Analysis And Design Of Active Integrated Antenna Based On Minimum NF Matching

With the rapid development of wireless communication technology, the RF Receiver Front-enddesign is meeting more and more requirements. The design concept of active integrated antenna areconstantly being introduced into the structure designing of modern microwave and millimeter wave,and it is widely applied in communication system, Radar, GPS and many other fields. Now it hasbecame an important development direction of the future Antenna Technology. Active antennasintegrate passive antenna and active circuit together with. Viewing it as a whole or taking antenna asan integral part of the circuit design has not only simplified the design of Receiver Front-end, butalso reduced the loss.Based on the minimum NF matching, two LNA active antennas operating on WLAN in band2.4GHz and band5.8GHz were designed in this study. At the band2.4GHz, LNA chip ATF-54143is applied, while at the band5.8GHz LNA chip ATF-55143is used. Passive antenna is designed inrectangular microstrip patch structure. Firstly, the static working point and the stability of the LNAcircuit were designed, with a single power supply self-bias circuit. With the negative feedbackadded to the source of the transistor, the LNA circuit was in an absolute stability in the operatingfrequency range, and then the optimal noise input impedance Zoptwas calculated. Next, in thedesign of microstrip antenna, by optimizing the position of the feed point, the output impedance ofthe antenna was changed so that it is equal to or similar to the optimum noise input impedance ofthe active circuit. Finally, the active circuit and the passive antenna were directly matched forsimulation in the ADS. It omitted the matching networks and reduced the loss, besides, it reducedthe NF, and this is very beneficial to improve the sensitivity of the receiver. The simulation resultsshowed that, compared with the traditional active antenna which matched to50Ω, the directmatching active antenna is more conducive to the broadening of the frequency band because of itsoutput impedance is more smooth. What is more, the Power Gain and NF are more smooth in alarge frequency range.The maximum gain matching was studied too, compared with the minimum noise matching,the NF and the Gain increased slightly. In the single-stage amplifier system, this matching mode canreplace the minimum noise matching in the designing for active antenna. But it can not be used in amulti-stage amplifier circuit.