# Design oscillator with linear small S parameters

• baby_1
In summary, designing an oscillator with linear small S parameters involves selecting the desired frequency, active device, and designing the negative feedback network. S parameters are used to characterize the small signal behavior and determine the stability and performance of the circuit. Improving linearity can be achieved through using high-quality components and proper grounding and shielding techniques. Non-linear S parameters cannot be used in oscillator design, as the circuit operates in the linear region.
baby_1
Hello
I have a question about design oscillator with linear small S parameters.If you assume I use a Common emitter configuration and put my resonator at input port (Base/Emitter). After I select a Gama(G) in unstable region in input smith chart plane(for example Gama(G)=A<B (for example A=1)) and I map it into Gama(L) plane it is necessary that Gama(L) should be in unstable output region or only |Gama(L)| should be more than unity?
what is the best design ( |Gama(L)|>1 and be in unstable region or |Gama(L)|>1 and be in stable region )?
Thanks

for your helpThe best design would be to choose a gamma(G) in the unstable region of the input smith chart plane, and then map it to a gamma(L) in the unstable region of the output smith chart plane. This ensures that the oscillator is operating in an unstable region and will generate an oscillating signal. A gamma(L) with a magnitude greater than 1 is also necessary, as this indicates that the oscillator is oscillating at the desired frequency.

## 1. How do I design an oscillator with linear small S parameters?

To design an oscillator with linear small S parameters, you will need to follow these steps:
1. Choose the desired frequency of oscillation
2. Select an appropriate active device (e.g. transistor, FET)
3. Design the negative feedback network using passive components (e.g. resistors, capacitors)
4. Simulate the circuit using a software tool or perform a hand calculation to ensure the small signal gain and phase shift meet the Barkhausen criteria for oscillation
5. Test and tune the circuit to achieve the desired oscillation frequency and stability.

## 2. What are S parameters in oscillator design?

S parameters, also known as scattering parameters, are a set of parameters that describe the relationship between the input and output signals of a linear electrical network. In oscillator design, S parameters are used to characterize the small signal behavior of active devices (e.g. transistors) and passive components (e.g. capacitors, inductors) in the feedback network. These parameters are crucial in determining the stability and performance of an oscillator circuit.

## 3. What is the significance of linear small S parameters in oscillator design?

In oscillator design, it is important to ensure that the small signal gain and phase shift of the circuit meet the Barkhausen criteria for oscillation. The linear small S parameters help in analyzing the stability and performance of the circuit in this regard. By using these parameters, one can determine the frequency of oscillation, the amount of feedback needed, and the stability of the oscillator circuit.

## 4. How can I improve the linearity of small S parameters in an oscillator circuit?

In order to improve the linearity of small S parameters in an oscillator circuit, you can use high-quality components with low parasitics, such as low-noise transistors and high-Q capacitors. Additionally, proper grounding and shielding techniques can also help in reducing unwanted parasitic effects and improving the linearity of the circuit.

## 5. Can I use non-linear S parameters in oscillator design?

No, non-linear S parameters cannot be used in oscillator design. This is because non-linear S parameters are not constant and depend on the amplitude of the input signal. In oscillator design, the circuit operates in the linear region, and thus, only linear small S parameters can accurately predict the behavior of the circuit. Non-linear S parameters are typically used in the design of amplifiers and mixers.

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