The signal transmission loss of the Arc-Curved Waveguide is negatively correlated with the bending radius and positively correlated with the operating frequency, and it needs to be precisely matched with the waveguide size. These three key parameters do not act independently but jointly determine the signal transmission performance in high-frequency scenarios by influencing the uniformity of electromagnetic field distribution and the probability of mode conversion in a coordinated manner. In critical systems such as satellite communication and radar that have extremely high requirements for signal integrity, the optimal matching of the three is a core design element to ensure transmission stability and reduce energy loss, which is directly related to the realization of system detection accuracy, communication distance and anti-interference capability.
The core function of the bending radius
- The bending radius, as the most crucial geometric parameter of the Arc-curved Waveguide, directly determines the propagation continuity and stability of the electromagnetic field in the Arc transition section. When the bending radius is too small, the electromagnetic wave shape will cause severe field discontinuity during the sudden turn process, resulting in energy being unable to propagate along the ideal path, and then locally concentrating on the inner wall of the waveguide to form energy accumulation. This uneven distribution not only significantly increases insertion loss and reflection coefficient, but also disrupts the propagation balance of the dominant TE10 mode, exciting higher-order useless modes such as TE11 and TM11. These high-order modes, due to their poor compatibility with the waveguide structure, cannot propagate forward efficiently. Some of the energy will be dissipated in the form of heat, while the rest will form reverse reflection, ultimately resulting in significant signal attenuation.
- Conversely, the simulated and optimized bending radius can effectively minimize field disturbances, enabling the electromagnetic field to smoothly transition during the arc transition. The professional-grade Arc-Curved Waveguide, with the aid of 3D electromagnetic simulation technology and precise geometric design, can strictly control the standing wave ratio (VSWR) below 1.15, minimizing reflection loss to the greatest extent. This feature is particularly important in multi-segment waveguide cascaded application scenarios such as satellite communication ground stations and on-board microwave payloads. It can effectively avoid the accumulation of losses caused by multi-segment bending and ensure the signal integrity of long-distance transmission links.
The adaptation requirements for the waveguide size
- The strict matching of the cross-sectional size (a×b) of the Waveguide with the operating frequency is the basic prerequisite for the Arc-Curved Waveguide to achieve low-loss transmission. The design of the waveguide size must precisely match the signal wavelength of the target frequency band: if the size is too small, the effective propagation space of high-frequency signals will be restricted, and some electromagnetic energy may break through the waveguide boundary to form radiation leakage, resulting in energy overflow loss. If the size is too large, the internal waveguide will satisfy the propagation conditions of multiple modes, reducing the screening ability for the dominant mode and easily introducing multimode transmission phenomena.
- Multimode transmission can cause interference and coupling between different modes, resulting in additional mode conversion losses. In severe cases, it can even lead to signal waveform distortion. Therefore, precise size design must take ensuring the stable transmission of the dominant TE10 mode as its core objective. By strictly matching the wavelength with the cross-sectional size of the waveguide, a single-mode propagation environment is constructed. This adaptive design can significantly reduce the energy loss caused by mode conversion, ensuring that the Arc-Curved Waveguide can maintain consistent and stable transmission efficiency regardless of its position in the transmission link within the specific frequency band of satellite communication.
Frequency dependence of the working frequency
- Transmission loss has a significant dependence on the operating frequency, and this correlation is particularly prominent in the high-frequency band. As the operating frequency increases, the signal wavelength will gradually shorten. When the wavelength approaches the critical size of the arc-curved Waveguide Arc structure, the distortion risk of the electromagnetic field at the bend will increase sharply. At this point, even the slightest structural deviation may disrupt the symmetry of the field distribution, leading to a significant increase in the probability of mode conversion and subsequently causing a marked upward trend in transmission loss.
- For example, in the millimeter-wave field such as the K-band of 90-140GHz, the Arc-Curved Waveguide must adopt CNC five-axis linkage processing technology to control the structural dimensional tolerance at the micrometer level, so as to ensure the consistency of the Arc transition and ultimately control the insertion loss within 0.5dB. Meanwhile, in broadband application scenarios such as satellite communication, it is also necessary to take into account the performance balance of different frequencies. By optimizing the arc-shaped contour and structural parameters, the sharp increase in loss at specific frequency points caused by frequency resonance can be avoided. This wideband adaptation design can ensure that the Arc-Curved Waveguide maintains stable transmission performance throughout the entire working frequency band, providing reliable support for multi-band compatibility and anti-interference transmission in satellite communication.
Reference
1.Admie, M. (2025). How do bend radius, waveguide dimensions, and frequency affect signal loss in E bend waveguides? Admicrowave Technical Journal. https://www.admicrowave.com/knowledge/how-do-bend-radius-waveguide-dimensions-and-frequency-affect-signal-loss-in-e-bend-waveguides
2.Xexa Tech. (2025). China Leading Manufacturer for K Band Waveguide - WR8 Curved Waveguide E Bend 90-140GHz 25.4mm. Xexatech Product Datasheet. https://www.xexatech.com/leading-manufacturer-for-k-band-waveguide-wr8-curved-waveguide-e-bend-90-140ghz-25-4mm-xixia-product/
3.Song, W., et al. (2022). Curved Light Channels Have Better Coupling. Physical Review Letters, 129(4), 043901. http://www.shurl.cc/ce8eef80421d56af4833175140407f4a