FCC ID: ASLMTX5 Leisure Marine Radar

Technical Description Note This Technical Description is part of the Pathfinder Radar/Chartplotter series Service Manual and includes both the 4kW, 48" Open Array Scanner Unit and the 10kW, 48" Open Array Scanner Unit. Raytheon Marine Company, Recreational Products, Portsmouth, England

Chapter 2. Technical Description Chapter 2. Technical Description 2.1 Overview Scanner configuration Antenna/Rotary joint assembly Motor 4kW/10kW Magnetron Transition Circulator

-20dB (nominal) 60dBm (maximum) W/Guide limiter Low Noise Converter Modulator, PSU board IF Receiver, micro, I/O board Ships power Scanner uplink connection D4595-2 Figure 1. Scanner Block Diagram The system comprises the functional blocks as shown in the above diagram. The basis of operation is as follows:

The Modulator, PSU board generates a high voltage pulse of between 65ns and 1.2us duration

(1.0us maximum for 4kW unit) dependant upon the range setting and the corresponding IF/Video filter control lines. This pulse begins on the rising edge of a negative going trigger at a pulse repetition frequency (PRF) also defined by the range setting. The resulting pulse is output to the magnetron which converts the energy into an RF pulse at a frequency of 9.41GHz (nominal). All supply requirements are also provided by the Modulator, PSU board. The RF pulse is routed to an antenna via a 3-port circulator which propagates microwave energy in only one direction and thereby provides isolation between the transmit source and the low noise converter. Note that the circulator for the 10kW system incorporates a waveguide diode limiter to reduce the power entering the receiver. A rotary joint is used to maintain continuity between a waveguide output from the circulator and a coaxial input to the antenna. The energy is then radiated, with a narrow azimuth beam shape (1.85 for the 48" antenna), with low sidelobe levels (<-22dB). The elevation beamwidth is maintained at approximately 25 in order to illuminate targets during pitch and roll of the transmitting vessel. 5 t r a P 2 r e t p a h C Echoes are returned due to reflections from potential targets such as boats, buoys, land etc, and in the form of clutter from sea, rain, etc. The returned energy is collected by the same antenna used to transmit the original pulse and is routed through the circulator to the low noise converter (LNC). These comparatively low level signals are amplified by a low noise transistor in order to maintain signal/noise performance and are mixed down to an IF frequency of 60MHz nominal for further amplification and subsequent detection. Service Manual 83147-2-Ch2 3 Pathfinder Radar/Chartplotter Series The IF receiver board provides further low noise amplification and adjustable gain to maximise the dynamic range (dynamic attenuation control) in the presence of clutter, target and range variations. The IF board also includes a logarithmic detection stage with approximately 50dB dynamic range, which provides a compressed signal output in terms of dB input power versus output Voltage level. Various filtering stages are also employed in the IF Receiver to provide optimum signal/noise characteristics for the detected pulse and to provide some immunity against the bulk effects of rain. The IF Receiver also provides the interface for the up-link commands to the scanner, including clutter and gain selection, 3-phase motor control and display synchronisation pulse generation. Receiver configuration (LNC/IF) The basic configuration of the microwave and IF receiver circuitry is as follows :

Low Noise Converter (LNC) IF Receiver Board Filter select logic Limiter LNA Switched Filter Logarithmic Detector Video Filter 90 HYB 90 deg Lineariser Lineariser Autotune Receiver Curve Splitter LNC Supplies MBS / STC / Rain / Sea / Gain Generation and Summing Network Scanner uplink D4055-1 Figure 2. Receiver Configuration (LNC/IF) Low Noise Converter/Limiter (LNC) The primary function of the LNC is to provide low noise amplification of the low level signal returns and mixing to an IF frequency of 60MHz nominal. 5 t r a P 2 r e t p a h C The low noise amplification is provided by a single low noise FET, with bias conditions, and associated matching set to minimise noise figure and maximise gain and compression levels. Maximum gain is required so as to minimise the noise figure contribution from subsequent stages. The mixing function is carried out in an image reject mixer configuration which reduces image noise by 20dB nominal in order to minimise the degradation in overall noise figure. Protection is provided in the form of three limiter diodes which are configured to become forward biased in the presence of increasing RF power. Note that the ciculator for the 10kW system also incorporates a waveguide diode limiter. NOTE. There are no user / dealer serviceable parts within the LNC due to its high frequency of operation. 4 Service Manual 83147-2-Ch2 Chapter 2. Technical Description m W I/P Limiter

