NOVATECH INSTRUMENTS
40 MHz Direct Digital Synthesizer Module
Model DDS6m
Photo
Last Modified January 10, 2001
The DDS6m Direct Digital Synthesizer Module is a Precision 40 MHz
Signal Source on a small (2.5" x 3.5") circuit board. It provides both
Sine and Clock outputs from 100 Hz to 40 MHz in 0.025 Hz steps. The
RS232 serial interface makes it easy to set the output frequency and
save the settings in EEPROM memory. It has excellent spectral purity
and contains a quartz crystal oscillator with better than 5 ppm
accuracy. The DDS6m can accept an external clock input instead of the
internal oscillator. Multiple DDS6m can be locked together using an
external clock and the phase is programmable in 11.25 degree
increments.
Specifications
OUTPUT
Types: Simultaneous Sine, ACMOS (TTL compatible) and unfiltered Sine
Impedance: 50 Ohms
Frequency: 100 Hz to 40.000 MHz in exact 0.025 Hz steps (Using internal clock)
OUTPUT AMPLITUDE
Sine: Approx. 1 Vrms into open circuit, 0.5 Vrms into 50 Ohms
ACMOS: (TTL Compatible) Vol: 0.5 V max, Voh: 3.5 V min into 30 pF, <5 ns rise and fall times
FREQUENCY CONTROL
RS232 interface allows setting of frequency to 0.025 Hz. Fixed at 9600 baud. Internal (default) or external frequency update input can be used to synchronize frequency change.
PHASE CONTROL
Serial interface allows setting phase in 11.25 degree increments. An unlimited number of DDS6m can be phase synchronized together using an externally supplied CMOS level sync pulse. (When used with external clock input.)
SPECTRAL PURITY (Typical)
Phase Noise: <-125 dBc @ 1 kHz offset @ 5 MHz out
Spurious: <-55 dBc below 10 MHz
<-45 dBc below 40 MHz
Harmonic: <-50 dBc below 10 MHz
<-40 dBc below 40 MHz
ACCURACY AND STABILITY (Using Internal Clock)
Accurate to < +/- 5 ppm @ 25 C +/- 5 C, 24 hrs
Stable to +/- 10 ppm per year at 25 C +/- 5 C
EXTERNAL CLOCK INPUT
Jumper selectable external input accepts frequencies from 5 MHz to 100 MHz (typ. 120 MHz), 1 Vpp to 5 Vpp Sine or Square Wave. Output frequency is derived from this clock. 50 Ohm input impedance. Accuracy and stability depend on external clock.
CONNECTIONS
SMB for ACMOS out and Sine out. Three pin Amp for power. DE9F for RS232 (Tx: pin 2, Rx: pin 3, Gnd: pin 5). Two pin headers for external clock input, external sync input and unfiltered out.
POWER
+5 Vdc +/- 0.1 Vdc @ <175 mA
-5 Vdc +/- 0.1 Vdc @ <35 mA
< 50 mV noise and ripple
ENVIRONMENTAL
Operating Temperature: 5 C to 40 C
Humidity: 80% to 31 C, decreasing linearly to 50% at 40 C
SIZE
2.5 in by 3.5 in (6.4 cm by 8.9 cm)
SERIAL COMMANDS
F XX . XXX XXX XXX Sets frequency in MHz. Software sets to
nearest 0.025 Hz setting. 1 MHz default.
Decimal point required.
E D Disables echo.
E E Enables echo.
R Reset. Same as cycling power.
P N N is integer 0 to 31. Phase is set to
N*11.25. (N*Pi/16 radians)
A E Enables ACMOS/TTL output.
A D Disables ACMOS/TTL output.
Output is set low. (Lowers system
noise for critical applications)
SAVE Save current setting in EEPROM. Used
as default upon power up.
QUE Return current setting
PRICING
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Novatech Instruments , Inc.
P.O. Box 55997
Seattle, WA 98155 USA
Return to Homepage: http://www.eskimo.com/~ntsales.html
Technical Questions: novatech@eskimo.com