Low Phase Noise Microwave Research Articles

A Dual-Band Low Phase Noise Microwave Oscillator Based on a Novel High Q Complementary Split Ring Resonator

ABSTRACTIn the present article, a dual-band low-phase noise oscillator is designed, constructed, and experimentally verified using a dual-band high group delay complementary split ring resonator. This oscillator is of serial feedback type. Oscillation frequencies have been designed at group delay peak of resonator so as to remarkably reduce the phase noise of an oscillator at two frequency bands. Additionally, the oscillator can be extended to a voltage-controlled-oscillator by attaching a varactor diode on the resonator. The oscillation frequencies of the oscillator in the present article are approximately 4.75 GHz and 5.33 GHz. The oscillator oscillates at only one frequency band in each moment. Oscillation frequency is selected by means of a switch. If the switch is on, oscillation frequency will be 4.75 GHz, the measured phase noise will be around –108 dBc/Hz at offset frequency of 100 KHz, and frequency tuning range with varactor diode voltage variation will be approximately 65 MHz around this oscillation frequency. On the other hand, if the switch is off, oscillation frequency will be 5.33 GHz, the measured phase noise will be around –129 dBc/Hz at offset frequency of 100 KHz, and frequency tuning range with varactor diode voltage variation will be approximately 81 MHz around this oscillation frequency.

Widely tunable, low phase noise microwave source based on a photonic chip.

Spectrally pure microwave sources are highly desired for several applications, ranging from wireless communication to next generation radar technology and metrology. Additionally, to generate very pure signals at even higher frequencies, these advanced microwave sources have to be compact, low in weight, and low energy consumption to comply with in-field applications. A hybrid optical and electronic cavity, known as an optoelectronic oscillator (OEO), has the potential to leverage the high bandwidth of optics to generate ultrapure high-frequency microwave signals. Here we present a widely tunable, low phase noise microwave source based on a photonic chip. Using on-chip stimulated Brillouin scattering as a narrowband active filter allows single-mode OEO operation and ultrawide frequency tunability with no signal degeneration. Furthermore, we show very low close-to-carrier phase noise. This Letter paves the way to a compact, fully integrated pure microwave source.

A low phase noise microwave oscillator based on a high Q SIW cavity CSRR band-pass filter

This study designed, developed and put empirically into test a low phase noise oscillator using a complementary split ring resonator filter of high Q factor as a frequency stabilization and selection element. This oscillator is of parallel feedback type. The oscillator was designed at the group-delay-peak frequency of the filter to achieve a dramatic reduction in the phase noise of the oscillator. At the oscillation frequency 5.36 GHz, the phase noise was measured −128 at 100 kHz offset frequency and −145 at 1 MHz offset frequency. The designed oscillator revealed the output power 7 dBm. According to the scientific literature, the proposed oscillator was found to enjoy the best performance at low phase noise for planar microwave oscillators.

Low phase noise microwave extraction from femtosecond laser by frequency conversion pair and IF-domain processing.

Extraction of a microwave component from a low-time-jitter femtosecond pulse train has been attractive for current generation of spectrally pure microwave. In order to avoid the transfer from the optical amplitude noise to microwave phase noise (AM-PM), we propose to down-convert the target component to intermediate frequency (IF) before the opto-electronic conversion. Due to the much lower carrier frequency, the AM-PM is greatly suppressed. The target is then recovered by up-conversion with the same microwave local oscillation (LO). As long as the time delay of the second LO matches that of the IF carrier, the phase noise of the LO shows no impact on the extraction process. The residual noise of the proposed extraction is analyzed in theory, which is also experimentally demonstrated as averagely around -155 dBc/Hz under offset frequency larger than 1 kHz when 10-GHz tone is extracted from a home-made femtosecond fiber laser. Large tunable extraction from 1 GHz to 10 GHz is also reported.

Model for low phase noise microwave photonic link and its application in opto-electronic oscillator

In this paper, the theory model of phase noise for microwave photonic link is derived and verified by experiments first, considering both types of flicker and white noises. In order to decrease the phase noise of link, low-phase noise amplifier and high-linear photodiode is applied in microwave photonic link. Based on this model, the effect of phase noise of microwave photonic link on the OEO is also analyzed and we found the lower-phase noise microwave photonic link results in better-characteristics OEO.

