Radar System Design and Data Processing

1. We now learn about the radar hardware basics and then (next week) treat the digital processing of: Radar range gating, signal and noise, coherent complex digital sampling, range-time matrix, digital radar data display, coherent integration, coding /decoding complex covariance function, complex Doppler spectrum, parameter deduction. Basics of phased antenna arrays, radiation pattern calculation, radar interferometry and imaging. Finally a summary of radar methods for atmosphere and ionosphere research and explanation of some typical results, incl. coherent and incoherent scatter.

2. Radar System Design and Data Processing

5. The ESR Receiver - Cryo-cooled (15 K) GaAsFET preamplifier, feeding into three parallel, high dynamic range dual superhets, employing + 23 dBm balanced mixers 1st IF = 70 MHz, 2nd IF = 7.5 ± 1.8 MHz - Receiver chain 1 dedicated to ion linereception fixed at 500 ± 1.8 MHz - Chains II and 111 used for plasma linereception, tunable over 484 – 516 (± 1.8) MHz - Sample of transmitted signal detected at first mixer - 2nd IF output signals at -10 dBm digitized by continuously running10 MHz, 12 bit A/D converters - Each 10 MHz data stream fed into several digital back end channels in parallel - Detection at nonzero IF results in: DC offset, gain imbalance, quadrature phase errors and unequal filter responses are avoided altogether. - Major advantage over muIti-channel base-band detection system

6. The ESR Antenna - 32 m shaped Cassegrain geometry, custom design - Designed, built by Kamfab-NTG-Ticra- Dielectric - high gain, 42.5 dBi at 500 MHz - low system noise temperature, 65 K at 500 MHz - low sidelobes - mechanically fast: 2.2 -2.8 degrees per second, can swing through 180 degrees in elevation - Dedicated real time control computer running OS-9 - Position servo loop closes numerically in computer

9. The ESR Transmitter • - Designed / built by Harris TVT, Cambridge, U.K. • - Basically a combination of 4 (8) standard UHF • TV transmitters, slightly modified, producing 500 kW (1 MW) • at 25 % duty cycle • (highest ever used in a pulsed ISR). • Pulse modulator is all solid state, runs at 25 kV • - Instantaneous power BW is 500 ± 2 MHz, • range resolution down to 40 m can be achieved • - Advanced DDS / heterodyne exciter providing • - theoretically unlimited number of TX frequencies • - pulse-to-pulse multi-frequency phase coherency • - linear chirp (later) • - possibilities for adding pseudo-random BPSK • - Transmitted waveform sampled and processed by receiver: • corrections for transmitter effects in the data analysis can • be done exactly, not only from models (a first as a routine • feature) • - Designed for unattended operation

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15. LATEST REVISION OF RECEIVER’S BLOCK DIAGRAM IF MON1 I-1 VA LPF LIM DC BL LN BPF MIX IFA BL ATT IFA DC QM LIM LIM LIM LIM RF IN1 Q-1 LPF VA IF MON2 I-2 VA LPF LIM DC BL LN BPF MIX IFA BL ATT IFA DC QM RF IN2 Q-2 LPF VA IF MON3 I-3 VA LPF LIM DC BL LN BPF QM MIX IFA BL ATT IFA DC RF IN3 Q-3 LPF VA LIM AMP 120 MHz OUT AMP 1:4 DIV LIM AMP 1:4 DIV MIX 150 MHz OUT NC 30 MHz 1:4 FREQ DIV AMP REF (Obtained from MO) 120 MHz MO 30 MHz OUT NO DC SUPPLY Generation of 120+ΔF and 150+ΔF signals Default radar operation freq is 150 MHz For generation of 150+ΔF signal, LO 120+ΔF signal injected via LO IN 220 Volts AC Mains LO SWITCH LO IN BL SW CONTL

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17. MEILHAUS ME-4660S PCI DAQ CARD

18. The ESR Digital Signal Processor - Every four back end channels are served by a VME DSP board containing: - two T.I. TMS 320C40 DSPs (2 x 80 Mflops) - 2 x 12 MB local RAM + 16 MB of 21 global dual-port RAM - six DMA controllers + VME bus interface - DSP computes the autocovariance coefficients of the filtered sample stream, averages and stores these in lag profile format or as raw data - DSP also controls NCO and filter settings on a pulse-by-pulse basis - Data output is over dedicated 10 MB/sec DMA link into four CPU, SparcServer 1000

19. transmitter exciter

20. The ESR RX Digital Back End - First known use of fullydigital back end in a scientific radar receiver - Each digital back end channel contains: - a tunable numerical oscillator - a digital complex multiplier - a complex digital FIR filter / decimator - a 2 x 256 kWords ping-pong sample memory

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22. DIAGRAM BLOK 150 MHz 1 kW T-R MODULE

23. TEST SETUP OF 150 MHz 1kW Transmitt MODULE

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26. 4-PORT DISTRIBUTION SYSTEM FOR THE TX ANTENNA OF THE LAPAN-TRAINERS VHF RADAR Yagi antenna Yagi antenna Yagi antenna Combiner II 1 (2,5 kW) Combiner II 2 Combiner II 4 Combiner III 10 kW RX TX 3 kW TX 1 kW TX 1 kW TX 1 kW

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28. RC Remote Control PC Lab View Software DSP Digital Signal Processing PRP TRAINERS - Radar-System( Phase 1/ Phase X ) RFP ADC FLP (Phase 1) PA 10KW MO φ 0/180º ANT ( TX ) 148 MHz 10 W 100 W 1 KW TX 0º 90º I ANT ( RX ) LNA Q RX 1 Picture 0-1 Radar System Schematic

29. To follow next: Radar range gating, coherent complex digital sampling, range-time matrix, digital radar data display, coherent integration, complex covariance function, complex Doppler spectrum, parameter deduction. Basics of phased antenna arrays, pattern calculation, radar interferometry. A final summary of radar methods for atmosphere and ionosphere research.