This letter presents a high-speed closed-loop capacitive-input voltage controlled oscillators (VCO)-based continuous-time delta sigma modulator (CTDSM) using a novel fully differential VCO topology whose parasitic pole is inherently located at a very high frequency, regardless of the number of inverters in the ring VCO. The mitigation of the parasitic pole is achieved by splitting the VCO's input transconductor into a set of distributed input transistors. Capacitive input and capacitive DAC result in a very low thermal noise front end, besides ensuring that there is no additional pole caused due to the VCO's input capacitance. A single pair of pseudo-resistors is used for providing dc negative feedback in the CTDSM. The prototype first-order 63-stage VCO-based CTDSM is fabricated in 40-nm CMOS and occupies a core area of 0.02 mm2 while achieving 63.1-dB dynamic range in 480 kHz-20.48 MHz bandwidth at 1 GS/s. This is the first work to mitigate the parasitic pole in a fully differential VCO, without relying on any additional active circuits. To the authors' best knowledge, this is also the first work to demonstrate the capacitive input in a high-speed CTDSM, without using chopping.
This paper presents a wideband integrated dielectric sensor with read-out circuit at 207-257 GHz in SiGe BiCMOS technology. The sensing element is equipped by a resonator that provides a bandpass frequency response which is varied in accordance to the carried permittivity change of the device under test. This variation can be sensed and recorded as the change of output voltage of an integrated 207-257 GHz 2 port vector network analyzer readout circuit. The demonstration of aforementioned readout system is verified by measuring the output of mixers as the reference, reflected and measured channel, and the uncalibrated S parameters of readout with different samples.
This article presents a fully differential power-tuning heterodyne on-chip sensing readout system at 240 GHz. The chip enables the measurement of not only the transmission parameter but also the reflection parameter to sense the permittivity of different materials by using four heterodyne mixer-based receiving channels connected to a dielectric sensing element. To facilitate the operation and characterization, three frequency multiplier chains are included to generate the required two identical radio frequency (RF) and one local oscillator (LO) subterahertz signals. RF frequency multiplier chain is configured to enable a tunable power level of the RF signal by using a variable attenuator. A chip prototype using 130-nm silicon–germanium (SiGe) BiCMOS is implemented with a size of 11 mm 2 and dc power consumption of 2.7 W. The measured 10-dB bandwidth of 20.8% is achieved in a frequency range from 207 to 257 GHz with 14-dB measured power-tuning range. The transmission and reflection parameters’ measurements for copper and gummi show a differentiated value in terms of magnitude and phase, which demonstrates the sensing function of the proposed readout system.
