Showing papers by "Ulrich L. Rohde published in 2017"

Extensive performance evaluations of RF MEMS single-pole-multi-throw (SP3T to SP14T) switches up to X-band frequency

Abstract: This work presents wide range of compact and reliable single-pole-multi-throw (SPMT) radio frequency (RF) microelectromechanical system (MEMS) switches where the M (output) varies from 3 to 14 throws. The single dc-contact switch dimensions are 0.144 mm × 0.29 mm which are fabricated on 635 µm alumina substrate using a surface micromachining process. SPMT switching networks demonstrate a measured return loss of more than 14 dB, a worst case insertion loss of ~1.76 dB and isolation of ~14.5 dB up to 12 GHz. The maximum area of the fabricated SPMT switch is ~1.2 mm2. The SPMT switches are capable of handling 1 W of RF power up to >1 billion cycles at 25 °C, and sustained even up to >80 million cycles with 0.5 W at 85 °C. To the best of our knowledge, this is the first reported wide range of MEMS SPMT switches and their respective performance evaluations in the literature that has undergone extensive measurement stages.

Cross-Spectrum PM Noise Measurement, Thermal Energy, and Metamaterial Filters

Abstract: Virtually all commercial instruments for the measurement of the oscillator PM noise make use of the cross-spectrum method (arXiv:1004.5539 [physics.ins-det], 2010). High sensitivity is achieved by correlation and averaging on two equal channels, which measure the same input, and reject the background of the instrument. We show that a systematic error is always present if the thermal energy of the input power splitter is not accounted for. Such error can result in noise underestimation up to a few decibels in the lowest-noise quartz oscillators, and in an invalid measurement in the case of cryogenic oscillators. As another alarming fact, the presence of metamaterial components in the oscillator results in unpredictable behavior and large errors , even in well controlled experimental conditions. We observed a spread of 40 dB in the phase noise spectra of an oscillator, just replacing the output filter.

Limits in Timing Jitters of Forced Microwave Oscillator Using Optical Self-ILPLL

Abstract: A novel optical feedback technique using self-injection locked and phase locked loop (SILPLL) is employed for phase noise reduction of free-running microwave oscillators. Phase noise reduction of 27 dB at 10-kHz offset has been demonstrated by applying this technique for a 10-GHz state of art dielectric resonator oscillator achieving −137 dBc/Hz at 10-kHz offset. A phase noise prediction of this feedback technique is also presented, which very closely corroborates with experimental results. Analysis of SILPLL using the modeling has shown that further phase noise reductions could be achieved, by reducing the flicker phase noise of the long delay lines and microwave amplifiers. Phase noise of −147 dBc/Hz at 10-kHz offset is predicted when the relative intensity noise (RIN) is reduced to the RIN of −170 dB/Hz for an optical power leading to a photocurrent of 5 mA and the $\text{b}_{\mathrm {\mathbf {-1}}}$ (flicker noise) levels of −125 dBc/Hz for RF amplifiers.

Frequency synthesis of forced opto-electronic oscillators at the X-band

Abstract: Ultra-low phase noise performance is required for frequency agile local oscillators, which are the core for high resolution imagers, spectrum analyzers, and high speed data communications. A forced opto-electronic oscillator (OEO) benefits from frequency stabilization techniques for realizing a clean and low phase noise source at microwave and millimeter wave frequencies. Forced oscillation techniques of self-injection locking and self-phase lock loop are combined to provide an ultra-low oscillator phase noise both close-in and far-away from the carrier frequency, while a tunable yttrium iron garnet microwave filter combined with a wavelength tuned transversal filter are employed to implement both coarse and fine frequency tuning for a tunable X-band OEO. A phase noise of −137 dBc/Hz at an offset frequency of 10 kHz is achieved covering the frequencies of 9 to 11 GHz with a fine frequency tuning resolution of 44 Hz/pm and coarse tuning of 25 MHz/mA. Moreover, the long term stability of the output signal is tested, and a maximum frequency drift of 2 kHz is measured within 60 min for the X-band synthesizer.

Optimizing Phase-Noise Performance: Theory and Design Techniques for a Crystal Oscillator

Abstract: At the heart of today's communication systems lies the autonomous signal source, the oscillators. The design criteria for these are governed by a system's requirements (based on its applications). Oscillators have evolved over the past century and today offer a wide range of options with stringent specifications in terms of power consumption, performance, and cost. Optimizing for phase noise with improved overall performance is considered a key design criterion, and a figure of merit (FOM) that includes all important parameters then determines the oscillator performance [1]-[3].

