The method for measuring antenna loss according to claim 1, characterized in that: The specific method of step (1) is: A far-field test system is established in a microwave darkroom, and a standard gain horn and an antenna to be tested are installed. The distance between the standard gain horn and the antenna to be tested meets the antenna far-field test distance condition. The antenna axis is aligned and polarization matching is performed. The single carrier signal emitted by the signal source is transmitted through the RF cable, emitted by the standard gain speaker, propagated through free space, received by the antenna under test, amplified by the low noise amplifier, and the power of the carrier signal received by the antenna under test is measured using the code engraving function of the spectrum analyzer; Then, turn off the RF output of the signal source, rotate the antenna to be tested by 90°, and point the main beam of the antenna to be tested to the absorbing material on the side wall of the microwave darkroom. In this way, the antenna to be tested is in the room temperature environment of the microwave darkroom and receives the environmental noise of the microwave darkroom. Set the RF input attenuation of the spectrum analyzer to 0dB, and use the code noise function of the spectrum analyzer to measure the normalized noise power of the system after the environmental noise received by the antenna to be tested is amplified by the low-noise amplifier; The system normalized carrier-to-noise ratio is calculated based on the measured carrier power and system normalized noise power.

3. The method for measuring antenna loss according to claim 2, characterized in that: The specific method of step (2) is: Drive the antenna to be tested to align with the axis of the standard gain horn, set the polarization of the standard gain horn to horizontal polarization, adjust the polarization matching between the antenna to be tested and the standard gain horn, drive the azimuth of the antenna to be tested, and measure the azimuth power pattern of the antenna to be tested within the range of ±180°, so as to obtain the E-plane power pattern of the antenna to be tested; Then, the antenna to be tested is adjusted to align with the standard gain horn, the polarization of the standard gain horn is set to vertical polarization, the polarization matching of the antenna to be tested and the standard gain horn is adjusted, and the azimuth power pattern of the antenna to be tested is measured within the range of ±180°, so as to obtain the H-plane power pattern of the antenna to be tested; The directivity coefficient of the antenna under test is calculated using the numerical integration method based on the measured E-plane and H-plane power patterns of the antenna under test.

4. The method for measuring antenna loss according to claim 3, characterized in that: The distance between the antenna to be tested and the standard gain horn meets the far-field test distance condition, that is, the distance between the antenna to be tested and the standard gain horn R ≥ 2d 2 / λ, where d is the aperture of the antenna to be tested and λ is the operating wavelength.

5. The method for measuring antenna loss according to claim 4, characterized in that: The gain of the standard gain speaker and the noise temperature of the low noise amplifier are precisely known.

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