Lab-05: Loop Antenna

I. Theory

1. Loop Antenna 기초

ㅇ 다이폴과 함께 가장 기본적인 안테나 중의 하나

ㅇ 3kHz-30GHz 주파수 범위에서 다양한 용도로 사용

ㅇ 루프 안테나 용도: 통신, NFC, RFID, 자기장 센서, 전파방향 탐지, 무선충전(자기장 생성 코일로 사용)

ㅇ 평면에 설치 용이

ㅇ 다이폴 안테나와 루프 안테나 비교

ㅇ 루프 안테나 전류분포 분석

2. A Small Loop Antenna

-

- Current: constant along the loop

I = I₀

- Farfield

- Radiation resistance

- Directivity:

- Multi-turn: N = number of turns

Electric and magnetic fields: N times

Radiation resistance: N² times

- Equivalent circuit with a tuning capacitor

R_r : radiation resistance

R_l : conductor loss resistance

L_A : loop external inductance

L_i : loop internal inductance, due to H inside the conductor

Thin wire (b<<a)

Thick wire: formulas by R. Dengler, Advanced Electromagnetics, 5(1), Jan. 2016

: quality factor

3. Large Loop Antennas

Radiation pattern

Input impedance

Large impedance (anti-resonance) when

Resonance at C = 1.0, 1.5, 2.0, 2.5

5. Loop Antenn 사례

ㅇ 무선충전

- Link Dream Qi wireless charger transmitter and coil (left) and receiver coils by Wurth Electronics (right)

ㅇ NFC, 13.56MHz

- Smartphon NFC loop antenna

- Credit card NFC loop antenna

ㅇ AM 방송수신 안테나

- AM receiving rerrite loop antenna (From Circuit Exchange International)

ㅇ HF amaeur radio

- HF loop antenna for amateur radio (qrznow.com, Joel Hallas, W1ZR)

ㅇ 방향탐지 안테나

- Cytony DF-A0097A crossed loop/monopole Watson Watt DF antenna, 2-m loop, VLF/LF/MF

ㅇ FM 라디오 방송 수신 안테나, 88-108MHz

- FM radio receiving loop antenna (Tesslor-USA)

ㅇ 군용 통신 및 방향탐지

- HF vehicle loop antenna for NVIS communication (Harris Corp.)

- HF loop DF array at Penhale Sands Tx Station, Cornwall, UK

5. Loop antenna impedance matching

ㅇSmall loop antenna impedance matching

ㅇNFC tag impedance matching