Technical Manual For Chips Multilayer Antenna Matching Adjustment Method LDA31 series

Transcription

1 Technical Manual For Chips Multilayer Antenna Matching Adjustment Method LDA31 series Application: 2.4GHz Wireless Bluetooth TM 1/17

2 Chip Antenna is a special component to change characteristics and this requires a different matching circuit by the condition of your usage(i.e. size of PCB / position of antenna / feeding position ) and it is difficult to offer standard product to you. So, we prepare the below 3 different kind of standard chip antennas which have different frequency and these will cover conditions of various customer s usage and application of 2.4GHz. Please evaluate and find the best chip antenna out of these chip antenna. This application manual was prepared to offer a hint of chip antenna s usage and technical information and this will be helpful for you to design your PCB and matching circuit. Center Frequency[MHz] Part Number 2730 LDA312G7313F LDA313G0313F LDA313G3313F-243 2/17

3 1. Standard f0 of LDA31 for 2.45GHz-Band 1-1. Measurement System Chip antenna f0 is measured by using a PCB as shown below and a network analyzer. Ferrite sheet is spreaded under the PCB to intercept from outside influence. Network Analyzer Cable Ferrite Sheet Antenna Measurement System for Chip Antenna 3/17

4 1-2. Standard f0 of LDA31 Construction, Dimensions & Marking Land Pattern max (mm) Center Frequency [MHz] Part Number 2730 LDA312G7313F LDA313G0313F LDA313G3313F-243 Standard f0 of LDA31 for 2.45GHz-Band 4/17

5 2.Suitable PCB Condition of LDA Chip Antenna Position Chip antenna is sticked out. LDA31 No Chip antenna is located on the no area. Chip antenna is located on the plane. No No No No Excellent Good Acceptable Not recommended 2-2.Antenna Direction & Feed Point Position Open terminal of chip antenna is pointed to outside of PCB, and feed point is located at the edge of PCB. Open terminal of chip antenna is pointed to outside of PCB, however feed point is located at the inside of PCB. Feed point is located at the edge of PCB, however open terminal of chip antenna is pointed to plane of PCB. Feed Point No No No No No No Good Acceptable Not recommended 5/17

6 2-3.Matching Circuit Position Matching Circuit is located at the top of 50ohm line that is nearest place from chip antenna. Matching Circuit LDA31 Matching Circuit is located at the top of 50ohm line that is farthest place from chip antenna. 50ohm LDA31 50ohm Matching Circuit OUTPUT RF Module OUTPUT RF Module Good Acceptable 2-4.Structure of Matching Circuit (Shunt-Series-Shunt) (Series-Shunt-Series) (Series-Shunt) Matching Circuit Matching Circuit Matching Circuit Good Good Acceptable (*Note: When series components are not needed, 0-ohm resistance is needed to mount there.) 6/17

7 2-5.Actual Mock-up PCB (1) Cellular Phone Size 40 (The Expansion of A area) 6.1 A Matching No Board Thickness: 0.8 Board Material: FR-4 Feed Point (unit : mm) Semi-rigid cable should be soldered to place and be extended away from the center of the PCB. And typically, ferrite beads are affixed to the part of the cable that extends away from PCB. 7/17

8 (1) Ideal Size for 2.45GHz-Band (The Expansion of A area) A Matching No Board Thickness: 0.8 Board Material: FR-4 Feed Point (unit : mm) Semi-rigid cable should be soldered to place and be extended away from the center of the PCB. And typically, ferrite beads are affixed to the part of the cable that extends away from PCB. 8/17

9 3.Impedance Matching and Frequency Adjustment 3-1. Preparation of Impedance Matching (Step 1) The Beginning Network analyzer is usually calibrated at the top of cable. So the smith chart can t show correct impedance of the chip antenna because of including semi-rigid cable impedance, etc Antenna OPEN Terminal (*A series component isn t mounted.) Z 0 = R 0 + jx 0 Feed Line 1 (Semi-rigid Cable, Strip Line, etc.) Feed Line 2 (Network Analyzer Cable) (Step 2) Electrical Delay Adjustment Electrical delay should be set on the network analyzer using open terminal as shown below. Antenna Z 1 = R 1 + jx 1 = OPEN OPEN Terminal (*A series component isn t mounted.) Feed Line 1 (Semi-rigid Cable, Strip Line, etc.) Feed Line 2 (Network Analyzer Cable) OPEN 9/17

10 (Step 3) Correct Impedance of Chip Antenna After electrical delay adjustment, the antenna system can be tested exactly on a calibrated network analyzer as shown below. Antenna Z 2 = R 2 + jx 2 THROUGH CONDITION (*0-ohm is mounted as series component.) Feed Line 1 (Semi-rigid Cable, Strip Line, etc.) Feed Line 2 (Network Analyzer Cable) 3-2. Smith Chart The smith chart view can be used to match the antenna impedance to 50ohm. Using series and shunt components, the point of 2.45GHz should be moved to the point of Z=50ohm. Z=50ohm Z=50ohm Value Shift Series C Small Large Large Small Small Small Large Large Value Shift Shunt C Small Small Large Large Small Large Large Small 10/17

11 3-3. Adjustment of Impedance (Ex1). The mock-up PCB of Cellular Phone size shown in page 7 is used. Initial impedance is lower than 50ohm. Mostly the chip antenna impedance shows low impedance than 50 ohm like this. 1. The Beginning 2.with =6.8nH =6.8nH Low Impedance 3.with 4. with =3.3nH f0=2370mhz =3.3 nh Good Matching! High impedance 11/17

12 (Ex2). The mock-up PCB of ideal size shown in page 8 is used. Initial impedance is higher than 50ohm. This is a rare case. 1.The Beginning 2.with =1.6nH =1.6nH High impedance 3.with =2.2nH 4. with =3.9nH =2.2nH =3.9nH Good Matching! Low Impedance 12/17

13 3-4. Adjustment of Resonance Frequency (Ex1). The mock-up PCB of Cellular Phone size shown in page 7 is used. Fistly chip antenna f0 is changed as rough adjustment. Then there is some possibility that the impedance is change a little, so it should be rematched again. 1.The Beginning() 2. f0=3030mhz (LDA313G2713F-237) f0=3030mhz (LDA313G0313F-240) f0=2425mhz f0=2677mhz 13/17

14 Nextly by inserting series component resonance frequency can be shifted widely and be adjusted more exactly (fine adjustment). Typical data is shown below. 3.The Beginning() 4., Series C=15pF f0=2425mhz f0=2434mhz Series C =15pF 5., Series C=7.5pF 6., Series C=4pF f0=2446mhz Series C =7.5pF f0=2462mhz Series C =4pF 14/17

15 7., =1.5nH 8., =2.2nH f0=2408mhz =1.5nH f0=2383mhz =2.2nH 15/17

16 (Ex2) The mock-up PCB of ideal size shown in page 8 is used. Fistly chip antenna f0 is changed as rough adjustment. Then there is some possibility that the impedance is change a little, so it should be rematched again. 1The Beginning() f0=2560mhz =2.2nH 16/17

17 Nextly by inserting series component resonance frequency can be shifted widely and adjusted more exactly(fine adjustment). Typical data is shown below. 2.The Beginning() 3., =22nH =22nH f0=2560mhz =2.2nH f0=2549mhz =2.2nH 4., =15nH 5., =12nH f0=2542mhz =15nH =2.2nH f0=2530mhz =12nH =2.2nH 17/17