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.

Schematics


VHFIQRX01.jpg
Si570 Control
VHFIQRX02.jpg
Si570 PSU
VHFIQRX03.jpg
uC PCB
VHFIQRX04.jpg
Quadarture
VHFIQRX05.jpg
Quadr. PCB
VHFIQRX06.jpg
Matching
VHFIQRX07.jpg
AD831 Mixer
VHFIQRX08.jpg
Mixer PCB
VHFIQRX09.jpg
Signal path
VHFIQRX10.jpg
AF Amp
VHFIQRX11.jpg
AF Amp PCB
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Pictures


IQRX_Pic1.jpg
RX design
IQRX_Pic2.jpg
Mixer PCB 1
IQRX_Pic3.jpg
Mixer PCB 2
IQRX_Pic4.jpg
AD831 IQ mixer>
IQRX_Pic5.jpg
Controller PCB 1
IQRX_Pic6.jpg
Controller PCB 2
IQRX_Pic7.jpg
RX test board
IQRX_Pic8.jpg
RX test
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Firmware


firmware.jpg
VHF IQ RX Control (Si570)

References

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