High-Power Photodiodes for Analog Applications

High-power, high-speed photodiodes are being used in an increasing number of applications including fiber optic antenna links, radio frequency (RF) over fiber, and photonic generation of low phase noise microwave signals. The fact that the photodiode (PD) can be operated at high photocurrent levels provides several improvements in these systems including high dynamic range, high link gain, and low noise figure. In photonic wireless systems an antenna integrated photodiode can help to increase radiated RF power without the need for electronic amplification and hence simplify the RF circuitry at the antenna unit. To achieve high RF output power, various photodiode structures have been developed [1]–[4] among which the uni-traveling carrier (UTC) photodiode [3] has demonstrated high saturation current and high bandwidth. We have developed charge-compensated modified uni-traveling carrier (MUTC) photodiodes flip-chip bonded on high-thermal conductivity substrates to address the two primary effects that limit the RF output power of photodiodes, space-charge and thermal.

Long-Term Frequency Stabilization of an Optoelectronic Oscillator Using Phase-Locked Loop

We demonstrate an approach of long-term frequency stabilization of a single-loop optoelectronic oscillator (OEO) with a phase-locked loop (PLL). The OEO is frequency locked to a highly stable microwave reference via a PLL circuit with a PID regulator. With this approach, we obtained a highly stable 3.035-GHz microwave signal with phase noise of −65 dBC/Hz at 10-Hz offset frequency, and the frequency stability has reached 6.98 × 10−14 at average time of 1000 s. These experimental results show that the PLL-locked OEO is greatly improved in both long-term frequency stability and phase noise performance at low offset frequencies. Therefore, the PLL-locked OEO can be a strong candidate of highly stable, low phase noise microwave generators for microwave photonics applications.

High Power Photodiodes for Microwave Applications

High Power Photodiodes for Microwave Applications

Dual photo-detector system for low phase noise microwave generation with femtosecond lasers

Low phase noise microwave signals can be generated by photo-detecting the pulse train of an optical frequency comb locked to a high spectral purity continuous-wave optical reference. Amplitude-to-phase noise conversion is, however, a well-known limitation to this technique. Great care is usually required to overcome this constraint due to its strong dependence on the impinging optical power. Here we demonstrate the combined use of "magic point" operating conditions of photodetectors, pulse repetition rate multipliers, and coherent addition of microwave signals to realize a microwave extraction device largely immune to amplitude-to-phase conversion effects over a large range of impinging optical powers.

Low-noise and broadband optical frequency comb generation based on an optoelectronic oscillator

A novel scheme to generate broadband high-repetition-rate optical frequency combs and low phase noise microwave signals simultaneously is proposed and experimentally demonstrated. By incorporating an optical frequency comb generator in an optoelectronic oscillator loop, more than 200 lines are generated for a 25 GHz optical frequency comb, and the single-sideband phase noise is as low as -122 dBc/Hz at 10 kHz offset for the 25 GHz microwave signal. 10 and 20 GHz optical frequency combs and microwave signals are also generated. Unlike the microwave frequency synthesizer, the phase noise of the microwave signals generated by this new scheme is frequency independent.

Design of Ultra-Low Phase Noise and High Power Integrated Oscillator in $0.25~\mu{\rm m}$ GaN-on-SiC HEMT Technology

A novel ultra-low phase noise and high power integrated oscillator is presented in this letter. The proposed oscillator, based on GaN-on-SiC high electron mobility transistor (HEMT) with 0.25 μm gate length and 800 μm gate width, delivers 21 dBm output power when biased at VGS=-3 V and VDD = 28 V. Phase noise was measured to be -112 dBc/Hz at 100 kHz offset and -135 dBc/Hz at 1 MHz offset from 7.9 GHz carrier, respectively. To the best of our knowledge, it achieves the lowest phase noise compared to other GaN HEMT based integrated oscillators. It is also comparable in performance to the state-of-the-art ultra-low phase noise oscillators designed in InGaP technology, while delivering more than 10 times higher output power. In addition, this oscillator also exhibits a minimum second harmonic suppression of 28.65 dBc and more than 60 dBc third harmonic suppression. The chip size is 1.1×0.6 mm2. The results show that the proposed oscillator has the potential to be used for both low phase noise and high power microwave source applications.

