Application: How C and L are used in an FSK WLAN circuit

Due No Due Date
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We've talked a lot in class about ways capacitors and inductors are used in practice. Here is an example of how they are used in a microwave engineering circuit. This circuit is provides a wireless communication link between two computers. Computers use data in digital format (1's = 5V and 0's = 0V), but we can't just send 5V and 0V wirelessly through the air. Some sort of coding scheme is needed to convert the digital 1's and 0's into a signal that can be transmitted wirelessly. There are many different coding schemes. This circuit uses Frequency Shift Keying Links to an external site.. The Frequency is used to code 1 or 0. This circuit transmits a 2.4GHz sine wave to represent a 0 and a 2.6 GHz sine wave to represent a 1.

Now... let's take a tour through this circuit. The videos give you a basic tour of the circuit and the several ways L and C are used in it.

You won't know how to design all of these pieces yet... You'll learn about the transmission lines in ECE3300, the FSK coding in Wireless Comm, the antenna in Antenna Design, and the rest of the circuit in Microwave Engineering (all senior year breadth electives). For the insanely curious, I'm including links to the various details of this circuit, but please don't think you should understand all of the stuff in those links YET!

FSK WLAN Overview Links to an external site.

FSK WLAN Antenna (uploading now) Links to an external site.

The transmission line in this circuit is a microstrip Links to an external site.. It is modeled, as all other transmission lines can be, as an RLGC circuit Links to an external site..
The antenna is a quarter-wavelength monopole antenna Links to an external site..

FSK WLAN Amplifier Links to an external site.

The Amplifier has a DC blocking capacitor Links to an external site.to prevent the DC that is powering the circuit from getting in to the higher frequency (AC) circuit. This circuit uses the 'inner only' model.
The Amplifier has a choke Links to an external site. (AC blocking inductor) to prevent the AC wireless signal from getting into the DC power supply.

FSK WLAN Splitter Links to an external site.

The splitter is a T-junction power divider Links to an external site.with quarter wave transformers Links to an external site. for impedance matching.

FSK WLAN Bandpass Filters Links to an external site.

Bandpass filters Links to an external site. allow one frequency or a band (range) of frequencies to pass through. They block all other frequencies and are made up of various combinations of L and C. The microwave version of L and C combinations can be implemented (as in this case) with coupled lines Links to an external site..

FSK WLAN Diode Detector Links to an external site.