After choosing the most appropriate receiver for your application from ...

After choosing the most appropriate receiver for your application from the Receiver Survey in the January issue of GPS World, you may need an antenna, too. We have collected key specifications for 493 antennas from 32 manufacturers. We publish the Antenna Survey each year in our February issue. To recommend improvements or to be listed in the survey next year, please email [email protected].

FOOTnotes 1



2





GPS L1 frequency 1575.42 MHz GPS L2 frequency 1227.60 MHz

abbreviations 3



A single voltage standing wave ratio (VSWR) figure indicates a combined antenna and amplifier.

4



Noise figure is expressed in maximum decibels.

5



L/D = lightning/diode.

User environment and applications: A = aviation D = defense E = meteorology G = survey/GIS L = land M = marine N = navigation O = other P = other position reporting R = real-time DGPS reference S = space T = timing V = vehicle/vessel tracking

www.gpsworld.com

cm: centimeter dB: decibel Ø: diameter ft: foot g: force of gravity g: gram Hz: hertz in: inch kg: kilogram lb: pound m: meter mA: milliampere max: maximum MHz: megahertz min: minimum mm: millimeter na: not applicable nr: no response qty: quantity RHCP: right-hand circular polarization typ: typical

February 2013 | GPS World

39

Advertorial

Selecting the Right GNSS Antenna

W

e recently met with Gordon Ryley of NovAtel to provide additional information on how to select the ideal GNSS antenna for your application.

Where do you start? The antenna you choose must match your receiver’s capabilities and specifications. Since the antenna behaves both as a spatial and a frequency filter, it will have significant impact on the performance of the GNSS receiver. Your application will also help determine form factor and antenna performance. What GNSS constellations and signals do I want to receive? Active GNSS constellations include GPS, GLONASS, and BeiDou. Galileo and QZSS will soon grow to full operation. Position correction services, known as Space Based Augmentation Services (SBAS), Gordon Ryley transmit on geostationary satellites in Antenna/Smart Antennas orbit around the earth. Product Manager Each of the constellations and SBAS have their own signal frequencies and bandwidths. Some of these frequencies are shared (e.g., GPS L1, WAAS (SBAS), Galileo E1). Choose an antenna that covers the signal frequencies transmitted by the constellation and bandwidth supported by your GNSS receiver. Multiple frequency antennas are used to help correct for ionospheric errors in RTK applications. The signal bandwidth of your antenna is important as many GNSS receivers take advantage of the full signal power transmitted. NovAtel’s GNSS receivers utilizes a patented Pulse Aperture Correlator technology (PAC) which uses a wider signal bandwidth to mitigate position errors caused by multipath and can support precision carrier phase RTK algorithms with centimetre accuracy. Many basic GNSS receivers only look at the constellations coarse acquisition (C/A) code and only require a narrow bandwidth of a few MHz and as such are restricted to positional accuracies of a few metres. What amount of antenna gain do I need? Gain is a key performance indicator of a GNSS antenna. A minimum gain is required to achieve a minimum C/N0 (carrier-to-noise ratio) to track the GNSS satellites. The antenna gain is directly related to the overall C/N0 of the navigation GNSS receivers. Hence, antenna gain helps define the tracking ability of the system.

40

GPS World | February 2013

Plot of Good and Poor Antenna Phase Centre Variation over Elevation Angle

GNSS receiver manufacturers will typically specify the expected RF input level required for optimum performance. This level is important to avoid underdriving (causing poor C/N0) or overdriving (causing limiting or distortion) the front end of the receiver. Nearly all receivers have automatic gain control, but there is only so much dynamic range in the system and the antenna gain, including cable losses, needs to be considered carefully. Why is element gain so important? The element gain defines how efficient the antenna element is at receiving the signals. In any signal chain, you are only as good as the weakest link, so an antenna with low element gain might be compensated by an increased low noise amplifier gain, but the signal to noise ratio or C/N0 is degraded. How important is antenna beamwidth and gain roll-off? Very important. Gain roll-off is a factor of beamwidth and specifies how much the gain changes over the elevation angle of the antenna. From the antenna’s point of view the satellites rise from the horizon towards zenith and fall back to the horizon. The variation in gain between zenith (directly overhead) and the horizon is known as the gain roll-off. Different antenna technologies have different gain rolloff characteristics. Patch antennas can track down to low elevation angles such as 10 degrees. Most choke ring antennas www.gpsworld.com

