Mixer-LT5512, LT5526, LT5560, LTC5562

Question

Hi, 
 I have RF input signal from 300 kHz to 12 GHz, and IF is 20 MHz . One of the design requirements is active mixer as we want a low LO drive.The frequency conversion will be split into 2 mixers, one covers 300 kHz to about 3 to 4 GHz, and the second one covers from there to 12 GHz. For the first mixer having RF input from 300 kHz to 3/4 GHz, it will need to perform up and downconversion together as the IF is 20 MHz. 
 
 When I looked through the catalogue from ADI, some mixers are labelled as downconverting, while others are "downconverting, upconverting". For example: 
 LT5512, LT5526 - Downconverting mixer 
 LT5560, LTC5562 - Downconverting mixer, Upconverting mixer 
 So, are any of these mixers able to perform both up and downconversion in a single circuit?

shsiao · Accepted Answer

As long as your application RF/LO/IF frequencies are within the active mixer's specified RF/LO/IF frequency ranges, it can be used as either upmixer or downmixer. However, many of our mixer products have on-chip baluns which have limited frequency range and in turn limit the mixers' usage as only upmixers or downmixers. 
 The 4 mixers you identified do not have on-chip balun, and all can be used for either upconversion or downconversion. 
 For your particular application, I would recommend LTC5510 for the 1st mixer, and LTC5548/LTC5549 for the 2nd mixer. 
 The LTC5510 is a wideband active mixer. 
 The LTC5548 / LTC5549 are wideband passive mixer with on-chip LO buffer and require only 0dBm LO drive.)

shsiao · Answer

Happy New Year Carmen. I apologize for the delayed response. Notifications of your follow up question did not reach me. 
 LTC5510 is only rated for up to 6GHz. Performance degrades rapidly above 6GHz. I would recommend that you break up your frequency range in to two bands, and use LTC5510 for 300kHz to 4GHz and LTC5548 for 4GHz to 12GHz. 
 The recommended LTC5510 input matching will have fairly poor return loss from 300kHz to ~20MHz. If the performance degradation from poor matching is not acceptable in your application, you can further break down the 300kHz to 4GHz band into two bands: 300kHz to 30MHz and 30MHz to 4GHz. The LTC5510 datasheet provides s-parameter data and low frequency equivalent circuit.

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Products Mentioned

Mixer-LT5512, LT5526, LT5560, LTC5562