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Instrument Evaluates Oscillator Performance

This compact, multifunction instrument evaluates oscillator and source noise, transients, tuning linearity, and output power from 10 MHz to 7 GHz.

Oscillator and synthesizer designers struggle to measure key performance parameters for their components, such as phase noise and tuning linearity. They often rely on large racks of single-function test gear, such as power meters and power supplies, to perform difficult measurements. But the E5052A signal source analyzer from Agilent Technologies (Santa Rosa, CA) should bring a sigh of relief to these designers because this all-in-one instrument can measure the performance characteristics of nearly every type of signal source from 10 MHz to 7 GHz over a wide range of offset frequencies.

The versatile E5052A Signal Source Analyzer was one of the outstanding products introduced at the recent Microwave Theory & Techniques Symposium (MTT-S) in Fort Worth, TX. The analyzer employs a proprietary cross-correlation measurement method, using two measurement channels with independent reference sources and performing analysis on the two-channel signals. If the two signals are correlated and vector summed, the vector (amplitude and phase) of the two signals will be emphasized. Cross-correlation can remove the limitation imposed by the noise floor of a reference source, allowing measurements of extremely low noise levels.

The E5052A performs from 1 to 10,000 correlations to lower the noise floor, enlisting the help of digital signal processing (DSP) to derive accurate frequency and amplitude information. As with averaging, the phase-noise sensitivity improves with the number of correlations: for example, 10 correlations yields a 5-dB improvement in the noise floor improvement, while 10,000 correlations provide a 20-dB improvement in the noise floor.

Normally, techniques like averaging and cross correlation add time to a measurement. But in the E5052A, a 100-MHz digital-to-analog converter (DAC) is used with a DSP-based stepped Fast Fourier Transform (FFT) to speed the calculations.

The instrument measures the spectral content for carrier signals of 400 MHz and greater at offset frequencies from 1 Hz to 40 MHz. For carrier signals below 400 MHz, the offset range is 1 Hz to 10 percent of the carrier frequency. The phase-noise sensitivity is typically ­164 dBc/Hz offset 40 MHz from a 7-GHz carrier and ­174.5 dBc/Hz offset 40 MHz from a 10-MHz carrier when putting + 5 dBm signal, and it can be extended as low as ­178 dBc/Hz with the cross-correlation technique (see table). The measurement accuracy is typically ±4 dB for offsets from 1 Hz to 1 kHz, ±2 dB for offsets from 1 kHz to 1 MHz, and typically ±3 dB for offsets greater than 1 MHz.

In addition to phase noise, the E5052A measures tuning linearity, output power, frequency, transients, and current consumed (see table). Its frequency range can be extended to 110 GHz by external downconverters. It offers improved capabilities compared to the company's existing source-measurement solution, the 4352S VCO/PLL Signal Test System, at a fraction of the cost and size. The E5052A includes a Windows-style operating interface, 10.7-in. thin-film-transistor (TFT) liquid-crystal-display (LCD) screen with touch-sensitive (touch-screen) surface, and programming via SCPI or Microsoft Visual Basic for Applications (VBA). Connectivity is via GPIB, USB, and Ethernet. P&A: From $75,000; 30 days. Agilent Technologies, Test and Measurement Organization, 5301 Stevens Creek Blvd., MS 54LAK, Santa Clara, CA 95052; (800) 829 4444 ext. 7799.

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