Protecting the "Precision Eyes" of Millimeter-Wave Radar: High-Isolation 28GHz RF Circulators/Isolators—The Core Barrier for Module Anti-Interference

With the rapid penetration of millimeter-wave radar technology, the 28GHz frequency band, with its short wavelength phase resolution of 10.7mm and wide available bandwidth of 1GHz, has become a "golden band" for scenarios such as automotive ADAS, industrial sensing, and security monitoring. However, the short wavelength of millimeter-wave signals also presents inherent challenges: signals are susceptible to multipath scattering and crosstalk from adjacent radars. Furthermore, the close coupling between the high-power transmitter and the high-sensitivity receiver within the radar module increases the risk of signal "self-interference," directly leading to problems such as reduced detection range, increased false detection rates, and damage to core components. High-isolation 28GHz RF circulators/isolators are the "anti-interference core" tailored for millimeter-wave radar modules, safeguarding every accurate sensing from the source.

Why are high-isolation 28GHz devices essential for millimeter-wave radar modules?

The core requirement for millimeter-wave radar is "precise detection without interference." However, the signal isolation requirements for applications in the 28GHz frequency band far exceed those of standard RF applications:

Scenarios with dense interference: In automotive applications, the 28GHz ADAS radars (forward collision warning and blind spot monitoring) of multiple vehicles in a traffic flow operate simultaneously, making crosstalk highly likely. In industrial applications, multiple 28GHz radars (for material level detection and robot obstacle avoidance) are densely deployed in a workshop, creating a complex electromagnetic environment where external clutter can easily penetrate the receiver.

High risk of intra-module coupling: The transmitter (PA output power typically reaches 10-30W) and receiver (LNA with a low noise figure of less than 1dB and extremely high sensitivity) of a millimeter-wave radar module are often integrated on the same PCB, separated by only a few centimeters. Without high isolation protection, the high-power signal from the transmitter can directly couple to the receiver, potentially drowning out weak echo signals (leading to missed detection) or, in severe cases, damaging the highly sensitive LNA chip, rendering the module useless. The high-loss nature of the 28GHz frequency band amplifies demand: Millimeter-wave signals attenuate rapidly during transmission (approximately 22dB per kilometer). Excessive insertion loss in devices further reduces radar detection range. Furthermore, insufficient isolation allows interference signals to slip through and overlap with the echo signal, reducing the signal-to-noise ratio. This necessitates that 28GHz devices meet both high isolation and low loss.

High-isolation 28GHz RF circulators/isolators leverage the nonreciprocity principle of ferrites to achieve "unidirectional signal transmission + strong reverse isolation":

RF circulators: Three-port directional transmission precisely directs the 28GHz signal from the transmitter (TX) to the antenna (ANT), while simultaneously directing the (weak) echo signal received by the antenna to the receiver (RX), completely eliminating direct coupling between the TX and RX signals and preventing "transmit-receive" self-interference.

RF isolators: Connecting one port of the circulator to a matched load provides focused "reverse isolation." When an antenna experiences standing waves (e.g., due to external obstructions) or when external interference signals attempt to penetrate the antenna, the isolator absorbs or blocks the reverse signal, protecting the transmit PA from overload and simultaneously providing a "noise barrier" for the receive LNA.

High-Isolation 28GHz RF Circulator/Isolator: Four Core Advantages Meet the Stringent Requirements of Radar

To address the performance pain points of millimeter-wave radar modules, high-isolation 28GHz devices are not simply "upgrades" of standard 28GHz products. Instead, they are fully customized from the perspectives of materials, structure, and process, offering four irreplaceable core capabilities:

1. Ultra-High Isolation: ≥35dB, Eliminating Interference Signals

Ordinary 28GHz RF devices typically have an isolation of 25-30dB, which only reduces interference by a factor of 100-300, but may still leave residual interference signals that could impact radar performance. This product utilizes a dual ferrite core stacking design and precision impedance matching to enhance reverse isolation to ≥35dB (some high-performance models can reach 40dB). This means that reverse interference signals are attenuated by over 3,000 times. Even in scenarios where multiple radars are operating densely (such as traffic jams and industrial workshops), the receiver can only "hear" the target echo signal, reducing the false detection rate by over 90%, completely eliminating the risk of false alarms or missed detections caused by interference. 2. Narrowband High Precision: Full Coverage from 27.5 to 28.5 GHz, Compatible with Mainstream Frequency Bands

The commercial frequency band for 28 GHz millimeter-wave radars is concentrated in the 27.5-28.5 GHz band (the allocated bandwidth in most regions worldwide). This device utilizes high-Q ferrite material to achieve "precise lock" to this frequency band:

The center frequency deviation is ≤±50 MHz, ensuring perfect matching with the radar module's TX/RX frequency bands without signal offset loss.

