FM Radio Repeater Design for Long Range Communication

FM RADIO REPEATER DESIGN
ADVANCED ELECTRONICS COURSEWORK ASSIGNMENT
STUDENT NAME
STUDENT ID NUMBER
INSTITUTIONAL AFFILIATION
LOCATION (STATE, COUNTRY)
PROFESSOR (INSTRUCTOR)
DATE OF SUBMISSION
1

INTRODUCTION
The Radio frequency FM broadcast lies between HF and VHF (1MHz-100MHz) in the
electromagnetic spectrum. Some sections of the frequency spectrum are licensed by the
telecommunication regulators in a given country while others such as the ISM band and the short
range devices are unlicensed. In the radio station FM design, the communication mode is
simplex, i.e. a one-way communication. FM transmitter uses the Fractional-N synthesizers.
When the communication is done over a wide range, such as 100km in this project, one must
increase the output power by adding an external power amplifier, increase the sensitivity by
adding an external low noise amplifier, increase both output power and sensitivity and use the
high gain antennas following the regulatory requirements (Fagbohun, 2014). The FM radio
repeater design is built on discrete analog component that are integrated on two circuit boards,
for the transmitter and receiver components. The transmitter particulars are:
RF frequency=93.3 MHz
Stat ion name=YES 93.3 FM
adjacent channels 92.4 MHz∧93.8 MHz
FM Transmitter Block
2

The chart below shows that the selection of radio station frequency falls in the correct
frequency band. It is illustrated as,
Figure 1 The Frequency Band & application Chart [source: FM Broadcast ElectronicsHub]
FM Receiver Block
FM RADIO REPEATER DESIGN
(i) Transmit RF power amplifier
3

An external power amplifier is required to boost the signal power for transmission. A
higher signal power is responsible for transmitting a signal to greater lengths. The
mixer and the power amplifier can be designed using the capacitors and an
operational amplifier as shown in the circuit below,
The power amplifier is supplied with 20dB of gain to compensate for the weak mixer
output. For a maximum power transfer between the mixer and the power amplifier,
the matching network circuit above is used. A transmission line’s characteristic
impedance is achieved using the 1.8nF coupling capacitor system into the 50-ohm
system. It uses the Gali-5 amplifier network to perform the amplification (Electronics,
2018).
(ii) Matching network (IMN & OMN) using smith chart (Torrungrueng and Mekathikom,
2015)
4