Lectrosonics UH400a - Manual (Page 4)

UH400A/UH400TM
General Technical Description
UH400A Block Diagram
Introduction
Digital Hybrid Wireless ™ is a wideband design with
±75 kHz deviation produding an excellent audio signal
to noise ratio and wide dynamic range. The switching
power supplies provide constant voltages to the trans­
mitter circuits from the beginning (9.3 Volts) to the end
(5.5 Volts) of battery life. The input amplifier uses an
ultra low noise op amp for quiet operation. It is gain con­
trolled with a wide range dual envelope input compres­
sor which cleanly limits input signal peaks over 30 dB
above full modulation.
Digital Hybrid Technology
All wireless links suffer from channel noise to some
degree, and all wireless microphone systems seek
to minimize the impact of that noise on the desired
signal. Conventional analog systems use compandors
for enhanced signal to noise ratio, at the cost of subtle
artifacts known as “pumping” and “breathing”. Wholly
digital systems defeat the noise by sending the audio
information in digital form, at the cost of some combina­
tion of power, bandwidth and resistance to interference.
The Lectrosonics Digital Hybrid Wireless
™ system
(hereafter called Digital Hybrid) overcomes channel
noise in a dramatically new way, digitally encoding the
audio in the transmitter and decoding it in the receiver,
yet still sending the encoded information via an analog
FM wireless link.
This proprietary algorithm is not a digital implementa­
tion of an analog compandor but a technique which
can be accomplished only in the digital domain, even
though the inputs and outputs are analog signals.
Channel noise still has an impact on received signal
quality and will eventually overwhelm the receiver. The
Digital Hybrid simply encodes the signal to use a noisy
channel as efficiently and robustly as possible, yield­
ing audio performance that rivals that of wholly digital
systems, without the power and bandwidth problems
inherent in digital transmission. As always, these
advantages come at a cost. The Digital Hybrid system
requires fairly intensive digital processing in both the
transmitter and the receiver. These processors cost
money, take up space and consume power. The Digital
Hybrid system also requires that the underlying RF link
be of excellent quality, with better frequency response
and distortion characteristics than that required by con­
ventional systems.
Because it uses an analog FM link, the Digital Hybrid
enjoys all the benefits of conventional FM wireless
systems, such as excellent range, efficient use of RF
spectrum, and long battery life. However, unlike con­
ventional FM systems, the Digital Hybrid has done away
with the analog compandor and its artifacts.
LECTROSONICS, INC. 4