The Ka-band circulator is a key device used in the microwave and radio frequency fields. Its working principle is based on the unidirectional transmission and isolation function of the signal. The circulator realizes the directional flow of signals between different ports through a specific structural design, thereby avoiding the reverse propagation of the signal and ensuring the unidirectionality of the signal transmission.
Basic working principle
The circulator usually has three or four ports. After the signal enters from one port, it is transmitted to the next port in a predetermined direction through the internal magnetic material or ferrite element and is isolated to prevent the signal from returning in the opposite direction.
For instance, in a standard three-port circulator, the signal comes in through the input port, travels along the internal pathway of the circulator, and is then sent to the output port.
At the same time, it is completely isolated by the isolation port, thereby realizing the unidirectional flow of the signal.
Features of Ka-band circulator
Frequency range: Ka-band circulators typically function within a frequency range of 26.5 to 40 GHz, making them ideal for applications like satellite communications, radar systems, and wireless communication.
Insertion loss and isolation: High-quality Ka-band circulators have low insertion loss (e.g., less than 0.3dB) and high isolation (e.g., more than 20dB), which enables them to reduce energy loss and prevent signal interference during signal transmission.
Structural form: Ka-band circulators can adopt different structural forms, such as all-ferrite substrate structure, embedded structure, microstrip circulator, etc. These designs help to reduce insertion loss, increase bandwidth and achieve miniaturization.
Working process
Signal transmission:
When the signal enters through the input port, it travels through the magnetic material or ferrite component within the circulator and is directed to the output port via a specific route. For example, in a typical three-port circulator, the signal enters from port 1 and is transmitted to port 2 after passing through the circular path, while port 3 is completely isolated.
Isolation function: The circulator implements the signal isolation function through magnetic materials or ferrite elements. This indicates that the signal cannot travel from the output port back to the input port, thus guaranteeing one-way transmission of the signal.
Frequency characteristics: Ka-band circulators are usually designed as broadband devices that can maintain stable performance over a wide frequency range. For example, some Ka-band circulators cover the frequency range of 26.5 to 40 GHz and have low insertion loss and high isolation.
Application scenarios
Satellite communication: Ka-band circulators are widely used in satellite communication systems for signal isolation and unidirectional transmission to improve communication quality and system stability.
Radar system:
Ka-band circulators are utilized in radar systems to provide isolation between transceivers, preventing interference between transmitted and received signals.
Wireless communication: In 5G base stations and other wireless communication equipment, Ka-band circulators are used for power amplifier link matching, wave splitting circuits, and other functions.
Technical advantages
Miniaturization and integration: By adopting advanced design methods (such as the admittance slope method) and materials (such as low-temperature co-fired ceramics), Ka-band circulators have achieved miniaturization and integration, which is convenient for integration with other microwave devices.
High power capacity: Some Ka-band circulators can support signal transmission up to tens of watts or even higher power, suitable for high-power base stations and radar systems.
Ka-band circulator plays an important role in the microwave and radio frequency fields through its unique structural design and working principle. It can not only realize the one-way transmission and isolation of signals, but also has low insertion loss, high isolation and broadband characteristics, and is widely used in satellite communications, radar and wireless communications.
Reference:
1. Kaiyu Zhang, Shangyuan Li et al. "An All-Optical Ka-Band Microwave Long-Distance Dissemination System Based on an Optoelectronic Oscillator." IEEE Photonics Journal.
2. WR28 Ka Band 26.5~40GHz RF Waveguide Circulator 25W Broadband Circulator. UIY Inc. [2025-01-01]
3. Self-biased Circulators. Metamagnetics. [2016-11-11]
4. CIRCULATOR. VALVO Bauelemente GmbH.