+5Volts

-5Volts Ground Constant current bias circuitry VCO tune compensation Figure 3. LNC Configuration Scanner Disable Switch Ships Supply Display Unit Tune_V 60MHZIF 90 HYB LNA Mixer 90 degrees D4056-1 LNC P7 IF Receiver P1 P2 P4 Ship's Heading Sensor CN7 CN2 CN5 CN11 CN9 CN8 CN10 JP1 Modulator/PSU/Motor CN3 CN6 CN2 IF Inter-connect CN3 3-Phase Motor CN5 Ships Header Transducer CN6 Magnetron CN7 IF Display Interface Inter-connect CN8 Display Inter-connect CN9 Scanner Disable Switch CN10 Ships Power CN11 Cooling Fan (10 kW only) JP1 Service Motor enable Jumper Note: CN3, CN5, CN8, CN9, CN10, JP1 are fitted to non-component side to give access to the installer. 3-Phase Motor Magnetron Figure 4. Scanner Interfaces D4648-2 5 t r a P 2 r e t p a h C Service Manual 83147-2-Ch2 5 Pathfinder Radar/Chartplotter Series 2.2 Modulator / PSU Interface Description The interfaces to the Mod/PSU are shown in Figure 4. and the individual signal functions are described below :-

Ship Supply Power Input (CN10) Ref. Signal Name Type State Function

+V_SHIP Power input Ships power i/p V_SHIP Power input Ships power return CN10-7 CN10-8 CN1-1 CN1-2 Modulator Control/Status (CN2) Ref. Signal Name Type State Function CN2-18 RADAR_TX_EN Logic input CN2-9 CN2-11 PW0, PW1 Logic input Logic input CN2-16 PW_ADJUST Analogue input Analogue voltage adjusts fine transmit pulse width. CN2-13 PTX_ADJUST Analogue input Analogue voltage adjusts modulator transmit power. CN2-8 PRI_PLS Logic input CN2-3 HEATER_OK Logic output CN2-17 MOD_ISENSE Analogue output 0-5.0V 1 0 1 0 (default) PW0 PW1 0 1 0 1 0 0 1 1 0-5.0V 0-5.0V clock 1/PRF or PRI Enable modulator (magnetron) pulses Disable modulator, regardless of activity on PRI_PLS Select course modulator pulse width as follows :-

Short pulse range Medium pulse range Long pulse range Very long pulse range 10us+/-0.5us low. Rising edge triggers modulator pulse. Frequency will be varied according to pulse width. See Figure 5 and Table 1in Section 2.3. Indicates magnetron heater is connected and drawing correct current. Magnetron heater faulty or magnetron disconnected. Indicates peak magnitude of magnetron anode current and thus indicates approximately peak R.F. power output. See Section 3.6 and Table 1in Section 2.3. 3-5V 0-0.5V D4059-2 For 3-phase motor: Output at approximately 590Hz confirms that correct rotational speed of 24 RPM has been obtained. For all build standards this line acts to identify the type of build standard in conjunction with the MOTOR_EN_N control as follows:

When MOTOR_EN_N=1 (motor = off) STEP_IO = 0 for 3-phase motor build standard. 10us _+ 0.5us PRI_PLS 5 t r a P 2 r e t p a h C Figure 5. Modulator clock format, PRI_PLS Motor Control Ref. Signal Name Type State Function CN2-12 MOTOR_EN_N Logic input 0 1 Enable Motor (3-phase) Disable Motor CN2-10 STEP_IO Logic input/output clock 6 Service Manual 83147-2-Ch2 Chapter 2. Technical Description Ships Heading Interface Ref. Signal Name Type Function CN2-15 SHP_IN Logic output State clock Negative going edge: Indicates antenna position is at nominal zero azimuth. This corresponds to a point just before the antenna reaches the forward facing position. Receiver Power Supply Signal Name State Function

-5V power rail to receiver

+5V power rail to receiver

+26V power rail to receiver

+12V power rail to receiver Isolated GND return from receiver power rails Phase 3 output Phase 2 output Phase 1 output Hall-effect phase 3 input Hall-effect phase 3 input Hall-effect phase 3 input

+12V Motor Hall-effect switch power rail 0V Motor Hall-effect switch power return & signal reference 3-Phase D.C. Brushless Motor Interface Note: These signals are referenced to the ships battery negative. Signal Name Type State Function IF-5V IF+5V IF+26V IF+12V GND GND L3 L2 L1 RLG3 RLG2 RLG1

+HALL H0V Ref. CN2-1 CN2-2 CN2-4 CN2-6 CN2-5 CN2-7 Ref. CN3-5 CN3-6 CN3-7 CN3-3 CN3-2 CN3-1 CN3-8 CN3-4 Ref. CN5-1 CN5-2 CN5-3 CN5-4 Type Power Power Power Power Power Analogue output Analogue output Analogue output Logic input Logic input Logic input Power Power

Ships Heading Sensor Hall Switch Interface Signal Name Type State Function B_ZERO SH+V SH_GND SH_GND Analogue Power Power Power Magnetron Interface Ships Heading Hall transducer open collector output

