Frequency Synthesizers Fit In Rugged Systems

Aug. 13, 2008
These compact, lightweight, hermetic frequency synthesizers feature fast switching speed and outstanding spectral purity for bands within the total range of 1 to 23 GHz.

Military and some commercial systems can benefit from a frequency synthesizer capable of harsh treatment. The Ruggedized Series (RS) of frequency synthesizers from Elcom Technologies are designed for the harsh realm of many military applications at frequencies to 23 GHz. In addition, they are small and sacrifice little in terms of spectral purity compared to much larger frequency synthesizers. Built for altitudes to 60,000 feet and capable of maintaining stable outputs even at shock and vibration levels beyond 6 g's, these fast-switching frequency synthesizers are ideal for airborne applications as well as a wide range of commercial and military systems requiring broadband signal generation.

Elcom Technologies is a wellestablished supplier of rack-mount frequency synthesizers for test and systems applications including the UFS series of frequency synthesizers that are based on direct-analog techniques combined with direct-digital-synthesis (DDS) technology to achieve frequency switching speed of 200 ns from 300 MHz to 18 GHz. The firm also offers the IBS series of frequency synthesizers based on phase-lock-loop (PLL) indirect frequency synthesis, with much more moderate frequency switching speeds from 0.05 to 18.0 GHz. By leveraging this frequency synthesizer expertise, the company has developed the compact but rugged RS line of frequency synthesizers available in octave bands from 1 to 23 GHz. The RS sources pack the basic performance of the company's larger laboratory sources into compact housings capable of withstanding wide ranges of temperature, shock, and vibration without adverse effects on performance.

The RS frequency synthesizers include several models, including the RS-1000 (Fig. 1) units, with 25-percent bandwidths for center frequencies from 1 to 23 GHz. The RS-1000 frequency synthesizers tune with step sizes of 1 MHz at S-band frequencies, 2.5 MHz at C-band frequencies, and 5 MHz at Ku-band frequencies. They deliver +14 dBm output power with outputpower flatness within +/- 2 dB. These frequency synthesizers, which provide frequency and amplitude switching speeds in excess of 50 microseconds (to settle within 4 deg. of a new frequency), are supplied in rugged hermetic housings measuring just 3 x 3 x 1 in. For a 10-GHz carrier, the RS-1000 frequency synthesizers exhibit singlesideband (SSB) phase noise of -76 dBc/ Hz offset 100 Hz from the carrier, -99 dBc/Hz offset 1 kHz from the carrier, -110 dBc/Hz offset 10 kHz from the carrier, -110 dBc/Hz offset 100 kHz from the carrier, and -145 dBc/Hz offset 10 MHz from the carrier. The spurious content is less than -77 dBc while harmonics are less than 40 dBc. The RS-1000 synthesizers handle operating temperatures from -54 to +85C without degradation in performance, and are designed to withstand shock and vibration to 6 g's as well as altitudes to 60,000 ft. They operate on power supplies of 100 mA at +15 VDC and 1300 mA at +6.5 VDC.

Additional ruggedized frequency synthesizer lines include the RS-1010, with bandwidths as wide as 2 percent from 8.8 to 9.0 GHz, the RS-1094, with octave bandwidth and minimum step size of 1 Hz from 1.8 to 3.6 GHz, and the RS-WMFS with octave-bandwidth coverage from 1 to 23 GHz. The smallest member of the group, the RS-1003 frequency synthesizers, measure 2.25 x 2.25 x 0.625 in. but provide as much as 20 percent bandwidth at center frequencies from 6 to 18 GHz. Tuning with step sizes from 10 to 100 MHz, the hermetic-packaged RS-1003 frequency synthesizers are shock and vibration tested at equal or higher levels than those endured by the RS-1000 frequency synthesizers, and are capable of handling altitudes to 70,000 ft.

The WMFS series frequency synthesizers include typical frequency coverage of 3 to 5 GHz, 6 to 10 GHz, 8 to 12 GHz, and 12 to 18 GHz, with output power ranging from +10 to +14 dBm. Frequency switching in steps of 1 Hz, 1 kHz, 100 kHz, or 1 MHz can be accomplished in less than 1 ms, with switching speed for WMFS frequency synthesizers as fast as 250 ms as an option. The WMFS frequency synthesizers promise outstanding spectral purity, with harmonics levels of -60 dBc or better, spurious of -60 dBc or better, and low phase noise. The maximum phase noise at 10 GHz is -60 dBc/Hz offset 10 and 100 Hz from the carrier, -80 dBc/Hz offset 1 and 10 kHz from the carrier, -95 dBc/Hz offset 100 kHz from the carrier, -119 dBc/ Hz offset 1 MHz from the carrier, and a noise floor of -140 dBc/Hz offset 10 MHz from the carrier. WMFS sources measure 5 x 5 x 1 in. in a hermetic housing per MIL-STD-202F (Fig. 2) with maximum power consumption of 10 W.

The RS line of frequency synthesizers are subjected to a barrage of environmental tests by means of Elcom's in-house Highly Accelerated Life Testing (HALT) and Highly Accelerated Stress Screening (HASS) systems with their multi-axis vibration capabilities and temperature control from -100 to +200C. These systems can apply forces in excess of 50 G's to simulate the harshest operating environments for the company's ruggedized lines of frequency synthesizers. The RS frequency synthesizers are suitable for demanding commercial and military applications. Elcom Technologies, 11 Volvo Dr., Rockleigh, NJ 07647; (201) 767-8030, Fax: (201) 767-1326, Internet:

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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