WJ-8611 DIGITAL VHF/UHF RECEIVER
5-2 CIRCUIT
DESCRIPTIONS
frequency control data to the reference synthesizer to lock the reference
oscillator to the external signal.
The Digital Control PC Assembly (A2) contains a control processor, a high
speed A/D converter, and Digital Signal Processing (DSP) circuitry for
processing of the signal data. It also contains D/A conversion and analog
circuitry for reconstruction of the analog signals. The A/D converter
circuit accepts the 250 kHz IF signal from the RF Tuner Assembly (A3)
and converts it into 12-bit digital data that can be interpreted by the DSP
processors. This data is converted to a serial data stream and is routed
through digital filtering circuits and to the Digital Signal Processor (DSP)
circuits for further processing. The DSP circuitry converts the digitized IF
signal data from a continuous time domain signal into discrete time
samples that are stored in random-access-memory (RAM) and processed
digitally to perform wide range operations, such as:
•
Receiver Fine Tuning to a 10 Hz resolution,
•
IF Bandpass Filtering,
•
Input Signal Strength Determination,
•
Receiver Gain Control,
•
Signal Detection and Demodulation,
•
Noise
Blanking.
Upon completion of the signal processing, the serial data stream,
representing the demodulated audio and video signal intelligence, is
converted back to analog signals and are routed to the audio and video
outputs. At the rear panel, terminal bus TB1 provides the audio at LINE
A, and LINE B. With AM, FM, CW, or SSB detection modes selected,
both of these line audio outputs contain the same signal. In the ISB
detection mode, the lower sideband is output at LINE B, and the upper
sideband is output at LINE A. A Digital IF Output is provided to the rear
panel via connector A2J14 and Cable W4. This is a post filtered IF in the
form of its complex I and Q components. The IF data is output serially as
a series of 16-bit I (In-phase) and Q (Quadrature-phase) word pairs,
transferred at a 10 MHz clock rate. Along with the data, the interface
provides a data strobe and qualifying line that identify the start of each
data word and the phase that it represents.
The Digital Control PC Assembly (A2) supports receiver control from
three control sources. It communicates with the Front Panel Assembly
(A1) using a serial communications link to provide front panel display
updates (TXD, J29, pin 3) and to accept data generated by front panel key
presses (RXD, J29, pin2). The remaining control ports connect to the rear
panel for remote control by an external controlling device. The IEEE-488
I/O port supports bit-parallel, byte-serial control with an IEEE-488 (GPIB)
equipped computer. The RS-232 I/O port supports serial communications
with an RS-232 equipped computer.
Courtesy of http://BlackRadios.terryo.org
Summary of Contents for WJ-8611
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