Outline

Chip Antenna Characteristics
Antenna Selection Considerations
Circuit Design Constraints
Layout Tips

Motivation

Chip Antenna an efficient means of “connectivity” to modern portable compact electronic devices.
Miniature portable devices requires small antennas.
Can be internalized – i.e. “Concealed” within device.

Pros & Cons

Pros
Chip antennas are small, cheap and performs well.
Bulky external “whip” type antennas are thing of the past.
Cons
Must be accounted for during initial circuit design stage.
Interference, proximity de-tuning & degradation concerns.

Ultimate Goal → To Maximize Performance

LTCC Chip Antennas
Chip Antenna Characteristics - 1
  • Features Ag radiating element encapsulated in ceramic.
  • A quarter-wave ( λ/4 ) monopole system.
  • Works with GND plane to form dipole system.
  • Certain “No-GND” metal-free space necessary.
  • Small form factor, thin profile & light weight
Chip Antenna Characteristics - 2
  • Omni-directional radiation.
  • Linear Polarization.
  • Mounting configuration flexibility.
  • Frequency range supported: 0.08 GHz thru 10 GHz.
  • WiFi, BT, WiMAX, UWB, GSM, CDMA, GPS etc.
  • Suitable for Pick & Place.
Antenna Selection Considerations - 1
  • Size
  • Frequency Band
  • Bandwidth
  • Polarization
  • Peak Gain
  • Average Gain
  • Radiation Pattern requirements
Antenna Selection Considerations - 2
  • Successful Antenna design means harmonious interaction of the “seven” parameters (next page).
  • Additional considerations for diversity systems – e.g. MIMO
  • Overall performance is always system dependent.
Circuit Design Constraints
  • Size of the Circuit board.
  • Layout of other board components.
  • Complexity of circuit.
  • Proper GND/No-GND dimensions and clearances.
  • “Tuning” Matching Circuitry
  • Shielding
  • Suitable Enclosure (material)
LTCC Chip Antennas
Layout Tips

Layout Tips -1

Layout Tips 1

Layout Tips -2

Layout Tips 2
  • Don’t put any metal objects or batteries (if applicable) above or below the yellow region
  • •Keep away any other metals from clearance area

Layout Tips -3

Layout Tips 3
  • Further examples of good antenna placement schemes

Layout Tips -4

Layout Tips 4
B. Measuring Steps

Test Board matching example
Antenna Matching

A. Antenna Matching Setup

  1. One-port (S11) calibration for N.A. (Network Analyzer) Open-Short-Load for desired operating bandwidth
  2. Mount probe (semi-rigid RF cable for our example) onto PCB and connect to N.A.
  3. Measure S11 of test board without antenna or any matching components and save as: →S11_open →save trace to memory of N.A.
  4. Measure S11 of test board with antenna and series 0Ω resistor mounted and save as: →S11_antenna
  5. Set N.A. to data/memory mode (S11_antenna/S11_open) and display/save as: →S11_match
  6. Match the trace of S11_match to 50Ω (center of Smith chart at the desired frequency)

1.Probe+Feed Line Smith chart display from 1-4GHz
(not-normalized)
Probe and Feed Line Smith chart display from 1-4GHz (not-normalized)

2.Probe+Feed Line (normalized)

Probe and Feed Line (normalized)

1.Probe + Feed Line + Antenna Smith chart display from 1-4GHz (not-normalized)
Probe and Feed Line Antenna Smith chart display from 1-4GHz (not-normalized)

2.Probe + Feed Line + Antenna
(normalized)
Probe and Feed Line and Antenna(normalized)

Step 1 in matching: Ant + shunt 3.9nH
(normalized)
Antenna and shunt 3.9nH (normalized)

Step 2 in matching: Ant + shunt 3.9nH + series 1.5pF (normalized)
Antenna and shunt 3.9nH series 1.5pF (normalized)

Matched Antenna Example

General Specifications

Part Number2450AT45A100
Frequency Range2400 - 2500 Mhz
Peak Gain3.0 dBi typ. (XZ-V)
Average Gain1.0 dBi typ. (XZ-V)
Return Loss9.5 dB min.

EVB p/n: 2450AT45A100-EB1SMA
2450AT45A100-EB1SMA Test Board

Probe + Feed Line + Antenna Smith chart display from 1-4GHz (not-normalized)
b) With Matching Circuit* (wide bandwidth)
* matching circuit and component values will depend on PCB layout, thickness, material, etc.

JTI P/N for Matching Circuit:
Cap (1.5pF): 500R07S1R5BV4T
Inductor (3.9nH): L-07C3N9SV6T