As 5G networks push into the millimeter-wave (mmWave) frequency bands, the challenge of accurately testing these systems in a laboratory environment has grown dramatically. This article examines the unique testing demands of 5G FR2 mmWave devices, why traditional coaxial test setups struggle at these frequencies, and how RF over fiber technology enables more accurate, repeatable, and scalable 5G test environments. It also outlines how RFOptic’s purpose-built RFoF solutions address the needs of 5G/6G testing engineers worldwide.

The global rollout of 5G networks represents one of the most complex RF engineering challenges in telecommunications history. For the test and measurement community, it has introduced equally demanding new requirements — particularly as deployments move into the mmWave spectrum. Engineers evaluating whether their test infrastructure is ready should start with a foundational question: can your signal transport method keep up with the frequencies you are testing? Exploring rf over fiber technology is increasingly the answer that test labs are arriving at.

Understanding 5G FR2: The mmWave Challenge

5G is defined by two frequency ranges. FR1 covers the sub-7 GHz bands familiar from 4G LTE, while FR2 — often called mmWave 5G — covers bands from approximately 24.25 GHz up to 52.6 GHz in the current 3GPP standard framework, with future extensions anticipated beyond 100 GHz for 6G precursor research. These FR2 bands offer multi-gigahertz of contiguous spectrum, enabling peak data rates measured in gigabits per second and ultra-low latency performance that FR1 alone cannot deliver.

However, mmWave signals propagate very differently from sub-6 GHz RF. They are attenuated much more rapidly in air, blocked by building materials, and absorbed by the body of a device under test. This means 5G mmWave devices almost universally rely on beamformed, phased array antenna systems — integrated directly into the device — that electronically steer a narrow beam to maintain link quality.

For test engineers, this creates a significant problem: these integrated antenna arrays cannot be physically connected to a test instrument via a coaxial cable. Testing must be done over the air (OTA) — meaning the device radiates its signal in free space, and test instruments must receive and analyze the radiated field. This in turn demands anechoic or semi-anechoic chamber environments, precise positioning, and signal transport from the antenna probe in the chamber to the instrument rack outside it.

The 3GPP’s technical specifications for 5G OTA testing are detailed in the TS 38.521 and TR 38.810 documents, which outline measurement configurations for FR2 devices. 3GPP Technical Specifications provide the industry baseline against which all 5G OTA test methodologies are validated.

Why Coaxial Cable Fails the 5G FR2 Test

At sub-6 GHz frequencies, the losses introduced by a coaxial cable between a test antenna and an instrument are manageable. At 28 GHz or 39 GHz, they are not. Signal attenuation in standard coaxial cables at mmWave frequencies is dramatically higher — often 2 to 4 dB per meter or more at Ka-band frequencies, depending on cable diameter. For a test setup with antenna probes positioned several meters from the instrument, this means severe signal degradation.

The consequences are measurable and serious:

• Higher noise floor in the measurement system, reducing sensitivity and making it harder to detect weak signals from the device under test.
• Reduced dynamic range, preventing the system from characterizing both strong and weak signals in the same measurement sweep.
• Phase instability due to coax mechanical sensitivity — even bending a cable can shift its phase response, introducing errors in phase-sensitive measurements like EVM (Error Vector Magnitude).
• Impractical cable management: at mmWave frequencies, even small connectors introduce insertion losses and mechanical fragility becomes a reliability concern in frequently reconfigured test environments.
• Fundamental frequency limits of most coaxial assemblies make coverage above 40 GHz an engineering challenge requiring specialized and expensive waveguide solutions.

RF over Fiber as the 5G Test Infrastructure Standard

RF over fiber addresses the signal transport problem in 5G FR2 test environments at the fundamental level. Instead of routing the mmWave signal through coaxial cable, RFoF converts it to an optical signal immediately at the antenna probe and transports it over optical fiber to the instrument. Optical fiber has negligible attenuation in the relevant transmission windows (on the order of 0.3 dB/km), is completely immune to electromagnetic interference, and does not introduce phase errors due to bending or temperature changes.

For 5G test labs, this translates to practical advantages:

• Probe-to-instrument distances of tens of meters or more with minimal signal degradation — enabling large anechoic chambers and flexible test geometries.
• Consistent signal integrity that enables accurate, repeatable measurements across multiple test runs and different environmental conditions.
• Freedom from EMI: test chambers often house high-power amplifiers, switching equipment, and other RF sources. Fiber is immune to all of this.
• Simplified test cell design: replacing bundles of mmWave coaxial assemblies with a single fiber link dramatically reduces installation complexity.

