Radio transmitters and receivers are essentially interfaces between digital data (bits) and electromagnetic waves.This can be further divided to front-end processing and baseband processing.
Fig1: Front-end processing and baseband processing diagram
Fig2: Block Digaram of a Transmitter
We can describe front-end section operate frequency translation stages,amplification stages,filtering stages and sampling interface and so on.In the based band DSP and other digital is operated.
Different radio architectures then mean how the above functionalities are organized in the radio chain.
We can see outline a transceiver in up images.Any transceiver has Three stages circuit.
- Base Band
- Intermediate Band
- Radio Band
Base Band:This is the first stage a Transmitter,this stage operate digital signal processing,data analysis and a other feature a digital circuit.
Intermediate Band:In the stage base band data is on LF or HF ,and we want to send data to upper frequency so we need a stage that we transformer data to VHF or UHF or even upper frequency. this stage usually we use mixer in circuit to transformer data to upper frequency.but this transformation yet is not sufficient so this stage is called Intermediate Frequency Band.this section usually is analog.
Radio Band:In the third section is a RF circuit, it can Transform Data to Frequency which we set. this section is analog part.This section we work with Radio Frequency signal in circuit.
So we have defined there type gain in a transceiver.
- BB gain
- IF gain
- RF gain
In gnuradio we have these three gains, in source sdr like osmocomsource or osmocomsink. we now are familiar with gain in a transceiver and other challenge question how we can decide to set value gain in Transceiver.For decition that how we can set parameter gain i create new thread in edaboard. general response is :
The balance between amplification in the stages is quite tricky and depends on what dynamic range and noise figure you want.
More gain especially close to the antenna gives lower noise figure but also degrades dynamic range.
More gain=less dynamic range= intermodulation and false signals.
Less gain= less sensitivity but less false signals.
I hope this post be useful for readers. in other post we write about other fun subjects.
Radio Architectures and Signal Processing,Mikko Valkama & Markku Renfors