Spectrum analysis is an essential measurement capability at RF and microwave frequencies, almost having the weight of a voltmeter at lower frequencies. If anything, however, it is the weight that has been left out of the latest line of portable spectrum analyzers from Anritsu Co. (www.anritsu.com). The company's "B" line of models MS2721B, MS2723B, and MS2724B Spectrum Master™ handheld analyzers are high-performance instruments with respective frequency ranges of 9 kHz to 7.1 GHz, 9 kHz to 13 GHz, and 9 kHz to 20 GHz. But even the highest-frequency mode, with built-in preamplifier and AM/FM/SSB demodulators, weighs less than 8 lbs. (3.6 kg).
The new Spectrum Master handheld instruments build on a product line that previously included economy and lower-frequency models operating to 7.1 GHz, such as the model MS2711B with frequency range of 100 kHz to 3 GHz (and higher noise levels than the new units) and the model MS2717A economy instrument with range of 100 kHz to 7.1 GHz. The new analyzers (Fig. 1) feature lower noise levels than the earlier models, with a low-frequency extension that supports near-audio testing and a high-frequency ceiling that permits capture of the largest majority of microwave signals.
The high-performance Spectrum Master instruments feature familiar packaging first introduced in Anritsu's Site Master line of wireless on-site and base-station portable testers (see sidebar). The front of each analyzer sports a large, 8-in.-diagonal, super VGA (SVGA) full-color liquid-crystal-display (LCD) screen that shows a signal under test along with key instrument settings on the left, such as resolution bandwidth filter, video bandwidth filter, sweep speed, and input attenuation. The right-hand side of the screen provides control options according to the selected function button, as start and stop frequency for the frequency controls. To the right of the screen are cursor controls and widely spaced numerical keypad buttons for direct data entry; a second level of functionality lies beneath these keys for simplified Spectrum Master control from the front panel.
The MS2724B (Fig. 2), with its frequency range of 9 kHz to 20 GHz, is well equipped for most commercial wireless standards and even broad-band military radar testing. As with its lower-frequency siblings, it offers digital resolution-bandwidth filters from 1 Hz to 3 MHz that allow close scrutiny of complex signals without sacrificing sweep speeds for narrower filter bandwidths. Video bandwidth filters can be selected from 1 Hz to 3 MHz in a 1-3 sequence. The analyzers can tune to the resolution of these filters, within 1 Hz, and can command measurement spans as narrow as 10 Hz to a wide as the full bandwidth of each instrument, or 20 GHz in the case of the MS2724B. All three analyzers also perform zerospan measurements, useful when examining wideband modulated signals. Sweep times are as short as 100 ms for full sweeps and 10 µs for zero-span measurements. The new analyzers perform peak, negative, sample, root mean-square (RMS), and quasi-peak detection to support measurements on a wide range of CW and burst or pulsed signals. All three Spectrum Master instruments feature a quasi-peak detector and CISPR bandwidths for EMC precompliance testing.
The amplitude measurement range of the Spectrum Masters is dependent upon the highest-level and lowest-levels signals that can be measured. The lowest level is defined by the displayed average noise level (DANL). In the 20-GHz model MS2724B, the DANL with a 1-Hz resolution-bandwidth filter is –139 dBm from 10 MHz to 4 GHz, –136 dBm from 4 to 10 GHz, –130 dBm from 10 to 13 GHz, and –136 dB from 13 to 20 GHz. Since all three Spectrum Masters include a built-in low-noise preamplifier, the DANL can be extended over the range of this preamplifier (100 kHz to 4 GHz), to –159 dBm from 10 MHz to 1 GHz, –156 dBm from 1 to 3 GHz, and –154 dBm from 3 to 4 GHz. At the other end of the measurement range, the Spectrum Masters are designed to handle input signals as large as 1 W (+30 dBm) and provide typical third-order-intercept (TOI) performance (with the preamplifier off) of +8 dBm from 0.5 to 2 GHz, +10 dBm from 2 to 6 GHz, and +12 dBm from 6 to 20 GHz. To protect the front end from overload, the analyzers are equipped with a broadband microwave attenuator that can be adjusted from 0 to 65 dB attenuation in 5-dB steps.
