David E Urbasic Performance Critical MIMO Antenna Solutions For MRM And M2M Applications

Transcription

1 David E Urbasic Performance Critical MIMO Antenna Solutions For MRM And M2M Applications

2 Agenda Applications, Key Market Drivers, Market+Data Rate Growth MIMO Technology Is Critical For High Data Rate Applications What Is MIMO What drives MIMO antenna system form factor Key Performance Factors in selecting MIMO antenna VSWR/Efficiency Gain Pattern Consistency Element De- Correlation, Element Envelope Correlation Installation/Implementation GPS Performance Tradeoffs With Each Approach Implementing MIMO Antennas Form Factors Performance Tradeoffs Available Solutions Summary 2

3 Mobile Resource Management MRM: Realized Benefits Drive Expanding Applications Tracking, Location, and Control Protect Equipment Investment Remote Interface and Control Vehicle Health Instant reporting of active and pending OBD trouble codes Tracks Preventative Maintenance Requirements Route Planning Pinpoint pick up and delivery times Ongoing route optimization Dynamic Re-routing Driver Performance Activity and Safety Management Manage Fuel Usage Time Clock and Reimbursement Appointment Accountability Health & Safety Management Temperature controlled equipment Transport of hazardous materials Reduce Liability - Increase Safety Dash Cam streaming and capture In-vehicle video capture/stream (Courtesy of the Intelligent Transportation Systems Joint Program Office) 3

4 MRM Market Overview Industry (USA): $10.91 billion in 2013 Approximately 25 Million track able units: 18 Million fleet vehicles; 5 Million commercial trailers; 1.5 Million heavy construction equipment TAM for GPS-based MRM systems by 2015: 5.5 million units* Global Industry is expected to grow at a Compound Annual Growth Rate (CAGR) of 22.8% from 2013 to 2018 (reserachandmarkets.com, October 1, 2013) *A Comprehensive Study of the U.S. Market for Fleet Tracking and Other MRM Products and Services C.J. DRISCOLL & ASSOCIATES 4

5 Performance Critical MRM/M2M: Growth and Demand for Data/Reliability M2M Modules Forecast: 2 Billion by 2018 a 43% CAGR M2M Data Traffic Forecast: 113% CAGR M2M Projected Growth of demand for data almost double versus all devices! 5

6 Typical MRM+MIMO MIMO: Smart Antennas Technology utilizing multiple antennas and multiple radiated signals utilizing various encoding schemes. Signals multipath provides possibility to improve throughput and increase reliability Typical MRM/M2M 2xCellular Antennas on Resource Omnidirectional Broadband/MultiBand GPS Location Reporting low grade timing Secondary 2x WIFI MIMO system Cellular Offloading Vehicle Hotspot Data download LTE1 LTE2 WIFI1 WIFI2 GPS 6

7 Antenna Size and Element Spacing, Driven by λ=c/f The advantages of MIMO rely element de-correlation. Because an MRM system requires an Omnidirectional Antenna, much of the de-correlation factor is derived from element spacing. MIMO antenna architecture and platform sizes are driven by the frequency bands in which they operate 700MHz the limiting factor in terms of element spacing and MIMO array spacing can be referenced in terms of wavelengths in this band. Cellular Bands MHz = λ = MHz 1λ@1719MHz= = 1.23λ 4.2 =.61λ GHz 1λ@2.3GHz= = 1.67λ 4.2 =.82λ Bands GHz 1λ@5.5GHz= = 3.7λ 4.2 = 1.8λ GHz 1λ@4.9GHz= = 3.5λ 4.2 = 1.75λ GHz 1λ@2.4GHz= = 1.7λ 4.2 =.86λ Wavelength at 700MHz and resulting minimum integrated antenna form factor.2-.3λ( ).4-.6λ ( ).7-1λ (12-17 ) 7

8 Quantifying MIMO Antenna Performance Antenna Performance Factors VSWR, Efficiency (%) Ratio of radiated power over supplied power. Antenna Gain After losses, the radiation intensity versus isotropic radiator Pattern Quality and Consistency Pattern Performance is a critical feature in maximizing potential MIMO benefits. The mobile antenna patterns should be as uniform as possible. Achieving this while colocated elements is one challenge. The secondary, but non trivial task is designing an element with broad band multiband performance that will perform with some consistency over MHz. In all but the most rare cases, MIMO elements should be identical. Element De-correlation Spatial Separation Port to port isolation Installation/Implementation Required Mounting Method Antenna Sealing, IP rating and build quality Mounting Surface sealing 8

