Radio systems at millimeter-wave (mm-wave) transmission frequencies have the potential to satisfy future user requirements for broadband services. Recently mm-wave frecpencies for wireless communication systems have been allocated to overcome crowding in the lower frequency spectrum [ 11. Mobile and personal radio systems at millimeter-wave transmission frequencies also offer the advantages of smaller equipment and antennas. Optical fibre signal feeds for these systems are of great interest because of their inherent advantages over coax and waveguide as a transmission medium. These include low loss, immunity to EMI, sizdweight reductions and the possibility of feeding many antennas rroni a single transmitter station 121. As a result there is also much interest in the generation and distribution of millimeter-wave signals using optical techniques.At present the intensity modulation bandwidth of state-of-the-art semiconductor lasers is less than 30 GHz. However the addition of an external cavity enables narrowband small-signal modulation of the laser at frequencies greater than the resonant frequency [3,4]. Other optical techniques for microwave and millimeter-wave signal generation include optical heterodyne [SI and harmonic generation using either intensity niodulntors 161 or pulsed semiconductor lasers 171. We hove recently dcvelopcd ;i new technique for the 0ptic:il generation of inillinletcr-wovc signals with 100 % tiiodu1;ition dcpth using a pulsed semiconductor Inser 18 1. In this paper, we demonstrate the application of this method to the feeding of :I millimeter-wave wireless link incorporating microstrip p:itch :uwmi:is. Microsti i p patches are very sit personal and mobile coinmuiiicotioti ;ipplications :is these ;intentias are low iit profile, light in weight ond cmi be easily itlteglatcd with both photonic devices and monolithic millimeter-wove integrated circuits. The optically fed link presented has application in indoor wireless LANs and optical fibre microcellular systems.
I1 Millimeter-Wave Antenna DesignTo design a microstrip patch in the millimeter-wave frequency range a rigorous full-wave analysis is required, such that all loss mechanisms (including surface wave excitation) are included. Also as the wavelength is small, the electrical thickness of commonly used substrates is relatively large and so reduced analyses (such as the cavity model) cannot accurately predict the input 0 7 8~2 7 1 % 5 / 9~. 0 0 0 1995 IEEE 1972