Theory Of Operation; General; Receiver; Transmitter - Motorola PRO1150 Manual De Uso

General

The product is a fully synthesized two-way FM
portable radio, designed to meet FCC specifications.
In addition to the channel frequencies, 38 different
PL codes are available. The radio is capable of
operating on any one frequency in simplex mode.
This radio is based on the Ultra Low Tier Zero
Intermediate Frequency (ULTZIF) integrated circuit
(IC).
The design is basically broken down into four
different areas: transmitter, receiver, frequency
generator, and audio/logic. The transmitter is a
three-stage discrete design. The receiver is best
characterized as a direct conversion type, with direct
detection of modulation accomplished using the
ULTZIF IC. Frequency generation is accomplished
using the ULTZIF's synthesizer, and an external
discrete VCO (Voltage Controlled Oscillator). The
audio/logic block includes the microcontroller, 2.75
V and 5.0 V regulators, compandor, voice synthesis
IC, and other interface and support circuitry. All
audio filtering is performed by the ULTZIF IC.

Receiver

The receiver of both the UHF and VHF radios
consists of the Front-End Circuit and the ULTZIF IC.
Receiver Front End Circuit
RF
Amp
Rx 5 V
Figure 4-17. Receiver Block Diagram
English
Bandpass
Filter
ULT ZIF
Detected audio

Theory of Operation

RF Amplifier
The RF amplifier boosts the low power of the input
signal to a more workable level using current from
the receiver 5 V supply (RCVR_EN). The amplified
output is applied to the bandpass filter.
Bandpass Filter
The bandpass filter is used to isolate out-of-
frequency signals and to remove any harmonics
which may have been introduced by the RF
amplifier.
ULTZIF IC
The ULTZIF (Ultra Low Tier Zero Intermediate
Frequency) IC has a receiver section that down-
mixes the carrier directly to audio, and performs all
audio filtering. It then passes the recovered audio
into a de-emphasis filter; then, from the IC into an
audio amplifier. The audio amplifier then boosts the
power to the speaker.

Transmitter

The VHF and UHF transmitters contain five basic
circuits: a Power Amplifier, an Antenna Switch, a
Harmonic Filter, an Antenna Matching Network,
and a Power Control Circuit. (Refer to Figure 4-18.)
PTT
3 dBm
Power
Antenna
Amp
Switch
VC
Microcontroller
Power Control
Figure 4-18. Transmitter Block Diagram
Section 4
Antenna
Harmonic
Match
Filter
*
50W
To Receiver
* NOTE: To connect to
W
50 remove antenna and
insert Antenna adapter
(HLN8362_)
4-1