We present a sensitivity analysis on TRL calibrated -parameter measurements of membrane circuits in the WR-03 waveguide band (220-325 GHz). The impact of waveguide and membrane circuit misalignment, as well as waveguide dimension mismatch is investigated. The analysis is performed for the thru-reflect-line (TRL) calibration applied to E-plane split waveguide blocks carrying membrane circuits. The analysis shows a large influence of the waveguide width tolerance on transmission and reflection phase after the TRL calibration. For a 20 mm long rectangular waveguide with a 5 m width tolerance a phase uncertainty as large as 45 for reflection and 30 for transmission measurements is observed.
This paper reports on an experimental analysis of phase noise in a tuned-input/tuned-output oscillator based on a bare-die GaN HEMT device. To investigate phase noise dependency on resonator coupling factor (β), the circuit is designed with flexibility to modify the resonant tank, in terms of unloaded quality factor (Q 0 ) and impedance level. The reflection coefficient (Γ amp ) from the reflection amplifier can also be varied.
With exception for very high values of Γ amp , the circuit is robust to variations in β. It is more important to choose a bias pointwhere the flicker noise is low and the power reasonably high. A minimum phase noise of -150dBc/Hz @ 1MHz off-set from a 1GHz oscillation frequency and a power normalized figure of merit (FOM) of 186 are reached.An interesting analytical result is also presented; power normalized figure of merit, commonly used for benchmark of oscillators is bound by Q 0 and can be related to the theoretical noise floor limit.
This paper presents a MMIC GaN HEMT Voltage-Controlled-Oscillator (VCO). The VCO is tunable between 6.45-7.55 GHz with good tuning linearity, average output power about 1 dBm, and a good phase noise with little variation over the tuning range. For a bias of V d /I d = 6 V/33 mA, the measured phase noise is -98 dBc/Hz @ 100 kHz and -132 dBc/Hz @ 1 MHz offset frequencies, respectively. To the author's best knowledge, this is the lowest phase noise reported for a VCO in GaN HEMT technology with comparable oscillation frequency and tuning range. The 1 MHz offset phase noise is also comparable to state-of-the-art GaAs-InGaP HBT VCOs with similar tuning range.Index Terms -Voltage-Controlled-Oscillator, MMIC, GaN, HEMT, phase noise.
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