Delay Line Oscillator Research Articles

Characterization of Nano-liter Sessile Droplets By Using An Active Microwave Resonance Probe.

In this work we present a microwave intracavity sensor for the characterization of aqueous solutions of nano-liter sessile droplets, deposited on the microstrip line electrode. The sensor operates at frequency and is based on tunable magnonic delay line oscillator. The samples were characterized by using their evaporation dynamics, by measuring their dielectric constants. The experiments have shown that the sensor is capable of detecting the salinity (S) of water with the required precision and resolution. The advantage of the sensor is the possibility of measuring the parameters such as S, Total Dissolved and Total Suspended Solids, simultaneously.

On the stability & phase locking to a system reference of an optoelectronic oscillator with large delay

Delay line oscillators based on photonic components, offer the potential for realization of phase noise levels up to 3 orders of magnitude lower than achievable by conventional microwave sources. Fibreoptic-based delay lines can realize the large delay required for low phase noise systems whilst simultaneously achieving insertion loss levels that can be compensated with available microwave and photonic amplification technologies. Multimode operation is an artefact of the delay line oscillator and introduces modulational instability into phase-locked control loops. An optoelectronic oscillator (OEO) with large delay under proportional integral control by a phase-locked loop (PLL) is modelled, providing the first report of the location of all the infinity of poles of the PLL-OEO system function. The first experimental observation of giant phase modulated oscillation of a free OEO and spontaneous giant phase modulated oscillation of a PLL-OEO are also reported and explained respectively as a source and manifestation of modulational instability. Nevertheless, the analysis and experimental observations, including a prototype 10 GHz PLL-OEO phase noise spectral density achieving - 80dBc/Hz {text{at}} 10 Hz and - 145dBc/Hz {text{at}} 10 kHz, demonstrate that stable phase lock operation and optimum phase noise performance is achievable provided full account of the multimode nature of the OEO is taken in the phase lock analysis.

Enhanced Frequency Stability of SAW Yarn Tension Sensor by Using the Dual Differential Channel Surface Acoustic Wave Oscillator.

This paper presents a 60 MHz surface acoustic wave (SAW) yarn tension sensor incorporating a novel SAW oscillator with high-frequency stability. A SAW delay line was fabricated on ST-X quartz substrate using the unbalanced-split electrode and bi-directional engraving slots. The dual differential channel delay linear acoustic surface wave oscillator is designed and implemented to test yarn tension, which can effectively remove the interference of temperature, humidity, and other peripheral factors through differential design. The yarn tension sensor using the surface acoustic wave has high-precision characteristics, and the SAW delay line oscillator is designed to ensure the test system’s stable operation. The effect of time and tension on oscillator frequency stability is studied in detail, and the single oscillator and the dual differential channel system were tested, respectively. After using the dual differential channel system, the short-term frequency stability from is reduced from 1.0163 ppm to 0.17726 ppm, the frequency accuracy of the tension sensor is improved from 134 Hz to 27 Hz, and the max frequency jump steady is reduced from 2.2395 ppm to 0.45123 ppm.

Injection Locking of Optoelectronic Oscillators With Large Delay

The optoelectronic oscillator is a delay line oscillator that leverages optical fibre technology to realize the large delay required for low phase noise systems. Spurious sidemodes are an artefact of the delay line oscillator, yet treatments of injection locking of optoelectronic oscillators have relied on the application of classical injection locking theory valid only for single mode oscillators. The large delay contributed by the optical fibre delay line is accounted for by the classical theory only in part through the quality factor Q that captures the round-trip group delay in a neighborhood of the oscillation frequency. This paper presents a new formulation of time delay oscillators subject to injection that describes all the essential features of their dynamics and phase noise. The common assumptions of a single mode oscillator and weak injection are removed. This is important to correctly predict the lock-in range, the suppression of sidemodes and the phase noise spectrum. The findings of the analysis are validated by experimental measurements provided by an optoelectronic oscillator under injection by an external source.

