User Manual

Technical Description
Version 4 4-3 04/02/04
4.3 EXTEND-A-PAGE TRANSMITTER UNIT EXCITER
The exciter module of the Extend-A-Page VHF transmitters utilizes advanced
direct digital synthesis techniques to achieve ultra-high stability analog composite
modulation or a two and four level FSK output at modulation rates 3200 baud (2
Level) and 6400 baud (4 Level) depending on the selected mode configuration.
The Extend-A-Page exciter is divided into two parts: the exciter control board
and the exciter board.
4.3.1 Exciter Control Board
4.3.1.1 Circuit Description
The EWI-FLEX-01-HS is a synthesized RF module, capable of setting the
Transmit frequency within 150 MHz to 174 MHz.
The transmit mode can be selected to generate either of the following,
center frequency, analog composite, binary FSK, or 4 level FSK
depending on the input mode lines, ICFOVRH, IMFSKH, and
IDIGMODEH. The frequency of operation is setup with the control of two
Phase Lock Loop (PLL) synthesizers in the RF module FLX-150B. The
interface to setup the unit is a serial data interface using a common data
and clock lines, and two strobe lines. One strobe line (PLLSTB) selects
the channel offset PLL the other (XINSTB) selects the modulation loop.
The RF module is supplied with two inputs, the 3 MHz high stability
reference frequency and the 10.7 MHz digital data modulated IF input.
The 10.7Mhz IF module has a fixed peak deviation output depending on
the mode of operation. The analog composite mode has a 2.4KHz peak
maximum limit, but can be attenuated on the Control “A” board. The digital
mode has a deviation of +/-2.4 KHz. The data rate is from dc to 3200 bps.
The digital symbols that are clocked into the IF modulator. The
parallel inputs for the symbols are IDTB1, and IDTB0, along with the
symbol clock IDTCLKH. The data transitions are shaped using a linear
ramp pulse shape. There are four shaping configurations that are
selected by the two parallel bit inputs IDHDT1, and ISHDT0. There is also
a transmit control line to key the transmitter on and off, TXCONT. All
controls to the Model EWI-FLEX-01-HS are TTL compatible logic levels.
The transmitter will synthesize the frequency on which to transmit,
determined by the “Program Data” data stream sent to it. Appendix page
A-45, Figure 7A shows an example of one such data stream. The
frequency data stream is written into an embedded software program and
burned into the PROM memory of a microcontroller. Therefore, the