As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. For instance, ultra wideband radio (UWB) will utilize the frequency-band of 3.1-10.6 GHz. Microstrip patch antennas have advantages of low cost and compatibility to the printed circuit board (PCB) technology, having the possibility to integrate the antenna with the circuit board. Since patch antennas have ground planes, components can be placed on the other side of the PCB, this allows a compact module design. However, the microstrip patch antenna has drawback of small bandwidth. Bandwidth is limited since the substrate height is limited. To overcome these drawbacks, we have studied a method to use a patch array with varied patch lengths on a low loss PCB. Patches electrically far away from each other will give independent resonances. By choosing several patch lengths so that the standing wave ratio (SWR) plots of the antennas overlap, they can be combined into one wideband with a power-divider. Several arrays can be combined to a multi-band antenna system using switches. A patch antenna array for the multiband UWB in the frequency band of 3.1-10.6 GHz is presented in this paper.

As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. For instance, the ultra wideband radio (UWB) utilizes the frequency band of 3.1-10.6 GHz. The spiral antenna has a higher spectral efficiency than other planar antennas like the patch antenna. Theoretically, any type of antennas can be combined into different kind of arrays, in order to improve performance beyond that from one single antenna. The electrically coupled parallelism is one solution to extend bandwidth. By combining two spiral antennas with different radius of the radiation zone, the standing wave ratio (SWR) can be kept low for a large bandwidth, resulting in an improved spiral antenna performance for UWB. Furthermore, a study of how spiral dimensions impact on gain and SWR was conducted and presented.

One of the trends in wireless communicationis that systems require more and more frequency spectrum.Consequently, the demand for wideband antennas increasesas well. For instance, the ultra wideband radio (UWB)utilizes the frequency band of 3.1-10.6 GHz. Such abandwidth is more than what is normally utilized with asingle low-profile antenna. Low profile antennas arepopular because they are integratable on a printed circuitboard. However, the fractional bandwidth is usually anissue for low profile antennas because of the limitedsubstrate height. The monofilar spiral antenna on the otherhand has higher fractional bandwidth, and at GHzfrequencies the physical dimensions of the spiral isreasonable. Furthermore, a study of how spiral dimensionsimpact on antenna gain and standing wave ratio (SWR) wasconducted and presented. Simulated results were comparedwith measurements.

As wireless communication applications grow rapidly, the demand for modular solutions with high performance and low profile antennas increases. For instance, the ultra wideband radio (UWB) utilizes the frequency band of 3.1-10.6 GHz. Integrateable antennas should be of planar structures. A Planar structure limits design options, regarding various performance aspects. For instance, the spectral efficiency, i.e., the bandwidth (BW) relative to the center frequency (CF) is limited. The antenna efficiency, i.e., gain relative to directivity is also limited. The antenna efficiency is important for receiver sensitivity, which is important in UWB systems. The efficiency is dependant of the antenna structure and material used. The Rogers 4350B material is suitable for high frequency modules since it has a low loss tangent that is stable over a wide frequency range, but the substrate height is limited. In this study a printed circuit board (PCB) with an air core was introduced to increase the antenna efficiency. The module is processed as two separate double-layer PCBs. This technique can be implemented to increase the performance in a narrowband as well as in a wideband antenna system. An advantage is that components can be placed on the other side of the ground plane without interference since the ground plane shields components from antenna radiation. A study of how the antenna bandwidth and efficiency are improved with the proposed structure at 3.5 and 10 GHz was conducted and presented.

An invented frequency multiplexing technique is used to combine inverted-F antennas for multi-band UWB. The frequency multiplexing technique allows a number of independent antennas to be used in parallel. In this paper a radio front-end system consisting of three antennas and a frequency multiplexing network is built. Using one antenna for each sub-band within a band-group provides equal performance for the entire band. Both the antennas and the frequency multiplexing network can be integrated on a printed circuit board. The antennas were simulated and measured. S-parameters of the antennas were extracted and used for co-simulation with the frequency multiplexing network. The antenna system fulfills the requirement for Mode 1 UWB.

An ultra-wideband (UWB) 3.1-4.8 GHz radio front-end consisting of three frequency multiplexed antennas and a low-noise amplifier (LNA) is presented in this paper. Using one antenna for each sub-band and an LNA designed for maximum-flat power gain provides equal performance within the entire frequency band. Frequency multiplexing is used to combine the antennas for multi-band UWB. The LNA is optimized for wideband operation and minimum noise figure. The LNA design employs dual-section input and output matching networks. The antennas, the frequency multiplexing network, the matching networks and the bias circuit of the LNA are all implemented using microstrip lines.

A fully integrated triplexer for multiband ultra-wideband radio is presented. The triplexer utilizes a microstrip network and three combined broadside- and edge-coupled filters. It is fully integrated in a printed circuit board with low requirements on the printed circuit board process tolerance. Three flat subbands in the frequency band 3.1-4.8 GHz have been achieved. The group delay variation within each 500-MHz subband was measured to be around 1 ns. A good agreement between simulation and measurement was obtained.

A fully integrated triplex antenna system for multibandUWB 3.1-4.8 GHz is presented. The system utilizes amicrostrip network and three combined broadside- and edgecoupledfilters to connect three inverted-F antennas in parallel.The triplexd antenna system is fully integrated in a printedcircuit board with low requirements on the printed circuit boardprocess tolerance. The group delay variation within the triplexerwas measured to be less than 1 ns. Furthermore, a goodagreement between simulation and measurement results wasobserved.

Bias networks with radio frequency (RF) chokes can be implemented using different microstrip elements. They can have different advantages in terms of bandwidth and occupied area. However, sharp discontinuities of the transfer functions have been observed in these types of bias networks. In this paper they are explained by resonances generated within the DC path of the bias network. As the resonance behavior degrades the performance of broadband RF circuits, the robustness of different bias networks against resonance was investigated. Different bias networks were fabricated and measured. Both simulation and experimental results show that broadband microstrip bias networks can be optimized to avoid or reduce the resonance phenomena.

A multi-band and ultra-wideband (UWB) 3.1-4.8 GHz receiver front-end consisting of a fully integrated filter and triplexer network, and a flat gain low-noise amplifier (LNA) is presented in this paper. The front-end utilizes a microstrip network and three combined broadside- and edge-coupled bandpass filters to connect the three sub-bands. The LNA design employs dual-section input and output microstrip matching networks for wideband operation with a flat power gain and a low noise figure. The system is fully integrated in a four-metal-layer printed circuit board. The measured power gain is 10 dB and the noise figure of the front-end is 6 dB at each center frequency of the three sub-bands. The minimum isolation between the sub-bands is -27 dB and the isolation between the non-neighboring alternate sub-bands is -52 dB. The out-of-band interferer attenuation is below -30 dB.

Fully integrated monopole and dipole antennas forultra-wideband (UWB) radio utilizing flexible and rigid printedcircuit boards are presented in this paper. A circular monopoleantenna for the entire UWB frequency band 3.1-10.6 GHz ispresented. A circular dipole antenna with an integrated balun forthe frequency band 3.1-4.8 GHz is also presented. The balunutilizes broadside-coupled microstrips, integrated in the rigidpart of the printed circuit board. Furthermore, anomnidirectional radiation pattern and high radiation efficiencyare predicted by simulations.