Figures & data
Figure 1. A 3D numerical model of the probe-fed cavity-backed resonant patch antenna studied in EM simulation software, HFSS®.
![Figure 1. A 3D numerical model of the probe-fed cavity-backed resonant patch antenna studied in EM simulation software, HFSS®.](/cms/asset/6787b56d-35ae-44f4-86b3-29d10b048653/ihyt_a_1068957_f0001_c.jpg)
Table 1. Material properties of model domainsa.
Figure 2. Evolution of the compact probe-fed patch antenna inside a metal enclosure. (A) Rectangular patch, (B) folded C-type patch and, (C) C-type folded patch with shorting post near the feed.
![Figure 2. Evolution of the compact probe-fed patch antenna inside a metal enclosure. (A) Rectangular patch, (B) folded C-type patch and, (C) C-type folded patch with shorting post near the feed.](/cms/asset/81ed8f38-18dc-4b12-b33e-2310907cbbce/ihyt_a_1068957_f0002_c.jpg)
Table 2. Sweep range for the design parameters of cavity-backed rectangular patch ().
Figure 4. Influence of the design parameters of the cavity-backed rectangular patch namely, (A) patch length (L), (B) height (h.) and (C) width (W) on return loss . (D) Return loss of the optimised cavity-backed patch with S11 = −17.31 dB at 434 MHz satisfying the design criteria (L = 28.5 mm, h = 10 mm, W = 3 mm).
![Figure 4. Influence of the design parameters of the cavity-backed rectangular patch namely, (A) patch length (L), (B) height (h.) and (C) width (W) on return loss . (D) Return loss of the optimised cavity-backed patch with S11 = −17.31 dB at 434 MHz satisfying the design criteria (L = 28.5 mm, h = 10 mm, W = 3 mm).](/cms/asset/21ecf103-45b4-4564-a3aa-e16e202bf157/ihyt_a_1068957_f0004_b.jpg)
Figure 5. Simulation results of the cavity-backed folded C-type patch of . Influence of the folded patch lengths namely, (A) the first (L) and (B) second arms (L1) on antenna return loss ; (C) return loss for the optimised C-type patch (L = 26 mm, L1 = 26 mm, h = 10 mm, W = 3 mm, S = 3 mm), and (D) normalised electric field
at 434 MHz in the antenna near field.
![Figure 5. Simulation results of the cavity-backed folded C-type patch of Figure 2(B). Influence of the folded patch lengths namely, (A) the first (L) and (B) second arms (L1) on antenna return loss ; (C) return loss for the optimised C-type patch (L = 26 mm, L1 = 26 mm, h = 10 mm, W = 3 mm, S = 3 mm), and (D) normalised electric field at 434 MHz in the antenna near field.](/cms/asset/d61ce249-b241-4cdf-be06-e7d2786ea087/ihyt_a_1068957_f0005_b.jpg)
Figure 6. Simulation results of the miniaturised patch with metal enclosure, folded C-type arm and shorting post near the feed. Influence of the lengths of the (A) first (L) and(B) second arms (L1) on antenna return loss ; (C) influence of the spacing between shorting post and feed Δx = 16 mm and (D) return loss of the optimised patch (L = 20 mm, L1 = 22 mm, h = 10 mm, W = 3 mm, S = 3 mm).
![Figure 6. Simulation results of the miniaturised patch with metal enclosure, folded C-type arm and shorting post near the feed. Influence of the lengths of the (A) first (L) and(B) second arms (L1) on antenna return loss ; (C) influence of the spacing between shorting post and feed Δx = 16 mm and (D) return loss of the optimised patch (L = 20 mm, L1 = 22 mm, h = 10 mm, W = 3 mm, S = 3 mm).](/cms/asset/417d8199-f8e4-473c-9477-d822845ca7f4/ihyt_a_1068957_f0006_b.jpg)
Figure 7. Orientation of induced current density on the patch surface for the optimised (A) cavity-backed rectangular patch, (B) C-type cavity-backed patch without shorting post, (C) with shorting post; (D) orientation of electric field vector radiated by the miniaturised cavity-backed folded C-type patch with shorting post in the antenna near-field.
