Case study: Custom microwave switching for MRI ATE delivered to Philips on time, on budget & with uprated specs

Author : Steven Edwards | Switching Product Manager | Pickering Interfaces

01 August 2021


When the healthcare division of Dutch electronics giant & multinational conglomerate, Philips needed a replacement for a microwave multiplexer (MUX) switch used within its in-house automated test equipment (ATE) for medical imaging scanners, it faced the challenge of selecting a partner with the engineering expertise to develop such a part & the flexibility to deliver fast.

This case study was originally featured in the August 2021 issue of EPDT magazine [read the digital issue]. And sign up to receive your own printed and/or digital copy each month.

In this case study, Steven Edwards, Switching Product Manager at modular signal switching & simulation experts, Pickering Interfaces explains how it was able to deliver a custom microwave MUX switch for MRI ATE to Philips quickly and with uprated specs…

Philips Healthcare has a worldwide reputation for product quality and reliability. Central to the company’s functional ATE for its medical imaging product range was a GPIB-controlled 32:1 microwave multiplexer switch, which Philips had been using for several years. However, the product was being made obsolete by the manufacturer, so Philips had to find another solution. Also, the part ideally needed to be easily integrated within the existing ATE, and time was pressing. Philips’ preference was to find a supplier that could handle both hardware and software design, and produce a unit that used the same BNC front panel connectors as the existing switch.

Strict requirements

The magnetic resonance system comprises around 32 different coils, while the data acquisition has only one output, hence the need for an RF switch. The RF signal is less than 1MHz, but the challenge is to maintain the integrity of the waveform during switching. In other words, the wave shape containing higher frequency harmonics (pulse) must not be impacted by the switch.

Pickering Interfaces was already known to Philips Healthcare, but didn’t have such a switch module in its wide product range. However, when Pickering agreed to design one from scratch, Philips subsequently had two options:

 1. Copy the existing tester and integrate the new Pickering switch

 2. Design and build a brand-new system

Philips Healthcare ATE [shown in rack on left] containing Pickering’s LXI microwave MUX (Model 61-891-001-002) [switch front & top view shown on right]
Philips Healthcare ATE [shown in rack on left] containing Pickering’s LXI microwave MUX (Model 61-891-001-002) [switch front & top view shown on right]

While the second option offered lower cost, it would have taken too long to develop. A challenge with the first, and chosen, approach was that some of the pre-existing modules were difficult to replicate.

When designing the new switch module, Pickering used high spec 18GHz relays to ensure signal integrity was not degraded. The new design includes LED-energised path indicators that were not available on the original switch, and 36 mux (multiplex) channels were provided—four more than the original module—to allow for future expansion. Finally, Pickering’s engineering team was able to produce the unit in a 2U high rack-mountable enclosure, 1U less than the unit it replaces.

Software was developed and evaluated at Philips using Pickering’s LXI simulation tool (model 60-901), configured with the new switch. The LXI simulator accelerated the development and integration process by providing real-time hardware-like feedback, which helped the engineers at Philips develop and verify their code effectively.

To ensure that no additional changes were needed on the users’ LabVIEW™ application, Pickering provided specific versions of LabVIEW drivers, which integrated seamlessly in their application. Along with the driver, Pickering also provided different example programs and remote training sessions to ensure a smooth transition.

To date, four of the new LXI microwave multiplexer modules have been delivered to Philips Healthcare. Harrie van den Oever, Electrical Engineer at Philips commented: “We are very happy with the result. This was a complex challenge, but now we have a better system that is 100% compatible with our established working practices – and Pickering delivered it on time and on budget.”

Turnkey LXI microwave switch & signal routing subsystem service

Since the development with Philips Healthcare, Pickering has formally launched its turnkey LXI microwave switch and signal routing subsystem service, delivering custom-engineered solutions, such as this one, created to customers’ specifications. Integrated microwave test packages include switches, Switch Path Manager signal routing software, dedicated soft front panels, all the wiring and more in a suitable enclosure, and supplied fully tested, with documentation and a three-year warranty.

Pickering_Philips Healthcare_MRI ATE LXI MUX
Pickering_Philips Healthcare_MRI ATE LXI MUX

The service provides compact, rack-mount multiplexer and matrix designs based on an industry-standard LXI/Ethernet interface, designed and manufactured by Pickering’s team of switching experts. Solutions are available with bandwidths from DC to 67 GHz @ 50?, with terminated or unterminated options (bandwidths up to 2.5 GHz @ 75 ?).

These cost-effective microwave test packages are available on a fast turnaround and are fully documented to ensure performance repeatability in subsequent engagements. Pickering’s familiar standard switch API programming environment accelerates software integration.

Keith Moore, CEO at Pickering Interfaces comments: “This is an exciting new business direction for Pickering. More and more, our customers are asking for out-of-the-box solutions that are complete and ready-to-run with minimal fuss and set-up time. We have the expertise and ability to turn your high-level requirements for a microwave switching subsystem into a fully integrated solution. You provide us with your unique configuration and specification. Our engineers will work closely with you to provide a well-defined and supportable end product that delivers everything a microwave test engineer needs to get a complex microwave test system up and working first time.”

Also, Pickering can turn a custom design into an ‘off-the-shelf’ product, offering product support for more than 15 years. Pickering also offers other microwave switching configurations and is developing a range of additional turnkey switching and signal routing subsystems, which will similarly be tailored to suit a customer’s needs, and offered as a boxed system solution for fast and simple installation.

In addition to microwave switching elements, a custom system may include alternate components such as couplers, splitters, attenuators or amplifiers that can be interconnected to form a fully integrated solution, minimising test system construction time.

A further expansion of the turnkey service combines electrical and optical switching in a single system to provide users with the capability to route DC to light signals. Our range of high-quality MEMS fibre optic switches (single and multi-mode), used in dedicated PXI or LXI products, can now be included, along with microwave switching & non-switching RF components to address specific custom requirements.

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