# Wideband Versatile Receiver for CubeSat Microwave Front-Ends
## 4 Receiver Performance  
In Figure 8, a picture of the entire receiver on a test platform is shown.  
The proper behavior of the receiver was tested by injecting tones within the entire frequency operating bandwidth, i.e., 2-18 GHz. In Figure 9a, the simulated output spectrum for an input power of \(-30\) dBm at the frequency of 2 GHz is reported. The simulated performance in terms of spurious rejection is confirmed by the measured data under the same conditions, as shown in Figure 9b.  
Figure 6: Measured S\({}_{21}\) (black solid line), S\({}_{11}\) (blue solid line), and S\({}_{22}\) (red solid line) of the (**a**) ZFL-1500 VH+ amplifier and (**b**) VLF-1500+ filter.  
Figure 7: Power budget of the receiver. The input power is equal to \(-20\) dBm.  
Figure 8: Picture of the microwave receiver.  
Figure 9: (a) Simulated and (b) measured frequency spectrum at the output of the receiver for an input signal with a center frequency and power equal to 2 GHz and \(-\)30 dBm, respectively.  
The measured down-converter conversion gain confirms the expected behavior over the entire frequency bandwidth. It was extracted by injecting input tones ranging from 2 GHz to 18 GHz, with an input power of \(-30\) dBm. The conversion gain is reported in Figure 10.  
As anticipated in the Introduction, the measured performance of the receiver confirmed the simulated behavior. A severe reduction of both the number and level of spurious signals is evidenced in Figure 9b, where the simulated results reported in Figure 9a were confirmed. The spurious level was maintained below the minimum signal detectable by the employed spectrum analyzer. This demonstrates a spurious level suppression equal to at least \(-45\) dBc.  
This very high spurious rejection was obtained without employing expensive systems but only exploiting the available COTS components. A quite flat compression gain was obtained, particularly from 6 GHz to 18 GHz. The higher variability in the low-frequency bandwidth can be attributed to the non-flat behavior of the amplification stages, which, of course, can be mitigated in the next revisions of the project. The power consumption of the microwave section with the amplifiers switched on is lower than 1 W. Due to the rapid passage of the CubeSat footprint on the ground transmitter, the receiving systems can be switched off for almost 24 h/day and switched on for a few minutes. This very low-duty cycle allows us to keep down energy consumption.  
The main performance of the downconverter is reported in Table 2.  
In the scientific literature, a microwave down-converter with these characteristics is not present, thus representing a good contribution to design and development in this field, hopefully stimulating research within the community.  
It is again worth highlighting the lack in the scientific literature of papers focused on very wide-band receivers. Often, commercial receivers are exploited aboard the CubeSat. As reported in Section 2, they are tailored for a narrow frequency bandwidth required by the specific application. This makes it challenging to implement an accurate performance comparison.  
The idea behind this work is to invert this standard approach by adding flexibility to CubeSat communication systems to be reused for different applications. This feature can be very beneficial not only in enabling different applications without changing the hardware but also in providing the largest bandwidth if required by the ground system.  
\begin{table}
\begin{tabular}{c c} Frequency (GHz) & 2–18 \\ Average CG (dB) & 8.4 \\ Minimum spurious & \(-45\) \\ suppression level (dBc) & 1 \\ Microwave section power consumption (W) & 1 \\ \end{tabular}
\end{table}
Table 2: The main performance of the reported downconverter.  
Figure 10: The measured conversion gain of the receiver. The input power is equal to \(-30\) dBm.