With the rapid development of wireless communication technology, Radio Frequency (RF) antennas have become essential components in various wireless devices, including mobile communications, Wi-Fi, IoT (Internet of Things) devices, and automotive applications. As the demand for high-speed data transmission and low latency continues to grow, ensuring the communication quality of wireless transmission is becoming increasingly important. Depending on the application, RF antennas operate at different frequencies and power ranges. For example, the frequency range for mobile phone communication is 700–3500 MHz, GPS operates at 1575.42 MHz, 1227.60 MHz, and 1176.45 MHz, Bluetooth uses 2.4 GHz, and Wi-Fi primarily operates at 2.4 GHz, 5 GHz, and 6 GHz. As a critical component for signal transmission and reception, the performance of an RF antenna directly affects the overall system's stability and reliability.
When a product is exposed to external environments, the antenna often faces the threat of Electrostatic Discharge (ESD), especially in handheld systems frequently touched by users, which have a higher risk of ESD damage. The problem is exacerbated by the miniaturization and high integration of antennas, making the damage from ESD more severe. Therefore, protecting the antenna from ESD has become a crucial aspect of the design process.
To protect the antenna from ESD damage, TVS (Transient Voltage Suppressor) are commonly used as protective components. When ESD energy enters the antenna from the external environment, the TVS quickly activates to discharge the ESD energy, preventing excessive voltage and current from damaging the antenna and internal circuits, thereby ensuring stable operation and extending the device's lifespan.
As shown in Figure 1, when using a TVS as a protective component, it is connected in parallel with the RF antenna circuit. It should be placed as close as possible to the port susceptible to ESD on the PCB, allowing the TVS to activate rapidly and protect the circuit. Additionally, streamlined PCB layout can reduce parasitic inductance in the path, enhancing the effectiveness of protection coming from TVS.
Figure 1: Diagram of TVS Placement in an Antenna System
When selecting a suitable TVS as the protective component for an antenna, consider the following parameters based on the antenna system's requirements:
· Bidirectional or Unidirectional TVS: Antennas transmit signals that can either be unidirectional (varying only in positive voltage) or bidirectional (varying in both positive and negative voltages). In Figure 2, the antenna in the upper diagram transmits bidirectional signals, so a bidirectional TVS is needed to maintain signal integrity while ensuring ESD protection. If the antenna system only handles unidirectional signals, a unidirectional TVS is recommended as it offers excellent protection against positive ESD and a very low clamping voltage against negative ESD.
· Breakdown Voltage (VBV): As shown in Figure 3, the TVS VBV should be higher than the peak voltage of the antenna's transmitted signal. If the VBV is lower than the signal's peak voltage, the TVS may activate unnecessarily, disrupting the antenna's normal operation.
· Low Capacitance: Since the TVS is connected in parallel with the antenna system, using a TVS with too high capacitance can cause signal distortion, severely affecting signal transmission.
· Harmonic Distortion: Harmonics are frequencies that are integer multiples of the original signal frequency. In antenna systems, TVS can generate multiple harmonic distortions. Therefore, selecting a TVS that minimizes harmonic distortion ensures proper ESD protection while maintaining signal quality and stability.
· Insertion Loss (S21): As shown in Figure 4, choosing a TVS with high insertion loss can degrade signal amplitude and transmission quality. To ensure the system's performance remains unaffected at the target frequency, select a TVS with low S21 insertion loss for stable RF signal transmission.
Figure 2: Bidirectional Signals Require Bidirectional TVS; Unidirectional Signals Recommend Unidirectional TVS
Figure 3: VBV Must Be Equal to or Greater Than the Signal Peak
Figure 4: Low S21 TVS Can Reduce Signal Loss
To address the ESD protection needs of various antenna interfaces, the comprehensive solutions offered by AmazingIC are summarized in Table 1 below.
| Parts | Application | VRWM | VBV (Min.) | Package | ESD Clamping Voltage at 16A | CIN (Typ.) | IEC 61000-4-2 Contact ESD |
|---|---|---|---|---|---|---|---|
| AZ5B65-01F | Consumer | 5V | 6V | DFN0603P2Y | 20V | 0.3pF | ±15-kV |
| AZ5B75-01B |
Consumer | 5V | 6V | CSP0603P2Y | 18V | 0.1pF | ±8-kV |
| AZ5B85-01B | Consumer | 5V | 6V | CSP0603P2Y | 11V | 0.5pF | ±16-kV |
| AZ5H23-01BS | Consumer | 3.3V | 18.5V | CSP0603P2US | 10.5V | 0.25pF | ±18-kV |
| AZ9817-01F | Automotive | 17V | 18.7V | DFN1006P2E | 38V | 0.4pF | ±10-kV |
| AZ9024-01F | Automotive | 24V | 26.2V | DFN1006P2E | 39V | 0.6pF | ±30-kV |
| AZ9568-01F | Automotive | 8V | 10V | DFN1006P2E | 20V | 0.4pF | ±30-kV |
| AZ9924-01F | Automotive | 24V | 26.2V | DFN1006P2E | 53V | 0.3pF | ±11-kV |
Table 1: Comprehensive ESD Protection Solutions for RF Antennas
RF antennas play a crucial role in wireless communication. To effectively reduce ESD damage, TVS are the ideal protective solution. AmazingIC offers a range of TVS with different operating voltages, low capacitance, and excellent ESD protection characteristics, providing superior ESD protection while maintaining the high performance of the antenna. In RFIC circuit systems, the small 0201 (0.6mm × 0.3mm) package TVS are suitable for integration in limited PCB spaces. AmazingIC is committed to delivering comprehensive technical support to meet our customers' ESD design needs.