tailieunhanh - Nonlinear Microwave Circuit Design phần 9

Một nhân đôi tần số có thể tận dụng lợi thế từ một cấu hình cân bằng [31, 50-58]. Hai giống nhau duy nhất kết thúc doublers đuổi ra khỏi giai đoạn của một coupler ◦ 180, và kết quả đầu ra của họ được kết hợp trong giai đoạn, ví dụ, một ngã ba đơn giản (Hình 6,32). Các tín hiệu tần số cơ bản | 308 FREQUENCY MULTIPLIERS AND DIVIDERS Figure A balanced frequency doubler 0 A frequency doubler can take advantage from a balanced configuration 31 50-58 . Two identical single-ended doublers are driven out of phase by a 180 coupler and their outputs are combined in-phase for example by a simple T-junction Figure . The fundamental-frequency signal and all the odd-order harmonics are 180 out-ofphase at the output and therefore cancel the second-harmonic signal and all even-order harmonics are in-phase at the output and combine. Such an arrangement therefore ensures intrinsic isolation between input and output without the need for filters. Conversion gain is the same as for the single-ended doubler and the output power is 3 dB higher provided that a correspondingly higher input power is supplied no matching improvement is obtained. FREQUENCY DIVIDERS - THE REGENERATIVE PASSIVE APPROACH In this paragraph the operating principle of regenerative frequency dividers are described together with a stability analysis. Frequency dividers can be classified into two main types regenerative dividers where the power is converted from the fundamental-frequency input signal to the fractional-frequency signal by a passive nonlinear device and oscillating dividers where an oscillator at the fractional frequency is phase locked by the input signal at fundamental frequency corresponding to a harmonic frequency of the oscillator. The latter type is treated in Chapter 8 together with other injection-locked circuits while the former type is described hereafter. The general structure of a regenerative frequency divider is shown in Figure in which a frequency divider-by-two is shown 59-61 . The input pumping signal is fed to a nonlinear device usually a reverse-biased diode where frequency conversion takes place. An input filter prevents the frequency-converted signal to bounce back towards the signal source while an output filter prevents the input signal to reach the .