5G Document Folder

| 36 over the air. For example, techniques such as massive multiple-input, multiple-output (MIMO) that rely on digital signal processing (DSP) still need to convert the analog signal to a digital form. Fortunately, major advances are being made to address this need from lower frequencies to the microwave, and millimeter-wave regions, with semiconductors that generate and receive RF signals to and from the antennas. RF Output Power For the past two decades, base station RF power amplifiers (PAs) have used lateral double-diffused metal- oxide semiconductor (LDMOS) field-effect transistors to generate RF power in macro-base stations. This technology has advanced dramatically over the years with respect to the amount of power a single device can generate (currently, about 2 kilowatts [kW]) and use efficiently, beating every other potential competitor. But, LDMOS has a maximum useful operating frequency of about 4 gigahertz (GHz), which eliminates its use at most of the new frequencies proposed for 5G networks. The technology that will take the mantle is gallium nitride (GaN), which, in the less than 15 years it's been commercially available, has cemented its place as the next big thing in RF power. For example, a GaN semiconductor die can produce 10 times the RF power output per unit of die than gallium arsenide (GaAs), with higher efficiency, higher-voltage operation, and superior thermal characteristics. GaN on silicon carbide (SiC) substrates offers better performance than GaN on silicon substrates, but it also costs more. This means that the latter will find a home in cost- critical small cells, where it will compete with GaAs, the predominant power semiconductor technology that has been used in smartphones for many years. At millimeter-wave frequencies, where high RF output is difficult to achieve in a solid-state device, silicon germanium (SiGe), complementary metal-oxide semiconductor (CMOS), and GaAs will be the key technologies. All these technologies, except LDMOS, will also be important for either RF power generation or receiving applications, such as low-noise amplifiers (LNAs). RF Front Ends: Packaging Functional Integration The 5G infrastructure will require that manufacturers of microwave and millimeter-wave devices increase their functional integration to reduce costs, complexity, and size and meet the needs of small cell base stations (as well as end-user devices). Packaging technology will be an essential ingredient in achieving this goal because although 4G increased the number of bands that a radio must accommodate to about 30, 5G will increase this number to 40 and perhaps more. Accommodating all these bands in a single device is unlikely, especially considering each band has different characteristics and thus requires different technologies. Nonetheless, each band segment, from sub-1GHz to millimeter wavelengths, must be as highly integrated as possible. To create these highly integrated RF devices, manufacturers of RF front ends (RFFEs) are taking a variety of approaches. Let's see what approaches Analog Devices, Skyworks Solutions, and Qorvo are taking to fabricate products that accomplish this feat. Analog Devices ® Analog Devices is producing transceivers within its RadioVerse™ family (which is dedicated to accommodating all 5G applications from sub-1GHz to 6GHz). The three devices in the family are housed in 10 x 10mm packages and target picocells to distributed antenna systems and IoT gateways. They also operate from 325 megahertz (MHz) to 3.8GHz. Analog Devices' AD9361 and AD9363 are highly integrated devices that include dual transceivers with four outputs, fractional N synthesizers, and 12-bit digital-to-analog and analog-to-digital converters (DACs/ADCs). They also have a tunable channel bandwidth up to 20MHz. Six differential inputs or 12 single-ended receive inputs are available along with CMOS and low-voltage differential signaling interfaces. The AD9364 covers 70MHz to 6GHz with a tunable bandwidth from 700 kilohertz (kHz) to 56MHz, and it's designed for use in base stations from 3G onward as well as in point-to-point microwave links. Among the other products in Analog Devices' portfolio is the ADRV9009, an integrated transceiver with dual transmitters and receivers as well as DSP functions. It serves 3G through 5G macrocells (and other applications) and covers 75MHz to 6GHz with a maximum channel bandwidth of 450MHz. Skyworks ® The goal of Skyworks Solutions' recently announced platform, called Sky5™, is to serve the transmit and receive sections of the low-band, mid-band, high-band, and ultra-high-band frequencies of 5G. Sky5 accomplishes [ C O N T ' D O N N E X T P A G E ]

• Cover