Low Phase Noise RF Oscillators Based on Thin-Film Lithium Niobate Acoustic Delay Lines

An RF oscillator has been demonstrated using a wideband SH0 mode lithium niobate acoustic delay line (ADL). The design space of the ADL-based oscillators is theoretically investigated using the classical linear time-invariant (LTI) phase noise model. The analysis reveals that the key to low phase noise is low insertion loss (IL), large delay ( ${\tau }_{\mathbf {G}}$ ), and high carrier frequency ( $\mathbf {f}_{\mathbf {o}}$ ). Two SH0 ADL oscillators based on a single SH0 ADL ( $\mathbf {f}_{\mathbf {o}}= 157$ MHz, IL = 3.2 dB, ${\tau }_{\mathbf {G}} = 270$ ns) but with different loop amplifiers have been measured, showing low phase noise of −114 dBc/Hz and −127 dBc/Hz at 10-kHz offset with a carrier power level of −8 dBm and 0.5 dBm, respectively. These oscillators not only have surpassed other Lamb wave delay oscillators but also compete favorably with surface acoustic wave (SAW) delay line oscillators in performance. [2019-0223]

Time-Domain Numerical Simulation of Electronic Circuits and Surface Acoustic Wave Devices Using Their Admittance Parameters

We present a method to calculate the transient response of electronic circuits when these contain elements whose behaviors are given by their admittance matrices in the frequency domain. After describing this method in detail, an amplifier with resistive networks and interdigital transducers using specific input signals was proposed to test the method, and these results agreed when compared with those obtained with a simulation program with integrated circuit emphasis (SPICE)-based program. Besides, the simulation of two oscillators are presented; the first has a feedback network consisting of serial-connected equivalent circuits of crystals, and the second uses a feedback network with a surface acoustic wave (SAW) delay line. For the first oscillator, the waveforms obtained using this method and a SPICE-based program considering two different numerical integration methods were compared, and they looked similar, but all signals have different rise times because these simulations are very sensitive to inherent numerical errors. The simulation of a SAW delay line oscillator and its input and output voltages and currents were obtained, and its fundamental frequency was 77.77 MHz. These simulated results were validated experimentally through the oscillation frequency, which was found using the ${S}$ -parameters of the amplifier and the delay line and an oscillation criterion, and it was measured directly in the circuit. The experimental oscillation frequencies were 76.9 and 77.5 MHz, respectively, and the errors between simulation and experimentation were approximately 1%.

Noise Analysis and Comparison of Phase- and Frequency-Detecting Readout Systems: Application to SAW Delay Line Magnetic Field Sensor

Transmission surface acoustic wave (SAW) sensors are widely used in various fields of application. In order to maximize the limit of detection (LOD) of such sensor systems, it is of high importance to understand and to be able to quantify the relevant noise sources. In this paper, low noise readout systems for the application with a SAW delay line magnetic field sensor in an open-loop and closed-loop configuration are presented and analyzed with regard to their phase noise contribution. By applying oscillator phase noise theory to closed-loop sensor systems, it is shown that the phase noise of the SAW delay line oscillator can be predicted accurately. This allows the derivation of expressions for the limits of detection for both readout structures. Based on these equations, the equivalence between the LOD of open-loop and closed-loop SAW delay line readout can be shown analytically, assuming that the sensor contributes the dominant phase noise. This equality is verified by measurements. These results are applicable to all kinds of phase sensitive delay line sensors.

Phase measurement by using a forced delay-line oscillator and its application for an acoustic fiber sensor.

