By utilizing cutting-edge semiconductors that offer improved performance and efficiency, such as GaN-based RF power ICs, 5G problems can be overcome.
A substantial number of new RF characteristics brought about by 5G technology need to be integrated in mobile networks while taking into account strict board space and power consumption limitations. Wide-bandgap (WBG) semiconductors, which can provide notable increases in terms of both power density and efficiency compared with conventional silicon-based RF power ICs, have been used by RF designers to satisfy these increasingly demanding criteria.
In comparison to earlier deployed infrastructures, the fifth-generation mobile network offers services with more bandwidth and reduced latency, necessitating the use of more powerful and effective power sources. While silicon still performs admirably at lower frequencies, WBG semiconductors like silicon carbide (SiC) and gallium nitride (Gan) power ICs are better suited for applications above 6 GHz and millimeter waves.
5G RF challenges
Although 5G technology increases bandwidth, using parts of the spectrum with higher frequencies inevitably leads to problems with signal attenuation. The signal level, or the sum of the transmitter power, the number of antennas, and the number of cells, can be increased to make up for a lower signal-to-noise ratio caused by a higher bandwidth. However, the market demands products with the smallest feasible form factor, price, and power usage. As a result, RF system designers must contend with both the technical difficulties required for 5G implementation and the limitations set by private network operators.
Power amplifiers present a substantial additional difficulty (PAs). The 256-quadrature amplitude-modulation (QAM) system with signals that offer a high peak-to-average-peak ratio is used by the 5G network to achieve great efficiency in the spectral range (PAPR). High PAPR is essential because it causes the power amplifier to enter the non-linear region, which causes distortion and interference. When operating at middle power levels, an amplifier often has low efficiency if it has been intended to work effectively and linearly at peak levels.
Using cutting-edge materials like WBGs and specific design solutions for this kind of radio application, including Doherty amplifiers, it is possible to solve the obstacles faced by 5G. The latter greatly improves the linearity and efficiency of the PA by incorporating two amplifier circuits that can handle signals of various power levels. Additionally, Doherty amplifiers and digital pre-distortion circuits can be used to further linearize the power source.
Technologies for power devices
Currently, three key technologies—lateral double-diffused metal oxide semiconductors (LDMOS), gallium arsenide (GaAs), and gaN—can provide the high level of performance needed for 5G.
LDMOS, which was first developed in the 1970s to raise the breakdown voltage of power MOSFETs, quickly outperformed bipolar transistors as a technology, and in the 1990s it was the industry standard for RF high-power devices. Although components made of WBG materials are replacing LDMOS devices, which are easier and less expensive to produce with current production techniques, they are still anticipated to be mostly employed for lower band deployment in the future (frequencies up to 2 GHz). GaN and LDMOS will therefore coexist in 5G systems.
GaAs-based power devices as well as, more recently, Gan-on-Si and Gan-on-Sic devices, have grown in popularity in RF applications due to their ability to meet the demands of low power consumption, small form factor, and better thermal management. The switching frequency, losses, power density, and thermal management of these compound materials are all significantly better than those of conventional silicon-based semiconductors.
GaN-on-SiC is mostly used for the new 5G active antenna radios because of its high thermal conductivity. Due to its non-standard semiconductor processing and propensity for faults during the production process, it is one of the most expensive materials for RF applications. Gan-on-Si, which can be made in 8-inch fabs, has a lesser performance than Gan-on-Sic but a higher yield.
RF Power ICs
A selection of RF power ICs appropriate for 5G applications is provided here. A variety of Gan and Gan-on-Sic devices are among them.
A new series of 32T32R discrete solutions from NXP, which enables lighter and smaller 5G base stations for simple deployment in urban and suburban regions, was recently introduced. The new series, which expands the range of discrete power amplifier options for 64T64R radios, is based on NXP’s most recent generation of GaN technology and supports all cellular frequency bands from 2.3 to 4.0 GHz. Massive MIMO coverage can be extended into less populated urban and suburban regions by deploying 32 Rx/Tx antennas rather than 64, offering a more economical alternative.
The 32 power amplifiers in the new 32T32R solutions, which supply double the power in the same package as their predecessor solutions, make a smaller, lighter 5G solution possible. Network operators can grow quickly across frequency and power levels because to the pin compatibility. The 32T32R device, made at NXP’s new Gac fab in Arizona, includes driver and final-stage transistors based on NXP’s highly linearizable RF Gac technology, providing 10-W average output power to the antenna (targeted 320-W radio units)
A example lineup is depicted in Figure 1, where the A5G26S008N 27-dBm RF power Gan transistor, serving as a driver, is placed before the A5G26H110N 15-W asymmetrical Doherty RF power Gan transistor, covering the frequency range between 2,496 and 2,690 MHz
Power amplifiers, switches, phase shifters, integrated modules, and other high-performance discrete RF devices are just a few of the RF connectivity solutions that Qorvo offers for both stationary and mobile applications. A Doherty power amplifier module (PAM) aimed at sub-6-GHz 5G applications is the QPA3908, for instance. Based on GaN technology, this PAM achieves great performance in a small footprint, allowing active antenna solutions like massive MIMO base stations and O-RAN networks to be smaller and lighter.
