Hardware Hands-On

Most of FCL's support to clients has included a significant proportion of 'hands-on' work. Laboratory based work has been necessary to verify performance to specification, to solve issues and to trial various improvement options. FCL has experience of these skills in many different laboratory environments including the examples described below.

Microstrip and Planar Circuits

Most of FCL's experience at RF and microwave frequencies has been with microstrip, stripline, co-planar waveguide (CPW) and combinations of these through various transitions. For the lower frequencies, operating at VHF and UHF, the dielectric substrate has usually been the industry standard type FR4. Many FR4 PCBs have been multi-layer architectures, sharing with DC and high speed digital circuits. In fact, it has been surprising how adequate FR4 has been for many clients' hardware realisations even up to several gigahertz. Being cheaper to produce than the others, sometimes the small compromise in RF performance that is necessary is quite tolerable. Attention to detail and strict design of features including controlled impedance lines, through hole technology, grounding and layout yields a product which works well. Where necessary, double sided PCBs have been used, with intelligent distribution of circuit function areas to each side to optimise performance generally, including isolation, EMC, ease of assembly and test. At the higher microwave frequencies FCL has also worked with dedicated low loss dielectric materials including the flexible 'Rogers' types and alumina. On circuits like these FCL has successfully solved many RF isolation, screening and EMC issues with techniques such as compartmentalisation, strict attention to layout and very good (low resistance and low inductance) grounding.   

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Hardware Debugging (Excessive Loss, Noise, Spurious, Jitter etc.)

FCL is often engaged to undertake hands-on debugging work. The problems solved have ranged from simple circuit breaks, excessive loss or excessive reflections through to eliminating some unusual spurious products caused by a strange mixture of harmonics and intermodulation products. For the biggest challenges, FCL has often verified proposed solutions by building, testing and documenting temporary modifications to existing hardware and then following these through to the formal engineering changes and production improvements. The debugging process is often performed at the same time as other circuit changes, enhancements or cost saving measures.

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Prototype Evaluation

FCL is sometimes required to support clients during the development and building of prototype hardware to tight timescales. Often this results from a commitment made to the customer by the client. The experience that FCL has acquired in similar industries enables it to rapidly provide this. FCL is familiar with many of the common types of RF and microwave test equipment such as vector network analyzers, spectrum analyzers, noise figure meters, power meters, oscilloscopes and dynamic signal analyzers. This extends to how to fully exploit their capability to produce reliable and accurate results including data extraction and instrument control over the general purpose interface bus (GP-IB/HP-IB/IEEE488) and TCP/IP (Ethernet® LAN). FCL has a good grasp of what can be done realistically and at what frequencies. Evaluation assignments like these frequently embody writing or updating design or test specifications. By replicating the proving tests FCL can often find ways to make the test engineer's job easier and more efficient.

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Demonstrator Construction

Several clients have used FCL to build and verify demonstration equipment whilst they concentrate on other priorities. FCL will likely have enough previous experience with similar equipment to quickly understand what the demonstrator is intended to do. With minimal supervision FCL can treat similar examples as a stand-alone project: assess the priorities such as long lead items and the fulfilment of commitments that the client has made, and get to work on it. Clients have then required FCL to play a central role in describing and demonstrating the equipment to review groups and potentially new customers.

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Thermal, Mechanical and Other Interfacing Issues

As well as the electrical aspects of a product, FCL also understands many of the non-electrical properties that are usually included in the product specification and have to be addressed at the same time. For example, calculations for power dissipations and heat transfer mechanisms by convection, conduction, radiation, and combinations of these. FCL is also conversant with the typical product physical properties such as mass, weight, moment of inertia and centre of gravity.

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Test Equipment: Interfacing and Automation

FCL has written source code modules in Microsoft Visual Basic 6®, Visual C++ 2010® and Matlab Instrument Server® for controlling test equipment and for extracting data for subsequent processing. Mostly, physical connections have been GPIB bus connections via cards installed into PC architectures or, more recently, universal serial bus (USB). FCL has also achieved highly effective control with various non-standard parallel and serial interfaces via PC based parallel and serial input output (PIO) cards. Some of this work has included S-parameter files in Touchstone (.snp) format.

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Locating Challenging Faults

Sometimes equipment fails to meet specification due to some particularly difficult parameter or perhaps at an extreme end of the operating temperature range. Alternatively there might be a specified requirement such as phase noise which just exceeds specification when all others pass with comfortable margins. FCL has experience of successfully finding and clearing many faults such as these. A very good understanding of the product is required: how it operates and was designed together with fully utilising the test equipment available, not always in the most conventional modes.

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Solar Radiation Tests

One product that FCL investigated, which was designed for operation in an external environment in the UK, was failing due to overheating at several of the customer's sites. Internal power dissipation was quite modest and convective cooling was thought to be adequate for the UK based on the predicted spread of ambient temperature. However further investigations revealed that insufficient margin had been allowed specifically for solar radiation heating, previously not thought to be of particular concern in a relatively cool climate. FCL quantified the level of solar heating expected by application of the Stefan Boltzmann 'fourth power' radiation law after making allowances for the surface emissivity, infrared spectral density, atmospheric absorption and integrated daily power flux. A representative unit was tested in the laboratory using solar lamps with suitable approximations. The effects of solar radiation were found to amount to several hundreds of watts equivalent power thus confirming the cause of overheating. Several recommendations were made for ways of reducing it.

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