Information entropy-based design principles for virtual wideband LPI signals against superheterodyne digital receivers

The superheterodyne digital receiver (SDR) is the main equipment for frequency guidance in modern digital radio frequency memory (DRFM) jamming devices. Low-interception signals can significantly reduce the frequency guidance effectiveness of SDR. Nevertheless, at present, the design principle of anti-SDR low-interception signals is still unclear, which severely restricts the quality of the design of low-interception signals. This paper reveals the mechanism of SDR signal interception and frequency scanning failure. Then, the calculation formula for the critical bandwidth required to achieve low interception of signals by the radio detector is derived. Finally, the design principle of multi-frequency group virtual broadband low-interception signals is proposed. Aiming at the limited frequency band and computing resources of a radio detector, based on the proposed principles, in typical cases (i.e., \(\alpha =0.8, \beta =0.2, {B}_{total}=3\text{G}\text{H}\text{z}, {B}_{J}=1\text{G}\text{H}\text{z}\) ), the total bandwidth is divided into four frequency groups and evenly spaced to synthesize virtual broadband. The synthetic virtual broadband can cause the failure of SDR frequency scanning. The simulation results show that the interception probability of the signal designed by the signal design principle proposed in this paper is less than 20%. The signal interception experiment shows that the success rate of signal low-interception design is 78.7%. The simulation and experimental results verify the correctness of the signal design principles and provided theoretical support for designing low‑probability‑of‑intercept (LPI) signals.