| 1. |
- Furtula, Vedran, 1981, et al.
(author)
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W-band waveguide bandpass filter with E-plane cut
- 2014
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 85:7, s. Art. no. 074703-
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Journal article (peer-reviewed)abstract
- In this paper, we present a design and measurements of a five-section bandpass filter with a passband from 96 to 106 GHz. The insertion loss is less than 1.4 dB in the passband, and the rejection is better than 40 dB in the range from 115 to 142 GHz. We use transmission line coupling theory based on Tchebyscheff's synthesis in order to provide an initial guess for the geometrical parameters of the filter such as cavity lengths and coupling widths. The filter is manufactured from brass in two halves in the E-plane cut topology. The S-parameters of the filter are measured and compared with the simulations. The measured passband insertion loss is approximately 0.4 dB worse than in the simulation, and the measured passband width is approximately 3.4% narrower. The measured filter attenuation roll-off corresponds well to the simulation. We also compare our S-parameter measurements of the E-plane filter with corresponding measurements of a very similar H-plane filter. The transmission and reflection characteristics of the E-plane filter are better than those of the H-plane filter.
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| 2. |
- Furtula, Vedran, 1981, et al.
(author)
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Waveguide Bandpass Filters for Millimeter-Wave Radiometers
- 2013
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In: Journal of Infrared, Millimeter, and Terahertz Waves. - : Springer Science and Business Media LLC. - 1866-6892 .- 1866-6906. ; 34:12, s. 824-836
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Journal article (peer-reviewed)abstract
- A fundamental requirement for most mm-wave heterodyne receivers is the rejection of the input image signal which is located close to the local oscillator frequency. For this purpose we use a bandpass filter, which for heterodyne receivers is also called an image rejection filter. In this paper we present a systematic approach to the design of a waveguide bandpass filter with a passband from 100 to 110 GHz and upper rejection bandwidth in the range from 113 to 145 GHz. We consider two non-tunable filter configurations: the first one is relatively selective with 11 sections (poles) whereas the second one is simpler with 5 sections. We used established design equations to propose an initial guess for the geometries of the filters, optimized the geometries, constructed the filters using two different milling methods, measured their transmission and reflection characteristics, and compared the measurements with numerical simulations. Measurements of both filters agree well with simulations in frequency response and rejection bandwidth. The insertion loss of the 11-pole filter is better than 10 dB and that of the 5-pole filter is better than 5 dB. The 11-pole filter has a sharper attenuation roll-off compared with the 5-pole filter. The upper out-of-band rejection is better than 40 dB up to 145 GHz for the 11-pole filter and up to 155 GHz for the 5-pole filter.
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| 3. |
- Moseev, D., et al.
(author)
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Elevation angle alignment of quasi optical receiver mirrors of collective Thomson scattering diagnostic by sawtooth measurements
- 2012
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:10
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Journal article (peer-reviewed)abstract
- Localized measurements of the fast ion velocity distribution function and the plasma composition measurements are of significant interest for the fusion community. Collective Thomson scattering (CTS) diagnostics allow such measurements with spatial and temporal resolution. Localized measurements require a good alignment of the optical path in the transmission line. Monitoring the alignment during the experiment greatly benefits the confidence in the CTS measurements. An in situ technique for the assessment of the elevation angle alignment of the receiver is developed. Using the CTS diagnostic on TEXTOR without a source of probing radiation in discharges with sawtooth oscillations, an elevation angle misalignment of 0.9 degrees was found with an accuracy of 0.25 degrees.
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| 4. |
- Vassilev, Vessen, 1969, et al.
(author)
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140-220 GHz Imaging Front-end Based on 250 nm InP/InGaAs/InP DHBT Process
- 2013
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819495068 ; 8715
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Conference paper (peer-reviewed)abstract
- This paper presents a pre-amplified detector receiver based on a 250 nm InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) process available from the Teledyne scientific. The front end consists of a double slot antenna followed by a five stage low noise amplifier and a detector, all integrated onto the same circuit. Results of measured responsivity and noise are presented. The receiver is characterized through measuring its response to hot (293) and cold (78) K terminations. Measurements of the voltage noise spectrum at the video output of the receiver are presented and can be used to derive the temperature resolution of the receiver for a specific video bandwidth.
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