Radar System Impacts on Spectrum Management

Transcription

1 Radar System Impacts on Spectrum Management National Spectrum Management Association Mitchell Lazarus May 13, 2014

2 Radar: Basic Principle Radio signal reflects from target, returns to receiver gives direction to target, distance to target 1

3 History Invented by Robert Watson-Watt around 1935 key development: use of oscilloscope for display Greatly improved by U.S. work during World War II Military and civilian applications mushroomed through 1950s and 60s and beyond Modern wideband radar appeared in 1970s first application: ground penetrating radar. 2

4 Major Categories Terminology Radiolocation Radar Power watts MW microwatts Bandwidth Range < 1 khz tens of meters hundreds of km tens of MHz GHz cm meters Licensed yes no 3

5 Radiolocation (licensed, high-powered radar) 4

6 Strong Signal Weak Return Low signal level at receiver: target t absorbs b and scatters signal return drops off with distance as 1/r 4 narrow beam & small antenna high frequency high space attenuation Weak return signal requires high transmitter power. 5

7 Does Not Share Well with Others 1. High transmitter power tends to interfere with other users 2. Low receiver power susceptible to interference from other users 3. High public interest many applications important to human safety: defense, air traffic control, maritime safety, weather prediction, etc. Causes interference; demands high protection combination makes sharing difficult. 6

8 FCC Radiolocation Frequencies khz khz Fed radar khz Fed radar khz shortwave MHz S ISM, Wi-Fi, MSS satellite, more MHz S Fed radar; proposed Citizens Broadband; PCAST MHz C Fed radar, U-NII, more ,550 MHz X Fed radar, more GHz Ku Fed radar, more GHz Ku Fed radar, more GHz K Fed radar, ISM, amateur, unlicensed GHz Ka Fed radar, more GHz Fed radar, more FCC applicants can also request Government frequencies 7

9 FCC Radiolocation Technical Rules Rules: Power: considered and authorized on a case by case basis, 47 C.F.R (r) Bandwidth: reviewed and authorized on a case-by-case basis, 47 C.F.R (b)(5) (table) n.2 Modulation: any type may be authorized upon a satisfactory showing of need, 47 C.F.R (k) Little guidance for applicants. 8

10 FCC Radiolocation Frequency Coordination FCC rules: no frequency coordination (unlike other shared-spectrum services Private Land Mobile, Private Operational Fixed microwave, etc.) FCC does not check applications for interference FCC coordinates with NTIA for Government users applicants have no advance assurance of successful coordination Some licensees report incoming interference. 9

11 Federal Radiolocation Subject to Manual of Regulations and Procedures for Federal Radio Frequency Management (Redbook) little detail Administered by NTIA through IRAC Proposals reviewed by either: IRAC Spectrum Planning Subcommittee ( major systems) IRAC Frequency Assignment Subcommittee (other systems) Process largely opaque to outsiders. 10

12 Radiolocation Sharing Methods In principle: apply separation radius avoid axis of radar beam (apply keyhole shape) exploit low duty cycle In practice: most radars pulse and/or rotate others can operate when beam is off or pointing away (could let collocated radars share frequency) only 2,017 active FCC licenses large fraction: police speed enforcement bigger sharing obstacle: federal radars many federal locations not disclosed. 11

13 Doppler Radar f 2f (/) (v/c) 60 mph target shifts frequency one part in 5.6 million. for GHz police radar, shift is 4 khz 12

14 TV Doppler Weather Radar Detects position, size, speed, and shape of moisture particles Many operate at GHz. 13

15 Other Doppler Weather Radars Terminal Doppler Weather Radar (TDWR) detects wind shear at major airports operates at MHz history of interference from unlicensed U-NII devices NEXRAD wider coverage, less resolution than TDWR operates at MHz DOPRAD maritime weather; some TV weather operates at GHz. 14

16 Public Safety Application Handheld sensing device sees through one foot of concrete detects people moving or an unconscious victim breathing steps over 200 frequencies from 3101 to 3499 MHz every 18.5 ms Licensing limited to state and local police and firefighters. (L3 Communications Cyterra;Akela,Inc.) 15

17 Mining Application U.S. model operates at GHz (wideband; licensed) identifies rock strata monitors site stability. (Reutech Radar Systems Ltd.) 16

18 Emerging Applications Support for UAV (drone) development and operation Bird detection ti near wind farms, solar power generation, airports birds + airplanes = serious safety threat. (SRC, Inc.) 17

19 Low-Power, Unlicensed Radar 18

20 Principles of Pulse Radar Short pulses: high precision wide bandwidth (tens of MHz) low energy per MHz. 19

21 Applications UWB ground penetrating radar, GHz UWB in-wall imaging, i GHz UWB through-wall imaging, below 960 MHz or * GHz UWB surveillance systems, ,600 MHz UWB medical imaging, GHz UWB vehicle radar GHz *license req d Wideband, GHz Level probing radars , , GHz Vehicle radar, , , , GHz Fixed field disturbance sensors, GHz Airport foreign object debris, ground vehicles, GHz Airport foreign object debris, GHz*. 20

22 Spectrum Coexistence Low power limits: many at 75 nw measured per MHz device can emit far more power Allowed in restricted bands Wideband can threaten many victim receivers unlicensed and ubiquitous (esp. vehicle radars) hard to find if interference occurs Mitigating factors: little energy into victim receiver bandwidths most applications are close to the ground high frequencies give high space attenuation, high ground clutter attenuation. 21

23 Level Probing Radar 1 Measure quantity of materials, liquid depth outdoors unlicensed wideband d operation o traditional rules set limit on transmitted (downward) emissions interference arises from scattered (horizontal) emissions difficult to measure reliably. 22

24 Level Probing Radar 2 FCC rules require boresight measurement seeking max. horizontal emissions of 41.3 dbm / MHz boresight emissions limits exceed that level by db, depending on band allows for losses due to scattering, etc. More precise measure of potential interference rules took effect April 7. 23

25 Conclusion New applications are expanding licensed radiolocation FCC (with NTIA) should systematize the technical rules and license approval process applicants need more predictability, better interference protection Unlicensed wideband radars are spreading rapidly FCC should continue to encourage new applications, especially at higher frequencies. 24

26 Thank you! Mitchell Lazarus