Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
Basically the front end of a RF transmitter is composed of an Upconversion Mixers/Balanced Modulators, Voltage Controlled Oscillator, Bandpass Filters and Power Amplifiers.
hrkhari is right. The front end also contains the preselector which helps eliminate image frequencies (if we are talking superheterodyne and we most likely are).
The front end conditions the signal. First, most likely, there will be some form of band pass filtering (like the preselector). The signal will be amplified (RF amplifiers) and converted to the proper Intermediate frequency (IF frequency) by using non linear mixing (the balanced modulator or mixer). Basically you tune either over or under the incoming frequency by an amount equal to the IF frequency. This ensures the rest of the receiver can be designed for the IF frequency, which makes design must easier and more pratical (think in terms of mass production). After the non-linear mixing you have to filter to get rid of the unwanted products. For example, take an FM radio:
***Start of Front End***
Preselector in
RF Amplifier to boost the incoming signal
non-linear mix to get the signal down to the IF frequency
Bandpass filter to get rid of the unwanted products
***End of Front End***
Next are the IF amplifiers (which are not part of the front end).
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
