We have been working on several challenging technologies that not only improve signal reception quality in RF systems but also contribute to enhancing the performance of wireless communication systems. We have a number of exceptional technical engineering solutions as explained below.
Multi-mode DR Filter Design Tool
Next generation wireless communication systems will require a large number of high performance (low insertion loss, high rejection, thermally stable, etc.) filters in miniaturized package with low cost. Today, the two common filter technologies for base station applications are: 1) coupled coaxial cavity filters, and 2) dielectric resonator based structures. Among them, Dielectric Resonator (DR) filters offer great promise for wireless base stations. They have been considered very promising and are expected to grow fast in the upcoming years. ActsPower is currently involved in development of CAD tools for design and modeling of novel shape multi-mode dielectric resonator filters. Our goal is to optimize the filter structure for facilitating the tunability while maintaining high power handling for wireless base station applications.
RF Filter Design Software Tool Development
In RF filter designs, baseline filter specifications are derived from the target system requirements. Our RF filter design tools provides all stages of standard RF filter design flow including the polynomial approximation, topology selection, coupling matrix synthesis and approximate modeling. This software tool also provides the SPICE circuit models that can be used in RF circuit simulation tools such as Agilent ADS or Microwave Office to easily tune/optimize the individual filter elements along with other front-end circuit components and further refine the design and verify frequency performance and define baseline geometries.
24GHz Radar Transceiver
24 GHz radar transceivers have been widely used in automobile collision avoidance applications in recent years. Complexity, cost, power dissipation, and the number of external components have been the primary criteria in selecting transceiver architectures. The main available architectures for the transceivers are homodyne (zero-IF), heterodyne (IF) and the low-IF architectures. The analog part of the transceiver is composed of five main parts: LNA, up/down-converter, IF amplifier and filter, local oscillator and power amplifier (PA). ActsPower has successfully designed and fabricated a 24GHz transceiver system prototype for radar applications.
Interference Cancellation Systems (ICS's)
The on-Frequency Repeater (OFR) is a kind of repeater that amplifies an input signal without altering its frequency spectrum. Although it provides maximum spectral efficiency, it suffers from an important drawback. In an on-frequency repeater the output signal can feed back to the repeater input via a so-called “leakage channel†and causes self-oscillation. Therefore this system requires high levels of isolation between transmission and reception antennas. By adding Interference Cancellation Equipment (ICE’s) which prevent self-oscillations, high isolation can be acquired.
Block Diagram of RF Leakage Canceller
Software-Defined Radio (SDR)
Novel smart reconfigurable antennas and multi-antenna structures integrated with adaptive front-end circuits are researched and developed. This work focuses on two main tasks: 1) simulation, design optimization, and prototype development for smart reconfigurable antenna and multi-element antenna structures, 2) adaptive front-end circuit to optimize signal reception/transmission between the antenna and the radio front-end.
Intelligent Handset Antennas
Performance levels expected from future generation wireless information networks require a high quality signal reception under time-varying physical environment around the antenna. Many portable information appliances use internal antenna elements that are placed inside the portable box close to one of its faces. Several types of antennas have been used for this purpose. One of the most popular ones is Planar Inverted F-Antenna (PIFA) or one of its variants. One of the drawbacks of PIFA is its lower gain and radiation efficiency compared to more efficient exterior elements such as asymmetrical monopoles or helices. Furthermore, with internal antennas, there are always chances that the user covers the entire antenna or parts of it by his hand or other parts of his (her) body. This can seriously deteriorate the performance of the antenna, in terms of gain, efficiency, directional properties, and polarization.
We are currently working toward several techniques for addressing these problems. Our focus is on development of adaptive impedance matching circuits, antenna geometry optimization and innovative antenna feeding mechanism.
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