Motorola Cp200 Detailed 6880309n62 C Manual
Have a look at the manual Motorola Cp200 Detailed 6880309n62 C Manual online for free. It’s possible to download the document as PDF or print. UserManuals.tech offer 249 Motorola manuals and user’s guides for free. Share the user manual or guide on Facebook, Twitter or Google+.
6880309N62-CJune, 2005 465-495 MHz UHF Theory Of Operation: UHF Transmitter 10-3 10.3 UHF Transmitter The UHF transmitter covers the range of 465-495 MHz. Depending on model, the output power of the transmitter is either switchable on a per-channel basis between high power (4 watts) and low power (1 watt), or is factory preset to 2 watts. The transmitter is divided into four major blocks as shown in Figure 10-2. • Power Amplifier • Harmonic Filter • Antenna Matching Network • Power Control. Figure 10-2. UHF Transmitter Block Diagram 10.3.1 Transmitter Power Amplifier The transmitter power amplifier has three stages of amplification. The first stage, Q100, operates in Class A from the 5T source. It provides 17 dB of gain and an output of 50 mW. The current drain is typically 30mA. Components C105 and L103 match the output of Q100 to the 50Ω input of the module U110. U110 is a two stage Silicon MOS FET power amplifier module. Drain voltage is obtained from UNSW B+ after being routed through current-sense resistor R150 in the power control circuit. The output power of the module is controlled by varying the DC gate bias on U110 pin 2 (VGG). 10.3.2 Antenna Switch The antenna switch consists of two pin diodes, D120 and D121. In the receive mode, both diodes are off. Signals applied at the antenna or at jack J140 are routed, via the harmonic filter, through network C122-C124 and L121, to the receiver input. In the transmit mode, Q170 is on and TXB+ is present, forward-biasing both diodes into conduction. The diode current is 20 mA, set by R120-R121. The transmitter RF from U110 is routed through D120, and via the harmonic filter to the antenna jack. D121 conducts, shunting RF power and preventing it from reaching the receiver. L121 is selected to appear as a 1/4 wave at UHF, so that the low impedance of D121 appears as a high impedance at the junction of D120 and the harmonic filter input. This provides a high series impedance and low shunt impedance divider between the power amplifier output and receiver input. 10.3.3 Harmonic Filter The harmonic filter consists of components C130-C136 and L130-L132. The harmonic filter is a seven-pole Chebychev low-pass configuration, optimized for low insertion loss, with a 3 dB frequency of approximately 655 MHz and typically less than 0.8 dB insertion loss in the passband. Power Control Harmonic Filter Antenna Matching NetworkPower Amplifier Module U110Q100TX_INJ (From VCO)5TVDD VGG TX_ENA PWR_SET USWB+ RX_IN (To Receiver) Antenna SwitchJ140 Antenna Jack Antenna
June, 20056880309N62-C 10-4465-495 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry 10.3.4 Antenna Matching Network The harmonic filter presents a 50Ω impedance to antenna jack J140. A matching network, made up of C140-C141 and L140, is used to match the antenna impedance to the harmonic filter. This optimizes the performance of the transmitter and receiver into the impedance presented by the antenna, significantly improving the antennas efficiency. 10.3.5 Power Control The power control circuit is a dc-coupled amplifier whose output is the dc gate bias voltage (VGG) applied to the two stages of the RF power amplifier U110. The output power of the transmitter is adjusted by varying the setting of the power-set DAC contained in the ASFICcmp IC (DACG, U451 pin 6). This PWR_SET voltage is applied to U150 pin 3. Stage U150-2 compares the voltage drop across current sense resistor R150 to the voltage drop across resistor R151 caused by current flow through Q150, and adjusts its output (pin 7) to maintain equal voltages at pins 5 and 6. Thus the current flow through Q150, and hence its emitter voltage, is proportional to the current drawn