GPS Patch Antenna Considerations - MRC Components … Doc.pdf · AMOTECH2 Contents n Antenna...

GPS Patch Antenna Considerations

Advanced Material On TECHnology

AMOTECH 2

Contents

n Antenna Elementn Impedance and Resonant Frequencyn Axial Ration Voltage Standing Wave Ratio (VSWR)n Bandwidthn Result of Measurement

AMOTECH 3

Antenna Element

n The antenna’s size and shape n compact size using ceramic materialn RHCP(Right Hand Circular Polarization) patch

Offset fedrectangular patch

Slotted squarepatch

Truncated cornersquare patch

AMOTECH 4

Antenna Element

n AMOTECH - GPS Patch Antenna25

2.6

25 4

0.5 3

¥Õ0.8

¥Õ3.0

n compact size : 25mm × 25mm × 4mmn excellent temperature stabilityn (silver plated) truncated corner square patch

AMOTECH 5

Impedance and Resonant Frequency

n An antenna’s impedance depends on many factors :n how it is constructed,n how it is fed,n and to some degree, the surrounding environment

n A microstrip patch antenna placed in a plastic enclosure (radome), for example, can have its resonant frequency shifted downward by several MHz, depending onn the thickness of the radomen its dielectric constantn and the distance between the antenna face and inner radome.

AMOTECH 6

Impedance and Resonant Frequency

n Radome effect on resonant frequency

RadomeAMOTECH

GPS Patch Antenna

Double SidedAdhesive Tape

PCB

Sheild Can

Infinite Ground

SMA TypeConnector

Infinite Ground

70by70 Ground

n Final Assembly

n Assembly without radome

n Patch on 70 by 70 ground 1540 1550 1560 1570 1580 1590 1600 1610 1620 1630

-30

-25

-20

-15

-10

-5

0

radomedifferent environment

Frequency shift caused by

Frequency [MHz]

Ret

urn

Loss

[dB

] Final Assembly Assembly without Radome Patch on 70 by 70 GND

The final assembly obtains optimized operation over 1575.42MHz ± 3MHz

AMOTECH 7

Axial Ratio

n General descriptionn To be maximally sensitive to GPS signals, the ideal GPS

antenna should be perfectly RHCPn The more elliptically polarized it is, the lower its RHCP

sensitivityn The degree of ellipticity is given by the antenna’s axial ration Good GPS antennas have an axial ratio in the zenith direction

of 3dB or better.n A measurement of the VSWR alone does not guarantee the

antenna’s axial ratio performance.

AMOTECH 8

Axial Ratio

n Measure the Axial Ration The GPS Patch antenna

transmits at the desired frequency.

n Rotates the linear polarization probe

n AR = A - B , in dB

Polarizationellipse

AB ¥è

n Measuring system in AMOTECH

rotate testprobe

7.26 m

3 m

SignalGenerator

SpectrumAnalyzer PC

<Anechoic Chamber>

AMOTECH 9

Voltage Standing Wave Ratio

n An important consideration is the antenna-receiver connection. This is achieved with a transmission line, usually a coaxial cable.

n To maximize signal transfer from the antenna to the receiver, wemust minimize power loss.

n Power may be lost if the coupling between the antenna and the cable is imperfect and also within the cable itself.

n To prevent power loss at the interface between the cable and theantenna, the impedance of the cable and the antenna must be the same.

n The formula for relating mismatch loss to VSWR is:2VSWR-1Mismatch_Loss(dB)=10log 1-

VSWR+1

AMOTECH 10

Bandwidth

n Operating bandwidth is defined as frequency range satisfied following:n VSWR (< 2.0) or Return loss (< 10 dB)n Axial ratio (< 3.0 dB)

n GPS patch antenna designed by AMOTECH satisfies all criteria over the operating frequency range of 1575.42 MHz ± 3 MHz.

AMOTECH 11

Result of Measurement

Geometry of final assembly Axial Ratio

n GPS Antenna installed on Infinite Ground

RadomeAMOTECH

GPS Patch Antenna

Double SidedAdhesive Tape

PCB

Sheild Can

Infinite Ground

SMA TypeConnector

1565 1570 1575 1580 15850

2

4

6

8

10

12

Frequency [MHz]

Axia

lratio

[dB]