+12V power to Ships Heading Hall transducer. Ships Heading Hall transducer GND connection Ships Heading Hall transducer GND connection 5 t r a P 2 r e t p a h C Ref. Signal Name Type State Function CN6-1 HEATER Analogue output Magnetron heater power and signal cathode connection. CN6-2 HEAT/CATH Analogue output Magnetron heater power return and signal connection Note: The magnetron anode connection is made through the body of the device to the chassis GND. Service Manual 83147-2-Ch2 7 Pathfinder Radar/Chartplotter Series IF-Display Interconnect Signal Name Type State Function AZ_SHP_OUTB Diff. Pair #1output RS485 Azimuth/Ship Heading Pulses Diff. Pair #2 i/o RS485 Bi-directional data and control Diff. Pair #3 output RS485 Transmit, PRI, pulse data Logic i/o Not Used. Spare GND IF GND to video coax screen Analogue output Video to coax inner CN7-10 GND GND IF GND Display Interconnect These signals are filtered versions of the above. Signal Name Type State Function Diff. Pair #1output RS485 Azimuth/Ship Heading Pulses Ref. CN7-1 CN7-2 CN7-3 CN7-4 CN7-5 CN7-6 CN7-7 CN7-8 CN7-9 Ref. CN8-1 CN8-2 CN8-3 CN8-4 CN8-5 CN8-6 CN8-7 CN8-8 AZ_SHP_OUT SER_IOB SER_IO PRI_OUTB PRI_OUT SPARE GND VIDEO Az-

Az+

Data-

Data+

Pri-

Pri+

GND Vid Diff. Pair #2 i/o RS485 Bi-directional data and control Diff. Pair #3 o/p RS485 Transmit, PRI, pulse data GND IF GND / to video coax screen Analogue output Video to coax inner Scanner Disable Switch Note: These signals are referred to the ship's battery negative. Ref. Signal Name CN9-1 SWITCH +

Type Power CN9-2 CN9-3 SWITCH RX_GND State Function 9 to 15V DC when shorted These two pins must be shorted to enable scanner operation. They are connected to the external enable switch accessible from the pedestal outer. GND

Not connected 5 t r a P 2 r e t p a h C Service Motor Enable Override Jumper Ref. JP_1 JP-2 Signal Name M0V M_OFF Type Power Analogue input 0V State Function This jumper is normally open. However it may be shorted by service personnel to enable motor rotation regardless of normal software control. Thus with the jumper shorted the motor should run as long as power is applied and the scanner disable switch is in the enable position. WARNING: Ensure the antenna and gearbox are safe to rotate before making this short. If necessary remove the antenna 8 Service Manual 83147-2-Ch2 Chapter 2. Technical Description Internal Cooling Fan CN11-1 FAN +

CN11-2 FAN Type Power GND Ref. Signal Name State Function

+12V DC

+12VDC power to cooling fan GND Power return 2.3 Modulator / PSU Circuit Description Design Overview The Modulator / PSU PCB integrates the modulator, power supply and motor drive functions of the radar scanner assembly. The power supply section provides regulated power to all functions within the scanner unit, except the motor, which is driven directly off the input supply. The modulator drives the magnetron when enabled and triggered from a simple logic input with one of eight pre-set pulse widths selected by the IF receiver module. The Motor Controller drives the 3-phase DC brushless motor which rotates the antenna. The figure below shows an overall block diagram of the Mod/PSU PCB showing the principal circuit blocks :

DC-DC Receiver/Modulator PSU AUX+12V MOD+Heat MOD+HV IF+5V IF--5V IF+12V IF+26V 3-Phase Motor Drive 3-Phase Motor Modulator Magnetron MOTOR_EN_N STEP_IO PW_ADJUST PTX_ADJUST PRI_PLS PW0 PW1 RADAR_TX_EN MOD_ISENSE Control AUX+12V SHP_IN Startup / Shutdown Cct Ship's Heading Interface Supply Reversal Protection EMC Filter Ship's DC Supply IP_FET Over Voltage Protection AUX+12V is an internal 12V supply rail (primary side ref.) IP_FET is internal supply rail (ship's supply ref.) D4649-2 Figure 6. Modulator/PSU Overview IF Receiver Ships Heading Sensor

