Connect with us

Newbie - Trying to simulate 3.5MHz Xmtr - LTSpice

Discussion in 'CAD' started by Talion, Dec 23, 2004.

Scroll to continue with content
  1. Talion

    Talion Guest

    Greetings,

    I have never used a schematic capture program before and I am just getting back
    into electronics after many years, so I'm a bit rusty. Please bear with me.

    I am trying to simulate a low-power transmitter in the 3.5 MHz range in LTSpice.
    I would like to look at a plot of the emissions at ANT to see what my frequency
    output looks Like. Effectively, a frequency spectrum plot. I understand I should
    use an FFT plot after running a transient simulation, but I seem to be having no
    luck.

    I'm at a loss as to whether my schematic is faulty, I don't understand how to
    properly use LTSpice or both. In particular, I wonder if I have configured the
    crystal properly (a colorburst crystal) and whether I need a 50 Ohm load instead
    of the ANT output?

    Any insight would be appreciated, and I thank you in advance.

    My LTSpice circuit follows:

    ----- snip 3.5MHZ xmtr.asc -----

    Version 4
    SHEET 1 892 680
    WIRE 96 144 48 144
    WIRE -16 144 -16 208
    WIRE -80 272 -80 288
    WIRE -80 288 -16 288
    WIRE -80 208 -16 208
    WIRE -16 288 -16 336
    WIRE 48 224 48 144
    WIRE 48 144 -16 144
    WIRE 48 304 48 400
    WIRE 48 400 336 400
    WIRE 112 240 112 224
    WIRE 112 224 160 224
    WIRE 160 192 160 224
    WIRE 160 224 192 224
    WIRE 192 288 192 320
    WIRE 192 320 112 320
    WIRE 112 320 112 336
    WIRE 48 144 48 32
    WIRE 112 32 144 32
    WIRE 160 96 208 96
    WIRE 432 400 464 400
    WIRE 464 400 464 416
    WIRE 256 128 256 96
    WIRE 256 96 336 96
    WIRE 432 96 464 96
    WIRE 336 128 336 96
    WIRE 336 96 368 96
    WIRE 336 208 336 400
    WIRE 336 400 368 400
    WIRE 336 400 336 448
    WIRE 256 192 256 336
    WIRE 288 448 336 448
    WIRE 208 448 160 448
    WIRE 160 448 160 464
    WIRE 208 32 208 96
    WIRE 208 96 256 96
    WIRE 464 96 464 16
    WIRE 464 16 560 16
    FLAG -16 336 0
    FLAG 112 336 0
    FLAG 464 416 0
    FLAG 256 336 0
    FLAG 160 464 0
    FLAG 560 16 ANT
    IOPIN 560 16 Out
    SYMBOL polcap -96 208 R0
    WINDOW 3 24 64 Left 0
    SYMATTR Value 33µ
    SYMATTR InstName C1
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 mfg="Nichicon"
    pn="UPR1A330MAH" type="Al electrolytic" ppPkg=1
    SYMBOL res -32 192 R0
    SYMATTR InstName R1
    SYMATTR Value 5.6k
    SYMBOL res 32 208 R0
    SYMATTR InstName R2
    SYMATTR Value 15k
    SYMBOL res 96 224 R0
    SYMATTR InstName R3
    SYMATTR Value 470
    SYMBOL npn 96 96 R0
    SYMATTR InstName Q1
    SYMATTR Value 2N2222
    SYMBOL Misc\\xtal 112 16 R90
    WINDOW 0 0 32 VBottom 0
    WINDOW 3 32 32 VTop 0
    SYMATTR InstName C3
    SYMATTR Value 3.56169600e-014
    SYMATTR SpiceLine Rser=3.56169600e-014 Lser=0.0555779237 Cpar=8.90424001e-012
    SYMBOL ind 320 112 R0
    SYMATTR InstName L1
    SYMATTR Value 2.5µh
    SYMATTR SpiceLine Ipk=1
    SYMBOL voltage 304 448 R90
    WINDOW 0 -32 56 VBottom 0
    WINDOW 3 32 56 VTop 0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 9
    SYMBOL polcap 144 48 R270
    WINDOW 0 0 32 VBottom 0
    WINDOW 3 32 32 VTop 0
    SYMATTR InstName C4
    SYMATTR Value 0.01µ
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    SYMBOL polcap 176 224 R0
    WINDOW 3 24 64 Left 0
    SYMATTR Value 0.01µ
    SYMATTR InstName C2
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    SYMBOL polcap 240 128 R0
    WINDOW 3 24 64 Left 0
    SYMATTR Value 100µ
    SYMATTR InstName C5
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    SYMBOL polcap 368 112 R270
    WINDOW 3 24 64 Left 0
    SYMATTR Value 100µ
    SYMATTR InstName C6
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    SYMBOL polcap 368 416 R270
    WINDOW 3 24 64 Left 0
    SYMATTR Value 0.01µ
    SYMATTR InstName C7
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    TEXT -98 514 Left 0 !.tran 0 10m 0 startup
    TEXT -128 464 Left 0 !.option plotwinsize=0

    ------ snip end of file ------
     
  2. Talion,
    I made some adjustments to the circuit. Now it oscillates. It takes
    several
    milliseconds for the oscillation level to become stable. When you do the
    FFT, you'll want to limit the "Time range to include" to exclude the startup
    time.

