센서 > "Mobile Amateur (Doppler) Rain Radar" Project

TODAY773 TOTAL2,229,331
사이트 이용안내
Login▼/회원가입
최신글보기 질문게시판 기술자료 동영상강좌

아두이노 센서 ATMEGA128 PWM LED 초음파 AVR 블루투스 LCD UART 모터 적외선


BASIC4MCU | 센서 | RADAR | "Mobile Amateur (Doppler) Rain Radar" Project

페이지 정보

작성자 키트 작성일2017-08-30 16:24 조회2,144회 댓글0건

본문

"Mobile Amateur (Doppler) Rain Radar" Project

Is it possible to make your own Doppler rain radar? Yes, I think so but nobody did it until yet. It is my target to build a mobile amateur rain radar for 10.4 GHz under 2000 Euro. 3 cm rain scatter is very similar and OE5VRL (Rudi) gave me some ideas with his rain scatter detector http://www.dl6nci.de/oe5vrl.htm

The Doppler effect, named after Austrian physicist Christian Andreas Doppler who proposed it in 1842, is the change in frequency of a wave for an observer moving relative to the source of the wave.
Christian Doppler was born in my city Salzburg.

                

1. Time schedule & status

- March 2010 : Start of  project
- June 2010 : Made my radio license
                            * finished with my call OE2IGL
- Summer 2010 : Finishing system concept and calculations
                            * finished (see system overview)
- Summer 2010 : Finishing prototype computer and μ-controller software
                            * first tests with PIC32 and C-compiler finished
                            * computer software "dBZ calculation" with USB (via RS232) connection finished
                            * computer software "Radar visualisation" finished
- Spring 2011 : Finishing prototype feed/dish/RSSI & software
                            * homemade 10.4 GHz feed finished
                            * prime focus dish mounting on tripod finished
                            * μ-controller software with high speed ADC (0.5 MSps), USB connection, LCD display finished
                            * RSSI circuit, impedance converter finished
- Summer 2011 : Finishing of conical feed/dish/receiver without azimuth rotor
                            * μ-controller software with 12 bit HH-12 encoder, call sign generator
                            * modified SAT LNB downconverter
                            * mounting head and rotor concept finished in more detail
- Summer 2012 : Module tests of Rain Radar system with azimuth rotor
                           * azimuth rotor with worm gear, H-bridge and HH-12 encoder and μ-controller finished and tested
                           * power supply (12V accu) finished and tested
                           * Kuhne beacon transmitter modified (10.402 GHz and pulsed) and tested
                           * Receiver, RSSI and μ-controller tested
                           * Dish/conical feed/LNB at 10.402 GHz tested
- Autumn 2013: 
                           * Test with ready finished downconverter instead of modified LNB
- Spring 2014: 
                           * Optimized feed for offset dish
                           * Test phase of system (dish-feed-circulator-transmitter-down converter-receiver-RSSI-μcontroller-computer software)
- Autumn 2014: 
                           * System analysis/measurements/improvements
                           * Upgrade from 220mW to 4W transmitter power

- Planned summer 2015 : Start operation of my Rain Radar with "radar vis" software and azimuth rotor


2. System overview

2093095301_03zlU9Pi_radarconcept.jpg


3. Technical details

Frequency                        :    10.402 GHz, vertical polarisation
Dish diameter                   :        0.82 m
Dish gain                          :        37.0 dBi
Dish beam width              :          2.5 °
Dish rotation                    :             2 per minute
Azimuth resolution           :          0.9 °
Time per azimuth step      :          140 msec
Echo time                        :             2 msec
Pulse                               :          9.0 μsec
Effective radiated power  :           40 dBi
Sensitivity                        :          0.5 mm/h at 100 km



4. Details of modules

10.2 - 10.8 GHz circulator

- Isolation: 30 dB
- VSWR: 1.12
- Insertion loss: 0.35 dB

2093095301_2oxpZFez_circulator.jpg




 Homemade 10.4 GHz conical feed (wave guide)

- Copper tube with inner diameter D: 20.1 mm
- VSWR adjustment by moveable back wall
- Wave guide formula:

        1 / Lamda0= 1 / Lamdac2 + 1 / Lamdag2
        
        Lamdac = 1.706 x D = 34.3 mm
        Lamda0 = 28.82 mm (10.402 GHz)
        
        -> Lamdag = 53.2 mm

- Wave guide drawing:

2093095301_yckjF5az_waveguide.jpg

I use this feed to transmit and receive signals in combination with a circulator. Therefore return loss must be as low as possible (< -30dB). After first measurements of return loss and adjusting back wall with the screw I got around -20dB. Then I adjusted the length from the open end to the pin to 54mm (1x Lamdag). Now the return loss is better than -40dB.