Advertorial

will typically not receive signals below 30 degrees with the exception of NovAtel’s GNSS-750 which can track down to and below the horizon. What is Noise Figure? Noise figure directly impacts the C/N0 of the GNSS receiver. The lower the overall noise figure the better the C/N0 and tracking capability. The noise figure is the difference between the signal-to-noise ratio at the input and output of the component and identifies how much additional noise is being added into the signal through the system or its individual components such as the low noise amplifier. Good antennas will have a noise figure less than 3dB. What is VSWR? The voltage standing wave ratio or VSWR is a measure of how much power is reflected back upon the transmission line (coaxial cable between receiver and antenna) and indicates how well the antenna is matched to a specific impedance, typically 50 ohms. An ideal VSWR of 1 indicates that a perfect match exists and that no power is reflected back from the antenna. Why should I be concerned about multipath rejection? Positioning errors are caused by multipath, which are multiple reflections of the GNSS signal off of nearby or far objects. Multipath degrades the positioning accuracy and should be suppressed. For optimum multipath rejection, an antenna should be mounted as close to the horizontal surface as possible and away from reflecting objects including water, antenna masts, air conditioners, ventilation shafts, etc. Choke ring antennas offer high multipath rejection due to their unique concentric ring design that block out multipath signal reflections to the antenna element. The Axial Ratio also defines the antenna’s ability to reject multipath-generated replicas of the original GPS signal. A good GNSS antenna provides a low axial ratio not only at each of the GNSS frequencies, but also over all elevations angles of the satellites in view. NovAtel’s GPS-700 series of antennas maintains an axial ratio as low as 3dB at azimuth or horizon. What is phase center stability and why is it important? The phase center of the antenna is the point where the signals transmitted from satellites are collected. When your receiver reports a location fix, that location is essentially the phase centre of the antenna. If you are specifying an antenna for use with geodetic survey or a reference station application, phase center offset (PCO) and phase centre stability or variation (PCV) are important. www.gpsworld.com

Plot of Good and Poor Antenna Phase Centre Offset over Elevation Angle

The electrical phase center of any antenna will vary with the position of the transmitting signal it is receiving by as much as a few millimetres. As GNSS satellites move across the sky, the electrical phase center of the signal received will typically move with the satellite position unless the antenna has been carefully designed to minimize PCO/PCV. The Phase Center Offset with respect to the antenna reference point (ARP) is the difference between the mechanical center of antenna rotation and electrical phase center location. The PCO is also frequency dependent which means that there can be a different offset for each signal frequency. The Phase Center Variation identifies how much the phase center moves with respect to the satellite elevation angles. Many users can accept accuracies of less than a metre so these small phase center variations cause a negligible amount of position error. But if you require high precision, Real Time Kinematic (RTK) receivers can achieve position accuracies of 2-4 cm and a few millimetres of phase center error translates to a 10-15% error in reported position. For RTK survey applications, geodetic grade antennas such as the NovAtel GPS-70x and Antcom G8 series offer superior PCO/PCV performance. For reference station applications a NovAtel GNSS-750 antenna is ideal. How does my application affect my antenna choice? An antenna may have to meet certain environmental, mechanical, and operational requirements. Size and weight are also important considerations. Go to novatel.com/antennas to learn more. See also the antenna feature chart on page 29. February 2013 | GPS World

