Download RADAR BY HUGH LUPO

RADAR
BY
HUGH LUPO
MARITIME ELECTRONIC TECH TRAINING
WHAT IS RADAR
•HOW DOES IT WORK
• TRANSMITTER
• TRIGGER PULSE
• MIC (microwave IC)
• IF AMP/ VIDEO
• DISPLAY
• DIGITAL
• FMCW
WHAT DOES RADAR STAND FOR ?
Radio Detecting and Ranging
The radar transmits a signal then receives For a
fixed period of time.
The echo reflected off a target.
The time laps and direction of the return
target is then recorded on a screen.
The mark on the screen is known as a pip
BLOCK DIAGRAM PUSE RADAR
SCANNER
DISPLAY
ANTENNA
CIRCULTATOR
MAG
C
MOD
C0NTROL PANEL
MIC /
LNA
IF
AMP
HD, BP
PROCESSOR
video
trigger
NAV IN
0183
SHIPS
MAINS
GYRO
OR
HDT
TRANSMITT
•The processor generates a pulse. ( The pulse width is controlled by the range selection)
•The pulse is amplified on the modulator board and feed into the pulse transformer
•The pulse now is around 4kv and feed to the Magnetron
•This oscillates the Magnetron and the 9.4 GHz wave is radiated from the array.
4KV P-P
400 V P-P
12V P-P
pulse width
10-20 us
12 VP-P
ARRAY
TX
RX
LIMITER BLOCKS INCOMMING RF
From the transmitter and other
Radars in close proximity
RECEIVER
•The circulator passes the transmitter signal to the antenna and the receiver signal
•From the antenna to the limiter in the MIC
•The MIC converts the 9.4 GHz signal down to 60 or 30 MHz depending on the system
design.
•Rf amp, increases the low level signal
•Double balanced mixer, mixes the 9.4 GHz signal with the local oscillator frequency
and produces the IF (intermediate Frequency) of 60 or 30 MHz
• IF amp increases the IF freq and outputs the video to the display
AFTER THE IF AMP BOARD
IF AMP BOARD
M
I
C
TURNING GEAR
The turning gear is made up of the Motor, Ships heading marker switch (flasher) and
The Bearing Pulse Generator.
•The motor drives the array in a 360 deg continues circle at 24 or 48 rpm
•The ships heading marker (flasher) resets the count at 0 deg every revolution to bow
reference.
•The bearing signal generator outputs a count from the timing disc. This disc has 60
Slots cut in it and uses a photo transceiver to produce a count of 144 rpm as it turns.
• This is then converted to a count of 4096 pulses that represents 360 deg on the
Screen in the display. One resolution
•These signals are all feed into the processor and this gives us the position of the
target in reference to the bow of the vessel
PROCESSOR
EAV ECHO AVERAGING
GDC GRAPHIC DISPLAY CONTOLLER
RADAR DEFLECTON BOARD
CONTRAST
AMP
PLATE CONTROL
DIGITAL RADAR
What is the difference ?
All signal conversion from analog to digital
Is processed in the scanner.
The transmitter functions are processed
In the scanner.
All the information from the scanner is
Transported by ether net.
The scanner has its own power supply.
The scanner now is called a sensor.
DIGITAL
RADARHall effect position sensor
shm
MTR
RX MOD
SPU
MD
The trigger pulse generated in the Field Programmable Gate Array (FPGA) on
the SPU (SIGNAL PROCESSOR UNIT) board is delivered to the modulator (MD) board and used
to trigger the magnetron.
The Pulse Repetition Frequency (PRF) and pulsewidth of the TX trigger pulse
varies according to the range in use.
The 60 MHz IF and video signal from the RX module is input to the
SPU board and processed by the FPGA.
Unlike the radar scanner unit, the DRS sends the video signal to the display unit
(MFD) via Ethernet, instead of through coaxial cable. Thus, no video timing adjustment is
required
1) SPU board
2) MD (Modulator) board
3) PWR (Power supply) board
4) MTR (Motor control) board for open antenna
5) DRS (Digital Radar Sensor)
The control signals including Radar ON/OFF signal are generated in the MFD
and sent to the DRS via Ethernet
RX module (RXM)
The Receiver Module, RXM consists of Microwave Integrated Circuit
(MIC) and a semi-logarithmic IF amplifier. The MIC down-converts the RF
signal to the 60 MHz IF signal.
