Two key challenges to LTE mobile phones: RF MEMS and software radio

With the advent of the era of LTE multi-frequency multi-mode smartphones, a new generation of smart phones requires the support of LTE mode and corresponding working frequency bands based on 2G and 3G modes, and realizes the working frequency band of international roaming. The total number of frequency bands is close to 40. The rapid increase of the frequency band causes the internal radio frequency (RF) antenna size and power consumption to be too large. How to reduce the number and size of the antenna and enhance the signal receiving performance and bandwidth is a problem faced by current engineers. RF engineers are placing higher demands on RF front-end devices, prompting RF semiconductor manufacturers to accelerate the development of innovative RF technologies and solutions, including RF MEMS and software-defined radio (SDR), antenna frequency adjustment and other emerging technologies, which have been accepted by terminal equipment manufacturers. attention.

RF MEMS technology improves handset antenna performance and saves costs

As the industry's RF technology requirements increase, Qualcomm, MediaTek and other chip manufacturers began to actively strengthen the RF solution, Qualcomm is the first to introduce the industry's first CMOS power amplifier (PA) to improve RF performance and cost. Since the chip manufacturer's RF solution has the advantages of signal enhancement and noise cancellation on the processor side, the effect on optimizing the size and transmission power of the RF antenna is still very limited. The industry has begun to pay attention to RF products using MEMS technology.

RF MEMS is a research hotspot in the field of MEMS in recent years. It is based on a mechanical resonant structure. As long as the internal diaphragm distance is changed, the capacitance flow can be changed. The external capacitors and switches and other components can be eliminated, and the overall power consumption and volume of the antenna can be alleviated. In addition, it has programmable capabilities to support software-defined radio (SDR) functions, and implements antenna frequency adjustment, adjustable impedance matching and other control schemes to help simplify RF front-end module (FEM) design, enhance signal reception performance, bandwidth, and reduce antennas. Quantity. This achieves on-chip high integration of the RF system, eliminates parasitic losses caused by discrete components, and truly achieves high cohesion and low coupling of the system, which can significantly improve system performance.

Dennis Yost, president of Cavindish KineTIcs, a manufacturer and manufacturer of radio frequency micro-electro-mechanical systems (MEMS), said that as the frequency band of smart phones continues to increase, how to improve the performance of RF antennas without affecting system footprint and power consumption has become an RF device. And the focus of product development by mobile phone manufacturers has led to a new round of RF technology revolution, which brings new opportunities for RF MEMS technology that excels in both size and performance.

Yost further introduced that LTE mobile phones using Cavendish KineTIcs RF MEMS are expected to be launched in the near future. Currently, Cavendish KineTIcs is working closely with a number of mobile phone manufacturers to initially lock high-end LTE multi-frequency multi-mode mobile phone applications. After the production economy scale, it will enter the low-end mobile phone market.

Yost expects RF MEMS technology to grow rapidly in 2014-2016, including power amplifiers, filters and duplexers for RF front-end modules that can be dynamically tuned for greater efficiency; and because of RF MEMS compatibility The CMOS process supports digital interfaces and may be further integrated with logic chips in the future to enable higher integration mobile phone system solutions. At the same time, RF MEMS reduces the cost of peripheral devices, the overall bill of materials (BOM) cost is lower than the traditional RF design, and can increase the transmission efficiency by 35% on average in various LTE bands. RF MEMS will become the next 5-10 years of mobile phone design. One of the key technologies in the process.

The industry expects the evolution of RF MEMS technology in the next four years

Software Radio (SDR) technology is increasingly mature and will be stationed in LTE mobile phones

Differences in national spectrum planning and the deployment of FDD or TDD LTE networks by telecom operators have complicated the demand for mobile antenna functions. In addition to the emerging RF technology, chip vendors and system vendors are beginning to adopt increasingly mature SDR technologies. They hope to automatically detect and switch to the best LTE frequency band in the user's location through software programming functions, with minimal RF hardware changes. Optimize phone performance.

NVIDIA has been the first to introduce LTE software-defined modems in Tegra 4i, and the first shot of SDR technology in mobile RF applications. At least 20 other processor manufacturers plan to adopt SDR technology to help system manufacturers improve. Size and power consumption of LTE mobile phone antennas. Perhaps SDR technology will be one of the key drivers for accelerating the launch of LTE handsets and enabling global roaming.

Chris Rowen, founder of microprocessor manufacturer Tensilica, said that with the addition of MIMO and Carrier AggregaTIon functions to LTE handsets, the performance requirements of the antenna will be greatly improved. The low-power, small-size design will use SDR technology to develop a specific baseband RF subsystem or enhanced receiver (Turbo Receiver) to meet the design requirements of LTE and LTE-Advanced.

Mobile phone manufacturers and technical departments are usually very cautious in evaluating replacement designs and devices to avoid increasing the risk of investment and product launch. In recent years, traditional RF manufacturers have also actively developed innovative RF technologies to cope with the challenges of multi-mode and multi-frequency. As a new technology for terminal applications, RF MEMS and SDR require a long process for terminal manufacturers and design engineers to fully accept. However, many advantages of MEMS and SDR technologies will become one of the main reference technologies for LTE and LTE-Advanced multi-frequency multi-mode mobile phones.