As known RF stands for Radio Frequency. Radio is the electromagnetic waves whose frequencies are below 3,000 GHz as defined in Article 2 of the Radio Law in general. However, in practice, radio is generally referred to as electromagnetic waves whose frequencies are between 10 kHz and 300 GHz.
Microwave (MW hereafter) is the electromagnetic waves in the frequency range of 1 to 30 GHz. Microwave-based networks are an evolving technology gaining favour due to high bandwidth and relatively low cost.
Both technologies are finding new applications in moderns science from communication to industrial use to drone (UAV) control to Internet of things (IoT) to medical healthcare to smart wearables, satellite communication, signal integrity, RFID and many more.
Many medical electronics systems such as magnetic resonance imaging (MRI) systems for cancer detection rely on RF/microwave technology. RF/microwave technology enables diagnostic imaging systems, electrosurgical devices, patient and equipment monitoring, and overall medical facility connectivity.
Radio frequency engineering continues to help drive the world across many applications right from smartphones to aeroplanes to ships or mission critical communication and so on…
Entire world is surrounded with RF WM waves!!
RF MW technology use many instruments such as Signal Generator, Spectrum Analyser, Power Meter and Sensors, Signal Analyzer in addition to VNA. We will cover Vector Network Analyser (VNA) as key RF MW technology Test & Measurement Instrument in this article.
What is VNA and its type:
Vector Network Analyzer -VNA’s are test and measurement instrument for measurement of transmission and reflection of various RF MW components, accessories, systems, modules etc. Here network means device with 1 port or more.
Transmission measurements pass the Vector Network Analyzer stimulus signal through the device under test, which is then measured by the Vector Network Analyzer receivers on the other side. The most common transmission S-parameter measurements are S21 and S12. Transmission measurements include gain, insertion loss/ phase, electrical length/delay and group delay in addition to swept power measurement. Comparatively, reflection measurements measure the part of the VNA stimulus signal that is incident upon the DUT but does not pass through it. Instead, the reflection measurement measures the signal that travels back towards the source due to reflections. The most common reflection S-parameter measurements are S11 and S22.
VNA can be either 1 port or 2 port type and now more than 2 ports are also in demand for specific applications. VNA can also be differentiated by form factor as well such as – handheld VNA and Benchtop type. Handheld VNA’s are small in size, lower in cost and battery operated in addition to mains power supply operated. While on the side benchtop VNA’s are bigger, more in weight, operate on main power supply. Both types of VNA have focus application area and successful.
Recently PC based or USB VNA are seen in market and getting popular. These are useful when economical, cost-effective solutions are in demand. Anritsu Shockline VNA is from this category. Shockline VNA are based on NLTL- Nonlinear Transmission Line (NLTL) technology. In general terms, NLTLs are distributed devices that support the propagation of nonlinear electrical waves such as shocks and solitons.
The use of NLTL-based samplers offers a number of benefits to modern VNA architectures (Table). These benefits provide customers with an unparalleled value per GHz for their investments.
|Parameter||NLTL-Based VNA Advantage||Customer Benefit|
|Simplified VNA architecture||Monolithic reflectometer design reduces number of discrete parts and connectors||Lower maintenance cost, reduced down time and operating costs.|
|Stability||Integrated chip design greatly reduces the temperature variation across reflectometer constituents||Longer intervals between calibrations, better measurement accuracy and repeatability|
|Bandwidth||Extremely wide RF sampler bandwidth allows one sampler to cover broad frequency range||Lower cost for making high-performance measurements over broader frequency ranges|
|Dynamic Range||Over 100 dB across all frequency ranges||Better characterization of highly reflective devices and weak crosstalk.|
|Size||High performance in a very small form factor||Direct connection to wafer probes, smaller footprint in manufacturing, light weight field solutions|
|Cost||Improved capability-to-cost ratio enables new applications||Dramatic cost reduction for high frequency testing in engineering, manufacturing and field|
Key VNA Applications:
Vector Network Analyzers (VNAs) are used to characterize a wide range of devices, ranging from 2-port passive devices, such as filters, to complex subsystems consisting of a combination of passive and active components. Moreover, the device under test (DUT) can vary from a connectorized and packaged format to on-wafer; even to raw materials and free-space antenna measurements.
Today’s VNAs address a wide and growing range of applications, from aerospace/defense and astronomy to high-speed serial data and homeland security. The following are some applications in which VNAs are used:
- Wafer-level characterization of active and passive devices
- Characterization of packaged or connectorized amplifiers and other active components (both linear and non-linear)
- Characterization of frequency translation components
- Characterization of passive components, such as filters, diplexers, etc.
