Expect majority questions from this topic. Study this topic really well, as many theory questions and problems are asked from this. Many questions from microwave is asked which is out of syllabus for gate. Study satellite communication link design and antenna theory also. Questions from topics which we don’t usually find important for GATE can come.
Mainly circuits with BJT and OPAMPS only asked. Also learn Rectifiers with zener diode
Lot of very straight forward questions asked. So brush up everything and study A/D converters which is not that important for gate.
Very few questions are asked, that too straight forward negative feedback question, system response etc. and related to concepts in root locus and other graphical methods
Compared to gate syllabus, this is having lot of advanced topics. Study each and every heading in this. Anything can be asked (mostly direct but expect little tricky questions here). Even questions from coding theory have been asked even though not in GATE syllabus.
This topic you will find difficult to study, as it is not for GATE and from previous year paper it is not easy for pin pointing even the correct syllabus. Many topics electronics students are not studying(mostly computer science people only knows the answers so get their help in finding answers in the previous year papers). Better don’t waste too much time in this. Study only basic concepts in computer networks, computer organization and microprocessor (study if you have done it as part of university syllabus and leave the more advanced topics in this and devote more time on to gate syllabus part)