Return loss of 45 dB (lower curve) @ 10.42 GHz, >42 dB @ 10.402 GHz

2093095301_YKJpTF9D_feed-RL.jpg


- For prime focus dish with f / D = 0.36

Closed end has a moveable back wall to adjust return loss. 

2093095301_mB954gTM_feed5.jpg

2093095301_4JwCA3cW_feed3.jpg    


- Corrugated horn feed (part of a standard sat tv LNB) for standard offset dish with f / D = 0.67

Closed end has also a moveable back wall and a moveable tube between probe and horn to adjust return loss. Return loss more than 50 dB.

 


- Dual mode horn feed for standard offset dish with f / D = 0.67

This type gives the best dish matching. 




- Optimized dual mode horn feed for standard offset dish with f / D = 0.67

Now this dual mode horn is my standard feed. Johannes Falk DC5GY has simulated this feed with CST microwave for best performance and measurements confirm his simulations.
It is robust, easy to adjust for best matching (with M2 screw), fits into standard LNB holder and is optimized for offset dish.

2093095301_wQ6guv21_opti-dualmodefeed.jpg

2093095301_aUytweXd_opti-dualmodefeed-RL.jpg

2093095301_wqkNXgxB_opti-dualmodefeed-sim.jpg




Microwave transmitter 10.402 GHz

This is the original Kuhne 10.368 GHz beacon transmitter with approx. 220mW.

2093095301_fA5haziJ_bake1.jpg

2093095301_3xLPYthd_bake2.jpg 

As this transmitter has only F1 (frequency) modulation I looked for simple A1 (amplitude) solution to switch on/off my pulse radar. To my surprise I found a p-MOSFET transistor (4 pin IC on the left above the output stage) doing this on the board. After little changes (see red marked area) and an additional n-MOSFET transistor it is possible to use F1 input as A1 input.

2093095301_cWJudRpy_bakeA1.jpg

2093095301_8jzC5iFD_bakemodified.jpg


In addition last transistor multiplier stage (before power amplifier stage) also has such a n-channel/p-channel combination to switch transistor power. Otherwise you will see a small signal from oscillator stage during pulse off periode at the 10.4Ghz output. Don't switch off/on oscillator stage! 

2093095301_l1Em7H4p_pulsed-multiplier.jpg


Here is a Multisim simulation and the real oscilloscope image. Yellow line = μcontroller pulse, blue line = TX pulse (power supply of amplifier).
Switch off edge of p-MOSFET is delayed and not sharp-edged. This could be adjusted with R3.

2093095301_XzlsH1yL_BSP171MOSFET-TastungTransmitter2.jpg

2093095301_MpaGtOlu_tastungTX.jpg
 

Improved version: better pulse shaping of output pulse (blue signal), rounded rise and fall edges.

2093095301_4IkqD0dp_BSP171MOSFET-TastungTransmitter3.jpg


Instead of the original 108.009 MHz quartz crystal I use a 108.354 MHz quartz crystal by Krystaly in Czech (thanks to OE5VRL for organizing). I only had to adjust the oscillator and then the output shows 10.402 GHz with 250 mW. Behind the quartz you can see the little quartz heater board.

2093095301_M8I5JjE2_bake10402.jpg        2093095301_RWcPtT3f_quartz.jpg



Downconverter 10.402 GHz -> 652 MHz

Some microwavers made good experiences with standard satellite LNB's. They have low noise figure, high gain and are very cheap. My first tests were done with such a modified LNB.

  

At first I removed the horn and then I made a hole into the waveguide opposite the probe. A short semirigid coax cable was soldered to the probe and ground.

  

The spectrum analyzer shows 10.7 MHz I.F. output of the AR8600 receiver.  The peak in the middle is my 10.402 GHz signal running through the modified LNB. 



