# A VHF Band Small CRLH Antenna Using Double-Sided Meander Lines
## 3 Fabrication and Measurement  
Figure 7 shows the fabricated antenna with 7-unit cells, and Figure 8 shows the return loss of the proposed antenna. The reflection coefficient of the antenna was measured using a Rohde & Schwarz ZVA 67 Vector network analyzer [28]. There was a 1 MHz difference in resonant frequency between the fabricated antenna and the simulated antenna. This may be due to inaccuracy during the manufacturing process and experimental tolerance. The  
Figure 5: The CRLH TL antenna structure at the bottom: (**a**) 3-unit cell; (**b**) 5-unit cell; (**c**) 7-unit cell. Figure 6: Normalized radiation pattern of the proposed CRLH TL antenna. The results of the 25-day fabricated antenna operated at 84 MHz and had a bandwidth of 2% (83.7-85.3 MHz) based on VSWR 3.5:1. Next, to verify the performance of the proposed antenna, the received power of the antenna was simply measured and compared with simulation results. Figure 9 shows the received power measurement environment. The transmitting antenna is an OMNI-A0245 antenna from Alaris [29], and a ground plane of 1500 \(\times\) 1500 mm\({}^{2}\) size was used as required in the antenna data sheet. The ground plane was wrapped in copper tape on Styrofoam. The transmitting power was generated by Agilent's E4422B ESG Series Signal Generator [30], and the received power was analyzed with Agilent's E4411B ESA-L Series Spectrum Analyzer [31]. The distance between the transmitting antenna and the receiving antenna was 30 m, and the transmitting power was set to 25 dBm and transmitted at intervals of 1 MHz. The received power of the antenna was measured by fixing the antenna in the direction of the maximum radiation (\(\theta\) = 90\({}^{\circ}\), \(\phi\) = 10\({}^{\circ}\)). In order to compare with the simulation results, the measured received power was converted into an antenna gain, as shown in Figure 10, using the Friis transmission formula [32], shown in Equation (3). \(P_{r}\) and \(P_{t}\) are the received power and the transmitting power, respectively. \(G_{r}\) and \(G_{t}\) are the gain of receiving antenna and transmitting antenna, respectively. \(L_{r}\) and \(L_{t}\) represent cable loss and mismatching loss as receiving loss and transmission loss, respectively. The cable loss was measured with or without cable connection, and the mismatching loss was calculated using the s-parameter characteristics of the data sheet for the transmitting antenna. In the case of the receiving antenna, it was calculated using the s-parameter characteristics measured using the VNA (Vector network analyzer), and the considered loss value was about \(-7.8\) dBm. \(\lambda\) and R are the wavelength and the distance between the antennas, respectively. Since the proposed antenna operates at a frequency below 100 MHz (1\(\lambda\) = 3m), it is hardly affected by surrounding objects. In addition, since it has a highly miniaturized size compared to the wavelength, and thus satisfies the far-field condition, it  
Figure 8: Normalized radiation pattern of the proposed CRLH antenna. Figure 7: Fabricated antenna with 7-unit cells. was calculated by applying the Friis transmission formula. From the calculated results, it can be seen that the proposed antenna can obtain \(-22.7\) dBi at 84 MHz and can be used as a receiving antenna [26; 27]. In the band where the antenna operates, the received power did not exceed \(-40\) dBm, so it was possible to measure it and it could be converted into an antenna gain. However, due to the low SNR performance of the spectral analyzer used in the experiment, the signal was not detected by noise at frequencies with antenna gain of approximately \(-40\) dBi or less. Actually, the detectable signal was about 50 dBm or more, and the expected received power in the range of 60-75 MHz was \(-50\) dBm or less, so the received signal was not detected. \[\frac{P_{r}}{P_{t}}=(\frac{\lambda}{4\pi R})^{2}G_{t}G_{r}L_{t}L_{r} \tag{3}\]  
Figure 10: Measured and simulated gain of the proposed antenna.