For many years Eravant has developed advanced millimeter-wave test systems to support a wide range of manufacturing activities. Leveraging this wealth of Test and Measurement experience, Eravant offers the industry its own VNA frequency extenders, calibration kits, contactless waveguide flanges, and sliding-rail test fixtures. When these innovative products are combined with modern VNAs they enhance mm-wave test systems with increased flexibility and productivity, improved reliability, and minimal risk of damage to the waveguide interfaces on calibration standards and tested devices.
STO FREQUENCY EXTENDERS
Eravant’s millimeter-wave frequency extenders for Vector Network Analyzers are offered in seven waveguide bands from WR-15 (50 to 75 GHz) to WR-03 (220 to 330 GHz). They are normally supplied as pairs of Transmit/Receive (TX/RX) units. The paired extenders provide full two-port VNA measurement capability (Fig. 1). Alternatively, the extenders are available individually with the choice of TX/RX, Transmit-Only, or Receive-Only configurations.
Fig. 1 – A pair of TX/RX frequency extenders provide full two-port VNA measurement capability.
For each TX/RX module, an RF test signal is provided by the VNA. The RF signal is multiplied by the extender to produce the mm-wave test signal (Fig. 2). An LO signal from the VNA is also multiplied and applied to a pair of mixers that down-convert the sampled Incident and Reflected signals. As a stand-alone unit, a single TX/RX extender can only measure S11 for the Device Under Test. Two TX/RX extenders can measure all four scattering parameters (Fig. 3).
Fig. 2 – TX/RX frequency extenders use directional couplers to sample Incident and Reflected signals.
Figure 3 — Signal flow diagram for a pair of TX/RX frequency extenders
A Receive-Only (RX) frequency extender only samples the incoming test signal. No outward-going test signal is generated. When used with a TX/RX extender, the pair can measure both S11 and S21. The pair can measure S21 and S22 as well by reversing the DUT.
A Transmit-Only (TX/Ref) frequency extender samples the outgoing test signal but not the reflected signal. When used with an RX extender, the pair measures the DUT response without correcting mismatch errors at the input and output ports of the DUT.
Eravant’s STO family of VNA frequency extenders are compatible with a range of VNA models including the Keysight PNA-X series, Copper Mountain C4220 and 4420 models, the Rohde & Schwarz ZVA series, and Anritsu VectorStarTM models. A compatible VNA must have dual sources for the RF and LO signals and provide access to its IF channels. It must also support programmable offsets between the RF and LO frequencies. VNAs that meet these criteria usually provide straightforward setup procedures to accommodate a variety of frequency extender models. Measured data is stored and displayed using appropriate frequency scales.
Eravant’s frequency extenders can achieve a measurement dynamic range of 120 dB or more for testing directional couplers, ortho-mode transducers, filters, and other devices with high levels of signal rejection or isolation. To avoid over-driving sensitive components, an integrated variable attenuator can be used to reduce the test signal power. The attenuator is positioned internally between the RF frequency multiplier and the first directional coupler.
STQ-TO CALIBRATION KITS
To further support VNA test systems operating at mm-wave frequencies, calibration kits are offered covering waveguide bands from 50 to 330 GHz (Fig. 4). The STQ-TO series of calibration kits are designed and manufactured for metrology-grade work and are compatible with all industry-standard VNAs. Each calibration kit consists of one fixed short, one matched load, and three waveguide shims (⅛, ¼, and ⅜ wavelengths). The calibration standards are made from durable beryllium copper with hard gold plating. They provide superior levels of electrical and mechanical performance over a long lifetime. Optionally, the calibration kits may include a pair of Quick-Connect waveguide flange clamps or a pair of Proxi-Flange™ contactless waveguide flange adapters. Nominal calibration coefficients are provided on a USB drive. Optional NIST-traceable calibration coefficients are available for an added fee.
Figure 4 – VNA calibration kits are provided in a durable carrying case
Proxi-Flange™ Contactless Waveguide Flanges
To further enhance mm-wave VNA performance, Eravant developed a series of contactless waveguide flange adapters for test systems that require frequent waveguide connections. When placed in close proximity to another waveguide flange, the contactless flange creates a highly effective RF choke that surrounds the waveguide interface. The contactless flange eliminates the need for near-perfect mechanical connections between flanges to achieve low-loss electrical connections. The technology is trademarked as Proxi-Flange™ (Fig. 5). The STQ-WG series of contactless flange adapters are offered in waveguide bands covering frequencies from 50 to 330 GHz. The adapters are constructed using beryllium copper with hard gold plating to yield repeatable and long-lasting electrical performance.
Fig. 5 – The contactless flange eliminates the need to engage screws in calibration and test procedures
Wave-GlideTM VNA Rail System
Eravant’s Wave-GlideTM product is a rail-guided positioning system that maintains mechanical alignment between pairs of frequency extenders (Fig. 6). Electrical connections between the VNA and the DUT are made with much greater speed and far less effort, reducing operator fatigue and improving measurement accuracy and reliability.
Fig. 6 – Wave-GlideTM VNA rail systems maintain extender alignment and simplify DUT handling
The rail system is compatible with all Eravant VNA frequency extenders, as well as extenders manufactured by Rohde and Schwarz, Farran, and Virginia Diodes (VDI). The mounting plates can be customized to meet the requirements of other devices.
Alignment of the VNA extenders is achieved using a straightforward process that is aided by an alignment fixture provided with the rail assembly. Precision tuning mechanisms compensate for small manufacturing tolerances in the assembled test system. The standard Wave-GlideTM rail configuration accommodates two-port devices with in-line waveguide ports. For other DUT configurations, customized adapter plates or separate rails for each extender may be used.
Conclusion
Eravant VNA frequency extenders provide leading levels of electrical and mechanical performance with competitive prices and relatively fast delivery. They are compatible with many extendable VNAs manufactured by Anritsu, Copper Mountain, Keysight, and Rohde & Schwarz. The extenders are complemented by Eravant’s metrology grade calibration kits, as well as Proxi-Flange™ contactless waveguide flanges and Wave-GlideTM VNA rail systems. All of these products are employed by Eravant internally to manufacture high-performance mm-wave and THz components for a variety of advanced applications. As a result, Eravant’s frequency extenders, calibration kits, contactless flange adapters, and rail positioning systems can be relied upon to support high-volume component testing operations while achieving superior levels of measurement accuracy, manufacturing productivity, and test system longevity.
More information about the Eravant Contactless Waveguide flange and Wave-Glide™ rail system can be found in the following links for further reading.
Contactless Waveguide Flange & mmW-THz Test Setup Applications: Proxi-Flange™ and Wave-Glide™