This standard applies to special measurements of angular tracking antennas. SJ 2534.12-1987 Antenna Test Method Special Measurements of Angular Tracking Antennas SJ2534.12-1987 Standard Download Decompression Password: www.bzxz.net
This standard applies to special measurements of angular tracking antennas.

Standard of the Ministry of Electronics Industry of the People's Republic of China Antenna Test Method
Special Measurement of Angular Tracking Antenna
This standard applies to special measurements of angular tracking antennas. 1 Overview
1.1 Electric axis, reference axis and pointing error
1.1.1 Electric axis
SJ2534.12-87
The direction determined by a certain electrical parameter of the antenna radiation pattern is called the electric axis. The electric axis is determined relative to a reference direction called the reference axis.
1.1.2 Reference axis
The direction determined by the electric axis, mechanical axis or optical axis is used as the reference for the antenna pointing, and the pointing reference is called the reference axis. 1.1.3 Pointing error
The angular deviation between the electric axis of the antenna and its reference axis is called the pointing error. It is a measured quantity and should be calibrated by measuring the electric axis of the closed-line system with reference to the reference axis. 1.2 Electric axis pointing accuracy
1.2.1 The electric axis pointing accuracy of a single main lobe antenna is usually determined by taking the direction of maximum response or the middle direction between equal response points on both sides of the maximum value as the electric axis direction of an antenna with a single main lobe. The accuracy determined by this method is usually about one-tenth of the half-power beam width. 1.2.2 Electric axis pointing accuracy of angle tracking antenna An angle tracking antenna can be used to obtain higher electric axis pointing accuracy, as shown in Figure 1. The angle tracking antenna has two or more lobe
difference radiation patterns with a minimum or zero value
/beam avoidance 2 or lobe 1
lobe/+lobe 2 sum)
/-lobe 2 (difference)
at a certain moment
. The relationship between the signal received by the tracking antenna and the target angle (a). Lobe radiation pattern of a single pulse or conical scanning (b). Sum and difference radiation pattern of a single pulse
Ministry of Electronics Industry issued on January 6, 1987
implemented on June 1, 1987
SJ2534.12-87
retransmitted beams or lobes. Comparison of these lobes yields a direction in which the amplitude or phase is equal, i.e., the direction of the electrical axis. When the comparison is made sequentially, it is called sequential beam switching, and the amplitude is generally compared. Two examples of sequential beam switching are conical scanning and beam switching. When the comparison is made simultaneously, it is called simultaneous beam switching or single pulse. In this case, the amplitude or phase can be compared. The electrical axis pointing accuracy of the angle tracking antenna is related to the signal-to-noise ratio, which is generally about one-half the power beam width.
2 Conical Scanning Angle Tracking
2.1 Conical Scanning Antenna
The conical scanning antenna uses a single beam so that the axis of the beam forms a conical scan. Figure 1 (a) shows a cross-section of the directional pattern through two opposite extreme positions on the circular path of the beam. 2.2 Fundamental and Harmonic Signals in the Amplitude Modulation Envelope When the target is not on the cross axis determined by the equal voltage points of the two lobes as shown in Figure 1 (a), the signal varies with the beam position, so that during the scanning cycle, the RF voltage received or transmitted by the antenna is amplitude modulated. The envelope of amplitude modulation is a complex signal in which the lowest frequency observed, or fundamental, is the scanning frequency. The modulation degree of the fundamental to the RF voltage is important in the tracking system. Harmonics of the fundamental scanning frequency are caused by the inherent nonlinearity of the scanning process. In theory, the harmonic signal should tend to zero like the fundamental signal on the cross axis. However, in practice, due to the non-ideality of the antenna radiation pattern, such as the unequal beam width of the E-plane and the H-plane, residual harmonic signals will still remain on the axial direction. 2.3 Electric axis and error signal
Fundamental and higher harmonic modulation are usually used to measure the target error, that is, the angular deviation of the target from the electric axis. The electric axis is determined by the zero point of the fundamental modulation (or error signal). The slope and linearity of the error signal related to the target error and the angular range of the error signal to maintain a single polarity are important design indicators of the tracking system. The single polarity determines the angular range within which the antenna system can capture the target. The harmonic components of the modulation envelope are important for the design of the demodulator. 2.4 Measurement of modulation
The modulation characteristics can be measured using a single-pass transmission system (the same system used in ordinary pattern measurements) that uses the square-law characteristics of the detector to simulate the two-pass transmission of normal radar angle tracking. The equipment of the system includes a microwave transmitter, a detector, an amplifier and a waveform analyzer. The transmitter installed in the far field is used to simulate the position of the target. The transmitter can be a square-wave modulated klystron or a pulsed magnetron that modulates the amplitude at an appropriate repetition frequency. In order to measure the fundamental modulation, the detector-amplifier combination should have a substantially flat response in a specified frequency band, the upper and lower sidebands of which are the repetition frequency plus and minus the conical sweep frequency, respectively. The modulation degree is determined by comparing the fundamental and the first sideband of the amplified signal with a waveform analyzer. The first sideband is at the repetition frequency plus or minus the sweep frequency. The modulation degree M is defined as the amplitude of the lower sideband + the amplitude of the upper sideband
the amplitude of the repetition frequency
The upper and lower contraband amplitudes are theoretically equal, but in practice they may differ slightly due to measurement errors. The average value is taken in the above formula.