9 Quantifying MIMO Antenna Performance: Efficiency + Return Loss Efficiency (%) Ratio of power radiated from the antenna over power supplied to the antenna. System Implications Energy lost to efficiency and return losses is indeed lost What impacts efficiency? Efficiency Loss Due Feed Cable Test with 1 to benchmark Impact from long run cables can be calculated or measured LMR400, LMR240, LMR195, LMR100 = Not created equal Individual Element Efficiency Element, including truncation for miniaturization Feed Structure Efficiency Loss Due to Mutual Coupling High Coupling Reduces Efficiency Loading unused port Return Loss Quality of the broadband/multiband match of the antenna to a 50Ω system What to expect? What do demand? Depends heavily on form factor. In the least, consistency across each band. With no cable, 70-90% is quite good. Numerous ways to measure/calculate, Comparative Measurements preferred. 9

10 VSWR discussion Two different MIMO antennas, VSWR measured with and without feed cable Cable Length 18 1 Cable Length 18 1 Typical MRM MIMO Antennas: 2:1 VSWR (89% transmitted power), Is a common spec for cellular MIMO antennas due to their broadband/multiband performance requirement. often include significant cable runs back to modem. 17 is often the standard amount of cable preterminated to the antenna. VSWR often specified with long lossy cable attached. Well optimized VSWR performance is a significant design challenge. It is not uncommon have significant performance roll off in the lower 700MHz bands. Often due to over-truncation of element or simply under-optimization. Long system length feed cables can MASK poor Return Loss performance. VSWR(RL) data for antenna qualification should be measured with minimal cable lengths. 10

11 Port to port Isolation Ant1 Ant2 Poor pattern performance can IMPROVE isolation, but will likely decrease the effectiveness of mobile system. Maximizing benefits of MIMO are also dependent on Isolation Isolation in MRM multiport MIMO antennas is largely dependent on Element Spacing vs Frequency Internal and External Feed Losses Pattern Performance: Isolation data must be reviewed with regard to pattern data. Typical isolation at 700MHz Smaller Form Factor, 8-10dB Larger Form Factor, 12+dB Radio manufacturers may have their own Minimum isolation requirements independent of MIMO performance 11

12 Elevation Pattern Performance Broadband Element and Co-location 0 φ 90 φ Case Study: Elevation Patterns taken from one element in MIMO antenna MIMO elements have reasonable separation at 5 (.3λ at 698MHz) 90 φ = plane in which both co-located elements sit. 0 φ = Orthogonal to 90 φ Overlaid patterns MHz Heavy Elevation Pattern Degradation at (heart of low band 4G/LTE) The element is slightly truncated to keep overall height below 4 Conclusion: Element co-location is playing some part in the pattern degradation. Element selection, under optimization, and over truncation may also cause abrupt pattern quality issues. With Broadband/multiband antennas, pattern performance must be reviewed throughout band and particularly at band edges. Pattern deficiencies are not always due to antenna 12 co-location and may be correctable with an improved element design.

13 Peak Gain vs Pattern Performance Comparing Azimuth Ripple Performance in two different Co-Located Omnidirectional Antennas Antenna1 LTE Port1 Antenna2 LTE Port1 90 θ Horizon 90 θ Deep null and wide gain delta. Omnidirectional? Peak Gain: 3.24dBi Average Gain: -.96dBi Max/Min Average: 8.4dB (Ripple:+/-4.2dB) GHz Band: 4.7dB Ripple Worst Case Max/Min: 13.88dB Peak Gain: 2.79dBi Average Gain:.30dBi Max/Min Average: 3.3dB (+/-1.6dB Ripple) GHz Band: 2.34dB Ripple Worst Case Max/Min: 4.49dB Case Study: Antenna1, Antenna2, both cellular MIMO antennas. Antenna footprints similar θ, Azimuth/Horizon Patterns Shown at MHz Conclusion: Peak gain performance is masking other performance problems as exposed by Average Gain and Ripple analysis Gain Specification can be misleading with out reviewing pattern data. Azimuth pattern ripple is one way to quantify the quality of an omnidirectional antenna. 13

14 MRM and the GPS Afterthought GPS can often be incorporated in to multi port MIMO antenna packages, which puts the active GPS module in very close proximity to Cellular MIMO+WIFI antennas operating MHz, with plenty of opportunity for trouble. Insurance: High Rejection(HR) GPS Achieves broad band high rejection performance through Optimized high frequency PCB layout Multistage/Multiband filters Custom tuned Patch element High Performance Shielding Techniques Seek out a purpose built and optimized HR GPS module 100% testing of both GPS performance and OOB Rejection Be weary of commoditized off the shelf modules Potential for varying consistency Not heavily characterized Primary advantages GPS system: Adjacent Bands, Spurious Transmissions, and Harmonics have a reduced potential for interference with GPS signals. System wide: Prevents LNA from supplying heavily amplified out of band signals directly cellular router, system chassis, or vehicle which may reduce performance of other systems. GPS+GLONASS for system flexibility 14

