VHF IQ RX 2014

Description

At the beginning of 2014 I wanted to build an IQ receiver like the HDR2007, but for higher frequencies (up to VHF). The common switching mixers with the analogue switches or multiplexers function only up to 25 MHz or something like that. One option was to use IQ mixer chips, like the LT5517. Another possibility I saw in the old AD831 mixer (DC to 200 MHz).

A further problem, however, is the generation of the IQ signal for the local oscillator with this high frequency. The Si570 XO is well suited, but how should a 90° offset signal be generated from the output signal?

One possible solution is to use a PECL building block like the MC100EP52 (ECL differential clock D flip-flop ). But still an adaptation problem is to solve. The adaptation of the Si570 LVDS output to the MC100EP52 input and then the MC100EP52 LVPECL output to the AD831 inputs.

The Si570 and control board should also be used for other purposes. It provides four signals with 0, 90, 135 and 180° phase shifts. In this version of 2014, the Si570 is not yet heated to keep the temperature drift low.