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PTS
offers one of the most complete lines of frequency synthesizers
available in the industry. Our models all use our own direct
synthesis systems. Their advantages over competitive designs
include excellent specifications with low phase noise,
fast switching speed and low spurious outputs along with
low complexity.
Each model is a direct frequency synthesizer capable of providing signals
for many uses requiring stable and accurate sine-wave signals with low
spurious outputs, low phase noise and fast switching between selected frequencies.
Typical applications include wireless communications, precision clock sources,
radar and surveillance systems and automatic test systems (ATE) with both
narrow and wide-band coverage. Options based on a modular design concept
permit a high degree of adaptation to a customer's specific needs.
To learn more about our product specifications and pricing, request
a catalog today. If you have questions about applicability or performance
detail, contact PTS; demonstrator
models are available for evaluations. |
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INTRODUCTION
TO PTS SYNTHESIZERS
PTS frequency synthesizers
are precision frequency generators. They transfer the accuracy
and stability of a frequency standard operating at 5.0
or 10.0 MHz, either built-in or external, to a selectable
output frequency.
Each model is a direct frequency synthesizer capable of providing signals
for many uses requiring stable and accurate sine-wave signals with low
spurious outputs, low phase noise and fast switching between selected frequencies.
Typical applications include communications, spectrum analysis and surveillance,
radar and automatic test systems (ATE) with both narrow and wide-band coverage.
Options based on a modular design concept permit a high degree of adaptation
to a customer’s specific needs.
Up to ten significant figures and resolution to 0.1 Hz are available; custom
higher resolution is also available. All output frequencies are coherent with
the standard frequency and reflect its stability and accuracy. Any frequency
within the instrument’s range may be selected by manual dial or by remote
control. The output from the levelled system is +3 to +13 dBm (for most models)
into 50 ohms and may be adjusted manually by the front panel control or remotely
by analog voltage.
PTS synthesizers offer a choice of the two most widely-used remote
interfaces. Instruments may be equipped with either the BCD-parallel
(buffered) or the GPIB (IEEE 488) interface. In addition, PTS now offers the
industry's fastest GPIB list-processing capability; this enhanced interface
features full IEEE 488.2 and SCPI capability.
The PTS systems of synthesis drastically cut complexity and parts count.
The attendant reduction of primary power input and dissipation (less than
50% of that of competitive designs) is a major factor in the reliability, which
is further enhanced by a packaging system maximizing mechanical integrity
and stability while keeping weight low. For ease of service, most modules
are of plug-in design and used in all models.
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REMOTE CONTROL INTERFACES
For remote-control or computer-controlled
applications, all PTS synthesizers are equipped with either a standard
parallel BCD interface, or an optional GPIB-compatible interface. (Lower
cost remote-only units are available which include no manual control capability.)
With both interfaces, output signal frequency, output signal level, and
remote/local mode control are programmable.
Parallel BCD Interface
The parallel BCD interface employs a 50-pin
Amphenol 57-40500-compatible connector on the equipment, and requires an
Amphenol 57-30500-compatible connector for control.
In the standard parallel BCD interface, output signal frequency programming
and remote/local mode control programming use TTL-level negative true logic.
Output signal level programming uses a DC control voltage.
The programming format for frequency control is parallel, 4 bit
BCD coding for each digit (decade). All frequency programming connects
to, and can be driven by, industry standard 74HCT-type ICs. By default,
all frequency control lines are internally pulled to a high (false) state;
to program a specific frequency the appropriate pins must be brought to
the low (true) state.
Data latches are included which provide storage when a "latched" or "buffered" mode
of operation is required. By default, all Latch Enable (LE) pins are internally
pulled to a high (false) state, disabling the latches. To store remote
frequency programming input, the LE pins are brought to the low state.
To operate in a "transparent" (i.e., non-latched) mode, the LE
pins may be left unconnected. A separate LE line is provided for each digit
pair (8 bits) so that operation with serial frequency programming data
bytes is possible.