RFOptic’s Role in 5G/6G Testing

RFOptic’s stated mission is to provide state-of-the-art RF-optical solutions with superior performance to the 5G/6G testing emerging markets. The company describes itself as a solutions provider and R&D-driven innovative manufacturing company with global coverage and extensive experience with customized solutions for the 5G testing markets.

RFOptic offers what it describes as top-notch RF-over-glass commercial off-the-shelf products for civil 5G and defense applications. Key elements of their 5G testing product line include:

• Off-the-shelf RF over fiber links covering from DC to 67 GHz in three family groups, providing frequency coverage from well below FR1 through the complete FR2 band and into mmWave territory relevant for 6G research.
• HSFDR (High SFDR) links optimized for applications where spurious-free dynamic range and signal stability are paramount — exactly the conditions required for accurate 5G OTA measurements.
• Subsystems and end-to-end solutions per customer requirements, recognizing that 5G test labs often have specific chamber dimensions, device categories, and measurement configurations that require tailored signal transport architectures.
• Remote management: all links and subsystems are managed by local or remote management interface, supporting the integration of RFoF links into automated test system software environments.

RFOptic also provides an online RFoF link calculator tool to assist test engineers in predicting link performance parameters including noise figure, gain, and dynamic range for their specific configurations — enabling accurate test system planning before hardware deployment.

Anechoic Chambers and Remote Antenna Applications

One of the most direct 5G test applications for RFoF is the anechoic chamber setup. In this configuration, the test antenna (probe) is inside the shielded chamber, while the signal generator and analyzer are in the equipment rack outside. Connecting these requires passing the mmWave signal through the chamber wall — a location where coaxial feedthroughs introduce insertion loss, potential leakage, and EMI ingress.

RFOptic offers specific solutions for anechoic chamber applications, recognizing that this is a core use case in the 5G test environment. The optical fiber feedthrough eliminates the shield integrity problem and allows the full mmWave bandwidth to be transported without the frequency-dependent losses of coaxial alternatives.

Preparing for 6G: The Frequency Frontier

While 5G mmWave deployments are still in early phases in many markets, research and pre-standardization work on 6G has already begun at frequencies above 100 GHz — the D-band (110–170 GHz) and beyond. Test infrastructure being deployed today for 5G FR2 will increasingly need to serve as the foundation for 6G research environments.

Choosing RFoF solutions with frequency coverage well beyond the immediate 5G FR2 requirement provides a degree of future-proofing for test facilities. RFOptic’s product family, which extends to 67 GHz in its standard off-the-shelf range, positions test labs to expand measurement capability as 6G frequencies become relevant for device and system characterization.

Engineers specifying rf over fiber modules for 5G test infrastructure are therefore making a technology investment with a long useful life — particularly when the solution comes from a vendor with demonstrated capability well above the minimum required frequency and with a track record of supporting customized configurations.

Conclusion

The shift to 5G FR2 mmWave testing has fundamentally changed what test and measurement infrastructure must deliver. Signal transport between antennas and instruments across the 24–40 GHz range demands low loss, phase stability, EMI immunity, and scalability that coaxial cable cannot reliably provide. RF over fiber has become the standard solution for forward-thinking 5G test labs, and its role will only grow as the industry progresses toward 6G research frequencies.

For test engineers and lab managers evaluating their signal transport architecture, the key criteria are frequency coverage, dynamic range, phase consistency, and the availability of system-level support. Purpose-built RFoF solutions from experienced high-frequency vendors offer the complete package for today’s 5G test challenges and tomorrow’s 6G requirements.

As electronics continue to shrink while demands for performance grow, the industry faces a pivotal inflection point. For engineers and product teams researching IC packaging companies capable of delivering complete SiP solutions, understanding the full technology landscape has never been more important.

What Is System-in-Package and Why Does It Matter?

System-in-Package (SiP) is a technology approach that integrates multiple functional components — processors, memory, sensors, RF modules, and passive components — into a single compact package. Unlike a System-on-Chip (SoC), which integrates all functions onto a single die, SiP combines multiple dies and components, often using different process nodes, into one unified module.

This heterogeneous integration approach offers a powerful alternative to traditional multi-chip designs, addressing the core engineering tradeoffs of size, performance, power consumption, and cost. As consumer electronics, wearables, industrial IoT devices, and defense electronics demand ever-smaller form factors without sacrificing functionality, SiP has emerged as a foundational technology for the next generation of electronic systems.