41

antenna survey 2013 | Sponsored by Manufacturer

Model

AeroAntenna Technology, Inc. www.aeroantenna.com

Allis Communications Co., Ltd. www.alliscom.com.tw

42

Intro. Date

UserEnvir. 1

Size: Length x Width x Height

Weight

Frequency / Bandwidth 2

VSWR 3

Axial Ratio (dB)

Gain / Gain with Amplifier (dB)

Pattern

Noise Figure (dB) 4

AT1675-7 L1 / L2 GPS & GLONASS

2007

G

7.25 x 3.20in

1.36 lb

1590 ± 25 & 1238 ± 21.5 MHz

≤2.0:1

3 dB Max @ Boresight

38 dB

RHCP

2.4 dB Max

AT1675-8

2009

A

4.70 x 3.00 x .75in

8 oz

1268± 12 MHz & 1590± 125MHz

≤2.0:1

as above

42 dB

RHCP

2.5 dB Max

AT1675-17 GPS / GNSS ANTENNA

2000

AG

4.70 x 3.0 x .75in

8 oz

1590 ± 25 & 1238 ± 21.5 MHz

≤2.0:1

as above

26 & 40 dB

RHCP

2.5 dB Max

AT1675-19

2010

LD

2.20 x .57in

75 g

1565-1607 MHz

≤2.0:1

as above

26 db

RHCP

2.5 dB Max

AT1675-32 GPS / GNSS ANTENNA

2009

LG

5.75 x 2.46in

1.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-80 (TSO ) GPS / GNSS / L-BAND ANTENNA

2008

AG

4.70 x 3.0 x .92in

10 oz

1570 ±45 & 1238 ±21.5 MHz

≤1.5:1

as above

43 dB

RHCP

2.6 dB Max

AT1675-116

2010

LG

3.5 x .84in

200 G

1551 -1615 MHz

≤2.0:1

as above

43 dB

RHCP

2.5 dB Max

AT1675-120 GPS / GNSS CHOKE RING 2009

LG

14 x 13in

11.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-180

2011

A

4.31 x 1.46 x 5.55

1565-1607 MHz & 1217-1260 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT1675-182 GPS / GNSS ANTENNA

2009

LG

5.75 x 2.46in

1.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-301

2009

LG

5.250 x 3.911in

1 lb

1565-1615 / 1217-1260 MHz & 9.5-10 GHz

≤2.0:1

as above

38 dB

RHCP

2.6 dB Max

AT1675-304

2012

LD

2.61 x 1.05

4.47 oz

1525-1607 MHz

≤2.0:1

as above

28 dB

RCHP

2.5 dB Max

AT1675-339 L1 / G1

2010

LG

7.5 x 2.8in

1 LB

1565-1610 MHz

≤2.0:1

as above

26 & 38 dB

RHCP

2.5 dB Max

AT1675-381 GPS / GNSS

2009

A

5.75 x 2.46in

1.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-382 GPS / GNSS ANTENNA

2008

LG

5.75 x 2.46in

1.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-383 GPS / GNSS

2009

LG

5.75 x 2.46in

1.00 lb

1570±45 & 1164-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-450

2011

LG

3.5 X .84in

8 oz

1565-1607 MHz & 1217-1260 MHz

≤2.0:1

as above

26 and 39 dB

RHCP

2.6 dB Max

AT1675-504

2012

LD

2.61 x 1.05

4.47 OZ

1525-1607 MHz & 1217-1260 MHz

≤2.0:1

as above

26 & 36 Db

RHCP

2.5 dB Max

AT1675-539 GPS / GNSS

2010

LG

7.5 x 2.8in

1 LB

1565-1610 & 1164-1260 MHz

≤2.0:1

as above

26 & 38 dB

RHCP

2.5 dB Max

AT1675-540 GPS / GNSS

2011

LG

7.50 x 2.88

1.00 Ib

1525-1610 & 1160-1253 MHz

≤2.0:1

as above

39 dB

RHCP

2.6 dB Max

AT3075-68

2010

LG

3.06 x 3.25in

0.6 lb

1525-1585 MHz +USCG / DGPS

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT2775-80 (TSO) L-Band / GPS ANTENNA

