A Novel Hybrid-Channel Attenuation Measurement System at 50–110 GHz
A novel hybrid-channel attenuation measurement system has been built for the measurement of Vand W-band waveguide attenuators from 50 to 110 GHz. The measurement system combines two single channels of the V and W bands together into one system. The V-band channel is used as the measurement channel and the W-band channel is used as the synchronization channel when the V-band attenuator is measured and vice versa. The measurement system is free of cross talk between the two channels and removes the need for isolators between the local oscillator and the mixer since the RF signal frequencies in the two channels are different. In addition, a compensation module was designed to cancel the self-mixing produced by the W-band mixer at frequencies above 102 GHz. The expanded uncertainty of the system is evaluated to be 0.004-0.08 dB at frequencies ≤102 GHz and 0.005-0.11 dB at frequencies 102 GHz for an attenuation range from 0 to 80 dB.
Photoacoustic Substitution Method for Calibrating Subterahertz Attenuation in Free Space
A terahertz (THz) attenuation calibration system is developed using a photoacoustic (PA) detector for free-space beams. Based on the principle of the PA detector, the system measures the THz attenuation by substituting radio frequency (RF) attenuation with audio frequency (AF) attenuation. The AF attenuation at 1 kHz is directly calibrated using an inductive voltage divider (IVD) as the reference standard. The calibration is demonstrated for metalized film attenuators up to 20 dB at 0.11 THz. A Gunn oscillator with a corrugated horn antenna is used as the source, and its radiated beam is collimated using an off-axis parabolic mirror. Sources of uncertainties are also discussed in detail, and the expanded uncertainty is found to be 0.40–0.46 dB ( $k = 2$ ).
A 33-110-GHz Millimeter-Wave Loss Scanner
A broad-band microwave measurement system has been designed to make insertion-loss measurements on a swept basis at millimeter wave frequencies. This instrument covers a frequency range of 33-110 GHz in three waveguide circuits, using WR-22, WR-15, and WR-10 waveguide components. Small variations in loss can be displayed and measured with a resolution of ??0.01 dB and an accuracy of ??0.08 dB while sweeping over frequency ranges as wide as 10 GHz. Insertion losses up to 60 dB can be measured with an accuracy of two percent for losses greater than 10 dB. Straighta way video detection techniques are employed. An interesting feature of the millimeter loss scanner is that random noise is averaged to insignificance and the test-set residual loss or baseline is automatically subtracted. The resultant output display is the actual insertion loss of the network under test along with any calibration lines that may be desired. This stored output can be displayed on an oscilloscope and photographed, read out on an X-Y plotter, or transmitted in either digital or analog form to a computer for further processing or analysis.