Three Factors Reshaping RF Transceivers in the 5G Era

June 3, 2019 Majeed Ahmad

Radio frequency (RF) transceivers, an intrinsic part of the wireless design, are going through a radical makeover in the 5G arena. That’s mainly because the need for higher capacity enabled by new technologies like massive MIMO, beamforming, and multiband communication is leading to the creation of highly integrated radio solutions.

However, RF transceivers, which facilitate receive and transmit paths in a single device, must raise the integration bar within the practical size, weight, power consumption, and cost constraints. And that is leading to a rapid shift in the RF architecture.

Below are the key highlights of the evolution of RF transceivers in the 5G era. And it starts with how RF transceivers are moving to wider bandwidths and higher speeds.

1. Wider Bandwidth Signals

The advent of 5G is all about efficient delivery of higher capacity through new radio advancements such as MIMO, beamforming, and high-density antenna arrays. Here, RF transceivers are contributing to this wireless dynamo by offering wider frequency range that provides engineers with the flexibility to design applications across a broad frequency swath.

Take, for instance, the ADRV9009 RF transceiver (Figure 1) from Analog Devices Inc. It offers the signal bandwidths of up to 200 MHz — twice than previous generation transceiver chips — to accommodate rigorous antenna density and expanded network capacity requirements of emerging 5G wireless infrastructure equipment.

Figure 1: ADI’s wide bandwidth RF transceiver supports 5G wireless while sustaining the 2G, 3G, and 4G cellular coverage.

The RF transceiver is tunable over a range of 75 MHz to 6 GHz to support 2G, 3G, 4G, and 5G wireless networks, and it works across all band and power variants. It’s a single-chip solution based on the time division duplex (TDD) technology and it accommodates both wideband services such as 5G and narrowband applications like military communications and signal intelligence.

Likewise, MaxLinear’s quad-RF transceivers are optimized for active antenna system (AAS) to facilitate massive MIMO applications. The MxL1500 transceiver, optimized for low-power designs, takes signal bandwidths up to 200 MHz, while the MxL1600 transceiver delivers signal bandwidths of up to 400 MHz.

An RF transceiver’s ability to offer wider frequency range and higher instantaneous bandwidth is intertwined with highly integrated radio solutions that can assimilate more components as well as shrink the chip size. The next section covers the integration aspects of RF transceivers.

2. Highly Integrated Solutions

In the 5G era, we see a transition from band-specific designs incorporating a lot of discrete components to single-chip transceiver solutions. These single-chip devices are employing innovative RF architectures to take integration to a whole new level.

For a start, these single-chip transceivers are integrating the major RF building blocks such as I/Q modulator, voltage-controlled oscillator (VCO), power amplifier (PA), low noise amplifier (LNA), programmable gain amplifier (PGA), and SPI control interface.

Next, RF transceivers like MaxLinear’s MxL1500 and MxL1600 are able to pack four transmitters, four receivers and up to two feedback receivers in a single device. That, according to MaxLinear, lowers the power consumption by up to 50 percent.

The dual- and quad-channel RF-sampling transceivers from Texas Instruments also provide a case study on how integration is advancing in modern RF transceiver chips. The dual-channel AFE7422 and quad-channel AFE7444 transceivers allow wireless designers to support up to eight antennae and 16 RF bands with a single chip.

These transceivers enable engineers to directly sample input frequencies into C-band without the need for additional frequency conversion stages (Figure 2). That, in turn, eliminates local oscillators, mixers, amplifiers, and filters. It also optimizes transceiver proximity to the antenna and thus facilitates digital beamforming in high-frequency and high-density antenna arrays.

Figure 2: The fact that TI’s quad-channel AFE7444 device bypasses the additional frequency conversion stages leads to significant improvement in high-channel-count systems.

Furthermore, TI’s RF-sampling transceivers integrate four analog-to-digital converters (ADCs) and four digital-to-analog converters (DACs) in a single chip, and that leads to a significant reduction in the design cycle. As a result, engineers end up devoting a lot less time than they otherwise would have spent in testing the discrete RF components.

3. The Incredibly Shrinking RF Transceivers

The growing impact of integration and miniaturization in RF transceivers leads to another crucial design advantage: elimination of discrete components. The highly integrated transceivers without external RF discrete lower overall cost, shrink footprint and create flexibility for board placement.

For example, TI’s RF-sampling transceivers, measuring 17 mm by 17 mm, claim to save 75 percent of board space when compared to discrete RF-sampling data converters. Likewise, ADI’s ADRV9009 RF transceiver replaces 20 components, cuts power consumption in half and shrinks package size by 60 percent.

Figure 3: The ADRV9009 system-on-chip (SoC) radio solution from ADI simplifies digital beamforming design by handling local oscillator (LO) synchronization on-chip, and thus eliminates the need for external LOs.

The ADRV9009 transceiver chip (Figure 3) integrates auxiliary functions, including ADCs, DACs, general-purpose inputs/outputs (GPIOs) for the power amplifier, and RF front-end control. It also integrates synthesizers and digital signal processing (DSP) functions.

The RF transceiver chips outlined in this article demonstrate how these semiconductor radio solutions are shrinking in physical footprint while they are significantly expanding in terms of functionality. Moreover, these single-chip solutions come along with software tools, reference designs, and evaluation and prototyping platforms.

In other words, they are full radio solutions.

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