Subharmonic Injection-locked Oscillator Research Articles

Analysis of high-order sub-harmonically injection-locked oscillators

AbstractHigh-order sub-harmonically injection-locked oscillators have recently been proposed for low phase-noise frequency generation, with carrier-selection capabilities. Though excellent experimental behavior has been demonstrated, the analysis/simulation of these circuits is demanding, due to the high ratio between the oscillation frequency and the frequency of the input source. This work provides an analysis methodology that covers the main aspects of the circuit behavior, including the detection of the locking bands and the prediction of the phase-noise spectral density. Initially, the oscillator in the presence of a multi-harmonic input source is described with a reduced-order envelope-domain formulation, at the oscillation frequency, based on an oscillator-admittance function extracted from harmonic-balance simulations. This allows deriving an expression for the oscillation phase shift with respect to the input source, and the average of this phase shift is shown to evolve continuously in the distinct synchronization bands obtained when varying a tuning voltage. This property can be used to detect the locking bands in circuit-level envelope-domain simulations, which, as shown here, can be done through different Fourier decompositions and sampling rates. The phase noise of the high-order sub-harmonic injection-locked oscillator under an arbitrary periodic input waveform is investigated in detail. The frequency response to the noise sources is described with a semi-analytical formulation, relying on the oscillator-admittance function in injection-locked conditions. The input noise is derived from the timing jitter of the injection source and the phase-noise response is shown to exhibit a low-pass characteristic, which initially follows the up-converted input noise and then the oscillator own noise sources. A method is proposed to identify the key parameters of the derived phase-noise spectrum from envelope-domain simulations. The various analysis methodologies have been applied to a prototype at 2.7 GHz at the sub-harmonic order N = 30 which has been manufactured and measured.

A Low-Noise Digital-to-Frequency Converter Based on Injection-Locked Ring Oscillator and Rotated Phase Selection for Fractional-$N$ Frequency Synthesis

This paper proposes a low-noise digital-to-frequency converter (DFC) for fractional- $N$ frequency synthesis. The DFC first employs a subharmonic injection-locked ring oscillator (ILRO) to generate low phase noise, high-frequency fixed reference from a crystal oscillator (XO). $\Delta \Sigma $ modulator ( $\Delta \Sigma \text{M}$ ) and accumulator are then applied to perform phase randomization and rotation around the multiphase outputs of the ILRO. This modulates the output frequency, while the rotation ensuring the range and linearity of the DFC. Meanwhile, clocking the $\Delta \Sigma \text{M}$ at high frequency greatly suppresses the quantization noise, enabling a wide loop bandwidth for the subsequent phase-locked loop stage. Implemented in UMC CMOS 65-nm technology, the proposed DFC occupies an area of 0.257 mm2, and is capable of generating frequencies from 390 to 640 MHz with resolution finer than 0.3 kHz. The in-band phase noise is lower than −120 dBc/Hz at 100 kHz, tracking well with the noise performance of the XO. The shaped high-frequency quantization noise only appears beyond 20-MHz frequency offset.

An Injection-Locked-Based FMCW Transmitter With Synthetic Bandwidth Technique

An injection-locked-based frequency-modulated continuous-wave (FMCW) transmitter using a synthetic bandwidth technique is presented. A wideband chirp is synthesized by combining the up-converted narrowband chirp with different adjacent carrier frequencies. This is achieved by mixing a narrowband direct digital synthesis chirp with a fast-switching subharmonic injection-locked oscillator (SHILO). The use of SHILO allows fast switching at sub-10 ns and provides better phase noise performance than phase-locked loops due to its much wider loop bandwidth. The key idea is demonstrated at 4 GHz by generating two subband chirps with about 300-MHz bandwidth each, achieving a synthetic bandwidth of 600 MHz. The measured impulse response shows a resolution of 32 cm (Hamming) with a sidelobe level of −25 dBc and very accurate range estimates with accuracy of ±0.5 cm.

A Near-Threshold, 0.16 nJ/b OOK-Transmitter With 0.18 nJ/b Noise-Cancelling Super-Regenerative Receiver for the Medical Implant Communications Service

A 0.16 nJ/b MICS transmitter and 0.18 nJ/b super-regenerative receiver are demonstrated, where each is specifically designed to operate in the near-threshold region. The low-VDD transmitter utilizes a sub-harmonic injection-locked ring oscillator, edge combiner for frequency multiplication, and class-C power amplifier. The low-VDD receiver introduces a replica super-regenerative receiver as a method to reject common-mode noise sources, such as supply/substrate coupling, thereby reducing undesired self-oscillations and improving BER. Designed in a 90-nm CMOS process, the test-chip measurements show a sensitivity of -80 dBm at 500 kb/s and -65 dBm at 1 Mb/s, respectively, at a BER less than 10⁻³, with 340 μW total power.

