Define Jammer-to-Signal Ratio (JSR) and its significance.

• A. JSR is the ratio of the target signal power to jammer power at the receiver; higher JSR indicates improved reception.
• B. JSR is the ratio of jammer power to the target signal power at the receiver; higher JSR indicates greater potential degradation of reception.
• C. JSR measures the time delay between jammer and target signals.
• D. JSR is a measure of how many jammers are present.

Answer: (B)

Jammer-to-Signal Ratio shows how strong the jammer is compared with the desired signal as it arrives at the receiver. It is defined as the jammer power divided by the target signal power at the receiver. A higher JSR means the jammer’s power dominates the received contents, reducing the signal-to-interference ratio and making demodulation or decoding harder, which increases the potential for degradation or outages. Conversely, a low JSR indicates the intended signal is stronger than the jamming, allowing the receiver to maintain performance. This metric is essential for assessing vulnerability to jamming and for guiding link-budget planning and countermeasure design, since it reflects how much interference a system must tolerate given factors like distance, antenna gains, and bandwidth. JSR can be expressed in linear terms or in decibels as 10 log10(P_j / P_s).