“ In the printed circuit board assembly (PCBA) of 5G communication devices, radio frequency (RF) interference has become a critical factor affecting communication quality and user experience. Effectively suppressing RF interference to enhance the performance of 5G communication devices has become a focal point of current research.”
01
—
5G Communication Frequency Bands and Sources of RF Interference
5G communication frequency bands are primarily distributed in the Sub-6 GHz and millimeter-wave bands. Within these bands, the sources of RF interference are diverse.
1. Harmonic Interference
Nonlinear components in electronic devices, such as power amplifiers, generate harmonics during operation. These harmonic frequencies are integer multiples of the fundamental frequency, and when they fall within the 5G communication frequency band, they can interfere with normal signals, leading to signal distortion and increased bit error rates. For example, some RF chips generate rich harmonics due to the nonlinear characteristics of their internal circuits when processing high-frequency signals. If not suppressed, these harmonics can propagate on the PCBA board, affecting the normal operation of other circuits.
2. Spatial Radiation Interference
As 5G devices become smaller and more integrated, the component layout on the PCBA board becomes increasingly compact. The reduced distance between different circuit modules makes it easier for signals to radiate and couple through space. For instance, strong signals generated by transmitters can radiate through space to nearby receivers, interfering with the receiver’s ability to capture weak signals. Additionally, other wireless devices in the surrounding environment, such as Wi-Fi routers and Bluetooth devices, can also generate RF radiation that interferes with 5G communication.
02
—
5G Communication PCBA RF Interference Suppression Solutions
1. Reasonable PCB Layout A
① Modular Design
Modular design of key components such as RF chips, baseband chips, and power modules, while maintaining appropriate spacing, can reduce electromagnetic coupling between different modules and lower the likelihood of mutual interference. For example, concentrating the RF module on one side of the PCBA board, separated from the baseband and power modules, and using reasonable wiring and isolation measures can reduce signal crosstalk between them.
② Partitioned Layout
Separating sensitive circuits (such as receivers) from interference sources (such as transmitters and switch-mode power supplies) and using shielding covers for isolation can effectively block electromagnetic waves generated by interference sources from radiating into the surrounding space, protecting sensitive circuits from interference. For example, installing a metal shielding cover around the receiver can isolate it from interference sources like transmitters, reducing the impact of interference signals on the receiver.
2. Ground Plane Segmentation
Separating digital and analog ground planes can prevent digital signals from interfering with analog signals. Digital signals, with their fast rise and fall times, can generate significant current changes, resulting in noise on the digital ground plane. If the digital and analog ground planes are not separated, this noise can couple into the analog circuits, affecting the quality of the analog signals. By segmenting the two and connecting them at appropriate points, noise coupling on the ground plane can be reduced.
3. Optimizing Traces
① Differential Traces
For high-speed signal lines, using differential trace methods is recommended. Differential signals consist of a pair of signals with equal amplitude and opposite polarity, which experience similar interference during transmission. At the receiving end, a differential amplifier can cancel common-mode interference, effectively suppressing electromagnetic interference. For example, using differential traces in high-speed data transmission lines in 5G communication can enhance the signal’s resistance to interference, ensuring accurate data transmission.
② Impedance Matching
Ensuring that the trace impedance matches the input and output impedance of the RF chip can reduce signal reflections and standing waves. When signals propagate along transmission lines, impedance mismatches between the transmission line and load can cause signal reflections, which, when combined with the original signal, can lead to signal distortion and reduced transmission efficiency. By appropriately selecting PCB materials and controlling trace width and spacing, impedance matching can be achieved, improving signal transmission quality.
4. Reducing Via Count
Vias can introduce parasitic capacitance and inductance, affecting signal quality, so their number should be minimized. Each via acts as a small inductor and capacitor combination, and during high-frequency signal transmission, these parasitic parameters can cause additional attenuation and phase shifts in the signal. Optimizing trace layout to reduce unnecessary vias is crucial for enhancing signal integrity during PCBA design.
5. Selecting Appropriate PCB Materials and Processes
For RF circuit design in the 5G frequency band, high dielectric constant and low-loss PCB materials should be used. High dielectric constant materials can reduce PCB size to meet the miniaturization requirements of 5G devices, while low-loss materials can decrease energy loss during signal transmission, improving transmission efficiency. For instance, some new high-frequency PCB materials, such as polytetrafluoroethylene (PTFE)-based composites, exhibit excellent high-frequency performance and are widely used in 5G communication PCBA design. Additionally, employing advanced manufacturing processes, such as multilayer board manufacturing and high-precision line fabrication, can enhance PCB quality and reduce signal interference caused by manufacturing errors.
6. Shielding and Filtering
① Shielding Covers
Adding shielding covers around RF chips and sensitive circuits can effectively isolate external electromagnetic interference. Shielding covers are typically made of metal materials, such as copper or aluminum, which can reflect or absorb interference signals, preventing them from entering the protected circuit area. For example, in the RF modules of 5G base stations, installing independent shielding covers for each RF chip can significantly reduce the impact of external interference on chip operation.
② Filters
Adding filters to power and signal lines can eliminate unnecessary noise and interference signals. For instance, using EMI filters can suppress the propagation of electromagnetic interference signals, while ferrite beads can filter signals in high-frequency bands, attenuating unwanted high-frequency noise. In the power input lines of 5G communication devices, series connection of ferrite beads can effectively filter out high-frequency noise from the power supply, providing clean power to the circuit.
7. EMI Absorbing Materials
Applying EMI absorbing materials on the PCBA board can absorb radiated electromagnetic waves, reducing interference. EMI absorbing materials can convert electromagnetic wave energy into heat or other forms of energy, thereby lowering the intensity of electromagnetic radiation in the space. In some 5G devices with high electromagnetic compatibility requirements, applying EMI absorbing materials in specific areas of the PCBA board can further enhance the device’s resistance to interference.
8. Grounding Design
① Single Point Grounding
Connecting the grounding pins of RF circuits to a single grounding point can avoid ground loop interference introduced by multipoint grounding. Ground loops can create potential differences between different grounding points, causing current to flow in the ground loop and generating additional interference signals. Using single-point grounding ensures consistent grounding potential across the entire RF circuit, reducing the impact of ground loop interference. For example, in the design of 5G communication modules, connecting all RF-related grounding pins to a common grounding point on the PCBA board is recommended.
② Large Area Copper Pouring
Implementing large area copper pouring on the PCBA board can reduce grounding impedance and improve grounding effectiveness. Grounding copper pouring increases the cross-sectional area of the grounding conductor, lowering grounding resistance and allowing grounding currents to flow more smoothly back to ground. Additionally, large area copper pouring can provide shielding effects, reducing crosstalk between signals. In the design of 5G communication PCBA, large area grounding copper foil should be laid on the top and bottom layers of the PCBA board, and vias should be used to connect the grounding copper foils of different layers, forming a good grounding plane.
Conclusion
Through reasonable PCBA layout, optimized traces, selection of appropriate PCB materials and processes, as well as effective shielding, filtering, and grounding design, a series of key technologies can effectively suppress RF interference in 5G communication PCBA, enhancing the performance and reliability of 5G communication devices. The comprehensive application of these technologies not only provides users with a more stable and high-speed 5G communication experience but also promotes the widespread application and further development of 5G technology in various fields. In the future development of 5G communication devices, continuous attention to and improvement of RF interference suppression technologies will be an important way to enhance product competitiveness and meet user needs.