| Millimeter-wave system have been widely used in many aspects such as precisionguidance,radar communication, aerospace monitoring and satellite communications.Themillimeter-wave low noise amplifier (LNA) in the receiver front largely decides thenoise level of the millimeter-wave receiver. Millimeter-wave LNA with broad band andlow noise coefficient plays a key role in high-performance millimeter-wave receiver.Thus it has great practical significance to develop the ultra low noise millimeter-waveamplifier for millimeter-wave system. On the basis of reading a large amount ofdocuments of millimeter-wave LNA at home and abroad,this paper described a balancedmillimeter-wave ultra-low-noise amplifier working at29~31GHz.It first introduces the basic theory of the LNA and its specifications. Balanced formwas chosen as the circuit realization form of the LNA after analysing and comparing thecharacteristics of different forms of LNA. Three kinds of3dB quadrature couplers weresimulated and analyzed. Branch waveguide coupler achieves the followingspecifications: greater than27dB input return loss; more than26dB port isolation from29to31GHz;90°±0.15°phase difference of the two output ports; less than0.15dBamplitude imbalance degree. This shows the coupler has low loss, high isolation, goodamplitude and phase consistency. Ka-band E-plane waveguide-microstrip probetransition is also simulated with input return loss greater than20dB and the insertion losless than0.12dB from26to40GHz.Again, in order to achieve ultra-low noise, low noise HMET die named EC2612from UMS Co. was selected to complete the design.Minimum noise match andmaximum transmission power match (both with double-T branched match) are appliedto the input and output of single-stage circuit to obtain ultra-low noise in a widefrequency band. Simulation shows that the noise figure of single-stage circuit is lessthan1.3and the gain is greater than9dB in29~31GHz. Simulation of the wholebalanced ultra-low-noise amplifier shows that the noise figure is less than1.54and thegain is greater than8.8dB. Finally the ultra low noise amplifier have been completedand tested.Test results shows that the ultra low noise amplifier noise figure is less than 2.6dB, and gain is greater than6dB in29~31GHz. |
