Lectrosonics UCR411 User Manual download pdf (Page 3)

UHF Wireless Digital Hybrid

Receiver

GENERAL TECHNICAL DESCRIPTION

The UCR411 is a portable, high performance, triple-

conversion, frequency synthesized, UHF receiver fully

compatible with all Lectrosonics 400 series transmitters.

The RF performance is extremely stable over a very

wide temperature range, making the UCR411 perfectly

suited to the rough environmental conditions found in the

field. The proprietary audio processing includes a digital

signal processor for very low distortion and a superior

signal to noise ratio.

The UCR411 features a menu-driven LCD graphic

display and a three button control panel as a convenient

means of viewing and altering user settings. The main

window, for example, shows the pilot tone indicator,

antenna diversity phase, RF level, audio level, receiver

battery status and transmitter battery status. It is also

possible to bypass the pilot tone from the main display

window. Other display windows show operating fre-

quency, audio output level, battery status in tenths of

volts and test tone status. The frequency scan mode

provides a spectrum analyzer for a graphical means of

observing all signals “on the air” within the frequency

range of the receiver in order to find operating frequen-

cies that are free of interference.

DIVERSITY RECEPTION

The UCR411 technology with SMART Diversity

minimizes dropouts in situations where multi-path

reflections can cause serious problems. The phase

diversity network and PIN diode RF switches are con-

trolled by the microprocessor using a sophisticated

algorithm to use both antennas simultaneously. This

design keeps the receiver compact enough for camera

mounting or shoulder bag applications, yet provides

effective diversity reception.

RF FREQUENCY TRACKING FRONT-END

AND MIXER

The receiver is frequency agile and can be set to operate

on any one of 256 frequencies within its tuning range. To

significantly reduce unwanted interference and

intermodulation problems, the UCR411 has a frequency

selective front-end section that tracks and tunes to the

desired signal frequency and rejects or “tunes out”

unwanted interfering signals. The design consists of four

varactor tuned ceramic transmission line resonators

controlled by the microprocessor to provide good selec-

tivity. The low noise high current RF amplifier was

designed with feedback regulation for stability and

precise gain in order to handle stronger RF signals

without output overload. The first mixer is of new GaAs

technology that has a very high third order intercept

point. This produces a robust front-end that is as selec-

tive as fixed single frequency designs and is suitable for

use in close proximity to other receivers and transmitters

commonly used in field production “bag” systems.

MICROCONTROLLER, PLL AND VCO

CIRCUITS

The 8-bit microprocessor is truly the “heart” of the

UCR411 receiver. It monitors user command inputs from

the front panel control buttons and numerous other

internal signals such as RF level, audio levels, pilot tone

levels and external/internal power voltages. Outputs

from the microcontroller drive the LCD display and

backlight, control the squelch and audio output attenua-

tor, and operate the front-end tuning, the PLL/VCO

circuits and the antenna phase switch. The UCR411

design and the advanced technology of the microproces-

sor control arguably set a new standard in wireless

microphone development.

IF AMPLIFIERS AND SAW FILTERS

The first IF low noise amplifier is controlled with feed-

back regulation and drives the first of two quartz SAW

(Surface Acoustical Wave) filters. The 244 MHz SAW

filters combine sharp tuning, constant group delay, wide

bandwidth and excellent temperature stability, far supe-

rior to conventional LC filters. The 244 MHz first IF

signal is converted to 10.7 MHz, filtered through two

ceramic filters for sharp selectivity, then converted to 300

kHz in one integrated circuit.

DIGITAL PULSE COUNTING DETECTOR

The UCR411 receiver uses an elegantly simple, yet

highly effective digital pulse detector to demodulate the

FM signal, rather than a conventional quadrature detec-

tor. This unusual design eliminates thermal drift, im-

proves AM rejection, and provides very low audio

distortion.

DSP-BASED PILOT TONE

The 400 Series system design utilizes a DSP generated

ultrasonic pilot tone to control the receiver audio muting

(squelch). Brief delays at turn-on and turn-off eliminate

thumps, pops or other transients that can occur when the

power is switched on or off. The pilot tone frequency is

different for each of the 256 frequencies in the tuning

range of a system (frequency block.) This eliminates

squelch problems in multichannel systems where a pilot

tone signal can appear in the wrong receiver via inter-

modulation products. The DSP generated pilot tone also

eliminates the need for fragile crystals allowing the

receiver to survive shocks and mishandling much better

than older analog-based pilot tone systems.

Rio Rancho, NM – USA

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