Ka-band Design Research Articles

Investigation of angular log-periodic folded groove waveguide slow-wave structure for low voltage Ka-band TWT

In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S21 varying from −2.7 dB to −4.8 dB and S11 better than −13.6 dB over the frequency range of 30–38 GHz. Simulations of beam–wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.

Design of $X$-Band and $Ka$-Band Colpitts Oscillators Using a Parasitic Cancellation Technique

An <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band and two <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band monolithic microwave integrated circuit (MMIC) common drain Colpitts oscillators using a parasitic cancellation technique are designed and fabricated in a 0.2-μm GaAs pHEMT technology with a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of 60 GHz. The parasitic cancellation technique significantly improves the negative resistance and increases the maximum operating frequency, which is suitable for microwave and millimeter-wave applications. An in-depth theoretical analysis of the Miller effect and insights in the behavior of the input impedance with the parasitic cancellation are provided. The effect of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor of the inductor used in the cancellation, and the impact of the parasitic cancellation technique on phase noise and frequency tuning range are analyzed and discussed in detail. The <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band design has a measured phase noise of -117.5 dBc/Hz at 1 MHz offset with an output power of -9.3 dBm . The first <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band design has a measured phase noise of -94 dBc/Hz at 1 MHz offset with an output power of +0.2 dBm. The second <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band design providing more flexibility has a measured phase noise of -98.5 dBc/Hz at 1 MHz offset with an output power of + 0.3 dBm. The two <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band designs achieve very high <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OSC</sub> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ratios and also demonstrate performance comparable to the best previously published oscillators in a similar frequency range.

High-power high-efficiency SiGe Ku- and Ka-band balanced frequency doublers

High-efficiency monolithic SiGe balanced frequency doublers have been developed for Ku- and Ka-band applications. A novel miniature second harmonic reflector is presented, and the impact of the parasitic inductor from emitter to ground is also explored to optimize the conversion efficiency of the doubler. The Ku-band design presents an output power of 5-6 dBm from 15.4-18 GHz for an input power of 1.5 dBm. DC power consumption is 28 mW and the corresponding power-added efficiency (PAE) is 9.2%. The Ka-band design demonstrates an output power of 10.5 dBm at 36 GHz for an input power of 6 dBm while consuming 114 mW of dc power, which results in a PAE of 6.4%. It also shows high spectral purity operation with the fundamental suppression of 35 dB. To our knowledge, these are the best results for active doublers using any technology.