Market Trends Driving SiP Adoption

The global SiP market is on a steep growth trajectory. According to industry research, the market was valued at approximately $8 billion in 2024 and is forecast to approach $17 billion by 2028, growing at a compound annual rate exceeding 15%. Several macro trends are powering this expansion:

• IoT and Wearable Devices: The explosion of connected devices demands ultra-compact, low-power modules. SiP allows designers to integrate sensing, processing, and connectivity functions into a package small enough for a smartwatch or medical implant.
• 5G and Advanced Communications: Millimeter-wave 5G systems require highly integrated RF front-end modules. SiP enables the co-packaging of RF components with antenna structures, dramatically reducing signal loss and board real estate.
• Defense and Aerospace Miniaturization: Modern defense electronics — from drone guidance systems to soldier-worn electronics — require extreme miniaturization alongside ultra-high reliability under harsh environmental conditions.
• Medical Device Innovation: Implantable devices, hearing aids, and continuous health monitors are pushing miniaturization to new extremes, where SiP technology enables life-critical functionality in sub-centimeter packages.
• Automotive Electronics: Advanced driver-assistance systems (ADAS) and autonomous vehicle platforms require high-density, thermally reliable SiP modules capable of operating across extreme temperature ranges.

The Technical Challenges of SiP Design and Manufacturing

While SiP offers compelling advantages, its design and manufacturing complexity is substantial. Engineers face a constellation of technical challenges that require deep, cross-domain expertise:

• Thermal Management: Integrating multiple high-power components into a small package concentrates heat significantly. Ensuring reliable thermal dissipation without increasing package height or weight requires sophisticated substrate engineering, embedded coin technology, and careful die placement.
• Signal Integrity and Electromagnetic Interference (EMI): Heterogeneous integration creates complex signal routing challenges. Fine-pitch interconnects between dies must maintain controlled impedance while minimizing crosstalk and EMI — particularly critical in RF and high-speed digital applications.
• CTE Mismatch: Different materials — silicon dies, organic substrates, and passive components — expand and contract at different rates under thermal cycling. Managing coefficient of thermal expansion (CTE) mismatches is essential for long-term reliability, especially in aerospace and defense applications where temperature extremes are the norm.
• Supply Chain Complexity: Traditional SiP development requires coordinating multiple specialized vendors for substrate fabrication, die sourcing, assembly, and testing. Each handoff introduces risk, delay, and potential quality variation.
• Design for Testability: Testing a fully assembled SiP module is fundamentally more difficult than testing individual components. Embedded dies and multi-layer substrates limit physical access, requiring sophisticated In-Circuit Testing (ICT) and system-level test strategies.

The Landscape of SiP Solutions Today

The market has responded to SiP complexity in several ways. Large Outsourced Semiconductor Assembly and Test (OSAT) companies offer high-volume SiP assembly, but their minimum order quantities and standardized processes are often mismatched with the prototype-to-mid-volume needs of defense, aerospace, and medical device companies. Dedicated substrate foundries provide advanced substrate technology but require separate assembly and test partners, fragmenting the supply chain.

The result is that many engineering teams face a frustrating choice: accept the limitations of standardized, high-volume OSAT services, or manage a complex multi-vendor supply chain that introduces quality risk and schedule uncertainty. A third path — working with an integrated, all-in-one solutions provider — is increasingly recognized as the most effective approach for complex, high-reliability SiP programs.

For a deeper understanding of the academic and technical foundations of SiP development, the IEEE Xplore library provides extensive peer-reviewed research on heterogeneous integration, organic substrates, and advanced packaging reliability testing.

How an All-in-One Approach Addresses SiP Complexity

PCB Technologies, with its specialized iNPACK division, has built an integrated capability that directly addresses the core challenges of SiP development. As described on their website, the company is an “All-in-One Solutions Provider of Miniaturization & Advanced IC Packaging Solutions,” operating with a single-roof approach that spans design, substrate fabrication, package assembly, and testing.

Their iNPACK division offers advanced System-in-Package solutions as multi-component, multifunction products. Key capabilities include size reduction, high thermal conductivity, ultra-thin substrates with fine lines and spacing, controlled CTE, 3D design, shielding options, sealing solutions, fine-pitch flip-chip and copper pillar technology, double-side assembly, development and production testing, and full turnkey solutions.

A core differentiator of iNPACK is its organic substrate technology, supporting 25-micron lines and 25-micron spacing — precision that enables the fine-pitch signal routing critical to advanced SiP applications. Their on-site, certified cleanroom manufacturing facility ensures that sensitive components remain free from contamination throughout the assembly process.

