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Motorola Radius Cm200 Cm300 Pm400 Detailed 6881098c00 A Manual

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    							Technical Specifications1-3
    *Availability subject to the laws and regulations of individual countries.
    Transmitter
    Specification UHF2
    Power Output1-25W
    Conducted/Radiated 
    Emissions:-36 dBm < 1 GHz 
    -30 dBm > 1 GHz
    Audio Response: (from 6 dB/
    oct. Pre-Emphasis, 300 to 
    3000Hz)
    TIA603 and CEPT
    Tx Audio Distortion < 3%
    Modulation Limiting:±2.5 kHz @ 12.5 kHz
    ±4.0 kHz @ 20 kHz
    ±5.0 kHz @ 25 kHz
    FM Hum and Noise: -35 [email protected] kHz
    -40 dB@25 kHz
    Receiver
    Specification UHF2
    Sensitivity (12 dB SINAD):0.35 μV @ 12.5 kHz
    0.3 μV @ 25 kHz
    Intermodulation: 60 [email protected] kHz 
    70 dB@25 kHz 
    Adjacent Channel Selectivity:60 dB @ 12.5 kHz 
    70 dB @ 25 kHz 
    Spurious Response 70 dB 
    Rated Audio Power4 W (typ.) Internal
    7.5 W @ 5 % External
    Audio Distortion < 5 %
    Hum and Noise:-35 dB @ 12.5 kHz
    -40 dB @ 25 kHz
    Audio Response TIA603 and CEPT
    Conducted Spurious Emission 
    per FCC Part 15:-57 dBm 1 Ghz
    Specifications subject to change without notice. All electrical specifications and methods 
    refer to EIA/TIA 603 standards.  
    						
    							1-4 MODEL CHART AND TECHNICAL SPECIFICATIONS
    Notes 
    						
    							Chapter 2
    THEORY OF OPERATION
    1.0 Introduction
    This Chapter provides a detailed theory of operation for the UHF circuits in the radio. Details of the 
    theory of operation and trouble shooting for the the associated Controller circuits are included in this 
    Section of the manual.
    2.0 UHF (438-470 MHz) Receiver
    2.1 Receiver Front-End
    The received signal is applied to the radio’s antenna input connector and routed through the 
    harmonic filter and antenna switch. The insertion loss of the harmonic filter/antenna switch is less 
    than 1 dB. The signal is routed to the first filter (4-pole), which has an insertion loss of 2 dB typically. 
    The output of the filter is matched to the base of the LNA (Q303) that provides a 16 dB gain and a 
    noise figure of better than 2 dB. Current source Q301 is used to maintain the collector current of 
    Q303. Diode CR301 protects Q303 by clamping excessive input signals. Q303 output is applied to 
    the second filter (3-pole) which has an insertion loss of 1.5 dB. In Distance mode, Q304 turns on and 
    causes D305 to conduct, thus bypassing C322 and R337. In Local mode, the signal is routed 
    through C322 and R337, thus inserting 7 dB attenuation. Since the attenuator is located after the RF 
    amplifier, the receiver sensitivity is reduced only by 6 dB, while the overall third order input intercept 
    is raised. 
    The first mixer is a passive, double-balanced type, consisting of T300, T301 and U302. This mixer 
    provides all of the necessary rejection of the half-IF spurious response. Low-side injection at 
    +15 dBm is delivered to the first mixer. The mixer output is then connected to a duplex network 
    which matches its output to the XTAL filter input (FL300) at the IF frequency of 44.85 MHz. The 
    duplex network terminates into a 50 ohm resistor (R340) at all other frequencies.
    Figure 2-1 UHF Receiver Block Diagram
    Mixer
    Xtal Filter
    Controller Front Filter Antenna
    First LO
    2nd LO Xtal Osc
     IF AmpSecond Filter4- Pole
    25 kHzFilter12.5 kHzFilter
    Phase Shift 
    Element IFIC LNA
    25 kHzFilter
    12.5 kHzFilter 
    						
