# A Space-Borne Ka-Band Tile-Type Phased Array Transmitter Module Based on HTCC Technology
## 3 Tile-Type Transmitter Module Based on HTCC Technology
### Transmitter Module Scheme Design  
The schematic of the proposed transmitter module is shown in Figure 3. The proposed transmitter module is designed for an antenna array or subarray of four radiation elements, so it consists of a four-channel multi-functional chip and four power amplifier (PA) chips. The input signal is pre-amplified and divided into four channels in the multi-functional chip. The amplitude and phase of the signal in each channel can be manipulated independently via the 4-bit digital control attenuators and 6-bit phase shifters, which are integrated in the multi-functional chip. Then the signal is amplified via a PA and sent to the antenna array for transmitting. The proposed scheme ensures the symmetry and ability of independent phase and amplitude control among four channels, which are key features to provide constructive interference in the desired direction, leading to the ability of radiation beam scanning. The configuration of three-stage amplifiers makes a good tradeoff between power consumption and output power. The link budget analysis is shown in Table 3 with an input power of \(-5\) dBm. The gain or insertion loss (IL) and the saturation output power of each component in the transmitter module are listed in the second and third columns in the table. The signal power at each stage of the link is listed in the fourth column. As the PA works at the saturation state for higher efficiency, the module achieves an output power of 21.2 dBm. The overall link gain can be calculated as 26.2 dB, which satisfies the performance requirements in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Design Requirements** \\ \hline Single channel gain (dB) & \(\geq\)26 \\ Saturation output power (dBm) & \(\geq\)21 \\ Efficiency & \(\geq\)40\% \\ RMS accuracy of phase shift (\({}^{\circ}\)) & \(\leq\)3 \\ RMS accuracy of attenuation (dB) & \(\leq\)0.5 \\ Inter-channel amplitude consistency (dB) & \(\leq\)0.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The main requirements of the transmitter module. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Characteristic** & **B210** & **W412** & **BX407** \\ \hline Color & black & white & black \\ Density (g/cm\({}^{3}\)) & 3.7 & 3.7 & 3.7 \\ Permittivity@1 MHz & 9.7 & 9.0 & 10 \\ Dielectric loss angle tangent & 3.3 \(\times\) 10\({}^{-4}\) & 2.3 \(\times\) 10\({}^{-4}\) & 13 \(\times\) 10\({}^{-4}\) \\ Dielectric strength (10\({}^{3}\) V/mm) & 27.8 & 28 & 20 \\ Volume resistivity@20 \({}^{\circ}\)C (\(\Omega\)-m) & 8.1 \(\times\) 10\({}^{13}\) & 8 \(\times\) 10\({}^{13}\) & 5 \(\times\) 10\({}^{13}\) \\ Linear expansion coefficient & 7.06 & 7.2 & 7.5 \\ @40\({}^{\circ}\)C (\(\times\)10\({}^{-6}\) /K) & 17.4 & 17 & 13.1 \\ Flexure strength (MPa) & 340 & 370 & 400 \\ Young’s modulus of elasticity (GPa) & 280 & 279 & 299 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of HTCC. The core of the transmitter module is a heterogeneously integrated multifunctional chip that consists of a four-channel GaAs chip for phase, and amplitude control and a Si-based CMOS chip that performs multi-channel serial-to-parallel conversion control, electrostatic discharge (ESD) protection, and power-on reset. The fan-in process is used to rewire the bonding points of the CMOS chip, allowing it to be heterogeneously integrated with the GaAs chip, thus combining the performance and size advantages of heterogeneous chips. The schematic of the chip is illustrated in Figure 4.  
The transmitter module is based on MMIC technology and HTCC substrate packaging integrated design technology. The schematic of the proposed transmitter module SiP is shown in Figure 5. Step cavities are formed on the substrate for MMIC chip mounting and electromagnetic shielding. A large number of metalized through-holes are designed in the substrate below the chip to achieve good grounding and heat conduction.