#1: Signals & Systems Flashcards
What is the frequency of light + its velocity in a vacuum?
frequency = 10^15 Hz velocity = 3x10^8 m/s
Velocity = ______ x wavelength
frequency
Wavelength = _____ / frequency
velocity
UHF = ____ High Frequency = 300_Hz - 3__Hz What sort of devices use this frequency spectrum?
Ultra (High Frequency) 300MHz - 3GHz Wireless LANs, modern TVs, high end 2-way radios, mobile phones
What frequency band + spectrum is FM radio?
VHF (Very High Frequency) 30 - 300MHz
Define a ‘signal’.
An amplitude that varies with time
Express radians in terms of frequency
w = 2*pi*f
Frequency is the ____ of _____.
Rate ; change
What is a radio signal (in terms of actual energy reaching its destination?)
Electromagnetic waves travelling through air or free space - cables not required!
Describe the steps in calculating the RMS value of a signal
1) square the signal 2) find the average of the area under the signal (e.g. integrate over a period) 3) square-root this answer (undo step 1)
What would the RMS of x(t) equal?
x(t) / sqrt(2)
What is a decibel, and what is it used for?
A tenth of a bell.
It illustrates the power of a signal or gain of a system via a logarithmic scale.
Why do we use a logarithmic scale?
Human hearing is based off a logarithmic scale.
Big numbers are easier to deal with on a log scale.
Any resistive component above 0°C emits ____ ____.
thermal noise
Using log rules, re-write:
y = logb x
by = x
What is ‘SNR’, and what is its use?
Signal to Noise Ratio.
Noise is only useful when comparing it to the signal strength to measure the actual distortion.
State Fouriers Theorem.
A continuous periodic function may be expressed as…
…the sum of a series of sine or cosine terms…
…each of which has specific amplitude and phase coefficients known as ‘Fourier coefficients’.
What does ‘THD’ stand for, and what does it mean?
Total Harmonic Distortion is the measurement of all harmonic components present in a signal.
What does ‘dBm’ mean?
decibell-miliwatts
Indicates a logarithmic expresison with reference to 1 miliwatt
Convert ‘0dBm’ to mW.
0 = 10 log10 PmW
PmW = 100/10
PmW = 1mW
What’s the difference between a higher and lower ordered filter?
A higher ordered filter has a sharper response curve, but is more expensive.