We demonstrate, theoretically and experimentally, a new method to measure small changes in the cavity length of oscillators. The method is based on the high sensitivity of the phase of forced delay-line oscillators to changes in their cavity length. The oscillator phase is directly detected by mixing the oscillator output with the injected signal. We describe a comprehensive theoretical model for studying the signal and the noise at the output of a general forced delay-line oscillator with an instantaneous gain saturation and an amplitude-to-phase conversion. The results indicate that the magnitude and the bandwidth of the oscillator response to a small perturbation can be controlled by adjusting the injection ratio and the injected frequency. For signals with a frequency that is smaller than the device bandwidth, the oscillator noise is dominated by the noise of the injected signal. This noise is highly suppressed by mixing the oscillator output with the injected signal. Hence, the device sensitivity at frequencies below its bandwidth is limited only by the internal noise that is added in a single roundtrip in the oscillator cavity. We demonstrate the use of a forced oscillator as an acoustic fiber sensor in an optoelectronic oscillator. A good agreement is obtained between theory and experiments. The magnitude of the output signal can be controlled by adjusting the injection ratio while the noise power at low frequencies is not enhanced as in sensors that are based on a free-running oscillator.

Longitudinal mode selection in a delay-line homogeneously broadened oscillator with a fast saturable amplifier.

Homogeneously broadened delay-line oscillators such as lasers or optoelectronic oscillators (OEOs) can potentially oscillate in a large number of cavity modes that are supported by their amplifier bandwidth. In a continuous wave operating mode, the oscillating mode is selected between one or few cavity modes that experience the highest small-signal gain. In this manuscript, we show that the oscillation mode of a homogeneously broadened oscillator can be selected from a large number of modes in a frequency region that can be broader than the full width at half maximum of the effective cavity filter. The mode is selected by a short-time injection of an external signal into the oscillator. After the external signal is turned off, the oscillation is maintained in the selected mode even if this mode has a significantly lower small-signal gain than that of other cavity modes. The stability of the oscillation is obtained due to nonlinear saturation effect in the oscillator amplifier. We demonstrate, experimentally and theoretically, mode selection in a long cavity OEO. We could select any desired mode between 400 cavity modes while maintaining ultra-low phase noise in the selected mode and in the non-oscillating modes. No mode-hopping was observed during our maximum measurement duration of about 24 hours.

Tunable optoelectronic oscillator with an embedded delay-line oscillator for fine steps

Tunable optoelectronic oscillator (OEO) with an embedded delay-line oscillator (EDO) for fine steps is presented. A delay-line oscillator consisting of an amplifier, phase shifter, and electrical delay line is embedded in the general single loop OEO. The oscillation frequency is controlled by the EDO loop phase, which is adjusted by the phase shifter. Without any narrow radio frequency bandpass filter, about 340 MHz tunable range with a fine step of ∼100 kHz is realized by directly tuning the direct current voltage of the phase shifter for 8 GHz oscillation. We also experimentally demonstrate κ-band tunable microwave signal generation within 22.18 to 23.32 GHz. The tunable accuracy and tunable range have a better performance compared to other OEO schemes with a fine frequency tunable step. The phase noise of the generated 22.25 GHz microwave signal is −108.7 dBc∕Hz at 10 kHz offset. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1.OE.55.3.031117)

Phase noise management of spin-wave delay-line oscillators

A phase noise of microwave oscillators having an active ring circuitry with a spin- wave delay line is theoretically and experimentally investigated. The delay line was made with yttrium iron garnet (YIG) film epitaxially grown on gadolinium gallium garnet substrate. Obtained results demonstrate a management of the oscillator phase noise with a variation of the distance between antennas used for excitation and reception of spin waves in the YIG film.

Optimization of surface acoustic wave-based rate sensors.

The optimization of an surface acoustic wave (SAW)-based rate sensor incorporating metallic dot arrays was performed by using the approach of partial-wave analysis in layered media. The optimal sensor chip designs, including the material choice of piezoelectric crystals and metallic dots, dot thickness, and sensor operation frequency were determined theoretically. The theoretical predictions were confirmed experimentally by using the developed SAW sensor composed of differential delay line-oscillators and a metallic dot array deposited along the acoustic wave propagation path of the SAW delay lines. A significant improvement in sensor sensitivity was achieved in the case of 128° YX LiNbO3, and a thicker Au dot array, and low operation frequency were used to structure the sensor.

