The microwave world is changing everyday. With engineers constantly striving for higher bandwidth, microwave frequencies are the natural place to exploit. With so many engineers working on the problem, there are new devices available every month. Of particular interest are the new surface mounted devices that can make the job of integration much easier and cheaper.

Jumper

There is a much better alternative to the jumper available from Anaren (website). Anaren has been particularily active in releasing new surface mount devices, including many types of couplers and power splitters in their new "Xinger" product line. The particular device we would use is a Crossover, which allows one signal to jump over the other. Anaren offers both a RF-RF (datasheet)and an RF-DC (datasheet) version, which offer 25 dB isolation from 0-6 GHz.

Mixer

Minicircuits has a new type of mixer available. It comes in their new "Blue Cell" product line. It offers better LO-IF isolation in a more reliable and stable package. It works up to 6.7 GHz and costs slightly less. Unfortunately, it has a slightly different outline from the older sky-60's so we cannot use them without a redesign.

filter

In future versions we might also leave the filter design to the experts. To go to higher frequency or to broader bandwidths may require more exotic designs which are usually proprietary. It is possible to get a filter manufacturer like K&L to make a filter that is either surface mountable or has tabs that can be integrated into a circuit.

impedance matching

The primary design limitation is the impedance mismatch on the RF input of the mixer. If we could carefully characterize the impedance of the mixer, a proper circuit can be designed to match the filter to the mixer. A much easier method to make the mixer "termination insensitive". That is to put an attenuator , which is essentially a resistor network, between the mixer and the filter. The input of the attenuator can be designed to be less dependent on the input of the mixer or the resistor values can be specially chosen. The only problem with this approach is, of course, the attenuation. The power into the mixer must be increased accordingly.