【Introduction】Cable TV providers need to be careful when upgrading their networks. They need to meet customer demand for capacity without sacrificing performance and reliability. Many providers are using GaN technology to keep the balance for the following reasons.

The need for speed, capacity, performance and reliability

With the popularity of video, music, gaming and online media content consumption, there is a need for faster cable speeds and higher capacity data transfers. This leaves North American cable operators struggling to enhance their networks to meet such demands without degrading signal integrity and performance. Gallium Nitride (GaN) power amplifier technology has emerged, which has the linearity, thermal characteristics and efficiency required by the market to meet the performance requirements of Hybrid Fiber Coaxial (HFC) and support reliable cable TV operations.

This article is an excerpt from the Qorvo Design Summit webinar series, highlighting significant improvements in industry areas that will enable the next generation of technology.

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Development of Gain Unit Amplification Technology

Over the past 25 years, cable television technologies such as gallium arsenide (GaAs), GaN hybrids, and monolithic microwave integrated circuits (MMICs) have continued to advance, expanding bandwidth and improving system performance to comply with the latest cable data service interface specifications (DOCSIS). GaN devices exceed the necessary specifications for efficiency, linearity and performance to ensure reliable data transmission and signal integrity in HFC networks.

Development of CATV semiconductor Technology

With GaN technology, gain cell performance is improved, and cable multi-system operators (MSOs) can improve linear power output. This brings a number of benefits, not only reducing upgrade costs, but also placing fiber closer to customers for better service. In addition, amplifiers in the network chain can be reduced or eliminated.

Figure 1 compares the relevant properties of commonly used material technologies in CATV gain cell structures. It is evident that GaN provides MSOs with several key system-level advantages.

Figure 1. GaN-based device characteristics compared to other semiconductor technologies.

Improving Linear Power Output with GaN

With the evolution from DOCSIS 3.0, DOCSIS 3.1 to DOCSIS 4.0 (standards supporting downstream spectrum up to 1.8 Ghz), the nonlinear behavior of active power devices presents a major challenge to the industry. Inconsistent linearity can degrade signal quality, create bit errors on digital channels, and sometimes cause entire equipment to fail when demodulating the signal. Using GaN can help improve linearity degradation and help avoid signal quality issues and equipment failures.

Qorvo’s expertise in designing and manufacturing cable TV amplifiers dates back to the early days of the industry. In fact, Qorvo was the first company to introduce a cable gain unit using gallium nitride on silicon carbide (GaN-on-SiC).

GaN, with its superior performance characteristics, is driving a large-scale transition from GaAs to GaN for cable TV applications. The higher output levels, increased durability, and superior thermal performance offered by GaN are key catalysts for this transition.

As cable TV bandwidth continues to expand, engineers and system architects are looking for the right technology for network upgrades. To meet higher bandwidth and data rate demands, linearity must be maintained. Maintaining the linearity of a gain cell or amplifier depends on four factors: semiconductor technology, circuit design, power consumption, and thermal design/performance. GaN offers advantages in these areas, delivering up to 10 W/mm compared to 1 W/mm for typical GaAs designs (see Figure 2).

Advances in Linear Output Power

Figure 2. Comparison of efficiency and composite output power for GaAs, GaN, and Si technologies.

Epilogue

Now, MSOs have a solid choice for capacity needs when upgrading their networks to the new DOCSIS standard. GaN technology provides better data transfer with the necessary characteristics to meet stringent design constraints, and GaN-based amplifiers provide the ideal building blocks for next-generation designs.

Source: Qorvo Semiconductor, Original: Bob Simmers