by stage U110, which is in turn proportional to the transmitter output power. The emitter voltage of Q150 is applied to U150 pin 2, where it is compared to the power set voltage PWR_SET at pin 3. The output of U150 pin 1 is divided by R110 and R111 and applied as a gate voltage to the power amplifier U110. By varying this gate voltage as needed to keep the voltages at U150 pins 2 and 3 equal, power is maintained at the desired setting. Excessive final current, for example due to antenna mismatch, causes a lowering of the voltage at U150 pin 6, an increased voltage at pin 2, and a lowering of the voltage at pin 1 and of the gate voltage VGG. This prevents damage to the final stage due to excessive current. 10.4 UHF Frequency Generation Circuitry The frequency generation system, shown in Figure 10-3, is composed of two circuit blocks, the Fractional-N synthesizer IC U201, the VCO/Buffer IC U251, and associated circuitry. Figure 10-4 shows the peripheral interconnect and support circuitry used in the synthesizer block, and Figure 10- 5 details the internal circuitry of the VCOBIC and its interconnections to the surrounding components. Refer to the schematic to identify reference designators. The Fractional-N synthesizer is powered by regulated 5 V and 3 V provided by U310 and U330 respectively. 5 V is applied to U201 pins 13 and 30, and 3 V is applied to pins 5, 20, 34 and 36. The synthesizer in turn generates a super-filtered 4.5 V supply (VSF, from pin 28) to power U251. In addition to the VCO, the synthesizer also interfaces with the logic and ASFICcmp circuits. Programming for the synthesizer is accomplished through the microprocessor SPI_DATA_OUT,
6880309N62-CJune, 2005 465-495 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry 10-5 SPI_CLK, and SYNTH_CS (chip select) lines (U409 pins 100, 1 and 47 respectively). A logic high (3 V) from U201 pin 4 indicates to the microprocessor that the synthesizer is locked. Figure 10-3. UHF Frequency Generation Unit Block Diagram Transmit modulation from the ASFICcmp (U451 pin 40) is applied to U201 pin 10 (MOD_IN). An electronic attenuator in the ASFICcmp adjusts overall transmitter deviation by varying the audio level applied to the synthesizer IC. Internally the audio is digitized by the Fractional-N synthesizer and applied to the loop divider to provide the low-port modulation. The audio is also routed through an internal attenuator for the purpose of balancing the low port and high port modulation and reducing the deviation by 6 dB for 12.5 kHz channels, and is available at U201 pin 41 (VCO_MOD). This audio signal is routed to the VCOs modulator. 10.4.1 Fractional-N Synthesizer The Fractional-N synthesizer, shown in Figure 10-4, uses a 16.8 MHz crystal (Y201) to provide the reference frequency for the system. External components C201-C203, R202 and D201 are also part of the temperature-compensated oscillator circuit. The dc voltage applied to varactor D201 from U201 pin 25 is determined by a temperature-compensation algorithm within U201, and is specific to each crystal Y201, based on a unique code assigned to the crystal that identifies its temperature characteristics. Stability is better than 2.5 ppm over temperatures of -30 to 60°C. Software- programmable electronic frequency adjustment is achieved by an internal DAC which provides a frequency adjustment voltage from U201 pin 25 to varactor D201. The synthesizer IC U201 further divides the 16.8 MHz signal to 2.1 MHz, 2.225 MHz, or 2.4 MHz for use as reference frequencies. It also provides a buffered 16.8 MHz signal at U201 pin 19 for use by the ASFICcmp. To achieve fast locking of the synthesizer, an internal adapt charge pump provides higher current at U201 pin 45 to quickly force the synthesizer within lock range. The required frequency is then locked by the normal mode charge pump at pin 43. A loop filter (C243-C245 and R243-R245) removes noise and spurs from the steering voltage applied to the VCO varactors, with additional filtering located in the VCO circuit. Both the normal and adapt charge pumps get their supply from the capacitive voltage multiplier made up of C221-C224 and D220-D221. Two 3 V square waves from U201 pins 14-15 provide the drive signals for the voltage multiplier, which generates 12.1 V at U201 pin 47. This voltage is filtered by C225-C228. Synthesizer U201VCOBIC U251 Voltage Multiplier Loop Filter To Mixer To PA Driver VCP Vmult1 Vmult2Aux3 MOD Out Modulating SignalRx VCO Circuit Tx VCO Circuit TRB 16.8 MHz Ref. Osc. Rx Out Tx Out Buffer Q280