 

 In March 2013 I found first LNB with a PLL instead of a resonator pill. Stability of frequency should be much better with a PLL.

2093095301_k052OIfQ_LNB-PLL.jpg

The internal 27 MHz quartz is multiplied by 361.111 inside the RD3560M chip to get L.O. of 9750 MHz.

2093095301_GMXL8svf_LNB-PLL-big.jpg



Big disadvantage of all modified LNBs is a poor noise figure at 10.4 GHz. Bigger than 2.8 dB against 0.55 dB at 11.5 GHz, measured with cold sky - hot sun method.
See more about modified LNBs here
Now this is my standard downconverter and a noise figure of 1.2 dB is doable. Roberto Zech DG0VE has good converters, e.g. the KON-DWN 97107.

As I will not switch off the downconverter/receiver stage during Tx pulse the downconverter detects the reflected Tx pulse of the feed horn.
3 amplifiers in front of the mixer are good for my weak echo signal but gain is too high for my strong dircet Tx pulse signal. Therefore I removed the 3rd amplifier (red one) to reduce overload of mixer.
green = sub-harmonic diode mixer
red = amplifier
blue = low noise amplifier

2093095301_cVvYd4bF_Converter97107.jpg


Received pulse spectrum after down converter with 18μsec Tx pulses. 

 2093095301_73PFUWVZ_pulse-spectrum.jpg

Echo signal against cold sky (no cloud, no rain, no hindrance). Peak is reflected Tx pulse from horn feed (first 20μsec) and after 20μsec there is only noise.
vertical -> signal strength of echo
horizontal -> time/distance

2093095301_fqRLJMas_20pulse.jpg  



FINAL COMBINATION (without Tx amplifier): conical dual mode horn - circulator - Rx down converter - Tx transmitter




To get more Tx power I use a 10.4 GHz PA with 4 W output made by Dirk Fischer DK2FD. That gives additional 13 dB.
PA is switched on/off with same n-channel/p-channel combination as used in beacon transmitter (switching drain power of amplifier). 

2093095301_LacVGios_radar-PA.jpg

2093095301_Dq7IY9JA_radar-PA-mod.jpg


Feed arm with beacon transmitter, power amplifier and downconverter.

2093095301_E0knPVZ7_Feedarm.jpg





AR8600 scanner with 10.7 MHz I.F. output and external RSSI (logarithmic received signal strength indicator) 

A RSSI can be built with e.g. SA627 and buffer amplifier to drive A/D of μ-controller. SA627 has a fast rise and fall time of 1-2μsec and a RSSI range of 90dB.

2093095301_oew0ckTb_RSSIfinished.jpg

2093095301_cgJM7Ti2_RSSItest.jpg

RSSI (mV) of SA627 chip versus RF input (dBmW): 

2093095301_yJCV0ghN_RSSI-SA627.jpg

2093095301_qTgUrYpQ_radar-calc.jpg




PIC32 μController

PIC32 ethernet or USB starter kit could be used. This controller has a speed of 72 MHz.    

2093095301_rn4Dk5HF_PIC32.jpg


USB starter kit with I/O expansion board and LCD/4x4 keypad

2093095301_gq1ANkJm_pic32IO.jpg



Sampling pulses every 2.22μsec and echo time up to 2ms

2093095301_AmBnysOI_samplingpulse.jpg    2093095301_NR1yuLqg_echo.jpg

μ-controller, RSSI meter, LCD, push buttons, motor driver in one box.
Pulses every 2ms in Tx mode.

2093095301_SHhMJpj0_radarpuls.jpg
 

2093095301_jhZJXwQB_radarelektronik2.jpg 








Mounting head for azimuth and elevation 

First tests with a small dish and motor controller.






Finished azimuth rotor with elevation sensor (small black box), azimuth encoder and tripod.

   

I use this tripod also for noise measurements (hot sun - cold sky method). This tripod can be extended to a top height of almost 3m without azimuth rotor system, 3.5m with it.
The adjustable cross-ties give better stability.


This was my first test of the pulse radar equipment in June 2014. First test was made without azimuth rotor. 20μsec pulsed transmitter, receiver and software are working but the system needs some improvements for best performance.

