What is a CRPA, and how do I test it?

The acronym stands for Controlled Reception Pattern Antenna. CRPAs are designed to reduce the effects of RF interference or establish signals’ angle of arrival. Using multiple antenna elements, they minimize jamming signals, using null generation or null steering or maximize “truth” signals using beam forming or beam steering.

CRPAs are a very useful antenna system for platforms that need to operate in environments where jamming and interference are commonly present. For this reason, CRPAs are becoming increasingly common, particularly in the Defense sector. They are an extremely effective anti-jam/spoof solution, because they adapt dynamically in response to jamming or spoofing signals. 

What Comprises a CRPA?

It starts with some sort of multi-element antenna, but the real magic happens within the antenna electronics, where the RF then proceeds downstream to the GPS receiver. These items can be connected to each other in-line or in a single enclosure. Single-enclosure antennas are sometimes called “integrated CRPAs”. Fundamentally, they work the same way.

Testing a CRPA

Testing a CRPA prior to fielding is critical − especially in applications like defense, where the stakes are high. There are several test methods for testing CRPA antennas. You should evaluate these methods, their costs and suitability for the use case to ensure that your needs are fully met.

1. Record Replay – Realistic because it is actual recorded data – not simulated or generated. But once you have that recording, you are unable to make changes, so you are stuck with that test case. Finding a suitable environment in which to record can be especially difficult. For example, if you want to record threats, you need to go where threats are.

2. GNSS Simulator – This method is the lowest cost option due to advances in technology. Previously, it required very expensive and complex phase matrix equipment. If you ever considered a wavefront simulator in the past but found it to be too costly or too complicated, it is worth taking another look, because innovation now allows us to do some cool things. Simulation also provides the flexibility to cover multiple test cases quickly, conducive to fast iteration speeds.

3. Anechoic Chamber – This entails having a complete anechoic chamber system, which includes the simulation equipment and an actual physical chamber. It is very expensive and high in effort. You must consider all the variables, such as physical limitations and building standards for where you want to put the chamber. There are also several potential unknowns that you may run into during installation, which can mean more effort and cost.

4. Field Testing – This is where you bring your device out in the field and attempt to replicate real-world scenarios by staging an environment and generating a threat. This method is often preferred because it facilitates tangible conditions, but costs can add up here as well. The event must be staffed, and licenses for each threat must be obtained per local regulations. As an attendee, you have no control over what or how threats are being generated. With limited access to the threats, you will not be able to cover all the possible test cases.

Jamming Spoofing White Paper

White Paper

An Engineer's Guide to CRPA Testing

This guide discusses the applications and use cases for CRPAs, how they work and the methods for testing them. It also explores the various types of testing solutions available in the marketplace today, and helps you choose the right solution for your specific application.

Ultimately, it is probably best to test by combining some of these methods. For complete system testing, you can start with GNSS simulators for fast iterations, then rent space in a chamber or attend a field test event.

Anechoic vs. Wavefront

The anechoic, also known as “radiated” method, is the only way to test an entire system as-is, because it allows testing of both the antenna and the antenna electronics integrated in a single package without modification. Still, it requires that the chamber be an optimal size to accommodate the device or system under test. Additionally, you could be limited by the antenna setup in the chamber. 

Orolia has a special tool that auto-calibrates the system, maps the antennas, and is designed to streamline chamber setup and reduce the multiplication of hardware systems. Interference can be integrated with Skydel software or an external generator.

For the wavefront, also known as “conducted” method, all signals for each antenna element are brought to the antenna electronics via cables. This way, you are prioritizing the ability to have dynamic trajectories for the receiver and for the interference transmitter. That lets you do a great deal of testing - you can essentially model any scenario with an unlimited number of interferences. Unlike anechoic, a wavefront system is packaged lab-ready; no complex installation involved. Although you are not testing the antenna, the important part to test is the antenna electronics, so it is still a very good solution for testing CRPAs.

A wavefront simulation system is the lowest-cost option when you consider all the variables. Before committing to a purchase, you want to be aware of any limitations in the system such as signals, jammers and spoofers, and scalability for future needs. The Orolia wavefront system is scalable from two to 16 elements, is phase coherent, performs real-time automated phase synchronization, and has built-in jamming and spoofing.

Orolia’s Skydel Technology: Software-Defined

What does it mean to have a software-defined architecture? Orolia’s Skydel is a real-time simulation software that runs on Linux or Windows. To generate GNSS signals, it uses a GPU as a co-processor and a software defined radio to convert IQ data into RF. Orolia selects high-end COTS (Commercial-Off-The-Shelf) hardware to create turnkey systems, but it is possible to run Skydel on your own hardware. Because it is not as dependent on the hardware, the architecture allows you to scale down to meet simple requirements or scale up to test more complex applications like CRPA.

Today, you really can say goodbye to expensive, rigid, limited solutions. Orolia’s CRPA testing systems are more capable than ever, easy to use, and enable repeatable tests. You do not have to be an expert to use them and they can simulate threats that are difficult to reproduce, even in field testing.

If you are curious about investing in a CRPA testing system, Orolia will help you make the right move. For more information, contact sales@orolia.com. If you need GPS encrypted signals, contact sales@oroliads.com.

About Rachael Smith

Rachael Smith is the lead Marketing Coordinator at Orolia Defense & Security. She previously worked at Talen-X since 2017 and joined Orolia in 2019 after being acquired. She develops and implements marketing strategy, content, design, and branding through all channels, on corporate and product levels, concentrating on Test & Simulation and defense markets within the US. Rachael holds a Bachelor’s degree in Marketing and Management Information Systems (MIS) from Ohio University.

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