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A novel low-voltage quadrature inductor–capacitor (LC) oscillator is presented. The proposed oscillator is immune to the phase ambiguity problem encountered in quadrature oscillators. Simulations show that the proposed oscillator can obtain a phase noise of −150 dBc/Hz at 10 MHz offset for a 5 GHz centre frequency and a figure-of-merit (FoM) of 195 dBc/Hz. The proposed oscillator has a superior start-up performance compared to other low-voltage quadrature LC oscillator architectures.

A new low-phase-noise colpitts LC quadrature voltage controlled oscillator (QVCO) is presented. The proposed QVCO is realised by coupling two differential current-switching Colpitts oscillators in an `in-phase-anti-phase' manner. The coupling technique between the two Colpitts LC-voltage controlled oscillators (VCOs) has significantly improved the phase noise of the proposed circuit without using any extra elements. The oscillation frequency of the proposed LC-QVCO is 4 GHz. The Colpitts QVCO exhibits a phase noise of -131.5 and -141.3 dBc/Hz at 1 and 3 MHz offset, respectively. By generalising the coupling scheme to more than two differential Colpitts VCOs in a loop, multiphase signals can be generated.

A novel low-power injection-locked frequency divider (ILFD) is proposed, in which a complementary G m -boosted Colpitts oscillator core is employed to improve negative transconductance ( G m ) and the current-reuse technique using a single transformer is applied to reduce the power consumption. The proposed ILFD exhibits a self-resonant frequency of 4.93 GHz with a maximum locking range of 870 MHz at 0 dBm of input power. The phase noises of the input and output signals are -128.54 and -134.53 dBc/Hz, respectively. The ILFD consumes 1.37 and 2.5 mW at 1.15 and 1.3 V, respectively. The chip area is 715.5 × 468 μm 2 in a 0.13 μm CMOS process. To the authors' knowledge, this is the first demonstration of the current-reuse ILFD.

An approach to adjusting and optimising the phase-noise performance of CMOS LC oscillators is presented. The technique is based on controlling the bulk-source voltage of the cross-coupled transistors in the oscillator core. It is shown that the impedance in the path of the current through the oscillator core to ground at the second harmonic of oscillation can be maximised through changing the value of the parasitic capacitances. The technique is validated by measured results from a proof-of-concept LC oscillator fabricated in a 90 nm CMOS process.

The first reactance-less oscillator is introduced. By using a memristor, the oscillator can be fully implemented on-chip without the need for any capacitors or inductors, which results in an area-efficient fully integrated solution. The concept of operation of the proposed oscillator is explained and detailed mathematical analysis is introduced. Closed-form expressions for the oscillation frequency and oscillation conditions are derived. Finally, the derived equations are verified with circuit simulations showing excellent agreement.

A compact wide tuning range design of a CMOS voltage-controlled oscillator (VCO) at W-band frequencies is presented. The design employs a differential Colpitts configuration, using a bufferless transformer output and nested inductors. The gate bias is used for frequency tuning that achieves a wide range of 93.7–100.7 GHz. A peak output power of 4.7 dBm with power efficiency of 5.5% is achieved at 98.8 GHz and the phase noise is around −80 dBc/Hz at 1 MHz offset across the tuning range. The VCO uses a silicon area of 0.15 mm2 including pads and, depending on bias, consumes between 6–63 mW of DC power.

A report is presented on all the possible canonical second-order single-transistor three-impedance oscillators that can be derived from the general class-A or class-B two-port network topologies. Two of the ten reported cases are already known as the class-A and class-B Colpitts oscillators. A selected case, which has the appealing feature of extending the oscillation frequency beyond the resonance frequency, is chosen for experimental validation.

A low-voltage relaxation oscillator for passive wireless microsystems is proposed. The oscillator employs a current pulse generator to generate effective hysteresis for oscillation without using a Schmitt trigger, avoiding the drawback of the high sensitivity of the frequency of Schmitt trigger relaxation oscillators to supply voltage fluctuation. The proposed oscillator has been implemented in TSMC-0.18 mum 1.8 V six-metal one-poly CMOS technology. The performance of the oscillator is validated using measurement results.

A class E Colpitts oscillator for low power wireless applications, operating around 900 MHz, is reported for the first time. A microstrip design of the oscillator demonstrates a maximum drain efficiency of 46.5 , with an output power of 8.5 dBm, at a supply voltage of 1.2 V. Simulation predicts that a miniaturised design of the oscillator with lumped element components would achieve a drain efficiency of over 60%.

A capacitive sensor for detecting the heartbeat rate of a human without direct contact with the skin is investigated. Precordial movement changes the capacitance between patch electrodes and modulates the frequency of a Colpitts oscillator. Heartbeat and respiration information can be obtained by demodulating the oscillating signal. Heartbeat signal obtained by bandpass filtering the harmonics of heartbeat frequency is separated from the demodulated signal.