    							2-2THEORY OF OPERATION
    2.2 Receiver Back End
    The IF signal from the crystal filter enters the IF amplifier which provides 20 dB of gain and feeds 
    the IF IC at pin 1. The first IF signal at 44.85 MHz mixes with the second local oscillator (LO) at 
    44.395 MHz to produce the second IF at 455 kHz. The second LO uses the external crystal Y301. 
    The second IF signal is amplified and filtered by two external ceramic filters (FL303/FL302 for 
    12.5 kHz channel spacing and FL304/FL301 for 25 kHz channel spacing). The IF IC demodulates 
    the signal by means of a quadrature detector and feeds the detected audio (via pin 7) to the audio 
    processing circuits. At IF IC pin 5, an RSSI signal is available with a dynamic range of 70 dB.
    3.0 UHF Transmitter Power Amplifier (438-470 MHz)
    The radio’s 25W PA is a three-stage amplifier used to amplify the output from the VCOBIC to the 
    radio transmit level. All three stages utilize LDMOS technology. The gain of the first stage (U101) is 
    adjustable and controlled by pin 7 of U103-2 via U103-3. It is followed by an LDMOS stage Q105 
    and LDMOS final stage Q100.
    Figure 2-2 UHF Transmitter Block Diagram
    Devices U101, Q105 and Q100 are surface mounted. A metal clip ensures good thermal contact 
    between both the driver and final stage, and the chassis.
    3.1 First Power Controller Stage
    The first stage (U101) is a 20 dB gain integrated circuit containing two LDMOS FET amplifier 
    stages. It amplifies the RF signal from the VCO (TX_INJ). The output power of stage U101 is 
    controlled by a DC voltage applied to pin 1 from the op-amp U103-3, pin 8. The control voltage 
    simultaneously varies the bias of two FET stages within U101. This biasing point determines the 
    overall gain of U101 and therefore its output drive level to Q105, which in turn controls the output 
    Loop
    Pin Diode 
    Antenna 
    Switch
    RF JackAntenna
    Harmonic 
    Filter
    CouplerPA - F i n a lStage
    From VCO
    ControlledSta ge
    Bias 
    Temperature
    Sense SPI BUSASFIC_CMP
    PA
    PWR
    SET
    PA
    Driver
    Controller
    U103-2Forward  
    						
    							UHF Transmitter Power Amplifier (438-470 MHz) 2-3
    power of the PA.Op-amp U103-3 monitors the drain current of U101 via resistor R122 and adjusts 
    the bias voltage of U101.
    In receive mode, the DC voltage from RX_EN line turns on Q101, which in turn switches off the 
    biasing voltage to U101.
    3.2 Power Controlled Driver Stage
    The next stage is an LDMOS device (Q105) which provides a gain of 12 dB. This device requires a 
    positive gate bias and a quiescent current flow for proper operation. The bias is set during transmit 
    mode by the drain current control op-amp U102-1, and fed to the gate of Q105 via the resistive 
    network R175, R147.
    Op-amp U102-1 monitors the drain current of Q105 via resistors R126-8 and adjusts the bias 
    voltage of Q105.
    In receive mode the DC voltage from RX_EN line turns on Q102, which in turn switches off the 
    biasing voltage to Q105.
    3.3 Final Stage
    The final stage is an LDMOS device (Q100) providing a gain of 12 dB. This device also requires a 
    positive gate bias and a quiescent current flow for proper operation. The voltage of the line PA_BIAS 
    is set in transmit mode by the ASFIC and fed to the gate of Q100 via the resistive network R134, 
    R131. This bias voltage is tuned in the factory. If the transistor is replaced, the bias voltage must be 
    tuned using the Tuner. Care must be taken not to damage the device by exceeding the maximum 
    allowed bias voltage. The device’s drain current is drawn directly from the radio’s DC supply voltage 
    input, B+, via L117 and L115.
    A matching network consisting of C1004-5, C1008, C1021: and two striplines, transforms the 
    impedance to 50 ohms and feeds the directional coupler.
    3.4 Directional Coupler
    The directional Coupler is a microstrip printed circuit, which couples a small amount of the forward 
    power of the RF power from Q100.The coupled signal is rectified to an output power which is 
    proportional to the DC voltage rectified by diode D105; and the resulting DC voltage is routed to the 
    power control section to ensure that the forward power out of the radio is held to a constant value.
    3.5 Antenna Switch
    The antenna switch utilizes the existing dc feed (B+) to the last stage device (Q100). The basic 
    operation is to have both PIN diodes (D103, D104) turned on during key-up by forward biasing 
    them. This is achieved by pulling down the voltage at the cathode end of D104 to around 12.4 V (0.7 
    V drop across each diode). The current through the diodes needs to be set around 100 mA to fully 
    open the transmit path through resistor R108. Q106 is a current source controlled by Q103 which is 
    turned on in Tx mode by TX_EN. VR102 ensures that the voltage at resistor R107 never exceeds 
    5.6 V. 
    						
