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Figure 1. Bistatic and multistatic radar geometry configuration RTRT TXTX RXRX TXTX R L Bistatic Radar: The transmitting and receiving antennas are not.

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Presentation on theme: "Figure 1. Bistatic and multistatic radar geometry configuration RTRT TXTX RXRX TXTX R L Bistatic Radar: The transmitting and receiving antennas are not."— Presentation transcript:

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2 Figure 1. Bistatic and multistatic radar geometry configuration RTRT TXTX RXRX TXTX R L Bistatic Radar: The transmitting and receiving antennas are not co-located.

3 Air traffic control/detection – important for being able to detect outer-atmospheric phenomena. Detect ionospheric disturbances Remotely sense auroral turbulence, density irregularities in the E and F regions of ionosphere, and meteor trails [1]. Traffic monitoring (law enforcement)

4 FM radio broadcasts - monitor disturbances in the ionoshpere Digital Audio Broadcasts (DAB) – high transmission power ~ 5 kW and wide bandwidth ~1.54 MHz Analog TV broadcasts Global Positioning Satellites Cellular telephones

5 ParameterValue Transmit ERP (P T G T )4 kW (CP); 250 kW (Wr) Receive Antenna Gain (G R )8 dB Wavelength (λ)3 m Assumed Bistatic RCS (σ B )20 m 2 Receiver Bandwidth (B)200 kHz Receiver Noise Figure (F n )6.8 dB Assumed System Losses10 dB Baseline Length (L)11.8 km (CP); 37 km (Wr) Integration Time (T int )1 s Effective Bandwidth (B eff )75 kHz Processing Gain (G P )48.8 dB Table 1. Operating parameters the UCL PBR radar [1] Given a minimum signal-to-noise ratio (SNR) of dB, determine the maximum distance to the target from the transmitter as well as from the receiver.

6 To solve this problem, well need to use the bistatic radar equation along with the Cassini range equation. Figure 2. Oval of Cassini [2] CP: Wr:

7 Figure 3. PBR sensitivity plot for the FM radio transmitter at Crystal Palace (a), and Wrotham (b) [1] (a) (b)

8 Low cost - no designated transmitter Covert operation Reduced electromagnetic pollution Potential detection of stealth targets

9 Complicated geometry Direct signal interference (DSI) – can mask the signal of interest Time-varying characteristics of received signal – e.g. periods of silence (FM), power outage, leakage from adjacent channels, and soil moisture are all out of our control. Figure 4. The 20 MHz FM broadcast band ( MHz). [1]

10 Possible Solutions Quiet spectrum with high transmitted power. FM music station – decreases periods of silence Multiple radio channels – increases robustness/SNR (through integration) however, using MF increase the DSI

11 Possible Solutions Cross polarization – observe using horizontal polarization if the transmit polarization is vertical Array nulls Shielding by topography – select a location with the weakest DSI

12 Center the antenna so that the DSI is received by a null and not the main beam. For returns close to grazing angles, the direct and reflected signals will tend to cancel each other due to the imperfect nature of the ground. Targets are at high altitudes where the antenna gain is high.

13 Figure 5. Topographical map showing radar (red X), illuminators (blue +) and airport (red O) posistions [3] Adelaide system: Built by the University of Adelaide, this system was designed to test the potential of DAB (Digital Audio Broadcasting) for radar applications. Located at the University of Bath, this system monitors air traffic at the Bristol airport.

14 Figure 6. Propagation loss from Bath (at 0 km) to Wenvoe (at 64 km). [3] Figure 7. Propagation loss from Bath (at 0 km) to Pur Down (at 20 km). [3]

15 Total DSI power at any given location can be determined through simulations. This allows us to select a location with minimal DSI. Figure 8. DSI contributions from all sources [3]

16 Figure 9. DSI contributions from Naish Hill and Mendip [3] Figure 10. One way loss from low DSI site to airport [3] Targets above 1000 m and at least 20 km away can be detected, assuming 120 dB loss is low enough for passenger jet observations.

17 Figure 11. One way loss at 900 m around a low DSI site [3] Figure 12. One way loss at 900 m around an alternative low DSI site [3] Placing multiple receivers at various low DSI sites could provide a more complete air picture [3].

18 [1]C.J. Baker and D.W. OHagen, Passive Bistatic Radar (PBR) Using FM Radio Illuminator of Opportunity, Dept. Elect. Eng., London Univ., London. [2]Wisstein, Eric W. Cassini Ovals. From MathWorldA Wolfram Web Resource. [3]C. Coleman, Mitigating the Effect of Direct Signal Interference in Passive Bistatic Radar, Dept. Elec. Eng., Adelaide Univ., Adelaide.


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