# Recent Developments and State of the Art in Flexible and Conformal Reconfigurable Antennas
## 3 Pattern-Reconfigurable Antennas
### Dual Mode Antennas  
Recent advances in communication technology have led to the advent of antennas for body area networks (BANs) applications. The suitable radiation pattern for connecting nodes that are placed on-body is monopole-like patterns and connecting nodes that are placed on-body and off-body are broadside patterns [88]. New types of the flexible dual-mode antennas which reconfigure between on-body and off-body radiation patterns have been presented [89; 90; 88; 91; 100].  
In Reference [88], a flexible reconfigurable dual-mode microstrip antenna operating at 2.45 GHz is presented. A ring and a meandered patch with two different feeding ports and the same ground plane are combined in one structure for the on-body and off-body modes, respectively. The pattern of the antenna is changed by switching between two feeding ports, the monopole-like of the ring pattern and a broadside pattern of the meandered patch. The pure copper polyester taffeta fabric is used for the conductive parts of the antenna and it is placed on felt with \(\varepsilon_{r}=1.17\) and loss of 0.016. The effects of the body tissue on antenna performance is investigated by placing an antenna on a phantom.  
The dual-mode feature by having broadside radiation pattern at 2.5 GHz and a conical-like radiation pattern at 5.8 GHz in the triangular patch antenna is achieved [99]. A conductive textile is used for the patch and the ground plane and antenna is placed on the substrate with \(\varepsilon_{r}=1.63\) and loss tangent 0.04. The reconfigurability is achieved by using three vias and two symmetrical open-ended slots. The proposed flexible microstrip patch antenna in [100], reconfigures between on and off-body communications at 2.45 GHz by employing two PIN diodes. The textile material felt and a conducting fabric pure copper taffeta is utilized for dielectric layers and metallic layers, respectively.  
As it is mentioned before, mechanical tuning techniques including physical deformation, stretching, or folding for pattern reconfigurable are presented as an alternative to electronic tuning [90]. A mechanical pattern reconfigurable antenna based on liquid metal and microchannel inside a polymer is presented in [90]. This antenna comprises a \(9\times 5\) array of metal dipoles which are inside platinum-cured thermoset silicone with \(\varepsilon_{r}=2.2\) and loss of 0.016. To form the dipoles, EGaIn is injected into the channels inside the substrate. Pattern reconfigurability is achieved through elongation from 0 to 53% to theta 0 to \(\pm 55^{\circ}\) and surface reshaping to 0, \(\pm 37\) and \(\pm 58\) for flat, convex and concave, respectively. In a fully textile reconfigurable ultra-wideband (UWB) antenna, the pattern is switched between a monopole-like shape from 2.62 GHz to 10.1 GHz and a microstrip-like shape from 2.73 GHz to 10.1 GHz [89]. The reconfigurability in this antenna is achieved by raising and lowering a textile flap which is the main radiator. As Figure 6 shows, when this textile flap is parallel to the ground plane, the structure behaves like a microstrip antenna with a unidirectional pattern. When in the orthogonal position to the ground plane, the structure acts as a monopole antenna with an omnidirectional pattern.  
Figure 6: The measurement set-up for proposed fully textile reconfigurable UWB antenna with two monopole-like and a microstrip-like patterns ([89], reproduced courtesy of The Electromagnetics Academy).