Agilent 71708A Microwave Source
Agilent 70428A Microwave Source Module
Data Sheet
Variable frequency source with lowest phase noise
2
The Agilent Technologies 71708A
microwave source provides signals
with exceptionally low phase and AM
noise performance from 2.4 to 26.4 GHz.
Phase noise specifications are
–113 dBc/Hz and –125 dBc/Hz at
1 kHz and 10 kHz offsets from a
10.2 GHz carrier. AM noise is as low
as –150 dBc/Hz. Thus, the 71708A is
an ideal source for testing microwave
receivers, verifying noise floors of
phase noise measurement systems, or
substituting for the local oscillator in
radar systems.
The 71708A consists of a
4
/8 width
70428A microwave source module
and an 70004A color display/mainframe.
This system combines:
• Low phase noise
• Low AM noise
• Output frequency range from
2.4 to 26.4 GHz
• 600 MHz frequency resolution
• Optional 0.1 Hz frequency resolution
• Output power up to +16 dBm
Modular Measurement System (MMS)
building block
The user interface of the 71708A is
built into the firmware of the 70428A
microwave source module. This
allows you to easily integrate the
70428A into existing MMS systems
with multiple instruments. Through
the MMS user interface, you have
complete control of all its functions.
Some of these functions include:
• Output frequency
• Output power level
• Reference source configuration
• Calibration functions
• Tuning sensitivity
In addition to manual operation, all
functions can be controlled over GPIB
by a computer.
0.1 Hz frequency resolution
For applications that demand frequency
resolution finer than 600 MHz, add
Option 002 and an Agilent 8662A/3A
synthesized signal generator. This
combination of instruments provides
a signal from 2.4 GHz to 26.5 GHz
with 0.1 Hz frequency resolution
while preserving much of the low
noise performance of the 71708A.
With Option 002, simply enter the
desired output frequency and the
71708A automatically sets the frequency
of its internal microwave source and,
over GPIB, the frequency and power
of the 8662A/3A.
Typical phase and AM noise of the Agilent 71708A microwave source
and high quality microwave synthesizer
Courtesy of McDonnell Douglas
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Selectable tuning and phase noise
performance
Along with low phase noise, the
71708A provides a DC coupled tuning
port with three sensitivity settings.
This allows you to phase-lock the
71708A when using it as a reference
source for phase noise measurements
on synthesized sources. The three
tuning sensitivity settings are directly
coupled to noise performance and
allow the 71708A flexibility to adapt
to your measurement needs.
Built-in output power calibration
Periodic calibration of the output
power of the 71708A can be quickly
and easily performed using built-in
calibration functions and an external
power meter. Over GPIB, the microwave
source will automatically control an
Agilent 437B, 438A,or 70100A power
meter. Over MSIB, the 71708A will
automatically control the 70100A.
Microwave receiver noise measurements
In the past, measuring the noise of
microwave receivers required two
receivers driven by a common
microwave source. This was due to
the inadequate phase and AM noise
performance of the available
microwave sources. Using this
method, the noise of the microwave
source cancels out and the combined
noise of the two receivers can be
measured. However, it is difficult to
accurately determine the noise of
each of the individual receivers and
two receivers are required.
With the low phase and AM noise of
the 71708A and a 3048A phase noise
measurement system, this measurement can be made directly. By driving
the input of the microwave receiver
with the low noise 71708A, the noise
of the IF signal out of the receiver is
dominated by the noise of its
microwave conversion and IF processing components. The noise of the
IF signal can then be measured using
an RF reference source such as the
8662A, and the resulting absolute
noise of the microwave receiver measured directly.
Low AM noise
Low AM noise allows the 71708A to
be used as a source for AM noise
measurements of signal processing
components such as amplifiers and
mixers. This low AM noise performance minimizes the degradation of
residual PM measurements due to AM
to PM conversion in the device under
test or in the microwave phase detector.
Reference chain
The heart of the 71708A microwave
source is the reference chain which
consists of a 10 MHz crystal oscillator, 100 MHz oscillator, and 600 MHz
oscillator. Each of these oscillators
can be the primary reference, providing three different tuning sensitivities
with corresponding phase noise performance.
The 600 MHz signal from the reference chain is multiplied with a step
recovery diode which generates harmonics from 2.4 to 26.4 GHz. To
obtain a particular harmonic, this signal is filtered with a YIG tuned filter.
A variable gain GaAs amplifier boosts
the power of this signal.
Microwave receiver
Block diagram for microwave receiver noise measurements
Agilent 70428A microwave source block diagram
IF out
Reference
oscillator
Tune line "in"
600
MHz
SRD YTF
µ wave amp
µ wave LO "out"
8662A "in"
YTF
Option 002 only
µ wave amp
RF "out"
71708A E5500 SeriesReference source
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Configuration 1
All oscillators locked
• For those applications that demand
the lowest possible noise at all
offsets
• Tuning sensitivity of 0.05 ppm/volt
• Phase noise of –65 dBc/Hz at
10 Hz offset, –113 dBc/Hz at 1 kHz
offset and 10 GHz carrier frequency
Configuration 2
100 MHz and 600 MHz oscillators locked
• For those applications that require
the best phase noise >1 kHz and a
moderate tuning range
• Tuning sensitivity of 1 ppm/volt
• Phase noise of –33 dBc/Hz at 10 Hz
offset, –113 dBc/Hz at 1 kHz offset
and 10 GHz carrier frequency
Configuration 3
600 MHz free-running oscillator
• For those applications that require
a wide tuning range and a low
broadband noise floor
• Tuning sensitivity of 20 ppm/volt
• Phase noise of –20 dBc/Hz at 10 Hz
offset, –100 dBc/Hz at 1 kHz offset
and 10 GHz carrier frequency
Option 002
Option 002 of the 71708A adds the
capability to mix the internal microwave
source with an external RF source.
This option adds a microwave mixer,
a second YIG tuned filter, a second
GaAs amplifier, and associated signal
switching. Once the first YIG tuned
filter is tuned and the RF source frequency and power set, the second YIG
tuned filter is tuned to the correct
frequency. The variable gain GaAs
amplifier provides output power control of this composite signal.
10 MHz
100 MHz
PLL PLL
PLL BW
25 Hz - 10 kHz
Tune line
1 kHz - 30 kHz
PLL BW
600 MHz
To
Multiplier
10 MHz
PLL
PLL BW
25 Hz - 10 kHz
10 MHz 100 MHz
PLL
PLL BW
25 Hz - 10 kHz
100 MHz
Tune line
Tune line
PLL
PLL BW
1 kHz - 30 kHz
PLL
PLL BW
1 kHz - 30 kHz
600 MHz
To
Multiplier
600 MHz
To
Multiplier
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