Matched 429/433 MHz PCB Antenna
Publication Date: 2004-Jun-08
The IP.com Prior Art Database
A matched antenna on a printed circuit board (PCB) can provide for an affordable, easily manufactured and designed PCB-based antenna in the 429 to 433 MHz bands. The matched antenna, which addresses the need for a small antenna based on a single-sided PC board, employs one of several disclosed fractal geometries. By utilizing a smaller area and by moving the feed point to the edge to allow the antenna to accommodate easier circuit design and trace routing, the matched antenna provides improvements over both past and current designs.
Disclosed below is a matched antenna that can be printed in a small (about 1.5” x 1.5” or less) space, such as on a printed circuit board (PCB) and tuned for between 429 to 433 MHz. The PCB antenna is well matched to 50 ohms by design and requires no additional matching components.
Embodiments of the invention address the need for a small (about 1.5” x 1.5” or less) antenna based on a single-sided PC board for use in the 429 MHz to 433 MHz range. The desire was to explore alternatives to a proposed stamped brass antenna with several potential manufacturing issues.
The initial testing of the first prototype of the matched 429/433 MHz PCB antenna showed that the antenna was resonant at around 160 MHz lower than the design goal but that it did produce the proper impedance at the resonant frequency. Pattern tests were conducted and found to be satisfactory enough to continue (see Fig. 1, Fig. 2, and Fig. 3).
Pattern number two (Fig. 7 and Fig. 8) was modeled and found to work well at 433 MHz. When tested on the network analyzer, the resonant frequency was at 330 MHz and 470 MHz. Minor tuning did not change the frequency significantly so the feed point was moved and the circuit trace for the loop was opened to lower the resonant frequency. The modified diagram is shown in Figure 4. Figure 6, which shows the output from the network analyzer, reveals that the new tuning was successful. Figure 6 shows a notch centered at 431 MHz that is over 30 dB dow...