UNIMO Technology PZ-S Series User manual

Maintenance Manual
PZ-S series Portable Radio
Circuit Analysis
PZ-S400, PZ-S100

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TABLE OF CONTENTS
FRONT ASSEMBLY..............................................................................................................................................3
Microphone and Speaker.................................................................................................................................3
REAR ASSEMBLY ................................................................................................................................................3
CIRCUIT ANALYSIS.............................................................................................................................................3
AUDIO/LOGIC SECTION.............................................................................................................................3
Microprocessor U100 ............................................................................................................. 4
3.3 Volt Regulator U50 ........................................................................................................... 4
Personality EEPROM............................................................................................................... 4
Low Battery Sense.................................................................................................................. 4
Liquid Crystal Display (LCD) .................................................................................................. 5
Audio Processor...................................................................................................................... 5
Audio Amplifier (U59) ............................................................................................................. 6
R/F SECTION ................................................................................................................................................. 6
SYNTHESIZER CIRCUIT......................................................................................................... 6
TRANSMITTER CIRCUIT ....................................................................................................... 8
RECEIVER CIRCUIT................................................................................................................ 9

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FRONT ASSEMBLY
The Front Assembly includes the speaker, PTT key button, Monitor button.
Microphone and Speaker
The microphone mounts directly onto the main PCB board. The microphone receives audio through the
hole in the front housing.
The speaker mounted onto the front housing, and connects to the main PCB board through the solder wire.
REAR ASSEMBLY
The Rear Assembly provides a die-casting frame for main board and sub-board. The antenna connects to a
SMA type connector that is mounted to the top of the frame.
The circuit of MAIN board of PZ-S series radio consists of the Audio/Logic circuitry (which controls the
functions of Radio) and the RF circuitry.(which decides the communication quality and performance) The
circuit of sub board consists of battery connectors and fuse for protected the main circuit.
CIRCUIT ANALYSIS
AUDIO/LOGIC SECTION
The Audio/Logic circuit consists of logic circuitry and audio receiver/transmitter circuitry. The
Audio/Logic circuit is common to UHF and VHF models. A single microprocessor on the board controls
the operation of the radio. The processor scans the control switch and issues commands to the RF board.
The Audio/Logic circuitry consists of primarily of the followings.
Microprocessor
Personality EEPROM
Audio signal processor
The schematic diagram is described in Fig . The first sheet contains all input/output connection for
the board. And the second sheet contains logic circuitry and audio signal circuitry.

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Microprocessor U100
A single microprocessor controls the all operation of the PZ-S series radio. All lines connect to the analog
portion of the board are first RF bypassed by RC circuits. Most of these RC circuits are physically located
as close as possible to each microprocessor pin of the board.
The microprocessor contains internal flash memory. The microprocessor normally executes the radio
software code in this Flash memory.
The Reset circuit consists of voltage detector (Q102), R101 and C117. If the input level of voltage
detector (Q102) is less than DC+2.7V, the reset circuit generates a reset signal automatically.
3.3 Volt Regulator U50
A single 3.3volt regulator U50 supplies all circuitry on the board. The regulator receives input voltage
from the battery (nominally 7.5Vdc) and fuse F50 provides protection for the main circuit.
And also the 3.3 volts for RF section and VCO can be controlled separately by microprocessor.
Personality EEPROM
A 2048 X 8 bit EEPROM U103 stores all customer frequencies, tones and option information. Tune data
aligned with the RF section is stored for transmit high power level, transmit low power level, audio
deviation, data deviation and squelch.
☞
CAUTION`
If replacement of U103 personality EEPROM, contact UNIMO Technology Co., Ltd. Customer
Service to obtain programming information.
The microprocessor serially communicates with the EEPROM on the IIC_CLK AND IIC_DATA lines (or
the Inter Integrated Circuit Bus) Programming of the EEPROM is accomplished without opening the
radio by communication with the microprocessor through the Phone jack connector.
Low Battery Sense
The low battery sense circuit (R119, R121, R112, C108) monitors the current voltage state of the battery.
This low battery sense voltage is sent to microprocessor U100 pin 63. This pin is analog-to-digital
conversion port and the microprocessor measure the voltage level.. When the battery voltage drops below
approximately 6.3Vdc, generates a low battery alert sound.

