Review of Agilent E4440A

Roger Allan | Electronic Design

Advanced performance in sophisticated test and measurement equipment generally comes at the price of complexity of use. Adding more features and capabilities to an instrument and its front panel often requires that users take a lot of time to just figure out how to get the most out of that instrument. But a new milestone in both performance and ease of use has been achieved with the E4440A spectrum analyzer from Agilent Technologies, the first in the company's Performance Series Analyzer (PSA) family (Fig. 1).

Digital technology was used to give the instrument what the company claims is "unparalleled performance, enhanced flexibility, and modern connectivity." Because of its flexibility, the E4440A can be employed by a wide variety of designers, from novice to expert, across a number of disciplines like aerospace, communications, R&D, and manufacturing, for both general and highly specialized signal-analysis purposes. The instrument's combination of speed and performance lets designers characterize signals that they couldn't even "see" before. And, it makes possible measurements that are much quicker and more accurate.

Speed, accuracy, dynamic range, resolution, and detection capabilities have all been optimized to what Agilent says are "industry firsts." Without using conventional LC and crystal filters that can slow signals down, the PSA platform doubles the speed of many measurements, permitting faster spur searches than other commercially available spectrum analyzers.

For example, the 30-Hz to 26.5-GHz analyzer features wide-ranging sweep speeds. It can measure very slow sweep speeds to capture intermittent signals. Zero-band sweep speeds range from 1 µs to 6000 seconds. For spans greater than 10 Hz, sweep speeds range from 2 ms to 2000 seconds. Users can trigger the sweeps with video, free-run, line, and external signals, and the trigger can be delayed up to 500 ms.

Using digital signal processing, the instrument offers 0.35-dB absolute-amplitude accuracy versus the typical 1.5 dB of other instruments, and an impressive 0.2-dB linearity over a 100-dB range. It removes log-fidelity errors almost entirely (0.2 dB total), significantly reduces bandwidth-switching er-rors (0.05 dB), and completely eliminates IF gain errors (0 dB). Therefore, users can operate effectively with closer tolerances and shrink guard bands.

In addition, the E4440A features a distortion-free dynamic range of 113 dB. This is critical for making adjacent-channel pow-er measurements in the cellular telecommunications industry.

The E4440A provides optimized phase-noise capability. Designers can set the analyzer to improve phase noise in the close-in mode to less than 30 kHz. This is particularly useful for identifying low-level signals otherwise hidden under phase-noise skirts. Or, users can choose the auto mode, which is more than 30 kHz, to let the instrument select the phase-noise setting at an optimal speed.

Another important parameter for the E4440A is flexibility, as this allows customizable measurements for both novice and experienced users. Measurements may be fine-tuned with 160 resolution bandwidth settings. Also, users can maximize the usable dynamic range with a 2-dB step attenuator and balance close-in or far-out phase noise (Fig. 2). Note that the industry standard for step attenuation is 10 dB.

Broad and easy connectivity are featured by the E4440A, minimizing the time wasted when getting data into and out of the instrument. The E4440A enables screen and data capture with popular Microsoft applications, and it can connect to LANs for data transfers. Plug-and-play drivers are available for Agilent VEE and other popular test-automation software, in-cluding LabView and LabWindows. Furthermore, the instrument supports popular PCL3 and PCL5 printers using a parallel port.

Unlike the previous-generation Agilent spectrum analyzers based on a 68000 CISC processor, the PSA line of analyzers is based on a RISC processor. By extensive use of digital and DSP technology, Agilent's designers were able to shrink the analyzer's eight internal pc boards from previous-generation units to just one.

A key element in the instrument's performance capability is a 3-GHz preamplifier that improves the digital average-noise level (DANL) to an impressive −153 dBm over a 10-MHz to 3-GHz frequency range, a figure that will be improved to −167 dBm. The preamplifier first feeds its signals to a sophisticated voltage-controlled oscillator (VCO) that actually acts as two VCOs, and then onto a 14-bit, 30-Msample/s analog-to-digital converter (Fig. 3).