The QPM1000 is a high performance, 2 to 20 GHz multichip module (MCM) that combines a limiter and low noise amplifier (LNA) within a small surface-mount package. It addresses traditional and emerging military system requirements for the receive arm in a variety of transmit/receive (T/R) architectures. Not only does the QPM1000 pull from Qorvo’s portfolio of performance-leading MMICs, a mainstay of the defense and aerospace markets, it leverages Qorvo’s high volume and low-cost packaging technology, used in traditional consumer and commercial markets. The result is a compelling and affordable surface-mount limiter/LNA that optimizes performance and footprint.
MILITARY MARKET NEEDS
Without sacrificing performance, defense and aerospace systems continue to choose commercial products to drive down nonrecurring and unit costs, as well as development schedules. While the use of commercial off-the-shelf (COTS) products has become the norm over the past several years, applying commercial packaging technologies to integrated RF front-end assemblies has lagged. Using commercial packaging technology is an opportunity to further shrink footprint, reduce cost and maintain the highest level of performance in military architectures.
Figure 1 shows the block diagram of a conventional T/R module, with the functionality of the QPM1000 indicated. Although a highly integrated, single chip solution offers the smallest size, it comes with high development cost and compromised performance. Alternatively, MCMs enable choosing the “right junction for the function,” resulting in the highest level of performance available using existing MMICs and a much shorter development cycle time, with only a modest penalty in size. The surface-mount QPM1000 and related MCMs are compatible with low-cost assembly to a second-level PCB using standard solder reflow processes. In comparison, a T/R module using single-function packaged components yields a footprint that is typically 10x larger—even greater—than an MCM solution.
HIGH VOLUME, LOW-COST HERITAGE
Qorvo is a world leading supplier of MCMs for handsets, shipping hundreds of millions of units each year. Although the mobile device market is quite different from defense and aerospace, commercial capabilities can be leveraged in a crossover play: global sourcing, design rules, materials, assembly processes and production test. Qorvo has invested substantially in laminate technology (i.e., a highly engineered soft board) and a robust manufacturing and supply chain. Design rules established over the years in concert with fab processes minimize trace width and gap geometries while maintaining high assembly yield. These laminate materials form the base for mixed technology assemblies that include die attach, wire bond and surface-mount component attach processes. Importantly, Qorvo routinely spins custom laminate designs quickly and at low-cost. These commercial capabilities have been tapped to establish a military-focused development engine that brings high performance MMICs together to create MCM solutions.
DESIGN AND PERFORMANCE
The QPM1000 combines two separate MMICs into a multichip module (see Figure 2). The limiter is a broadband, high-power limiter chip based on Qorvo’s GaAs VPIN technology. This MMIC operates through 20 GHz and has 10 W peak power handling. The LNA MMIC, fabricated using Qorvo’s 3MI
0.15 µm power PHEMT process, has 2.5 dB typical noise figure at 10 GHz and flat gain past 20 GHz.
The module design features a customized laminate base, which optimizes the RF performance by minimizing die-to-die spacing and the associated bond wire interconnects. The RF transitions were designed and verified for operation through 40 GHz, and the air cavity package design provides high performance through 20 GHz, the operating frequency range. The layout yields an overall 6 mm × 5 mm land grid array footprint. The QPM1000, both lead-free and RoHS compliant, can be surface-mounted to a second-level PCB using standard solder reflow assembly processes. It is assembled and tested in the U.S.
The QPM1000 delivers 17 dB small-signal gain, with gain control, and greater than 18 dBm output power at 1 dB compression. The noise figure ranges from 1.5 to 4 dB across frequency (see Figure 3). The integrated limiter handles up to 4 W of incident power without performance degradation. IM3 measures less than 20 dBc at 25°C, with 0 dBm input power per tone. The typical bias conditions are 5 VD, 100 mA IDQ and 1.3 VG2.
Qorvo’s QPM1000 is an integrated limiter/LNA providing robust performance over the 2 to 20 GHz frequency range. It combines high performance MMIC die into a low-cost, laminate-based MCM assembly to optimize performance in a small surface-mount package.
Higher levels of integration in the future will increase functionality and enable proportional shrinks in MCM footprint. As the performance of single-function MMICs improve, MCM T/R architectures will benefit accordingly. The same packaging technology used with the QPM1000 has been extended to GaN MMICs, enabling MMIC combinations that leverage the optimum device technology for each RF component. To reduce unit cost and improve environmental robustness, overmold packaging can be used in place of air cavity, when warranted to meet the requirements of next-generation military systems.