Alciom

ALCIOM Cuts Design Time in Half for Complex Wideband RF Downconverter Subsystem

Company Profile

ALCIOM (www.alciom.com) is a consulting and design company specializing in innovative mixed-signal projects, from RF and microwave to high-speed electronics, signal processing, sensors, optoelectronics, and ultra low-power devices. Based in Chaville, France, ALCIOM was founded in 2003 and has more than 100 customers ranging from startups to worldwide telecom companies and research organizations.

The Design Challenge

ALCIOM was challenged to develop a wideband RF downconverter subsystem for a custom measurement instrument with strict instrumentation-grade specifications. In particular, the downconverter was required to cover a wide bandwidth from 700MHz up to 6GHz, with stringent phase and amplitude stability constraints.

Due to these constraints, the design required a custom assembly of several frequency translations, filtering, and amplifying stages (with no less than three intermediate frequencies). The design team kicked off the project by defining the overall system architecture, followed by modeling the system performances, focusing in particular on spurious rejection and frequency-response flatness. The team finished with circuit-level design and simulation of the custom microstrip filters and couplers used within the downconverter subsystem.

The AWR Solution

AWR’s Visual System Simulator™ (VSS) was the backbone design tool for this project. As a first step, VSS was used to create the high-level system diagram with close-to-ideal mixers, filters, and amplifiers. This then enabled the team to validate the selection of the intermediate frequencies and overall gain and noise figure budgets allocated to each stage, and finish with a specification for each of the subsystems.

In the second step, actual components were selected utilizing VSS, which enabled the team to refine each subsystem using real models (either behavioral models or S2P data files from component manufacturers) for each component. The custom microstrip filters and couplers in the downconverter subsystem were designed and simulated at the circuit level using AWR’s Microwave Office®. Because VSS and Microwave Office are seamlessly coupled within the AWR Design Environment™, it was very easy to design the components at the circuit level and immediately integrate these designs into the system-level simulations of the complete downconverter subsystem.
The third step of the design project involved simulating and optimizing each subsystem using VSS until they were close to the specifications. Figure 1 shows the VSS system diagram of a subpart of the first LO subsystem (8 to 13GHz).

Finally, after all the subsystems where modeled, VSS was used to connect them together and validate that the overall system performance was in line with the strict specifications.

Why Did You Choose AWR?

This particular project was one of the most complex custom microwave downconverter systems ALCIOM has ever designed. The ALCIOM design team chose AWR’s design tools because they met the criteria required for this demanding project, included the following:

• Intuitive and easy to use
• Capability to co-simulate at both the system and circuit level
• Easy import of third party component models

The ALCIOM design team found that VSS and Microwave Office more than fulfilled all of their requirements. VSS enabled designers to check many different possible system architectures in a matter of days and then validate in a top-down approach that system performances were still in line with the specifications of the actual components selected, as well as with the circuit-level microstrip filters and couplers designed and optimized using Microwave Office.