In my EDN article entitled A major change in smartphone RF filters and front ends as 5G approaches, I discussed Smartphone filter architectures for the coming 5G standard with regards to LTE carrier aggregation (CA) and beyond, as well as Multiple-In-Multiple-Out (MIMO) designs to increase capacity and data downlink/uplink speeds. This will necessitate multiple frequency bands operating simultaneously through one antenna (That challenge makes designers dizzy).
With RF front-end (RFFE) complexity increasing, the insertion loss and link budgets will increase. Plus, HPUE/Power Class 2 requirements will add more complexity to the designs. Here is what designers need to know in order to design a robust RF front-end for the coming mobile devices.
To get another aspect on this difficult dilemma, I sought out Ben Thomas, director of technical marketing at Qorvo and asked his opinions on the subject regarding what it means for radio frequency (RF) solutions that enable receive and transmit out of handsets. What can we expect for filtering out a constantly increasing set of frequency bands and multiple antennas being added to the phone. How can the next generation of smartphones reach the needed Gigabit speeds?
Mr. Thomas said that Qorvo sees that as 5G approaches, there will be a fundamental shift in how mobile data is being used globally. For an entirely new generation, streaming video is the new baseline for entertainment, information, and much more.
These are several, real-time questions impacting smartphone manufacturers today. Qorvo is helping solve RF complexities for the handset OEMs by addressing several key challenges:
- Meeting rapidly changing standards including carrier aggregation and MIMO
- Balancing size with performance
- Enabling CA combinations with filters and multiplexers
- Offering RF Front End solution option for premium and mid-tier smartphones
Qorvo has a 2017 RF Fusion Solution now that consists of multiple modules which will enable global CA-band coverage in a small form factor for the industry’s flagship smartphones. See Figure 1.
Figure 1: 2017 RF Fusion LTE Solution (Image courtesy of Qorvo)
Of course, they have a roadmap so far that extends into 2018 (When the Korean Olympics will showcase many early 5G architectures) See Figure 2.
Figure 2: RF Fusion roadmap into 2018 (Image courtesy of Qorvo)
The challenge going forward is that the smartphone arena has a few categories with different design goals and priorities. Two important categories are flagship phones that are designed for super-regional/global usage and mid-tier and entry-level phones for regional usage.
In a Super-regional/global capable phone, there will need to be a high level of RFFE integration. Many bands are needed here along with uplink and downlink CA combinations for different performance needs. These small, sleek form factor handsets need to maximize the use of space to also house batteries and multiple antennas as an added challenge. Qorvo has an RF Fusion solution for this class of phones, that combines all the necessary transmit/receive functionality demanded, including major frequency bands. This solution has three modular solutions that cover high, mid, and low-band regions of the spectrum. The modules incorporate power amplifiers (PAs), switches, and filters. Figure 3 shows an example of the high-band module block diagram. Electronic Products showed a teardown of the Samsung Galaxy S7 with the QM78064 inside. See the Bill of Materials (BOM) here.
Figure 3: Qorvo’s RF Fusion #QM78064 high-band module that supports FDD-LTE (with an integrated Band 7 duplexer) and TDD-LTE (Bands 40 and 41), plus it has a wideband B41 LowDrift Bulk Acoustic Wave (BAW) filter that enables 20 MHz + 20 MHz uplink CA. There is also an antenna switch and can support Envelope Tracking (ET) and Average Power Tracking (APT) to increase efficiency of the transmit Power Amplifier which improves power efficiency and helps extend battery life. (Image courtesy of Qorvo)