Design of Low Phase-Noise Oscillator Based on a Hairpin-Shaped Resonator Using Composite Right/Left-Handed Transmission Line

In this letter, a low phase-noise microwave oscillator based on a hairpin-shaped resonator (HSR) using a composite right/left-handed transmission line (CRLH TL) is proposed. The proposed HSR consists of the conventional transmission line (CTL) and the CRLH TL. In order to obtain the high- Q factor, an electric field is concentrated on the CRLH TL, and then the CRLH TL provides a low loss due to a slow wave effect. The proposed HSR has a very compact size of 0.105 λg ×0.19 λg. An oscillator based on the HSR was designed, fabricated and measured. At the oscillation frequency of 4.95 GHz, the measured phase noise is -120.5 dBc/Hz at 100 kHz offset with 4.93 dBm output power.

Temporal solitons in optical microresonators

Dissipative solitons can emerge in a wide variety of dissipative nonlinear systems throughout the fields of optics, medicine or biology. Dissipative solitons can also exist in Kerr-nonlinear optical resonators and rely on the double balance between parametric gain and resonator loss on the one hand and nonlinearity and diffraction or dispersion on the other hand. Mathematically these solitons are solution to the Lugiato-Lefever equation and exist on top of a continuous wave (cw) background. Here we report the observation of temporal dissipative solitons in a high-Q optical microresonator. The solitons are spontaneously generated when the pump laser is tuned through the effective zero detuning point of a high-Q resonance, leading to an effective red-detuned pumping. Red-detuned pumping marks a fundamentally new operating regime in nonlinear microresonators. While usually unstablethis regime acquires unique stability in the presence of solitons without any active feedback on the system. The number of solitons in the resonator can be controlled via the pump laser detuning and transitions to and between soliton states are associated with discontinuous steps in the resonator transmission. Beyond enabling to study soliton physics such as soliton crystals our observations open the route towards compact, high repetition-rate femto-second sources, where the operating wavelength is not bound to the availability of broadband laser gain media. The single soliton states correspond in the frequency domain to low-noise optical frequency combs with smooth spectral envelopes, critical to applications in broadband spectroscopy, telecommunications, astronomy and low phase-noise microwave generation.

High Q, high frequency, high overtone bulk acoustic resonator with ZnO films

Bulk acoustic wave resonators with piezoelectric films have been widely explored for the small size and high quality factor (Q) at GHz. This paper describes a high overtone bulk acoustic resonator (HBAR) based on Al/ZnO/Al sandwich layers and c-axis sapphire substrate. ZnO film with high quality c-axis orientation has been obtained using DC magnetron sputtering. The fabricated HBAR presents high Q at the multiple resonances from a 0.5–4.0 GHz wide band with a total size (including the contact pads) of 0.6 mm×0.3 mm×0.4 mm. The device exhibits the best acoustic coupling at around 2.4 GHz, which agrees with the simulation results based on the one-dimensional Mason equivalent circuit model. The HBAR also demonstrates Q values of 30 000, 25 000, and 6500 at 1.49, 2.43, and 3.40 GHz, respectively. It is indicated that the HBAR has potential applications for the low phase noise high frequency oscillator or microwave signal source.