Critically, PCB Technologies’ approach eliminates the multi-vendor fragmentation that plagues many SiP programs. Their R&D center is located within the same complex as their manufacturing facilities, enabling seamless transitions from design iteration to prototype production without the handoff delays and communication gaps inherent in fragmented supply chains.

For engineers exploring panel level packaging as an alternative to wafer-level processes, iNPACK’s panel-level approach uses rectangular panels similar to organic substrate manufacturing — designed for efficient production, lower cost per unit, and the flexibility to incorporate Multi-Chip Module (MCM) and SiP assembly on the same production infrastructure.

SiP in Practice: Applications Across High-Demand Industries

The industries best positioned to leverage SiP technology share a common need: maximum functionality in minimum space, with uncompromising reliability. PCB Technologies serves customers across medical, defense, aerospace, communications, and semiconductor sectors — all of which are increasingly turning to SiP as a strategic platform.

• Defense Electronics: Miniaturized radar modules, electronic warfare systems, and soldier-worn communications devices require SiP solutions that maintain performance under shock, vibration, and extreme temperatures. High-reliability SiP with embedded thermal management meets these requirements.
• Medical Devices: From cochlear implants to continuous glucose monitors, medical SiP modules must combine RF, sensing, and processing in biocompatible packages that meet ISO 13485 quality standards — a certification held by PCB Technologies.
• IoT and Industrial Systems: Industrial IoT nodes that operate in harsh environments require rugged SiP modules with wide operating temperature ranges, integrated sensing, and low-power wireless connectivity.

Conclusion: SiP Is No Longer Optional — It Is a Strategic Imperative

System-in-Package technology has moved from a niche solution for space-constrained applications to a mainstream platform technology across multiple high-growth industries. For product teams facing the dual pressure of miniaturization and performance, SiP is increasingly the answer — but only when implemented with the right combination of substrate expertise, assembly precision, and integrated design-to-test capability.

The companies that will lead in the next wave of electronics miniaturization will be those that choose manufacturing partners capable of delivering SiP solutions as an end-to-end, accountable service — from substrate design through final system testing, all under one roof.

Face Lit; AI generated faces
Imagine the number of pre digital photos that have been taken since the invention of the camera. With these there are both good and bad pictures with people not smiling, frowning or just looking ugly. No matter what made that picture special, that instance in time, these disappointments let the viewer down.
Thankfully Face Lit has the answer, you now can scan in your old photos and change them with natural moods and expressions being added without needing to know anything about altering photos or a professional. This novel application works through the use of artificial intelligence that creates AI generated faces from the original target image. Through simple presets you can get each person to look how they would have in the photo unlike what you have seen in the original.
Imagine all of those family pictures now fixed and frameable that were not originally possible, keeping precious moments alive. AI generated faces additionally offer you the opportunity to also fix media pictures, educational and historical pictures and also give you a way to use them in advertising.
So how does Face Lit work? The software takes an image and uses artificial intelligence that has been trained to recognize facial features. These features need to be also identified in context of the larger image such as the turn of the head, and relies on modelling of different layers of a face. These layers have parametric variables that are then modified through relative calculation and mapping from the original image.
Artificial intelligence utilizes essentially a weighted decision-making matrix that has node points at each layer and data is passed from one side of the neural net or decision-making matrix to the other, filtering through these decision layers as it goes. Each node that represents one of many options in each layer has a weighted value to help the software guess what it needs to make a decision on. A layer is essentially a data filter, for images it could be a method used for feature recognition, applying grayscale and contrast to assess a picture’s geometry through normal distribution of hue and relative pixel locations. AI generated faces and applications such as Face Lit normally use this type of technique and others in different layers to help understand what is in the picture automatically and where these features that have been identified are in terms of pixels.
The first step of the AI decision making process is to first take images and train it iteratively through passing images en masse through the neural network. Each time it correctly or incorrectly guesses each node the weighting factor is adjusted based on its previous experience. Eventually the weighting values of each node is within an acceptable tolerance and the learning stage is complete. For neural networks with multiple layers this is called deep learning however it is more representative of an iterative optimization process. This process is normally done during the development cycle of the software allowing users just to pass in their photos later and for it to only need to run once. The initial learning process normally requires a lot of processing power to optimize the weightings quickly, however once done these values are saved and the user can run Face Lit within a fraction of a second. This application is based on AI used for real-time video sources and therefore is highly performant for working quickly on lightweight low power devices.
The Future
Soon as Face Lit becomes much more widely used there will be no more need to hide hideous pictures that capture an instance in time. You can also use these images in advertising campaigns, education and media to help get your message across.
For more information visit this website: https://www.d-id.com/