A LNA is directly integrated with a microstrip slot antenna to form an active antenna element. In integrating process, input matching circuit of the LNA is implemented by the input impedance of the microstrip slot antenna. As a result, it reduces the discontinuity of the input matching circuits. The integration can diminish the transmission line between the antenna and the LNA, which attenuates power loss and noise figure of the receiver. Because an active device and microstrip slot antenna are placed on the diffrent layers of substrate, the microstrip slot antenna may not be repaired for integrating active device, which decreases spurious radiation power and cross-polar radiation. Experimental results are compared with theoretical results at 2.40-2.50 GHz. It was found that the integrated receiver could have better performances in noise figure, power gain and radiation than cascade receiver.
