In a typical wireless system, field engineers and technicians are routinely faced with a wide variety of system elements that can cause failure in the overall system. Among the elements are antennas, cables, filters, multiplexers, amplifiers, isolators, circulators, switches, and low noise amplifiers. Other field personnel will be working on different RF/microwave systems that operate from the broadcast band to Ku-band radar.
Maintenance crews, both civilian and defense, often need to quickly evaluate and isolate faults in avionics packages without removing them from the airframe. In these instances, performance of the RF and microwave system is crucially dependent on a variety of high-precision components, many of which are subject to the long-term effects of weather and aging.
For example, cables, antennas, filters, and interconnects degrade over time due to corrosion, moisture intrusion, and normal aging processes.
Further, to optimize the coverage of a wireless communication system, the transmit and receive paths need signal separation components to prevent interference, to comply with industry spectrum masks, and to satisfy dynamic range needs.
Measurement and fine adjustment of two-port devices such as cavity filters, combiners, multiplexers, etc., (which are needed to mitigate co-location issues and allow systems to meet emission compliance standards) are tasks best done on-site, and often need to be completed in challenging environments, such as inside confined transceiver bays, near active flightlines, and on elevated perches on antenna towers.
Multi-instrument test solution
The complexity and diversity of measurements required to install and maintain wireless networks have created testing challenges. Engineers, technicians and other wireless professionals have traditionally relied on multi-instrument solutions that consisted of bulky benchtop instruments more suited for the production floor than the outdoors. Among the instruments typically used were a vector network analyzer (VNA), time domain reflectometer (TDR), modulation analyzer, and a spectrum analyzer.
A VNA is used to conduct S-parameter measurements on coaxial and waveguide components to identify degradations. Field personnel use the TDR to analyze cables for faults, including minor discontinuities that may occur due to a loose connection, moisture intrusion, corrosion, or other aging effects. Spectrum analyzers are required to analyze frequencies and detect interference sources. Spectrum analyzers that use modulation analysis show the performance of the system in terms of deviation, occupied bandwidth, emission compliance, sidebands, and other parameters.
Despite the ability for these test configurations to make the necessary measurements, there are limitations. As multiple instruments are necessary because many benchtop instruments are specialized and can not perform all the measurements, large and heavy “instrument carts” are configured. All of this makes it difficult – if not impossible – for a benchtop “solution” to be used in the field or in elevated/space-restricted environments. Adding to the complexity of using benchtop instruments in the field is the need to utilize AC extension cords or even portable generators to power the equipment.
Another problem with the use of benchtop instruments in the field is that their displays are not designed to be used in sunlight. In many instruments, the viewing angle is not optimal for field use, especially when working on systems with limited physical access. Seeing the results can be problematic, due to these factors.
From an investment standpoint, purchasing benchtop instruments for use in the field can make any purchasing agent a bit nervous. These expensive investments, which were never intended to be used in the field, are susceptible to damage and weathering due to the rugged outdoor environments in which they are used.
What field personnel responsible for the operation of wireless networks used in military, aeronautics, broadcast, and commercial applications require is a single instrument that is specifically designed for today’s stringent performance and comcompliance testing requirements. It must combine portability, durability, and extensive measurement capability and performance.