Ap-Ifu - JRC NTG337-EL0 Instruction Manual

3.2. AP-IFU

3.2.1. Overview
AP-IFU consists of three blocks: IF section, digital section and interface section.
3.2.2. IF section
The transmission IF section performs quadrature modulation of 427.5MHz IF frequency according to the
transmission output from the digital modem installed in the WT-ASIC.
In the receiving IF section, the received burst signal level is adjusted by the automatic gain control (AGC)
function of the digital modem. The quadrature demodulator downconverts the received IF signal into the
baseband signal.
The digital section consists of a digital modem, TDD/TDMA framer, wireless MAC processor, and system
controller. These functionalities are equipped in the WT-ASIC.
The digital modem performs modulation and demodulation of transmitting and receiving burst signals.
The interface section has an interface between the AP and the upper unit (100BASE-TX).
The digital section consists of the wireless MAC processor, TDD/TDMA controller, modem and system
controller. The wireless MAC processor converts between the Ethernet frames that the interface section
handles and wireless MAC frames. It also schedules the dynamic slot assignment. The TDD/TDMA
controller performs scrambling, encryption, error correction and other processing. The system controller
performs operating parameter setting, state monitoring, control and testing for the modem, TDD/TDMA
processor, wireless MAC processor and network interface. It also sends and receives maintenance
signals via SNMP. It performs delay control, authentication and other procedures, operating parameter
setting, state monitoring, control and testing for the subordinate WTs over a DMF channel.
The transmission IF section in the IF section performs quadrature modulation for the transmission
baseband signals at 427.5MHz LOC frequency for upconversion to IF signals. It also controls the output
level to the desired level based on the control from the ASIC. The receive IF section equalizes the level of
the reception waves arriving in a wide level range using the automatic gain control (AGC) from the ASIC,
and then downconverts them into baseband signals.
Figure 3-4 is a block diagram of the AP-IFU.
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