Leaders' Ambitions

The RF Device Division works on RF devices for wireless communication. These devices include filters, power amplifiers (PAs) , low-noise amplifiers (LNAs) , and radio frequency (RF) switches. In addition, we have modules that integrate coils and capacitors in substrates made of LTCC (low temperature co-fired ceramics) . Unlike conventional ceramics that are fired at high temperatures above 1,500°C, the Murata LTCC is fired at approximately 900°C. This is because the LTCC ceramic material is prepared by mixing glass components with the conventional ceramic material, which makes it possible to use internal wiring made of silver and copper, conductors with low electrical resistance. Modules are produced by combining LTCC substrates with SAW (surface acoustic wave) filters, PAs, and LNAs.

These products find use mainly in smartphones and, on average, a single smartphone integrates seven to eight switches, four to five PAs, and three LNAs. As typified by SAW filters, surface wave filters are used to extract signals with specific frequencies and eliminate the others. As such they are now indispensable for smartphones. Not only does an increase in the production and shipment of smartphones generate growing demand for these filters. At the same time, the number installed per terminal is also on the rise, with some phones featuring nearly 50.

The 5G standards are now taking shape in the world of communications. RF technologies will remain in great demand. At present they use transmission frequencies of 700 MHz to 2.5 GHz as well as 3.5 GHz. By contrast, the 5G technology will allow the use of 5 to 6 GHz, 10 to 20 GHz, and even 60 GHz.

Accurate microfabrication is the greatest challenge in producing RF devices. With SAW filters, the key among this product group, the challenge translates into making filter size smaller and making the electrodes finer. The higher the transmission frequency, the more difficult it will be to adjust, and so it will be necessary to improve the characteristics. We are asking ourselves many questions: will we need to change the device structure per se? How will we be able to reduce resistance? The 20 GHz band, which will likely be used in the future, is largely unknown. As far as communication between base stations is concerned, however, some systems already use the band, and in fact Murata has the expertise to work on the technology.

More new technologies will be required as the frequency band expands. Future smartphones will use an even greater number of components to cover new frequency bands. Previously, smartphones used only a limited number of frequency bands. As further bands are added, the limited space available in a mobile terminal will be required to house even more components. The modularization of devices and dense mounting of components will present an inevitable challenge: an increase in temperature within the terminal due to heat emissions from the substrate and reduced distances to heat-generating components. Coping with the internal temperature rise now makes it necessary to develop components aimed at reducing frequency shifts caused by temperature changes.

BAW (bulk acoustic wave) filters represent a separate technology from SAW filters. Made of silicon wafers, BAW filters come into their own in applications required to eliminate interfering waves caused by narrow frequency intervals. A typical example is FBARs (film bulk acoustic resonators) engineered by U.S. semiconductor manufacturers. BAW filters are considered as having the advantage as higher frequencies are used and frequency bands are set closer to each other. Against this backdrop, Murata has established a new SAW technology that expands the range of frequencies covered thereby covering most of the region accommodated by BAW and FBAR technologies: It is called TC (temperature compensated)-SAW. As marked by this development, we never cease to develop Murata technology further, expanding its scope step-by-step.

In recent years we made a couple of merger and acquisition deals in rapid succession. In March 2012, Murata purchased the PA business of Renesas Electronics Corporation. Most of the PAs Murata had commercialized before were for Wi-Fi®, and so we wanted cellular PAs that could be used in smartphones and feature phones. We chose to purchase such technology after discussing that it was better to incorporate advanced technology owned by a competitor than to try to develop our current technology further.

In December 2014 Murata also completed the purchase of U.S.-based Peregrine Semiconductor Corp. Peregrine owns cutting-edge technology for RF switches, components mounted around the smartphone antenna. It had been doing a lot of business with Murata, posting some 70% of net sales from its transactions with us. The Peregrine purchase, costing us some 49 billion yen, was one of the biggest deals of its kind in Murata history.

Peregrine has a unique RF switch technology based on CMOS. CMOS was believed to be unable to deliver characteristics for RF communication. However, the U.S. company uses it to achieve excellent characteristics. Murata has worked with them for more than a decade, and we understand the advantage of their technology.

Exchanging electric waves using a smartphone requires three kinds of key components around the antenna: switches select either among signals in several FDD (frequency division duplex) frequency bands to establish connection with the desired duplexer or between transmitted and received signals by TDD (time division duplex) to connect them to the transmission and reception circuits; PAs are used to amplify signals; and SAW filters extract from electric waves only the signals having the target frequency. Murata has SAW filters that are said to win the highest market share. By adding Renesas PAs and Peregrine RF switches Murata now has all three component groups within its Group. This allows us to design and develop the key devices comprising the smartphone RF circuit internally and ensure integrated production and delivery. It in turn allows us to strengthen our product portfolio further so we can meet customer requests quickly. What’s more, if we produce devices in-house and modularize them, we will be able to keep ourselves updated on technological trends. These purchases give us a great advantage.

Around 2007, we worked with leading engineers to conduct an in-house study as to which communication technologies we would need in a decade. We concluded that mobile phones would process increasing data traffic, causing a shortage of available channels. To cope, an increasing number of frequency bands would be used. While this would lead to an increase in the number of filters used per phone, the downsizing of phones would reach the limit in terms of the number of devices installed in a phone. An increase in the number of devices per terminal could lead to a hike in terminal prices, even causing the market to shrink. The publication of cognitive radio studies in the academy also prompted us to work on technologies that superseded and/or denied those we owned.

Through this process, we generated a new idea of making it possible to tune a filter to cover a certain range of frequencies. Instead of using different filters for different frequencies, this tunable filter concept consists in tuning the filter to set the range of frequencies at which signals are to be passed. If this comes true, it will be possible to reduce the number of components required per terminal, achieve cost reductions, and resolve the problem of limited mounting space. A possible drawback that came to mind was that it could reduce sales of Murata products. In considering the future potential of the tunable filter technology, we had no choice but to study its possibility.

We made various examinations including feasibility studies to see what kind of technologies we would be able to use for development and what the goal was in technical terms. Finally, we have managed to mass-produce and ship the initial product this year.