| With the rapid development of wireless communication technologies,the demands of RF front-end are increasingly higher. Active integrated antenna due to its small volume, high efficiency and multi-function is widely applied in requirements for military and commercial field antennas, such as phased array, millimeter wave power synthesis, wireless sensor and mobile communications. At the same time, as an emerging smart antenna, microstrip leaky-wave antenna with function of beam scanning and the advantages of low profile and easy integration has becomed a research hotspot in recent years.Composite right /left hand(CRLH) leaky wave antenna is one of the applications with CRLH transmission line. CRLH transmission line can transmit fast and slow waves at the same time. When CRLH transmission line transmits fast waves, it could work as leaky wave antenna and radiate backward, frontward and broadside with low profile. With these advantages, CRLH leaky wave antennas could integrate with active device or work as conformal surface applied to wireless and communication system. Distributed Amplifier(DA), as a traveling wave amplifier, multiple several amplifiers in parallel along the transmission line, which can achieve a good impedance matching and flat gain in a wide band. Based on the feature of traveling wave in common, this thesis researches the Distributed Amplifier and CRLH microstrip leaky wave antenna and proposed an improved active integrated leaky-wave antenna.The main work and achievements of this thesis can be summarized as follows:1. A miniaturized balanced low noise amplifier is presented. The proposed low noise amplifier, with miniaturized 3d B coupler, is designed by the method of lumped and distributed component matching network. The compact 3 d B coupler reduces the size of the circuit greatly. Simulated by AWR MWO software, the amplifier is fabricated and measured. Over the operating frequency band(1.85-1.95 GHz), the measured result shows a good operation.2. The operating principle and main characteristics of the Distributed Amplifier are discussed. Based on the small signal equivalent model, a Distributed Amplifier withwide operating band of 2.5~6GHz is designed. Its gain is aroud 10 d B and S11 is less than-10 d B. A distributed amplifier has been fabricated to conduct experiments. The measurement results are in good agreement with simulation results.3. Utilizing the theory of equivalent circuit, the principal characteristics and design methods of CRLH transmission line are introduced. Meanwhile, the CRLH microstrip leaky-wave antennas with Symmetrical and asymmetric structure are analyzed and compared in detail. Based on this, two CRLH microstrip leaky-wave antennas with 6 Symmetrical and asymmetric units is designed separately, which operate in balanced state. Both of them are capable of continuous scanning from backward to forward. The asymmetric leaky-wave antenna operated at frequency range from 2.4GHz to 6.8GHz(S11<-10 d B) and radiated at the range from-30° to 50°. The asymmetric leaky-wave antenna operated at frequency range from 2.6GHz to 6GHz(S11<-10 d B) and radiated at a wider range from-60° to 80°.4. By means of similarity in the traveling wave between the leaky-wave antenna and distributed amplifier, the CRLH leaky wave antenna is substituted for the drain line of the distributed amplifier. Meanwhile, a lumped CRLH transmission line having the same dispersion with leaky wave antenna is designed and substitutes for the gate line of the distributed amplify. It ensured the phase consistency between drain line and gate line. The measured results shows a flat realized gain of active leaky wave antenna, which is improved to about 5.5d B with only 6 CRLH units... |
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