Caption: FIGURE 11: (a) Type I SHG
tuning curve of LGT.
Inspecting [f.sub.L] expressed in Equation (2), when [C.sub.1] of the primary LC tank incorporates tuning varactors, there is a two-dimensional
tuning curve (frequency versus vtune or versus [C.sub.1]) as traditional VCO designs in literature.
The current flow through varactors [C.sub.var2], [C.sub.var4] and [C.sub.var6] are used to establish the unidirectional phases (A, B, C) by utilizing the monotonic
tuning curve of accumulation-mode MOS varactor.
The plot depicts the
tuning curve and represents the "receptive field" of the nerve from which the data were obtained.
In general, today's systems demand the largest possible frequency range, the lowest possible phase noise, a linear
tuning curve and insensitivity to load conditions.
This can be accomplished by varying the sweep rate (or shape of the
tuning curve) in some random way, but it is much easier to implement a scheme in which the start time of the sweep is pseudo-randomly selected.
The boundaries of each frequency
tuning curve were defined as the stimuli (intensity and frequency) that yielded these evoked, excitatory responses [22, 26].
A high SWR or unstable load not only causes VCO frequency pulling, but will also sometimes produce rapidly accelerated regions of the
tuning curve (voltage-to-frequency transfer function).
As shown in Equation 4, [[omega].sub.0](V) is a nonlinear function of V, and therefore, in general, the
tuning curve will not be a perfectly straight line.
The VCO's typical
tuning curve over temperature is shown in Figure 2.
In addition, using a varactor with a less abrupt
tuning curve reduces the tuning diode's nonlinearity.
Since the upper part of the
tuning curve is much more nonlinear than the lower part, six switching points are used in the upper part (resistors R+) and only two switching points are used in the lower part (resistors R-).