Converting Microwave Signals to Optics-on-a-Chip Makes for Light, Cool Instruments

Credits: Eleanya Onuma

Sometimes innovators adapt proven technologies to enable new capabilities.

A new instrument concept combines existing technologies and techniques to improve the way exploration spacecraft receive and convert radio frequency signals to data by converting the radio signal to optical for processing.

Goddard Photonics Engineer Eleanya Onuma said electronic signal processing components used in communication and remote sensing applications are efficient but bulky due to their ruggedized packaging for the space environment. They also operate within a narrow bandwidth which limits science investigations. He plans to convert the long-wavelength microwave signals to more compact optical wavelengths using a miniaturized version of an electro-optic modulator.

“Electro-optic modulators have cross-cutting applications in Goddard’s instrument designs,” Onuma said. “So why don’t we take a stab at that? How can we improve this essential electrooptic component to enable instrument miniaturization without sacrificing performance?”

He plans to use microwave photonics technology to design an ultra-wide band electro-optic modulator for Photonics Integrated Circuits (PICs). By combing the multiple operations of a microwave front end receiver into a single chip, communication and remote sensing instruments can process incoming signals across broader bandwidths while reducing the overall size of the modulator, susceptibility to noise, and transmission losses.

A modulator on a circuit board consists of a radio frequency switch, oscillator, mixer, low noise amplifier and frequency filters. Goddard Systems

Engineer Chris Green said these compact PICs will improve essential signal-processing for both communication and remote sensing applications in a single component without compromising performance.

Onuma’s project received Center Innovation Funds, or CIF, last year to design and validate the performance of a new, compact electro-optical modulator. This year, the team is working on prototyping their design.

“We are looking to broaden the frequency range of operation while being compatible with current integrated photonic platforms, which inherently allows for device miniaturization,” Onuma said. The design will eliminate the need for multiple antennas and electro-optic modulators in broadband applications.

While the technology isn’t connected to a particular mission, the design allows for flexible integration with low-power PICs, Onuma said. Developing smaller, faster, and more cost-effective technology will optimize mission costs across the board.

“Radiometers, for example, that observe the microwave range of the electromagnetic spectrum are essential for profiling atmospheric constituents of planetary bodies for molecules like water,” Onuma said.

Remote sensing engineers typically optimize their instruments’ antennas and front-end electronics circuits for the specific frequency band of scientific

interest, Onuma said. This means an instrument may need multiple electro-optic modulators and signal processors to accommodate different frequency bands. Consequently, each additional component results in an increase in heat generation, size, weight and power demands on a spacecraft. Having a single component that can receive and modulate broadband frequencies of interest enables a wider collection of scientific data.

Shrinking these critical components will allow future missions to operate at the same, if not better, capacity while meeting the size, weight and power demands of small satellite platforms, Onuma said. “Other applications include software-defined radios and broadband wireless communications for terrestrial and space applications,” he said.

CONTACT Eleanya.E.Onuma@nasa.gov or 301.286.1157