15 Case Study: Swept GPS Gain Measurement Commercial-off-the-shelf vs. Optimized High Rejection GPS Module In band/out of band Gain After LNA Typical COTS Optimized High Rejection Typical Min Rejection performance requirement: fc ± 25MHz fc ± 100MHz 2.4-6GHz Frequency: 20MHz/Div Out of Band Out of Band 15 GPS Receive Frequency

16 Mechanical Considerations Surface Seal Double Sealing Method Preferred Radome Seal Gasket for increased consistency and reliability over glue IP67 Compliance Mounting Stud Single preferred Size, cable choice driven Strain relief Cable Routing and termination in close quarters Avoid cable bend radius violations! Clean terminations that do not rely on heavy amounts of solder 16

17 MIMO System Design Tradeoff: Individual antennas, Integrated package, Form factor Multiple Antenna Solution Allows maximum spacing of antennas on a given platform.5-1+λ Maximizes Potential MIMO Benefits Maximizes De-correlation of antennas Maximizes Port to Port Isolation Low to no pattern impact due to antenna co-location* Easy Maintenance, service/replace individual elements Potential smallest individual antenna footprint Largest overall real-estate requirement Increases system area and number of mounting points/holes Option 1 Single Package, Large Form Factor Element Spacing.5λ+ at Lowest frequency Maximized element spacing in single reasonably sized package Single Mounting Location, Single HOLE* Easier to minimize Pattern Problems due to Antenna Co-location* Larger Antenna Footprint Antenna Footprint = Real-estate required Option 2 Single Package, Small Form Factor Element Spacing.2-.5λ Single Mounting Hole Small Antenna Footprint Minimal element spacing to still achieve some benefits of MIMO Reduced De-correlation of antennas Difficult to Mitigate Pattern Performance Impact due to Antenna Co-location Micro/Conformal/Covert/Embedded Option 3 Option 4 17

18 Option1 Solution Individual Antenna Elements BMLPV-MBLTE-HP MHz 2:1 VSWR with no cable Multiple Antennas Phenomenal Efficiency>80% Optimally Placed 3.4 tall (36x86mm) High pattern stability over all bands N-female for direct attach Extremely Rugged and IP67 Compliant 8171D-HR GPS L1 and GLONASS L1 Frequencies 2dB noise figure 26dB LNA Gain 2.36 x.83 (60x21mm) Industry Leading out of band rejection TNC bulkhead termination for maximum feed options Low Profile and IP67 Compliant BMLPVDB Adds MIMO WIFI Capability 18

19 Option 2 Solution.5λ, Multiport Co-located MIMO Antenna GPSDLTE-LFF True.5λ design at 698MHz Maintains Single Hole Mount MHz 2:1 VSWR with no cable Phenomenal Efficiency>75% Isolation 12dB Maintains low ripple Omnidirectional Patterns 3.5 tall x10 x3 High pattern stability over all bands Factory terminated with LMR195 or LMR240 Integrated High Rejection GPS Optional integrated dual band WIFI MIMO elements Ruggedized mobile applications including rail Conforms to contoured surfaces NO FOAM gasket Double seal on mounting surface Single Large Form Factor Antenna: Easy Install 19

20 Option 3 Solution.25λ, Small Form Factor Cellular MIMO Antenna Single Small Form Factor Antenna: Easy Install GPSHPDLTE-SF: LTE MIMO + HR GPS MHz.25λ design at 698MHz Single Hole Mount Broad Band VSWR Performance with no cable Maintains Pattern/Gain Performance down to 690MHz Isolation 8dB while maintaining low ripple Omnidirectional Patterns 3.4x5.2 (86x132mm) Factory terminated with LMR195 or LMR100 Integrated High Rejection GPS IP67 Compliant Double Mounting Surface Seal GPSHPDLTEMIMO-SF Adds MIMO WIFI with 2x DualBand 2.4/5.8GHz 20

21 Summary MRM and M2M Applications Are Growing Exponentially Driving Data Intensive Applications MIMO Is a Critical Technology That Enables High Data Throughput For Various Wireless Standards (WLAN, LTE etc.) An overview of MIMO Antenna Parameters What to look for in a properly optimized antenna Understanding the compromises between even well optimized solutions. PCTEL Provides A Wide Variety Of High Performance MIMO Antenna Solution For Performance Critical Applications. 21