Atec Agilent-8901B User Manual
HP 8901B Modulation Analyzer
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Options 030/037
10 MHz - 1.3 GHz
Technical Specifications
Selective Power Measurements
Adjacent Channel Power
Measurements
The HP 8901B Modulation Analyzer’s easy-to-useselective power measurement option saves you time
and money, speeding adjacent-channel power testing
on your RF communications transmitters. These selective measurements meet the stringent CEPT standards for adjacent-channel power with superb accuracy: ±0.5 dB; dynamic range >115 dB; and selectivity
>90 dB. The HP 8901B also performs RF power, frequency, modulation and audio measurements, plus
selective RF power measurements, fully characterizing your transmitter in seconds.
Making an adjacent channel power measurement is
simple. You first select the appropriate filter
(12.5, 25 or 30 kHz channel spacing) and measure the
transmitter carrier power. Then, tune the analyzer to
any offset desired, and measure the channel power.
The analyzer displays the results in dBc (dB relative
to the carrier power).
To meet the CEPT noise-floor requirements at frequencies greater than 300 MHz, the HP 8901B requires an external local oscillator (LO) such as the
HP 8656B Synthesized Signal Generator. Selecting
an external LO with fine frequency resolution also
improves the analyzer’s tuning resolution, which can
be as coarse as 2 kHz at 1300 MHz. Using an
HP 8656B signal generator gives you 10 Hz resolution
up to 990 MHz. Dedicating a signal generator as the
external LO is not necessary. When not being used as
the LO, a built-in RF switch in the HP 8901B routes
the signal generator’s output to the rear panel of the
analyzer.
HP-IB: Not just IEEE-488, but the hardware
documentation and support that delivers the
shortest path to a measurement system.
Direct-Spectrum Carrier Noise
Measurements
The HP 8901B Modulation Analyzer, with a low noise
external LO, performs fast, accurate single- sideband
(SSB) carrier noise measurements to 1.3 GHz. To
make a carrier noise (AM noise and phase noise)
measurement, you select the noise filter
(2.5 kHz noise bandwidth), measure the source under test’s carrier power, tune the analyzer to the frequency offset desired (5 kHz to 1300 MHz) and measure the noise. The data is displayed in real time,
either as dBc in a 1 Hz bandwidth or as total power
in the 2.5 kHz filter bandwidth.
Direct-Spectrum Carrier Noise
Measurements (cont’d)
Phase noise usually dominates the carrier-noise
measurement at most offsets of interest, so
direct-spectrum noise measurements provide a convenient and simple way to measure phase noise of
many sources. This measurement technique is relatively insensitive to many common pitfalls encountered in making phase noise measurements. There is
no need to phase-lock signals. Testing can be fully
automated using an external controller. Most important, selective signal and noise measurements are
fast (five readings/second). The analyzer’s measurement accuracy is better than ±0.5 dB to –129 dBc/Hz,
typically better than ±1 dB to –140 dBc/Hz. The noise
floor is –150 dBc/Hz.
Many applications require spectral purity to be expressed as residual AM, FM or phase modulation.
With the HP 8901B’s convenient modulation capabilities you make these measurements with one keystroke, in a variety of common bandwidths.
To extend the measurement range to 26.5 GHz, add
the HP 11793A Microwave Converter and a low noise
microwave source, such as the HP 8673B Synthesized
Signal Generator. With this system you can test highperformance sources from 10 MHz to 26.5 GHz.
Block Diagram
The high-selectivity option for the HP 8901B Modulation Analyzer adds an RF switch, a buffer amplifier, variable gain IF amplifiers, narrowband filters
and a rms detector. To make selective power measurements, the analyzer mixes down the RF input signal using either the internal LO or an external LO.
The IF signal is buffered and sent through one of two
narrowband bandpass filters which provide over 90
dB of rejection. The signal is amplified by precision
IF amplifiers, filtered again and measured by the rms
detector. The IF amplifiers provide as much as 95 dB
of gain in 5 dB increments; the rms detector is used
over a 20 dB dynamic range.
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