June, 20056880309N62-C 10-6465-495 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry One of the auxiliary outputs of the synthesizer IC (AUX3, U201 pin 2) provides the TRB signal which determines the operating mode of the VCO, either receive or transmit. Figure 10-4. UHF Synthesizer Block Diagram 10.4.2 Voltage Controlled Oscillator (VCO) The VCOBIC (U251), shown in Figure 10-5, in conjunction with the Fractional-N synthesizer (U201) generates RF in both the receive and the transmit modes of operation. The TRB line (U251 pin 19) determines which oscillator and buffer are enabled. A sample of the RF signal from the enabled oscillator is routed from U251 pin 12 through a low pass filter, to the prescaler input of the synthesizer IC (U201 pin 32). After frequency comparison in the synthesizer, a resultant DC control voltage is used to steer the VCO frequency. When the PLL is locked on frequency, this voltage can vary between 3.5 V and 10 V. L251 and C252 further attenuate noise and spurs on the steering line voltage. In the receive mode, the TRB line (U251 pin 19) is low. This activates the receive VCO and the receive buffer of U251, which operate within the range of 420.15 to 450.15 MHz. The VCO frequency is determined by tank inductor L254, C253-C257, and varactor D251. The buffered RF signal at U251 pin 8 is further amplified by Q280 and applied as RX_INJ to the low-pass injection filter in the receiver front end circuit. In the transmit mode, U251-19 is driven high by U201 pin 2, enabling the transmit VCO and buffer. The 465-495 MHz RF signal from U251 pin 10 is applied as TX_INJ to the input of the transmitter circuit via matching network C290-C291 and L291. TX VCO frequency is determined by L264, C263- DATA CLK CEX MODIN V CC, 5V XTAL1 WARP PREIN VCP Reference Oscillator Voltage Multiplier Voltage Controlled Oscillator 2-Pole Loop Filter DATA (U401 Pin 100) CLOCK (U401 Pin 1) SYNTH_CS (U401 Pin 47) MOD IN (U451 Pin 40) +5V (U310 Pin 5)7 8 9 10 13,30 23 25 32 47 VMULT2 VMULT1BIAS1 SFOUTAUX3 IADAPTIOUTGND FREFOUTLOCK4 19 6,22,23,24 43 45 2 28 141540Filtered 5VSteering Line LOCK (U401 Pin 56) Prescaler InLO RF Injection TX RF Injection (First Stage of PA) FREF (U451 Pin 34) 39 BIAS241 +3V (U330 Pin 5) V DD, 3VMODOUTU201 Low Voltage Fractional-N Synthesizer 5,20,34,36 TRB VCO Mod
6880309N62-CJune, 2005 465-495 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry 10-7 C267, and varactor D261. High-port audio modulation from the synthesizer IC is applied as VCO_MOD to varactor D262 which modulates the transmit VCO. Figure 10-5. UHF VCO Block Diagram Presc RX TX Matching Network Pin 8 Pin 14 Pin 103V (U330 Pin 5) VCC BuffersU201 Pin 32 AUX3 (U201 Pin 2) Prescaler Out Pin 12 Pin 19 Pin 20 TX/RX/BS Switching Network U251 VCOBIC Rx Active Bias Tx Active Bias Pin 2 Rx-I adjustPin 1 Tx-I adjustPins 9,11,17 Pin 18Vsens Circuit Pin 15 Pin 16 TX VCO Circuit TX TankRX VCO Circuit RX TankPin 7 Vcc-Superfilter Collector/RF in Pin 4 Pin 5 Pin 6RX TX V_SF (U201 Pin 28)NC NC Vcc-Logic 3V (U330 Pin 5) Steer Line Voltage (V_STEER) Pin 13 Pin 3 TRB_IN Buffer Q280 RX INJ V_SF (U201 Pin 28) TX INJ
June, 20056880309N62-C Notes: 10-8465-495 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry
