User's Manual

Model 1150A DVOR
2-24 Rev. - November, 2008
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The signal then enters a buffer then a passes through a 6 dB fixed attenuator. The signal then passes through a
voltage controlled phase shifter with up to 360 degrees of phase shift. This phase shifter is used in a control loop to
correct for any phase shift due to temperature, and aging so that the output phase remains constant. After the phase
the signal passes through a buffer then a fixed 6 dB attenuator and then a voltage variable attenuator used to
amplitude modulate the RF signal.
The signal then passes through a buffer then a pre-driver and then the final amplifier. The signal then passes through
a low pass filter to eliminate the higher harmonics of the RF signal. The signal then passes through a dual directional
coupler. Both forward and reverse RF paths are provided from the coupler.
The phase control loop maintains the output phase of the sideband generator the same relative to a sample of the
input phase. A sample of RF signal is taken after the manual phaser. This is considered the reference phase. Another
sample of RF signal is taken from the directional output and 3 dB two way splitter. A phase detector strips the
modulation from the signals and compares the phase and produces an error voltage that is used to control the mean
phasor in order to keep the input to output phase constant.
The amplitude control loop receives a sinusoidal signal from the Audio Generator. The amplitude of this signal sets
the output power of the Sideband Generator. The sinusoidal signal is rectified and used for the reference signal to
the amplitude control loop. A sample of the amplitude modulated signal is derived from the directional coupler
forward port and split by the 3 dB two way power divider. The signal then enters the forward power linear detector.
The output of the detector is fed into the error amplifier. The error amplifier is used to drive the voltage controlled
attenuator. The error amplifier makes sure that the input and output signals are the same.
The reflected power monitor compares a sample of the forward signal and sample of the reflected signal from the
directional coupler to determine the VSWR of the circuits following the Sideband Generator.
The power applied to the Sideband Generator is approximately 48 Vdc. The power supply circuitry is common to
both sidebands on the board. A 48 V to 28V converter module is mounted to the back side of the board. This module
supplies most of its output power to the final amplifier transistors. Another power supply is comprised of discrete
components and generates +5 Vdc from the 48 Vdc input. The 5 Vdc is used by another switching power supply to
generate the +12 and -12 Vdc supply voltage.
The sideband generator has an on board temperature sensor that is monitored by the RMS processor.
2.3.2.6.2
Sideband Generator CCA Detailed Circuit Theory
There are two Sideband Generators on the circuit card. Only one will be described along with the circuitry common
to both Sideband Generators.
The CW RF enters on connector P1:D at approximately 0 dBm. The signal is equally split by he -3 dB power splitter
formed by L1, L2, C2, C7 and R7. The signal then passes through high pass filter formed by C8, C10 and L3.
The signal then enters the phase shifter formed by T2, C12 and C16. This phase shifter has a range of approximately
+/- 60 degrees of range and is the manual phase shifter. This phase shifter is used to align all the sideband amplifiers
to the same phase. The diodes CR1 and CR2 are varactor diodes that vary in capacitance based on the voltage
applied. The operational amplifier U1amplifies the SB1_PHS signal that originates at the Audio Generator. This
voltage is controlled from the PMDT as a Sideband Phase offset setting
After the manual phase shifter the signal is split by a 6 dB splitter formed by R15, R17 and R18. A sample
(SB1_REF_PHASE) is provided to the phase comparator circuit described later. The signal then enters a phase
shifter with transformer T4, controlled by the Phase control loop voltage (SB1_MEAN_DYN_PHASE). After the
phase shifter the signal is amplifier by U3 with a fixed 20 dB gain.