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FREQUENCY  BANDS

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DOPPLER FREQUENCY SHIFT

 

Doppler shift is an apparent change in frequency (or wavelength) due to the relative motion of two objects. Either one or both of the objects may be moving with respect to the ground. Radar systems exploit the Doppler shift to provide an indication of relative speed. When the two objects are approaching each other (closing), the Doppler shift causes a shortening of wavelength - or increase in frequency.  When the two objects are receding from each other (opening), the Doppler shift causes a lengthening of wavelength - or decrease in frequency. For a Doppler radar system to measure speed, an accurate sample of the original phase of the transmitted signal must be maintained for comparison against the reflected signal.

Fixed Transmitter with Moving Target
,  where all units must be kept constant (c=speed of light)
Moving Transmitter with Moving Target
,  where all units must be kept constant (c=speed of light)
 
 

FREQUENCY BANDS

 

30
Hz
300
Hz
3
kHz
30
kHz
300
kHz
3
MHz
30
MHz
300
MHz
1
GHz
2
GHz
3
GHz
4
GHz
8
GHz
12.5
GHz
18
GHz
26.5
GHz
30
GHz
40
GHz
300
GHz
 >300
GHz

ELF

                                    
 

VF

 

VLF

 

LF

 

MF

 

HF

 

VHF

 

UHF

 

L-Band

 
 

S-Band

  SHF
  C-Band        
 

X-Band

 

Ku

 

K

 

Ka

 

EHF

 

Millimeter

ELF = Extremely Low Frequency

VF = Voice Frequency

VLF = Very Low Frequency

LF = Low Frequency

MF = Medium Frequency

HF = High Frequency

VHF = Very High Frequency

UHF = Ultra High Frequency

SHF = Super High Frequency

EHF = Extremely High Frequency

 

DTMF FREQUENCIES

 

Dual-Tone, Multiple Frequency tones for touch-tone phones. When a keypad button is depressed, a dual-tone signal is transmitted according to the table below. For example, if the "5" is depressed, then both a 770 Hz tone and a 1336 HZ tone are sent simultaneously. On the receiving end, the tones are discriminated and decoded.
 

  1209 Hz 1336 Hz 1477 Hz 1633 Hz
697 Hz 1 2 3 A
770 Hz 4 5 6 B
852 Hz 7 8 9 C
941 Hz * 0 # D