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Liquid Crystal Display (LCD)
The LCD assembly is on the Board. It consists of a diffuser, zebra strips, the LCD and a lens. The primary
function of the board is to drive a 112 x 16 graphic display and to drive the individual segment lines of
the LCD.
Serial display data from the microprocessor is sent to the LCD driver on the LCD panel. IIC DATA and
IIC CLK lines (Inter Integrated Circuit BUS) are pass through the zebra strips on the LCD driver. Another
function is to provide back lighting of the LCD module using for LED devices (D102). The diffuser
placed immediately above the LED evenly distributes the light.
Audio Processor
The Audio Processor U101 handles nearly all the audio functions in the PZ-S series radio. It has the audio
filter that operates the basic functions of radio, the Limiter, the Splatter Filter, the Compander and the
Scrambler. It can be controlled by microprocessor.
The main functions are as followings;
The amplifier and attenuator functions for Transmitting and Receiving signals
The Pre/De-emphasis circuitry is built-in.
The Compressor and Expander are built-in.
The Scrambler and De-scrambler of frequency inversion type (3.388 KHz) are built-in.
Max Deviation level adjustment is available.
The 12.5 / 25 KHz filter is built-in.
The CTCSS and DCS filter is built-in and the level adjustment is available.
EDACS & Conventional Modes RX Audio (sheet4)
For transmitting of PZ-S series radio, the microphone bias can be supplied to microphone through Q109,
R183 and R184 when pressing the PTT key button. When the VOX mode is activated, the bias can be
supplied automatically. The voice signal made through microphone is entered into audio processor chip.
(U101) In case of external speaker-microphone, the bias also can be supplied and generate EXT_PTT
signal to microprocessor.
The audio modulation signal is connect to the mod input of the VCO and sub-audible modulation signal is
connected to the reference oscillator. The sub-tone signal (CTCSS, DCS) also can be added in the audio
processor.

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For receiving PZ-S series radio, the IF signal put into audio processor chip. The audio signal is on the
output pin of the audio processor. The audio signal can be amplified byAudio amplifier chip.
The CTCSS tone and DCS codes are decoded on the audio processor and pass through the microprocessor,
Audio Amplifier (U59)
The audio amplifier (U104) operates speaker and the maximum power output is 1.5 Watts with 16 Ω
speaker. The earphone jack (J100, J102) is for using an external speaker microphone.
R/F SECTION
The RF section consists of the following circuits;
A frequency synthesizer for generating the transmit carrier frequency and the first mixer injection
frequency for the receive circuitry.
Transmit circuits
Receive circuits
DC voltage regulator circuits and TX/RX switch circuits
SYNTHESIZER CIRCUIT
The synthesizer circuit consists of the reference oscillator (VCTCXO, U303), PLL IC (U302), Loop-Filter,
and VCO.
The microprocessor controlled frequency synthesizer circuit generates all transmit and receive RF
frequencies for the PZ-S series radio. This circuit uses a Voltage Controlled Oscillator (VCO) operating
on the actual transmit frequency of 400 ~ 470 ㎒(136~ 174 ㎒for VHF model) during transmit and 45.3
㎒(21.4 ㎒for VHF band) below the actual receive frequency during the receive.
The PLL IC (U302) consists of the internal 19bit reference counter and the 19bit program divider, and is
controlled by MPU program. The PLL_EN, PLL_DATA and PLL_CLK signals program the synthesizer
circuit.