(Hall Effect) Scanner Disable Switch 5 t r a P 2 r e t p a h C Service Manual 83147-2-Ch2 9 Pathfinder Radar/Chartplotter Series Circuit Description EMC Filter The EMC filter section comprises of series ferrites, common mode inductor and associated filter capacitances to minimise EMC problems with other electronic equipment. Over Voltage Protection A varistor, VR1, protects the unit from over voltage surges. Supply Reversal Protection The scanner is protected from inadvertent reversal of the ships supply by FET, Q1. This FET will not connect the ships supply to the board as long as its polarity is reversed. When the ships supply is connected correctly the FET body diode will conduct and start the internal charge pump formed by D33, C146, etc. which will drive the IP_FET supply to approximately 12V greater than the ships supply voltage and turn ON the FET. DC-DC and Start / Shutdown Circuit WARNING: The Power Supply circuit contains very high voltages and energy levels, care should be exercised in all maintenance activities in this area. Only those items which appear on the Raytheon spares list may be replaced. This switch mode power supply unit derives the low voltage supplies for the receiver, modulator, magnetron and motor drive assemblies. It is configured as a flyback converter whereby the ships supply is switched at approximately 65kHz across the primary of transformer Tx1 by FET Q21. Pulse width modulation (PWM) control is by IC U8 which senses the voltage of an internal power rail, +5V5, and drives the FET to maintain voltage regulation. With the exception of the internal supply, AUX+12V, IP_FET, PWM+V, +HIGATE and +GATE, which have the ships supply as their ground reference, all other output voltage rails are isolated from the ships supply and therefore must be ground referenced to the secondary side when measured (note when fitted within the core assembly the secondary side ground reference is connected to the metal chassis). The high voltage supply, MOD+HV, is derived from a pair of series connectred secondary windings. The IF+26V supply is derived from a charge pump comprising D21, Q23, etc. 10kW only. The 10kW unit uses an additional series connected PSU circuit comprising of U10, TX2, etc. to generate the additional voltage required to drive the 10kW modulator. This supply operates only when the antenna motor is enabled. The +GATE supply is referenced to TX1 primary side, and is derived from the primary flyback voltage. This supply is referenced to the positive supply input rail such that it remains approximately 15V greater than the input supply. From this rail the IP_FET and +HIGATE supplies are derived to drive the input polarity protetection FET, Q1 and the 3-phase DC motor FETs Q5, Q9 and Q13 etc. The auxiliary +12V supply derives power to supply the PSU controller U8, and the motor drive controller U4 etc. This output is driven from a charge pump driven by the primary of TX1, formed by D61 - D65, etc. this supply is essential to the operation of the whole modulator/PSU assembly, since without it the operation of the main PSU and motor drive will fail at lower ship's supply voltages. From this supply PWM+V is derived which powers the switch mode controller, U8, via the external scanner disable switch. When the switch is opened power is removed from U8 which shutsdown and thus disables all supplies. This in turn disables the motor controller and thus the motor. 10 Service Manual 83147-2-Ch2 5 t r a P 2 r e t p a h C Chapter 2. Technical Description The scanner is protected from operation at inadequate ships supply voltages by the start/shutdown circuit comprising of Q27, etc. This circuit will shut the supply down if the ships supply falls below the minimum scanner operating voltage. This circuit also detects a fault condition if the secondary supplies are over voltage, via D39, OP3, etc. If this fault condition is detected the supply is shut down. In both shutdown cases described above after a brief interval the supply will attempt to restart. If the fault condition is still present then a further shutdown occurs. Thus the supply will cycle in this manner at low frequency until the fault is cleared. Scanner operating supply voltage range Parameter Units Conditions Operating Voltage Range 4kW - Measured at CN10 10kW - Measured at CN10 Minimum startup voltage Minimum voltage to start operating, measured at CN10 Reverse polarity leakage current

+/-100 DC Measured with 44.0V differential imposed between V-SHIP+ and isolated GND. Maximum Leakage current between isolated secondary GND and ship's supply Output Specification DC-DC1 Units Nom. Max. Conditions IF+12V output voltage 11.2 12.0 IF+26V output voltage 25.0 27.0 29.0 Load will be reduced to minimum during standby state of IF receiver. Load will be reduced to minimum during standby state of IF receiver. Load will be reduced to minimum during standby state of IF receiver.

-6.4 125 5.3 350 12.4 300 2 Parameter IF-5V output voltage IF-5V load IF+5V output voltage IF+-5V load IF+12V load IF+26V load Modulator Max. 44.0 44.0

+/-1

-6.0 5.0 Min. 7.5 15.0 10.0 0 0 Min.