    							2-4THEORY OF OPERATION
    3.6 Harmonic Filter
    Inductors L111 and L113 along with capacitors C1011, C1023, C1020 and C1016 form a low-pass 
    filter to attenuate harmonic energy coming from the transmitter. Resistor R150 along with L126 
    drains any electrostatic charges that might otherwise build up on the antenna. The harmonic filter 
    also prevents high level RF signals above the receiver passband from reaching the receiver circuits 
    to improve spurious response rejection.
    3.7 Power Control
    The output power is regulated by using a forward power detection control loop. A directional coupler 
    samples a portion of the forward and reflected RF power. The forward sampled RF is rectified by 
    diode D105, and the resulting DC voltage is routed to the operational amplifier U100. The error 
    output current is then routed to an integrator, and converted into the control voltage. This voltage 
    controls the bias of the pre-driver (U101 and driver (Q105) stages. The output power level is set by 
    way of a DAC, PWR_SET, in the audio processing IC (U504) which acts at the forward power 
    control loop reference.
    The sampled reflected power is rectified by diode D107,The resulting DC voltage is amplified by an 
    operational amplifier U100 and routed to the summing junction. This detector protects the final stage 
    Q100 from reflected power by increasing the error current. The temperature sensor protects the 
    final stage Q100 from overheating by increasing the error current. A thermistor RT100 measures the 
    final stage Q100 temperature. The voltage divider output is routed to an operational amplifier U103 
    and then goes to the summing junction. The Zener Diode VR101 keeps the loop control voltage 
    below 5.6 V and eliminates the DC current from the 9.3 regulator U501. 
    Two local loops for the Pre Driver (U101) and for the Driver (Q105) are used in order to stabilize the 
    current for each stage.
    In Rx mode, the two transistors Q101 and Q102 go to saturation and shut down the transmitter by 
    applying ground to the Pre Driver U101 and for the Driver Q105 control.
    4.0 UHF (438-470 MHz) Frequency Synthesis
    The synthesizer consists of a reference oscillator (Y201), low voltage Fractional-N (LVFRAC-N) 
    synthesizer (U200), and a voltage controlled oscillator (VCO) (U201).
    4.1 Reference Oscillator
    The reference oscillator is a crystal (Y201) controlled Colpitts oscillator and has a frequency of 
    16.8 MHz. The oscillator transistor and start-up circuit are located in the LVFRAC-N (U200) while 
    the oscillator feedback capacitors, crystal, and tuning varactors are external. An analog-to-digital (A/
    D) converter internal to the LVFRAC-N (U200) and controlled by the microprocessor via SPI sets the 
    voltage at the warp output of U200 pin 25. This sets the frequency of the oscillator. Consequently, 
    the output of the crystal Y201 is applied to U200 pin 23.
    The method of temperature compensation is to apply an inverse Bechmann voltage curve, which 
    matches the crystal’s Bechmann curve to a varactor that constantly shifts the oscillator back on 
    frequency. The crystal vendor characterizes the crystal over a specified temperature range and 
    codes this information into a bar code that is printed on the crystal package. In production, this 
    crystal code is read via a 2-dimensional bar code reader and the parameters are saved. 
    						