GaN/SiC based surface acoustic wave structures for hydrogen sensors with enhanced sensitivity

In this article, we present an application of GaN/SiC heterostructures for Surface Acoustic Wave (SAW) hydrogen sensors with enhanced sensitivity. We demonstrate that the mass-loading sensitivity of such sensors can be increased by using shorter acoustic wavelengths and by confining the acoustic wave energy in an epitaxial waveguide. The effect of different Rayleigh-like modes on the mass-loading sensitivity is also discussed. The SAW wavelength-dependent phase and group velocity and electromechanical coupling constants were determined from electrical measurements. The outcome was used to design a microwave SAW delay-line oscillator. Its sensing characteristics are presented. The oscillator frequency shift was larger than 60kHz after exposure to 1000ppm H2/N2. The sensor reaction time was about 12s for the same sensing conditions at room temperature.

Synchronization between two weakly coupled delay-line oscillators

We study theoretically the generation of a continuous-wave signal by two weakly coupled delay-line oscillators. In such oscillators, the cavity length is longer than the wavelength of the signal. We show by using an analytical solution and comprehensive numerical simulations that in delay-line oscillators, the dynamics of the amplitude response cannot be neglected even when the coupling between the oscillators is weak. Therefore, weakly coupled delay-line oscillators cannot be accurately modeled by using coupled phase-oscillator models. In particular, we show that synchronization between the oscillators can be obtained in cases that are not allowed by coupled phase-oscillator models. We study the stability of the continuous-wave solutions. In delay-line oscillators, several cavity modes can potentially oscillate. To ensure stability, the bandwidth of the delay-line oscillator should be limited. We show that the weakly coupled delay-line oscillator model that is described in this paper can be used to accurately model the synchronization between two weakly coupled optoelectronic oscillators. A very good quantitative agreement is obtained between a comprehensive numerical model to study optoelectronic oscillators and the model results given in this paper.

Design and process test of a novel MOEMS accelerometer based on Raman—Nath diffraction

A novel micro-opto-electro-mechanical system (MOEMS) accelerometer based on Raman—Nath diffraction is presented. It mainly consists of an FPW delay line oscillator and optical strip waveguides. The fundamental theories and principles of the device are introduced briefly. A flexural plate-wave delay-line oscillator is designed to work as an acousto-optic (AO) shifter, which has a Klein—Cook parameter of 0.38. Single-mode optical strip waveguides of 2 μm in width and thicknesses of 0.6 μm are designed by using the effective index method for light transmission. The Ey00 mode waveguide polarizers are designed to ensure the consistency of the light polarization in the waveguides. The fabrication process, based on (100) oriented, 450-μm-thick silicon wafers is proposed in detail, and some difficulties in the process are discussed carefully. At last, a series of process tests are undertaken to solve the proposed problems. The results indicate that the proposed design and fabrication process of the device is dependable and realizable.

Theoretical analysis and concept demonstration of a novel MOEMS accelerometer based on Raman—Nath diffraction

The design and simulation of a novel microoptoelectromechanical system (MOEMS) accelerometer based on Raman—Nath diffraction are presented. The device is planned to be fabricated by microelectromechanical system technology and has a different sensing principle than the other reported MOEMS accelerometers. The fundamental theories and principles of the device are discussed in detail, a 3D finite element simulation of the flexural plate wave delay line oscillator is provided, and the operation frequency around 40 MHz is calculated. Finally, a lecture experiment is performed to demonstrate the feasibility of the device. This novel accelerometer is proposed to have the advantages of high sensitivity and anti-radiation, and has great potential for various applications.

