Link Budget Parameters. This link was realized at ULIL, by radiating the 300 GHz beam in the free space using conical horn antennas, fed by a WR3.4 (220-325 GHz) band. Such antennas provide a typical gain of about 25 dBi. Then the signal was collimated using a 100 mm Teflon lens. Using a free-space VNA setup we estimated that the gain of such a system (horn + lens) is featuring a total gain around 38 dBi. The same configuration of lens/horn is used at the receiver, for signal detection in the receiver. Fig. 6 shows a view of the TX, RX and lenses. The 10-meter transmission is obtained with a reflection on a mirror placed at 5-meter distance from the emission/detection circuits. The link budget of the transmission is presented in Table 1. The output power of the TX module has been measured for signals with different modulation types, symbol rates and IF input powers and varies between -10 and -5 dBm. For simplicity, an average of -7 dBm is used for the link budget calculation. At 310 GHz carrier frequency the free space path loss (FSPL) over 10 meters is 102 dB. The atmospheric losses can be neglected. To achieve an optimum input power for the receiver a variable attenuator is placed between reception horn and RX module. The attenuation value is set to 10 dB, which leads to an RF input power of -43 dBm, which corresponds to the optimum point of the receiver’s sensitivity curve measured previously and presented in [3]. Fig. 6. View of the 300 GHz transmit-receive system including collimating lenses. Table 1 Link Budget Parameters Parameter Unit Value Comment Centre frequency GHz 310 LO plus carrier offset TX output power dBm -7 Measured TX and RX overall antenna gain dBi 38 Including horn antennas, collimating lenses and mirror Link distance m 10 Free space path loss (FSPL) dB 102 Extra attenuation dB 10 to drive the RX in its optimum sensitivity point RX input power dBm -43 Value expected from the receiver design