2093095301_HdvwhI7g_tripod2.jpg


My second outdoor test in October 2014 showed much better results (with reduced down converter gain and additional power switching of last transmitter multiplier stage).
Now I use a 9μsec transmitter pulse and 60 times averaging of weak reflected signal (230mW beacon transmitter power without PA).
First large peak is Tx pulse coming back to receiver and the next peak comes from mountain echos (distance around 20km).
vertical -> signal strength of echo
horizontal -> time/distance

2093095301_9ViQYdqm_radartest2.jpg 






Third outdoor test with 9μsec pulses, 60 times averaging and only 230 mW transmitter in October 2014. This time I removed a 20dB external attenuator in front of the RX because I don't need it. This enhanced signal-to-noise value.
Echos obtained from mountains, 0.5° to 2° degrees above horizon. Now system performance is very good (also without Tx PA) and next tests with rain clouds are planned.

In this case hindrance distance is 2.7 km and minimum distance is limited to 1.5 km  because of TX pulse width (10μsec * 3E8 m/s / 2 = 1500 m).
Distance range is from 0 to 100km (left to right).

2093095301_atLsMZuV_radartest3.jpg

Hindrance at 58.0 km with 3dB (S+N)/N.

2093095301_gCMFaszV_radartest4.jpg

Strong multiple echos between 10 and 20 km with up to 23dB (S+N)/N.

2093095301_VqxwglTr_radartest5.jpg

Why 60x signal averaging? -> to improve S/N by factor 10*log10(number of samples)0.5 
S increases by factor #samples. N = increases by factor (#samples)0.5 because s² (= variance) is additive.
s of noise is (4.3 / #samples0.5) dB. To detect  a signal S it should be 4 times greater than 1 s of noise.

Only 1x sampling for comparison. Noise fluctuation is much higher than above and it is not possible to detect a very small signal.

2093095301_jBP5QaF4_1xsampling.jpg




DC motor with encoder for azimuth (0 to 360° degrees)

12V worm gear motor with additional worm gear to get only 2 rpm.
Torque is approx. 100 Nm.
HH-12 Encoder has a resolution of 12 bit and an accuracy of approx. 0.2°.

2093095301_cGx1BMp3_getriebemotor.jpg   2093095301_eYTJAaIZ_hh12encoder.jpg


DC linear motor for elevation (0 to 90° degrees)

Not yet installed but I use the inclinometer sensor SCA61T .

2093095301_kxGZNB5d_linearantrieb.jpg    2093095301_y0RdbFgP_SCA61T.jpg




5. Computer software

"dBZcalc" is a VB.net software running under Windows. It is connected to the μ-controller via USB cable (virtual COM port, RS232) and transfers echo data from the RSSI analog-to-digital 10bit converter to the computer. These data are buffered in a file and the second VB.net software called "MobileRadar" reads this file. "MobileRadar" also converts echo data into dBZ values representing rain rate [mm/h] and makes a rain rate overlay.

dBZcalc with some test data coming from AR8600 receiver, RSSI and μ-controller

2093095301_i6uCHXls_dBZcalc2.jpg    

2093095301_FJLlARgn_dBZcalc1.jpg

Screenshot of MobileRadar coming soon




6. Place of test/operation

The red area shows the free sight of the rain radar from "Haunsberg" (730m), 47.936N, 13.014E

2093095301_KYqD2pZf_radarplace1.jpg

Red point shows the location of the station and the red circle shows the range of 100 km (up to Linz and Munich).

2093095301_gU9RfCo7_radar1.jpg

2093095301_i4vCIKbs_radarplace2.jpg

ⓒ Panorama http://www.udeuschle.de



HOME

 



 

댓글 0

조회수 2,144

등록된 댓글이 없습니다.

센서HOME > 센서 > 전체 목록

게시물 검색

2022년 1월 2월 3월 4월 5월 6월 7월 8월 9월 10월 11월 12월
2021년 1월 2월 3월 4월 5월 6월 7월 8월 9월 10월 11월 12월
2020년 1월 2월 3월 4월 5월 6월 7월 8월 9월 10월 11월 12월
2019년 1월 2월 3월 4월 5월 6월 7월 8월 9월 10월 11월 12월
2018년 1월 2월 3월 4월 5월 6월 7월 8월 9월 10월 11월 12월
Privacy Policy
MCU BASIC ⓒ 2020
모바일버전으로보기