Chapter 11 UHF Troubleshooting Tables 11.1 Troubleshooting Table for Receiver Table 11-1. Troubleshooting Table for Receiver Symptom Possible Causes Procedure Corrective Action Radio Dead (no turn-on beep, no LED indication)1. Battery dead or defec- tive.Substitute known good battery or battery eliminator.Charge or replace battery. 2. Defective batery con- tacts.Inspect battery contacts for corrosion or bent terminals.Clean/repair/replace J301. 3. Blown fuseCheck voltage on each side of fuse. If blown, 0 VDC after fuse.Check for short on output, check D301, VR301, trouble- shoot/repair as needed, replace fuse. 4. DC switching fault Verify battery voltage present at S444 pin 5 when radio is on. Verify Q494-1 is at least 1V dc, Q494-6 is ~0.1V dc, Q493-3 is at Vbatt.Check/replace on-off-volume control S444. Troubleshoot/replace Q493/4. 5. Microprocessor not starting up.Verify clock input to U401-90 (EXTAL) is 7.3975 MHz using high impedance probe. If clock is 3.8MHz, check for shorts on U401 pins. Con- nect RIB to verify communication via CPS. Verify U401-94 (RESET) is high.Verify 16.8 MHz signal at U451- 34. If OK, troubleshoot/replace U451. If not present, trouble- shoot U201 Synthesizer. Repro- gram/reflash as needed. If RESET is Low, troubleshoot regulator U320. Check for shorts at U401 pins. Replace U401 (depot only). Reprogram/ reflash as needed. 6. Regulator fault Verify U310-5 is 5V dc, U320-5 is 3.3V dc, U330-5 is 3V dc.Check for shorts on outputs, troubleshoot/repair as needed, replace faulty regulator.
June, 20056880309N62-C 11-2UHF Troubleshooting Tables: Troubleshooting Table for Receiver No Audio 1. Synthesizer out of lockVerify U201-4 is at 3V dc.Troubleshoot synthesizer/VCO circuits. 2. Defective IFIC Verify audio is present at U51-8. Check Q70, Y70, U51. 3. RX audio buffer faultVerify audio is present at U451-2.Check U510 and associated parts. 4. ASFIC fault Verify audio is present at U451-41. Verify U451-14 is high.Check squelch setting, PL/DPL programming. Troubleshoot/ replace U451. 5. Audio PA faultVerify U490-1 is
6880309N62-CJune, 2005 UHF Troubleshooting Tables: Troubleshooting Table for Synthesizer 11-3 11.2 Troubleshooting Table for Synthesizer Table 11-2. Troubleshooting Table for Synthesizer Symptom Possible Causes Procedure Corrective Action Synthesizer Out of Lock (RX mode only)1. VCO faultVerify oscillator is working, check RF level at U251-10 per schematic. Check dc voltages at U251 pin 2 through 6 and 10 per Table 11-4. Verify steering line voltage is between ~3V and 10V. Check VCO tank components connected to U251-5 and 6. Check for shorts/opens, replace U251. Check D251 and associated components. 2. Synthesizer fault Verify TRB line (from U201-2 to U251-19) is low in RX modeCheck for shorts, check U201 voltages per Table 11-4, replace U201 if incorrect. 3. Programming faultVerify RX channel programming is correct.Re-program if necessary. Synthesizer Out of Lock (TX mode only)1. VCO fault Verify oscillator is working, check RF level at U251-10 per schematic. Check dc voltages at U251 pins 1,3,4,10,15,16 per Table 11-4. Verify steering line voltage is between ~3V and 10V.Check VCO tank components connected to U251-15 and 16. Check for shorts/opens, replace U251. Check D261 and associated components. 2. Synthesizer faultVerify TRB line (U201-2 to U251-19) is high (3V) in TX modeCheck for shorts, check U201 voltages per Table 11-4, replace U201 if incorrect. 3. Programming fault Verify TX channel programming is correct.Re-program if necessary. Synthesizer Out of Lock (RX and TX modes) 1. VCO faultCheck that RF level at U251-12 is at least 150 mV (VHF) or -12 to -20 dBm (UHF)If low/missing, check L276, C276-7, R276. 2. Synthesizer fault Check that RF level at U201-32 is at least 150 mV (VHF) or -12 to -20 dBm (UHF). Verify steering line voltage is between ~3V and 10V.If correct, check/replace U201. If incorrect, check R248 and C241. Check loop filter components R243-5 and C243-5. 3. DC voltage faultVerify 4.5V dc at U201-28. Verify 12.1V dc at U201-47Check C231-233, etc., for shorts. If OK check/replace U201. Check for 3V 1.05 MHz sq waves at U201-14 and 15. Check C218-228, D220-221. 4. Programming fault Verify channel programming is cor- rect.Re-program if necessary.
