Vertex Standard FT-1000MP - Manual (Page 74)

Page 72 O
PERATING
M
ANUAL
EDSP
Advanced Features
Enhanced Digital Signal Processing uses A/D (Ana-
log to Digital) and D/A (Digital to Analog) conversion
techniques under microprocessor control to achieve
significant enhancement of signals at the audio and
low-frequency IF levels. The major capabilities offered
by EDSP lie in the area of heterodyne/random noise
reduction and audio bandpass filtering. Digital filters
have many advantages over their analog counterparts
in that they can meet tighter specifications on param-
eters such as voltage and temperature drift and noise
problems. And the hybrid filter architecture of the
MARK-V FT-1000MP
Field, utilizing extensive analog
IF filtering to protect the DSP circuitry which follows,
guarantees superior strong-signal performance under
crowded band conditions.
The MARK-V FT-1000MP
Field uses a 16-bit NEC
µPD77016 CMOS digital signal processor chip featur-
ing a 30-nS Instructions Cycle, 33 MHz Clock fre-
quency, a 16 x 16-bit and 40-bit multiply accumulator,
40-bit Barrel Shifter, and 64 K Bytes Program ROM.
DSP enhancement is basically a four-step process.
Audio (or EDSP IF) input is sampled several thousands
of times per second, then the frequency and ampli-
tude of the audio are converted into a digital represen-
tation of the analog waveform that resembles ascend-
ing and descending “staircases” by the A/D (analog-
to-digital) converter. This is later changed into digital
serial bitstream as raw data for analysis and process-
ing.
Information is extracted from digital data, and the
EDSP chip performs complex mathematical calcula-
tions according to pre-programmed routines known as
algorithms. Algorithms are processed then compared
against a set of parameters (or threshold if you will)
based on a phenomenon known as “correlation.” The
degree of correlation depends on the incoming signal’s
characteristics: random noise has relatively little cor-
relation, speech contains moderate correlation, with
heterodynes (and QRM) being highly correlated. The
EDSP microprocessor is programmed with various
parameters corresponding to different known audio
phenomena.
EDSP allows the frequency spectrum of a received
signal to be modified according to a specific set of pa-
rameters for the desired effect (QRM reduction, audio
tailoring, etc.). Certain types of audio interference leave
a distinctive signature or “footprint,” which can be rec-
ognized, and “processed out” of the digitally-recon-
structed audio from the EDSP chip. Also, digital filters
are constructed which emulate traditional low-pass,
high-pass, band-pass, and band-stop filters, except with
steep skirt shaping and performance possible with digi-
tal technology. EDSP also allows direct “digital” de-
modulation of audio for receive, as well as direct modu-
lation of audio for transmit.