Miniature Antenna:Results and Proposed Work

March 2008

Outline

• 916 MHz antenna prototypes and results

• 2.2 GHz, 2.4 GHz antenna prototypes and results

• 433 MHz antenna prototypes and results

• Proposed New Research

916 MHz antenna, prototype and test results

The volume of the antenna with its ground plane is 0.024 λ 0.06 λ 0.076 λ, where λ = 372.5 mm for 916 MHz antennas.

Simulation and Measurement of S11

916 MHz antenna, Gain measurements

Half wave dipoles

916 MHz FICA

916 MHz FICAHalf wave dipoles

S11 of 2.2 GHz & 2.45 GHz FICA

2.2 GHz FICABandwidth = 14 MHz

2.45 GHz FICABandwidth = 3 MHz

2.2GHz FICA: 98% available power transmitted

2.45GHz FICA: 92% available power transmitted

Total volume including ground plane: 0.09 λ x 0.09 λ x 0.025 λλ = 136.36 mm@2.2 GHzλ = 122.44 mm@2.45 GHz

2.2 GHz FICA Gain Test (II)

-50 0 50 100 150 200 250 300 350 400-30

-25

-20

-15

-10

-5

Phi

Nor

mal

ized

Gai

n (d

B),

The

ta =

90

degr

ee

Calibrate using ½ wave dipole

Difference between FICA and ½ dipole is -7dB; Polarization demonstrates functionality

0Half wave dipole

68 mm

0.09 λ x 0.09 λ x 0.025 λ12 mm x 12 mm x 3.5 mm

433 MHz Dielectric Loaded Miniature Antenna Results

77.2

mm

25.4mm

At 433 MHz,λ=693mm.This antennacan work witha PCB board of0.11λ x 0.037λ

Initial test:-5dB Bandwidthis 8 MHz

Further design needed for 10MHz bandwidth

BW=8MHz

Commercial Chip Antennas (Antenna Factors, Co.) need a ground plane to function properly

λ/2.98

λ/3.64 λ/4.68

λ/8

λ/8

λ/9

λ/9

1

2

3

4 5λ/8.84

λ/8.84

λ/8.84

SMA fed through a holeλ= 32.75 cm ( 916 MHz )

Antenna 1~4, commercial chip antenna.Antenna 5: Our FICA antenna

FICA Outperforms Commercial

1. Antenna 1-4 are commercial antennas. Antenna 5 is our FICA.2. Antenna 1 is the exact design given by spec sheet,3. Antennas 1-3: The feeding cable is along the same direction as the feeding

line, which helps antenna radiation, effectively increasing antenna size.4. To eliminate this effect, feeding line is perpendicular to the ground plane.

This was done for Antenna 4, notice enormous performance drop. 5. Our FICA (Antenna 5) has substantially better performance than commercial

antennas, especially with when feed is not part of the system (4) where the improvement is by more than 23dB (200 times).

Resonance

frequency

-10dB bandwidth Received Power

Antenna 1 916 MHz 25 MHz -42 dBm

Antenna 2 911 MHz 14 MHz -39 dBm

Antenna 3 893 MHz NA -39 dBm (not sure)

Antenna 4 831 MHz 9 MHz -55 dBm

Antenna 5 952 MHz 11 MHz -32 dBm

Proposed Research for Ultra-Small Antennas

Task I: Design of Helical (FICA) Style Ultra-Small Antenna for Requested Specifications (400MHz resonance, 10MHz BW)

• Ultimate optimization goal:– Maximum achievable bandwidth (10 MHz or more

Bandwidth at 400 MHz with10 dB return loss )– minimum antenna volume (2 parts)

• Part1: the component which we called “antenna”, • Part2: the “virtual or image antenna”-----ground plane (ground plane will be smaller than the current prototype

at 400 MHz)– highest gain (-1 to -2 dBi)– highest achievable efficiency (40%<efficiency<60%)

Proposed Research for Ultra-Small Antennas:Realize Design Goals

These design goals will be realized with a synergistic approach using experiment and theory:

•We will fabricate and test designs•We will use finite element (HFSS) simulation to help guide experimental program.

•We will optimize the following parameters for FICA:•Determine helix shapes for wire antenna families (i.e. FICA): pitch, leaning angle, cross-section area of coils, helix length, tapping point.•Determine geometry of ground plane: ground plane size, feeding positions and FICA position on the ground plane.•Optimize dielectric block: Use dielectric to increase capacitance to ground, not the intercoil capacitance of FICA to minimize the coil length

Proposed Research for Ultra-Small Antennas

We also propose to develop circuit models of FICA for antenna-RF circuit co-design, which will maximize performance on system level.

For example, for a FICA at 916 MHz (Fig a), we developed an equivaleng circuit to represent the antenna’s impedance matching, radiation resistance, and resonance. The circuit may look like the one in Fig. b. With the help of circuit b, we could optimize system gain, and sensitivity for transceivers.

a b

Proposed Research for Ultra-Small Antennas

• Testing plan:– Will have access to a world

class anechoic camber at the FDA White Oaks Facility

– Antenna measurements at the FDA will be very accurate and help evaluate with precision the gain performance of the various designs.

– We will regularly compare our antenna prototypes with commercially available antennas.

– Comparisons will require building test platforms for commercial antennas, as well as our own.

Anechoic Chamber

ReceiverTransmitter

FICA antennaOn rotating table

Half wave dipoleOn fixed pole

Anechoic Chamber

ReceiverTransmitter

FICA antennaOn rotating table

Half wave dipoleOn fixed pole