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Voltage Controlled Oscillator (VCO)
There are two kinds of Voltage Controlled Oscillator in the synthesizer circuit. One is the TX VCO which
generates the actual transmit frequency of 400 ~ 470 ㎒(136~ 470 ㎒for VHF model) during transmit
and the other is RX VCO which generates the 1st LO frequency of 354.7 ~ 414.7 ㎒(114.6~ 152.6 ㎒for
VHF model) during the receive. These two VCO is selected by the VCO_TX and VCO_RX signal from
the microprocessor.
When VCO_TX signal is High, it turns transistor Q66 on and the TX5V1 (5Vdc) is supplied to the
TX_VCO. TX VCO oscillates transmit frequency by C463, C415, C418, C419, L85, D76, and Q62. The
D77 (variable capacitor diode for modulation) and C412, C413, R452 play a role in maintain regular
audio modulation within the using frequency range. The TX VCO generates the actual transmit frequency
of 400 ~ 470 ㎒for UHF model and 136 ~174 ㎒for VHF model.
When VCO_RX signal is High, it turns transistor Q67 on and the RX5V1 (5Vdc) is supplied to the
RX_VCO. RX VCO oscillates transmit frequency by C458, C402, C404, C405, L81, D74. The RX VCO
generates the actual 1st local frequency of 354.7 ~ 414.7 ㎒for UHF model and 114.6 ~152.6 ㎒for
VHF model.
Q63 operates as an amplifier which amplifies the output signal of the VCO and operates as a buffer
amplifier which helps the stable operation of VCO. The output level from this amplifier is about –10dBm.
The output signal of the VCO fed through the local amplifier and TX pre amplifier. A control voltage
from the Loop Filter is applied to L78 and L79 and is used to control VCO frequency. The feedback for
the synthesizer circuit is taken from the C429. This signal connects though a band-pass Filter consisting
VCO
(TX / RX) Synthesizer
IC(U302)
Pre Amplifier
& Local
Amplifier
Loop
filter
VCTCXO
(U303)
PLL_EN, PLL_DARA, PLL_CLK
Voltage
Converter
TX5V1, RX5V1
RF+3.3
DC+5V
Audio/Tone
modulation

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of capacitor C431, C434, C432 and inductor L75. The output signal fed into the synthesizer IC and the
feedback signal level is –15dBm.
Transmitter modulation signal from Audio/Logic section is applied to R452, D77 and C413.
Reference Oscillator (U303)
Reference Oscillator U303 provides a reference frequency of 12.8 ㎒at ±2.5ppm (-30°C~+60°C) to
Phase-Locked-Loop circuit. The oscillator has modulation capability. Frequency is adjusted by the
FRE_CON signal from the D/A converter section of U101. The voltage is controlled by PC Tune program.
Charge Pump and Loop Filter
Synthesizer circuit outputs phase error signal between the desired frequency and feedback frequency from
the VCO section. This phase error signal fed through the internal charge pump circuit.
The low pass filter is used for Loop filter circuit to reduce the side band noise of reference frequency and
obtain a high signal-to-noise.
TRANSMITTER CIRCUIT
The transmitter section consists of a driver amplifier, final amplifier, power control circuit and transmitter
switch.
DriverAmplifier
The driver amplifier consists of driver buffer amplifier (Q74, Q71) and drive amplifier (Q72). Transmit
RF signal form the VCO feed to driver amplifier and amplified up to 37dB by the driver amplifier section.
The output signal fed through the final amplifier.
Final Amplifier
The final amplifier (Q73) can amplify the power output up to more than 5W. The Final Amplifier (Q73)
amplifies to make final power output of more than 37dBm. The drain of final amplifier is connected into
the battery voltage in order to obtain maximum power. The output signal is fed through D61 and low-pass
Filter section.
Power Control
The Power Control circuit allows the radio transmit power to be set between 2 watt and 4 watts. It keeps
the output power close to the set value in spite of variations in transmit frequency, battery voltage,

