An Automatic Antenna Tuning System Using Only RF Signal Amplitudes

Abstract

Abstract-The operating environment of mobile phones fluctuates continuously, due to changing handling conditions and nearby objects. The resulting fluctuations in antenna impedance cause both a decrease in link quality and a higher standing wave ratio, that requires more robust and hence less efficient PA implementations. In this paper an automatic antenna tuner system for handheld applications is presented that uses two series reactances combined with 3 simple RF-peak detectors to sense both reactive and real impedance mismatches. The control loop only requires low-frequency electronics which makes it low cost, low power and relatively easy to integrate. Measurements on a demonstrator system show correct behaviour for VSWR up to 10.Index Terms-Impedance matching, antenna tuning, high efficiency power amplifiers, wireless communication systems.

A Design of Adaptive Impedance Tuning Circuit for UHF-Band Using λ/4 Transmission Line and π-Network

“…임의의 부하단 임피던스를 측정하기 위한 부정합 측정부는 방향성 결합기 [5]～ [7] 를 이용하여 신호의 크 기만을 측정하는 방법과, RF 검파기(detector) [1], [8]～ [10] 나 로그 증폭기(logarithmic amplifier) [11] [7] . [15] , 이러한 방법으로 넓은 임피던스 가변 대역을 만족시키기 위해서는 많은 갯 수로 이루어진 PIN 다이오드 열(bank)과 각각의 PIN 다이오드의 on/off를 수행하여야 하므로 적응형 임피 던스 정합 회로의 조정 알고리즘이 복잡해지는 단점 이 발생하게 된다.…”

An Efficient Adaptive Antenna-Impedance Tuning Unit Designed for Wireless Pacemaker Telemetry

“…To address the problem due to impedance mismatch, many antenna impedance tuning units operating iteratively and/or using directional coupler to evaluate the quality of the link were investigated [7][8][9][10][11][12][13][14][15]. Since the use of a bulky additional coupler into the device is totally inacceptable and since iterative matching process spends time and consumes power to set the proper state of the network, we investigate on a novel coupler less method [25] solving the problems related to the impedance mismatch in a single iteration.…”

“…The pacemaker radio communication module, designed to exchange data with an external base station, features new technologies including, but not limited, new architecture, low power design technique, acoustic wave filter co-integration, miniaturized antenna design, etc. The miniaturized antenna embedded on the pacemaker device is typically a narrow bandwidth high-Q antenna [3] easily detuned by unpredictable near field environmental factors [4][5][6]. The input impedance of the implanted antenna can vary due to the tissue (muscle, fat, skin, etc.)…”

“…Most of existing antenna-impedance tuning units [7][8][9][10][11][12][13][14][15] operates iteratively to successfully adapt source and load impedances. However, iterative methods generally spend several hundred milliseconds to calibrate the system and are not well suited to low power pacemaker applications where energy is lost during the calibration as the proper state configuration of the system is not yet obtained.…”

Wearable self‐tuning antenna for emergency rescue operations

“…A first characterisation aspect is related to the collection of the feedback data. One potential solution consists in measuring current or voltage values at different points of the circuit [11,12]. An alternative possibility is to sense the signals before and after the impedance matching network to determine the impedance mismatching level [13].…”