1. Core Functions and ADAS Scenario Adaptability

　　Basic Function Positioning

　　An RF circulator is a three-port non-reciprocal device that achieves unidirectional signal transmission (e.g., Port 1 → 2 → 3) through the magnetic properties of ferrite materials. An isolator is a variant of a circulator with one port connected to a matched load, whose core function is to block reverse reflected signals. In ADAS, both devices mainly address two key pain points:

　　Transmit-Receive Isolation: They support radar systems in sharing a single antenna. Transmitted signals are sent to the antenna via the circulator, while received signals are directed from the antenna to the receiver, avoiding transmit-receive interference (isolation is usually ≥20 dB).

　　Device Protection: When the radar antenna experiences impedance mismatch due to obstacles (such as rain or snow), the isolator can absorb reflected energy to prevent damage to the power amplifier (PA).

　　Key ADAS Application Scenarios

　　For 77 GHz millimeter-wave radar, the role of the device includes transmit-receive channel isolation and anti-reflection protection, with typical requirements such as an operating frequency range of 76-81 GHz and insertion loss ≤1.6 dB. For 5G-V2X communication, the device is used for directional signal transmission between base stations and terminals, requiring support for the Sub-6G frequency band and isolation ≥15 dB. For imaging radar, the device is responsible for signal management of multi-antenna units, with requirements for a compact design to adapt to AESA arrays.

　　(Source: superscript:3superscript:4superscript:6)

　　2. Automotive-Grade Technical Characteristics and Certification Requirements

　　Core Indicators of Performance Parameters

　　Frequency Coverage: Mainstream products support a frequency range of 85 MHz-42.5 GHz, while ADAS radar-specific models focus on the 77 GHz frequency band.

　　Environmental Tolerance: They need to meet the requirements of a wide temperature range (-40°C ~ 105°C), resistance to vibration and impact, and a service life of ≥12 years.

　　Integration: Microstrip circulators have become the preferred choice for automotive applications due to their small size and no need for an external magnetic field, and they are compatible with MMIC technology (e.g., a 2.4 GHz four-port design verified by ADS simulation).

　　Mandatory Certification System

　　Component-Level: Compliance with AEC-Q100 certification (including stress testing and life verification).

　　Production End: Adherence to the IATF16949 quality management system and provision of PPAP documentation support.

　　3. Market Pattern and Market Scale

　　Market Scale and Growth

　　The global market size of automotive RF chips is expected to grow from USD 900 million in 2021 to USD 1.9 billion in 2027, with a compound annual growth rate (CAGR) of 11.6%. Circulators and isolators account for approximately 15%-20% of this market.

　　(Source: Yole Data)

　　4. Technical Challenges and Development Trends

　　Existing Bottlenecks

　　It is difficult to control the loss of ferrite materials in the high-frequency band (79 GHz);

　　There is a design conflict between multi-band compatibility and miniaturization (the volume of traditional waveguide structures exceeds automotive-grade limits).

　　Future Directions

　　Integration: Packaging with devices such as PAs and LNAs into RF front-end modules;

　　Wide Frequency Band: Developing millimeter-wave devices covering 60-100 GHz to adapt to next-generation imaging radars;

　　Reliability Upgrade: Adopting ceramic-metal packaging technology to improve stability in high-temperature environments.

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