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temperature and load. To do this, the Power Control circuit maintains a steady power output level by APC.
The transmit output power is controlled by varying the power control voltage (DA_TXPOW). The output
transmit output power is monitored by D80 and produce a DC voltage. The Amplifier (U305) amplifies
only the difference between the forward power level and DA_TXPOW level. This signal play a role to
gate voltage driver amplifier (Q72) and final amplifier (Q73).
TX Switches
The antenna switch part separates TX from RX and when transmitting, it emits only the carrier through
antenna and removes the Spurious and Harmonic. TX and RX switching is operated by pin diodes D60,
D61 and D62. Regarding TX operation, if TX5V2V is supplied to D60, D61 and D62, the diodes will be
turn on and the carrier is emitted to Antenna. The RX direction is blocked by D62, and it protects the RX
part. When RX operation, TX5V2 will be OFF and D60 & D61 are blocked. The RX signal is entered into
the RX direction.
The output signal passes through the low pass filter (L55, L56, C57, C58, C501, C502, C503, C504,
C505, C506, C507, and C508) to remove of Spurious and Harmonic.
RECEIVER CIRCUIT
The dual conversion receive circuit consists of a receiver front end, a 45.3 ㎒1st IF (UHF model), 21.4
㎒1st IF (VHF model) and 455KHz 2nd IF and an FM detector. All audio processing and squelch
functions are accomplished on the Audio/Logic section.
Front End
The front-end circuit consists of low pass filter, tunable band-pass filter and low noise amplifier. A
desired RF is coupled from antenna to the main board through antenna connector. The 400 ~ 470 ㎒RF
receive frequency is passed through a low-pass filter and passed the transmit switch and tunable band-
pass filter (L61, L62. L67, L68, D64, D65, D68, D69). The frequency characteristic of tunable filter plays
a role in making rejection of low frequency by DA_BPF voltage.
RFAmplifier
RF amplifier Q200 provides typically +15dB of gain to the RF signal. The output of the RF amplifier is
coupled through tunable band-pass filter (U202). The center frequency of tunable band-pass filter is
controlled by DA_BPF. The output of band-pass filter connected to the input of mixer circuit (Q203).

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Local Oscillator Buffer
The injection frequency (354.7 ~ 414.7 ㎒) from the synthesizer circuit is applied to the base of LO buffer
transistor Q105. The output signal level is +3dBm and is connected to the input of mixer circuit (Q201).
Mixer
The RF signal from the front-end and the injection frequency from the LO buffer is connected to the input
of mixer(Q201), The mixer generates a 1st IF (UHF : 45.3 ㎒, VHF : 21.4 ㎒) signal on the output of the
mixer circuit (Q201). The signal level of VCO local frequency is 2dBm±2dBm and at this time, the
conversion gain is approximately 0dBm. The Mixer (Q13) uses n-channel dual gate MOS-FET in order to
prevent spurious harmonics.
The signal on the output of the mixer is applied to the 1st IF band-pass filter. The Crystal filter (XF31)
selects 1st IF frequency out of frequencies generated from the mixer part. The Crystal filter matching
circuit consists of L73, C257, C223, C208, and R209.
The crystal filter output is amplified by bipolar IF amp transistor Q54. The output signal of IF amplifier
connected through coupling capacitor C260 to the input of IF IC.
IF Detector circuit
The IF IC (U301) consists of the 2nd Mixer, the 12.5 / 25KHz ceramic filter, the Discriminator, and the
noise squelch circuit.
The 1st IF (UHF : 45.3 ㎒, VHF : 21.4 ㎒) signal is applied to an input of second mixer circuit (internal
U301) through coupling capacitor C260. A second Local injection frequency of 44.845 ㎒(VHF : 20.945
㎒) is internally applied to an other input of the mixer. This result in a second IF of 455 ㎑on the output
of the mixer. This signal pass through the 2nd IF filter (455 ㎑) to the internal IF amplifier. The
microprocessor selects the ceramic filter for the suitable channel spacing (12.5 ㎑or 25 ㎑) out of 2
ceramic filters. The W_CON signal is high, 25 ㎑ceramic filter is selected and N_CON signal is high,
12.5 ㎑ceramic filter is. Accordingly, the output of IF IC (pin#3) selects only the 12.5 ㎑signal
through F104 (25 ㎑ceramic filter) and F103 (12.5 ㎑ceramic filter).
When the channel spacing 12.5 ㎑and 25 ㎑are selected, Q55 and Q56 make the audio sound and the
noise squelch in the same level. The squelch is adjusted in 10 steps by supplying the noise voltage of
U301 (pin#14) to P2.6 A/D port of MPU (U51).