    							UHF (438-470 MHz) Frequency Synthesis2-5
    This oscillator is temperature compensated to an accuracy of +/-2.5 PPM from -30 to 60 degrees C. 
    The temperature compensation scheme is implemented by an algorithm that uses five crystal 
    parameters (four characterize the inverse Bechmann voltage curve and one for frequency accuracy 
    of the reference oscillator at 25 degrees C). This algorithm is implemented by the LVFRAC-N (U200) 
    at the power up of the radio.
    TCXO Y200, along with its corresponding circuitry R204, R205, R210, and C2053, are not placed as 
    the temperature compensated crystal proved to be reliable.
    4.2 Fractional-N Synthesizer
    The LVFRAC-N U200 consists of a pre-scaler, programmable loop divider, control divider logic, 
    phase detector, charge pump, A/D converter for low frequency digital modulation, balanced 
    attenuator used to balance the high and low frequency analog modulation, 13 V positive voltage 
    multiplier, serial interface for control, and a super filter for the regulated 5 volts.
    Figure 2-3 UHF Synthesizer Block Diagram
    A voltage of 5 V applied to the super filter input (U200, pin 30) supplies an output voltage of 4.5 Vdc 
    (VSF) at U200, pin 28. This supplies 4.5 V to the VCO Buffer IC U201.
    To generate a high voltage to supply the phase detector (charge pump) output stage at pin VCP 
    (U200, pin 47) while using a low voltage 3.3 Vdc supply, a 13 V positive voltage multiplier is used 
    (D200, D201, and capacitors C2024, 2025, 2026, 2055, 2027, 2001).
    Output lock (U200, pin 4) provides information about the lock status of the synthesizer loop. A high 
    level at this output indicates a stable loop. A 16.8 MHz reference frequency is provided at U200, pin 
    19.
    DATA
    CLK
    CEX
    MODIN
    VCC, DC5V
    XTAL1
    XTAL2
    WARP
    PREIN
    VCP
    REFERENCE
    OSCILLATOR
     VOLTAGE
    MULTIPLIER
    DATA (U403 PIN 100)
    CLOCK (U403 PIN 1)
    CSX (U403 PIN 2)
    MOD IN (U501 PIN 40)
    +5 V (U503 PIN 1)7
    8
    9
    10
    13, 30
    23
    24
    25
    32
    47
    VMULT2 VMULT1BIAS1 SFOUTAUX3 AUX4 IADAPTIOUTGND FREFOUTLOCK4
    19
    6, 22, 33, 44
    43
    45
    3
    2
    28
           14
            1540FILTERED 5VSTEERING LOCK (U403 PIN 56)
    PRESCALER INFREF (U504 PIN 34)
    39 BIAS2
    41
     48 5, 20, 34, 36
    +5 V (U503 PIN 1)
    AUX1 VDD, DC5VMODOUT
    U200 
    LOW VOLTAGEFRACTIONAL-N
    SYNTHESIZER
    AUX21 (NU)
    BWSELECTVCO Bias
    TRB
    To IF
    SectionTX RF INJECTION
    (1ST STAGE OF PA)LO RF INJECTION
    VOLTAGE 
    CONTROLLED 
    OSCILLATORLINE
    LOOP
    FILTER 
    						
    							2-6THEORY OF OPERATION
    4.3 Voltage Controlled Oscillator (VCO)
    The Voltage Controlled Oscillator (VCO) consists of the VCO/Buffer IC (VCOBIC, U201), the TX and 
    RX tank circuits, the external RX buffer stages, and the modulation circuitry.
    Figure 2-4 UHF VCO Block Diagram
    The VCOBIC together with the LVFRAC-N (U200) generate the required frequencies in both 
    transmit and receive modes. The TRB line (U201, pin 19) determines which VCO and buffer is 
    enabled (high being TX output at pin 10, low being RX output at pin 8). A sample of the signal from 
    the enabled output is routed from U201, pin 12 (PRESC_OUT), via a low pass filter to U200, pin 32 
    (PREIN). 
    A steering line voltage between 3.0 V and 10.0 V at varactor D204 tunes the TX VCO through the 
    frequency range of 438-470 MHz, and at D203 tunes the RX VCO through the frequency range of 
    393.15-425.15 MHz.
    The external RX amplifier is used to increase the output from U201, pin 9 from 3-4 dBm to the 
    required 15 dBm for proper mixer operation. In TX mode, the modulation signal from the LVFRAC-N 
    (U200, pin 41) is applied to the VCO by way of the modulation circuit D205, R212, R211, C2073.
     
    Presc
    RX
    TXBuffersQ200
    Low Pass
        Filter
    Attenuator Pin8
    Pin14
    Pin10(U200 Pin28)
    VCC Buffers
    TX RF Injection U200 Pin 32 AUX3 (U200 Pin 2)
    Prescaler Out
    Pin 12 Pin 19 Pin 20
          TX/RX/BS
    Switching Network
    U201
    VCOBIC
           Rx
    Active Bias
          Tx
    Active Bias
    Pin2
    Rx-I adjustPin1
    Tx-I adjustPins 9,11,17
    Pin18Vsens
    Circuit Pin15Pin16 RX VCO
     Circuit
    TX VCO
     Circuit RX Tank
    TX TankPin7
    Vcc-Superfilter
    Collector/RF in
    Pin4
    Pin5
    Pin6RX
    TX
    (U200 Pin 28)Rx-SW
    Tx-SW
    Vcc-Logic
    (U200 Pin 28) Steer Line 
    Voltage 
    (VCTRL)Pin13
    Pin3TRB IN
    LO RF INJECTION 
    						
