13
THEORY OF OPERATION
Functional Block Diagram
Major blocks in the AB-HDRX diagram include:
•
Dual Antenna Inputs
•
Dual Microwave Receiver and COFDM Demodulator Circuits
•
Dual Input Maximal Ratio Combining Circuit
•
MPEG4 Video Decoding Circuit
•
Video Output Interfaces: ASI, SDI, and Composite Video
•
Left and Right Audio Output Interfaces
•
Preset Selection and Status Monitoring User Interface
•
Programmable Serial Interface and Internal Control CPU With Flash Memory
•
Interface For Firmware Upgrades
•
Power Circuitry
Pre RF
Filter
Pre RF
Filter
Narrow
Band
IF
High
Dynamic
LNA
Antenna
COFDM
Demodulator
MRC
Combiner
Decryption
Ethernet
MEGTSoIP
Pre RF
Filter
Pre RF
Filter
Narrow
Band
IF
High
Dynamic
LNA
Antenna
COFDM
Demodulator
Figure 7: Internal Block Diagram
Dual Antenna Inputs
The AB-HDRX has two N-Type antenna input connectors. The input impedance of the antenna connectors are 50 ohms.
The frequency band supported by the antenna connectors are labeled next to the antenna inputs.
Dual Microwave Receiver COFDM Demodulator Circuits
The AB-HDRX is capable of receiving COFDM transmissions from compatible products. Each antenna input is filtered and amplified by a
low noise amplifier. The output of the amplifier is filtered again at the output of the RF receiver circuitry. The receiver mixer down converts the
received signals to the internal IF frequency.
The COFDM demodulator is programmable to support transmission modes offering different data rates (Refer to Chapter 4 for more
information). The output of the COFDM demodulator circuits contains transport streams carrying audio, video, and user data.
