The design of analog front-ends of digital telecommunication transceivers requires simulations at the architectural level. The nonlinear nature of the analog front-end blocks is a complication for their modeling at the architectural level, especially when the nonlinear behavior is frequency dependent. This paper describes a method to derive a bottom-up model of nonlinear analog continuous-time circuits used in communication systems. The models take into account frequency dependence of the nonlinear behavior, making them suitable for wideband applications. Such model consists of a block diagram that corresponds to the most important contributions to the second- and third-order Volterra kernels of the output quantity (voltage or current) of a circuit. The examples in this paper, a high-level model of a CMOS low-noise amplifier and an active low-pass filter, demonstrate that the generated models can be efficiently evaluated in high-level dataflow-type simulations of mixed-signal front-ends and that they yield insight in the nonlinear behavior of the analog front-end blocks.