Lecture #5 - Non-Linear Devices Flashcards
Give an example of a linear and non-linear device
Linear; Resistor
Non-linear; diode
A general nonlinear device can be modelled through a TS; what is the equation and what’s the significance of which the coefficient holds dominance
When is nonlinearity desirable and not desirable?
What is the characteristics of the practical equation for gain
- The gain is less than an ideal amplifier.
- There’s a dependance on V_0
What does the spectrum look like for an ideal amplifier
A straight line centred around f_0
For a real amplifier, what happens to the output power
The actual power drops by 1db; which is called the 1db compression point.
What happens when a single sinusoid (one tone) of frequency w_o is input into a non-linear device.
Its output signal consists of multiple frequencies
Are harmonics desired or undesired in a device?
It depends; undesired in an amplifier, good for frequency multiplier or sub-harmonic mixer.
What is the noise floor?
It’s the amount of noise that the frequency signal (RF) must be stronger to be detected.
A higher noise floor indicates a lower sensitivity within the system.
What is the fundamental tone?
What are the intermodulation products
The addition and reduction of sinusoid tones in the frequency
In a signal, what are we only interested in amplifying?
cosw_1t
What happens when a bass pand filter can’t filter out the third-order intermodulation products
- This leaks into the different
What is the IP3 or the TOI value
Why do we need an IP3, if it’s hypothetical?
The IP3 value indicates how large of a signal the amplifier can process before Intromodulation Distortion (IMD) occurs.
A high IP3 value implies that the device has good linearity, whereas, a low IP3 value means the intermodulation products could interfere with the fundamental signal.
Explain the practical measurement of the IP3 point.
Are intermodulation products deterministic or stochastic?
Deterministic
In the output IP3 point of a three stage cascaded system, what happens when one one of the OIP3 values are low?
This dominates the value
What happens when of the the OIP3 values is out of phase?
It lowers the overall OPI3 value
The IP3 point is usually given in terms of what?
In terms of the higher power.
Amplifier OIP3
Mixer IP3
Explain the relationship between noise and OIP3
An ideal Rx requires the lowest NF and the highest OIP3, but these requirements are often contradictory and a trade-off is needed in a system design.
Which is more important IP2 or IP3?
IP3 and in general odd-order IMD are closer to the fundamental tones, hence they are of a bigger concern in components whose desired output has the same frequency as its input
Give a layman’s example of Desensitization
If you’re listening to somebody, but there is one person shouting in your ear and the other person is whispering.
Person who is whispering is your desired signal. The person who is shouting is the interrupted signal.
That is essentially Desensitization.
