Bruker DAEDALUS, Service Manual

Page: 46 / 145

Lock Transmitter
40 Spectrospin AG Daedalus Lock Manual
N x 10 MHz Multiplier 5.1.4
The Deuterium frequency is generated by mixing a DDS frequency and an assisting
frequency. The assisting frequency is a multiple of 10 MHz and depends on instru-
ment version. It is generated in the N x 10 MHz multiplier.
The construction of the 60 MHz Multiplier remains the same. The various assisting
frequencies are listed below.
Instrument Assisting Frequency
[Version] [N x 10 MHz]
750 100 MHz
600 80 MHz
500 90 MHz
400 50 MHz
300 60 MHz
360 70 MHz
250 50 MHz
200 20 MHz
Direct Digital Synthesizer (DDS) 5.1.5
This synthesizer generates selectable frequencies that make variations in the lock
frequency (Lockshift) possible. The DDS module (IC6) calculates with a clock rate
of 60 MHz the amplitude values for the desired output frequency. The frequency is
dependent upon the operating frequency and lies between 9 and 16 MHz. The small-
est frequency shift is 14 mHz.
The DDS also allows you to quickly switch the output signal phase. This is impor-
tant because the transmitting and receiving phases are different. These differences
can be up to 360 degrees and the setting accuracy is less than 0.1 degree. Fast
switching is possible because the DDS contains two programmable phase registers.
The serial S_BUS and 8 Bit serial-to-parallel shift registers control the DDS.
A 22 MHz low pass filter (LP1) following the DDS suppresses interference.
A low frequency function test is possible using the diagnostic channel DIAG_2.