The amplifier stages in an RFPA are muted between the RF pulses.
This is for two reasons: it saves energy and more importantly it reduces noise.
The latter aspect is important as the spin echo shall be received as clearly as possible.
The above picture shows the sequence:
unblank (=pregate) the amplifier
switch the RF on
switch the RF off
blank the amplifier
Often steps 3 and 4 are executed simultaneously in order to reduce the output noise of the RFPA as quickly as possible.
Pre-Gating Time.
The pre-gating time depends on the frequency the amplifier is designed for.
The lower the lower frequency of the amplifier's bandwidth the longer the pre-gating time must be.
For specified values refer to the data sheet or manual.
For some models the option Fast Pregate is available.
With it the minimum pre-gating time is reduced to 1 - 2 μsec.
Level.
For the blanking signal use 5V TTL level.
Modifications may be possible upon request.
Polarity.
In most cases polarity is high active.
That means you need to connect 5V to pre-gate the amplifier.
However, polarity can be adjusted if necessary.
© barthel HF-Technik GmbH 2024 – T +49 (0)241 45015-40 – Imprint & Privacy