The relative bandwidth is ≥3%, covering the radar module's FM bandwidth (typically 500 MHz to 1 GHz) without additional adjustments, ensuring direct compatibility with mainstream radar chipsets (such as 28 GHz radar ICs from Infineon, Texas Instruments, and STMicroelectronics).

3. Low Insertion Loss: ≤0.5 dB, Extending Radar's Detection Field of View

Millimeter-wave signals inherently attenuate rapidly. Excessive device insertion loss can directly reduce radar detection range (for example, every 0.5 dB increase in insertion loss can reduce detection range by 10%-15%). This product utilizes a gold-plated microstrip line design and a low-loss dielectric substrate to minimize forward insertion loss to **≤0.5dB** (typical value 0.35dB), minimizing useful signal attenuation.

For automotive forward-facing radar, this extends the detection range from 150 meters to over 170 meters, allowing more time for emergency braking.

For industrial liquid level radar, it can accurately detect liquid levels in tanks over 10 meters deep, eliminating measurement errors caused by signal attenuation. 4. Miniaturization + High Reliability: Suitable for Module Integration and Harsh Operating Conditions

Millimeter-wave radar modules (especially automotive and industrial models) have stringent requirements for size and reliability. This device is designed to fully meet these requirements:

Ultra-small package: Utilizing a surface-mount package, the device measures as small as 5mm × 5mm × 2mm, just one-third the size of traditional metal-cased devices. This allows for easy integration into compact radar PCBs, saving over 30% of board space.

Full-Scenario Reliability: Operating temperature ranges from -40°C to +105°C, meeting the requirements of both automotive high- and low-temperature cycling (-40°C to +85°C) and industrial high-temperature environments (+105°C). It also achieves AEC-Q200 automotive certification (for automotive models), meeting vibration (10-2000Hz) and shock (1000G) standards, ensuring long-term stable operation and an MTBF (mean time between failures) exceeding 100,000 hours. Deeply Empowering Scenarios: From automotive to industrial applications, safeguarding every "precise perception"

High-isolation 28GHz RF circulators/isolators are not general-purpose devices; instead, they provide customized protection for the pain points of different millimeter-wave radar scenarios:

1. Automotive ADAS Radar: Clearing Interference for Safe Driving

In automotive forward radar, blind-spot monitoring radar, and automated parking radar, components must address two core challenges:

Resisting "Vehicle-to-Vehicle Interference": When multiple vehicles equipped with 28GHz radars are running parallel or intersecting, high isolation (≥35dB) completely blocks radar signal crosstalk from adjacent vehicles, preventing interference-induced "misjudgment of preceding vehicles" or "missed blind-spot detections."

Protecting Core Components: The instantaneous power of an automotive radar PA can reach 30W. If the antenna experiences abnormal standing waves (e.g., rain or snow), the reverse power can easily burn out the LNA. Isolators can absorb over 99.9% of reverse power, extending the life of radar modules (from 3 years to over 5 years) and reducing after-sales costs for automakers.

2. Industrial Millimeter-Wave Radar: Providing Stable Support for Smart Manufacturing

In scenarios such as industrial material level detection, robot obstacle avoidance, and conveyor belt foreign object detection, devices must adapt to complex electromagnetic environments:

Resistance to Industrial Electromagnetic Interference: Motors and inverters within factories generate strong electromagnetic interference. High isolation blocks this interference, ensuring the measurement accuracy of the level radar (error ≤ 1%) and preventing material spills or shortages caused by false detection.

Tolerance to Harsh Environments: In high-temperature workshops (such as those in the metallurgical and chemical industries), the device's wide operating temperature range of -40°C to +105°C ensures stable operation without the need for additional heat dissipation, meeting the 24/7 operational demands of industrial equipment. 3. Security Millimeter-Wave Radar: Eliminating False Alarms for Perimeter Protection

Multiple radar deployments are common in perimeter intrusion detection radar systems at airports, substations, and warehouses.

Preventing "radar crosstalk": When multiple 28GHz security radars are deployed in the same area, high isolation ensures that each radar operates independently, preventing false alarms caused by signal crosstalk, thus reducing unnecessary investigation costs for security personnel.

Improving detection sensitivity: Low insertion loss ensures that the radar can detect small targets (such as pedestrians and small animals) up to 100 meters away. High isolation reduces noise interference, ensuring that any intrusion is detected and no security risks are missed. Conclusion: High Isolation Builds the Reliable Foundation of Millimeter-Wave Radar

For millimeter-wave radar module manufacturers, high-isolation 28GHz RF circulators/isolators are far from optional accessories; rather, they are the core element that determines radar performance, reliability, and scenario adaptability. They not only address interference issues but also provide differentiated competitive advantages for products, enabling automotive radars to pass rigorous EMC testing, industrial radars to meet high-precision requirements, and security radars to achieve zero false alarms.

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