Agilent 81110A Technical Specifications

Agilent 11715A
AM/FM Test Source

Technical Specifications

Description

The Agilent Technologies Model 11715A AM/FM
Test Source is a tunable voltage-controlled oscilla­tor combined with modulators to form a source of
calibration-quality amplitude and frequency modu­lated signals. It is designed primarily to verify the
demodulation performance of the Agilent 8901A
Modulation Analyzer, but its excellent signal quali­ties can benefit many other demanding applications.

The front panel provides four separate RF outputs
with both fixed and variable carrier frequencies
and an input for a modulation source. The fixed
output is a crystal-derived 560 MHz carrier with
low residual FM. The other three output ports
cover 11 to 13.5 MHz, 88 to 108 MHz, and 352 to
432 MHz. Frequency modulation is possible on all
three ranges, and amplitude modulation is avail­able on the 11 to 13.5 MHz range.

Frequency Modulation

Maximum deviation is greater than 400 kHz peak
with distortion less than 0.025%. As a function of
modulating frequency, deviation is constant within
±0.1% up to 100 kHz rates and typically within
±2.5% up to 10 MHz rates due to the wideband
dc-coupled design. Two other critical parameters,
residual FM and incidental AM, are both mini­mized in the design.

Amplitude Modulation

AM up to 99% is available on the 11 to 13.5 MHz
range with excellent flatness. Even at 95% AM, dis­tortion is less than 0.1% for 20 Hz to 100 kHz mod­ulation rates. As a function of modulating input
voltage, modulation depth linearity varies less than
±0.2% up to 99% AM. Residual AM is less than 0.01%
rms in a 50 Hz to 3 kHz post-detection bandwidth.

Superior AM & FM

Performance in

a Specialized

RF Source

2

Applications

General Use

Many other applications requiring wideband, low­distortion modulation can utilize the 11715A. For
example, precise test signals for the 88 to 108 MHz
commercial FM broadcast band can be generated
by combining the 11715A with a suitable stereo
modulator and an 8901A Modulation Analyzer.
Typical left-to-right channel separation is 60 dB,
and distortion and incidental AM are very low.
With the 8901A to monitor the level, frequency,
and modulation of the 11715A’s output, the
11715A performs as a highly accurate stereo test
generator.

8901A Tests

A primary application of the 11715A is to verify
and adjust the demodulation performance of the
8901A Modulation Analyzer. The 8901A is a preci­sion calibrated receiver designed to accurately
demodulate and measure amplitude, frequency, or
phase modulated RF carriers. 8901A demodulation
specifications include accuracy, flatness, band­width, range, distortion, residual noise, and inci­dental modulation. The AM and FM accuracy spec­ifications can be verified with a precise optional
built-in calibrator; however, the calibrator oper­ates on only one carrier frequency, at a fixed mod­ulation rate, and with a single AM depth or FM
deviation. The other specifications must be veri­fied with an RF source that has variable carrier
frequency and modulation parameters.

Although RF signal generators have calibrated
frequency, modulation, and output level character­istics, they are generally unsuited for 8901A tests
because the circuitry required to ensure calibra­tion can also degrade or restrict modulation para­meters such as flatness and linearity. For this rea­son, the 11715A contains no circuitry to compro­mise performance—no output leveling or control,
no frequency stabilization, and no modulation
metering or control. The resultant modulation
characteristics make the 11715A an ideal choice
for exacting tests and adjustments on the 8901A.