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JTI Chip Antenna Mounting and Tuning Techniques |
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Outline
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- Chip Antenna Characteristics
- Antenna Selection Considerations
- Circuit Design Constraints
- Layout Tips
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Ultimate Goal → To Maximize Performance
Motivation
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- 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.
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Pros
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- Chip antennas are small, cheap and performs well.
- Bulky external “whip” type antennas are thing of the past.
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Cons
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- Must be accounted for during initial circuit design stage
- Interference, proximity de-tuning & degradation concerns.
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LTCC Chip Antennas
Chip Antenna Characteristics - 1
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- 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
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Chip Antenna Characteristics - 2
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- 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.
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Antenna Selection Considerations - 1
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- Size
- Frequency Band
- Bandwidth
- Polarization
- Peak Gain
- Average Gain
- Radiation Pattern requirements
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Antenna Selection Considerations - 2
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- 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.
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Circuit Design Constraints
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- 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)
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Circuit Design Constraints
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- 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)
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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
- Further examples of good antenna placement schemes
Layout Tips - 4
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- Antenna placement schemes for antenna diversity systems
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Antenna Matching -5
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A. Antenna Matching Setup
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Test Board matching example |
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B. Measuring Steps
- One-port (S11) calibration for N.A. (Network Analyzer) Open-Short-Load for desired operating bandwidth
- Mount probe (semi-rigid RF cable for our example) onto PCB and connect to N.A.
- Measure S11 of test board without antenna or any matching components and save as: →S11_open →save trace to memory of N.A.
- Measure S11 of test board with antenna and series 0Ω resistor mounted and save as: →S11_antenna
- Set N.A. to data/memory mode (S11_antenna/S11_open) and display/save as: →S11_match
- Match the trace of S11_match to 50Ω (center of Smith chart at the desired frequency)
- Probe+Feed Line Smith chart display from 1-4GHz
(not-normalized)
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- Probe+Feed Line
(normalized)
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Test Board matching example |
- Probe + Feed Line + Antenna Smith chart display from 1-4GHz
(not-normalized)
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- Probe + Feed Line + Antenna
(normalized)
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Test Board matching example |
Step 1 in matching:
Ant + shunt 3.9nH (normalized) |
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Test Board matching example |
Step 2 in matching:
Ant + shunt 3.9nH + series 1.5pF (normalized) |
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Test Board matching example |
Matched Antenna Example
Conclusion – How to design
- 1st – Determine the antenna location and space available on board
- 2nd – Select the most appropriate antenna model
- 3rd - Implement antenna in conformance with design rules
- 4th – Match antenna to your system
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Technical Notes 
