The Adoption and Use of Long-Distance PHY

The Ethernet, which has advanced continuously over the last fifty years, plays an important role in the successful popularization of the Internet. With such advantages as low cost, high transmission speed and the ability to be deployed on a large scale with ease, the Ethernet has become the most popular data transmission solution of today. The conventional Ethernet, however, still has its limitations, one well-known example of which is that an Ethernet cable must not exceed 100 meters in length. This limitation on transmission distance causes a considerable increase in the deployment cost of an Ethernet system that must cover an extensive area.

In view of the above, Realtek launched RTL8201G(R)(I)-VB-CG, a Long-Distance PHY (LDPHY) chip, in 2019 in order to provide customers with more flexible choices in wire speed, transmission distance and transmission medium, and hence with the adaptability to different application scenarios.

■ RTL8201G(R)(I)-VB-CG is a highly integrated Ethernet transceiver that is fully compatible with IEEE standards 802.3 10BASE-T and 100BASE-TX. It offers all the necessary physical layer functions to transmit and receive Ethernet packets over CAT.5 UTP cable. Realtek implements state-of-the-art DSP technology and an analog front end (AFE) on this chip to enable long-distance data transmission and reception over a UTP cable using a proprie­tary LD100 mode. 100BASE-T1 and another proprietary mode LD10 are also implemented for long-distance application over single-pair UTP or coaxial cable (Figure1).

Figure1: Existing coaxial cable deployment: public transportation infrastructure

Product specifications

  • 10BASE-T IEEE 802.3 compatible
  • 100BASE-T1 IEEE 802.3bw compatible
  • 100BASE-TX IEEE 802.3u compatible
  • Proprietary mode LD10/LD100
  • IEEE802az-2010 EEE supported
  • 32-pin MII/RMII QFN package: RTL8201G(I)-VB-CG
  • 24-pin RMII QFN package: RTL8201GR(I)-VB-CG
  • Industrial version: RTL8201G(R)I-VB-CG
Table 1. Realtek PHY solutions for long-distance media converter/extender

Easy Design and Low Cost for Construction

When a single twisted pair is used, RTL8201G(R)(I)-VB-CG allows 100Mbps Ethernet signals to be transmitted over 300 meters and 10Mbps Ethernet signals over 800 meters. In common IP surveillance applications (transmission speed < 100Mbps)(Figure2), the 300-meter transmission distance greatly reduces the difficulty of system design and deployment cost.

Figure2. Long Ethernet cable routing: IP surveillance system in the highway

No Need Change if Using Coaxial 75-5 Cable

The built-in LD10 mode of RTL8201G(R)(I)-VB-CG allows data to be transmitted as far as 1 kilometer at 10Mbps; the 100BASE-T1 mode works equally well by providing a transmission distance of 500 meters (Table 2).As RTL8201G(R)(I)-VB-CG supports 75-5 coaxial cables, a customer can directly upgrade the terminal devices (e.g., IP cameras) in a conventional analog-signal system and continues to use the existing coaxial cable network, without having to deploy Ethernet cables. This helps reduce the cost of system upgrade significantly. RTL8201G(R)I-VB-CG also has an industrial version, whose working temperature ranges from -40° to 85°.

Table 2. Details of the operating modes of RTL8201G(R)(I)-VB-CG

Widely Application Scenarios

Where long-distance transmission is required, RTL8201G(R)(I)-VB-CG is a solution of tremendous value. Its flexible support for Ethernet cables and coaxial cables makes it possible to use the chip in cars, elevators and outdoor applications, where the operating conditions are relatively tough. The chip can be directly designed as part of a terminal device (e.g., switch in factory) (Figure3) or as a media converter/extender solution to overcome the deployment problems of critical scenarios.

Figure3. Long distance Ethernet transmission: switch/converter in the factory

Typical applications (Figure 4-6)

End Products:

  • Long Distance IP camera
  • Long Distance Switch
  • Long Distance PHY Converter/Extender


  • Long Distance IP surveillance system
  • Edge device upgrade on CCTV infrastructure


  • Factory, museum, stadium, airport, harbor, border, automotive
  • Elevator
  • Transportation station
  • Vehicle
Figure 4. Typical applications: Long Distance IP Camera on different scenarios

Figure5. Solution from Realtek: Long Distance IP Camera, Long Distance Switch

Figure6. Solutions from Realtek: Long Distance PHY Converter/Extender


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