Before starting the system measurement, the linearity should be checked. The specific method is to insert an RF attenuator before the detector and record the relative output voltage displayed on the waveform analyzer for a given attenuation change. At least the change in the output voltage in decibels should be twice the change in the radiation attenuation within a 20dB input level change range. 2.5 Angular sensitivity measurement
SJ2534.12-87
Since the angular sensitivity of two-way fundamental frequency modulation is not easy to measure, the angular sensitivity S is usually determined according to formula (2). This formula has a satisfactory approximation at least in the crossover region (in this region, the harmonic components of the modulated waveform are not large). X100%1.67DbZxz.net
S=_21n10
In the formula, D—crossover depth, dB
β—3dB beam width, ().
Angular sensitivity can also be expressed by decibel difference V. The decibel difference is the algebraic difference between the two azimuth patterns at the extreme scanning position as shown in Figure 1 (a). The data is measured in decibels, V~(20lge)(
)=8.686(
3 Single-pulse angle tracking
The measurement of the single-pulse angle tracking antenna is carried out on the sum port and the difference port. The electric axis is determined by the minimum point of the difference pattern. The main measurement contents are electric axis measurement and difference slope measurement. 3.1 Electric axis measurement
3.1.1 Test system
The test system includes:
a. Antenna under test;
b. , additional circuits that process the signal appropriately to obtain an error signal: C. Remote signal sources (including extraterrestrial radio sources): d. Precision devices that orient the antenna (or moving signal source): e. High-precision optical or mechanical indicating mechanisms that indicate the direction of the antenna. 3.1.2 Measurement
The antenna (or signal source) is oriented at the minimum output on the appropriate error signal port of the circuit, and then this direction (or the position of the signal source) is recorded under specific frequency, environmental or other test variable conditions. By comparing this direction with the reference axis, the pointing error of that port can be determined. If it is not possible to continuously record the changes in the antenna system output as the signal source angle changes, it can be The minimum point is obtained by interpolation. Because the change of the electric axis with the system parameters during the test is more important than the absolute direction of the electric axis, the main requirement of the antenna direction indicating mechanism is high accuracy within a small angle range. A telescope fastened to the antenna base can be used to align the calibrated optical target at a distant signal source, or a dial indicator mounted on a long radial arm can be used. When tracking a moving target, a camera or laser can be used to measure the dynamic error between the electric axis and the reference axis. 3.2 Differential slope measurement
The definition of the differential slope K is related to the reference reference. When the isotropic radiator is used as the reference reference, K=dVGA
When the isotropic radiator is used as the reference reference, K=dVGA
When the sum gain of the same antenna is used as the reference benchmark, K
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Where: the power gain of the difference channel of the GA antenna; the peak power gain of the sum channel of the Go antenna; 0 angle, radians or degrees.
Other quantities can also be used as reference benchmarks. In actual measurement, only the average value within an appropriate angle range near the electric axis can be obtained, and the measurement method is the same as the ordinary radiation pattern measurement method.
Additional notes:
This standard was proposed by the Standardization Institute of the Ministry of Electronics Industry. This standard was drafted by the 39th Institute of the Ministry of Electronics Industry. The main drafter of this standard: Ke Shuren
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