GL-T8200 1- to 25-Watt 900-MHz Transmitter System
Glenayre Document Number: 9110.01305
+DESCRIPTION
Rev. A: 03/24/99
Page: 3-4
Copyright © 1999 Glenayre
Print Date: 05/10/99
3.2.3
Paging Transmitter
The paging transmitter converts the digital signal from the transmitter controller into
modulated and amplified RF power.
Operation is in response to commands from the transmitter controller via the DSP exciter.
The transmitter monitors its functions and reports its status to the VDT and the GL-C2000
via the exciter. The transmitter controller permits the transmitter to be controlled and
monitored from a remote location. Local control and monitoring are performed through a
VT-100 video deplay terminal (VDT).
The DSP exciter combines functions of an RF exciter and a PA controller. The exciter
generates modulation using digital signal processing (DSP) to achieve accurate, stable
modulation that does not vary with time or temperature. The PA-control section monitors
transmitter status signals in the form of fault logic and voltage samples. The microprocessor
in the exciter reports PA status to the transmitter controller, VDT, and the exciter front
panel. If a malfunction occurs, the transmitter enters a reduced operating condition,
depending on the seriousness of the fault. PA control and status monitoring are performed
by the microprocessor, which consolidates control logic from the transmitter controller or
the locally operated VDT. Both the exciter and transmitter controller receive continuous
status reports from the microprocessor. The exciter is the control and status-monitoring
interface between the transmitter and the user.
The DSP exciter provides up to 400 milliwatts of RF drive.
A power-reference signal from the PA is fed back to the exciter, via the PA board, to allow
control and monitoring of output power. The exciter-supplied control voltage functions as
AGC control for the PA.
3.2.4
Video Display Terminal
The VDT, though not part of the transmitter, is required for setup, local control, and local
monitoring of the transmitter. The VDT can be any laptop or desktop terminal with a VT-
100 type program. The VDT interfaces the transmitter through the connector on the front
of the exciter. The VDT software is menu-driven.
3.2.5
Ac Power Supply
Refer to Figure 3-1. The switching power supply is mounted below the PA. The power
supply is two rack units high. The front panel contains a dc power on indicator.
3.3
Site Signal Flows
3.3.1
Site RF-Signal Flow
The on-frequency carrier is created by the VCO circuitry in the DSP exciter. It is then
modulated with paging information, amplified, and sent to the PA via connector J3 on the
back of the DSP exciter. Through coaxial cable, the carrier goes to the back of the PA,
where it is further amplified to a preset level under control of a microprocessor within the
exciter. The amplified carrier is cabled from the PA output to a low-pass filter and a triple