Enhanced Sensitivity of Novel Surface Acoustic Wave Microelectromechanical System-Interdigital Transducer Gyroscope

In this paper, we present a novel microelectromechanical system-interdigital transducer (MEMS-IDT) surface acoustic wave (SAW) gyroscope with an 80 MHz central frequency on a 128° YX LiNbO3 wafer. The developed MEMS-IDT gyroscope is composed of a two-port SAW resonator, a dual delay line oscillator, and metallic dots. The SAW resonator provides a stable standing wave, and the vibrating metallic dot at an antinode of the standing wave induces the second SAW in the normal direction of its vibrating axis. The dual delay line oscillator detects the Coriolis force by comparing the resonant frequencies between two oscillators through the interference effect. The coupling of mode (COM) modeling was used to extract the optimal design parameters prior to fabrication. In the electrical testing by the network analyzer, the fabricated SAW resonator and delay lines showed low insertion loss and similar operation frequencies between a resonator and delay lines. When the device was rotated, the resonant frequency differences between two oscillators linearly varied owing to the Coriolis force. The obtained sensitivity was approximately 119 Hz deg-1 s-1 in the angular rate range of 0–1000 deg/s. Satisfactory linearity and superior directivity were also observed in the test.

Implementation of Surface Acoustic Wave Vapor Sensor Using Complementary Metal–Oxide–Semiconductor Amplifiers

A surface acoustic wave (SAW) vapor sensor is presented in this work. A SAW delay line oscillator on quartz substrate with the high gain complementary metal–oxide–semiconductor (CMOS) amplifier using a two-poly–two-metal (2P2M) 0.35 µm process was designed. The gain of the CMOS amplifier and its total power consumption are 20 dB and 70 mW, respectively. The achieved phase noise of this SAW oscillator is -150 dBc/Hz at 100 kHz offset. The sensing is successfully demonstrated by a thin poly(epichlorohydrin) (PECH) polymer film on a SAW oscillator with alcohol vapor. This two-in-one sensor unit includes the SAW device and the CMOS amplifier provides designers with comprehensive model for using these components for sensor circuit fabrication. Furthermore it will be promising for future chemical and biological sensing applications.

Detection of Shallow Underground Buried Object Using Air Vibration Probe

An air vibration probe is a device to measure an acoustic impedance using acoustic delay line oscillation. The frequency is changed when the acoustic impedance is changed. If some objects are varied, the frequency is expected to be changed in the case of the shallow underground detection. The advantage of this device is that it can detect the underground object easily without any contacts or destructions. Two experiments were practiced to study the relation among the frequency, the space between the probe and the ground, and the depth of object. The space was changed with the buried objects in various depths. The frequency became higher when the space became wider. In addition, the frequency was changed more obviously when the space was narrower. The probe scanned the buried objects in the fixed space. The objects were buried in various depths. The frequency became high when the object was buried shallower. In conclusion, the air vibration probe can detect the buried object because the frequency became high when something was buried.

A micro rate gyroscope based on the SAW gyroscopic effect

We propose a micro rate gyroscope (MRG) based on the surface acoustic wave (SAW) gyroscopic effect for extremely high-shock military applications. We not only derived theoretically the SAW gyroscopic gain factor in a ST-cut quartz by introducing a wave velocity ratio and the perturbation method, but also verified this gain factor by experiment. The proposed SAWMRG, which consists of two delay-line oscillators, operates as a differential scheme. To estimate an inherent insertion loss, we adopted the equivalent circuit model in the design process of the delay line. The 9 × 9 mm2 SAWMRG was fabricated on a ST-cut quartz and loaded into a specially designed low temperature co-fired ceramic (LTCC) package to ensure good RF characteristics. The center frequency and the insertion loss of the delay line are measured at 98.6 MHz and 15.2 dB, respectively. We evaluated the performance of the SAWMRG, using a rate table and stochastic noise analysis, revealing a sensitivity of 0.431 Hz deg−1 s−1 in the angular rates up to 2000 deg s−1 and a white noise of 0.55 deg s−1 Hz−1/2, respectively. Consequently the feasibility of the proposed SAWMRG was verified through a set of performance evaluations, confirming the theoretical predictions.