Here are a few options for replacement BALUNs from Mini Circuits and specs:
Current. TCM1-83X+, 10-8000 MHz, 50 Ohms, Impedance Ratio 1, Configuration K
1. Z7550-..., DC-2500 MHz (some DC-2300), 50/75 Ohms, Impedance Ratio 1.5, Configuration Q. There are various types of the Z7550 which have different connectors (SMA and BNCs). These have much larger dimensions than the TCM1-83X. Can handle up to 5A DC current with matching loss 0.6 dB.
2. SFMP-5075+, DC-2500 MHz, 50/75 Ohms, Impedance Ratio 1.5, Configuration D. This is an SMA connected BALUN. It can handle 350mA, has a matching loss 0.4 dB, and has 1W power handling.
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Seems like it should be possible to just remove the transformer (aka as a BALUN ... BALanced, UNbalanced), or replace it with a lower frequency part. Its just a usual mini-circuits part. Maybe you can ask Chris Stoughton about this and ask Tommy to checkout some of the RFSoC user forums for how to go to DC.
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After fiddling around with the tone-generators and spectrum analyzer tools in loopback configuration (DAC --> ADC direct connection), we noticed that lower frequency (~ 1 MHz) signals were hardly making it out/back into the board... so we looked at some of the schematics found here and saw that both RF data converters (ADC & DAC) interfaces are AC coupled through a BALUN network in the 10 - 8000 MHz band (see Attachment #1). This is in principle not great news if we want to get this board ready for audio-band DSP.
We decided that while Tommy works on measuring TFs for SHP-200 all the way up to ~ 2 GHz (which is possible with the board as is) I will design and put together an analog modulation/demodulation frontend so we can upconvert all our "slow" signals < 1MHz for fast, wideband DSP. and demodulate them back into the audio band. The BALUN network is pictured in Attachment #2 on the board, I'm afraid it's not very simple to bypass without damaging the PCB or causing some other unwanted effect on the high-speed DSP.
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| model_no |
case_style |
single2single |
single2bal |
bal2bal |
center_tap |
dc_iso |
freq_low |
freq_high |
impedance |
imped_ratio |
interface |
tech |
config |
| SFMP-5075+ |
FF1891 |
Y |
N |
N |
N |
N |
DC |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
D |
| TCM1-83X+ |
DB1627 |
N |
Y |
Y |
N |
N |
10 |
8000 |
50 |
1 |
SMT |
CORE & WIRE |
K |
| Z7550-BFNF+ |
H795-14 |
Y |
N |
N |
N |
N |
DC |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-BMBF+ |
QP1876-1 |
Y |
N |
N |
N |
N |
DC |
2300 |
50/75 |
1.5 |
CON |
CORE & WIRE |
D1 |
| Z7550-BMNF+ |
QP1876 |
Y |
N |
N |
N |
N |
DC |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-FFNM+ |
H795-1 |
Y |
N |
N |
N |
N |
DC |
2300 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-FFSF+ |
H557-1 |
Y |
N |
N |
N |
N |
DC |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-FMSF+ |
H795-3 |
Y |
N |
N |
N |
N |
DC |
2300 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-FMSFDC+ |
H795-3 |
Y |
N |
N |
N |
Y |
1 |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
| Z7550-NFNF+ |
H795-10 |
Y |
N |
N |
N |
N |
DC |
2500 |
50/75 |
1.5 |
CON |
CORE & WIRE |
D1 |
| Z7550-NMNF+ |
H795-4 |
Y |
N |
N |
N |
N |
DC |
2300 |
50/75 |
1.5 |
CON |
CORE & WIRE |
Q |
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