The FET with the associated sections of transmission lines and radial stub constitute the oscillator part of the circuit, with the patch antenna being the load of the oscillator. The bias of the FET was implemented by feeding the center of the nonradiating edge of the patch antenna. The output of the photodetector will be connected to the input of the circuit, and the output will be connected to the mixer of the remote site.
Experimental results of the diplexerαpatch oscillator integration showed that the technique could be very useful for the optical-fiber-fed radio system. The patch oscillator was locked to an injected signal of 5.23 GHz, and the locking bandwidth was 26.7 MHz. The input power of a 5.97 GHz signal was 0 dBm, and it was recovered at the output of the diplexer with 5 dB insertion loss.
VI. CONCLUSIONS
In this paper, a new simple configuration for the opticalfiber-fed radio system has been proposed. This configuration has minimum complexity of the system central site where a dual-mode laser source generates the optical millimeter-wave signals, and offers the feasibility of a compact and low-cost implementation of the radio node. A 6 GHz full-duplex prototype module has been designed and implemented for the remote site of the radio on the fiber system. The prototype was an attempt to justify the use of printed circuit technology for the application of an optical-fiber-fed system. Radio interfaces of this type can reduce the cost and complexity of these systems. Although the implementation of the prototype is scaled down to the microwave region, it is believed that extension to a 60 GHz version would not imply any great difficulties. Furthermore, the concept of optically injection locking mutually coupled patch oscillators has been investigated, and the results showed that the mutually coupled patch oscillators can satisfy the power requirements of the optical-fiber-fed radio system, where power combining can take place in free space.