FBR (Front to Back Ratio)

Front to Back Ratio (FBR) is a measurement of the relative strength of an antenna’s signal in the forward direction (i.e., towards the intended receiver) compared to its signal in the opposite direction (i.e., towards unwanted sources). In other words, it is a measure of the antenna’s ability to reject interference from sources behind it.

FBR is typically expressed in decibels (dB), and is calculated by comparing the power of the signal received from the front of the antenna to the power of the signal received from the back of the antenna. A high FBR indicates that the antenna is effective at rejecting unwanted signals from behind it, while a low FBR indicates that the antenna is more susceptible to interference.

There are several factors that can affect an antenna’s FBR, including its physical design, the materials used in its construction, and the frequency range over which it is intended to operate.

One of the most common designs for achieving high FBR is the use of a “Yagi” or “beam” antenna. These antennas are directional, meaning that they are designed to focus their energy in a particular direction while minimizing radiation in other directions. By carefully designing the shape and orientation of the antenna’s elements (i.e., the metal rods or wires that make up the antenna), it is possible to achieve a high level of directivity and, therefore, a high FBR.

Another common design for high FBR is the “parabolic” or “dish” antenna. These antennas use a curved reflector (usually made of metal or fiberglass) to focus the incoming signal onto a single point (the “feed” or “hot spot”) where the receiver is located. By carefully shaping the reflector and positioning the feed at its focal point, it is possible to achieve very high levels of directivity and, therefore, very high FBR.

In addition to physical design, the materials used in an antenna’s construction can also affect its FBR. For example, some materials are more effective at reflecting or absorbing unwanted signals than others. Likewise, the choice of materials can affect the antenna’s durability, weight, and cost.

The frequency range over which an antenna is intended to operate is another important factor in determining its FBR. Different antenna designs are optimized for different frequency ranges, and the choice of frequency range can have a significant impact on the antenna’s performance. For example, antennas designed for lower frequencies (e.g., AM radio) are typically larger and less directional than those designed for higher frequencies (e.g., microwave).

There are several methods for measuring an antenna’s FBR, including laboratory testing and field testing. Laboratory testing typically involves placing the antenna in a controlled environment (e.g., an anechoic chamber) and measuring the strength of the signal received from various angles. Field testing, on the other hand, involves measuring the strength of the signal received by the antenna in real-world conditions (e.g., on a rooftop or in a mobile vehicle).

In conclusion, Front to Back Ratio (FBR) is an important measure of an antenna’s ability to reject unwanted signals from behind it. The FBR is typically expressed in decibels (dB) and is calculated by comparing the power of the signal received from the front of the antenna to the power of the signal received from the back of the antenna. There are several factors that can affect an antenna’s FBR, including its physical design, the materials used in its construction, and the frequency range over which it is intended to operate. Achieving high FBR requires careful attention to these factors, and the choice of antenna design will depend on the specific application and operating environment.