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Nonlinear Microwave Circuit Design phần 5

Rõ ràng, các mạch trước khi kết hợp phải được đặc trưng về thông số S và thay thế bằng những người thân khác nhau bất cứ khi nào khu vực thiết lập cho vô hướng điển hình, thụ động nguồn / tải kéo với kiểm soát cá nhân của trở kháng hòa Chuyển đổi đạt được là tương tự như đối với nhân đôi duy nhất kết thúc, và công suất đầu ra cao hơn | 148 NONLINEAR MODELS Figure 3.66 Perturbed drain current and voltage around a large-signal state for a high-efficiency power amplifier perturbed by several small fifth-harmonic waves in the time domain. In the complex plane of the waves a and b the waves are represented by vectors the perturbed waves are therefore represented as constant vectors the unperturbed wave to which small perturbing vectors waves are added. For better accuracy of the measurement many perturbing waves a with the same amplitude but different phases are used describing thus a circle around the unperturbed wave a 0 . The perturbed wave vector b correspondingly describes an ellipse around the unperturbed vector b 0 because of the non-analytic nature of eq. 3.97 Figure 3.66 . The nonlinear scattering parameters find application for example when the stability of the large-signal state must be verified or ensured or when the condition of large-signal match is required. 3.5 SIMPLIFIED MODELS In this paragraph simplified models are described together with some hints on their main applications. So far accuracy has been one of the main desirable features of the described models. In this paragraph we will describe models that are intentionally not very accurate but that allow for substantial advantages from other points of view. In fact an accurate model requires an equally accurate nonlinear analysis algorithm even considering that SIMPLIFIED MODELS 149 the limiting factor of the simulation accuracy for the current state of nonlinear CAD is the model itself. However an accurate analysis algorithm is a numerical algorithm that in itself does not allow a proper insight into the behaviour of the device or circuit. The data are fed into the computer and the results come out. Of course optimisation is very useful for improving the performances of a circuit however numerical problems sometimes do not allow the optimisation algorithm to find the optimum values. Moreover the definition of a single .