A dual-gate 2nd/3rd-order subharmonic injection-locked oscillator in GaAs PHEMT

A dual-gate subharmonic injection-locked oscillator (SILO) has been designed and fabricated in 0.5μm GaAs PHEMT process for millimeter-wave communication applications. Specifically, this study proposes a dual-gate circuit topology to achieve a high-frequency oscillator with a large output signal power. The proposed dual-gate transistor also performs a wideband negative resistance characteristic by which the self-oscillation frequency can easily be determined with a proper resonator. The measured self-oscillation frequency of the proposed SILO is approximately 49GHz, and the frequency tuning range is adjustable from 48.7GHz to 49.7GHz with an output power of 8dBm. By injecting a 2nd-order (~24.5GHz) subharmonic signal into the dual-gate SILO, the maximum locking range of 5.6GHz can be approached at an input power of 11dBm without any self-oscillation frequency tuning. With changing the input frequency to be a 3rd-order subharmonic injection (~16.3GHz), an output locking range of 2.9GHz also can be achieved. The measured phase noises of the output signals from 2nd- and 3rd-order subharmonic injections are −101 and −100dBc/Hz, respectively, at 100-kHz offset frequency.

A 5-GHz Subharmonic Injection-Locked Oscillator and Self-Oscillating Mixer

This paper presents a multifunctional circuit realizing the functions of oscillation, mixing, amplification, and frequency multiplication at 5 GHz. A theoretical and experimental description of the circuit is given. The proposed circuit, which combines both the injection-locking and mixing processes, uses only one port where both the RF/intermediate frequency signal and the injection signal (IS) are applied. The IS, which is used to stabilize the oscillation, is at a subharmonic of the oscillation frequency (omegaosc/4) having a power level as low as -50 dBm. Calculations of the phase noise and measurements of the mixing properties are reported which indicate a noise improvement, and a high up-conversion gain. The implementation of the circuit exhibits an up-conversion gain of 14 dB, a phase noise of -110 dBc/Hz at 100-kHz offset, a dB of -15 dBm, a third-order intercept point of -2 dBm, and a power consumption of 35 mW. Calculated and measured results are in good agreement for all cases, emphasizing the relevance of the proposed circuit.

UWB in Millimeter Wave Band With Pulsed ILO

A simple but efficient transmitter for ultra-wide-band impulse radio wavelet generator in millimeter-wave band is presented. It is suitable for RADAR, gigabit wireless personal area network, and localization applications. This front-end involves a subharmonic injection-locked oscillator driven by a pulse generator (PG) with fast transition time (<25 ps). Its frequency oscillation is locked on one of the numerous harmonic components generated by the PG around 30 GHz. This allows to obtain a stable pulse-to-pulse phase condition and a very low phase noise (<-110 dBc/Hz@100 kHz). Two monolithic microwave integrated circuits have been designed using a commercial pseudomorphic high-electron mobility transistor foundry process (ft = 100 GHz). The first one is a PG with position and width modulation capabilities, and the second one is an oscillator with a 30-GHz free-running output frequency. The start of the oscillations is studied, using the external quality factor as main factor.

V-Band GaAs pHEMT Cross-Coupled Sub-Harmonic Oscillator

A V-band cross-coupled sub-harmonic injection-locked oscillator has been designed and fabricated using 0.15-mum GaAs pHMET technology. Based on the known harmonic injecting circuit topology, this oscillator was designed by a differential output approach, a low-Q microstrip-line resonator, and a current mirror, which has a free-running oscillation frequency around 60GHz with a tuning range of 2.5GHz (from 57.8GHz to 60.3GHz). The maximum single-end output power is 3.8dBm with a dc dissipation of 225mW under a -3V supply voltage. Within the input matching network for second (30GHz) and fourth (15GHz) sub-harmonic signals injection, it demonstrates the maximum locking ranges close to 120MHz and 30MHz, respectively

Subharmonic injection‐locking balanced oscillator

AbstractA subharmonic injection‐locked balanced oscillator is presented in this paper. Subharmonic injection locking is preferred to fundamental injection locking, because the central injection point is a virtual short‐circuit at the fundamental frequency for a balanced oscillator. An analytical model is described to predict the locking range whereby power series are used to model the device's nonlinearity. An injection‐locked balanced oscillator is designed at 5.8 GHz and very good agreement is achieved between the predicted and measured locking ranges. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 306–309, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20124