Low Phase Noise Microwave Oscillators Research Articles

Ultralow noise microwave synthesis via difference frequency division of a Brillouin resonator

Low phase noise microwave oscillators are at the center of a multitude of applications that span the gamut of photonics and electronics. Within this space, optically derived approaches to microwave frequency synthesis are particularly compelling owing to their unique combination of ultrawideband frequency access and the potential for resiliency to temperature and environmental perturbation via common-mode noise rejection. We demonstrate here an optical frequency divider that uses the 30 terahertz frequency gap between two stimulated Brillouin scattering (SBS) lasers as the basis for frequency division. The resulting microwave signal, centered at 10 GHz frequency, exhibits exceptionally low phase noise levels of −95dBc/Hz and −110dBc/Hz at 10 Hz and 100 Hz frequency offset, respectively. Moreover, the two SBS lasers, generated from a common fiber resonator, exhibit a high degree of correlated noise cancellation in their frequency difference. We measure 16.1 dB of noise rejection against intentionally applied vibrations, thus showcasing a promising pathway towards portable and robust ultralow noise photonic-microwave synthesis.

Low phase noise microwave oscillator based on gain driven polariton

Low phase noise oscillators are key building blocks of many high-end microwave systems. This work introduces a phase noise reduction mechanism through a gain driven polariton platform, where coherent coupling is used to suppress frequency distribution around the carrier, effectively reducing the phase noise. The design process for achieving low phase noise performance is outlined, and three prototypes are constructed, all of which feature key components, such as gain-embedded planar microwave cavity, yttrium iron garnet, and magnets. In particular, the first prototype is used to showcase the phase noise reduction mechanism, while the second prototype, a fixed-frequency oscillator working at 3.544 GHz, exhibits phase noise levels of −117 and −132 dBc/Hz at 10 and 100 kHz offset frequencies, respectively. The third prototype offers a tuning range from 2.1 to 2.7 GHz, while maintaining phase noise levels comparable to the second prototype.

Low phase noise microwave oscillator with greater than 60 dB second‐harmonic suppression

This study presents a microwave oscillator in which an innovative hybrid microstrip and substrate integrated waveguide filter is proposed for phase noise reduction. By virtue of equivalent circuit, the specific topology of this filter is clearly revealed and verified by both the simulation and the experiment. It can realize a third-order elliptic bandpass response with two transmission zeros near the passband. Specific phase response can be formed, in which a high group delay can be achieved within a narrow frequency range around the centre frequency. This feature makes the filter performance very flexible for its application in microwave oscillator, and then reduces its phase noise. For demonstration, an oscillator example at 9.0 GHz was deigned, fabricated and measured. The measured phase noise at 100 kHz away from the oscillation frequency is as low as −120.06 dBc/Hz. Furthermore, the proposed oscillator is featured by greater than 60 dB second-harmonic suppression and at least the third harmonic is suppressed.

Fast automatic frequency calibration assisted phase-locked highly stable optoelectronic oscillator

Highly stable, low phase noise microwave oscillators are essential for various applications. An optoelectronic oscillator (OEO) can overcome the short-term phase noise limitation of pure electronic oscillators at high oscillation frequency. Nonetheless, the long-term frequency stability should be addressed. To stabilize the frequency of OEO, a phase-locked loop (PLL) is widely used to synchronize the OEO to a stable reference. However, due to the narrow free-spectral-range (FSR) of the oscillation cavity of the OEO, the pull-in range of the PLL is limited. It is challenging to acquire phase-locking at startup and phase-relocking when mode-hopping of OEO occurs. Here, by using an automatic frequency calibration (AFC) assisted PLL, we attain a highly stable 10 GHz phase-locked OEO with robust phase-locking at startup and phase-relocking when mode-hopping of OEO occurs, for the first time. With the use of a fast digitally-controlled frequency shifter and a real-time frequency error detection unit in the AFC loop, the phase-locking and phase-relocking time are below 120 ms. Furthermore, it shows the phase noise of -135 dBc/Hz at 10 kHz offset, side-mode suppression ratio (SMSR) of 128 dBc, and Allan deviation of 4.8×10-11 at 5000 s for the phase-locked OEO. We thoroughly investigate the dynamics of the automatic frequency calibration, the phase-locking process, the phase-relocking after OEO mode-hopping, the system under vibration, and the frequency switching. Our approach is promising to generate a highly stable, low phase noise, and determinate frequency microwave signal, which can be used as a low phase noise reference for a microwave frequency synthesizer and high performance sampling clock for a data conversion system.

