BNMR: PSM (Pol Synth Module)
Links
Introduction
The PSM and PSMII VME modules are used to produce RF for the bnmr and bnqr respectively.
PSM Manuals
- Hardware Manuals:
- Programming Guides:
Description
Please refer to the #PSM Manuals from which much of this information is derived.
The POL Synthesizer Module (PSM) is a VME module built at TRIUMF, incorporating a AD9857 Quadrature digital upconverter. It has been designed to generate a complex modulation swept RF signal summed with a reference frequency (fREF). The swept signal may be a single modulated carrier (1f) or include the modulated 3rd and 5th harmonics (3f and 5f). Each carrier is independently modulated.
- Note
- the harmonics and the reference frequency ( 1f,3f,5f, fREF) are known as "profiles".
- Do not confuse the "1f" profile with the Experimental (PPG) Mode 1f (Freq) !!
For the bnmr and bnqr experiments only profile "1f" is implemented, except for PPG Mode 1f (Freq) where both 1f and fREF are supported.
The PSM can be operated in two modes:
- Single Tone Mode
- carrier is not modulated, the output signal consists of a single frequency signal. Frequency data are read from the Frequency Sweep Memory (1f,3f,5f) or from the Frequency tuning register (fREF). At least one strobe must be issued.
- Quadrature Modulation Mode
- both the I and Q data paths are active, the output is a quadrature modulated analog output signal. The I and Q data are read from the I&Q data memory. Each profile (1f,3f,5f,fREF) has its own I&Q memory. If an unmodulated carried is needed, I,Q pairs are set to constant values. When the I,Q memory length is set to zero, the output is modulated by a pair of constant values.
The carriers are synthesized and modulated digitally. In quadrature modulation mode, the modulation data consists of up to 2048 I,Q pairs sampled at a submultiple of the carrier sample rate. The synthesizer circuit interpolates the I,Q sample rate to match the carrier sample rate before modulation. The only modulations currently available are the ln-sech and Hermite functions.
See #PSMII Module in the BNMR experiment for a summary of how the PSMII differs from the PSM.
PSM Module in the BNQR Experiment
The PSM module is programmed differently for a Type 1 (I-MUSR) or Type 2 (TD-MUSR) experiment.
- Type 1 (I-MUSR) experiment
- (e.g mode "1f") where the frequency remains constant during the cycle, and is changed by a command from the frontend at the end of each cycle (no frequency file is downloaded);
- Type 2 (TD-MUSR) experiment
- where a frequency file is downloaded, so that the PSM steps through a sequence of frequencies during the cycle. The frequency file is generated automatically from the input parameters in the odb. In Single Tone Mode, the user can select which profile(s) are enabled (at least one must be enabled), and also select the tuning frequency.
The PSM can be used in Single Tone mode or Quadrature Modulation Mode. The output signal can be modulated with a single I,Q pair, or an I,Q pairs file can be generated automatically according to the parameters supplied. All the I values or all the Q values can be set to 0 for testing.
PSMII in the BNMR experiment
The PSMII module is a modified PSM module, and it runs at a higher frequency (up to almost 80MHz compared with the PSM's almost 40MHz).