Frequency synthesizers generate stable RF/microwave signals for a variety of applications, from commercial communications to military systems. Standard models are available from a number of suppliers, but some jobs call for a special set of requirements. When a set of custom frequency synthesizer specifications must be met, Mini-Circuits offers an array of choices from fixed-frequency and narrowband units to broadband designs from 167 to 6010 MHz.

The custom frequency synthesizers are available with a wide range of frequency plans, including fixed-frequency (with internal microcontrollers), dual-band, tunable narrowband, tunable mediumband, tunable wideband, tunable verywideband (with as much as six octaves of coverage), and tunable fast-settling-time frequency synthesizers. Each design starts by working out a set of requirements with a customer, including reliability issues and program milestones. Designs are simulated by means of the latest computer-aided-engineering (CAE) software tools, and those simulation results are shared with the customer.

Trade-offs and options are reviewed until a customer is comfortable with these pre-prototyping specifications.

Once approved, a synthesizer design is prototyped and 100-percent tested over the full operating temperature range. Those test results are then shared with the customer and, only when a customer is fully satisfied with the prototype results will a design be released for an engineering production run. The custom frequency synthesizes are then manufactured with advanced computer-controlled automated assembly equipment according to some of the most rigorous quality standards in the industry: ISO 9001:2000, ISO 14001:2004, and aerospace standard AS 9100B. Every custom frequency synthesizer is 10-percent tested during production, using over 40 electrical tests to verify that each unit meets or exceeds a customer's specifications.

As examples of the company's workmanship several different types of frequency synthesizers have been designed and produced for applications such as cable-television (CATV), cellular base stations, WiMAX, Global Positioning System (GPS), and military electronic systems. In the narrowband category, a 2932-to-3132-MHz frequency synthesizer was developed for 3.5-GHz WiMAX applications. It is designed for a 52-MHz reference frequency and tunes across its bandwidth with 250-kHz step size. The synthesizer delivers flat +3-dBm output power across its 200-MHz bandwidth with typically -20 dBc harmonics and -80 dBc spurious content. With settling time of typically 10 ms, the low-noise frequency synthesizer exhibits single-sideband (SSB) phase noise of-82 dBc/Hz offset 100 Hz from the carrier, -88 dBc/Hz offset 1 kHz from the carrier, and -95 dBc/Hz offset 10 kHz from the carrier.

In the very-wideband category, the model WSN frequency synthesizer was developed for octave-band coverage from 1110 to 2220 MHz. It operates with a 20-MHz reference frequency and tunes in 10-MHz steps. The very-wideband frequency synthesizer delivers +8-dBm output power, with -30 dBc typical harmonics, -98 dBc reference spurious content, and -75 dBc comparison spurious content. The settling time is typically 15 microseconds and the SSB phase noise is typically -89 dBc/Hz offset 100 Hz from the carrier, -101 dBc/Hz offset 1 kHz from the carrier, and -102 dBc/Hz offset 10 kHz from the carrier. It is supplied in a low-profile housing measuring 1.75 x 1.25 x 0.22 in. (44.45 x 31.75 x 5.99 mm) (Fig. 1).

For medium-band tuning, frequency synthesizers in the DSN series offer ranges of 10 to 30 percent of the center frequency, such as units operating from 1690 to 2310 MHz and 2700 to 3500 MHz. The two frequency synthesizers are both designed for a 10-MHz reference and tune with step sizes of 250 kHz and 1 MHz, respectively. They have been designed for different phasenoise characteristics, with the lowerfrequency unit providing phase noise that is outstanding far from the carrier while the higher-frequency synthesizer shaves phase noise close to the carrier. The 1690-to-2310-MHz frequency synthesizer exhibits harmonic content of -25 dBc with reference spurious of -100 dBc and comparison spurious of -95 dBc. The SSB phase noise is -58 dBc/Hz offset 100 Hz from the carrier, -68 dBc/Hz offset 1 kHz, -97 dBc/Hz offset 10 kHz, and -121 dBc/Hz offset 100 kHz from the carrier. The 2700-to- 3500-MHz medium-band synthesizer has typical harmonics of -25 dBc, with reference spurious of -92 dBc/Hz and comparison spurious of -85 dBc/Hz. The SSB phase noise is -83 dBc/Hz offset 100 Hz from the carrier, -84 dBc/Hz offset 1 kHz, and -105 dBc/Hz offset 100 kHz from the carrier. The synthesizer features settling time of 0.22 ms.

When faster switching speed is required, one of the firm's RSN series frequency synthesizers can be designed for a variety of requirements. For example, an RSN frequency synthesizer developed for GSM applications from 1543 to 1618 MHz tunes in 200-kHz steps with frequency settling time of typically 25 microseconds. It provides +4.5 dBm typical output power with -25 dBc harmonics. The SSB phase noise is -106 dBc/Hz offset 100 kHz from the carrier. It is supplied in a tiny package measuring 0.91 x 0.91 x 0.252 in. (23.11 x 23.11 x 6.40 mm) (Fig. 2).

More information on Mini-Circuits' custom frequency synthesizers can be found by downloading a free eightpage catalog in PDF form at the company's web site. Mini-Circuits, P. O. Box 350166, Brooklyn, NY 11235-0003; (718) 934-4500, FAX: (718) 332-4661, Internet: www.minicircuits.com.