1] of the primary LC tank incorporates tuning varactors, there is a two-dimensional tuning curve
(frequency versus vtune or versus [C.
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.
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).
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-).
The typical tuning curve
of the model CLV1320E VCO is shown in Figure 4.
Likewise, the oscillation frequency can be determined and the oscillator tuning curve
can be predicted.
The theoretical tuning curve
obtained from a circuit model agrees well with experimental results.
In the past, this parameter was not within the control of the design engineer, which meant working around whatever tuning curve
was the closest to the desired design.