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In this brief, a harmonic-controlled substrate-integrated defected ground structure (SIDGS) resonator with tuning capacitor is proposed for the design of tunable filter. Such resonator exhibits a harmonic-controlled characteristic. The fundamental resonant frequency can be properly tuned, while the spurious resonance is controlled at much higher frequency to achieve a wide stopband. To verify the principle, a tunable bandpass filter (BPF) is designed and fabricated based on the resonator. The center frequency can be tuned from 1.75 to 2.7 GHz. Meanwhile, the stopband can extend up to 9.5 GHz with a rejection level of 20 dB for all tuning cases. The BPF also exhibits low insertion loss (i.e., 1.1–1.9 dB) and compact size (i.e., 0.07 ${\lambda _{g}}\,\,{\times }\,\,0.08\,\,{\lambda _{g}}$ , where ${\lambda _{g}}$ is the microstrip guided wavelength at the 1.75 GHz). [ABSTRACT FROM AUTHOR]

In this article, a distributed-swing-boosting and harmonic-impedance-expanding multi-core oscillator is proposed to achieve low phase noise and high figure-of-merit (FoM), simultaneously. First, a distributed-coupling multi-core topology is introduced to reduce the chip area with no mode ambiguity. Then, the distributed-swing-boosting and harmonic-impedance-expanding structure is developed to boost the gate swing and square-like waveform of $V_{\text {DS}}$. The common-mode (CM) resonances around the second harmonic and the differential-mode (DM) resonances around the third harmonic are utilized to suppress the flicker noise up-conversion and achieve harmonic shaping. Meanwhile, the dual-resonance response expands the high-impedance frequency ranges around the harmonics, and thus, the effect of harmonic shaping can be obtained over a wide frequency range. Fabricated in a 40-nm CMOS process, the oscillator measured exhibits low phase noise and high FoM simultaneously with a compact chip size. The minimum phase noise is −138.9 dBc/Hz at the 1-MHz offset, corresponding to an FoM of 195.1 dBc/Hz. The 1/ $f^{3}$ phase noise corner is 100–130 kHz over the 26.6% tuning range. [ABSTRACT FROM AUTHOR]

In this letter, a novel substrate integrated defected ground structure (SIDGS) resonant cell is proposed. Such SIDGS resonant cells can not only introduce an ultrawide stopband for spurious suppression but also achieve low radiation loss in a wideband, which can be easily implemented in passive circuits with high performance. To verify this mechanism, a filtering power divider (FPD) using the folded stepped-impedance scheme is developed. Here, two coupled SIDGS resonant cells are cascaded at the arms of the power divider to achieve a filtering response with ultrawideband harmonic suppression. The fabricated FPD is operated at 2.87 GHz (i.e., the passband center frequency $f_{0}$) with a 3-dB fractional bandwidth (FBW) of 23%, which exhibits the 28-dB attenuation upper stopband with a low radiation loss even up to 25 GHz (i.e., 8.71 $f_{0}$). [ABSTRACT FROM AUTHOR]

In this article, two types of substrate-integrated defected ground structure (SIDGS) resonant cells with wide upper stopband and low radiation loss are presented for filter implementation. Such SIDGS resonant cells are composed of two dissimilar DGSs surrounded by the bottom ground and metal-vias, which cannot only introduce wide stopband with low radiation loss but also be flexible for integration. Based on the aforementioned SIDGS resonant cells, single- and dual-band bandpass filters (BPFs) are designed and fabricated. The single-band BPF centered at 2.40 GHz exhibits an ultrawide upper stopband up to 19.7 GHz with a rejection level of 31 dB, whereas the measured stopband total loss (i.e., including radiation, metal, and substrate loss) remains about 30% up to 19.3 GHz. The dual-band BPF operated at 2.10 and 3.78 GHz exhibits an ultrawide upper stopband up to 17.8 GHz with a rejection level of 23 dB, whereas the measured stopband total loss is less than 16% up to 11.4 GHz. [ABSTRACT FROM AUTHOR]

A wideband hybrid mode-switching push–push oscillator with low phase noise is presented in this paper. To achieve the wide tuning range, the inductive and capacitive hybrid mode-switching technique is proposed for the first time. It introduces more freedom of design parameters (i.e., inductance and capacitance) in the resonant tank. Under certain tuning range requirement, the hybrid mode-switching oscillator achieves higher input impedance of the resonator compared to the conventional mode-switching oscillators. Meanwhile, a transformer-coupled inductor ring with symmetrical layout configuration is proposed to realize the switch-less hybrid mode switching, which further improves the circuit performance at sub-THz. Therefore, a good phase noise performance can be obtained within a wide tuning range, which leads to a relaxed tradeoff between the phase noise and tuning range. To verify the aforementioned mechanism operating at sub-THz band, a hybrid mode-switching oscillator based on the dual-mode push–push topology is proposed and fabricated in a conventional 28-nm CMOS technology. The measured results show a 21.7% tuning range with the center frequency of 169.6 GHz and a state-of-the-art FoMT of −180.6 dBc/Hz. The core circuit only occupies 0.039 mm2, while drawing 95 mW with a 0.9-V supply. [ABSTRACT FROM AUTHOR]

The needs of multiband communication continue to grow, leading to an increase in the number of RF bands. Therefore, to meet system requirements for efficient operation in a compact size, as well as develop multifunction applications, reconfigurable and miniaturized filters using a single signal path are essential. [ABSTRACT FROM PUBLISHER]