Chaos Based Frequency Modulation for Joint Monostatic and Bistatic Radar-Communication Systems

Abstract

In this article, we propose the utilization of chaos-based frequency modulated (CBFM) waveforms for joint monostatic and bistatic radar-communication systems. Short-duration pulses generated via chaotic oscillators are used for wideband radar imaging, while information is embedded in the pulses using chaos shift keying (CSK). A self-synchronization technique for chaotic systems decodes the information at the communication receiver and reconstructs the transmitted waveform at the bistatic radar receiver. Using a nonlinear detection scheme, we show that the CBFM waveforms closely follow the theoretical bit-error rate (BER) associated with bipolar phase-shift keying (BPSK). We utilize the same nonlinear detection scheme to optimize the target detection at the bistatic radar receiver. The ambiguity function for both the monostatic and bistatic cases resembles a thumbtack ambiguity function with a pseudo-random sidelobe distribution. Furthermore, we characterize the high-resolution imaging capability of the CBFM waveforms in the presence of noise and considering a complex target.

Synchronization of Monostatic Radar Using a Time-Delayed Chaos-Based FM Waveform

“…They also operate at low frequencies (below 3 MHz), and therefore they suffer from diffraction due to the surface of the earth. Longwave bands in HF band MHz employ Skywave (shortwave), where the short wave depends on the ionosphere [2,[4][5][6][7][8][9]14].…”

“…Each radar system depends on the type of waveform, whether continuous or non-continuous (i.e., pulse wave) [2]. The radar is called monostatic radar if the transmitter and receiver are placed in the same place; otherwise, the radar is a bistatic or multistatic type if both transmitter and receiver(s) are separately located over a distance [4]. Figure 1 depicts the three types of radar systems.…”

“…Another issue in chaotic based radar systems (CBRS) is choosing the type of chaos synchronization between the transmitter and the receiver nodes. Conversely, traditional synchronization schemes such as Phase-Locked Loop (PLL) can be used in chaotic radars [4]. In fact, there are many studies on complete synchronization and feedback control [7,8] in a radar system, but the limitation is raised due to its sensitivity to noise, and any tiny amounts of additive noise to the (echo) signal can degrade the synchronization quality, and the chaotic signals may not be synchronized [11].…”

“…In fact, there are many studies on complete synchronization and feedback control [7,8] in a radar system, but the limitation is raised due to its sensitivity to noise, and any tiny amounts of additive noise to the (echo) signal can degrade the synchronization quality, and the chaotic signals may not be synchronized [11]. Moreover, some CBRS systems have been widely studied, either with no modulation, such as pulse compression, or within a variety of modulation methods, such as continuous AM/FM/PM modulation where many CBRSs are utilized in microwave and UWB and laser applications [4,12,13]. One example was devoted to a microwave chaos signal practically generated through the Colpitts oscillator and directly transmitted through a wide-band antenna without modulation [7,8].…”

“…To the best of our knowledge, some studies [17,18] are only concerned with the coupled systems without time delay in the presence of parameters mismatch. Other significant reports have also been devoted on the adaptive-observer synchronization schemes to solve this problem using different time-delay chaotic systems [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Among these, Liu et al [16], He et al [19] and Huang et al [20] have discussed some approaches on synchronization of two coupled delayed systems with parameters mismatch under particular certain coupling strength for the delayed Lur'e systems.…”