Large-scale RF integration can reduce mobile phone circuit board area and power consumption
In today’s wireless devices, more than half of the components on the circuit board are analog RF devices, so an effective way to reduce circuit board area and power consumption is to carry out larger-scale RF integration and move towards system-level chip. This article introduces the current status of RF integration and proposes countermeasures and solutions to some of the problems.
A few years ago, the cwhones, which used technology that only supported one or two cellular bands and used the same modulation method, multiple access scheme and protocol in all supported bands. In contrast, today’s new generation of cellular phone designs are much more complex, providing multi-band and multi-mode support, with functions such as Bluetooth personal area network, GPS positioning, and ultra-wideband and TV reception functions have begun to appear. In addition, applications such as games, images, audio and video have become very common in mobile phones.
Wireless phones are becoming a complex device such as the so-called handheld personal entertainment center,
and its development trend continues to bring more challenges to designers. Although the new generation of mobile phones has significantly increased communication processing, application processing, number of RF interfaces and integrated memory capacity compared to voice-only phones, users still expect mobile phones to be smaller, streamlined, low-priced, with large color displays and similar standby and talk time as traditional voice phones. Maintaining the existing form factor and power consumption, while increasing functionality exponentially, while maintaining the overall system cost, all these have presented a lot of challenges to system designers.
Obviously, the problem involves all parts of the entire system design and all wireless communication and entertainment content suppliers.
One area that is particularly effective in reducing circuit board area and power consumption is the RF part of the wireless system design, because in today’s typical mobile phone, more than half of the components on the circuit board are analog RF components, which together occupy 30-40% of the entire circuit board area. Adding RF systems such as Bluetooth, GPS and WLAN will greatly increase the space requirements.
The solution is to carry out greater RF integration and eventually develop into a fully integrated system-level chip.
Some designers put the analog-to-digital converter into the antenna to reduce the total board space required for RF functions. When semiconductor integration technology can integrate more functions in a single device, the number of discrete devices and the board space used to accommodate these devices are reduced accordingly. As the industry moves towards system-level chip integration, designers will continue to discover new technologies to meet the contradiction between higher RF complexity and extended battery life in small wireless devices.
1 Current status of RF integration development
An important development in RF integration occurred about three years ago, when the development of RF technology and digital baseband modems made it possible to replace superheterodyne RF devices with direct down-conversion receivers in wireless mobile phones. Superheterodyne RF devices use multi-stage mixers, filters and multiple voltage-controlled oscillators (VCOs) and have been well used for many years, but the integration of direct conversion RF devices can greatly reduce the total number of GSM RF components. In the late 1990s, a typical single-band superheterodyne RF subsystem, including PA, antenna switch, LDO, small signal RF, and VCTCXO, required about 200 discrete components; today, we can design a direct conversion system with quad-band capabilities, integrating VCO, VCXO, and PLL loop filter, with less than 50 components.
For example, Texas Instruments’ TRF6151 transceiver for GSM (Figure 1) integrates on-chip voltage regulators, VCO and VCO tank, PA power control, PLL loop filter EDGE blocker detection, LNA gain step control, and VCXO.
For designers, advanced integration helps overcome some of the biggest challenges in wireless RF.