Millimeter wave (mmWave) frequencies offer significantly higher data rates and wider bandwidth compared to lower-frequency signals. To understand their impact, it is important to consider the complete signal chain between the antenna and the digital baseband.
The new 5G radio standard (5G NR) introduces mmWave frequencies to cellular devices and networks. Unlike sub-6 GHz frequencies, mmWave requires additional RF-to-baseband signal chain components, including specialized transceivers, filters, amplifiers, and converters. For 5G, mmWave frequencies generally range from 24 GHz to 90 GHz, with typical peak usage around 53 GHz. While initially targeted at urban smartphone use for faster data speeds, mmWave is now increasingly deployed in high-density environments such as stadiums, fixed wireless access (FWA) networks, and private 5G networks.
Key Benefits of 5G mmWave
High throughput – 5G mmWave supports large data transfers of up to 10 Gbps with channel bandwidths up to 2 GHz, even without carrier aggregation.
Low latency – Higher data transfer rates between the 5G radio access network and core network enable latency as low as 1 millisecond, compared with 100 milliseconds in LTE networks.
These features make mmWave ideal for applications requiring high-speed data and low latency, including Industrial IoT and high-density broadband deployment.
The 5G mmWave Signal Chain
The radio frequency front-end (RFFE) refers to all components between the antenna and the baseband digital system. It includes the analog-to-digital portion of the receiver and transmitter, supporting both transmit and receive modes. A typical mmWave signal chain includes:
RF ADC and RF DAC
Low-pass filters
Power amplifier (PA)
Digital down and up converters
RF filters
Low-noise amplifier (LNA)
Digital clock generator (CLK)
Phase-locked loop/voltage-controlled oscillator (PLL/VCO) for local oscillation
Switches connecting the antenna to transmit or receive paths
In addition, a beamforming IC (BFIC), or phased array module, distributes the signal from the upconverter into multiple channels. Each channel features independent phase and gain controls, enabling precise beamforming for improved signal strength and coverage.
Transceiver Architecture
An example mmWave transceiver may use an IF interface between baseband and the 24.25–29.5 GHz mmWave band, often employing a 3.5 GHz intermediate frequency (IF). The RFFE manages signal routing between PA and LNA depending on whether the device is transmitting or receiving.
Applications and Deployment
The rollout of 5G mmWave networks benefits both service providers and end users, with key applications in:
Cellular broadband modules
5G communication modules for Industrial Internet of Things (IIoT)
Fixed wireless access
Private enterprise networks
This article focuses on the mmWave aspect of 5G. Future discussions will cover the detailed elements of the mmWave signal chain and their performance optimization.
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