Spherical Near Field
Millimeter-wave near-field OTA rapid test system provides solutions
for one-stop testing of satellite communication antennas
Millimeter wave antenna/OTA fast measurement system
mmWave antenna application
With the successive releases of 3GPP Release 16, millimeter-wave phased array antenna technology will play an increasingly important role in 5G communications, in addition to its applications in traditional automotive radar and satellite communication antennas. Whether it is a non-standalone architecture (NSA) that uses millimeter-wave phased array technology for hotspot connections on the existing network architecture, or a completely independent architecture (SA) in the 5G frequency band, millimeter-wave phased array technology is inevitable. Its testing requirements and challenges have become issues that have to be faced.
The measurement challenges of 5G NR devices and systems are first and foremost in the innovation of wireless technology, in which changes in communication frequency and antenna technology are the main factors. Whether it is chip, terminal, or base station testing, new problems will be faced.
The full-band access of 5G and the application of MIMO technology make the traditional antenna of the terminal and the phased array antenna coexist, and the application of the phased array antenna leads to the diversification of the working state of the terminal, which greatly increases the test complexity.
Base Station Test
The 5G application scenario means the explosive growth of terminals and equipment. The huge contradiction between a large number of test requirements and the testing complexity of a single device will be the biggest problem that 5G measurement will face soon, and a high-precision and fast measurement system will become one of the core requirements.
In the millimeter wave band, space and cost constraints make the integrated design of the antenna and the chip an inevitable trend. The size of the chip is greatly reduced, and there is not enough space to connect the RF connector. The traditional chip test has become an OTA test connected by a phased array antenna. inevitable choice.
Main measurement methods of
Far field measurement
Far-field measurement (R≥2D2/λ, where R= test distance, D= DUT size, λ= working wavelength) is the basic method of antenna measurement, which has the characteristics of simple measurement scheme and accurate measurement results.
Crunch field measurement
The constricted field measurement method is a direct measurement method that achieves a similar far-field measurement effect within a near-field distance, using an arc-shaped reflective surface to convert a spherical wave into a plane wave, so as to achieve a similar far-field effect in a smaller space.
Near field measurement
In the near field of radiation, the far-field pattern can be more accurately derived through Fourier expansion based on mode theory, which has been widely used in traditional antenna measurements and OTA measurements, which can greatly reduce the size of the darkroom.
Core Theory: Near Field Measurement + Field Source Reconstruction Based on Physical Model
For the multi-wave position test of phased array antennas, the GTS proposes a field source reconstruction method based on a physical model in the radiation near field. Introduce the far-field pattern. Its core theoretical field source reconstruction (or equivalent source method) has been fully researched in the past two decades and a variety of equivalent unit reconstruction methods have been developed. In recent years, its application in near-field measurement has been increasingly received.
Schematic diagram of field source reconstruction
CH1900 Millimeter Wave Fast Measurement System
CH1900 is a multi-function fast measurement system positioned in the R&D and production stage of 5G millimeter wave equipment. With amplitude and phase calibration, antenna index measurement, RF index measurement and other functions. The CH1900 is optimally designed around the system objectives in terms of mechanics, RF components, calibration methods, and testing methods, enabling high-precision measurement of larger DUTs in a small space. Its miniaturized split design enables convenient and fast transportation and installation, and is suitable for workplaces such as R&D offices and laboratories.
CH1900 can be connected to VNA (or signal source and spectrum analyzer), radar simulator and wireless comprehensive tester respectively through a set of RF switch units to realize antenna performance measurement and RF compliance measurement. The complete test system architecture is shown in Figure 6 . The low noise amplifier circuit is included in the uplink and downlink, which can effectively increase the dynamic range of the system, and the typical value can reach 60dB.
Product RF Characteristics
Wide range of applications
Chip, terminal, base station, radar, satellite antenna.
High test accuracy
Through the design and optimization of mechanical accuracy, probe beam symmetry and cross-polarization, quiet zone reflection, and calibration methods, the accuracy of sampling data is improved and the test accuracy is guaranteed.
The optimized spherical wave near-far field transformation algorithm can improve the measurement speed by 20%–50%
Full test function
Antenna performance measurement; RF index measurement; Amplitude and phase calibration.
Large test area (quiet zone)
The high-gain narrow-beam probe antenna and high-performance EPP absorber and compact mechanical design ensure a large testable area in a small space, with reflection levels as low as -40dB.
Various testing methods
Direct far field, spherical wave near and far-field transformation, new field source reconstruction.
Product Mechanical Properties
The outer dimension is 2.74×1.62×2.06m, which can be divided into three independent parts with casters, which can enter the office building. The smallest passenger elevator (typical space is 0.9×1.4×2m) can be assembled and calibrated in the factory and then transported to the site for installation. Enable fast delivery.
Independent high-precision turntable and rocker coordinate system
The installation reference frame of the turntable and the rocker arm is processed as a whole with high precision, which ensures the mechanical accuracy and independence of the core test device, and is basically not affected by factors such as ground flatness, shielding body deformation and manual installation errors.
High-precision linear drive motor
The linear drive motor is used, with small size and high precision, better than 0.01mm, which is an order of magnitude higher than the conventional transmission method, and meets the unit amplitude and phase calibration requirements of phased array antennas such as millimeter-wave band chips and base stations.
- Supports free choice of test angle step size and test configuration.
- Click to view test data at any point is supported.
- The software integrates the system calibration function, and supports a wealth of test process anti-drop, breakpoint continuous and abnormal prompt settings, which effectively improves the reliability and fluency of the measurement.
- The original test data and log management are perfect, and the test process is unchangeable and traceable.
- Supports 3D testing, optional plane 2D testing and single-point testing verification.
- The batch function supports the establishment of task lists for unattended continuous testing.
- The software has built-in rich templates, and the preset parameter settings fully consider the characteristics of different instruments and platforms. The operation is simple and effectively avoids misoperation.
- The 3D data display software provides the function of rotating, browsing and cutting the orientation diagram at any angle, helping R&D engineers to analyze and diagnose problems intuitively.