H
HP 8901A Modulation Analyzer
150 kHz to 1300 MHz
Product Overview
Outstanding signal characterization
Measurements*
Frequency
Range: 150 kHz to 1300 MHz
Resolution:
10 Hz below 1000 MHz,
100 Hz above 1000 MHz
Input Level:
Automatic Mode: −20 dBm to +30 dBm
Manual Mode: Typically −60 dBm to +30 dBm
Power
Display: Peak envelope power
Range: 1 milliwatt to 1 watt
Accuracy: Typically ±1.5 dB
Input Power Protection:
>25 watts
Modulation
Frequency Modulation
Rates: 20 Hz to 200 kHz
Deviations: to 400 kHz
Accuracy: ±1% of reading ±1 digit for rates 30 Hz to 100 kHz
Amplitude Modulation
Rates: 20 Hz to 100 kHz
Depths: to 99%
Accuracy: ±1% of reading ±1 digit for rates 50 Hz to 50 kHz and depths >5%
Applications
Mobile Radio
The HP 8901A Modulation Analyzer combines all the capabilities necessary for making accurate transmitter measurements. It can be used in making all the tests listed below. It can also be used to test modules and subassemblies from either the transmitter or receiver. For reliability, input power protection reduces the chance of accidentally damaging the modulation analyzer by connecting it directly to a high power transmitter.
•Carrier power
•Carrier frequency and stability
•AM depth
•FM deviation
•Hum and noise
•Incidental AM or FM
•Modulation limiting
-Instantaneous
-Steady state
•Audio frequency response
Maintenance and Metrology
Accurately measuring modulation has long been a problem for metrology laboratories. The HP 8901A Modulation Analyzer
helps solve this problem two ways. First, it provides an extremely accurate method of measuring AM depth and FM deviation, and
it recovers the modulation with little degradation for making measurements such as modulation distortion. Second, the optional calibrators provide a precise modulation source for calibration. There are many metrology and maintenance uses for the modulation analyzer. They include:
•Signal generator calibration
•Modulation calibration standard
•VCO and VCXO characterization
Phase Modulation
Rates: 200 Hz to 20 kHz
Deviations: to 400 radians
Accuracy: ±3% of reading ±1 digit
*All parameters describe performance in automatic operation or properly set manual conditions. Specifications describe the instrument’s warranted performance. Supplemental characteristics (shown in italics) are intended to provide information useful in applying the instrument by giving typical, but non-warranted, performance parameters.
Applications, cont. |
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Features |
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Research and |
Complete Signal |
High Performance |
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Development |
Characterization |
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The accuracy and versatility of the modulation analyzer make it a very useful laboratory instrument for characterizing a wide variety of devices and assemblies. When used with a modulated signal source the modulation analyzer can make stimulusresponse measurements for direct measurement of a device’s effects on such signals. Because of its wide frequency range, it can measure the performance
of both RF and IF assemblies. Characterizing modulated sources for sensitivity, distortion, and incidentals, and measuring the noise performance of local oscillators is also possible.
•Mixer and Amplifier compression
•Local oscillator residual FM
•Modulator characterization
•Incidental AM or FM
•RF and IF characterization
The HP 8901A Modulation Analyzer brings together in one instrument several RF signal measurement capabilities. It is more than just a high quality modulation meter. It accurately measures carrier frequency and peak input power in addition to completely characterizing modulation. This unique combination of capabilities makes the HP 8901A Modulation Analyzer an extremely powerful tool for analyzing signals. In normal use it elimi-
nates the need to frequently connect and disconnect several instruments, such as counters and power meters. The modulation analyzer is fully programmable and can be used as part of an automatic system to make all these measurements under remote control.
Single Key Measurements
The HP 8901A Modulation Analyzer features easy to use controls. In automatic operation, all major functions are selected by pushing a single key. No manual tuning or range selection is needed. The modulation analyzer automatically tunes to the input signal, adjusts for proper signal level, selects the appropriate measurement range, makes the measurement, and displays the result.
For certain measurements manual operation may be more desirable. When selecting a specific signal in the presence of others or for special applications, the operator can easily use the modulation analyzer’s keyboard to set any or all measurement parameters. Functions not selected manually remain in automatic mode. This greatly increases the modulation analyzer’s versatility.
