Antennas and Microwaves

Entry Page

Contents

Here are 2 directional couplers fabricated by hand, both couplers are designed to work at 1 Ghz.

        Top is a basic ¼ wave coupler using discrete capacitors. (Coupling factor 10dB)

        Bottom is an Odd/Even mode microstrip coupler. (Coupling factor 20 dB)

PCB Prototyping

WHAT IS POSSIBLE

With a little practice it is possible to produce a simple device, such as one of the couplers above, in around 1 hour (printout to board, ready for testing) . With care, track widths can be realised to within +/- 0.1mm. For 50 Ohm track on 0.76mm RO4350 this equates to around +/- 2 Ohms.

Some other circuits that lend themselves to this approach include hybrids, power splitters, filters, impedance transformers and patch antennas.

For more complex layouts and improved accuracy something a little more sophisticated is required. I mentioned in the introduction, CNC micro-milling machines as an alternative to chemical etching and promptly dismissed them as rather expensive. However, for the more cost conscious there is a halfway house in the form of desktop sign makers.

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PCB Prototyping

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Start in a corner and work along an edge.

DRILLING AND PEELING contd

For the peeling you will need a soldering iron with a broad bit (see photos), a modelling knife, some thin nose pliers and a little patience. Small areas will peel quite easily once started. For larger areas try and lift a complete edge using the iron and knife, then just peel by hand.

Large areas can be peeled off in one.