Test instrumentation evolution for aerospace & defence gathers pace

03 January 2020

Test instrumentation evolution for aerospace & defence gathers pace_fighter jet
Test instrumentation evolution for aerospace & defence gathers pace_fighter jet

With order numbers continuing to increase for both commercial & military aircraft, Sam Darwish, UK & MEA Sales Director at T&M equipment rental & leasing specialist, Microlease tells us there is added pressure on the test & measurement (T&M) sector to meet the critical requirements of aerospace & defence (A&D) companies.

This article was originally featured in the January 2020 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.

A&D test engineering departments need access to reliable equipment that can deliver with integrity on a repeatable basis. There is therefore a clear need for suppliers to demonstrate a thorough understanding of the A&D sector and its specific challenges. Suppliers must be able to help manufacturers meet tight project lead times and stay within budget, offering support and flexibility in the procurement phase.

While T&M equipment is evolving fast, the A&D industry is also advancing. To remain at the forefront of technology, the sector is adopting solutions developed for other applications, such as optical interconnectivity. This cross-transfer of technologies is a challenge for A&D manufacturers, as their knowledge of such technologies can be lacking.

Take cyber/network security as an example. Here, end-to-end testing solutions are already used across numerous industries, chiefly because of the increasing need to provide high performance levels with deterministic results. More and more service providers, network equipment manufacturers (NEMs) and enterprises see the value in undertaking more network testing, measurement and validation, which will likely spread to other industries, including A&D.

With regard to network infrastructure, A&D firms are also migrating towards cloud and virtual environments, supported through web applications. Subsequently, there is also growing demand for the validation and optimisation of networks under realistic conditions.

RF in A&D

In electronic warfare, RF and microwave technologies are playing an increasingly critical role. Among emerging demands in this area is the requirement to move collected or stored RF signal data from one test instrument or sub-element to another, at rates of 10 GB/s (equivalent to 2 GHz RF bandwidth). Several data transfer technologies can be used to achieve this, including 10 Gb LAN; PCIe (PXI) Gen 3 with multiple lanes; optical (a good choice for integrated boxes); or a dedicated peer-to-peer (P2P) local bus or backplane (AXIe).

Thanks to its many advantages, the use of active electronically scanned array (AESA) antennas has become almost omnipresent in radar and electronic warfare systems. AESA antennas use phased arrays, permitting systems to operate in multiple modes, engaging multiple threats or targets, by taking advantage of powerful signal processing capabilities.

For satellite applications, it is well documented that phased array antennas deliver specific benefits in comparison with reflector antennas and can therefore be considered a good option for GEO spacecraft. Here, a single antenna communicates with multiple spatially distributed ground stations by repositioning (hopping) the antenna beam between users.

There are, however, growing challenges associated with testing antennas. For instance, there is a clear increase in the element count found within phased arrays. These elements facilitate more simultaneous functions and a narrower focus of the main lobe in beamforming. Furthermore, digital (broadband) signals are getting nearer to the antenna. Within the A&D sector, there is talk that the only connection to the transmit/receive (T/R) module for each element will eventually be a digital bus (no analogue).

The many faces of warfare

Electronic warfare can, of course, take many guises, including signal jamming, radar strikes and discrete signal detection. With regard to T&M solutions, engineers are relying on the latest signal generators and analysers. For instance, it is now possible to simulate increasingly complex signal environments for radar and electronic warfare with enhanced realism and confidence using an agile vector adaptor.

Turning to the satellite industry, the use of higher frequencies in communications links has become more common. Until now, most satellite communication has been performed in the C, L and Ku bands, which have limited spectrum. Instead, a number of satellite operators are now using, or considering, the Ka band (typically 27 to 40 GHz), as transmitting in this frequency range can be achieved using smaller antennas.

Test instrumentation evolution for aerospace & defence gathers pace_satellite dish
Test instrumentation evolution for aerospace & defence gathers pace_satellite dish

Among the clear challenges here is the requirement for test equipment that covers higher frequencies, which means more atmospheric attenuation. Uplinks are able to use higher frequencies, because power is available on the ground. Downlinks, on the other hand, are constrained, due to the relative lack of power available.

Numerous mmWave frequencies are deployed for crosslinks between satellites, especially those in high absorption bands, such as 60 to 65 GHz, as beyond the Earth’s atmosphere there are no issues with absorption. Communication using optical lasers is also gaining interest, not just for crosslink communications, but for links through the atmosphere.

Yet another market driver impacting the A&D sector is demand for higher data rates. To attain higher data rates, wider bandwidth signals and higher order modulation formats are being used, which in combination present test challenges.

Until very recently, many signal analysers were restricted to ~100 MHz of analysis bandwidth. Combining wide bandwidth with higher frequency signals makes it challenging to adopt traditional wideband test equipment, like oscilloscopes, which are perfectly adept at handling wider bandwidths, but not higher frequencies.

In short, T&M equipment requires good dynamic range to handle the low signal-to-noise ratio (SNR) issues seen typically in satellite testing. In addition, higher order modulation formats mean factors such as compression and small amplitude errors in the channel now have more potential to appear as a bit error. For this reason, test equipment must maintain the dynamic range and leave sufficient margin to help identify these issues.

A distinct shift towards smaller, more complicated payloads in the satellite sector is driving the development of more advanced T&M devices, capable of multiple communications strategies and measurements. Here, signal and spectrum analysers that prove most popular are those that can provide optimised sensitivity and low-phase noise, along with high internal and real-time analysis bandwidth.

During the validation of higher-level integrated assemblies and sub-systems, A&D sector companies opt for integrated test systems featuring both hardware and software. Examples for satellite testing include payload test stations, power and solar array simulator sub-systems, telemetry tracking and command sub-systems, as well as command and data handling sub-systems.

Software-defined instrumentation delivers flexibility, as it can be used to create a full solution for almost any T&M challenge, without resorting to costly custom systems that are restricted to single use-cases. Important attributes include: RF data throughput and streaming; channel density and scalability; flexibility in platform form factor; synchronisation infrastructure; and user-friendly access.

Broadband SATCOM testing is another growing trend. As these bands rise in popularity and need to transmit more data, more rigorous testing is necessary. For broadband SATCOM testing, the latest arbitrary waveform generators are able to generate complex simulated signals, based on optimised sample rate, waveform memory and signal fidelity. Such systems represent a signal stimulus solution for the simple production of ideal, distorted and ‘real-life’ signals.

Ultimately, choosing to work with an established, experienced and reputable technology provider like Microlease can pay real dividends in selecting the right T&M equipment, optimising its use and maximising return-on-investment (ROI). Regardless of whether the T&M equipment is needed for a short or long timeframe, Microlease can offer rent, lease or buy options across an extensive range of new or preowned equipment, as well as the option to use older test instruments in part-exchange. Rental is particularly useful where project needs change rapidly, as it offers access to equipment at short notice and for only as long as it’s needed. This avoids unnecessary capital expenditure, saving much needed capital for investment elsewhere.

The success of an A&D programme can often hinge on gaining access to various T&M equipment acquisition options. Sure enough, technical challenges can prove a headache, but project delays due to budgetary or equipment availability issues can be damaging, either financially or through reputation. Working with an independent expert T&M partner reduces these risks.

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