Abstract
Wideband and low-noise tunable oscillators at microwave frequencies are crucial within microwave frequency synthesizers and key to high-end measurement systems based on electromagnetic sensing in the microwave range as well as in the terahertz (THz) and sub-THz range. This paper presents a novel, wideband, and low-noise differential yttrium iron garnet (YIG) tuned oscillator. It is based on a SiGe monolithic microwave integrated circuit and a transmission-type YIG resonator. The integrated circuit contains a fully differential amplifier as a part of the oscillator core. The resonator was realized by two orthogonal, crossed pad-to-pad bonds and an YIG sphere, which is positioned between those bonds and the integrated circuit. To design and optimize the oscillator, an equivalent circuit modeling the resonator was developed. Concerning the tuning range and the phase noise, the results of the circuit simulations are in good agreement with the measurements. Two oscillators with different lengths of the inductive load transmission line were realized. First, the oscillator with a short transmission line offers very high-oscillation frequencies with a tuning range from 32.0 to 48.2 GHz. It exhibits an excellent phase noise of less than -119dBc/Hz at an offset frequency of 100kHz for oscillation frequencies up to 42GHz. Second, the oscillator with a longer transmission line length offers a tuning range from 19.1 to 41.4 GHz. This configuration exhibits an excellent phase noise of less than -120dBc/Hz at an offset frequency of 100 kHz for oscillation frequencies up to 38GHz.
Highlights
M ICROWAVE frequency synthesizers are key to high-end measurement systems based on electromagnetic (EM)
Yttrium iron garnet (YIG) tunable oscillators (YTOs) utilize an yttrium iron garnet (YIG) sphere as the resonator, whose resonance frequency is tuned by a magnetic field [21]
The use of bipolar transistors is crucial for low phase noise of the oscillator, as they exhibit a low flicker noise corner compared to MOS transistors
Summary
M ICROWAVE frequency synthesizers are key to high-end measurement systems based on electromagnetic (EM). Tunable opto-electronic oscillators (TOEO) use sophisticated optical resonators to tune the output frequency in the microwave range They offer a high bandwidth of up to more than one octave and low phase noise at the same time [19], [20]. Yttrium iron garnet (YIG) tunable oscillators (YTOs) utilize an YIG sphere as the resonator, whose resonance frequency is tuned by a magnetic field [21] They offer a high bandwidth of up to more than one octave and low phase noise at the same time, like TOEOs. unlike TOEOs, YTOs do not exhibit critical spurs at high offset frequencies and exhibit a crucial lower noise floor [19], [20], [22], [23].
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