The HP 8901A Modulation Analyzer offers a significant advancement in modulation measurements. Modulation depth and deviation are measured with unprecedented 1 percent accuracy. To complement this capability, optional calibrators with 0.1 percent depth or deviation accuracy can be included in the analyzer.
A significant improvement has also been made in the area of residual noise. The extremely low internal noise of the modulation analyzer makes possible residual AM and FM measurements even on very stable signals. Accurate measurement of signals with small incidental AM
or FM modulation are now easily performed. Residual AM in a 50 Hz to 3 kHz bandwidth is <0.02 percent, and residual FM in the same bandwidth is <8 Hz at 1300 MHz decreasing to <1 Hz below
100 MHz.
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The HP 8901A Modulation Analyzer
is a complete measurement system for accurately characterizing signals in the 150 kHz to 1300 MHz frequency range.
It can make more than just a single form of measurement; it combines the capabilities of three separate instruments. The HP 8901A Modulation Analyzer has the capability of a frequency counter for measuring carrier frequency. It can measure RF peak power with typical measurement accuracy of ±1.5 dB. It can also accurately measure modulation and recover the modulating signal. This allows the user to make those measurements most commonly needed to totally characterize a signal. The modulation analyzer can measure a signal’s frequency, frequency drift, peak power level, AM, FM, or φM, and AM and FM noise components.
It recovers the modulating signal with very low added distortion for audio analysis.
Besides combining several measurements in one instrument the HP 8901A Modulation Analyzer makes a second contribution to signal analysis—extremely precise modulation measurements. Its ability to make highly precise depth and deviation measurements coupled with very low internal noise enables the analyzer to characterize very accurate signal sources. Modulation depth or deviation accuracy is generally <1 percent of reading. Residual noise in a 50 Hz to 3 kHz bandwidth is 0.02 percent for AM and <8 Hz for FM at 1300 MHz carrier frequencies, decreasing to <1 Hz below 100 MHz.
The modulation analyzer is fully automatic and all major measurements can be made by pushing a single key. The modulation analyzer’s large digital display shows measurement results with excellent resolution and is easy to read. All measurements can be easily controlled remotely and data transferred via the Hewlett-Packard Interface
Bus (HP-IB).*
Frequency Measurements
In automatic operation the
HP 8901A Modulation Analyzer has the performance of a high quality 150 kHz to 1300 MHz frequency counter. Resolution is 10 Hz below 1000 MHz and 100 Hz above 1000 MHz. Sensitivity is −25 dBm (12 mVrms) below 650 MHz and −20 dBm (22 mVrms) above 650 MHz.
Besides normal frequency measurement capabilities the analyzer’s counter has several additional capabilities. Like most frequency counters it will measure signals over a wide dynamic range, >50 dB (22 mVrms to
7 Vrms), and is protected from damage for signals up to 35 Vrms. Unlike many frequency counters, however, it automatically adjusts itself as the input level changes. There is no need to manually set or adjust any input attenuator. Because the modulation analyzer is usually used to measure modulated signals, its frequency counter accurately measures signals with significant levels
of AM modulation.
The modulation analyzer uses an indirect technique for measuring RF frequencies. Instead of counting directly, the input signal is down-converted to an interme diate frequency (IF) using a mixer and a local oscillator (LO). By counting the frequency of both the IF and LO and calculating their difference, the modulation analyzer can determine the frequency of the input signal.
In automatic operation the analyzer automatically tunes to the largest input signal and measures its frequency.
In manual operation the user determines the frequency to which the modulation analyzer tunes.
When more than one signal is present it is thus normally possible to select which signal is counted. Entering the approximate frequency on the keyboard causes the IF filter to eliminate all but very close interfering signals. This allows the modulation analyzer to selectively count signals other than the largest. Also, because of the large IF gain of the modulation analyzer, it is possible to measure very low-level signals. In manual operation the modulation analyzer has sensitivity of 0.22 mVrms, and dynamic range
of >90 dB (0.22 mVrms to 7 Vrms).
*HP-IB is Hewlett-Packard's implementation of IEEE standard 488.
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