Cross-Shaped Waveguide Probe for Reliable Near-Field Antenna Testing
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Solution Overview
Problem
Existing testing methods for high-frequency antenna elements and array antennas, such as those used in 5G and satellite communication, are complex and inefficient, particularly when measuring amplitude and phase properties, with over-the-air methods lacking reliability and far-field testing requiring multiple setups.
Innovation Solution
A cross-shaped waveguide test probe with a dielectric filler and lens element for near-field measurement, allowing for reliable and efficient testing of antenna properties by optimizing signal transmission and polarization stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If over-the-air (OTA) methods are used for testing antenna properties, then contactless measurement is achieved, but measurement reliability deteriorates
Solution Approach 1:
A test probe serving as an intermediary device is introduced between the measurement system and the antenna under test. The probe includes a waveguide with dielectric filler material and a lens element that mediates the electromagnetic field interaction, enabling reliable near-field measurements while maintaining contactless operation. The intermediary structure transforms the measurement approach from direct OTA to indirect near-field probing.
2Measurement precision
If far-field testing is performed with direct measurement of field properties, then field properties are directly measured, but test procedure complexity increases significantly
Solution Approach 1:
The measurement approach is inverted by performing near-field measurements instead of far-field measurements. The test probe measures electromagnetic field properties in the near-field region of the antenna, and through mathematical transformation (near-field to far-field transformation), the far-field characteristics are derived. This inversion simplifies the test procedure by eliminating the need for multiple positioning setups while maintaining measurement accuracy.
3Device complexity
If conventional waveguide designs are used, then simple structure is maintained, but polarization instability occurs
Solution Approach 1:
The waveguide structure is made asymmetric by introducing a dielectric filler material with specific permittivity that is not uniformly distributed. This asymmetric configuration creates stable polarization characteristics by preferentially guiding one polarization mode while suppressing others. The asymmetric dielectric loading compensates for the inherent polarization instability of simple waveguide structures.
4Adaptability or versatility
If broadband frequency detection is required, then frequency range is extended, but polarization instability increases
Solution Approach 1:
The dielectric constant of the filler material and the dimensions of the waveguide are optimized as key parameters to achieve broadband operation with stable polarization. By carefully selecting and adjusting these parameters, the waveguide maintains consistent polarization characteristics across a wide frequency range, resolving the trade-off between bandwidth and polarization stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The cross-shaped waveguide design enables broadband frequency detection, minimizes polarization instability, and facilitates simultaneous measurement of multiple antenna elements, with the option for near-field-to-far-field transformation.
Implementation Method 1
a lens element for coupling electromagnetic waves into the waveguide, the lens element being made of dielectric material
Implementation Method 2
a filler element made of dielectric material and disposed in the waveguide
Implementation Method 3
the waveguide is realized as a cross-shaped waveguide at least in sections
Data Source
AI summary
The present invention relates to a test probe (10) for contactless measuring of the electromagnetic properties of a radio unit (20), in particular an antenna unit, the test probe (10) comprising a waveguide (1) for transmitting electromagnetic waves, a filler element (2) made of dielectric material and disposed in the waveguide (1), a lens element (3) for coupling electromagnetic waves into the waveguide (1), the lens element (3) being made of dielectric material and being disposed at one end of the waveguide (1), and a contact portion (4) for coupling out a measurement signal, the contact portion (4) being disposed at an end of the waveguide (1) opposite the lens element (3).