Bringing 5G Back to the Hardware: An Overview of RF Front-End Modules

The advent 5G presents a myriad of new challenges, two of which stand out for design engineers.

One is that a 5G device needs to weigh about a quarter of a pound to sit in a consumer's pocket and instantaneously switch operation between multiple frequency bands. The other concerns mmWave bands, which extend between 24 GHz to 300 GHz—though 5G will reportedly operate within the range of 24 GHz to 100 GHz, according to Accton.

Yole Développement (Yole) and Systems Plus Consulting recently released a report that suggests that systems in a package (SiP) may be a solution to some of these challenges. In the report, the research companies explore specifically how RF front-end modules can successfully integrate the amplifiers, switches, and filters necessary for 5G use cases. 

Moving forward, Yole sees antennas, too, as an integral part of the package. All these functions will need to function in concert within ever smaller patches of board space. As such, Yole envisions “highly integrated products with optimized cost, size, and performance.”

 

RF front-end structure for 5G mobile. Image (modified) used courtesy of Yole Développement

 

This conversation on RF-front end SiP highlights the hardware aspects of 5G that actually concern design engineers. To continue the discussion, we'll review some of the key producers of front-end modules in the market and the technology pertinent for circuit boards headed for 5G applications.

 

The Players

Yole describes Qorvo, Broadcom, Skyworks Solutions, and Murata as the prime integrated device manufacturers (IDMS) who will provide the basis of the RF front-end SiPs. The SiP assembly will be tasked out to outsourced semiconductor assembly and test (OSAT) companies who specialize in such work.

Other manufacturers of 5G hardware include Qualcomm and Samsung, which Yole claims are the only suppliers that provide complete 5G solutions, including modems, antennas, and application processors. Here's a closer look at the specific RF front-end technology coming out of these key players.

 

Qorvo

Qorvo has actual 5G mmWave front-end modules in production. Note that they are meant for base stations and terminals. These include:

• The QPF4001 for 26 to 30 GHz
• The QPF4005 for 27 to 40.5 GHz
• The QPF4006 for 37 to 40.5 GHz
• The QPF4010 for 24.25 to 27.5 GHz

The first three are GaN-based, while the QPF4010 is GaAs-based.

 

Broadcom

In a recent press release, Broadcom asserted that they had completed the industry's first end-to-end 5G mobile network switch portfolio. Broadcom is also involved in 5G-HD enterprise Wi-Fi. It has announced the BCM43465, supporting 4x4 11ac multi-user, multiple inputs, multiple outputs (MU-MIMO), which operates in the range of 2.4/5 GHz.

 

Skyworks Solutions

Skyworks Solutions claims that its Sky5 Ultra is a completely agnostic solution enabling global 5G coverage. The platform employs DSBGA packaging for a small footprint and includes notable low-power requirements. 

As an example, the company’s SKY5-5501-11 is a 5 GHz front-end module incorporating a low-noise amplifier (LNA). In a tiny 1.7 mm x 2.1 mm x 0.7 mm package, the device supports the 5.15 GHz to 5.925 GHz band.

 

Block diagram of the SKY5-5501-11. Image used courtesy of Skyworks Solutions 

 

The unit supports 5G WLAN as well as licensed assisted access (LAA) systems. The supply voltage is 3.7 V, and the receive gain and receive bypass loss are 12.5 dB and 8.5 dB, respectively.

 

Murata

As one of the top leaders in front-end technology, Murata acknowledges the challenges of RF technology as frequencies rise to 20 GHz. The company's RF Device Division currently offers a range of products for wireless communication, including filters, power amplifiers, low-noise amplifiers, RF switches, and modules integrating coils and capacitors in low-temperature co-fired ceramic substrates.

 

Murata’s front-end modules. Image used courtesy of Murata

 

But there are many unknowns associated with the 20 GHz band, and Murata acknowledges these questions: "We are asking ourselves many questions: will we need to change the device structure per se? How will we be able to reduce resistance?"

Still, Murata feels that at least with communication between base stations, they have the tools to work on 5G technology since some systems already use the band.

Perhaps one of these basic technologies that will help Murata make that 5G leap is the PAMid, an integrated module that supposedly contains an “entire RF transceiver function."

 

Murata’s PAMid. Image (modified) used courtesy of Murata

 

However, the block diagram indicates than an LNA and RFIC are not included in the module.

 

Conclusion

Even for older regimes like 4G, there was, and is, a lot to be packed into the RF front-end module. The situation is more critical in the sub-6-GHz portion of 5G. Even here, as Yole points out,  designers will need “packaging innovations like closer placement of components, double-sided mounting, conformal/ compartmental shielding, high accuracy and high-speed SMT.”

And that’s only for the sub-6-GHz portion of 5G. The real “magic” of 5G, the vast reduction in latency and the superfast downloads, only occur in the mmWave bands.

 

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With all the buzz about 5G, what parts of the actual 5G hardware do you care to learn more about? Share your thoughts in the comments below.