-5.6 0 4.7 50 0 1 V V uA uA V mA V mA V mA V mA WARNING: The modulator circuit contains very high voltages and energy levels, care should be exercised in all maintenance activities in this area. Only those items which appear on the Raytheon spares list may be replaced. 5 t r a P 2 r e t p a h C The modulators function is to drive the magnetron in order to generate a transmit pulse at approximately 9.4GHz to the antenna. The modulator is required to generate eight different pulse widths as selected by external logic control lines, PW0, PW1 and analogue control, PW_Adjust. The PW0 and PW1 logic controls select one of four possible coarse pulse width selection ranges, whilst fine adjustement within each coarse range setting is provided by the analogue voltage setting of PW_Adjust. Each unit is calibrated for pulse width by automated production test equipment, and the calibration data is saved within the non-volatile memory within the IF controller. Modulator output power is trimmed by production test equipment by adjustment of the analogue voltage setting of PTX_ADJUST. Service Manual 83147-2-Ch2 11 Pathfinder Radar/Chartplotter Series The modulator is fired when triggered by the rising edge of the PRI_PLS logic level control signal from the micro controller. In addition a further control line RADAR_TX_EN is used to over-ride PRI_PLS and disable transmission when held low (the default state is transmit disabled in the event of the IF controller being disconnected). Output sense lines, HEATER_OK and MOD_ISENSE, indicate correct operation to the external micro controller. The modulator comprises a high voltage pulse transformer, Tx3 (4kW) or Tx4 (10kW) and a switching FET Q41 (4 and 10kW) and Q42 (10kW only) together with associated control and pulse shaping circuitry. In operation the control circuitry selects one of eight pulse widths which then drive the FET gate via IC U13. As the FET turns on it switches the high voltage supply, MOD+HV, across the very low impedance of the pulse transformer primary. The current rapidly rises in the FET(s) and their series source resistors until the FET(s) begin to pinch-off thus holding the current at a constant level. The resulting primary voltage pulse causes an associated secondary pulse stepped-up by the transformer turns ratio to several kV. When the secondary voltage reaches the magnetron switch-on threshold it will fire generating a burst of microwave power at several kW and at a frequency of approximately 9.4GHz. The voltage supply to U13, nominally at 18V, is controlled by PTX_ADJUST which allows the primary current to be trimmed and thus the magnetron current controlled. The FET(s) are protected from operation at excess temperature by a thermistor, RT1 attached to the FET heatsink. This functions so as to disable the modulator pulse generation circuitry, U11A, etc, in the event of excessive heatsink temperature (>100C). It is further protected from operation with low or unstable supply voltage by Q29, D26, Q40, etc. The control circuitry comprises a monostable U11A, whose pulse width is controlled by selection of one of four capacitor values under control of the logic level PW0, PW1 control lines. Fine adjustment of pulse width by variable analogue voltage control, PW_Adjust is achieved by varying the effective resistance of R262, R263. An additional monostable, U11B limits the maximum pulse repetition rate under fault conditions. Table 1: Range, Pulse Width and PRF Table (4kW/10kW) Range (nm) Nominal PW (ns) PRF (kHz) PW1 state PW0 state Normal Magnetron Current Reading Course Pulse Width

(X = Pulse Expand ON) 5 t r a P 2 r e t p a h C 1/8 1/8X 1/4 1/4X 1/2 1/2X 3/4 3/4X 1.5 1.5X 3.0 3.0X 65 90 65 90 90 150 150 250 350 450 450 600 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 2.0 1.6 1.6 1.2 0 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 0 0 1 1 0 0 0 0 1 1 17 - 40 30 - 60 17 - 40 30 - 60 30 - 60 58 - 94 58 - 94 84 - 130 85 - 145 85 - 145 85 - 145 85 - 145 80 - 135 SP range SP range SP range SP range SP range MP range MP range LP range LP range LP range LP range VLP range VLP range 6.0 or greater 1000 (4kW) 1200 (10kW) 0.74 12 Service Manual 83147-2-Ch2 Chapter 2. Technical Description Two circuit blocks monitor the performance of the modulator / magnetron to provide diagnostic information for service personnel which may be read in the diagnostics menu at the display unit. Comparitor U14D senses the correct flow of magnetron heater current and provides an output, HEATER_OK which is normally a logic high when the magnetron is connected and drawing at least the minimum specified current. Peak detector D60, etc detects the peak pulsed magnetron current flow and derives the signal MOD_ISENSE which gives an indication of the transmit power. This circuit is an improvement on that used on the D2 and D4 radome scanners and may be used with some confidence to diagnose correct modulator/magnetron operation. The reading may be found in the display diagnostics menu (seeSection 3.3). The value will change with selected range setting. See Section 3.6, Diagnostics Menu and Table 1 below, for details. Modulator Clock, PRI_PLS 10us _+ 0.5us PRI_PLS 1/PRF or PRI Figure 7. Modulator clock, PRI_PLS Ships Heading Sensor 3-5V 0-0.5V D4059-2 The ships heading sensor is used to indicate the antenna alignment. It provides one output pulse per antenna revolution. This information is utilised by the IF receiver to synchronise the radar output to the ships heading. A Hall effect transducer is triggered by a magnet on the principal gear of the antenna rotary joint assembly. This results in a negative going pulse at CN5-1. This pulse is conditioned by the interface formed by R124, C100 and reappears as SHP_IN at CN2-15 as a negative going pulse of approximately 5V amplitude. If the antenna is rotating normally this pulse will have a repetition rate of approximately 2.5 seconds. 3-Phase DC Brushless Motor Controller All open array radar systems use a 3-phase DC motor. The controller for this motor is based on an integrated controller IC, U4. This IC provides electronic commutation of each of the three motor phase windings. Three hall effect transducers embedded within the motor signal the position of the rotor. These signals RLG1, RLG2, RLG3 are then interupted by U4 to signal which motor phases are to be driven by the 3-phase bridge formed by Q5/Q14, Q9/Q15 and Q13/Q16. The motor Hall transducer signals are combined by U1, U2A to provide antenna positional feedback to the IF controller. When rotating normally at 24 rpm, the signal at TP34 and CN2-10 (STEP_IO) should be a logic level clock at approximately 590 Hz. In addition the hall transducer signals are used to derive rotational speed feedback via U1, U2A and U3C. The output of filter U3C is a DC voltage proportional to motor speed. The desired speed is set by potentiometer RV1 and is set to establish a motor speed of 2900 RPM. Motor over-speed is detected by U3D which enables motor braking to minimise overun speed in high wind conditions. Motor torque control is achieved by controlling the switching duty cycle of the 3-phase bridge, bottom FETs, Q14, Q15, Q16. This pulse width modulated control operates at approximately 25kHz. Each on cycle may also be terminated 5 t r a P 2 r e t p a h C Service Manual 83147-2-Ch2 13 Pathfinder Radar/Chartplotter Series prematurely by peak motor current detected by R102, if the peak winding current threshhold is exceeded (approximately 13 A). exceeded (approximately 13 A). Fault conditions such as incorrect hall transducer inputs or excessive motor current are detected by U4 and signalled at pin 14. This fault signal is conditioned and timed by monostable U2, U3B, etc. and in the event of a persistent fault of approximately 10 seconds duration the motor controller is disabled and latched off. Thus an obstructed antenna will cease to drive after this period. This condition will also be detected by the IF controller microprocessor and transmission will be disabled. Once latched OFF the motor circuit will remain off until either the radar power button is pressed to switch the mode back to 'transmit', or the power is cycled. Note: The motor controller circuit is referenced to ship's battery negative. 2.4 IF Receiver PCB Interface Description The Interfaces to the IF Receiver are shown in Figure 4. The individual signal functions are described below:-

