## 3 Results  
Figure 4 top shows the Arduino Uno microcontroller transmitted bits. Figure 4 bottom show the GDD detected bits. A comparator circuit is used as a decision circuit that decides whether an incoming binary signal is at the logical 0 level or at the logical 1. The output voltage of this comparator is shown in the middle of Figure 4. The VDI MMW source used for the transmission of serial bits from the Arduino microcontroller had an MMW frequency of 100 GHz. The incoming binary signal was encoded using the Arduino Uno microcontroller and the message was shown using the Arduino software (serial monitor option). The SNR of the proposed system for distance between transmitter and receiver dishes of up to 20 m, depends mainly on the detector noise. The NEP and responsivity of the GDD were calculated for the electronic detection system at 100 GHz and resulted in 10 nW/\(\sqrt{\text{Hz}}\) and 31 V/W respectively [9]. The MMW source transmission power was about 600 mW, and the measured beam waist was about 10 mm. Therefore the total power collected by the GDD effective cross section is about 3.8 mW and, because of the On-Off modulation, the average power is approximately 1.9 mW. The GDD circuit of Figure 2 was connected to an amplifier with gain of 5, therefore the response of the GDD can be calculated by multiplying the received power of 1.5 mW by the responsivity of 31 V/W and by the amplifier gain of 5. The calculated response is therefore approximately 295 mV. The noise voltage is approximately 310 nv/\(\sqrt{\text{Hz}}\) and the bandwidth was about 1 MHz, therefore the noise voltage can be calculated to be about 0.31 mV RMS or 6.2 mV RMS after amplification. The signal shown in Figure 4 is about 270 mV peak to peak voltage as was expected (95 mV RMS). The SNR is therefore equals to about 24 dB. Thus, the performance of the communication link or (Pout/Pin) is 0.91, which means that 91 percent of the transmitted signal is received at the GDD plane. The Arduino Uno microcontroller was programmed to send the same message in loops. Based on typical chart for bit error rate of different modulation method [30] including On-Off keying shown in Figure 5 the bit error rate can be estimate at about 10\({}^{-12}\) for a signal to noise ratio of 24 dB.  
\begin{table}
\begin{tabular}{c c c c c c} \hline Distance between transmitter and receiver [m] & 15 & 20 & 50 & 100 & 500 \\ \hline Beam waist on the Transmitting dish [mm] & 92 & 92 & 92 & 92 & 92 \\ \hline Beam waist on the receiving dish [mm] & 175 & 220 & 518 & 1031 & 5161 \\ \hline Percentage of total power collected by the receiving dish. & 100\% & 99.86\% & 69\% & 26\% & 1.2\% \\ \hline Percentage of total power collected by the GDD detector (effective aperture diameter of 1 mm). & 1.64\% & 1.62\% & 1.13\% & 0.42\% & 0.019\% \\ \hline \end{tabular}
\end{table}
Table 1: Approximated beam diameter and approximated percentage of total power collected by the receiving dishes are given for transmitter to receiver distances of \(z=15\) m, \(z=20\) m, \(z=50\) m and \(z=500\) m.  
The experimental results shown in this study prove that the proposed MMW channel can be used as a MMW point to point backhaul network. Following this proof of concept, we can now realize high data rates and a very inexpensive MMW communication channel. MMW communication channel distances of hundreds of meters can be designed and constructed based on the proposed MMW channel.