- Characterization of high-speed serial interconnects, such as backplanes, cables and connectors
- Materials characterization
- Antenna characterization
Trends in RF MW VNA:
5G evolution and acceptance has increased VNA role in telecom industry. 5G Antenna characterization work has VNA demand in market. VNA are used from user device design validation to network antenna validation, production testing. Machine to Machine (M2M) communication will be leading technology in industrial market. All such machine will have some kind of connectivity and VNA will be key tool to characterise many components in devices and network. Internet of Things (IoT), Industrial IoT, Location Based Services (LBS) Goods Tracking, RFID, EV are emerging market for VNA applications.
High speed network, devices have opened new opportunities for VNA, and Signal Integrity is new application area for VNA.
Autonomous Cars/Vehicles have opened new doors for VNA. Automotive Industry is using following types of RADARs for many applications.
Radar systems typically fall into three categories:
- Short-range radar (SRR) and Ultra-wideband SRR (UWB SRR): SRR and UWB SRR systems, with a shorter range of 0.5 to 30 meters, are more typically used in advanced driver-assistance systems (ADAS). These radar systems began in the 21.65- to 26.65-GHz frequency range, but they have already migrated to 77 to 81 GHz in Europe and will do the same in the U.S. by 2021. This frequency change will affect the mounting of SRR and UWB SRR sensors on the car chassis.
- Long-range radar (LRR): Typically, the LRR system is designed for an angular range of up to ±10° and a distance of 10 to 150 meters, which enables the adjustment of the automobile’s velocity between 20 MPH to 110 MPH. Measuring automotive radar systems requires proper configuration and calibration to achieve accurate results. A typical calibration method employed for these radiated measurements is the Line, Reflect, and Match (LRM) algorithm, in which a reflection plane is applied for reflective calibration, a line for transmission calibration, and an excellent match for load calibration.
Anritsu VNA has been used for EV industry as well.
Signal Integrity (SI)
Signal integrity addresses the losses and types of signal degradation that can happen along the signal path (channel) between a transmitter and a receiver. Signal integrity is becoming more and more important as digital signal speeds and analog frequencies are rapidly increasing making circuits much more sensitive to any losses or variations in the path. This eBook provides information and instruction on making accurate signal integrity measurements with emphasis on the VNA as a tool.
Higher data rates introduce new challenges for test solutions. There are several 20+ Gbit/s high speed standards that are driving the upper end of the test spectrum from 40 GHz all the way up to 110 GHz and beyond. Along with the design trade-offs related to choices of vias, stackups, and connector pins, accurate measurements are needed to better understand new challenges related to conductor skin effects and dielectric losses on PC boards. For many of these measurements, it is necessary to collect data that includes higher value harmonic frequencies.
VNAs are useful in characterizing channels as a means of comparing measured S-parameters to the ones that have been modelled in an EDA software package like HFSS or Microwave Office. Having high quality S-parameters are key in making the measured and modelled results agree; more on determining the quality of S-parameters later in the article Using the time domain mode, they are useful as a troubleshooting and verification tool to look at defects in channels. They can also be used to probe these channel structures for actual impedance measurements of the inaccessible structures, like PCB vias, and can help detect internal cable and connector defects. This application also needs eye diagram results in VNA and new VNA have this feature available. De-embedding is other feature is SI applications.
Optoelectronic Device Characterization- E/O & O/E
To satisfy next-generation device bandwidth requirements, technologies are being developed that require the use of extremely high frequencies. One such technology is opto-electronics, which offer enormous bandwidth, low latency, and is commercially viable. The demand for testing these opto-electronic devices precisely is a big challenge today. Anritsu’s ONA solution provides accurate and precise measurements with NIST traceability of these opto-electronic devices. Opto-electronic device characterization is another target area for Anritsu’s VectorStar® based ONA systems. Upgradability, flexibility and NIST traceability in measurement results are some of the unique offerings that help our customers.
As fiber and free-space optical communication bandwidths increase, the need for very high-speed optical modulators and detectors has also increased. The frequency response characterization of these electrical-to-optical (E/O, modulators sometimes integrated with lasers) and optical-to-electrical (O/E, detectors and receivers) converters can be important in terms of such parameters as bandwidth, flatness and phase linearity. The VNA has several measurement utilities to facilitate this kind of analysis and, coupled with an O/E calibration module, some level of measurement traceability is possible.
Defence, Satellite, Electronic Warfare, UAV:
VNA played a very important role in technical advancement in all above market. Many defence labs are working on various material research using VNA. Soldiers’ cloth material, aircraft, land vehicles paint properties etc are characterised using VNA.
Satellite Communication will increase in coming years, and it will be key medium to connect unconnected people across world, provide broadband. Space race is on, and many components are tested using VNA. We see RF and Microwave (MW) technology will be in demand in future and VNA technology architecture will evolve with time and technology.