4.3.2
Amplifier WARMUP mode
Requesting either the STBY or XMIT mode from the OFF mode will result in the TWT
cathode heater power being applied and the warmup timer (180 seconds) being
initiated.
Note:
If the ambient temperature is less than
7
10
8
C, the warmup timer period is
10 minutes.
During WARMUP, the STBY or XMIT modes can be requested, to select the mode
that the amplifier will enter at the end of the warmup period.
4.3.3
Amplifier STBY (Standby) mode
In this mode, the TWT cathode is at its operating temperature and is ready to enter
the XMIT mode. Power is applied only to the TWT cathode heater. Unless XMIT
mode has been requested, the amplifier will enter STBY mode when the warmup is
complete.
Following transmission, the STBY mode can be requested to remove the amplifier
from the XMIT mode.
4.3.4
Amplifier XMIT (Transmit) mode
With the amplifier in the STBY mode, selecting the XMIT mode results in the
application of helix and collector voltages to the TWT, allowing RF transmission. In
the XMIT mode, the RF output power and TWT helix current monitor features are
operational and the control of gain is possible using the (optional) Digital
Electronically Variable Attenuator.
4.4
Upconverter Operation
Products in the antenna mount range which include a UA or UB suffix in the type
number (e.g. N6315UA, N6318DUB) contain an integral block upconverter. The UA
suffix indicates an upconverter which operates over the RF input frequency range
950 to 1450 MHz, corresponding to an RF output frequency range 14.0 to 14.5 GHz.
The UB suffix indicates an upconverter which operates over the RF input frequency
range 950 to 1700 MHz, corresponding to an RF output frequency range 13.75 to
14.5 GHz.
The block upconverter comprises four main elements as shown in the block diagram
below; this modularity gives design flexibility allowing gain and frequency variants to
be accommodated. All modules are fully integrated within the standard package
outline, with the amplifier control system providing all power and control interfaces.
The L-band input signal should be connected to the N-type socket labelled ‘RF IN’.
The external 10 MHz locking reference input is fed into the unit modulated onto the
L-band input signal. This 10 MHz signal is split from the L-band input within the
amplifier, converted to 50 MHz and used to phase lock the frequency of the DRO.
The L-band input is fed to the mixer where it is combined with the LO and
subsequently fed to the bandpass filter. The waveguide filter is used to remove the
LO and other mixer products; it gives excellent rejection performance, with low loss
and a flat response. The output of the filter is connected to the input of the solid-
state amplifier (fixed gain or digital electronically variable attenuator version).
An ‘out of lock’ alarm signal is fed from the upconverter to the amplifier control
system (see note 1); this in turn is processed and provided as an advisory
‘upconverter fault’ alarm signal, available from the 41-pin user interface connector
(see sections 5 and 6, and note 2).
HBN63xx-1, Issue 8, Page 18
