Luke Commins-Blick HNC YR1 ELECTRICAL TWO-PORT NETWORK
WHAT IS A TWO PORT NETWORK? A two port network is an electrical deive with two pairs of external ports comprising of V1, V2, I1 and I2.(Shown in the picture below).
WHAT IS A TWO PORT NETWORK?
The two port network can be used to help calculate current or voltages in part of a circuit the device is connected to. As long as two out of the four variable are given any of the others can be calculated. The current entering one terminal must equal the current exiting the paired terminal.
USES OF TWO PORT NETWORK Two port networks can be used to isolate certain parts of a circuit. This would help in fault finding or calculating certain parameters. The two port networks take out any of the internal circuit voltages and currents generated. Two port networks are used to help impedance match like in communication systems where the antenna impedance needs to match the transmitter impedance to stop the power from being reflected back down the system and possibly causing damage.
USES OF TWO PORT NETWORKS Impedance matching is essential in many different scenarios. The one most common in my job role is the matching of antenna to the transmitter in Radio systems to stop power surging back up the system.
Impedance matching is done between to terminals or terminations and this is why the two port network is used for this as it can be used between different terminations. Impedance matching can be used with resistors, transformers, L-C sections etc.
TRANSMISSION LINES A transmission line is a device designed to guide electrical energy from one point to another. It is used to transfer an electrical signal from a transmitter to an antenna. This signal cannot be transferred through normal electrical wires without great losses. The ratio of voltage to current at the input end is known as the input impedance (Zin). This is the impedance presented to the transmitter by the transmission line and its load, the antenna. The ratio of voltage to current at the output end is known as the output impedance (Zout).
TELEPHONE SYSTEMS The electrical circuit inside telephones can be made of two port networks. This allows the processing of analogue and digital between the input and output ports. All this will depend on the voltage to current and input and output relationships and this will mean that there will be an input voltage and current and an output current and voltage going through the two port network. Two port networks can be used in telephone systems to calculate the series and shunt impedance as telephone systems primarily use series connections to parallel connections.
LOUDSPEAKER
Two port networks are used in loudspeaker systems to help maximise the output signal with as little distortion as possible. The two port network within a loudspeaker will contain slightly different components such as bipolar junction transformers or field effect transistors. Just like in Radio transmission lines the impedance the amplifier sees must match the impedance the speaker sees to allow for maximum power output.
BIBLIOGRAPHY
• http://www.globalspec.com/reference/75707/203279/2-6-na
• http://www.qsl.net/va3iul/Impedance_Matching/Impedance_ • http://www.tpub.com/neets/book10/41.htm • http://en.wikipedia.org/wiki/Image_impedance