Terence Shie Ping See

A Planar UWB Diversity Antenna

A planar dual-port diversity antenna, operating with broadside and/or conical radiation patterns in H-planes, is presented for ultrawideband (UWB) applications. The proposed antenna consists of a suspended square patch with a thick stem underneath. A broadband differential feeding strip is used to feed the square patch. The measured gain for the broadside mode is 8.4-10.3 dBi from 3.1 GHz to 5.2 GHz (50.6%), and the conical mode 3.2-5.1 dBi from 3.1 GHz to 4.9 GHz (45%). The measured reflection coefficients (|S 11|, |S 22|) are less than -10 dB over the frequency ranges and the isolation |21| between the two ports is greater than 13.5 dB. The operation of the differential feeding strip on the antenna is discussed. Both pattern diversity and partial polarization diversity are achieved for this antenna.

Antennas for WiFi Connectivity

Wireless fidelity (WiFi) is a superset of the IEEE 802.11 standards for communications over several tens of meters. A WiFi device connects to the network via an access point. The design of commercial WiFi antennas is a compromise between cost, size, manufacturability, and performance. This paper describes the design considerations of antenna from a WiFi system perspective with state-of-the-art solutions. The omnidirectional and multiband antenna solutions with diversity characteristics, particularly for access points and portable devices, are discussed. Case studies of a compact multiband antenna with omnidirectional coverage for access point application and a dual-band antenna system for portable devices are presented.

RF transmission in/through the human body at 915 MHz

The Medical Implant Communication Service (MICS), which was allocated by the Federal Communication Committee (FCC) on a shared, secondary basis in 1999, refers to a specification for using a frequency band between 402 to 405 MHz in communication with medical implants [1, 2]. It allows bi-directional radio communication with a pacemaker or other electronic implants. The maximum transmit power is limited to 25 µW, or −16 dBm, in order to reduce the risk of interfering with other users within the same band. The maximum usable bandwidth at any instant is 300 kHz, which makes it a low data rate system compared with WiFi (5.8GHz) or Bluetooth (2.4GHz). Other frequencies considered for implant communication include 915 MHz, 1.5 GHz, and 3.1–10.6 GHz ultra-wideband (UWB). The frequency band of 902–928 MHz is one of the Industrial, Scientific, and Medical (ISM) bands, commonly abbreviated as the 915 MHz ISM band. In this band, there are no restrictions to the application or the duty cycle. Furthermore, the allowed power output is considerably higher. Due to the lack of restrictions and higher allowed power, this band is very popular for unlicensed short range applications including audio and video transmissions. The FCC section 15.249 allows 50 mV/m of electrical field strength at a distance of 3 meters within the frequency band of 902–928 MHz. This corresponds to an EIRP of −1.23 dBm. A higher output power of up to 30 dBm is permitted if the system employs some form of spread spectrum such as frequency hopping or direct sequence spread spectrum since they are less likely to interfere with other systems and are also immune to interference from other systems.

Effect of wireless charging antennas on transmission of an antenna pair through human body

In this paper, the effect of the spiral antenna and the loop antenna for wireless charging on the transmission of an antenna pair comprising an external antenna and an implanted antenna through human body is studied. The transmission characteristic of the antenna pair with a wireless charging antenna positioned between the antenna pair is investigated over the frequency band of 3 - 5 GHz. It is found that the loop antenna features a limited effect on the transmission response while the spiral antenna causes the transmission response to change drastically across the frequency band. It is suggested that a loop antenna, compared to a spiral antenna, is a more efficient wireless charging antenna for an implanted radio system and causes less effect on the transmission between the external and the implanted antenna pair.

Implanted and external antennas for 915-MHz capsule endoscopy

This paper presents the design and performance of an implanted coil antenna for capsule endoscopy and a circularly polarized antenna for an external base station operating at a 915-MHz band (920–925 MHz). The measurement setup for characterizing the transmission characteristics between the external and implant antennas is designed and demonstrated. The data derived from the RF transmission measurements are essential for system link budget calculation.

Characterization of RF transmission in human body

The last decade has witnessed a rapid surge of interest in new sensing and monitoring devices for healthcare and the use of wearable/wireless devices for clinical applications. There has been a strong tendency to use implanted electronic device for therapeutic and diagnostic purposes. Recently, the Medical Implant Communication Service (MICS) technologies have been investigated with great interest. The MICS system is able to transmit information from an implanted antenna that is embedded inside the human body to the external device by using a wireless communication link. Using the MICS, a healthcare provider can set up a wireless link between an implanted device and a base station, which allows physicians to establish high-speed, ease of use, reliable, and short-range access to the patients health data in real time. The MICS system is able to reduce the frequency of diagnosis by the doctor and to alleviate the physical or mental burden of the patients. Furthermore, it is non-invasive as communication can be established without wire piercing of the skin, which reduces the risk of infection during a medical diagnosis.