Connectors Connector P1 P2 P4 Ref. P2-1 P2-2 Display Connector (P2) Function LNC connector Display connector for serial communications, video and synchronisation timing signals Type 20 way SAMTEC CLH-110-F-D-DV-P

(7 pins used only) 10 way Picoflex ribbon connector Mod-IF interconnect 18 way Picoflex ribbon connector Signal Name Type State Function AZ_SHP_OUTB AZ_SHP_OUT clock, differential pair output normally high, low going clock normally low, high going clock 0 - 5.0V A differential output pair providing azimuth pulses to synchronise antenna position with the display (10us duration at approximately 820 Hz). The SHP

(ships heading position) pulse is superimposed on the signal once per antenna revolution (30us pulse every 2.5 secs) An RS485 Bi-directional serial communications link operating at 19.2 kBaud. It provides control of the scanner operation and monitoring functions from the Radar display. A differential output pair providing PRI

(Pulse Repetition Interval) pulses to synchronise the firing of the transmitter with the display video. Rate is according to range setting. Not used P2-3 P2-4 SER_IOB SER_IO digital comms, differential pair bi-directional 2.2 V nom. DC bias 2.8 V nom. DC bias 5 t r a P 2 r e t p a h C P2-5 P2-6 PRI_OUTB PRI_OUT clock, differential pair output normally low, high going clock normally high, low going clock 0 - 5.0V VIDEO GND VIDEO Analogue Video output AC coupled 1.75V max peak signal into 75 ohms The raw Radar video signal from the scanner. Spare P2-7 P2-8 P2-9 P2-10 GND 14 Service Manual 83147-2-Ch2 Chapter 2. Technical Description Figure 8. AZ_SHP_OUTB / AZIM_DNEG Figure 9. AZ_SHP_OUT / AZIM_DPOS Figure 10. PRI_OUT / PRI_DPOS 10us _+ 0.5us AZ_SHP_OUTB 10us _+ 0.5us AZ_SHP_OUT 10us _+ 0.5us PRI_OUT 10us _+ 0.5us PRI_OUTB approximately 1.2ms approximately 1.2ms 1/PRF or PRI 1/PRF or PRI Figure 11. PRI_OUTB / PRI_DNEG LNC Connector (P1) Ref. P1-1 P1-2 P1-3 P1-4 GND 60MHz IF Not Connected N/A RF_ATTENV 60MHz Intermediate Frequency (IF) Radar received signal input Analogue control voltage output Analogue control voltage output State N/A N/A 0 - 10V 4 - 24 V P1-5 TUNE_V P1-6 GND Analogue output 0V Signal Name Type Function 3-5V 0-0.5V 3-5V 0-0.5V 3-5V 0-0.5V 3-5V 0-0.5V D4061-1 D4062-1 D4063-2 D4064-2 The down-converted received radar signal from the LNC at 60MHz carrier frequency. N/A N/A A control voltage that is applied to the LNC VCO (Voltage Controlled Oscillator) to maintain the tuning of the LNC output to 60MHz. Analogue ground reference for the LNC supplies. 5 t r a P 2 r e t p a h C Service Manual 83147-2-Ch2 15 P1-7

