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A technique is proposed to mitigate the unwanted effect of ground plane currents when an antenna is mounted on a printed circuit board (PCB). To demonstrate the concept a CPW fed monopole is integrated onto a relatively large PCB. In the first stage of integration, a microstrip to grounded CPW feedline is incorporated to avoid connecting the PCB and antenna ground directly. To reduce the flow of current onto the edges of the PCB, two pairs of quarter-wavelength stubs are then utilised. A prototype is manufactured and examined. To show how this method enhances the radiation characteristics, the radiation patterns of the antenna in both an isolated and an integrated scenario with and without stubs are compared.Introduction: Since the FCC has allowed licence-free usage of the spectrum from 3.1-10.6 GHz for low power short impulse ultra-wideband (UWB) applications [1], planar monopole antennas have been much studied in the literature [2][3][4]. They are low profile, light in weight, cost-effective and easy to manufacture and have wide impedance bandwidth and stable radiation characteristics. However, when mounted on a printed circuit board (PCB), their radiation characteristics degrade owing to the coupling between the antenna and the PCB. The current flowing onto the edge of the PCB contributes to the radiation and deteriorates the radiation patterns.In this Letter, the isolation between the antenna and the PCB is addressed. A CPW fed monopole antenna is integrated into a relatively large PCB to demonstrate the concept. Two pairs of quarter-wavelength microstrip stubs are utilised to reduce the flow of current onto the PCB edge. The proposed technique is examined for the European UWB mask, which is partly focused on the frequencies between 6-8.5 GHz [5]. However, the technique can also be used for a wider frequency range. A prototype of the antenna is fabricated and examined. Details of the proposed strategy together with the simulated and measured results are presented.

The growing demand for broadband multimedia services urges the aeronautical industry to provide bidirectional on-board communication services in near future. Today, the first aircrafts are already being equipped with the technology necessary to provide intemet access for staff and passengers. Up to now, these solutions are developed to operate in L-and Ku-Band, due to the satellite systems available and the existence of affordable RF-components for these frequency ranges. Considering broadband multimedia applications, however, it is obvious that in the near future the technology will have to explore higher frequency regions like Ka-Band, where the required bandwidth can be provided. Several studies show that, for airbome broadband satellite communications, the terminal antenna is one of the key components in the system design. To compensate for the aircrafts movement, the terminal antenna must be steerable, to allow satellite tracking. Due to the limitations of mechanically steerable antennas, an electronically steerable array antenna using digital beamforming seems to be the most promising solution. Still, the development of such antenna arrays in Ka-Band technology faces high demands regarding performance, integration and, last but not least, component costs. In the framework of a project called SANTANA (Smart ANtenna TermiNAl), funded by the german government (BMBF) on behalf of the DLR, several antenna concepts have been investigated. One promising concept, which will be discussed in this paper, is a transmit-only array at 30 GHz that uses the sequential rotation principle to improve the circular polarisation.