Theoretical investigation of an ultra-low phase noise microwave oscillator based on an IF crystal resonator-amplifier and a microwave photonic frequency transposer

Resonator Q-factor and amplifier flicker noise are the most important parameters that determine the phase noise of microwave oscillators. The Q-factor of intermediate frequency (IF) crystal resonators at IF frequencies can be larger than that of microwave resonators at microwave frequencies. In addition, flicker noise of IF amplifiers can be less than that of microwave amplifiers. One of the well-known usual ways to implement low phase noise microwave oscillators is to use ultra-low phase noise IF crystal oscillators and frequency multipliers. In this paper a new method to implement such oscillators based on IF crystal resonators and amplifiers, called a transposed-frequency microwave oscillator, is proposed. In the proposed structure, a microwave photonic frequency transposer is used to downconvert RF to IF followed by a high-Q IF crystal filter and low flicker noise IF amplifier and then upconverting IF to RF frequency. This novel method in comparison to the well-known multiplier-based microwave oscillators presents significant advantages. In this paper, the proposed new structure is introduced, and a theoretical model is developed to study its performance. Oscillation frequency and amplitude, equivalent Q-factor, phase noise, etc., are theoretically studied and compared with the performances of the well-known microwave oscillators based on frequency multipliers and optoelectronic oscillators. It is shown that the phase noise of the proposed microwave oscillator can be less than −130 dBc/Hz at 100 Hz from a 10 GHz carrier with a noise floor less than −165 dBc/Hz.

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.

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.

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.

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.

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.

Low phase-noise microwave oscillators with interferometric signal processing

Phase-noise spectral density of a 9-GHz oscillator has been reduced to -160 dBc/Hz at 1-kHz offset frequency, which is the lowest phase noise ever measured at microwave frequencies. This performance was achieved by frequency locking a conventional loop oscillator to a high-Q sapphire dielectric resonator operating at the elevated level of dissipated power (/spl sim/0.4 W). Principles of interferometric microwave signal processing were applied to generate the error signal for the frequency control loop. No cryogenics were used. Two almost identical oscillators were constructed to perform classical two-oscillator phase-noise measurements where one oscillator was phase locked to another. The phase locking was implemented by electronically controlling the level of microwave power dissipated in the sapphire dielectric resonator.

Low phase noise microwave oscillators based on HTS shielded dielectric resonators

To meet the specifications of future radar and communication systems we developed a low phase noise microwave oscillator. This feedback oscillator consists of a commercial MESFET-amplifier at room temperature and a LaAlO/sub 3/ dielectric resonator with high temperature superconducting (HTS) shielding at 63 K. The resonator operating at a resonance frequency of 5.6 GHz showed unloaded quality factors in the 10/sup 5/ to 10/sup 6/ range. By means of a strong resonator coupling (|S/sub 21/|=6 dB) and an amplifier gain of 20 dB we obtained an output power of +15 dBm. The phase noise L(f/sub m/) of the oscillator was below the detection limit for offset frequencies beyond 10 kHz. For offset frequencies below 5 kHz measurements revealed perfect L(f/sub m/)/spl prop/f/sub m//sup .3/-behaviour according to the Leeson model. The phase noise was -110 dBc/Hz at 1 kHz offset and -130 dBc/Hz at 10 kHz. This phase noise performance is superior to state of the art SAW- or quartz oscillators for f/sub m/>10 kHz. To further reduce the phase noise performance close to the carrier we investigated the implementation of a phase locked loop (PLL). The long term temperature stability of the oscillator frequency can be enhanced by introducing a central cylinder made from rutile (TiO/sub 2/). We present numerical and experimental results on this compensation.

Low 1/f noise SiGe HBTs with application to low phase noise microwave oscillators

SiGe HBTs featuring a high quality oxide passivation show ideal Gummel plots and low 1/f noise with corner frequencies down to 300 Hz. The measured KB-factor of 2.6 × 10–10 µm2s is the lowest of any previously reported HBT. With an f⊤ of 40 GHz, the devices are ideal for low phase noise microwave oscillators. A simple 10 GHz microstrip resonator showed –100 dBc at 100 kHz off carrier.

The active device characterization and modelling problem in low phase noise microwave oscillator design

The conversion of low frequency noise into phase noise in a high frequency oscillator depends strongly on the active device type and operating conditions. Experimental set-ups are presented to achieve the choice of a transistor to be used in low noise oscillators and to study the correlation between phase noise and low frequency noise. Modelling guidelines are then described to help in the understanding of the noise conversion process. Simple rules of noise reduction are derived from simplified small signal models but the emphasis is put on more complete modelling approaches. These accurate models are affected by yet unsolved (or partially unsolved) problems such as : the influence of the large signal behaviour on the noise sources or the physically unacceptable cancellation of the phase noise in special biasing conditions.

Ultra-low-noise microwave oscillator with advanced phase noise suppression system

An advanced phase noise reduction technique has been developed to improve the short-term frequency stability of microwave oscillators. The technique is based upon an ultrasensitive microwave frequency discriminator with effective noise temperature close to its physical temperature. The phase noise spectral density of a 9 GHz microwave loop oscillator incorporating such a discriminator has been measured as -120 dBc/Hz and -150 dBc/Mz at offset frequencies of 100 Hz and 1 kHz, respectively. This performance is at least 25 dB better than current state of the art. The developed phase noise reduction technique is quite general and can have valuable implications for the design of various low phase noise microwave oscillators.