Modular frequency synthesizers are useful in numerous applications requiring a stable frequency source. Compact units are available from a number of suppliers, with one relative newcomer, HGC Microwave, offering a miniature synthesizer module with broad bandwidth of 29 to 3840 MHz and excellent spectral purity in a housing measuring only 5.39 x 6.48 x 0.67 in. with SMA female connectors.

The model KY3840A frequency synthesizer module, with its flexible programming capabilities, is ideal for architectures requiring a stable embedded source. It tunes across its frequency range in fine steps, providing 1-Hz tuning resolution. It is designed to operate from a single +15-VDC supply, with nominal current consumption of 480 mA. The synthesizer, with typical output power of +10 dBm, maintains that level with output level flatness of typically dB from 29.0 to 1919.999999 MHz.

The synthesizer includes a lownoise temperature-compensated crystal oscillator (TCXO) reference source with ppm long-term stability over case temperatures from -30 to +60C, and 2 ppm stability for case temperatures from +60 to +70C. The internal reference frequency is adjustable to compensate for the effects of aging over a typical period of 15 years. The frequency synthesizer provides a 10-MHz, +3-dBm reference signal at an SMA connector for use with other test equipment. To help monitor operating conditions, the synthesizer includes an internal temperature monitor. In addition to the internal reference, the KY3840A works with an external reference source at frequencies of 2, 4, 5, 8, 10, or 16 MHz when stability greater than that of the internal oscillator is needed.

In terms of spectral purity, the model KY3840A frequency synthesizer module exhibits nonharmonic spurious content of -70 dBc or better, and typically -80 dBc. Second harmonics are typically better than -50 dBc at 50 MHz, typically -36 dBc at 500 MHz, and typically -29 dBc at 3840 MHz. The single-sideband (SSB) phase noise is -110 dBc/Hz offset 10 kHz from a 1-GHz carrier and -130 dBc/ Hz offset 10 kHz from a 100- MHz carrier.

The synthesizer provides the switching speed expected of a phase-locked-loop (PLL) source, with maximum tuning speed of 6 ms. Although not the microsecond speed of a direct-analog or direct-digital-synthesizer (DDS) design, this is adequate for a wide range of applications, including in automatic-test-equipment (ATE) and communications systems. In support of tuning flexibility, the synthesizer incorporates RS-232 and four-wire serial control interfaces for connection to an external personal computer (PC), and is shipped with Windows-based software for remote control with a PC. The KY3840A weighs just 1.4 lbs. HGC Microwave, Gaithersburg, MD; (301) 977-8484, e-mail: support@hgcmicrowave.com, Internet: www.hgcmicrowave.com.

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