RF Electronics Chapter 6: Oscillators Page 180
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
the oscillation frequency and set the secondary parameter VpMax to 8V, since the
oscillating waveform at the base of the transistor will be less than 8Vp. The APLAC HB
(Harmonic Balance) simulator, allows the oscillation frequency, output power, output
waveforms, and output spectrum to be determined. The frequency Fo can now be tuned,
to ensure the circuit oscillates at the 100 MHz. This requires changing Fo to 102.62 MHz
in the equations shown in figure 6.10, and also gives minor changes to Cr and Lc.
If desired, Zrc, the impedance of the inductor at the resonating frequency, and Kc, which
is related to the ratio of Cr1 and Cr2, or the biasing resistors Rb1, Rb2 and the emitter
resistor Rec, can be tuned to provide lower harmonics, a larger output voltage or a lower
phase noise. Equations are used in the Global Definitions block, to ensure that both the
linear and non-linear circuit keep identical circuit elements. For figures 6.10, the blue
(tuneable) variables have been tuned to achieve the phase noise shown in figure 6.13.
That results in a close to 10Vpp output voltage and noticeable harmonic components. At
this stage the characteristic impedance of the resonator, Zrc is kept constant. Figure 6.11
shows the resulting output spectrum of the oscillator and figure 6.12 shows the resulting
output waveform.
Figure 6.11. Output spectrum determined by non-linear analysis.
Figure 6.12. Output waveform determined by non-linear analysis.
RF Electronics: Design and Simulation
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