Home of RF and Wireless Vendors and Resources

One Stop For Your RF and Wireless Need

SSB vs VSB | Difference between SSB and VSB modulation types

This page on SSB modulation vs VSB modulation describes difference between SSB and VSB modulation types.It provides link to DSBSC vs SSBSC.

Before we start our discussion, it is recommended to understand concept of DSB-SC vs SSB-SC which mentions difference between DSB-SC and SSB-SC modulation types. In DSB-SC signal, there is symmetry in band structure. Due to this fact even if one half is transmitted, the other half can be recovered at the receiver. Due to this, bandwidth and power of transmission is reduced by half. Depending upon which half of DSB-SC is transmitted there are two types of SSB modulation viz. LSB (Lower Side Band) modulation and USB (Upper Side Band) modulation. The same have been depicted in figure-2 below.

SSB Modulation

SSB signal generation

As shown in figure-1, DSB-SC modulator is used for SSB signal generation. It is mathematically represented as below.
= m(t)*cos(Wc*t) +/- m^(t)*sin(Wc*t)

Original signal is retrieved using coherent demodulation of SSB signals. φSSB(t) is multiplied with cos(Wc*t) and passed through low pass filter to get back the original signal.

φSSB(t) * cos(Wc*t) = 1/2 m(t) + 1/2 cos(2*Wc*t) +/- 1/2 m^(t)*sin(2*Wc*t)
The demodulated signal is passed through an LPF to remove unwanted SSB.

VSB Modulation

SSB modulation vs VSB modulation

Following are the drawbacks of SSB signal generation:
-Generation of SSB signal is difficult.
-Selective filtering is done to get back the original signal.
-Phase shifter should be of 90 degree exactly.

To overcome all these drawbacks of SSB modulation, VSB modulation is used. Hence VSB is considered as a compromise between SSB and DSB-SC.

In VSB modulation :
•  One sideband is not rejected fully.
•  One sideband is transmitted fully and a small part (i.e. vestige) of the other sideband is transmitted. Hence bandwidth here is BWv = B + v, where v is vestigial frequency band.

VSB signal generation

Figure-3 depicts VSB signal generation. Hi(w) is a filter which shapes the other sideband.
φVSB(w) = [ M(w-wc) + M(w+wc)]. Hi(w)

To recover the original baseband signal from the VSB signal, the VSB signal is multiplied with cos(Wc*t) and passed through an Low Pass Filter(LPF). Doing so, original signal is recovered.

Modulation types related links

AM vs FM vs PM  ASK vs FSK vs PSK  what is modulation  MSK and GMSK modulation  8-PSK modulation  QPSK modulation  BPSK modulation  QAM modulation  C4FM vs CQPSK

What is difference between

Refer QPSK vs OQPSK vs pi/4QPSK for difference between QPSK, OQPSK and pi/4QPSK modulation types
difference between OFDM and OFDMA
Difference between SC-FDMA and OFDM
Difference between SISO and MIMO
Difference between TDD and FDD

RF and Wireless tutorials

WLAN  802.11ac  802.11ad  wimax  Zigbee  z-wave  GSM  LTE  UMTS  Bluetooth  UWB  IoT  satellite  Antenna  RADAR 

RF and Wireless Terminologies

Share this page

Translate this page