MMIC Power Amplifier


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MMIC Power Amplifier


Contents



Introduction

Abstract :
The design of an MMIC Power Amplifier needs to consider the effects of inductor electromagnetic coupling on chip and the MMIC packaging off chip. RFPro makes it easy to perform EM-circuit co-simulation of the MMIC by automatically launching and combining the EM and circuit simulation  results to reveal the frequency shifts, gain and match degradation caused by EM couplings and MMIC packaging.


As the RF industry trend continues towards higher integration densities and frequencies in 5G, defense-aerospace and IoT applications, the need for highly integrated multi-technology RF modules grows. However, designing an RF module is challenging because the parasitic effects of physical interconnects tend to cause frequency shifts which must be accounted for by using a combination of electromagnetic and circuit simulations

This two-stage LTE MMIC Power Amplifier is designed using a Keysight III-V GaAs internal demo kit. Once an initial schematic robust design topology is established, a physical layout of the design is created. The challenge is to fit all components and matching networks in the smallest possible area in order to produce a small die with the lowest fabrication cost. This leads to another challenge; the design components and the matching networks then tend to couple to each other, especially when they are densely placed and of proximity to each other. Therefore, a 2.5 D planar Momentum EM simulation is required to insure the design meets its specifications prior to fabrication.

Once the die is assembled in a package and bond wired, a 3D FEM simulation is used to account for the parasitic effects of the package and bond wires and help the designer to final adjust the design parameters to meet the overall specification.

Design Challenges

Traditionally, EM set up and EM simulation has been identified as an arduous task for engineers and has been known to require expert knowledge on EM. For over a decade, RF circuit designers have difficulties in setting up and combining the results of EM simulation with circuit analysis. That’s because they must first manually strip off the active components from their design, re-define EM ports and materials, and setup EM analysis correctly to produce a multi-port S-parameter file representing the passive interconnect structure without the active components.

Secondly, they must then manually reconnect this S-parameter file with all previously stripped off circuit components correctly to analyze the composite EM-circuit response. This process is error prone and time consuming and inhibits interactive tuning and optimization that are so crucial in the design process.

With the newly created RFPro EM environment fully integrated in Advanced Design System (ADS), this design challenge is now been eliminated. RFPro in ADS enables any designer to automatically create EM setup and analysis on their designs with automated setups and configuration and without any hurdle. RFPro utilizes both planar EM and 3D FEM simulation engines.

When full 3D EM simulation is required to characterizing RF modules with IC chips and packages, the traditional design approach, which is used by some engineers, requires exporting the module layout from the circuit design environment to a separate 3D EM environment, run EM simulations, then export the results back to the circuit design environment. This approach can be time consuming and highly error prone. With RFPro fully integrated in ADS, 3D FEM simulation can be easily accessed and automatically run on the design in the same environment with easy automated setup and analysis.

In this example, full 3D EM simulations of an RF module layout are simulated directly in the ADS circuit design environment, so no data import/export is required.

Results


Figure 1: MMIC LTE PA imported from the ADS Layout page into the fully integrated RFPro page for Momentum Planar EM simulation and analysis.


 
Figure 2: 
MMIC LTE PA circuit simulation results and RFPro EM results overlaid. The frequency shift shown is mainly a result of coupling of adjacent spiral inductors at the Input matching network.



Figure 3: 
MMIC LTE PA inserted onto a QFN package and with bond wires, imported from the ADS Layout page into the fully integrated RFPro page for FEM simulation and analysis.



Figure 4. MMIC simulation versus FEM results of the MMIC inserted onto a QFN package and with bond wires. Results show that parasitic effects from the package and the bond wires reduced the gain and the output power and also shifted the frequency lower due to the inductance of the bond wires.

Conclusion

  • Designing a MMIC in a package with bond wires is challenging because the parasitic effects of physical interconnects tend to cause frequency shifts which must be accounted for by using a combination of electromagnetic and circuit simulations.
  • RFPro provides a consistent automated interface to access multiple EM solver technologies such as Momentum and FEM in the ADS or Virtuoso environment for instant error-free EM-circuit co-simulation with significant cost savings and risk reduction.
  • RFPro provides effortless EM-Circuit co-simulation with correct automated analysis setup ensures RF circuit designers can now focus on their MMIC design to account for EM effects that was so time consuming and error prone before with a separate EM tool.

Related Information

More Information

Meta Description

DocID:
DocOwner:Jack Sifri, How-Siang Yap
DocCustViewable:Yes
Keywords:EM, MMIC
DocVersion:RFPro2019
DocPlatform:RFPro

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