    --Mike

    --- osc.asc ---
    Version 4
    SHEET 1 892 680
    WIRE 96 144 -160 144
    WIRE -336 240 -336 288
    WIRE -256 256 -256 288
    WIRE -160 224 -160 144
    WIRE -160 144 -256 144
    WIRE -160 304 -160 400
    WIRE -160 400 336 400
    WIRE 160 240 160 224
    WIRE 160 192 160 224
    WIRE 256 304 256 336
    WIRE 160 320 160 336
    WIRE -32 16 48 16
    WIRE 160 96 208 96
    WIRE 432 400 464 400
    WIRE 208 96 336 96
    WIRE 432 96 560 96
    WIRE 336 160 336 96
    WIRE 336 96 368 96
    WIRE 336 240 336 400
    WIRE 336 400 368 400
    WIRE 336 400 336 464
    WIRE 272 464 336 464
    WIRE 192 464 160 464
    WIRE -256 144 -256 176
    WIRE -336 288 -256 288
    WIRE -256 288 -256 320
    WIRE -336 176 -336 144
    WIRE -336 144 -256 144
    WIRE -160 144 -160 16
    WIRE -160 16 -96 16
    WIRE 256 336 160 336
    WIRE 160 336 160 352
    WIRE 160 224 256 224
    WIRE 256 224 256 240
    WIRE 48 112 48 96
    WIRE 48 32 48 16
    WIRE 48 16 112 16
    WIRE 176 16 208 16
    WIRE 208 16 208 96
    FLAG -256 320 0
    FLAG 160 352 0
    FLAG 464 400 0
    FLAG 160 464 0
    FLAG 560 96 ANT
    IOPIN 560 96 Out
    FLAG 48 112 0
    SYMBOL res -272 160 R0
    SYMATTR InstName R1
    SYMATTR Value 15K
    SYMBOL res -176 208 R0
    SYMATTR InstName R2
    SYMATTR Value 45K
    SYMBOL res 144 224 R0
    SYMATTR InstName R3
    SYMATTR Value 470
    SYMBOL npn 96 96 R0
    SYMATTR InstName Q1
    SYMATTR Value 2N2222
    SYMBOL Misc\\xtal -32 0 R90
    WINDOW 0 0 32 VBottom 0
    WINDOW 3 32 32 VTop 0
    SYMATTR InstName C3
    SYMATTR Value .03561696p
    SYMATTR SpiceLine Rser=0 Lser=55.5779237m Cpar=8.90424p
    SYMBOL ind 320 144 R0
    SYMATTR InstName L1
    SYMATTR Value 100µ
    SYMBOL voltage 288 464 R90
    WINDOW 0 -32 56 VBottom 0
    WINDOW 3 32 56 VTop 0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 9
    SYMBOL polcap 368 112 R270
    WINDOW 3 24 64 Left 0
    SYMATTR Value 100µ
    SYMATTR InstName C6
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine Rser=2.3
    SYMBOL polcap 368 416 R270
    WINDOW 3 24 64 Left 0
    SYMATTR Value 0.01µ
    SYMATTR InstName C7
    SYMATTR Description Capacitor
    SYMATTR Type cap
    SYMATTR SpiceLine V=10 Irms=60m Rser=2.3 MTBF=1000 Lser=0 ppPkg=1
    SYMBOL cap 176 0 R90
    WINDOW 0 0 32 VBottom 0
    WINDOW 3 32 32 VTop 0
    SYMATTR InstName C4
    SYMATTR Value 200p
    SYMBOL cap 32 32 R0
    SYMATTR InstName C5
    SYMATTR Value 100p
    SYMBOL cap -352 176 R0
    SYMATTR InstName C1
    SYMATTR Value 25p
    SYMBOL cap 240 240 R0
    SYMATTR InstName C2
    SYMATTR Value .01µ
    TEXT 510 258 Left 0 !.tran 10m startup
    TEXT -136 80 Left 0 ;3.58007MHz
    TEXT 504 304 Left 0 !.options method=trap
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-