Combating Fractional Spurs in Phase Locked Loops to Improve Wireless System Performance in Beyond 5G

As wireless technology continues to evolve, the demand for faster and more reliable communication systems has led to the development of beyond 5G networks. These networks aim to provide higher data rates, lower latency, and improved overall performance. However, one of the challenges faced in achieving these goals is the presence of fractional spurs in phase-locked loops (PLLs).

Understanding Fractional Spurs

Fractional spurs are unwanted spurious signals that occur at non-integer multiples of the PLL reference frequency. These spurs can degrade the performance of wireless systems by causing interference, reducing signal quality, and increasing bit error rates. In beyond 5G networks, where higher frequencies and wider bandwidths are utilized, the impact of fractional spurs becomes even more significant.

The Impact on Wireless System Performance

Fractional spurs can lead to various performance issues in wireless systems, including reduced signal-to-noise ratio (SNR), increased phase noise, and degraded spectral purity. These effects can result in decreased data rates, lower coverage range, and overall poor system performance.

Combating Fractional Spurs

To improve wireless system performance in beyond 5G networks, it is crucial to combat fractional spurs in PLLs. Here are some techniques that can be employed:

1. Loop Filter Design

The design of the loop filter plays a critical role in minimizing fractional spurs. By carefully selecting the loop filter parameters, such as the loop bandwidth and damping factor, the impact of spurs can be reduced. Additionally, advanced filter design techniques, such as fractional-N PLLs and charge pump architectures, can be utilized to further mitigate spurious signals.

2. Reference Frequency Selection

The choice of the PLL reference frequency can also affect the occurrence of fractional spurs. By selecting a reference frequency that minimizes the likelihood of spurious signals, the overall system performance can be improved. This can be achieved through careful frequency planning and analysis of the system requirements.

3. Noise Reduction Techniques

Noise sources within the PLL, such as phase noise and reference spurs, can contribute to the generation of fractional spurs. Implementing noise reduction techniques, such as low-phase-noise voltage-controlled oscillators (VCOs) and high-quality reference sources, can help minimize the impact of these noise sources and reduce the occurrence of spurious signals.

4. System-Level Optimization

Optimizing the overall system architecture and layout can also aid in combating fractional spurs. By carefully considering the placement of components, minimizing parasitic effects, and optimizing the interconnects, the likelihood of spurious signals can be reduced. System-level simulations and analysis can assist in identifying potential sources of spurs and implementing appropriate mitigation strategies.

Conclusion

As beyond 5G wireless systems continue to evolve, combating fractional spurs in PLLs is crucial to ensure optimal system performance. By employing techniques such as loop filter design, reference frequency selection, noise reduction, and system-level optimization, the impact of spurious signals can be minimized, leading to improved data rates, lower latency, and enhanced overall wireless system performance.