June, 20056880309N62-C 11-4UHF Troubleshooting Tables: Troubleshooting Table for Transmitter 11.3 Troubleshooting Table for Transmitter Table 11-3. Troubleshooting Table for Transmitter Symptom Possible Causes Procedure Corrective Action No Transmit (no TX LED indication)1. PTT switch defective.Verify U401-71 goes low when PTT is pressed.Replace PTT switch S441. 2. EXT MIC PTT fault Verify U401-72 goes low when J471- 4 is grounded.Check/replace Q470, L471 etc. No Transmit (TX LED indication OK) 1. Synthesizer out of lockRefer to Table 11-2.Refer to Table 11-2. 2. No TX_ENABLE Verify U401-50 is high when pin 71 or 72 is low.Check/replace U401. 3. TX DC switch faultVerify Q171-C is 0V in TX. Verify Q170-C is at Vbatt in TX.Replace Q171. Check for shorts, replace Q170. 4. Power control fault Check Q150 and U150 dc voltages per schematic and Table 11-4.Repair/replace defective com- ponents 5. No TX injectionCheck that RF level at jct. R100/ R101 per schematic.Check U251, L291-292, C290- 291. 6. No 5T source Verify Q312 gate is 0V dc in TX Verify Q312 drain is 5V dc in TX.Check/replace Q313. Check for shorts, check/replace Q312. 7. TX gain stage failureCheck RF levels at Q100 and U110 per schematic.Troubleshoot Q100/U110 and associated circuitry. 8. Antenna switch failure Verify dc voltage at jct. R122/L120 is approx 1.5V.Check/replace D120-121, L120- 121, R120-122, etc. Low Power 1. Low TX injectionCheck that RF level at jct. R100/ R101 per schematic.Check U251, L291-292, C290- 291. 2. Low gain in TX stage Verify dc voltage at Q100-E is ~1.3V (VHF) or ~0.5V (UHF). Verify that RF level at U110-1 is approx. 1V (VHF) or 1.6V (UHF).Verify 5T voltage is correct. Troubleshoot Q100 circuitry. Troubleshoot Q100 circuitry. Check/replace Q100. 3. Incorrect control volt- ageVerify that the dc voltage at PWR_SET (R162) is approx 1.8V dc (at 1 watt) to 2.6V dc (at 4-5 watts). Verify that the dc voltage at U110-2 is approx 2-3V dc (at 1 watt) to 3-4V dc (at 4-5 watts). (See schematic.)Check programming. Trouble- shoot controller circuitry. Check/ replace U451. Troubleshoot U150, Q150 and associated circuitry. 4. Antenna switch defect Verify dc voltage at jct. R122/L120 (VHF) or R121/L120 (UHF) is approx 1.7V. Note: Do not attempt to mea- sure RF or DC voltages at the diodes. Damage to test equipment may occur.Check/replace D120-121, L120- 121, R120-122, etc. 5. Harmonic filter defectVisually inspect components C130- 137, L130-132. Check dc continuity of L130-132 in RX mode only.Repair/replace if necessary.