RF Over Fibre (RFoF) Real Time Applications: Part 1 – The CEMA/EMSO RFoF Vehicle Integration Kit (VIK)
Author: Andy Haslam, Director of Business Development, PPM Systems
RFoF is a highly effective, low risk method of distributing data through fibre optic cable. This approach leverages the strengths of both RF and fibre optics. You can find out more about this in my recent blogs ‘’Optimal data distribution over fibre – The Basics’ and The Role of RF over Fibre Technology in Modern Defence Applications.
The terms Cyber Electro-Magnetic Activities (CEMA) and Electro-Magnetic Spectrum Operations (EMSO) have become ‘all things to all men’ and I’m still not convinced that we have the right terminology. Depending on which part of the Defence or Governmental community you speak to you will get a different answer to what they want to achieve and how they wish to achieve it. For the purpose of this blog I shall refer to both simply as CEMA. This is a thought piece, however to demonstrate comparison between coax and RFoF, I have woven in some of the benefits of PPM Systems’ own CEMA VIK offering.
What is the current Electro-Magnetic Warfare capability?
The Electro-magnetic Spectrum (EMS) is congested and there is a plethora of resources available to both the military and government to monitor, survey and affect the EMS used by the enemy, in whatever guise they may be. However, much of this equipment is legacy, due to the fact that we have been fighting a series of insurgency campaigns for the last 30 years, and our Electro-magnetic Warfare (EW) capability has been greatly reduced both in terms of the equipment we have and the skill-sets of our operators. Undoubtedly within the Land domain there is a lot of catching up to do and Tier One nations (5EYES, NATO and others) are all conducting modernisation and transformation programmes to rapidly attain capability. This is especially pertinent as our near peers are now very successfully conducting EW operations, helping to further mature and develop their capability.
Consequently, there is a real need for allied forces to close that gap by enhancing personnel training, as well as having operationally configurable CEMA equipment (hardware and software) that is effectively integrated into land platforms. This effective integration is centred on optimising the position of the equipment on the platform (e.g., antennas vs. radios), and the configurable distribution of data / signals between the pieces of equipment – this integration solution is often referred to as a Vehicle Integration Kit (VIK).
PPM Systems’ RFoF CEMA VIK enables the effective integration of the CEMA equipment onto the platform through the use of an optical architecture that is frequency agnostic and dynamically configurable. It unlocks the true benefits of the software enabled configurability seen in typical modern CEMA equipment, which ensures that the performance of the integrated CEMA equipment matches its potential capability. Additionally, although the RFoF CEMA VIK was initially designed for Land platforms, its architecture and potential use cases are compatible with land, sea and air platforms, making it a truly pan-domain solution. This solution can readily replace and significantly improve platform mounted CEMA capabilities that are currently heavily constrained by the use of coaxial VIKs.
Coaxial Routing for CEMA capabilities
Current VIKs typically use coaxial cables (and RF splitters if required) to transport signals to and from the antennas, which introduces significant RF losses. This approach severely limits the performance of any vehicle mounted CEMA capability, with some specific examples as follows:
Reducing detection range in Electronic Surveillance (ES) applications
The RF losses through the coaxial VIK will reduce the strength of any received signal at the signal analysis equipment; if this reduction causes the signal to drop below the noise floor, then the analysis equipment cannot detect it. Furthermore, where the ES application requires a signal to be decoded (e.g., cellular signals), the analysis equipment typically requires the received signal to be above the noise floor by a predefined amount. Therefore, the losses in the coaxial VIK cabling reducing the received signal strength effectively reduces detection range.
Reducing engagement range of Offensive CEMA (OC) or Electronic Attack (EA) effect
Coaxial VIKs typically use power amplification that is co-located with, or a part of, the signal generation equipment that generates the OC or EA effect. This equipment is typically inside the vehicle, which leads to reduced RF transmit power at the antenna through the coaxial VIK cable losses, which in turn reduces the engagement range for the OC or EA effect. Note that vehicles are often space and power constrained so are frequently unable to integrate larger Power Amplifiers (PAs) to compensate for the losses.
Reduces scope of effective coverage for Force Protection ECM (FPECM) applications
Barrage type jamming can be used to inhibit low power / undetected signals, but this is power inefficient compared to responsive type (e.g., protocol based) that requires signal detection. The reduced detection range (as per point 1 above) will likely drive an FPECM system to use more barrage type techniques, which is a less efficient usage of the limited amount of power available in vehicles (due to space constraints and usage by other mission systems such as tactical communications). Consequently, this could lead to a reduction in inhibition range, or a reduction in the number of simultaneous threats that can be defeated.
Fixed point-to-point (P2P) network topologies
Antenna placement relative to the target is key in having effective coverage; for example in Tx applications it ensures that sufficient RF power can be delivered to the target device (or signal is jamming / ECM applications). In Rx applications it ensures that Signals of Interest (SoI) can be received and processed to provide useful intelligence. The extant point-to-point network topology fixes which antenna is connected to which CEMA equipment giving a fixed configuration that is not optimised to the theatre specific threats. Moving to a star or hub type network topology will enable reconfiguration to optimise coverage to theatre, or even location specific, threats. This will maximise performance for each platform’s individual constraints e.g., electrical power available and shape.
