Article By Microchip Product Manager Baljit Chandhoke
RF systems need power amplifiers (PAs) to deliver linear efficient high output power. As systems move to higher-order modulation schemes such as 64/128/256 Quadrature Amplitude Modulation (QAM), they also must deliver high linearity and efficiency in denser environments with stringent peak-to-average power ratio (PAPR). This performance is critical in Aerospace & Defense (A&D), Satellite Communications (Satcom) and 5G Communications. A new generation of Gallium Nitride (GaN) on Silicon Carbide (SiC) Monolithic Microwave Integrated Circuits (MMIC) PAs offers a solution to these challenges with the highest power density to generate high linear output power with high efficiency.
RF Power Amplifier Opportunities and Challenges
The biggest growth opportunities and challenges for the RF power amplifiers are in satellite communications (Satcom), as well as emerging 5G communications solutions. NASA has enabled private-sector companies to launch thousands of low-Earth-orbit (LEO) satellites that are now circling the earth and delivering broadband Internet access, navigation, maritime surveillance, remote sensing and other services. These RF applications consistently seek SWaP-C or Size, Weight, Power, and Cost benefits. Large dish antennas are being replaced with phased array antennas for satellite communication that require smaller size components for integration, as well as lower weight components. High RF power, which is linear with high P1dB and IP3, to reduce distortion and is efficient with high PAE to minimize power consumption, is essential for these RF applications.
Millimeter-wave 5G Communications
New generations of millimeter-wave 5G communication solutions, by virtue of their speed, ultra-wide bandwidth, and low latency for broadband communication, is substantially increasing how much information can be shared in support of real-time decision-making and other military applications. 5G systems operating in lower frequency bands (sub 6 GHz) have been vulnerable to high-power jamming signals, but 5G millimeter-wave (24 GHz and above) systems are bringing 5G networking to both on-battlefield and off-battlefield applications with the millimeter wave band that is not as vulnerable to high-power jamming signals. Examples include battlefield sensor networks for command-and-control data gathering, and augmented reality displays that enhance situational awareness for pilots and infantry soldiers. 5G will also enable virtual reality solutions for remote vehicle operation in air, land, and sea missions. Off the battlefield, 5G will enable a variety of smart-warehouse, telemedicine, and troop-transportation applications.
Radar Communication Application
Radar systems operate in the 1 Gigahertz (GHz) to 2 GHz L band for applications including “identify friend or foe,” distance-measuring equipment, and tracking and surveillance. S band (2 GHz to 4 GHz) is used for selective response Mode S applications and for weather radar systems. X Band (8 GHz to 12 GHz) is used for weather and aircraft radar, while C Band (4 GHz to 8 GHz) is used for 5G and other sub- 7 GHz communications applications. 5G mmWave provides the highest bandwidths and data rates, operating in 24 GHz and higher frequency bands. Satellite communications for LEO and geosynchronous communication operate in the K band, which spans from 12 GHz to 40 GHz.
RF Signal Chain
The figure shows the RF Signal chain block diagram. At the receiver, the RF signal comes in through the Antenna, goes through a limiter diode, followed by a switch and the desired RF frequency is selected through the saw filters. The desired signal is then amplified through the low noise amplifier with extremely low noise figure to minimize degradation in signal to noise ratio of the received signal. Then, it is down converted using a mixer. The local oscillator (LO) signal is generated using discrete PLL components comprising of phase frequency detector, pre-scaler to provide the LO frequency to the Mixer to down convert the signal to Intermediate Frequency (IF), followed by conversion from IF to base-band for signal processing.
At the transmitter, the base-band signal is upconverted to IF and then to the desired RF frequency. The RF signal is amplified using a Power Amplifier to transmit the signal.
RF Figure of Merit
The table demonstrates the RF Figure of Merit and the benefits for components used in the RF Block diagram.
| Product Type | Key Parameter | Key Benefit |
|---|---|---|
|
LNA |
Noise Figure (dB) |
Improved Range/Signal Sensitivity |
|
PA |
OIP3 (dBm) & P1dB (dBm) |
Linear Power — Low Distortion |
|
Prescalers |
Phase Noise (dBc) @ kHz offset |
Low Nose Floor — More Range |
|
Switches |
Low Loss (dB) / High Isolation |
Low Harmonics in System |
Power Amplifiers (PA) Requirements
Power Amplifiers (PAs) play a key role at the transmitter in RF applications. One of the biggest PA requirements is that it can operate in its linear region to minimize RF distortion. Satellite communications systems that use higher-order modulation schemes such as 64/128/256 Quadrature Amplitude Modulation (QAM) are extremely sensitive to non-linear behavior. Another challenge is achieving satisfactory peak-to-average power ratio (PAPR)—that is, the ratio of the highest power the PA will produce to its average power. PAPR determines how much data can be sent and is proportional to the average power. At the same time, the size of the PA needed for a given format depends on the peak power. These and other conflicting challenges can only be met with GaN on SiC power amplifiers for satellite communication, 5G, and aerospace and defense applications.
Gallium Nitride (GaN) on Silicon Carbide (SiC) Power Amplifiers
GaN on SiC has the highest power density to generate high linear output power with high efficiency. GaN on SiC power amplifiers can operate at high frequencies in the Ka, Ku band from 12 GHz to 40 GHz for satellite communication, 5G and have broad bandwidths, high gain with better thermal properties meeting the requirements of RF applications. Microchip provides RF solutions using GaN on SiC technology meeting the SWaP-C requirement for components. ICP2840 is a flagship device which operates in 27.5–31 GHz providing continuous wave (CW) output power of 9 watts and pulsed output power of 10 watts with a gain of 22 dB and power added efficiency of 22%.
An overview of key Microchip K-band Power Amplifier offerings targeted for Aerospace & Defense, Satcom, and 5G Communications by Supplier Business Manager Steven Darrow.
K Band Power Amplifiers
ICP2840 generates 9W continuous wave output power in the Ka band from 27.5–31 GHz for uplink frequency for satellite communication as well as 28 GHz 5G frequency band.
ICP2637 has a wide bandwidth from 23–30 GHz and generates 5 watts CW output power and is offered in a QFN package as well as in die form.
ICP1445 generates 35 watts pulsed output power in the 13–15.5 GHz frequency Band.
ICP1543 operates in the Ku band 12 to 18 GHz generating 20 watts CW output power.
These PAs have high gain and power added efficiency using GaN on SiC technology and meet the requirements at Ku/Ka band for 5G, Satellite Communication, and Aerospace & Defense applications. GaN on SiC with its highest power density provides the optimal power amplifier solutions for these applications.
Microchip RF Signal Chain Solution
Microchip product categories shown in the figure provide a complete RF Signal Chain solution meeting the requirements for RF applications.
About Baljit Chandhoke
Baljit Chandhoke is the Product Manager for Microchip’s industry-leading portfolio of RF products. He has more than 15 years of product line management experience in customer facing roles–leading teams in defining new products, competitive positioning, driving design wins, revenue, and go-to-market strategies across wireless infrastructure, mobility (5G), aerospace, and defense market segments.
About Steven Darrow
As a Supplier Business Manager at RFMW, Steven Darrow specializes in diode solutions, RF switching applications, and MEMS-based technologies. He first gained an interest and understanding of the RF industry as a Communications Officer and qualified Nuclear Engineering Officer and earned his BS degree from the United States Naval Academy. Steven feels privileged to work with the best and brightest engineers in the industry who are working on the most cutting edge technology in RF/Wireless communication.
