An Improved Design and Implementation of a Range-Controlled Communication System for Mobile Phones.

Haichun Zhang,Zhenglin Liu,Mingyang Gong

doi:10.3390/s20174997

Haichun Zhang, Zhenglin Liu + Show 1 more

Open Access

https://doi.org/10.3390/s20174997

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Abstract

The Short-range-controlled communication system (RCC) based on a subscriber identity module (SIM) card is a replacement for the standard near-field communication (NFC) system to support near-field payment applications. The RCC uses both the low-frequency (LF) and high-frequency (HF) wireless communication system. The RCC communication distance is controlled under 10 cm. However, current RCCs suffer from compatibility issues, and the LF communication distance is lower than 0.5 cm in some phones with completely metallic shells. In this paper, we propose an improved LF communication system design, including an LF transmitter circuit, LF receiver chip, and LF-HF communication protocol. The LF receiver chip has a rail-to-rail amplifier and a self-correcting clock recovery differential Manchester decoder, which do not have the limitations of accurate gain and high system clock. The LF receiver chip is fabricated in a 0.18 m CMOS technology platform, with a die size of 1.05 mm × 0.9 mm and current consumption of 41 A. The experiments show that the improved RCC has better compatibility, and the communication distance reaches to 4.2 cm in phones with completely metallic shells.

Highlights

Payment applications based on smartphones change peoples’ daily lives and make the world a better place
Some LF receiver chips are packaged in chip-on-board mode (COB), and a empty flexible substrate of the subscriber identity module (SIM) card is used because the LF receiver coil and coil matching circuits are inside it
The inner SIM card is placed in the middle of the mobile phone, and the HF signal is poorly disturbed by the device, with the situation worsening if the phone made with a completely metallic shell

Summary

Introduction

Payment applications based on smartphones change peoples’ daily lives and make the world a better place. The standard near-field communication (NFC) system is based on the International Organization for Standardization (ISO) protocol 14443 at 13.56 MHz [1,2,3,4] It can be used for both payment and for access control and other applications [5,6,7,8]. The SIM card’s working distance based on the LF receiver chip in [20] decreases to less than 0.5 cm in these new mobile phones. The die size of the LF receiver chip is decreased to 1.05 mm × 0.9 mm using a new analog frontend circuit, and more space is available for increasing the LF turning coil number in the SIM card.

System Building Blocks

Low-Frequency Transmitter

Low Frequency Receiver

Antenna Matching Circuits

Rail-to-Rail Amplifiers

Self-Correcting Clock Recovery Differential Manchester Decoder

Low Power Design

Frame Format of Low-Frequency Communication

Protocol for Range-Controlled Communication

Experiments

Waveform of LF Analog Frontend Circuits

Comparison with Previous Work