Precision waveguide system for measurement of complex permittivity of liquids at frequencies from 60 to 90 GHz

Abstract

We describe a variable path length waveguide setup developed to accurately measure the complex dielectric permittivity of liquids. This is achieved by measuring the complex scattering parameter of the liquid in a waveguide section with a vector network analyzer in combination with an E-band frequency converter. The automated measurement procedure allows fast acquisition at closely spaced intervals over the entire measurement bandwidth: 60-90 GHz. The presented technique is an absolute method and as such is not prone to calibration errors. The technique is suited to investigate low-loss as well as high-loss liquids in contrast to similar setups described previously. We present measurements for a high-loss liquid (water), an intermediate-loss sample (ethanol), and for nearly loss-less n-octane. Due to the available phase information, the present data have an improved accuracy in comparison with literature data.

Water-mediated interactions between trimethylamine-N-oxide and urea

“…22 At 0.4 t n/THz r 1.6 we use an optical setup based on the propagation of single cycle THz pulses in the sample, generated and detected in non-linear ZnTe crystals (terahertz time-domain spectroscopy). 25 To cover frequencies at (0.3 t n/GHz t 70) we use a Vector Network Analyzer (Rhode & Schwarz ZVA67 & Anritsu MS4647A) to measure the complex reflection coefficient at an open-ended coaxial probe, which is in contact with the sample. 23,24 At frequencies ranging from 25 GHz to 90 GHz we use two variable path length waveguide reflection cells connected to a Vector Network Analyzer (Rhode & Schwarz ZVA67 & ZVA-Z90E).…”

“…23,24 At frequencies ranging from 25 GHz to 90 GHz we use two variable path length waveguide reflection cells connected to a Vector Network Analyzer (Rhode & Schwarz ZVA67 & ZVA-Z90E). 25 To cover frequencies at (0.3 t n/GHz t 70) we use a Vector Network Analyzer (Rhode & Schwarz ZVA67 & Anritsu MS4647A) to measure the complex reflection coefficient at an open-ended coaxial probe, which is in contact with the sample. 24 At frequencies ranging from 0.1 GHz to 2 GHz we measure the permittivity spectra using a coaxial cut-off type measurement cell connected to a Vector Network Analyzer (Rhode & Schwarz ZVA67).…”

Microwave resonant sensor for measurement of ionic concentration in aqueous solutions

“…This calls for compensation, and one approach adopted is to ensure that the sample liquid is in sufficient quantity to absorb all the RF power, effectively making the sample infinitely long, thus doing away with the impact of a nonideal short [53]. A fairly recent implementation of a waveguide based method for dielectric characterization of liquids in the frequency range of 60-90 GHz, which spans parts of the V (40-75 GHz) and W (75-110 GHz) bands of the frequency spectrum, has been demonstrated in [61].…”

“…This would also require the sensor to interface well with the sample. [61], and the work has been closely followed to come up with the approach for the current problem.…”

Loaded waveguide measurements of plastic explosives at V-band

“…The loaded waveguide technique for permittivity measurements has been used to characterize solid materials such as plastics, 11 glass, 12 and concrete, 13 as well as liquid and granular materials. 14,15 Use of waveguides for permittivity measurements has also been adopted as an ASTM standard method. 16 When coupled with the aforementioned challenges to using other techniques, the loaded waveguide technique is particularly attractive for semi-solid explosives.…”