+5V Analogue Output

(switchable) 0V in standby mode

+5V in transmit mode The 5v supply for the LNC. It is switched off in standby mode to save power. P1-8

-5V Analogue Output

-5.9V nom. The -5.9V supply for the LNC Pathfinder Radar/Chartplotter Series

-5V GND RF_ATTENV GND Figure 12. LNC Connector P1 connections as viewed from component side of board

+5V TUNE_V N/C 60MHzIF D4065-1 Mod / IF Interconnect (P4) This connector P4 is pin to pin identical to CN2 connector on the MOD / PSU PCB. See MOD / PSU interface section for details. 2.5 IF Receiver Circuit Description Main Receiver The prime function of the IF receiver is to provide low noise amplification and logarithmic detection of the 60MHz IF (Intermediate Frequency) Radar received signal, to give a video signal output suitable for displaying on the Radar screen (after digital processing at the display). The receiver provides low noise amplification, dynamic IF gain control (STC) and selectable IF bandwidths to optimise target detection for all ranges and for various sea and weather conditions. The following summarises the functions of the circuitry. A low noise amplifier (AR1), is situated prior to an adjustable gain monolithic microwave integrated circuit (MMIC) amplifier stage (U9 and U10) in order to define the noise figure of the system. This incorporates the relevant circuitry to provide fast gain control via the STC generator. General amplification and attenuation control is also provided by the cascaded MMIC amplifiers U9 and U10 in conjunction with factory-tuned inductors (L4, L10 and L11) and capacitors to tailor the bandwidth characteristics of the circuit. IF Bandwidth switching between 12MHz and 3MHz is configured to provide matched filtering for the shorter transmit pulses which are automatically set when the Radar range is adjusted. Gain is increased accordingly to maintain a relatively constant noise power at the receiver output. 5 t r a P 2 r e t p a h C Switched video filters are used in conjunction with the 3MHz IF filter to provide matched filtering for the 600ns and 1us/1.2us pulses. These are 0.7 MHz and 0.5MHz respectively. Remaining variations in noise power as a consequence of the different signal bandwidths (i.e. noise power is directly proportional to bandwidth) are adjusted in the display. A fast time constant circuit is used to provide a continuously variable high pass filter to provide some immunity against the bulk effects of rain. N.B. The variable inductor coils L4, L10 and L11 are preset at the factory. They require specialist equipment for tuning and must not be adjusted by the service engineer. The PRI rates and video noise can be observed at the appropriate connectors (see interface section) for the different range settings as follows:

16 Service Manual 83147-2-Ch2 Chapter 2. Technical Description 0.125 to 0.75 nm 1.5 and 3nm 3nm (target expand) 6nm to max range IF BW 12MHz 3MHz 3MHz 3MHz Autotune Receiver Summary of bandwidths, pulse widths and PRI rates Radar Range Setting Video BW Pulse width used Video Noise level 15MHz 15MHz 0.7MHz 0.5MHz 65 to 250ns

>500mV pk-pk 350 and 450ns

>500mV pk-pk 600ns 1us/1.2us

>250mV pk-pk

>200mV pk-pk The autotune receiver provides frequency selective peak detection of high level main-bang transmitter pulses. This is achieved using a high impedance branch from the main receiver input with a transistor/diode based amplifier/detector circuit (Q31, Q32, D16, Q33, Q37). The detection bandwidth of the autotune receiver is set at the factory using variable inductors L7, L8 and L9. The output of the receiver is buffered (U6A) and passed to the scanner microprocessor. A tuning algorithm is then performed at the display to set the difference frequency between the magnetron and VCO (Voltage Controlled Oscillator) to a fixed IF frequency of 60MHz using the TUNE_V control line P1 pin5. Both coarse and fine adjustment are provided by the microprocessor to allow for initial setting and subsequent fine tuning. N.B. The variable inductor coils L7, L8 and L9 are preset at the factory. They require specialist equipment for tuning and must not be adjusted by the service engineer. STC/Main Bang Suppression (MBS) The STC circuitry consists of a logarithmic function generator split into four outputs and multiplied by 4, 5.5 and 2 to generate the respective R4, sea clutter and rain curves respectively. These curves are offset as requested via processor/operator demands and then combined to provide an output equal to the greatest of the inputs. A curve splitter and linearisation circuits are used to match the output control levels to the characteristics of each attenuator. General STC Characteristics MBS Curve amplitude variations Decreasing Attenuation Sea clutter - R5.5 decay STC - R4 decay Rain clutter - R2 decay Fixed gain 5 t r a P 2 r e t p a h C Combined curve generated as an output equal to the greatest of the inputs Time D4650-1 Figure 13. General STC Characteristics Main bang suppression (MBS) amplitude and duration controls are configured so as to override these STC controls. For low values of attenuation the attenuation is applied to the Monolithic amplifiers in order to preserve system noise figure. At higher values of attenuation the attenuation is divided between the IF pin attenuator (D17) used to control the first IF amplifier stage, and the Monolithic amplifiers. Service Manual 83147-2-Ch2 17 Pathfinder Radar/Chartplotter Series Microcontroller The microcontroller subsystem, using an NEC 78054 device, is integrated onto the IF receiver board and provides the following functions :-

