Photonic Integrated Circuit for Dual Polarization RF Antenna Feed

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Solution Overview

Problem

Phased RF arrays face challenges due to the large volume and weight of RF-electronic beamforming networks, which can be overcome by using an optical feed network to directly transfer phase and amplitude modulation from optical signals to microwave signals.

Innovation Solution

A monolithically fabricated photonic integrated circuit (PIC) with an optical feed network modulates phase and amplitude components of optical signals, which are then converted to RF electrical feed signals using photo-detectors to drive dual polarization RF antennas, enabling a steerable RF beam with a variable polarization state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If RF-electronic beamforming networks are used to generate RF feed signals, then the system can achieve beam steering and polarization control, but the volume and weight of the system increase significantly

Engineering Contradiction:

Improvebeam steering capabilityVSAvoidbeamforming network weight

Core Design Contradiction:

Ease of operationVSWeight of stationary object

Solution Approach 1:

The patent replaces the traditional RF-electronic beamforming network with an optical feed network. Optical components such as optical waveguides, optical modulators, and photodetectors are used to generate and control RF feed signals, substituting heavy RF electronics with lighter optical systems. This substitution maintains beam steering and polarization control capabilities while significantly reducing system weight and volume.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If traditional RF components are used for phase and amplitude modulation, then the system can control polarization state, but the number of components and device complexity increase

Engineering Contradiction:

Improvepolarization state controlVSAvoidnumber of RF components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The optical feed network uses universal optical components that can perform multiple functions. Optical modulators can simultaneously control both phase and amplitude of RF signals, and the same optical network can generate feed signals for different polarization states by changing optical modulation parameters. This multi-functionality reduces the number of separate RF components needed while maintaining full polarization control capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If RF-electronic beamforming networks are used, then beam steering can be achieved, but the system occupies large space

Engineering Contradiction:

Improveelectronic beam steeringVSAvoidbeamforming network area

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The patent substitutes RF-electronic beamforming components with optical components. Optical waveguides and integrated photonic circuits occupy significantly less space than their RF-electronic counterparts. The optical feed network can be implemented on compact integrated photonic chips, dramatically reducing the physical area required for beam steering functionality while maintaining electronic beam steering capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The optical feed network reduces the number of components and size, achieving a more compact and efficient RF antenna feed module that can generate RF beams with variable polarization states, improving the SWaP (Size, Weight, and Power) efficiency and enabling electronic beam steering.

Implementation Method 1

The principle of operation uses a coherent detection scheme to directly transfer the phase and amplitude of an optical signal to a microwave signal by mixing this signal with an optical local oscillator (LO) signal

Methodology Applied

Scientific EffectCoherent detection:

Implementation Method 2

The two inputs are fed to a 2×16 power splitting network, the outputs of which are stored in pairs. Each pair is connected to a phase and amplitude modulation section, after which the two signals are fed to a 3-dB coupler. The RF-signals are obtained by coupling the signals coming out of the sixteen 3-dB couplers to a series of 16 discrete optical detectors off-chip

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11183770B2Dual polarization RF antenna feed module and photonic integrated circuit (PIC)

Publication Date: 2021.11.23 RAYTHEON CO

AI summary

An RF antenna feed module uses an optical feed network and photo-detectors to generate RF feed signals to drive a dual polarization RF antenna to produce an RF beam with a variable polarization state. The optical feed network and suitably the photo-detectors are monolithically fabricated PIC. Multiple modules may be configured to drive a dual polarization RF phased array. A single feed module can produce RF feed signals over a frequency range of at least 300 GHz.