5G Remote Radio Head (RRH)

Component parts of a 5G Remote Radio Head:

What’s in a 5G Remote Radio Head (RRH) ?

A 5G Remote Radio Head (RRH) comprises several key component parts. Here we look at some of the key technologies involved

5G Band n77 Remote Radio Head (RRH)
5G Band n77 Remote Radio Head (RRH)

Remote Radio Head (RRH) Transceiver, (TRX)

In a modern RRH The Transceiver module may be a single high density PCB containing high speed logic, RF, slow speed analogue and management functions.

The RF processing stages will include complex technologies such as Digital Predistortion (DPD) and Crest Factor Reduction (CFR) which are key to ensure high fidelity of transmitted signals across the airside interface.

The high speed logic may be implemented in a Field Programmable Gate Array (FPGA).

High speed interfaces may include CPRI and/or 10Gbps Ethernet (IP) eCPRI interfaces. More modern Open RAN (ORAN) and Virtualised RAN (VRAN) networks require Ethernet interfaces and more complexity inside the RRH.

Lower speed interfaces may be used to control antenna arrays and other functions.

Front End Module (FEM)

An FEM is used in TDD variants as a highly integrated module. The Front End Module (FEM) contains the following key elements:

  • Power Amplifier (PA)
  • Low Noise Amplifier (LNA)
  • Transmit-Receive switch

FEM Model variants used in Remote Radio Heads to cover different frequency bands and power levels. Please note this is only a partial list of examples:

EWA1057: 2496 – 2690 MHz, 2x20W (Watts output power)

EWA1054: 2300 – 2400 MHz 2x5W (Watts output power)

EWA1056: 2496 – 2690 MHz, 2x5W (Watts output power)

EWA1055: 2300 – 2400 MHz, 2x20W ((Watts output power)

EWA1053: 3400 – 3700 MHz, 2x5W (Watts output power)

EWA1051: 3800 – 4200 MHz, 2x1W (Watts output power)

Power Amplifier (PA)

The Power Amplifier takes signals from the Transceiver (TRX) and boosts to high power levels needed for over-the-air transmission. The output power may vary from 100mW up to 80W per chain (channel) depending on the specific model and application.

Low Noise Amplifier (LNA)

The Low Noise Amplifier (LNA) takes low level input signals from the antenna and boosts them to suitable levels to feed to the Transceiver (TRX) module. The LNA must be suitable shielded to prevent unwanted signals entering, including from other items within the RRH.

RF Duplexer or Filter

Depending whether the RRH is being used in FDD or TDD mode, an RF Duplexer or Filter is used. TDD units feature a filter, and FDD units feature a Diplexer

This RF stage is key to remove unwanted harmonics from the transmission, and also block any unwanted signals from adjacent bands entering the sensitive RF receiver

DC-DC Power Supply (PSU)

The DC-DC Power Supply (PSU) takes input power (typically 36-72V, nominally 48V DC) and converts to smooth, stable power voltage rails to power the key items within the Remote Radio Head.

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