Generates analogue control voltages via a multi channel Digital to Analogue Connector (DAC) for all user and automated scanner adjustments Reads the tune indicator input and adjusts tune control voltage as necessary. Controls modulator pulse width selection. Generates Azimuth pulses synchronised to the 3-phase motor for display synchronisation. Generates the PRI (Pulse Repetition Interval) pulses to fire the magnetron, start the STC cycle and synchronise the display. Buffers the Ships Heading Pulse from the MOD/PSU PCB for synchronising the display. Communicates with the display via a serial interface. Initial Scanner set up (EEprom stored values) The scanner has non volatile storage (EEprom U18) for the following items:-

Optimum VCO coarse and fine tune settings. Calibrated values for setting each of the 8 transmit pulse widths. Default values for the Auto Gain function for each pulse width (used when GST is selected for MBS Duration and Amplitude for each pulse length. Range Zero Offset (adjusted by Display Timing function in Advanced settings Menu) for each Azimuth zero offset (adjusted by Bearing Alignment function in Radar Set Up Menu) STC Preset Max - a preset level of R4 clutter curve is set to equalise close target returns Scanner Size - storage of the antenna size fitted to the Scanner - used to set Max Range for the display). filter setting Display Modulator Power - The power of the modulator in kW - also used to set Max range for Display 5 t r a P 2 r e t p a h C The above stored parameters each have a factory set and used working location. These values are set at the factory and are optimised for each individual scanner unit to provide optimum performance and a good starting value when the Radar system is first operated. However, the VCO tuning, range zero offset and Azimuth zero offset used working values are adjustable from the display during Radar operation. Due to temperature variations affecting the LNC, the VCO tuning values are adjusted by the display when Auto mode is selected to give optimum tuning. The present optimum value is stored when a range change (i.e. transmit pulse length change) is made, so that when the range is selected again, the auto-tune function is at a better starting point. Normally this adjustment is made just to the fine tune value for each pulse length. Occasionally, a change in coarse tune may be necessary. If tuning problems occur, the Tune Preset function in the Advanced Settings Menu provides a manual way of adjusting the coarse tune used working value. The Range Zero Offset is adjusted manually from the display Advanced Settings Menu (Display 18 Service Manual 83147-2-Ch2 Chapter 2. Technical Description Timing) as part of the normal Radar installation procedure. If the inter unit cable is kept to the supplied length the Display Timing should not normally need adjusting. STC preset maximum is set at the factory, however the STC preset value can also be changed via the Advanced Settings Menu. When a Factory Reset is performed (press MENU, select SYSTEM SET UP, the press and hold MENU for 5 second countdown) the scanner copies the Factory set values back into the used working locations of the EEprom so the scanner and display are as they were set up when they left the factory. The EEprom also stores the scanner Build Standard information that is accessible through the Diagnostics Menu - see chapter 4 - fault finding. 2.6 Antenna / Rotary Joint Assembly The primary specifications for the antenna / rotary joint assembly are as follows :-

Parameter Operating frequency Azimuth beam angle Elevation beam angle Return loss Sidelobe levels Antennae gain across bandwidth 48" Open Array 9.410GHz 63MHz *

1.85 nominal 25 nominal 28.0dB nom

>15.0dB

>22.0dBc

* Bandwidth requirements are defined by the magnetron uncertainty 2.7 Scanner Display Connection The scanner / display interface is a universal link between any display and any scanner. It consists of a single, multi-core cable with a single moulded plug at the display and multiple sprung loaded connections at the scanner:

Video, Serial bus, PRI, Azimuth/Ships heading pulse (connected at CN8). Power (connected at CN10). A moulded plug at the display provides the necessary sealing against the environment, whereas at the scanner this is provided with a compression cable gland. The cable consists of the following cores :

1. 75 ohm coaxial cable carrying the 1.75V peak to peak video signal from the scanner 5 t r a P 2 r e t p a h C 2. Twisted pair cable carrying the 5V differential azimuth and ships heading reset synchronising signal from the scanner (pins 1and2). 3. Twisted pair cable carrying 5V differential PRI pulse synchronising signal from the scanner (pins

(pins 7and 8). 5and6). 4. Twisted pair cable carrying 5V differential, bi-directional serial communications signal (RS485) between scanner and display (pins 3and4). 5. DC ships power to scanner(4 cores) Service Manual 83147-2-Ch2 19 Pathfinder Radar/Chartplotter Series 5 t r a P 2 r e t p a h C 20 Service Manual 83147-2-Ch2