2008

AG

4.70 x 3.0 x .92in

10 oz

1555± & 1238 ± 21.5 30 MHz

≤2.0:1

as above

43 dB

RHCP

2.5 dB Max

AT2775-94 L1 / L2 GPS

2005

AL

3.44 x 2.19 x .77in

.34 lb

1575 & 1227± 10 MHz

≤2.0:1

as above

43 dB

RHCP

2.5 dB Max

AT2775-264

2009

D

1.20 x 3.22in

7 oz

1575 & 1227± 10 MHz

≤2.0:1

≤2.0:1

26 dB

RHCP

2.5 dB Max

AT2775-203 L1 / L2 GPS

2005

L

2.98 x 2.17 x 1.49in

4.47 oz

1575 & 1227± 10 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT2775-304 L1 / L2 GPS

2009

LD

2.20 x .57in

4.47 oz

1575 & 1227± 10 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT2775-382 GPS L1 / L2 and L-BAND

2001

LG

5.75 x 2.46in

1.00 lb

1555±30 & 1217-1237 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT2775-457

2007

L

2.64 x 1.69 x .69in

131 G

1575 & 1227± 10 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT2775-478 L1 / L2 GPS

2009

LD

1.35 x 1.35 x .54in

40 g

1575 & 1227± 10 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT1621-262 GPS / IRIDIUM

