Yang Lu

PIFA Bandwidth Enhancement by Changing the Widths of Feed and Shorting Plates

The ultrawideband (UWB) systems require antennas having a very broad bandwidth. The planar inverted-F antenna (PIFA) is widely used in mobile systems due to its excellent performance. However, its bandwidth is very limited. This letter is aimed at addressing this problem by investigating the effects of changing the widths of the feed plate and shorting plate on the impedance bandwidth. It is shown that a PIFA with a much wider bandwidth (up to 65%) than previously reported can be achieved by optimizing the widths of the feed and shorting plates. Simulated and measured results are provided to verify the conclusion.

Reducing Ground-Plane Effects on UWB Monopole Antennas

A common problem with planar ultrawideband (UWB) monopole antennas is that their performance is heavily affected by the ground plane. To resolve this problem, a novel approach is proposed in this letter. Slots along the top edge of the ground are introduced to minimize the ground-plane effects by changing the current distribution. An equivalent circuit model is developed to obtain an insight view of the behavior of the slots. Computer simulation and measured results are obtained, and they confirm the validity of the proposed method.

Wideband antenna efficiency measurements

Over the past 10 years or so, many broadband and ultra-wideband antennas have been developed for broadband high data rate mobile communications. It is realized how to make efficient and accurate measurements for such antennas could be a challenging issue. In this paper, we examine the antenna efficiency measurement techniques which have been used up to now, and identify their advantages and disadvantages for broadband measurements. It is shown that the classic Wheeler cap method, which is the best for electrically small antennas, has a lot of attractive features even for broadband antenna measurements in terms of the cost and efficiency although the newly proposed reverberation chamber method may become a good alternative method. A “source stirred” method is proposed as a new approach for the broadband antenna efficiency measurement and its major advantages are cheap, convenient, and efficient. Both the experimental and numerical results are provided. It is shown that the loss due to the imperfection of the cavity can cause a serious problem for obtaining an accurate result. How to eliminate the effects of the cavity loss and improve the measurement accuracy for this method is an issue to be resolved.

An Empirical Equation for Predicting the Resonant Frequency of Planar Inverted-F Antennas

The planar inverted-F antenna (PIFA) is widely used in mobile systems due to its excellent performance. This letter introduces a new empirical equation for predicting the resonant frequency of PIFA, taking into account all the important parameters that significantly affect the resonant frequency. The comparisons between the new and the previously used empirical equations are provided to show the comparative accuracy of the new equation. The average % error found between the predicted and the actual operational frequencies is less than 3%. This proposed equation should be very useful to aid the PIFA design.

A further study of planar UWB monopole antennas

In this paper, we present a further investigation of microstrip-fed planar UWB monopole antennas using both the numerical and experimental approaches. The focus is on the characteristic mode analysis and the optimisation of the monopole design in term of its size and S11 performance. A comparison of elliptical and circular monopoles is also conducted.

A dual feed PIFA diversity antenna for MIMO systems

This paper presents a novel dual-feed Planar Inverted-F Antenna (PIFA) for MIMO radio communication systems at 2.45 GHz. This antenna contains only one radiating plate with two matched and isolated ports. To reduce the mutual coupling and to achieve a good isolation, ground plane under the top radiating plate is etched. The calculated envelope cross-correlation is less than 0.02 and the ratio of the mean effective gain between the two ports is close to unity. It is shown that a single PIFA antenna can be used instead of two antennas for diversity gain which is an excellent solution for saving the space and cost. Simulated and measured results are provided to verify the conclusion.

An elliptical UWB monopole antenna with reduced ground plane effects

Many monopole UWB antennas have been developed over the years. One common problem is that their performance is heavily affected by the ground plane. In this paper, a new approach on how to reduce the ground plane effects on such antennas is proposed: L-shape cuts on the edge of the ground plane are introduced and it is shown that this method changes the current distribution on the ground plane without sacrificing the frequency and time domain performance, which makes such antennas more suitable for real applications with different sizes of the ground plane.

Further bandwidth enhancement of PIFA by adding a parasitic element

The ultra wide band (UWB) systems require antennas having a very broad impedance bandwidth. The planar inverted-F antenna (PIFA) is widely used in mobile and portable devices due to its excellent performance. But it is not used as an ultra wide band antenna as it is assumed to be a narrow band antenna. This paper is aimed at addressing this problem by introducing a PIFA antenna having a parasitic element. It is shown that due to the addition of this parasitic element, this PIFA can achieve a very wide bandwidth (more than 95%). Simulated and experimental results are provided to verify the conclusion.

A further study of planar inverted-F antenna

This paper represents a simulated and experimental study of the planar inverted-F antenna (PIFA). It involves the changes in different parameters to observe their effects on the antenna characteristics such as the resonant frequency, impedance bandwidth and radiation pattern. It is found that the characteristics are affected by a number of parameters which include dimensions of ground plane, length, width and height of top plate, widths of shorting and feeding plates. The characterictics are also affected by the horizontal distance between shorting and feeding plates, the position of feeding plate under the top plate, the distance of shorting plate from one edge of top plate and the distance of PIFA structure from horizontal and vertical edges of ground plane. Taking these variables into account, a new empirical formula is proposed. These results will be very helpful in designing PIFA.

Effects of Wheeler cap loss on wideband antenna efficiency measurement results

Recently, Wheeler cap method was extended to measure wideband antennas. This paper presents an investigation on the effects of the loss of Wheeler cap on antenna efficiency measurement results. Two caps/cavities (one large and one small) are employed for this study and numerical simulation is also conducted to aid the analysis. Both the experimental and numerical results show the loss due to the imperfection of the cavity can cause a serious problem for obtaining an accurate result. How to eliminate the effects of the cavity loss and improve the measurement accuracy for the Wheeler extended method is an issue to be resolved.