Study And Fabrication Of The Miniaturized 900 MHz LTCC Microwave Power Amplifer Module

It is well know that the microwave power amplifier module is one of the most important part of microwave transmitter. Its main function is to amplify and transmit the upconvertor's signal. It is applied to various kinds of ground equipment and satellite transponder. There was captured by foreign brand basically in the market of mobile communications in our country. The mobile communication system belongs to the intensive system of the device, and it can't be regarded as the genuine production domesticization without the domesticization of the device. In order to improve the competitiveness of national information, it is imperative to develop the independent power amplifier module.For designing the microwave power amplifier formed by the chip of SiGe HBT more accurately, an novel method to extract chip s-parameter from s-parameter of packaged device with package is proposed. First we measured s-parameter of the device and package shell. The package shell and bonding wire are expressed with equipment circuit composed of the resistance, capacitance and inductance Then acquired the value of component by optimizing using microwave emulation software (Microwave Office). Subsequently, we can get the chip s-parameter by adding the negative equipment circuit of the parasitic parameters in the s-parameter model of packaged device.For the problem of poor cohesion and the difficult process follow-uply, such as mount the components in the LTCC substrate. Besides, it's easy to short circuit between each electrode because of the small size of chip. We carried on the experiment of mount components and chip bonding. Trough the experiment, we probed to the suited mount method (mount with 183℃ soldering paste) and bonding technique (Ball bonding with the gold silks of 18 μm in diameter). Therefore the components were mounted in the substrate firmly and chip worked steady. We designed and fabricated LTCC power module on the basis of solving a series of difficult problems about technology.The amplifier adopted the three-stage structure, and the first stage used one chip, the second stage used two chip in parallel, the third stage used four chip in parallel. We first designed the single layer power amplifier using epoxy substrate. It can offer reference for LTCC power amplifier. First, passive resistance network was selected as direct current biasing network, which offered direct voltage for base through the resistance voltage divider composed of two resistances, among them the upper resistance connected from the DC to base, the lower resistance connected from the base to ground. The collector connected with DC directly. The lower resistance should select properly, too big to make radio frequency signal drive collector current too little, too small to make amplifier instable easily. The lower resistances of three stagewas selected respectively as 240Ω,220Ω,100Ω. The first and second stage worked in class A operation and the third stage worked in AB operation. The high frequency matching network mainly used lumped element lowpass network, including the series capacitance, series inductance and shunt grounded capacitance. Assuring the basic performance of circuit through the emulation using Microwave Office. Then we assembled the circuit according to the result of the emulation. Last, modulating the circuit and acquiring the favorable result. The result of actual circuit is difference with that of emulation, this because software emulated according to strict circuit model and can't involve some practical factors, such as the via to ground, microwave connector. Moreover, the Q value of capacitance and inductance is not involved. With the increase of input signal, gain compress become quickly and the gain on the condition of large signal is lower. The reason is that emulation is implemented according to S-parameter of small signal, and the change of chip parameter is not taken into account. After the analysis, we think the reason is that interstage matching between second stage and third stage, output matchin...