The analyzers are designed around a clean, synthesized local oscillator (LO) with excellent stability. The single-sideband (SSB) phase noise of the internal LO is –95 dBc/Hz offset 10 kHz for carriers through 20 GHz, –97 dBc/Hz offset 100 kHz for carriers through 20 GHz, –105 dBc/Hz offset 1 MHz from carriers through 20 GHz, and –102 dBc/Hz offset 10 MHz from carriers through 20 GHz (essentially the noise floor). Residual spurious content is –85 dBc or better at frequencies above 13 GHz, and better than –90 dBc at frequencies below 13 GHz.
As with their lower-frequency Spectrum Master counterparts, these new analyzers load generous marker functions (as many as 6 markers can be used, with each having a delta function for effectively 12 total on-screen markers), limit lines, and automatic test functions (or what the company refers to as "Smart Measurements"). These automatic measurement functions include tests for occupied bandwidth, channel power, carrier-to-interference (C/I) ratio, field strength, and adjacent-channel power ratio (ACPR). As many as three traces (A, B, and C) can be shown on the screen at one time using a trace overlay function; trace storage is dictated by the amount of memory in an installed Compact Flash (CF) memory card, or about 13,000 traces and more than 10,000 instrument setups for a 256-MB CF card.
Each Spectrum Master provides versatile display capabilities to better understand and interpret captured data. The spectrogram display, for example, was used to examine the cellular range of frequencies from 850 to 910 MHz with color-coded power levels helping to simplify the analysis (Fig. 3).
The new Spectrum Masters are available with a variety of optional features, such as a tracking generator that supports scalar-network-analyzer (SNA) type swept-frequency measurements. The optional tracking generator provides calibrated signals from 450 kHz to 7.1 GHz with a power range of –40 to 0 dBm in 0.1-dB steps. In addition, an option adds accurate power-measurement capability using a model PSN50 power-meter sensor that connects to the instrument via the USB; a Channel Scanner function simplifies analysis of wireless-standard-based channels, such as in GSM and UMTS systems; a built-in Global Positioning System (GPS) receiver provides accurate position indication; and WCDMA/HSDPA RF measurement capability detects and displays advanced wireless-communications signals. For example, the Channel Scan display was used to analyze GSM 900 signals from 935.0 to 936.8 MHz with each channel clearly shown in terms of frequency and power levels (Fig. 4). The GPS option was switched on when analyzing a UMTS band 1 downlink to provide location coding for measured signals (Fig. 5).
To add versatility to their portability, the MS2721B, MS2723B, and MS2724B Spectrum Masters equip an operator with a host of languages to choose from, including English, Spanish, Italian, French, German, Japanese, Korean, and Chinese. The analyzers are equipped with Type N female connectors for input test signals and for an optional tracking generator, a BNC jack for an optional GPS antenna, a RJ45 Ethernet connector for linking to a local-area network (LAN), and Universal Serial Bus (2.0) connectors for connecting to flash drives, the PSN50 power meter, and to a PC. The instruments are shipped with Master Software Tools, an MS Windows-based collection of software programs that allows a Spectrum Master to link to a personal computer (PC) and use the PC for control and data analysis.
The portable, handheld instruments are built to MIL-PRF-28800F Class 2 requirements and are rugged enough to withstand the most demanding infield applications. They are ideal for spectrum monitoring, security and intelligence needs, RF/microwave measurements, or cellular signal measurements. The analyzers are shipped with rechargeable batteries that provide more than two hours of operation per charge. P&A: $20,950 (MS2724B), $17,950 (MS2723B), and $13,950 (MS2721B); 8 wks.
Anritsu Co., Microwave Measurements Div., 490 Jarvis Dr., Morgan Hill, CA 950372809; (800) ANRITSU, (408) 7782000, Internet: www.us.anritsu.com