The output signal level is programmed via a DC control voltage.
The RMS RF output voltage is one-half (0.5) the DC analog voltage present
on the output-level control pin (0.63 to 2.0 VDC, corresponding to 0.315
to 1.0 Vrms output into 50 ohms).
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GPIB Interface
The GPIB interface employs an IEEE-488 24-pin
female connector on the equipment, and requires an IEEE-488 24-pin male
connector for control.
PTS offers two versions of the GPIB interface:
-a fast-switching legacy version which is IEEE 488.1(1987)-compliant.
It allows the synthesizer to act as a basic listener device (no talk
capabilities), and provides control of the two device-dependent functions
output signal frequency and level. Output signal frequency can be programmed
in 30 µseconds or less to the instrument’s full resolution; signal level
is programmed from + 4 dBm to +13 dBm in 1 dB steps.
-a fully IEEE 488.2/SCPI-compliant interface. It allows complete control over
all instrument functions and status. Switching speeds are 5 - 10 mseconds, or
less than 250 µseconds in the LIST mode of operation.
The PTS GPIB can be controlled via special-purpose GPIB controllers. Alternatively,
a number of manufacturers provide low-cost board-level products for microcomputers
which implement the IEEE-488 interface. The PTS GPIB remote-control interface
is compatible with such products.
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FREQUENCY
SWITCHING BEHAVIOR
In all PTS synthesizers, the most significant
digits down to 1 MHz (all produced by direct analog technology) have phase-coherent
frequency switching.
For applications requiring high-speed, phase-continuous frequency switching,
PTS offers the Direct Digital Synthesis Table Look Up (DDS-TLU or DDS)
option. With this option, the standard direct analog low-resolution subsection
of an instrument is replaced with a direct digital subsection capable of
generating the required low-resolution frequency increments. The DDS can
provide phase-continuous frequency switching, and less than 1 µs switching
time (with 2 µs delay). The following versions are available:
- Version H – DDS option replaces
the 100 KHz through 0.1 Hz subsection. Phase continuity can be maintained
during frequency switches involving the 100 KHz through 0.1 Hz digits.
Spurious outputs are -60 to -70 dBc.
- Version K – DDS option replaces
the 10 KHz through 0.1 Hz subsection. Phase continuity can be maintained
during frequency switches involving the 10 KHz through 0.1 Hz digits.
Spurious outputs are -65 to -75 dBc.
The DDS option is available for PTS models
040, 120, 160, 250, 500 and 620. (DDS high speed, phase-continuous switching
is standard in the PTS model 310, 1600, 3200, 6400, x10, D310 and D620.)
Note that the spurious specifications for the versions differ, reflecting
the tradeoff between bandwidth coverage and spurious output; consult instrument
specifications for details.
In instruments using the analog mix-and-divide technology for steps from
100 KHz down to 0.1 Hz, frequency switches have limited, though arbitrary,
phase discontinuities. In principle, a frequency switch using the 100 KHz
digit may have at most a 180° phase jump, a frequency switch using
the 10 KHz digit at most an 18° phase jump, 1 KHz at most 1.8°,
100 Hz at most 0.18°, 10 Hz at most .018°, 1 Hz at most .0018°,
0.1 Hz at most .00018°. For all practical purposes, frequency switches
of 100 Hz or less may be considered phase-continuous in these instruments.
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FREQUENCY STANDARDS
The output frequency of a PTS synthesizer reflects directly the accuracy
of the controlling frequency standard, either internal or external. PTS
offers a choice of two internal standards: a high-stability oven-controlled
crystal oscillator (OCXO), or a moderate-stability temperature-compensated
crystal oscillator (TCXO).
All quartz crystal oscillators are secondary standards which require a
primary reference for calibration. PTS oscillators are set to within 1x10-7
of nominal at the time of delivery from the factory. Thereafter, these
oscillators are subject to the time-drift and temperature-drift given in
the specifications. Both PTS oscillators include field-adjustment capability
for up to five years of aging.
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