In this paper, we propose a method to broaden a tuning range of a CMOS LC-tank oscillator without sacrificing its area. The extra tuning range is achieved by forcing a strongly coupled transformer-based tank into a common-mode resonance at a much higher frequency than in its main differential-mode oscillation. The oscillator employs separate active circuits to excite each mode but it shares the same tank, which largely dominates the core area but is on par with similar single-core designs. The tank is forced in common-mode oscillation by two injection locked Colpitts oscillators at the transformer's primary winding, while a two-port structure provides differential-mode oscillation. An analysis is also presented to compare the phase noise performance of the dual-core oscillator in common-mode and differential-mode excitations. A prototype implemented in digital 40-nm CMOS verifies the dual-mode oscillation and occupies only 0.12 mm² and measures 56% tuning range.

Quantum computing holds the promise to achieve unprecedented computation power and to solve problems today intractable. State-of-the-art quantum processors consist of arrays of quantum bits (qubits) operating at a very low base temperature, typically a few tens of mK, as shown in Fig. 15.5.1 The qubit states degrade naturally after a certain time, upon loss of quantum coherence. For proper operation, an error-correcting loop must be implemented by a classical controller, which, in addition of handling execution of a quantum algorithm, reads the qubit state and performs the required corrections. However, while few qubits (∼10) in today's quantum processors can be easily connected to a room-temperature controller, it appears extremely challenging, if not impossible, to manage the thousands of qubits required in practical quantum algorithms [1].

We present an ultra-low-power Bluetooth low-energy (BLE) transceiver (TRX) for the Internet of Things (IoT) optimized for digital 28-nm CMOS. A transmitter (TX) employs an all-digital phase-locked loop (ADPLL) with a switched current-source digitally controlled oscillator (DCO) featuring low frequency pushing, and class-E/F₂ digital power amplifier (PA), featuring high efficiency. Low 1/ f DCO noise allows the ADPLL to shut down after acquiring lock. The receiver operates in discrete time at high sampling rate (10 Gsamples/s) with intermediate frequency placed beyond 1/ f noise corner of MOS devices. New multistage multirate charge-sharing bandpass filters are adapted to achieve high out-of-band linearity, low noise, and low power consumption. An integrated on-chip matching network serves to both PA and low-noise transconductance amplifier, thus allowing a 1-pin direct antenna connection with no external band-selection filters. The TRX consumes 2.75 mW on the RX side and 3.7 mW on the TX side when delivering 0 dBm in BLE.

This paper proposes a digital-to-time converter (DTC)-assisted fractional-N wide-bandwidth all-digital phase-locked loop (ADPLL) with a fine-resolution time-to-digital converter (TDC). The TDC employs a two-channel time-interleaved time-domain register with an implicit adder/subtractor realizing an error-feedback topology. Such an error-feedback unit of a first-order Δ Σ -TDC can be cascaded as a multi-stage noise shaping configuration to achieve higher-order noise-shaping and, thereby, low in-band phase noise (PN) of the ADPLL. A digitally controlled oscillator with a transformer and a pair of cross-coupled NMOS amplifiers exploits magnetic and capacitive coupling to achieve nearly an octave frequency coverage, i.e., 1.73-3.38 GHz (after a ÷2 division). Fabricated in 40-nm CMOS, the ADPLL achieves better than -110-dBc/Hz in-band PN and occupies an active area of 0.5 mm². With a 50-MHz reference clock, a 2-GHz output RF clock, and a loop bandwidth of 800 kHz, this prototype achieves 420-fsrms jitter, integrated from 1-kHz to 30-MHz offset, while drawing 10.7 mW.

In this paper, we propose a method to reduce a flicker (1/f) noise upconversion in voltage-biased RF oscillators. Excited by a harmonically rich tank current, a typical oscillation voltage waveform is observed to have asymmetric rise and fall times due to even-order current harmonics flowing into the capacitive part, as it presents the lowest impedance path. The asymmetric oscillation waveform results in an effective impulse sensitivity function of a nonzero dc value, which facilitates the 1/f noise upconversion into the oscillator's 1/f³ phase noise. We demonstrate that if the ω₀ tank exhibits an auxiliary resonance at 2 ω₀, thereby forcing this current harmonic to flow into the equivalent resistance of the 2 ω₀ resonance, then the oscillation waveform would be symmetric and the flicker noise upconversion would be largely suppressed. The auxiliary resonance is realized at no extra silicon area in both inductor-and transformer-based tanks by exploiting different behaviors of inductors and transformers in differential-and common-mode excitations. These tanks are ultimately employed in designing modified class-D and class-F oscillators in 40 nm CMOS technology. They exhibit an average flicker noise corner of less than 100 kHz.