Designers of oscillators and synthesizers need creative ways to achieve low phase noise in smaller packages in order to serve shrinking systems. To accomplish this, some manufacturers are using advanced materials and circuit techniques, as well as the latest software design tools, which can allow for extremely accurate simulations and speed time to market. Once a prototype is in hand, designers need to leverage the most robust methods and equipment to test it.

The pressure is definitely on to minimize phase noise in oscillators and synthesizers, even as applications move into higher frequency bands. “The general trend has been to develop higher frequency solutions with better noise performance (>10 GHz) and octave tuning solutions in the S and C bands,” notes Daniel Loomis, Sr. Applications Manager, Z-Communications. According to Stuart Rumley, Owner, Valon Technology LLC, the ability to keep phase noise in check is being helped by the availability of low-power, highly integrated semiconductor devices, especially phase-locked loops (PLLs) with integrated voltagecontrolled oscillators (VCOs). Rumley notes, “I will say that one key is to use the very lowest noise LDO regulators and buffer all RF outputs.”

Some companies are leveraging new technologies and methods. For instance, Z-Communications reports that it is applying thick-film component technology in a multilayer substrate to address phase-noise concerns. At Synergy Microwave, Bill Becker, Sales & Applications Regional Manager, explains, We apply our patented, lowphase- noise techniques to both the larger (0.5 x 0.5 in.) VCO packages and the smaller (0.3 x 0.3 in.) packages to achieve the lowest phase noise over a greater-than-octave operating frequency band. The technology emulates the high Q required for low phase noise with hybrid-mode planar resonators and three-dimensional structures.”

New oscillators and synthesizer designs with admirable phase noise specifications continue to roll out. Leveraging four differential voltagecontrolled oscillators (VCOs), the SKY73134 synthesizer from Skyworks Solutions is housed in a 5 x 5 mm, 32-pin RF land grid array (RFLGA) package. Particularly well suited for use in cellular base stations, the SKY73134 features normalized in-band phase noise of –211 dBc/Hz in a 30-kHz PLL bandwidth. Wenzel Associates also has a line of crystal oscillators for base stations, as well as other communications, military, and test equipment applications. The Small Fry oven-controlled crystal oscillator (OCXO), for instance, is optimized for use in Global Positioning System (GPS) receivers and demonstrates phase noise of –165 dBc/ Hz at 10 kHz offset. It measures 1.5 x 1.5 x 3 in.

Endwave Corporation recently announced its EWV0800YF dual-output VCOs that cover 3.65 to 4.4 GHz and 7.3 to 8.8 GHz. Phase noise for these components is specified at –116 dBc/Hz offset 100 kHz from the carrier in either band, with subharmonics of typically –41 dBc and second harmonics of typically –10 dBc. The company’s VCO portfolio includes dual-output models that operate through 15.5 GHz.

EM Research continues its commitment to miniature frequency synthesizers, recently announcing a series of frequency synthesizers and phase-locked oscillators targeted at very-small-aperture-terminal (VSAT) satellite communications systems. Earlier this year at IMS 2010, the company also announced dual-output VCOs for applications to 15.5 GHz. The phase noise for these units is –112 dBc/Hz offset 100 kHz from the carrier, while subharmonic levels are typically –40 dBc and second-harmonic levels are typically –30 dBc.

Vectron International recently announced a new ultra-low-noise oven-controlled crystal oscillator (OCXO), the OX-045, claiming that the new source demonstrates industry-leading close-in phase noise for a 10-MHz OCXO, at –140 dBc/ Hz at 10 Hz offset and a –163 dBc/ Hz noise floor.

Z-Communications released a new low-noise VCO, the SMV1205C-LF, which spans 1185 to 1225 MHz and features phase noise of -103 dBc/Hz at 10 kHz offset. This little VCO is housed in a sub-L package, which measures 0.3 x 0.3 x 0.08 in. The company also recently released a 13.5-GHz fixed-frequency synthesizer, the SFS13500Z-LF, with typical phase noise of –80 dBc/Hz at 10 kHz offset with typical reference spur suppression of –65 dBc.

Synergy Microwave Corp. has announced the FCTS-series of phase-locked clock translator frequency sources (Fig. 1). The company reports that they exhibit better phase noise than crystal-based reference oscillators that are multiplied to higher frequencies. These new sources have phase noise performance of –150 dBc/Hz at a 10 kHz offset from a fundamental frequency of 1000 MHz. Mini-Circuits offers extensive lines of surface-mount VCOs, including the 0.5 x 0.5 in. model ROS-2082-119+ with low –118 dBc/Hz phase noise offset 100 kHz from the carrier. It tunes from 1700 to 2082 MHz.

Moving away from the miniature and looking at the modular, there are a number of new synthesizer products available to help improve RF and microwave testing, including the 5003 and 5005 dual-synthesizer modules from Valon Technology. These are self-contained, board-level signal sources based on Flash memory. Designers can program the units in a lab, for instance, to implement a complete RF receiver or transmitter on the bench. Because they are dualsynthesizer modules, these products can also be used as a frequency translator (by adding two mixers and a filter).

Also working at the module level, Phase Matrix recently introduced its latest QuickSyn frequency synthesizer that operates from 200 MHz to 20 GHz with phase noise of –110 dBc/Hz offset 10 kHz from the carrier. Designed to be dramatically smaller than a traditional rack-mount unit, the Phase Matrix device weighs in at 2.1 lbs. and measures 5 x 7 x 1 in. Alexander Chenakin, Ph.D., Vice President, Signal Sources, Phase Matrix, Inc. says that this version delivers the best phase noise/ switching speed performance for its device class. He explains that they use their patented phase-refining technology, which removes the divider from the PLL feedback path. This inverts the PLL division ratio, applying multiplication within the PLL, which improves phase-noise and spurious characteristics. Since removing the divider affects the frequency resolution, Phase Matrix uses direct digital synthesis (DDS) to achieve sub-1-Hz steps.

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