JTI Chip Antenna Mounting and Tuning Techniques

LTCC Chip Antennas –How to maximize performance

 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)
Layout Tips
Layout Tips 1
Layout Tips - 1
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 - 2
Layout Tips 3

Further examples of good antenna placement schemes

Layout Tips - 3
Layout Tips 4
Layout Tips - 4
B. Measuring Steps
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)
Probe and Feed Line Smith chart display from 1-4GHz (not-normalized)
1.Probe+Feed Line Smith chart display from 1-4GHz
(not-normalized)
Probe and Feed Line (normalized)
2.Probe+Feed Line (normalized)
Probe and Feed Line Antenna Smith chart display from 1-4GHz (not-normalized)
1.Probe + Feed Line + Antenna Smith chart display from 1-4GHz (not-normalized)
Probe and Feed Line and Antenna(normalized)
2.Probe + Feed Line + Antenna
(normalized)
Antenna and shunt 3.9nH (normalized)
Step 1 in matching: Ant + shunt 3.9nH
(normalized)
Antenna and shunt 3.9nH series 1.5pF (normalized)
Step 2 in matching: Ant + shunt 3.9nH + series 1.5pF (normalized)
Matched Antenna Example
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.
2450AT45A100-EB1SMA Test Board
EVB p/n: 2450AT45A100-EB1SMA
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