While the QPA3810 (Figure 2) serves applications in European markets with an operating frequency range of 3.4-3.8 GHz, the QPA3908 (Figure 2) covers U.S. C-band applications with an operating frequency range of 3.7-3.98 GHz. Both modules achieve great linearity, are input/output matched at 50, have a drain voltage of 48 V, and only need a few more parts. The gadget has a Doherty final stage with an average output power of 8 W and a driver PA.
The power amplifier module, which is offered in an 8 mm by 10 mm size, is fully constructed and doesn’t need any more fine tuning. When opposed to a method that uses many discrete power amplifiers, this one simplifies the architecture of 5G networks and cuts down on design time.
Pallets, modules, monolithic microwave integrated circuits (MMICs), RF power devices, and other electronic components are all readily available from Amplicon in both LDMOS and Gac technologies. An asymmetric Doherty power transistor for base station and multi-carrier applications that may operate at frequencies between 2,300 and 2,700 MHz is the C4H27W400AV (Figure 3). This high-efficiency device uses ground-breaking Gac technology to produce 400-W output power, good digital pre-distortion performance, and decreased output capacitance for enhanced Doherty application performance. The DFM6 (SOT1275-1) package and internal matching of the C4H27W400AV make it simple to utilize.
Wolfs peed Inc.
Gan is the perfect choice for meeting the needs of 5G NR because of its inherent high operating frequency and broader bandwidth capabilities. Gan-on-Sic has additional advantages like better efficiency and power density that make it useful in the sub-6 GHz (5G FR-1) band, where it can take the place of LDMOS devices. A high-power RF Gan-on-Sic high-electron-mobility transistor (HEMT) that meets the needs of multi-standard cellular power amplifier applications is the Wolfs peed GTRB266908FC.
The new HEMT (Figure 4) operates in the 2,515 to 2,675 MHz frequency band and provides 549 W of POUT and 69.2% efficiency at a 3-dB compression point (P3dB). The POUT (average) is 50.1 dBm, the PSAT is 57.8 dBm, the efficiency is 48%, the gain is 15 dB, and the IBW is higher at 194 MHz The power device has a thermally improved packaging with an earless flange and an operating voltage of 48 V. It complies with ANSI/ESDA/JEDEC JS-001, is lead-free, and Human Body Model Class 1B compatible.
Infineon Technologies AG
Infineon provides a wide range of Gan devices suitable for power-conversion applications in the voltage range up to 600 V thanks to its unique Cool Gan technology. E-mode HEMTs from the Cool Gan family can deliver the excellent efficiency and lightning-fast switching rates needed for 5G applications.
Gan HEMTs have the benefit of having relatively temperature-independent on-resistance, which produces a figure of merit that is significantly higher than that of comparable silicon-based competitors. The size and weight of the power solutions are greatly reduced by Gan characteristics, which also result in a reduction in board space and weight. In 5G applications, where there is little installation space available, this is a crucial consideration.
Gan HEMTs have a benefit over comparable silicon-based equivalents in that their on-resistance is comparatively temperature-independent, producing a figure of merit that is significantly higher. The weight and size of the power solutions are greatly reduced as a result of the major impact that GaN characteristics have on both. Because there is so little installation area available for 5G applications, this is a crucial consideration.
Microchip Technology Inc.
Recently, additional MMICs and discrete devices have been released by Microchip, expanding its RF power offering. The new devices combine high power-added efficiency (PAE) and strong linearity to cover frequencies up to 20 GHz, fulfilling the demanding needs of 5G applications. The MMICs, like other Gan RF power products from Microchip, are based on Gan-on-Sic technology, offering the best high power density and yield, high-voltage operation, and longevity. Among them are Gan MMICs with frequency ranges of 2–18 GHz, 12–20 GHz, and 12–20 GHz at P3dB.
The ICP2840 Gan MMIC power amplifier, which was recently produced by Microchip and was previously known as the GIMP 2731-10, was created to fulfill the needs of 5G networks as well as Sitcom, aerospace, and defense applications. The Gan-on-Sic-based GMC P2731-10 has a frequency range of 27.5 to 31 GHz, a bandwidth of 3.5 GHz, and an output power of up to 10-W. The chip has 15 dB of return loss and 22 dB of small-signal gain, resulting in a 20% PAE and good linearity. Blocking capacitors facilitate design integration while allowing the device to be well-matched to 50 thanks to the balanced topology.