This chapter considers a variety of functionalities that are typically assigned to distinctly different devices, each designed separately and each requiring its own power supply, analog front end (AFE), physical space, spectral allocation, and computational processing power. Specifically, these devices comprise a radar-based sensor, a data communication transceiver, and a radio frequency (RF) position/navigation system. The rationale behind this “division of labor” is well understood. Certain types of waveforms are simply better suited to particular tasks. For example, linear frequency modulation (LFM) chirp signals are a veritable radar staple, while a variety of keying modulation formats are used for communications. There is an obvious redundancy in this approach; a redundancy that often leads to a critical increase in power consumption, spectral overcrowding, instrument weight and size, and demands upon computing resources. When combined, these increases may represent a formidable challenge especially when these systems are designed for autonomous, long-endurance platforms such as unmanned (aerial, ground, underwater) vehicles. Consequently, instead of choosing system parameters that are best suited to each function, it is worth investigating a prospective compromise solution that allows for a combination of these functions via judicious signal design. A uniting factor throughout this chapter is thus the signal and system architecture format that enables the fusion of the aforementioned functionalities. We explore this potential via the orthogonal frequency division multiplexing (OFDM) software-defined radar system (SDRS) concept.

Chapter Contents:

• 9.1 Overview of OFDM in radar and communications
• 9.2 Design of an UWB software-defined system based on OFDM
• 9.2.1 General considerations for an UWB SDRS design
• 9.2.2 Transmit power considerations for indoor UWB OFDM SDRS
• 9.3 Dual use of system bandwidth and transmit power via OFDM radar/communication signals
• 9.3.1 Radar-embedded communications and radar/communication signals
• 9.3.2 Example: OOK OFDM signal performance in radar and communications
• 9.3.2.1 AF and PSL of UWB OOK-like OFDM radar signals
• 9.3.2.2 BER of UWB OOK-like OFDM communication signals
• 9.4 Simultaneous sensing and covert, ad-hoc asynchronous communications with OFDM
• 9.4.1 Randomization of radar/communication signals for communications
• 9.4.2 Randomization of radar/communication signals using stochastic sequences
• 9.4.3 Cross-range compression for SAR with randomized OFDM signals
• 9.5 In-band co-existence of UWB OFDM radar signals and navigation satellite signals
• 9.5.1 System and simulation setup for UWB radar and GPS receiver co-design
• 9.5.2 GPS software receiver model
• 9.5.3 UWB OFDM and GPS coexistence modeling results
• 9.6 Looking ahead: conclusions and perspectives
• References

Inspec keywords: frequency modulation; radio transceivers; data communication; OFDM modulation; Global Positioning System; software radio; sensor fusion

Other keywords: AFE; data communication transceiver; SDRS; radio frequency position-navigation system; power supply; OFDM; instrument weight; LFM; radar sensing fusion; analog front end; software-defined OFDM architecture; power consumption; spectral allocation; judicious signal design; system architecture; software-defined radar system; keying modulation formats; veritable radar staple; computational processing power; GPS interoperability; uniting factor; system parameters; spectral overcrowding; physical space; linear frequency modulation chirp signals; RF position-navigation system; orthogonal frequency division multiplexing

Subjects: Modulation and coding methods; Sensing devices and transducers; Radionavigation and direction finding