![Figure 7. Orientation of induced current density on the patch surface for the optimised (A) cavity-backed rectangular patch, (B) C-type cavity-backed patch without shorting post, (C) with shorting post; (D) orientation of electric field vector radiated by the miniaturised cavity-backed folded C-type patch with shorting post in the antenna near-field.](/cms/asset/b4fd5f54-a09c-4252-9cac-6f07904493b5/ihyt_a_1068957_f0007_c.jpg)
Figure 8. Prototypes of the miniaturised antenna for microwave hyperthermia. (A) C-type folded patch with a shorting post near the feed inside a metal cavity; (B) prototype 1 with flexible 0.3 mm thick PVC water bolus; (C) prototype 2 with rigid side wall to maintain constant bolus thickness and a flexible PVC film at the skin-contacting side.
![Figure 8. Prototypes of the miniaturised antenna for microwave hyperthermia. (A) C-type folded patch with a shorting post near the feed inside a metal cavity; (B) prototype 1 with flexible 0.3 mm thick PVC water bolus; (C) prototype 2 with rigid side wall to maintain constant bolus thickness and a flexible PVC film at the skin-contacting side.](/cms/asset/bfe12407-6917-41d1-b1a0-978942e1dd9f/ihyt_a_1068957_f0008_c.jpg)
Figure 9. Comparison between return loss measurements of the fabricated miniaturised patch and simulation. Return loss measurements of (A) prototype 1 with flexible water bolus for polyacrylamide phantom, and (B) prototype 2 with fixed water bolus height (h1) and plastic outer shell for no load, poly acrylamide and gelatin phantoms.
![Figure 9. Comparison between return loss measurements of the fabricated miniaturised patch and simulation. Return loss measurements of (A) prototype 1 with flexible water bolus for polyacrylamide phantom, and (B) prototype 2 with fixed water bolus height (h1) and plastic outer shell for no load, poly acrylamide and gelatin phantoms.](/cms/asset/8efd5a59-24b0-435b-98d4-dc5bfa1f0e04/ihyt_a_1068957_f0009_b.jpg)
Figure 10. Normalised SAR along the depth of muscle phantoms (XZ plane) for varying pulse duration, Δt. SAR measurements of polyacrylamide gel phantom for (A) 45 s, (B) 60 s and (C) 90 s, (D) simulation results for muscle tissue, (E) normalised SAR of gelatin phantom for Δt = 60 s, (F) comparison of measured and simulated SAR depth profiles.
![Figure 10. Normalised SAR along the depth of muscle phantoms (XZ plane) for varying pulse duration, Δt. SAR measurements of polyacrylamide gel phantom for (A) 45 s, (B) 60 s and (C) 90 s, (D) simulation results for muscle tissue, (E) normalised SAR of gelatin phantom for Δt = 60 s, (F) comparison of measured and simulated SAR depth profiles.](/cms/asset/4e40f901-a12f-4d88-96b4-f61ee438f616/ihyt_a_1068957_f0010_b.jpg)
Figure 11. Normalised SAR at a given depth in muscle phantoms (XY plane). SAR at 5 mm depth for (A) polyacrylamide gel phantom, Δt = 60 s and, (B) simulation result; (C) comparison between measured and simulated SAR profiles along y = 0 mm. SAR surface distribution at 20 mm depth for (D) gelatin phantom, Δt = 60 s, (E) simulation result for muscle tissue, (F) comparison between measured and simulated SAR profiles along y = 0 mm. The dotted black line indicates the outer circumference of the metal cavity (56 mm diameter with 8 mm wall thickness).
![Figure 11. Normalised SAR at a given depth in muscle phantoms (XY plane). SAR at 5 mm depth for (A) polyacrylamide gel phantom, Δt = 60 s and, (B) simulation result; (C) comparison between measured and simulated SAR profiles along y = 0 mm. SAR surface distribution at 20 mm depth for (D) gelatin phantom, Δt = 60 s, (E) simulation result for muscle tissue, (F) comparison between measured and simulated SAR profiles along y = 0 mm. The dotted black line indicates the outer circumference of the metal cavity (56 mm diameter with 8 mm wall thickness).](/cms/asset/f0d98faf-3885-460d-9fa8-539e247182e8/ihyt_a_1068957_f0011_b.jpg)