Technalogix TAU-100, Руководство пользователя

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IV-4
Isolator
The power amplifier pallets are protected in part by the isolator located in the filter enclosure. It is
actually made up of a circulator and 50-ohm dump resistor. The circulators’ specifications include an
insertion loss of less than 0.2dB with an isolation rating better than 20dB. Any reflected power gets
dumped into the flanged power resistor. This way, there is instantaneous protection due to the isolator
setup and long term protection due to the software.
Filter
The passive bandpass filter rejects spurious and harmonic output products and passes the UHF
channel RF output. The cavity resonator uses aperture coupling. Typical insertion loss is 0.3 dB to 0.6
dB depending on channel frequency. Average roll off is –33 dBc at a point 4.5 MHz below the peak
visual carrier frequency and –30 dBc 9.0 MHz above the peak visual carrier frequency. The filter is DC
grounded on both the input and output for additional lightning protection.
Directional Coupler
The Technalogix dual directional couplers provide DC voltages proportional to forward and reflected
RF power monitoring. These analog voltages are converted for processing using a 10-bit analog to
digital converter. The microcontroller system monitors power supply voltage, forward and reflected RF
power, amplifier module temperature, the input video signal and the “VIEW” display request button.
The LCD is based on the industry standard HD44780 controller and contains 4 lines with 20 characters
per line. The LCD communicates with serial-to-parallel latches on the monitor and control circuit board
and the latches communicate with the microcontroller via a custom serial interface.