A Ka-band push-push voltage-controlled oscillator (VCO) using a parasitic capacitance cancelling technique is presented. To enhance the oscillation frequency (f osc) and the tuning range (TR), the parasitic capacitance of the VCO is cancelled with negative capacitance (NC). To realise NC, a negative impedance circuit (NIC) is analysed and designed. Because of self-resonance frequency, NC is realised using an open-circuit stable NIC. For further enhancement of the f osc , the VCO is developed in a push-push operation. The proposed VCO is fabricated in a commercial 0.15 μm GaAs pHEMT process. It shows 12.4% of the TR at 31.6 GHz with 11 dBm output power. With the NIC, the centre frequency of the VCO increases from 20.1 to 31.6 GHz and the TR increases from 5.7 to 12.4% compared with a VCO without the NIC.
Selective suppression of high order axial modes of the gyrotron backward-wave oscillator Phys. Plasmas 14, 093301 (2007) In this paper, we test the performance of a quasi-optical, internal-gyrotron mode converter. When cold testing mode converters, a rotating higher-order mode is commonly used. However, this requires a nontrivial design and precise alignment. We thus propose a new technique for testing gyrotron mode converters by using a simple, non-rotating, higher-order mode generator. We demonstrate the feasibility of this technique for a W-band gyrotron quasi-optical mode converter by examining the excitation of a TE 6,2 mode from a non-rotating mode generator. Our results demonstrate that this new cold-test scheme is an easy and efficient method for verifying the performance of quasi-optical mode converters.
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