A Transceiver is a device which can be both used for transmission and receiving purposes. Some devices are also called transmitter-receiver, but they are different from transceiver as they don't share common circuitry or single housing whereas transmitter and receiver within a transceiver share common circuitry or a single housing. There are many types of transceivers: RF transceivers, fibre-optic transceivers, Ethernet transceivers, wireless (WAP) transceivers, and more but here we are mainly concerned with RF transceiver for satellite purposes.<ref>http://www.pearsonitcertification.com/articles/article.aspx?p=398091&seqNum=13</ref><br \>

Our mobile phones, walkie-talkie etc. are examples of transceivers. <br \>

A modem is similar to a transceiver, in that it sends and receives a signal, but a modem uses modulation and demodulation. It modulates a signal being transmitted and demodulates a signal which is received. <ref>https://en.wikipedia.org/wiki/Transceiver</ref> <br \>

This beacon board is an elementary example of a transmitter. <br \>

Next, we have Downlink board. The Downlink signal contains telemetry data. Hence it has to communicate with the On-Board Computer to gather the data which needs to be transmitted. This data is received in packeted form which is passed from On-board microcontroller (downlink board microcontroller) to the transceiver CC1101 (Texas Instruments). It modulates the signal using [https://en.wikipedia.org/wiki/Frequency-shift_keying FSK modulation] on the 437.455 MHz frequency. This signal then passes through Power Amplifier which amplifies the signal, and it is radiated through the monopole antenna. <br \>

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