High speed of > 5000 dual-port s-parameters per second
‘Quad RX’ four-receiver architecture for optimal accuracy
118 dB dynamic range at 10 Hz bandwidth
0.005 dB RMS trace noise at bandwidth of 140 kHz
Compact half-rack, lightweight package
3 year warranty
PC-controlled over USB using Windows software
Reference plane offsetting and de-embedding
Time domain and port impedance transformations
Tabular and graphic print and save formats, including Touchstone
P1dB, AM to PM, and stand-alone signal generator utilities
Fully accessible guided 8 and 12-term calibration processes
6 calibration modes, including unknown thru and connected DUT isolation
Making vector network analysis accessible
Today's microwave measuring instruments need to be straightforward, accurate, portable and affordable. No longer restricted to specialists, they are now used by scientists, educators, surveyors, inspectors, engineers and technicians in radio and gigabit data applications. Now Pico Technology has applied its expertise in microwave sampling oscilloscopes and time domain transmission and reflectometry to bring you a USB vector network analyzer.
The PicoVNA 106 is a professional USB-controlled, laboratory grade vector network instrument of unprecedented performance, portability and affordability. Despite its small size and low cost, the instrument boasts a ‘Quad RX’ four-receiver architecture to eliminate the uncorrectable errors, delays and fragility of three-receiver designs with internal transfer switches.
The PicoVNA 106 offers exceptional dynamic range of 118 dB and only 0.005 dB RMS trace noise at its maximum operating bandwidth of 140 kHz. It can also gather all four s-parameters at every frequency point in just 190 µs; in other words a 500 point 2-port .s2p Touchstone file in less than one tenth of a second. The cost is so low that the PicoVNA 106 could even be used as a cost-effective high-dynamic-range scalar network analyzer! It's affordable in the classroom, small business and even amateur workshop, yet capable in the microwave expert's laboratory.
Vector network analysis everywhere
With all these advantages, the PicoVNA 106 is ideal for field service, installation test and classroom applications. Its remote automation interface extends its use to applications such as:
Test automation or the OEM needing to integrate a reflectometry or transmission measurement core, in:
Electronics component, assembly and system, and interface/interconnect ATE (cable, PCB and wireless)
Material, geological, life-science and food science tissue imaging or penetrating scan and radar applications
Inspection, test, characterization or calibration in the manufacture, distribution and service center industries
Broadband cable and harness test at manufacture, installation and fault over life
Antenna matching and tuning
PicoVNA 106 features
‘Quad RX’ four-receiver architecture
In a VNA a swept sine-wave signal source is used to sequentially stimulate the ports of the interconnect or device under test. The amplitude and phase of the resultant transmitted and reflected signals appearing at both VNA ports are then received and measured. To wholly characterize a 2-port device under test (DUT), six pairs of measurements need to be made: the amplitude and phase of the signal that was emitted from both ports, and the amplitude and phase of the signal that was received at both ports for each source. In practice this can be achieved with a reasonable degree of accuracy with a single source, a transfer switch and two receivers; the latter inputs being switched through a further pair of transfer switches. Alternatively three receivers can be used with an additional input transfer switch or, as in the PicoVNA, four receivers can be used. Using four receivers eliminates the receiver input transfer switch errors (chiefly leakage and crosstalk) that cannot be corrected. These residual errors are always present in two- and three-receiver architectures and lead to lower accuracy than that of the Quad RX design.
Support for 8 and 12-term calibration and the unknown thru
Almost all vector network analyzers are calibrated for twelve error sources (six for each signal direction). This is the so-called 12-term calibration, which experienced VNA users are used to performing fairly regularly. In a four-receiver design some error sources are so reduced that 8-term calibration becomes possible, along with an important and efficient calibration technique known as the unknown thru. This gives the ability to use any thru interconnect (including the DUT) during the calibration process, vastly simplifying the procedure and reducing the number of costly calibration standards that need to be maintained.
Advanced vector network analyser users will be pleased to know that internal a-wave and b-wave data is made available for export under a diagnostic facility. Amongst others, Transfer switch error terms can therefore be derived.
Bias-Ts are often not provided, or available as costly extras, on other VNAs. Use the PicoVNA 106’s built-in bias-Ts to provide a DC bias or test stimulus to active devices without the complexity and cost of external DC-blocks. The bias is supplied from external power supplies or test sources routed to the SMB connectors adjacent to each VNA port.
Test cables and calibration standards
A range of RF and Microwave accessories are available from Pico Technology. Test cables and calibration standards have particular significance to the overall performance of a VNA, so we recommend that you select your accessories carefully. Cables and standards are often the weakest links in a VNA measurement, generally contributing significantly to measurement uncertainty despite their high cost. At the lowest levels of uncertainty, costs can be significant and measurements can be compromised by seemingly quite minor damage or wear. For these reasons, many customers hold both premium-grade items for calibration, reference or measurement standards, and standard-grade items as working or transfer standards and cables. Pico Technology can now offer cost-effective solutions in both grades.