    							UHF (438-470 MHz) Frequency Synthesis2-7
    4.4 Synthesizer Operation
    The synthesizer consists of a low voltage FRAC-N IC (LVFRAC-N), reference oscillator, charge 
    pump circuits, loop filter circuit, and DC supply. The output signal (PRESC_OUT) of the VCOBIC 
    (U201, pin 12) is fed to the PREIN, pin 32 of U200 via a low pass filter which attenuates harmonics 
    and provides a correct input level to the LVFRAC-N in order to close the synthesizer loop.
    The pre-scaler in the synthesizer (U200) is a dual modulus pre-scaler with selectable divider ratios. 
    The divider ratio of the pre-scaler is controlled by the loop divider, which in turn receives its inputs 
    via the SPI. The output of the pre-scaler is applied to the loop divider. The output of the loop divider 
    is connected to the phase detector, which compares the loop divider’s output signal with the 
    reference signal. The reference signal is generated by dividing down the signal of the reference 
    oscillator (Y201).
    The output signal of the phase detector is a pulsed dc signal that is routed to the charge pump. The 
    charge pump outputs a current from U200, pin 43 (IOUT). The loop filter (consisting of R224, R217, 
    R234, C2074, C2075, C2077, C2078, C2079, C2080, C2028, and L205) transforms this current into 
    a voltage that is applied the varactor diodes D203 and D204 for RX and TX respectively. The output 
    frequency is determined by this control voltage. The current can be set to a value fixed in the 
    LVFRAC-N or to a value determined by the currents flowing into BIAS 1 (U200, pin 40) or BIAS 2 
    (U200, pin 39). The currents are set by the value of R200 or R206 respectively. The selection of the 
    three different bias sources is done by software programming. 
    To modulate the synthesizer loop, a two-spot modulation method is utilized via the MODIN (U200, 
    pin 10) input of the LVFRAC-N. The audio signal is applied to both the A/D converter (low frequency 
    path) and the balance attenuator (high frequency path). The A/D converter converts the low 
    frequency analog modulating signal into a digital code which is applied to the loop divider, thereby 
    causing the carrier to deviate. The balance attenuator is used to adjust the VCO’s deviation 
    sensitivity to high frequency modulating signals. The output of the balance attenuator is presented 
    at the MODOUT port of the LVFRAC-N (U200,pin 41) and connected to the VCO modulation 
    varactor D205. 
    						
    							2-8THEORY OF OPERATION
    5.0 Controller Theory of Operation
    This section provides a detailed theory of operation for the radio and its components. The main 
    radio is a single-board design, consisting of the transmitter, receiver, and controller circuits. A 
    control head is connected by an extension cable. The control head contains LED indicators, a 
    microphone connector, buttons, and speaker. 
    In addition to the power cable and antenna cable, an accessory cable can be attached to a 
    connector on the rear of the radio. The accessory cable enables you to connect accessories to the 
    radio, such as an external speaker, emergency switch, foot-operated PTT, and ignition sensing, etc.
    Figure 2-5 Controller Block Diagram 
    5.1 Radio Power Distribution
    Voltage distribution is provided by five separate devices:
    • U514 P-cH FET - Batt + (Ext_SWB+)
    • U501 LM2941T - 9.3 V
    • U503 LP2951CM - 5 V
    • U508 MC 33269DTRK - 3.3 V
    • U510 LP2986ILDX - 3.3 V Digital
    External
    Microphone
    Internal
    Microphone
    External
    Speaker
    Internal
    Speaker
    SCI to
    Control Head Audio
     PA Audio/Signaling
       Architecture To Synthesizer
    Mod
    Out
    16.8 MHz
    Reference Clock
    from Synthesizer
    Disc Audio
    To RF SectionSPI
        Digital
    ArchitectureµP Clock
       3.3 V
    RegulatorRAM
    EEPROM
    FLASHHC11FL0 ASFIC_CMP
    Accessory &  
    Connector
    Handset
    . 
    						
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