ingiant technology | Industry new | April 21.2025
As 5G communications are rapidly becoming popular and radar technology is constantly innovating, RF rotary joints, as core components for achieving stable signal transmission, are playing an increasingly critical role. Whether it is a satellite antenna in the vast space or an automated production line in a complex environment on the ground, it can ensure seamless transmission of signals between fixed and rotating parts. Next, we will delve into the technical details and practical applications of RF rotary joints.
Ⅰ. Exploring the working core of RF rotary joints
The operating principle of RF rotary joints is a subtle fusion of electromagnetism and mechanical engineering. It builds a signal bridge between the rotating end and the fixed end through transmission media such as coaxial cables, waveguides or optical fibers. During signal transmission, the internal electric field and magnetic field interact and transform, and the mechanical structure assumes the key responsibility - ensuring stable contact during rotation to avoid signal loss or distortion caused by poor contact, thereby achieving efficient and stable transmission of RF signals.
Ⅱ. Analysis of the types and characteristics of RF rotary joints
(I) Single-channel coaxial rotary joints: basic and reliable signal messengers
Single-channel coaxial rotary joints have become the "main force" for transmitting single RF signals with their simple structural design. Taking the field of security monitoring as an example, in high-definition cameras at urban traffic intersections, single-channel coaxial rotary joints can help cameras achieve 360-degree rotation without dead angles, while ensuring that video signals are transmitted to the monitoring center with low latency and high definition. Its typical electrical parameters are: frequency range can reach DC - 18GHz, insertion loss is controlled at 0.3 - 0.5dB, voltage standing wave ratio (VSWR) ≤1.2; in terms of mechanical properties, the maximum speed can reach 3000rpm, and the rotation life exceeds 10 million revolutions, which can meet the needs of long-term continuous work.
(II) Multi-channel coaxial rotary joints: signal coordinators for complex systems
Multi-channel coaxial rotary joints are designed to meet the simultaneous transmission of multiple signals in complex systems. In the phased array radar system in the military field, it can simultaneously process multiple types of RF signals such as transmission signals, reception signals, and control signals to ensure that the radar detects targets in all directions and with high precision. The electrical parameters of this type of joint are usually: frequency range DC - 12GHz, single-channel insertion loss of about 0.6dB, VSWR≤1.3; in terms of mechanical parameters, it can withstand a torque of 0.5 - 2N・m, and a maximum speed of 2000rpm, ensuring stable operation during complex signal transmission.
(III) Waveguide rotary joint: signal transmission expert in high-power scenarios
The waveguide rotary joint relies on waveguide technology and has an advantage in high-power, low-loss signal transmission scenarios. In satellite communication ground stations, it is responsible for efficiently transmitting high-power RF signals to satellites, providing solid support for global communications. Its electrical parameters are outstanding, the frequency range is mostly concentrated in 8-18GHz, the insertion loss is only 0.3dB, and the power capacity can reach the kilowatt level; in terms of mechanical performance, the rotation accuracy is extremely high, the rotation life can reach 8 million revolutions, and it has good vibration and impact resistance, and can adapt to harsh outdoor environments.
(IV) Fiber optic rotary joint: Pioneer in high-speed data transmission
Fiber optic rotary joints use optical signals as transmission carriers. With their fast transmission rate and strong anti-interference ability, they have become the preferred choice in the field of high-speed data transmission. In the optical communication network of large data centers, fiber optic rotary joints can ensure stable transmission of data at a rate of 10Gbps or even higher between rotating connection components. Among its electrical parameters, the insertion loss is about 1dB; in terms of mechanical parameters, the maximum speed is 1500rpm, the rotation life is 6 million revolutions, and it can work normally under different temperature and humidity environments, ensuring stable data transmission.
Ⅲ. Unlocking the key design parameters of RF rotary joints
(I) Electrical parameters: core indicators of signal transmission quality
a. Frequency range: This parameter determines the frequency range in which the RF rotary joint can work effectively. From low-frequency direct current signals (DC) to high-frequency frequency bands of tens of GHz, different types of rotary joints have different focuses. For example, a single-channel coaxial rotary joint can cover a wide frequency range and is suitable for a variety of signal transmission scenarios; while a waveguide rotary joint is optimized for a specific high-frequency band to meet the needs of high-frequency signal transmission.
b. Insertion loss: Indicates the degree of power loss of a signal when it passes through a rotary joint, usually in dB. The lower the insertion loss, the less energy loss during signal transmission and the higher the transmission efficiency. Generally speaking, the insertion loss of a single-channel coaxial rotary joint is relatively low, between 0.3 and 0.5 dB; due to the complex structure of a multi-channel coaxial rotary joint, the insertion loss will be slightly higher, between 0.5 and 0.8 dB.
c. Voltage standing wave ratio (VSWR): This parameter is used to measure the reflection of RF signals during transmission. The closer the VSWR value is to 1, the smaller the signal reflection and the higher the transmission efficiency. The VSWR of a high-quality RF rotary joint is usually controlled at ≤1.2, which can effectively reduce the energy loss and interference caused by signal reflection.
d. Power capacity: refers to the maximum power value that the rotary joint can withstand. When the actual transmission power exceeds this capacity, it may cause the equipment to overheat, damage or even fail. Waveguide rotary joints have a high power capacity of up to kilowatts due to their unique structure and materials; coaxial rotary joints have a relatively low power capacity, generally around a few hundred watts.
