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I found this ring modulator circuit on the internet

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I tried to simulate this circuit on LTspice, but it doesn't work. Here is the LTspice circuit:

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And these are the simulation results: (Green: message signal, Blue: carrier, Red: DSB-SC output)

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I probed the carrier voltage source to see the current flowing through it, and this is what I found:

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The current goes to 16A!

Edit: A user pointed out that my carrier signal was incorrect and that it was keeping 2 diodes permanently on. After changing the carrier signal for a 0-5V pulse to a -2.5V to +2.5V pulse, the high current draw problem has been solved, but I'm still not getting any output. Also, I noticed that there is current flowing through L4 and L5, but not L6. Are they not coupled even though there is a .s command?

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I tried simulating this on EveryCircuit, but it didn't work there either.

I'd like to know what I'm doing wrong. Or is the circuit itself wrong?

PS
V1: 2Vpp 1kHz
V2: 5Vpp 10kHz
All coils have an inductance of 1mH and resistance of 50mOhms.

Netlist

"ExpressPCB Netlist"
"LTspice XVII"
1
0
0
""
""
""
"Part IDs Table"
"L1" "1m" ""
"L2" "1m" ""
"L3" "1m" ""
"V1" "SINE(0 1 1k)" ""
"L4" "1m" ""
"L5" "1m" ""
"L6" "1m" ""
"D1" "1N5817" ""
"D2" "1N5817" ""
"D4" "1N5817" ""
"D3" "1N5817" ""
"V2" "PULSE(-2.5 2.5 0 1n 1n 50u 100u)" ""
"R1" "1k" ""

"Net Names Table"
"N006" 1
"N001" 4
"N005" 7
"0" 10
"N003" 17
"N007" 19
"N002" 22
"N004" 25

"Net Connections Table"
1 1 1 2
1 2 2 3
1 12 1 0
2 1 2 5
2 8 1 6
2 10 2 0
3 2 1 8
3 9 1 9
3 11 2 0
4 3 1 11
4 4 2 12
4 6 1 13
4 7 1 14
4 9 2 15
4 10 1 16
4 13 2 0
5 3 2 18
5 4 1 0
6 5 1 20
6 6 2 21
6 12 2 0
7 5 2 23
7 8 2 24
7 11 1 0
8 7 2 26
8 13 1 0

Thankyou for the answers. The circuit is now working.

enter image description here

Prathik Prashanth
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2 Answers2

7

Your K statements have a coupling coefficient of .0.98 - try changing that to 0.98.

rdtsc
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4

Your carrier has DC. It should be symmetric around zero to change which diodes conduct. The circuit is intended to make the carrier to alter the polarity of the input signal. Have one of the carrier source terminals = GND to see if the carrier source outputs what's needed.

  • I tried making the carrier symmetric about the x-axis and it solved the excessive current draw problem, but I am still not getting any output voltage. PS Moving the ground around didn't make any difference, as I expected. – Prathik Prashanth May 04 '21 at 12:00
  • Moving the ground doesn't change the function, it only makes possible to show the carrier as a single node voltage. Some simulators can show right it as a property of voltage source, no matter where the GND is and some need to make a formula like v(7)-v(8) where 7 and 8 are the (non-GND) poles of the voltage source. –  May 04 '21 at 12:20