# Space-Borne System-in-Package Based on High Reliability Microwave Interconnections
## 4 Packaging Design and Measurement of a Spaceborne Ka-Band Receiver  
The novel high reliability horizontal and vertical transmission structures described above are used for the metallic SIP design of a Ka band receiver. During the Ka band packaging design, the cavity division design is first carried out according to the function, frequency, and gain. Then the transmission structure described above is used to achieve the horizontal and vertical interconnection between the cavities. The following aspects need to be considered in packaging design:  
1. Avoid space coupling and crosstalk of microwave signals. Precise cavity division has been made for the Ka band receiver. The top of the packaging structure is divided into seven cavities and the bottom is divided into five cavities. Since the SIP is divided and the horizontal and vertical transition transmission structures  
Figure 21: Tolerance analysis of the distance D between substrate edge and conductor center. Figure 22: Actual photo of the vertical interconnection in the SIP. are used for interconnection, there will be no space coupling or crosstalk between cavities due to electromagnetic radiation or leakage [24]. b. Resonant frequency design of the cavity. In order to eliminate the cavity resonance near the working frequency and ensure that the resonant frequency of the cavity is much higher than the working frequency, the dimensions of all cavities are designed and simulated. From the simulation results, all cavities meet the application requirements. The model of the SIP cavities and their lowest resonant frequencies are shown as Figure 23 and Table 6.  
In order to eliminate this effect, 100 pf and 10,000 pf die capacitors are connected in parallel at each power supply pad nearby to filter out the stray signals, which come from the low-frequency power supply board. In addition, the power supply pads on the low-frequency power supply board and the vertical power seal are interconnected nearby, and the uF-level capacitor is connected in parallel nearby for filtering, so as to eliminate the crosstalk between low-frequency and RF to the greatest extent. Based on the method above, this spaceborne Ka band receiving SIP is composed of an RF low noise amplifier, an RF amplifier, an image rejection filter, a mixer, an intermediate frequency (IF) band-pass filter, an IF low power amplifier, an IF medium power amplifier, and an attenuator. It was manufactured, and the diagram and the photo are shown in the Figure 24. The circles show the locations of the proposed horizontal interconnects and the rectangles show the vertical ones. The design completes the functions of low noise amplification, frequency conversion, gain amplification, gain adjustment, and harmonic clutter filtering. The RF circuits are cascaded by microwave dies, microstrip lines on the substrate, and other devices by the novel interconnections above. The top and bottom circuits are interconnected through the novel horizontal and vertical seals. The local oscillator chain completes the functions of frequency doubling, gain amplification, and filtering. The local oscillator chain is similar to the RF, and it is realized by cascading dies and microstrip lines with the same interconnections. After the measurement, the SIP was subjected to a temperature cycling test of \(-35\)- +70 \({}^{\circ}\)C for 200 cycles, followed by a mechanical impact test with a peak acceleration of 1500 g and a pulse width of 0.5 ms. After the environmental compatibility tests, the system package was tested again, and its performance was still excellent, as shown in Table 7. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Test Items** & **Measured Value** \\ \hline
1 & Input frequency & 30 GHz \\
2 & Output frequency & 4 GHz \\
3 & Bandwidth & 800 MHz \\
4 & Gain & 57.1 \\
5 & Gain flatness & 0.55 dB \\
6 & Noise figure & 2.8 dB \\ \hline \end{tabular}
\end{table} 
Table 7: Performance of the Ka band receiving SIP through the environmental compatibility tests.