## 4 Experimental Results
### Measurements  
Figure 16 shows the measured scanning patterns of V\(-\) and H\(-\)polarization of the RX array at the central frequency of 11.7 GHz. As can be seen in Figure 16a, both polarizations can be scanned over a range of \(\pm 70^{\circ}\) in the azimuth plane. Using a Taylor amplitude taper, the sidelobe levels (SLLs) are lower than \(-18.3\) dB, \(-16.3\) dB and \(-13.2\) dB when the phased array is scanned to \(0^{\circ}\), \(\pm 60^{\circ}\) and \(\pm 70^{\circ}\), respectively. The gain drops are less than 4.2 dB and 6.1 dB, at \(\pm 60^{\circ}\) and \(\pm 70^{\circ}\) scan angles, respectively. In the elevation plane, the SLLs are lower than \(-18\) dB, \(-16.1\) dB and \(-12.6\) dB at \(0^{\circ}\), \(\pm 60^{\circ}\) and \(\pm 70^{\circ}\) scan angles, respectively, with the gain drops are less than 4.3 dB and 6.3 dB. To verify the circular polarization properties of the RX array, Figure 17 shows the axial ratios (ARs) of the array in the left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) states. Figure 17a shows the ARs of different frequencies at boresight are less than 0.77 dB. Note that different test frequencies use the corresponding calibration values. Figure 17b shows the ARs of 11.7 GHz at different scan angles. The AR is still less than 4.3 dB at \(\pm 70^{\circ}\), because double\(-\)feed antenna element has better axial ratio characteristics than single\(-\)feed antenna element. Figure 16: Measured scanning patterns at 11.7 GHz for the V\(-\) and H\(-\) polarizations. (**a**) Azimuth plane. (**b**) Elevation plane. Figure 15: Residual errors after calibration of the array (**a**) Amplitude. (**b**) Phase. (Different colors represent different subarrays). The G/T values of the proposed array were measured in the anechoic chamber at \(T_{\mathrm{ant}}\) = 290 K, as is shown in Figure 18. Similarly, different calibration values were used to test the array at different frequencies. The G/T of the array when pointed toward a cold and empty section of sky (\(T_{\mathrm{ant}}\) = 20 K) were calculated by:  
\[\mathrm{G/T}|_{\mathrm{20K}}=\mathrm{G/T}|_{\mathrm{290K}}+10\log_{10}\left( \frac{T_{\mathrm{array}}|_{\mathrm{290K}}}{T_{\mathrm{array}}|_{\mathrm{290K}} -270/10^{\frac{T_{\mathrm{ant}}}{10}}}\right) \tag{23}\]  
where \(T_{\mathrm{array}}|_{\mathrm{290K}}\) is the system noise temperature of the proposed RX phased array at 290 K.  
As is shown in Figure 18a, the G/T values at boresight were measured under uniform illumination and a Taylor amplitude taper, respectively. In the array's operating bandwidth, the G/T values were 11.9-12.4 dB at \(T_{\mathrm{ant}}\) = 290 K under uniform illumination. This was slightly smaller than theoretically calculated values, since the physical arrays were subject to machining, assembly, and residual phase and amplitude errors following calibration. The G/T value under the Taylor amplitude taper decreased by 0.23 dB, owing to a decrease in the aperture's directivity. The G/T values at \(T_{\mathrm{ant}}\) = 290 K were also 2.9 dB below those at \(T_{\mathrm{ant}}\) = 20 K. Figure 18b shows the variations in G/T values under different scanning angles at 11.7 GHz and uniform illumination. The G/T value at 70\({}^{\circ}\) was 6.2 dB lower compared to that at the boresight. A comparison of several other recently-reported RX SATCOM phased arrays with the proposed 2048-element \(Ku\)-band array is presented in Table 3. For those that use the same planar array structure, it can be seen that our multilayer PCB designed using the copper paste sintering process had fewer types of vias than those that were designed using conventional or HDI processes. Although only one kind of vias is reduced in this paper, the  
Figure 17: Measured axial ratio (AR) values of the array over (**a**) different frequencies at boresight, and (**b**) different scanning angles at 11.7 GHz. Figure 18: Measured G/T values of the array over (**a**) different frequencies at boresight, and (**b**) different scanning angles at 11.7 GHz.