Frequency Translation Working and Its Applications

In a communication system, the transmission of an individual message can be done simultaneously above a single communication channel. A technique which uses numerous transmissions is called multiplexing. This includes changing every message to a dissimilar location within the frequency spectrum which is known as frequency multiplexing. This method uses the auxiliary wave from carrier wave which is sinusoidal. The signal processing in the communication system can be frequently convenient to convert the signal from one frequency domain region to another frequency domain region. The frequency translation method is one where the unique signal is changed by an innovative signal whose frequency range expands from f1 to f2.

What is Frequency Translation?

The frequency translation can be defined as; it is one kind of method for transmitting a signal from one fraction of the frequency axis to another fraction of the axis. This is frequently done within the wireless communications system to transmit a passband signal toward baseband previous to demodulation. Compound multipliers are used for performing frequency conversion; however, a more efficient technique is to employ decimation.

Frequency Translation Requirements using Decimation

In DSP (digital signal processing) applications, generally, aliasing can be keep away from all costs. Though, in this application it is the device at work, so care should be taken to generate the preferred result instead of the normal negative results connected with aliasing.

Initially, the signal must be translated to bandpass within nature, which means that the signal of attention should live in a comparatively thin band & all other frequencies should include considerably less energy. But, this necessity is application-specific as there may be applications that execute well, even with an important quantity of aliasing.


The above figure demonstrates a bandpass signal using bandwidth, the frequency which is centered is relatively high contrasted to bandwidth. The signal energy of interest can be much superior to the energy within other frequencies. This condition can be met within one of two modes.

In some cases, the signal will be bandpass within nature to start with; otherwise, the application can call for an indication that can be simply bandpass. In this situation, the decimation may be done instantly. In most of the cases, the bandpass signal requires to be formed using a bandpass filter previous to the decimation process is done.


Next, the signal bandwidth of interest ought to be below the unique sample rate separated by twice the decimation factor. This condition can be sum up in the following equation.

BW < fs/2D

The condition in the above equation guarantees that the last sample rate can be highly sufficient for the interest bandwidth’s signal.

Frequency Translation using PLL

The frequency shifting of an oscillator using a small factor is known as a frequency translator. The block diagram of the frequency translator using PLL is shown below.


The block diagram can be built with a mixer, LPF, and the phase-locked loop. The fs (input frequency which has to be transferred is applied to the mixer. Other i/p of the mixer is the o/p voltage of VCO that is fo. As a result, the o/p of the mixer includes the difference signal and sum (fo ± fs). The LPF which is connected to the mixer’s o/p discards the (fo +fs) signal & provides the signal like (f0 – fs) at the o/p. The signal like (fo – fs) can be applied toward the phase detector. The offset frequency f1 is i/p of the detector. In the locked mode, the o/p frequency of VCO can be regulated to make 2- input frequencies of phase detector equivalent.

This gives,

f0-fs = f1 & f0 = fs +f1

By regulating f1 (offset frequency) can move the oscillator’s frequency to the preferred value.


  • The applications of frequency translation mainly include within the context of the parts like QF4A512 & QF1D512.
  • The interest signal moving is nearer to DC so that the filter’s 512 taps are more efficient.
  • The signal of interest moving under the highest operating frequency of the parts
  • The applications of frequency translation mainly include conversion of frequency up, frequency down, improved signal reception, and combined down change, groupings, etc.

This is all about frequency translation which can be used to transfer a form of signal from one portion of the frequency axis to other one portion of the frequency axis. This translation mainly happens often within a wireless communication system. This translation can be used for transferring the signal from passband to baseband. For this, the most efficient technique is decimation. Here is a question for you, what are the advantages of frequency translation?