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
- 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
- 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.
- Size
- Frequency Band
- Bandwidth
- Polarization
- Peak Gain
- Average Gain
- Radiation Pattern requirements
- 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.
- 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)
The ceramic chip antenna and top RF ground must be on the same plane. Substituting the top layer for an inner layer as a ground plane requirement will not work
![Layout Tips 1](/images/tuning/layout-tip-1.png)
![Layout Tips 2](/images/tuning/layout-tip-2.png)
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](/images/tuning/layout-tip-3.png)
Further examples of good antenna placement schemes
![Layout Tips 4](/images/tuning/layout-tip-4.png)
![Antenna Matching](/images/tuning/antenna-matching-5.png)
- 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 and Feed Line Smith chart display from 1-4GHz (not-normalized)](/images/tuning/probe-feed-line-1.png)
(not-normalized)
![Probe and Feed Line (normalized)](/images/tuning/probe-feed-line-2.png)
![Probe and Feed Line Antenna Smith chart display from 1-4GHz (not-normalized)](/images/tuning/probe-feed-line-3.png)
![Probe and Feed Line and Antenna(normalized)](/images/tuning/probe-feed-line-4.png)
(normalized)
![Antenna and shunt 3.9nH (normalized)](/images/tuning/probe-feed-line-5.png)
(normalized)
![Antenna and shunt 3.9nH series 1.5pF (normalized)](/images/tuning/probe-feed-line-6.png)
Part Number | 2450AT45A100 |
---|---|
Frequency Range | 2400 - 2500 Mhz |
Peak Gain | 3.0 dBi typ. (XZ-V) |
Average Gain | 1.0 dBi typ. (XZ-V) |
Return Loss | 9.5 dB min. |
![2450AT45A100-EB1SMA Test Board](/images/tuning/2450AT45A100-EB1SMA.png)
![Probe + Feed Line + Antenna Smith chart display from 1-4GHz (not-normalized)](/images/tuning/2450AT45A100-EB1SMA-b.png)
* 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