This paper introduces the first fully 3-D printed tunable microwave subsystem, consisting of 26 circuit elements. Here, a polymer-based 3-D printed Ku-band 4-element steerable phased-array antenna with fully integrated beam-forming network is demonstrated. Polyjet was adopted for fabricating the main body of the subsystem, as it is capable of producing a geometrically complex structure with high resolution over a large volume. Low-cost fused deposition modeling was chosen to manufacture the dielectric inserts and brackets for the phase shifters. The measured radiation pattern revealed that the phased-array antenna subsystem has total beam steering angles of 54 • and 52 • at 15 GHz and 17 GHz, respectively. Excellent input return loss behavior was observed across the optimum operational frequency range of 15 to 17 GHz, with a worst-case measured return loss of 12.9 dB. This work clearly shows the potential of using 3-D printing technologies for manufacturing fully integrated subsystems with complex geometric features.
We describe a method for direct intercomparison of terahertz permittivities at 200 GHz obtained by a Vector Network Analyzer and a Time-Domain Spectrometer, whereby both instruments operate in their customary configurations, i.e., the VNA in waveguide and TDS in free-space. The method employs material that can be inserted into a waveguide for VNA measurements or contained in a cell for TDS measurements. The intercomparison experiments were performed using two materials: petroleum jelly and a mixture of petroleum jelly with carbon powder. The obtained values of complex permittivities were similar within the measurement uncertainty. An intercomparison between VNA and TDS measurements is of importance because the two modalities are customarily employed separately and require different approaches. Since material permittivities can and have been measured using either platform, it is necessary to ascertain that the obtained data is similar in both cases.
NPL, PTB, and LNE designed and produced three different microcalorimeters for the WG29/WR7 band. The microcalorimeters used different correction methods to characterize effective efficiency. Finally, the three laboratories measured thermoelectric power sensors from 110 GHz to 170 GHz to demonstrate equivalence and results show good agreement.
The aim of this study is to examine the characterization of a thermal isolation section for a waveguide microcalorimeter, used to characterize the effective efficiency of a thermistor power sensor. The power loss in the thermal isolation section has been analyzed for both the dielectric and conductor losses. Its effect on the thermopile output has been assessed using a foil short method through analysis of the heating ratio. This method involves a one-off measurement of the microcalorimeter system with the foil short before the unknown power sensor measurement and does not require additional S-parameters measurements of the isolation section. The estimated value of the heating ratio effect has been obtained between 1 for fully reflected signal from the input of the unknown power sensor and 2 for perfectly matched power sensor. The full analytical model and an estimated model for the heating ratios have been calculated for NPL's WG25 (WR15) microcalorimeter and a commercial thermistor power sensor. The analytical model has been applied to an effective efficiency measurement and good agreement has been obtained when compared with the existing methodology used at NPL. This model can be applied to any metallic waveguide type thermal isolation section in other bands. A rigorous uncertainty analysis of the analytical model for the heating ratio is also presented and shows an expanded uncertainty between 0.008 and 0.023 (k=2) for this microcalorimeter.
This paper describes the design, fabrication and testing of 3-D printed primary standards for use with the calibration of microwave vector network analysers. The standards are a short-circuit and a quarter wavelength section of line that are designed for use with the Thru-Reflect-Line calibration technique. The standards are realised in metal-pipe rectangular waveguide, covering the frequency range from 12 GHz to 18 GHz (i.e., Ku-band). The standards are polymer-based 3-D printed, which is subsequently metal plated to provide the required electrical conductivity. The performance of the standards is compared with conventionally machined standards that are used as part of the UK's primary national measurement system for microwave scattering parameters. The authors believe that this is the first time that 3-D printing techniques have been used to produce such calibration standards, and, that this could lead to a new approach to providing metrological traceability for these types of measurement.
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