# A W-Band Communication and Sensing Convergence System Enabled by Single OFDM Waveform
## 5 Experimental Setup and Results  
In this work, we also implement an experimental demonstration. Figure 6 shows the configuration of our system in the experiment, which is composed of several blocks in the digital and analog domain for transmission and reception. In our experiment, the baseband 16-QAM OFDM waveform is digitally generated for communication and sensing using parameters listed in Table 2. An oversampling factor of 20 is used before the signal is digitally up-converted to an intermediate frequency (IF) at 3 GHz through the IQ mixing. The IF signal is then fed to an arbitrary waveform generator (AWG) operating at 120 GS/s. Before the free-space transmission, the signal is up-converted to the W-band with a carrier frequency of 97 GHz using a commercially available W-band mixer at 94 GHz. Subsequently, a W-band amplifier with 10 dB gain is used to boost the signal to around 0 dBm, and a pair of conical horn antennas with a gain of 30 dBi is used for transmission and reception. At the receiver, the signal is first down-converted into the IF domain using a similar W-band mixer, sampled using a digital sampling oscilloscope (DSO) (KEYSIGHT MXR608A, sampling rate of 16 GS/s, bandwidth of 6 GHz) and then processed digitally to retrieve the baseband signal for further processing. In the digital domain, typical Fourier sidelobes are suppressed by using the Hamming window.  
The photos of the experimental setup are shown in Figure 7a-c. Figure 7a shows the arrangement for realizing the reflective sensing to measure the range of two static targets with flat reflective surfaces. Figure 7b shows the setup for speed and range measurement with a static target and a moving target. The speed is measured via a reflective target mounted on a belt, which moves the target along the LOS and away from the receiver with adjustable speed. In this case, the Doppler frequency shift is induced in the signal reflected from the moving target, and the down-conversion from W-band carrier frequency to an IF yields a sinusoidal of the Doppler frequency, which can be observed at the DSO. Observation of the sinusoidal-like variations in the received signals at the DSO indicates the correct measurement arrangement for speed measurement.  
Figure 5: (**a**) One static target at 0.6 m and one moving with 5 m/s using the conventional OFDM–based sensing. (**b**) Results by using the proposed range extension method for the scenario in (**a**). (**c**) Range–speed plot for targets at 0.85 m and moving with 2.34 m/s, with second and third static targets at 12.65 m and 17.65 m, respectively. (**d**) Range–speed plots obtained by using the proposed range extension method for targets mentioned in (**c**).  
The setup is calibrated during range measurement, and we measure different cases for illustrating the range and speed measurements, as listed in Table 3, where \(d_{1}\) and \(d_{2}\) are the actual distances of targets from the receiving antenna and \(\hat{d_{1}}\), \(\hat{d_{2}}\) represent measurement results. Similarly, \(v\) and \(\vartheta\) in Table 3 represent actual and measured speeds, respectively. For the data transmission part, a LOS link is established by placing the receiver at the location of the static target, as shown in Figure 6(c). In the following subsections, we discuss experimental results obtained from the measurements.