The V_TUNE signal controls the VCO in the MIC to tune the MIC with the receiving
RF signal.
The LNA and VGA CONTROL signals control the gain of LNA (Low
Noise Amplifier) in the MIC and the VGA (Variable Gain Amplifier) in the IF amplifier.
Other signals from the SPU board to the RF module are;
(a) VOLTAGE_COMMON
The reference voltage output from the ADC is applied to V_COM terminal of the
differential amplifier in the IF amplifier circuit.
(b) CARRIER_GATE
This signal selects the output signal from the IF amplifier to either video signal for
normal operation or IF carrier signal for automatic tuning.
(c) BAND_WIDTH
This signal selects the bandpass filter in the IF amplifier; 1.7 MHz or 20 MHz.
(d) MBS_CONT
This signal turns on the Main bang attenuator in the IF amplifier.
This image cannot currently be displayed.
FET DRIVER ON OPEN ARRAY ONLY
MTR BOARD
The antenna motor used in the DRS is a three phase brushless DC motor
with the Hall effect position sensors.
The outputs from a set of hall sensors inside the motor are supplied to the SPU board
through the MTR board in the antenna.
The motor drive circuit consists of the high-side and the low-side drivers. Each side
is driven separately by the motor control signals, M HD A/B/C for the high-side and
M LD A/B/C for the low-side respectively.
The over current and overload detectors output 5 V (“H” signal) in normal condition,
and 0 V (“L” signal) in an over current and an overload conditions.
***
***THE 4 & 6 KW OPEN ARRAY HAS A STORAGE CAPACITOR IN THE TXHV LINE
MD BOARD
The MD board for 2 kW and 4 Kw transmitters in the radome type antenna.
The board mainly consists of an FET driver, a switching FET, a pulse transformer,
a Rate of Rise of Voltage pulse circuit (RRV), magnetron current detector, and a
voltage divider.
The open 4 and 6 kw open array has a storage capacitor added in the HV circuit
Other than that the circuit is the same.
NAVICO BROADBAND RADAR. FMCW
Frequency Modulated Continuous Wave
This system transmits a MODULATED FREQUENCY for 1 ms. Long increasing in frequency.
For example it will start its transmitted signal at 9.400 GHz and stop at 9.410 GHz.
The receiver is sweeping the same frequencies and listening for return signal in the
Selected band. The receiver is a wide band receiver
Both the transmitter and receiver are in continues mode, Not Pulsing. This gives a big
advantage with targets, and enhances close in targets
The targets are compared to the tx frequency when received and the difference between
The Tx and Rx echo frequency to measure the distance.
The rest of the system works the same as pulse radar.
The use of a magnetron is not Needed for this system, they use semiconductor finals
with low power output.
Pulse vs. FMCW
FMCW Radar
Pulse Radar
•
•
Pulsed Transmissions
Magnetron
–
•
Used for both transmitting and
receiving
•
–
•
Pulse length depends on range
•
Frequency Modulated Continuous Wave
Dual Antennas
–
–
High Power Pulse
–
Continuous Transmissions
One continually transmitting
One continually receiving
Low Power
9.410 GHz
Target echo retains the same freq when
It was transmitted.
Tx Freq 9.405
At any instant in time, Tx Freq is higher
Than Rx Freq
Rx Freq 9.403
9.400 GHz
1 ms tx time
FMCW = Frequency Modulated Continuous Wave
The scanner transmits a ‘rising tone’ (Tx wave) with linearly increasing frequency. The wave
propagates out from the transmitter retaining the frequency it had when it was transmitted. If it
reflects off an object, it will return to the receiver, still at the frequency it had when originally
transmitted.
Meanwhile, the transmitter continues to output an increasing frequency.
The difference between both the currently transmitted and received frequencies, coupled with
the known rate of frequency increase, allows a time of flight to be calculated, from which
distance is calculated.
BP
Conventional X-Band Magnetrons
Solid State, small X-Band Transmitters are in all
Navico Broadband Radars
MARTIME ELECTRONIC TECH TRAINING
METT
[email protected]
203-205-0266
I offer training seminars in marine electronics on theory of many
Different subjects. Some include
VHF RADIO
SSB RADIO
ANTENNA THEORY
RADAR
SAT SYSTEMS
BASIC ELECTRONIC
CMET
Most of this material came from
FURUNO OR SIMRAD
Service manuals.
I thank NAVICO for the support
They provided me on the new
FMCW system.