Hi everyone,
Is any simulation project available for the RX and TX matching circuits (LTSpice, Altium, …)? If not, can someone provide some insight on how the following figures were made:
https://myriadrf.org/blog/optimising-limesdr-matching-hf/
Thanks!
Hello marsupial67
I have used LTspice to simulate the filters for receive Low input and transmit output. The receive filter uses the Minicircuits TC1-1-13MA+ four port transformer. The specifications are defined in S parameters. LTspice uses spice models; however there is a s2spice.exe utility which will convert up to 8 ports (touchstone format) to spice. The source code and s2spice.exe can be found on the Yahoo LTC spice group site. To simulate, use the s2spice.exe utility to convert s parameters to spice. Make sure you have the port order defined correct. The common or reference can be used as the ground point. Use the same procedure for the two port transmit transformer. This works for the AC mode; but not for the transient mode. Otherwise use standard parts for circuit completion. I did have to make a guess for the LMS7002M input impedance. My guess was about 2K (balanced). TX output impedance was given in the data sheet 50 ohms (balanced).
With LTSpice, it’s easy to compare the RX input frequency response with the inductor installed or removed and plot on the same graph. Use the step command. LTspice will allow for symbolic values i.e {R} encased in {}. I also used ADS design software. I liked LTC better than ADS; it’s much easier to use with similar results and its free. ADS is very costly $$$$$!