Voltage-controlled oscillator

About: Voltage-controlled oscillator is a research topic. Over the lifetime, 23896 publications have been published within this topic receiving 231875 citations. The topic is also known as: VCO.

Phase locked loop having plural selectable voltage controlled oscillators

Abstract: The invention discloses a PLL formed by a phase detector, a filter, three VCO's (VCO1, VCO2, and VCO3), a multiplexer, and a frequency divider. The VCO1, VCO2, and VCO3 have different mean frequencies, each oscillating at a frequency controlled according to the voltage value of a phase control signal from the filter. The multiplexer selects one of the VCO's which operate in parallel. If a pulse of a digital phase difference signal UP indicating that an internal signal is delayed in phase with respect to a reference signal is output twice in succession, or if a pulse of a digital phase difference signal DOWN indicating that an internal signal is advanced in phase with respect to a reference signal is output twice in succession, a counter makes the multiplexer change its current VCO selection via a shift register. Accordingly, high-speed PLL pulling is achievable even if a PLL frequency variable-range is expanded.

Analysis and Design of Transformer-Based Dual-Band VCO for Software-Defined Radios

Abstract: This work presents complete analysis of both one- port and two-port dual-band oscillators using transformer-based fourth-order LC tanks, from which critical parameters including oscillation frequency, start-up condition, tank Q, phase noise-are thoroughly derived and compared. It is shown that one-port oscillators consume less power than two-port counterparts but may suffer from stability problem which can be solved by a notch-peak cancellation technique. On the other hand, compared to one-port oscillators, two-port oscillators need to consume more power to obtain the same output swing, but their phase noise can be improved more linearly with increasing bias current, and thus they can achieve lower phase noise with a sufficiently large bias current. Based on the results, a dual-band quadrature voltage- controlled oscillator (Q-VCO) is systematically designed and implemented in a 0.13- m CMOS process for software-defined -radio (SDR) applications, in which the two-port topology is used in the low band for low phase noise and the one-port topology is employed in the high band for low power consumption. The prototype achieves a dual-band operation with in-phase and quadrature-phase (IQ) output signals from 2.7 GHz to 4.3 GHz and from 8.4 GHz to 12.4 GHz. At 3.6 GHz and 10.4 GHz, phase noise at 3 MHz offset of dBc/Hz and dBc/Hz and sideband-rejection ratios (SBR) of 37 dB and 41 dB are measured, respectively.

Voltage controlled oscillator operating with digital controlled loads in a phase lock loop

Abstract: A phase lock loop (16) operates independent of temperature and process variation by digitally loading a VCO (22) until reaching the desired operating frequency. The VCO reaches a high output frequency even under worst case processing by controlling multiple current mirrors (162-166, 174-180, 182-188) to increase inverter switching current without slowing the response of the VCO to changes in loop node voltage. An Initialize-to-VDD circuit (32) sets the loop node voltage to V DD so that the load control circuit need only increase loading to slow down the VCO to the desired operating frequency. A frequency range detector (34) monitors the output frequency of the VCO and passes control signals to a load control circuit to (36) activate digital loads (38) and slow down the VCO to the desired operating frequency.

PLL Fast frequency synthesizer with memories for coarse tuning and loop gain correction

Abstract: A phase-locked loop frequency synthesizer apparatus for providing an output signal whose frequency jumps from one value to another, at regular intervals of time. Coarse tuning circuitry couples a prescribed signal to the apparatus' voltage-controlled oscillator (VCO), to drive the VCO immediately to the correct frequency each time a new frequency is selected, thereby substantially reducing the apparatus' settling time. In addition, adaptive coarse tuning circuitry continuously updates the values of stored coarse tuning information for each possible frequency, to correct for any drifts in the VCO's voltage/frequency characteristic. A VCO gain normalizer circuit amplifies the error signal coupled to the VCO by an amount that varies with the selected frequency, so as to correct for any non-uniformities in the apparatus' various elements, particularly the VCO, and to thereby provide a uniform loop gain.

A low-phase-noise low-phase-error 1.8 GHz quadrature CMOS VCO

Abstract: A 1.8 GHz quadrature VCO in standard 0.35 /spl mu/m CMOS with three metal layers shows -140 dBc/Hz or less phase noise across an 18% tuning range, while drawing 25 mA from a 2 V power supply. The quadrature phase error between the VCO outputs is at most 0.25/spl deg/.