CA Technology Drives RF Components to High Integration

The integration of RF front-end antenna switches and low-noise amplifier (LNA) modules jumped. Carrier Aggregation (CA) has become an indispensable technology for next-generation LTE systems. In order to achieve the goal of simultaneously aggregating two to four different frequency bands, taking into account cost, performance, and component size considerations, high integration and adoption of mobile industry processing MIPI antenna switches and low-noise amplifier modules have grown in importance.

Infineon Associate (right), Infineon’s RF and Protection Component/Power Management and Multi-Electronics Division, said that the application of carrier aggregation technology will drive the RF front-end component design towards high integration. On the left is Huang Zhengyu, Infineon’s power management and multi-electronics division manager.

According to Infineon's Associate Professor of RF and Protection Components/Power Management and Diversified Electronics Division, Mai Zhengqi, the number of globally adopted frequency bands in the past 3G era was more than 20, and now they are entering the LTE era, and the number of frequency bands used by telecom operators In total, there are forty, and it is also necessary to take into account the backward compatibility of 4G to 3G systems, which makes the design of mobile communication systems more complicated. Therefore, the main antenna, the diversity antenna (antenna), the antenna switch, the antenna tuning switch, and The use of RF components such as low noise amplifiers will increase substantially.

Taking high-end LTE smart phones as an example, the number of support bands is about 12 to 16. In order to meet the requirements of simultaneous multi-band operation, the device may have to be composed of three main/high/mid-band main antennas respectively. Three-component antenna sets, one to three sets of antenna switches, antenna tuning switches, and low-noise amplifiers constitute the RF front-end system.

Even for low- and mid-range smart phones, in order to increase the sensitivity and linearity of the mobile communication system, the use of diversity antenna designs other than the main antenna and the increased use of antenna switches and antenna tuning switches have become an irresistible trend.

Mai Zhengqi further pointed out that in addition to the multi-frequency multi-mode demand derived from LTE leading to increased RF component usage, another important point to be focused on is carrier aggregation due to LTE-A and FDD/TDD-LTE converged networking. The technology trend will also bring new challenges to the design of RF front-end systems; for example, how to let the switch switch to the correct frequency band and let the antenna tuner when the antenna must receive two to four sets of LTE signals with different aggregation bands at the same time. Adjusting to the most accurate matching circuit to optimize antenna performance and simplifying the number of complex traces has become a severe design challenge.

In fact, highly integrated RF front-end solutions have become an important solution for carrier aggregation applications. Huang Zhengyu, manager of Infineon's Power Management and Diversified Electronics Division, said that the configuration of RF front-end systems will take on a variety of features depending on the end-use market, cost, battery size, and layout design, but it is usually highly integrated. The packaging solution will better meet the needs of carrier aggregation. For example, the two antenna switches are packaged in the same module. Compared with the discrete design solution, the size of the two antennas can be smaller and the two antennas in the module can be compared. The switch operates independently and simultaneously outputs two different aggregated-band signals to the back-end modem module.

On the other hand, high-integration low-noise amplifier modules are also on the rise. For example, Infineon's low-noise amplifier modules can now integrate up to four LTE frequency bands to meet the needs of carrier aggregation applications; The first LNA Multiplexer Module (LMM) has also been introduced. The module integrates a low noise amplifier and antenna switch to achieve the performance of a tri-band low noise amplifier in a smaller package solution. The general-purpose input-output (GPIO) interface design was abandoned and the MIPI interface was adopted, which greatly reduced the number of system wires.

Huang Zhengyu analyzed that with the advent of the carrier aggregation era, the design complexity of RF front-end systems will increase, which will also accelerate the MIPI interface to become the mainstream of RF front-end systems. He disclosed that in the past each RF component had to pass three traces to form the GPIO control interface. In other words, if the RF front-end system had eight antenna switches, at least eight groups of GPIO interfaces must be designed; while the MIPI interface only requires a group of Traces are compatible with all RF components. This not only reduces the number of I/O interfaces and pin counts, but also makes PCB routing easier. As a result, many RF component vendors have accelerated the development of MIPI interface solutions. To further simplify the design complexity of the carrier aggregation RF front-end system.