Lectrosonics UT700 - Manual (Page 8)

UDR700 / UM700 / UT700
supplied with 48 Volts. A unique 16-position sensitivity
control at the element itself can also adjust the sensitiv­
ity over a 15 dB range. This is in addition to the normal
gain control in the wireless microphone. The result is
the widest dynamic range of any condenser mic in a
wireless microphone.
The VariMic TM has a three-point damped rubber suspen­
sion to reduce high frequency handling noise and a
generous sized windscreen to keep wind noise and
breath pops away from the microphone.
Comparing Diversity Reception and Rota-Versity ™
The UDR700’s new approach to diversity reception is a
vast improvement over traditional designs. Traditional
analog diversity reception designs employed techniques
ranging from simple antenna and audio signal switching
using one or two receivers, to dual-receiver ratio
combining systems. In the digital realm, even more
advanced techniques are possible to analyze and
correct antenna phase.
A popular phrase, “true diversity,” arose in defense of
dual-receiver audio switching diversity designs versus
very low cost receivers that simply had two antennas
mounted on a single unit. Diversity reception can be
implemented by mixing or selecting the audio from two
separate receivers, or by various antenna combining
techniques ahead of the receiver. In reality, all receiver
designs can aptly be called “true diversity” if they make
use of two or more antennas that are receiving diverse
(uncorrelated) signals.
Two diversity designs found in use today include Audio
Switching Diversity and Ratio Diversity. Both offer some
improvement in
audio reception,
but with a
significant
increase in
equipment costs
because of the
need for two
receivers.
SmartDiversity
™
from
Lectrosonics is
different.
SmartDiversity ™
SmartDiversity ™ is a microprocessor controlled tech­
nique that automatically analyzes audio content and RF
levels to determine optimum timing for the switching
activity. Active analog antenna phase switching tech­
niques use both antennas at the same time, with 180
degree phase switching to help keep the received
signals in phase and minimize dropouts. When the
overall RF signal strength quickly drops, the phase of
one antenna is switched 180 degrees. If the switch
increases the RF
level, it will remain
latched in that
position until the
RF level quickly
drops again. Both
antennas are used
at the same time,
so overall operating
range is also
improved.
Rota-Versity ™
ANTENNA PHASE
SWITCHING
RECEIVER
180 DEGREE PHASE
SWITCHING
MICROPROCESSOR
RECEIVER A
RECEIVER A
SWITCH
RECEIVER AUDIO OUTPUT
SELECTED BY RF LEVEL
AUDIO SWITCHING
DIVERSITY
AUDIO
OUTPUT
RATIO DIVERSITY
AUDIO COMBINING
AUDIO
OUTPUT
Rota-Versity ™ is only possible in the digital realm. Rota-
Versity TM uses a four-way phase shifter to combine the
output of two antennas in any of four phase angles,
each 90 degrees apart, regardless of RF levels. Hun­
dreds of times per second, all of the phase angles are
explored, with the angle offering the best reception
used for the audio data. The result is the diversity
system “tracks” the phase shift between the two anten­
nas to ensure that they always add to one another (they
are always less than 90 degrees out of phase). Multi-
path dropouts are minimized and operating range is
maximized by using both antennas simultaneously.
Because it times
phase switches
to happen only
during digital
packet headers
where no audio
is being con­
veyed, Rota­
versity
™ is also
transparent and
cost effective .
ROTA-VERSITY™ DIGITAL
PHASE CORRELATION
0
270
90
MICROPROCESSOR
RECEIVER
180
PHASE CORRECTED
COMBINING
LECTROSONICS, INC.
RECEIVER A
RECEIVER A
RECEIVER AUDIO OUTPUTS
MIXED IN OptiBlend™ RATIO
CONTROLLED BY RF LEVEL
AUDIO
PANNING
CIRCUIT
8