Ku to V-band 4-bit MEMS phase shifter bank using high isolation SP4T switches and DMTL structures

Abstract: This work presents a micro-electro-mechanical system (MEMS) based on a wide-band 4-bit phase shifter using two back-to-back single-pole-four-throw (SP4T) switches and four different distributed MEMS transmission line (DMTL) structures that are implemented on 635 µm alumina substrate using surface micromachining process. An SP4T switch is designed with a series-shunt configuration and it demonstrates an average return loss of >17 dB, an insertion loss of 28 dB up to 60 GHz. A maximum area of the SP4T switch is ~0.76 mm2. Single-pole-single-throw and SP4T switches are capable of handling 1 W of radio frequency (RF) power up to >100 million cycles at 25° C; they can even sustained up to >70 million cycles with 1 W at 85 °C. The proposed wide-band phase shifter works at 17 GHz (Ku-band), 25 GHz (K-band), 35 GHz (Ka-band) and 60 GHz (V-band) frequencies. Finally,a 4-bit phase shifter demonstrates an average insertion loss of 10 dB and maximum phase error of ~3.8° at 60 GHz frequency over 500 MHz bandwidth. Total area of the fabricated device is ~11 mm2. In addition, the proposed device works well up to >107 cycles with 1 W of RF power. To the best of the author's knowledge, this is the best reported wide-band MEMS 4-bit phase shifter in the literature that works with a constant resolution.

Next generation radios: SDR and SDN

Abstract: This paper describes the applications of SDR (Software Defined Radio) and SDN (Software Defined Network) technology in the next generation radios.

Next generation 5G radio communication NW

Abstract: This paper discusses the expectations, challenges, and uncertainties of the next generation 5G radio communication networks. The acknowledged high expectations for new radios place challenges on designers and uncertainties on the selection of the frequency spectrum. Although, research community and industry leaders are engaged towards figuring out the dynamics of 5G (fifth generation), expectation continue high for the next-generation radio standard, which will require higher data rates, massive device connectivity, more system capacity, reduced latency, energy savings, and inexpensive solution. The transition from 4G to 5G can lead to significant augmentation in data rates and latency. Designers are engaged in cope with the needed dimension of time t in 5G, which aims at air latency of 10 Gbps at millimeter wave frequencies. Therefore, considerable design challenges stretch out ahead for system engineers to integrate novel technologies (CR, SDN, SDR), into interoperable platforms that intelligently connect to local and global NW and offers affordable solutions.

K-Band High Stablity and Resolution Frequency Synthesizers Using Forced Opto-Electronic Oscillators

Abstract: Forced opto-electronics oscillator (OEO) is a very promising way to build low phase noise oscillators. Forced techniques of self-injection locking phase locking (SILDPLL) are integrated with narrowband tunable RF filters to build OEO system to further reduce the phase noise and suppress side mode generated among standard OEOs because of long fiber delays. The narrowband tunable RF filter is based on an optical wavelength tuned transversal filter using a fiber Bragg grating as delay element cascaded with current tuned YIG filter to accomplish a 2kHz frequency resolution over K-band. Second harmonic generated frequency synthesized signals with close-in to carrier phase noise of −127 dBc/Hz at 10 kHz offset are reported by Vπ operation of a Mach-Zehnder (MZM) over 18 GHz to 22 GHz. 19” rack mount system is also constructed and long-term stability of 4.5 kHz over 60 min is measured at K-band, while a 3.5 kHz drift is measured for a tabletop realization.

High-resolution frequency synthesizers over X-band using SILPLL opto-electronic oscillators

Abstract: Optoelectronic oscillators with their demonstrated low phase noise are popular due to the increasing demand of very clean local oscillator and clock signal sources. Forced techniques are applied on an OEO system reducing the phase noise and suppresses side mode observed in standard OEO with long delays. A frequency synthesizer working at X-band is demonstrated using dispersive optical transversal filter cascaded with YIG filter to electronically fine and coarse tune the oscillation frequency of the synthesized frequency, as a replacement for fixed frequency high Q metallic filter. Close-in to carrier phase noise of −135 dBc/Hz at 10 kHz are reported by V π/2 operation of a Mach-Zehnder (MZM) over 9 GHz to 11 GHz with frequency tuning step as small as 10 kHz/pm.