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 release of 3GPP Release 16, millimeter-wave phased array antenna technology will play an increasingly important role in 5G communication, in addition to its applications in traditional automotive radar and satellite communication antennas. Although 5G Sub-6G applications have the advantage of wide coverage, they still cannot meet the requirements of future typical 5G application scenarios, such as enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable and low-latency communication (uRLLC), etc. Whether it is the non-standalone architecture (NSA) that uses millimeter-wave phased array technology for hotspot area connections on the existing network architecture or the completely independent architecture (SA) that uses the 5G frequency band, millimeter-wave phased array technology is already inevitable, and its testing requirements and challenges have become an issue that cannot be ignored.
The measurement challenges of 5G NR devices and systems first lie in the innovation of wireless technology, in which communication frequency and antenna technology changes are the main factors. Whether it is chip, terminal, or base station testing, they will all face new problems.
The full-frequency access and MIMO technology application of 5G enable the coexistence of traditional antennas and phased array antennas in terminals, and the application of phased array antennas leads to a diversification of terminal operating states, greatly increasing testing complexity.
Base Station Test
The application scenarios of 5G imply explosive growth of terminals and devices, and the huge contradiction between a large number of testing needs and the complexity of testing a single device will be the biggest challenge that 5G measurement is about to face, 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 antenna and chip integration design an inevitable trend. Chip size has greatly reduced and there is no longer enough space to connect RF connectors. Traditional chip testing has become OTA testing through phased array antennas, which has become an inevitable choice.
Main measurement methods of
Far field measurement
Far-field measurement (R≥2D2/λ, where R is the test distance, D is the size of the device under test, λ is the working wavelength) is a fundamental method for antenna measurement, characterized by a simple measurement scheme and accurate measurement results.
Crunch field measurement
The compact range measurement method is a direct measurement method that achieves similar far-field measurement results at near-field distances. It uses a curved reflector to transform spherical waves into plane waves, thereby achieving far-field-like effects in a smaller space.
Near field measurement
In the radiation near field, Fourier expansion based on mode theory can be used to accurately deduce the far-field radiation pattern. It has been widely used in traditional antenna measurement and OTA measurement, which can greatly reduce the size of the anechoic chamber.
Core Theory: Near Field Measurement + Field Source Reconstruction Based on Physical Model
For multi-beam testing of phased array antennas, the physical model-based field source reconstruction method in the radiation near field has been proposed by GTS. This method can reconstruct the characteristics of the source through sampling points in the near-field region and directly deduce the far-field radiation pattern from the source characteristics. The core theoretical field source reconstruction (or equivalent source method) has been extensively studied and developed various methods for reconstructing equivalent single elements in the past twenty years. In recent years, its application in near-field measurement has been increasingly valued.
Schematic diagram of field source reconstruction
RSP1900 Millimeter Wave Fast Measurement System
RSP1900 is a multi-functional and fast measurement system designed for the research and development and production stages of 5G millimeter-wave devices. It is suitable for various types of tested components (chips/terminals/base stations/automotive radar/satellite antennas, etc.) using phased array antenna technology, and has functions such as amplitude-phase calibration, antenna parameter measurement, and RF parameter measurement. RSP1900 is optimized and designed around the system’s goals in terms of mechanical, RF components, calibration methods, and test methods, achieving high-precision measurement of relatively large components in a small space. Its compact split design enables convenient and rapid transportation and installation, suitable for working places such as research and development offices and laboratories.
RSP1900 can be connected to a VNA (or signal generator and spectrum analyzer), radar simulator, and wireless comprehensive tester through a set of RF switching units to achieve antenna performance measurement and RF consistency measurement, as shown in the complete test system architecture. The uplink and downlink include low-noise amplification circuits, which can effectively increase the system’s dynamic range, with a typical value of up to 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 external dimensions of the device are 2.74×1.62×2.06 meters and can be split into three separate parts with wheels, which can fit into the smallest office elevator (typical space of 0.9×1.4×2 meters). The device can be assembled and calibrated in the factory, then transported to the installation site separately to achieve rapid delivery.
Independent high-precision turntable and rocker coordinate system
The installation reference frame for the turntable and rocker arm is processed as a whole with high precision, ensuring the mechanical accuracy and independence of the core testing equipment. It is basically unaffected by factors such as ground flatness, shield deformation, and human installation errors.
High-precision linear drive motor
Linear drive motors are used, with small size and high accuracy, better than 0.01mm, one order of magnitude higher in precision than conventional drive methods, meeting the requirements of unit amplitude-phase calibration for phased array antennas such as mmWave chips and base stations.
- Supports free selection of test angle steps and test configurations.
- Supports click-to-view for any point test data.
- The software integrates system calibration function and supports rich test process anti-drop, breakpoint reconnection, and abnormal prompt settings, effectively improving the reliability and smoothness of the measurement.
- Test raw data and log management are comprehensive, and the test process is solidified and cannot be changed, traceable.
- Supports 3D testing, optional 2D testing of the plane, and single-point testing verification.
- The batch processing function supports the establishment of a task list to achieve continuous testing without supervision.
- The software comes with rich templates, and preset parameter settings fully consider the characteristics of different instruments and platforms, with easy operations that effectively avoid operational errors.
- The 3D data display software provides directional graph arbitrary angle rotation and browsing, as well as cutting functions, helping R&D engineers intuitively analyze and diagnose problems.