AMOTECH 12


Return Loss Smith chart

n GPS Antenna installed on Infinite Ground

CH1 S22 LOG 5 dB/ REF 0 dB

CENTER 1 . 575 000 000 GHz SPAN . 200 000 000 GHz

Cor Avg10

Hld

PRm

MARKER 1 1.57542 GHz

17 May 2000 13:18:10

1

2

3 4

1 : -29 . 366 dB 1 . 575 420 000 GHz

CH1 Markers

BW : . 019597108 GHz

cent : 1 . 576044505 GHz

Q : 80 . 422

1_ loss : -29 . 366 dB

CH1 S22 1 U FS


Cor Avg10

Hld

PRm


17 May 2000 13:18:39

1

2 3

4

1 : 53 . 414 -824 . 22 m 122 . 57 pF 1 . 575 420 000 GHz

CH1 Markers

2 : 54 . 098-304 . 69 m

1 . 57604 GHz

3 : 95 . 941-4 . 6016

1 . 56624 GHz

4 : 40 . 080-28 . 146

1 . 58584 GHz

AMOTECH 13



n GPS Antenna installed on 70mm×70mm Ground



Cor Avg11

Hld

PRm


17 May 2000 13:20:18

1

2

3 4

1 : -32 . 796 dB 1 . 576 040 000 GHz

CH1 Markers

BW : . 025996459 GHz

cent : 1 . 575217893 GHz

Q : 60 . 594

1_ loss : -32 . 796 dB

CH1 S22 1 U FS


Cor Avg11

Hld

PRm


17 May 2000 13:20:33

1

2

3

4

1 : 52 . 219 -748 . 05 m 135 . 00 pF 1 . 576 040 000 GHz

CH1 Markers

2 : 52 . 7400 . 3691

1 . 57521 GHz

3 : 77 . 30131 . 188

1 . 56221 GHz

4 : 28 . 793-13 . 788

1 . 58821 GHz

AMOTECH 14



n GPS Antenna installed on 50mm×50mm Ground



Cor Avg16

Hld

PRm


17 May 2000 13:24:44

1

2

3 4

1 : -23 . 136 dB 1 . 571 160 000 GHz

CH1 Markers

BW : . 021365209 GHz

cent : 1 . 570216250 GHz

Q : 73 . 494

1_ loss : -23 . 136 dB

CH1 S22 1 U FS


Cor Avg16

Hld

PRm


17 May 2000 13:25:01

1

2

3

4

1 : 50 . 771 -6 . 9941 14 . 483 pF 1 . 571 160 000 GHz

CH1 Markers

2 : 51 . 322-6 . 7988

1 . 57021 GHz

3 : 96 . 0623 . 5078

1 . 55953 GHz

4 : 33 . 186-21 . 324

1 . 58089 GHz

AMOTECH 15



n GPS Antenna without Ground



Cor

PRm


17 May 2000 13:27:44

1

2

3 4

1 : -13 . 217 dB 1 . 570 040 000 GHz

CH1 Markers

BW : . 009909594 GHz

cent : 1 . 569743510 GHz

Q : 158 . 41

1_ loss : -13 . 217 dB

CH1 S22 1 U FS


Cor

PRm


17 May 2000 13:27:57

1

2

3

4

1 : 37 . 344 14 . 777 1 . 4980 nH 1 . 570 040 000 GHz

CH1 Markers

2 : 35 . 21711 . 643

1 . 56961 GHz

3 : 38 . 666-26 . 533

1 . 56465 GHz

4 : 96 . 6871 . 4766

1 . 57457 GHz

AMOTECH 16


Geometry of assembly without radome Axial Ratio

n GPS Antenna without Radome on Infinite Ground

Infinite Ground

1570 1575 1580 1585 1590 15950

2

4

6

8

10

12

Frequency [MHz]

Axia

lratio

[dB]

AMOTECH 17



n GPS Antenna without Radome on Infinite Ground



Cor Avg10

Hld

PRm

MARKER 1 1.5815 GHz

17 May 2000 14:18:22

12

3 4

1 : -24 . 581 dB 1 . 581 500 000 GHz

CH1 Markers

BW : . 021975607 GHz

cent : 1 . 583006891 GHz

Q : 72 . 035

1_ loss : -24 . 581 dB

CH1 S22 1 U FS


Cor Avg10

Hld

PRm

MARKER 1 1.5815 GHz

17 May 2000 14:18:50

1

23

4

1 : 52 . 887 5 . 3477 538 . 16 pH 1 . 581 500 000 GHz

CH1 Markers

2 : 55 . 6316 . 2891

1 . 58300 GHz

3 : 95 . 9304 . 7422

1 . 57201 GHz

4 : 35 . 635-24 . 199

1 . 59399 GHz

AMOTECH 18


Return Loss Smith Chart

n GPS Antenna without double sided adhesive tape



Cor Avg11

Hld

PRm


17 May 2000 14:22:33

1

2

3 4

1 : -24 . 604 dB 1 . 577 260 000 GHz

CH1 Markers

BW : . 020971366 GHz

cent : 1 . 578946411 GHz

Q : 75 . 291

1_ loss : -24 . 604 dB

CH1 S22 1 U FS


Cor Avg11

Hld

PRm


17 May 2000 14:22:55

1

2 3

4

1 : 54 . 336 4 . 3496 438 . 90 pH 1 . 577 260 000 GHz

CH1 Markers

2 : 56 . 3795 . 1270

1 . 57894 GHz

3 : 95 . 0639 . 0820

1 . 56846 GHz

4 : 34 . 949-23 . 455

1 . 58943 GHz

AMOTECH 19


Geometry of patch antenna Axial Ratio

n GPS Patch Antenna on 70 by 70 AMOTECH Test Jig

70by70 Ground

1585 1590 1595 1600 1605 1610 16150

2

4

6

8

10

12

Frequency [MHz]

Axia

lratio

[dB]

AMOTECH 20


Return Loss Smith Chart

n GPS Patch Antenna on 70 by 70 AMOTECH Test Jig



Cor Avg16

Hld

PRm


17 May 2000 13:31:03

1

2

3 4

1 : -24 . 491 dB 1 . 601 860 000 GHz

CH1 Markers

BW : . 023749519 GHz

cent : 1 . 602020404 GHz

Q : 67 . 455

1_ loss : -24 . 491 dB

CH1 S22 1 U FS


Cor Avg16

Hld

PRm


17 May 2000 13:31:28

1

2

3

4

1 : 55 . 262 -3 . 4277 28 . 986 pF 1 . 601 860 000 GHz

CH1 Markers

2 : 55 . 158-3 . 5430

1 . 60202 GHz

3 : 86 . 25424 . 543

1 . 59014 GHz

4 : 32 . 359-20 . 197

1 . 61389 GHz

GPS Patch Antenna Considerations - MRC Components … Doc.pdf · AMOTECH2 Contents n Antenna...

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