(II) Mechanical parameters: a solid foundation for ensuring stable operation
a. Maximum speed: reflects the maximum rotation speed at which the rotary joint can work stably. In different application scenarios, the requirements for speed vary significantly. For example, the speed of the robotic arm of an industrial automation production line may only be a few hundred rpm; while in some high-speed rotating radar systems, the speed needs to reach 3000rpm. Therefore, when selecting a rotary joint, it is necessary to ensure that its maximum speed meets the actual application requirements.
b. Rotation life: measured by the number of rotations or the time of use, it is an important indicator for evaluating the durability of a rotary joint. Generally, the rotation life of an RF rotary joint is more than millions of revolutions to ensure that the equipment maintains stable performance during long-term operation.
c. Torque: the torque required for the rotary joint to rotate. Due to the complex internal structure of the multi-channel coaxial rotary joint, the torque it needs to withstand is relatively large, generally between 0.5 and 2N・m. Appropriate torque parameters can ensure that the rotary joint runs smoothly during rotation, avoiding rotation jamming due to insufficient torque or component damage due to excessive torque.
d. Environmental adaptability: covers multiple aspects such as working temperature, humidity, and dust and water resistance levels. Rotary joints used outdoors must have a protection level of IP65 or above to resist the invasion of dust and rain; at the same time, the operating temperature range is usually required to be -40℃ - 85℃ to adapt to environmental changes in different regions and seasons.
Ⅳ. Focus on the practical application of RF rotary joints in the industry
(I) Military field: Building a solid technical defense line for national defense security
In a new air defense early warning radar system, multi-channel coaxial RF rotary joints play an irreplaceable role. The radar system needs to transmit and receive signals from multiple frequency bands at the same time to achieve all-round detection and precise tracking of aerial targets. Through the multi-channel coaxial rotary joint, the radar antenna can perform 360-degree rotation scanning uninterruptedly, and its electrical parameters fully meet the stringent requirements of the frequency range DC - 12GHz, insertion loss less than 0.8dB, and VSWR≤1.3, effectively improving the detection distance, accuracy and reliability of the radar, and providing a strong guarantee for national defense security.
(II) Communication field: Building a signal bridge for global interconnection
In a certain international satellite communication network, waveguide RF rotary joints are used in large antenna systems of ground stations. As the satellite continues to move in space, the ground station antenna needs to adjust its direction in real time to maintain communication connection with the satellite. The waveguide rotary joint, with its high power capacity and low loss characteristics, stably transmits high-power RF signals. Its frequency range of 8-18GHz, insertion loss of 0.3dB, and power capacity of 1000W greatly improve the data transmission rate between the ground station and the satellite, significantly reduce the communication delay, and achieve high-speed and stable communication on a global scale.
(III) Industrial Automation: The Key Engine Driving Intelligent Production
In the automated production line of a certain automobile manufacturing company, a single-channel coaxial RF rotary joint is installed on the rotating part of the robotic arm. The robotic arm needs to rotate frequently in welding, spraying, assembly and other processes, and at the same time transmit control signals and sensor data to ensure precise operation. The parameters of the rotary joint with a frequency range of DC-18GHz, insertion loss of 0.5dB, VSWR≤1.2, and a maximum speed of 3000rpm are perfectly adapted to the working requirements of the robotic arm. Even in high-intensity and long-term production operations, it can ensure stable signal transmission, effectively improving the automation level and production efficiency of the production line, and reducing labor costs and product defective rates.
Ⅴ. Master the practical strategy of selecting RF rotary joints
To select a suitable RF rotary joint, it is necessary to combine the actual application scenario and comprehensively consider the following factors:
a. Working frequency matching: According to the frequency of the signal required to be transmitted by the system, select a rotary joint that can fully cover the frequency range to avoid abnormal signal transmission due to frequency mismatch.
b. Power carrying capacity: According to the actual power size of the system, select a rotary joint with sufficient power capacity and a certain margin to prevent equipment failure caused by power overload.
c. Signal transmission efficiency: Prioritize products with low insertion loss and VSWR close to 1 to ensure the efficiency and stability of the signal during transmission.
d. Mechanical performance adaptation: Comprehensively consider mechanical parameters such as maximum speed, rotation life, torque, etc. to ensure that the rotary joint can adapt to the operating conditions and service life requirements of the equipment.
e. Environmental adaptability: According to the characteristics of the use environment, such as temperature, humidity, dust, corrosive gases, etc., select a rotary joint with corresponding protection level and environmental adaptability to ensure the normal operation of the equipment in a complex environment.
Ⅵ. Future development of RF rotary joints
With the rapid development of science and technology, RF rotary joints will continue to evolve towards miniaturization, integration, and intelligence. Ingiant Technology's joint series products are designed for RF signal transmission, with a maximum frequency of 40GHZ. The coaxial contact design gives the connector an ultra-wide bandwidth and no cut-off frequency. The multi-contact structure effectively reduces relative jitter, the overall size is small, and the connector is plug-in and easy to install. The current, voltage, shell and color can be customized. I believe that ingiant company will continue to inject strong impetus into the innovation and development of various industries.
Post time: Apr-21-2025