Phase- and amplitude-stable test leads
Two test cable types and grades are recommended and provided by Pico Technology. Both of high quality, with robust and flexible construction and stainless steel connectors, the main difference between them is the stability of their propagation velocity and loss characteristic when flexed; that is, the degree to which a measurement could change when the cables are moved or formed to a new position. Cables are specified in terms of flatness and phase variation at up to 6 GHz when a straight cable is formed as one 360° turn around a 10 cm mandrel.
PicoVNA 2 softwarePicoVNA 2 presents standard VNA measurement and calibration simply, intuitively and with efficient usage at its heart. The software offers a comprehensive range of measurements and plot formats in its one, two or four user-configurable measurement channels. All the standard vector network analyzer functions can be seen at a glance.
The PicoVNA 2 software supports a comprehensive range of calibration modes to address single or dual-port workload with male, female or mixed gender interfaces, all with best achievable accuracy (least uncertainty). In some instances only a single calibration kit may be required. As you would expect, the Pico calibration kits are individually serial-numbered and supplied with S-parameter data. This standard-form data is a traceable and accurate record of measured errors for the calibration kit. It can be loaded into the software, which will correct for these errors and those of the instrument during a calibration. Alternatively, you can use a third-party calibration kit and its data, or you can enter its electrical length, parasitic values and polynomial coefficients into the software if these are supplied rather than a profile data set. As for any vector network analyzer, for best accuracy a calibration is performed before a measurement with the same sweep span and frequency steps as the measurement. If, however, a change of sweep settings is necessary for a measurement, the PicoVNA 2 software will for convenience interpolate its corrections to the new sweep settings. An enhanced isolation calibration setting is available for optimum dynamic range when using resolution bandwidths below around 1 kHz.
Reference plane extension
Reference plane extension (offset) allows you to shift the measurement reference plane away from the point established during calibration. This is useful in removing the path length of assumed ideal interconnecting , connectors cables or microstrip lines from measurements. The PicoVNA 2 software allows independent reference plane extensions on each of the measurement parameters (S11, S22, S12 or S21), either as an automatic re-reference or by manual entry. Independent extensions allow, for example, different extensions on the two ports for S11 and S22 and then thru-line normalization for S21 and S12 transmission comparison with equivalent length thru-line.
De-embedding embedded port interfaces
When it is unsafe to assume the above ideal interconnecting connectors cables or microstrip lines; for example to achieve greater accuracy or to remove known imperfections in a test setup, we can choose instead to de-embed the interface networks on each measurement port. The PicoVNA 2 software simply requires a full Touchstone .s2p file for the embedded interfacing network on each port. Likewise, defined networks can be embedded into the measurement to achieve a desired simulated measurement. As for a calibration, best accuracy will be achieved when the embedding network is defined at the same frequency points as the intended measurement. Unusually for a vector network analyzer, the PicoVNA 2 software will interpolate where necessary and possible.
Z0 impedance reference
System measurement impedance (default 50 Ω) can be mathematically converted to any value between 10 Ω and 200 Ω. The PicoVNA 2 software also supports the use of external matching pads and calibration in the new impedance using a calibration kit of that impedance.
Time domain transmission and reflectometry measurements
Time domain reflectometry is useful in the measurement of a transmission line; in particular the distance-to-fault location of any discontinuity due to connectors, damage or design error. To achieve this, the PicoVNA 2 software determines from its frequency domain measurements the time domain response to a step input. Using a sweep of harmonically related frequencies, an inverse fast Fourier transform of reflected frequency data (S11) gives the impulse response in the time domain. The impulse response is then integrated to give the step response. Reflected components of the step, occurring at measurable delays after excitation, indicate the type of discontinuity and (assuming a known velocity of propagation) the distance from the calibration plane. A similar technique is used to derive a TDT (time domain transmission) signal from the transmitted signal data (S21). This can be used to measure the pulse response or transition time of amplifiers, filters and other networks. The PicoVNA 2 software supports Hanning and Kaiser–Bessel lowpass filtering on its time-domain IFFT conversions, preserving magnitude and phase, and achieving best resolution. A DC-coupled DUT is essential to the method.
The 1 dB gain compression point of amplifiers and other active devices can be measured using a power sweep, either at a test frequency or over a sweep of test frequencies. The VNA determines the small-signal gain of the amplifier at low input power, and then increases the power and notes the point at which the gain has fallen by 1 dB. This utility uses a second-order curve fit to determine interpolated 1 dB compression points.
AM to PM conversion utility
AM to PM conversion is a form of signal distortion where changes in the amplitude of a signal produce corresponding changes in the phase of the signal. This type of distortion can have serious impact in digital modulation schemes for which amplitude varies and phase accuracy is important.
Limit lines testing
The limit lines facility allows six segments to be defined for each displayed plot. These can be extended to 11 segments using an overlapping technique. Visual and audible alarms can be given when a limit line is crossed. All plot formats except Smith chart and polar support limit testing. Peak hold functions are also available.
The PicoVNA 2 software provides an ActiveX server, allowing you to write your own software to communicate with the PicoVNA Vector Network Analyzer on Microsoft Windows platforms.
Example code is available via our GitHub organization page, including a toolbox for use with MathWorks MATLAB.
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