2005

VL

3.44 x 2.19 x .77in

4.5 oz

1575 & 1621± 5 MHz

≤2.0:1

as above

26 dB

RHCP

2.5 dB Max

AT575-234 L1 GPS TSO C190

2008

A

4.70 x 3.0 x .75in

8.0 oz

1575±10 MHz

≤1.5:1

as above

29.5 dB

RHCP

2.5 dB Max

AT575-493 L1 GPS TSO C190

2007

A

4.68 x 3.00 x .66in

7.0 oz

1575± 10MHz

≤1.5:1

as above

26 dB

RHCP

2.5 dB Max

AT8075-4 GPS / GSM

2009

VL

3.45 x 2.20 x 2.5in

.80lb

1575 / GSM QUAD BAND

≤2.0:1

≤2.0:1

26 dB

RHCP

2.5 dB Max

AT2300-126 L1 / XM TSO C190

2008

A

4.70 x 3.0 x .75in

8.0 oz

1575&XM± 10 MHz

≤1.5:1

as above

29.5 dB

RHCP

2.5 dB Max

M812B

2004

N

48 x 40 x 13mm

42

1575.42MHz / 20MHz

1.5:1

3 dB max

12

omni at -90°, >

CCAH32ST04

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32ST05

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32ST12

1999

T

90.0mm Dia x 98.4mmH

200g

1575.42 + / - 1.023 MHz

1.5 typical, 2.5 maximum

3dB typical 6dB maximum

38dB typical 30dB minimum

RHCP

1.8dB typical, 2.1dB maximum

CCAH32ST13

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32ST14

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32ST15

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32ST16

1999

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

CCAH32NT21

2010

T

90.0mm Dia x 98.4mmH

200g

1575.42 + / - 1.023 MHz

1.5 typical, 2.5 maximum

3dB typical

34dB typical, 27dB minimum

RHCP

4dB typical, 5dB maximum

CCAH32NT24

2010

T

Same as above >>

>>

>>

>>

>>

>>

>>

>>

GPS-L1L2-28MAG

2011

D,L,O, V

2.75” D x 0.98” H

6.6 oz

GPS L1 / 10MHz, GPS L2 / 10MHz

2:1

0 dBi

RHCP

GAS-1

1998

NDAMOP

CRPA=350mm ø AE=220x60x330mm

CRPA 3.8Kg, AE 4kg GPS L1/GPS L2

nr

nr

7-40dB

nr

Navshield

2005

NDAMOP

CRPA=350mm ø AE=220x60x330mm

CRPA 3.4Kg, AE 4.5kg

GPS L1/GPS L2

nr

nr

7-40dB

nr

nr

Landshield Analogue

2011

LMDNOPTV

115mm ø x 50mm

GPS L1

nr

nr

7-28dB

nr

nr

Landshield Digital

2011

LMDNOPTVA

115 ø x 50mm

GPS L1

nr

nr

7-38dB

nr

nr

SAS

2009

DAMNOP

150x110x80mm

GPS L1/GPS L2

nr

nr

7-38dB

nr

nr

MaxiNav

2000

DGLMV

110 x 18mm

157.5 ± 5 MHz

>

>>

>>

>>

N

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

N

>>

>>

>>

>>

>>

>>

>>

>>

>>

TNC

>>

>>

>>

>>

5V + / -0.5V

20mA typical 27mA maximum

-40 to +85 C

Sine Sweep, 1G, 33 to 50 Hz each axis

Y

Y

TNC

nr

Pole mount

Contact Panasonic

Antenna

>>

>>

>>

>>

>>

>>

N

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

N

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

TNC

>>

>>

>>

>>

>>

>>

>>

>>

>>

>>

TNC

>>

>>

>>

>>

5V + / -0.5V

23mA typical 30mA maximum

-40 to +85 C

Sine Sweep, 1G, 33 to 50 Hz each axis

Y

N

TNC

nr

Pole mount

Contact Panasonic

Enhanced Filter Antenna

>>

>>

>>

>>

>>

>>

N

>>

>>

>>

>>

2.5-5.5 VDC

37mA typ, 50mA (max)

-40 to +85

Mil Std 810F, Method 514.5, Procedure II, Category 5

Y

nr

SMA F

na

Magnetic < 20lb pull force

425

4.5-5.5 VDC

40mA Nominal

-40 to +85

nr

Y

nr

TNC F

na

Surface mount four hole pattern

320

5-28 VDC through connector

25 mA typ., 40 mA max @ 26.5 dB / 40 mA typ., 60 mA Max @ 40 dB

-40 to +85

nr

Y

nr

TNC F

na

Through hole 5 / 8-18UNC-2A thread

385.5

3 - 13.5 V

20 mA nominal;

nr

nr

nr

nr

nr

nr

TNC

nr

nr

nr

nr

nr

nr

nr

nr

nr

nr

TNC

nr

nr

nr

nr

nr

nr

nr

nr

nr

nr

SMA

nr

nr

nr

nr

nr

nr

nr

nr

nr

nr

SMA

nr

nr

nr

nr

nr

nr

nr

nr

nr

nr

TNC

nr

nr

nr

nr

3 – 30 V DC

25 mA

-40 to +60c

na

Y / IP68

DC ground

N preferred but all available

As applicable

Magnetic / Pole / Screw

nr

nr

5 – 30 V DC

80 mA

-40 to +60c

na

Y / IP68

DC ground

N preferred but all available

As applicable

as above

nr

nr

5 – 30 V DC

80 mA

-40 to +60c

na

Y / IP68

DC ground

N preferred but all available

As applicable

Pole / Screw

nr

nr

www.gpsworld.com

February 2013 | GPS World

55

antenna survey 2013 | Sponsored by Manufacturer

Model

Sarantel

SL1251 / SL1252 (GeoHelix)

www.sarantel.com

Intro. Date 2012

UserEnvir. 1 ADLNPVSM

Size: Length x Width x Height 23.2x10x10mm

Weight 7g

Frequency / Bandwidth 2 1575.42 MHz ± 2

VSWR 3 2.0:1 typ

Axial Ratio (dB)