A simple approach to the realisation of a differential Colpitts oscillator is to connect the grounded capacitor in the feedback network of two single-ended Colpitts oscillators together in series. As the output signals are expected to be differential, it is proved in this Letter that, this is not always the case. In certain circumstances, this topology exhibits a common-mode output signal, or even worse, a combination between differential-mode and common-mode waveforms. Design criteria for avoiding these undesirable oscillating behaviours are derived by considering the start-up characteristic of the oscillator.

The design of a temperature-compensated CMOS ring oscillator is introduced. The concept is to make use of a linear, positively or negatively temperature-sloped supply voltage to power-up the ring oscillator. Experimental results show that the oscillation frequency remains fairly constant using the proposed scheme.

A novel version of the Colpitts oscillator is presented generating chaotic oscillations at gigahertz frequencies. In contrast to the standard oscillator the inductor is moved from the collector circuit of the transistor to the base circuit. PSpice simulations demonstrate chaos at the fundamental frequencies of 0.5, 1 and 2 GHz employing transistors with a threshold frequency of 9 GHz.

Experimental results demonstrating chaotic performance of the Colpitts oscillator in the very high frequency (30–300 MHz) and the ultra-high frequency (300–1000 MHz) ranges are reported. Period-doubling route to chaos is revealed, confirming the dynamical nature of the chaotic oscillations. Broadband continuous power spectra are presented.

CMOS VHF/RF CCO based on active inductors A novel CMOS current controlled oscillator (CCO) is proposed. Based on the current-reused active inductors, a differential oscillator has been designed and fabricated. Measurement results show that it has very wide tuning-range and reasonable phase-noise performance.

The classical Wien-bridge sinusoidal oscillator is studied, when both of the capacitors of the oscillator acquire a fractional order. Accordingly, the Wien oscillator is described by a set of fractional-order nonlinear differential equations. It is shown that sinusoidal oscillations are preserved but the phase-shift between the waveforms of the two state variables and the frequency of oscillation both depend on the fractional-order, leading to a significant advantage over the integer-type Wien oscillator. Findings are validated via numerical simulations.

The problem of undesirable low-frequency oscillation which may occur in oscillators with composite amplifiers is discussed. The Letter shows how the Wien-bridge oscillator proposed by Carlosena et al. should be modified in order to avoid such oscillation and ensure stable operation of the oscillator and good properties of the sinusoidal waveform generated.

A new variable frequency sinusoidal oscillator configuration is proposed. Only two current feedback operational amplifiers (CFOAs), two grounded capacitors and three resistors are used. The frequency and condition of oscillation can be independently adjusted by means of single grounded resistors. Also, very high frequency operation is demonstrated and an example application of an oscillator which does not require an external capacitor presented.

Two microwave oscillators at a free-running frequency of ∼800 MHz are designed. Both were designed to have the same feedback factors; the difference lies in the output loading circuit. By using the inverted common collector (ICC) configuration, a stable negative resistance is generated. This negative resistance is then used to compensate for the loss in the feedback path. Hence, a zero resistance loaded oscillator is implemented. A comparative study with experimental support confirmed that the zero loaded oscillator has a 6 dB and 18 dBc improvement in the phase noise and second harmonic rejection, respectively.

The output from a data selector driven by a polyphase binary oscillator and addressed by a digital counter enables the sum or difference of two frequencies to be selected.

A sinusoidal oscillator whose frequency is linearly related to an input control current is described. A variable inductor is realised using a fixed inductor and a variable-gain current-controlled current source. The variable inductor is then used in an LC oscillator circuit. Linear frequency variation with control current is obtained in a temperature-independent manner by using a function generator. Frequency variation over a range of 1:3 is obtainable, with a linearity of better than 1%.

An earlier single-resistance-controlled oscillator (s.r.c.o.) with grounded capacitors employs three operational amplifiers (o.a.); the new s.r.c.o. proposed here employs only two o.a.s and a reduced number of resistors. The proposed s.r.c.o. may be adopted for voltage-controlled-oscillator realisation. In addition, the new circuit may also be employed for the generation of very-low-frequency oscillations. The circuit appears to be suitable for integrated-circuit implementation.

The design and performance of a rugged duroid-microstrip IMPATT-diode oscillator is described. The oscillator's frequency was set by a simple, easily replaceable metal resonant cap, with fine tuning of about 30 MHz/mA being achieved by means of the diode current.

Circuits are described for simulating inductors and capacitors by digital (hardware) techniques. Filter and oscillator applications are discussed and test results are given.

A simple method to synthesise dual-feedback ideal op-amp oscillator circuits is presented. Based on two theorems, this method permits us to synthesise three different oscillator circuits from the knowledge of one circuit. As an example, starting from the well known Wien-bridge oscillator, three other forms of Wien-bridge oscillators are derived.

The technique of oscillator stabilisation by a delay line, previously used at h.f., is extended to microwave frequencies. Performance details are given at X-band, showing a stabilisation ratio of about 23 and an improvement in f.m. oscillator stability. The system remains in lock throughout X-band.