Design of Low Phase-Noise Microwave Oscillator and Wideband VCO Based on Microstrip Combline Bandpass Filters

This paper presents a new low phase-noise microwave oscillator and wideband voltage-controlled oscillator (VCO) based on microstrip combline bandpass filters. For this type of oscillator, the passband filter is embedded into the feedback loop to treat as a frequency stabilization element. Instead of designing the oscillator at the group-delay-peak frequency of the filter to achieve a good phase-noise performance, in this paper, the peak frequency of the complex quality factor Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> is adopted for oscillator design. To demonstrate the effectiveness of using Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> -peak frequency, two filter-based oscillators are implemented at the Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> -peak and group-delay-peak frequencies, respectively. The oscillator designed at the Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> -peak frequency improves the phase-noise about 10 dB as compared with that realized at the group-delay-peak frequency. The developed oscillator with the three-pole combline filter is experimentally demonstrated at 2.05 GHz with -148.3-dBc/Hz phase noise at 1-MHz offset frequency. Moreover, by attaching a varactor on each resonator of the combline filter, the oscillator can be extended to a wideband VCO. The developed VCO has a frequency tuning range from 1.3 to 2.2813 GHz with a 54.8% bandwidth. Over this frequency range, all the phase noises measured at 1-MHz offset frequency are better than -117.19 dBc/Hz.

기판 집적형 도파관(SIW)과 Complementary Split Ring Resonator(CSRR)로 구현한 저위상 잡음 발진기 설계

A low phase-noise microwave oscillator is presented by a substrate integrated waveguide(SIW) loading a complementary split ring resonator(CSRR) in this paper. The unloaded -factor of the SIW cavity is increased by loading a complementary split ring resonator(CSRR) and its value exhibits 1960. It is theoretically and experimentally demonstrated that the proposed circuit generates 11.3 dBm of output power at 9.3 GHz and a phase-noise of -127.9 dBc/Hz at 1-MHz offset.

A low phase noise microwave source for atomic spin squeezing experiments in 87Rb

We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of (87)Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 × 10(5) (87)Rb atoms.

Microwave low phase noise oscillators using T-shaped stepped-impedance-resonator filters

Low phase noise microwave oscillators using T-shaped step-impedance-resonator (TSIR) filters are proposed and experimentally verified. Instead of using a high-quality factor resonator to design an oscillator, the TSIR filter is embedded into the feedback loop as a frequency stabilisation element. As the oscillator is designed at the group-delay-peak frequency of the filter, one can improve the phase-noise performance. Moreover, to miniaturise the oscillator circuit size, the TSIR filter can be further evolved into a compact net-type filter by the folding technique. The developed oscillators using TSIR filters at 1 and 5.2 GHz have the measured phase noises of −131 and −132 dBc/Hz at 1 MHz offset frequency, respectively. On the other hand, as compared with oscillators using TSIR filters, using a net-type TSIR filter to develop the filter-based oscillator at 1 GHz can achieve a 38% circuit size reduction and a 4-dB phase noise improvement at 1 MHz offset frequency.

Microwave generation with low residual phase noise from a femtosecond fiber laser with an intracavity electro-optic modulator

Low phase-noise microwave generation has previously been demonstrated using self-referenced frequency combs to divide down a low noise optical reference. We demonstrate an approach based on a fs Er-fiber laser that avoids the complexity of self-referenced stabilization of the offset frequency. Instead, the repetition rate of the femtosecond Er-fiber laser is phase locked to two cavity-stabilized cw fiber lasers that span 3.74 THz by use of an intracavity electro-optic modulator with over 2 MHz feedback bandwidth. The fs fiber laser effectively divides the 3.74 THz difference signal to produce microwave signals at harmonics of the repetition rate. Through comparison of two identical dividers, we measure a residual phase noise on a 1.5 GHz carrier of -120 dBc/Hz at 1 Hz offset.

Characterizing a fiber-based frequency comb with electro-optic modulator

We report on the characterization of a commercial- core fiber-based frequency comb equipped with an intracavity free-space electro-optic modulator (EOM). We investigate the relationship between the noise of the pump diode and the laser relative intensity noise (RIN) and demonstrate the use of a low-noise current supply to substantially reduce the laser RIN. By measuring several critical transfer functions, we evaluate the potential of the EOM for comb repetition rate stabilization. We also evaluate the coupling to other relevant parameters of the comb. From these measurements, we infer the capabilities of the femtosecond laser comb to generate very-low-phase-noise microwave signals when phase-locked to a high-spectral-purity ultra-stable laser.