Reducing phased array antenna design time by 25 percent

Introduction

RF2B is a wireless design services company offering custom antenna design and validation services across air interfaces and bands. RF2B developed a phased array antenna proof of concept design for small cell Citizens Broadband Radio Service (CBRS) base stations at 3.5GHz for its customer Menlo Micro, who develops high performance RF MEMS switch integrated circuits. Menlo Micro developed a reference design for 3.5GHz MEMS Based Differential Delay Shifter (DDS) using its RF switches that can be a great building block for electronically scanning antenna array in place of traditional phase shifters, which are band limited as well as expensive. Simcenter Feko comes with a feature called finite array analysis, plus a built-in script that synthesizes the antenna array. These features significantly sped up the high-level trade off analysis due to model building acceleration and lower memory consumption leading to much quicker simulation times, which is critical during the high-level design phase.

About the customer

RF2B is a wireless design services company offering custom antenna design and validation services across air interfaces and bands. Its mission is to significantly enhance quality and shorten time-to-market for radio frequency integrated circuits (IC) developers, manufacturers and satellite system providers. RF2B provides validation services based on disruptive system level methodology and turnkey development of application reference radio frequency integrated circuit designs. The use of fast, accurate simulation is key to its efficiency. Customer applications span mobile, medical, trackers, gateways, home automation and gaming accessories.

Comparison between Simcenter Feko simulation results and actual measured values.

Their challenge

RF2B developed a phased array antenna proof of concept design for small cell Citizens Broadband Radio Service (CBRS) base stations at 3.5GHz for its customer Menlo Micro, who develops high-performance RF MEMS switch integrated circuits. Menlo Micro developed a reference design for 3.5GHz MEMS Based Differential Delay Shifter (DDS) using its RF switches that can be a great building block for electronically scanning antenna array in place of traditional phase shifters, which are band limited as well as expensive The challenge with antenna array design for CBRS band was to achieve enough azimuth and elevation beam steering range with enough grating lobe suppression and higher efficiency. That required high level design analysis to decide number of columns and rows, element type, element spacing angular step size and amplitude tapering for the antenna array.

Another challenge was the overall complexity of the design, requiring a time efficient antenna array simulation and design methodology that included the feed network as well. In addition, antenna array also needed to be optimized in its mechanical environment, including the enclosure and radome.

Array 3D gain pattern, azimuth at boresight and elevation +6.5°.

Our solution

Simcenter™ Feko™ software, which is part of the Siemens Xcelerator business platform of software, hardware and services, comes with a feature called finite array analysis, plus a built-in script that synthesizes the antenna array. These features significantly sped up the high-level trade-off analysis due to model building acceleration and lower memory consumption leading to much quicker simulation times, which is critical during the high-level design phase.

CBRS antenna measured radiation patterns.

Results

At earlier stages, the various blocks were modeled with multiport S-parameters that integrated well with the Simcenter Feko non radiating network schematic function. It was possible to optimize the antenna array design by conducting a careful trade-off analysis of materials and separating from the antenna array when adding the antenna enclosure and especially the radome that Simcenter Feko was used to analyze. The entire design was simulated on an off-the-shelf desktop computer while still accomplishing simulation run times that met the end customer’s deadline.

The antenna array was fabricated as simulated and designed and was validated in an anechoic chamber with test results for the gain, steering range of the beam and antenna array efficiency. Excellent agreement with Simcenter Feko simulations was observed as shown in the picture of the antennae. Disagreement in the sidelobes and back lobes is an artifact of source cables, etc. CBRS Antenna Measured Patterns compared with Simcenter Feko Simulations at 3.62GHz. Dotted lines were measured patterns of two antennas fabricated and solid line were Simcenter Feko simulations.

“The unique features of Simcenter Feko such as finite array analysis and synthesis combined with lower memory requirements were key to faster and more accurate simulations and helped us complete our design in time to deliver a fully validated phased array antenna product to our customer,” says Mats Lindstrom, president and chief executive officer (CEO), RF2B.