  High implementation complexity of multi-scroll circuit is a bottleneck
problem in real chaos-based communication. Especially, in multi-scroll Chua's
circuit, the simplified implementation of piecewise-linear resistors with
multiple segments is difficult due to their intricate irregular breakpoints and
slopes. To solve the challenge, this paper presents a systematic scheme for
synthesizing a Chua's diode with multi-segment piecewise-linearity, which is
achieved by cascading even-numbered passive nonlinear resistors with
odd-numbered ones via a negative impedance converter. The traditional voltage
mode op-amps are used to implement nonlinear resistors. As no extra DC bias
voltage is employed, the scheme can be implemented by much simpler circuits.
The voltage-current characteristics of the obtained Chua's diode are analyzed
theoretically and verified by numerical simulations. Using the Chua's diode and
a second-order active Sallen-Key high-pass filter, a new inductor-free Chua's
circuit is then constructed to generate multi-scroll chaotic attractors.
Different number of scrolls can be generated by changing the number of passive
nonlinear resistor cells or adjusting two coupling parameters. Besides, the
system can be scaled by using different power supplies, satisfying the
low-voltage low-power requirement of integrated circuit design. The circuit
simulations and hardware experiments both confirmed the feasibility of the
designed system.