The RF losses leading to the above performance limitations are especially pertinent above about 1 GHz, above which many commercial and Defence technologies of interest such as Wi-Fi, cellular, and SatCom sit: This highlights the importance of a VIK that prevents this limitation. This ‘1 GHz upwards’ marker for significant RF losses has been demonstrated to a UK MOD customer that compared their RFoF Optical Distribution solution to a coaxial equivalent. They exhibited both shock and frustration that they have effectively been missing so many signals of interest for so long. See my previous blogs that explain why this is the case.
This results in the advanced CEMA capability being ‘hamstrung’ by its VIK; although highly capable, its performance when integrated onto a platform cannot be matched. This is pictorially illustrated below in the context of operational effectiveness, where the C= Capability of the CEMA equipment and P= Performance the CEMA equipment when integrated onto a platform.
What is an RFoF CEMA VIK?
An RFoF CEMA VIK uses the optical domain to distribute signals and data to antennas from CEMA equipment and vice versa, with PPM Systems’ RFoF CEMA VIK providing a solution that can dynamically configure the mapping of radios to antennas and distribute the signals without loss over long distances. This enables the antennas to be placed in optimised positions on the platform for maximised performance, and enables the true benefits of SDR configurability to be realised through changing the SDR to antenna mapping such that the antenna best suited to the SDRs chosen role can be selected.
When compared to a traditional coaxial VIK, the benefits of PPM Systems’ RFoF CEMA VIK manifest as a 5x increase in detection range (compared to a 10 m coaxial based antenna at 18 GHz), and a 7x increase in engagement range (compared to a 4 m coaxial based antenna at 6GHz with equivalent amplification). These benefits, as well as the previously mentioned dynamic configuration benefits are primarily driven by following two features of the VIKs:
Lossless single mode fibre optic cabling
Losing 0.02 dB over 10 m compared to a loss of 3.6 dB over 10 m for coaxial (LMR-400-DB coaxial cable at 6 GHz and fibre optic at 1550 nm) as shown below. It also supports high capacity data rates and the coexistence of both analogue RF and digital RF formats, giving future flexibility.
Optical distribution (hub / star network topology)
This enables the dynamic routing of signals in that any SDR can be mapped and routed to any antenna on the platform. This allows the platform mounted CEMA capability to be optimised to the operational threat and theatre environment almost instantly (less than a second).
PPM Systems’ RFoF CEMA VIK can be applied to a number of different CEMA applications such as Electronic Attack (EA), Electronic Surveillance (ES), or a combination of these to give an Electronic Warfare (EW) platform. To illustrate one implementation of the VIK, the below diagram shows a Counter-IED (CIED) application that could be applied to projects such as the UK’s CRENIC, or the US DoD’s JCREW; this example has been selected as it includes a significant number of antennas / Radioheads (RHDs) to illustrate potential scaling.
Both the above example implementation, and implementations for any other CEMA applications, generally consist of four main elements:
Roof Mounted RHDs
Optically enabled antennas that are typically Omni-direction for CIED jamming and ES DETECT functionality, but could also be Direction Finding (DF) antennas for ES LOCATE functionality or directional transmit (Tx) antennas for EA or OC DEFEAT functionality.
Side Mounted RHDs
A small form factor optically enabled directional antenna that can support both Tx and Rx. They are typically used in a Tx role for improving CIED performance.
Optical Distribution Chassis
This chassis fits within a typical extant platform space claim and provides dynamic routing (splitting and switching) of antennas and SDRs such that the combinations can be optimised to the changing threats in the operational environment. For example, optically combining multiple EA, OC or ECM effects to easily generate complex / hybrid signals transmitted through the optimised antenna type and location.
Main CEMA Chassis
This chassis contains the signal analysis and generation functionality delivered by equipment such as SDRs, but can also house the Electro-Optic (EO) conversion functionality required for this solution. It integrates onto an OpenVPX 3U card form factor that includes 8 RFoF channels with 4 digital C2 channels, which supports 4 transmit / receive (TRx) RHDs per 3U card.
What can an RFoF VIK solution provide?
As the Defence industry evolves, the use of an effective VIK solution to enable a mounted CEMA capability will be crucial for maintaining a tactical edge and ensuring the success of military operations in an increasingly complex and contested battlefield. The PPM Systems’ RFoF CEMA VIK solution can be summarised as providing:
Dynamic configuration
Gives optical routing functionality for dynamic configuration to optimise the CEMA application to the operational environment and the vehicle.
Step change in performance
Eliminates the performance limitations of extant coaxial VIKs to maximise the effectiveness of vehicle mounted CEMA capabilities.
Embedded future growth
Includes inherent future growth with the ability to support RFoF, RFoIP and the distribution of digital Command and Control (C2) data simultaneously if required.