[time-nuts] Varactor frequency dividers question

Mike Monett timenuts at binsamp.e4ward.com
Wed Feb 3 02:04:12 EST 2016


>Hi,
>
>I'm looking for a copy of the following document.
>
>"Parametric frequency divider basics. (technical note )"
>
>>From the Microwave Journal Sept 1 1989.
>
>Can anyone help?
>
>Thanks,
>
>Corby
>
>Abstract below.
>
>>>>Since the introduction of half octave bandwidth microwave frequency
>dividers and full octave models, parametric frequency dividers have found
>applications in many microwave systems.
>General Description
>The parametric frequency divider is constructed using two varactor diodes
>in a resonant circuit. These diodes are biased slightly forward under
>normal operation. The input signal capacitively is coupled into the
>matching network for the two diodes, where it drives both of the diodes
>in phase. Due to the modulation of the varactor's capacitance at the
>input frequency f, a subharmonic resonance is set up in the diode pair at
>half of the input frequency, f/2. [1] This signal appears across both of
>the varactor diodes, but at 180[degrees] out of phase with each other. It
>is possibly, by using a balun connected to both diodes, to cancel the
>input signal f. However, by observing the signal on one of the diodes in
>the time domain, it can be seen that balancing is unnecessary. This
>signal appears as a negative impulse train with a period of f/2, with a
>positive maximum at the varactor's turn-on threshold voltage of 0.7 V. An
>electrical schematic diagram of a typical divider is shown in Figure 1. 

Corby,

If you use LTspice, this may be what you are looking for. The basic
circuit is courtesy Phil Hobbs in the newsgroup
sci.electronics.design.

I improved it by changing varactor D2 to a schottky diode. This
increased the output amplitude slightly and reduced the harmonic
distortion. You can easily change it back to see the original.

I verified it runs on a virgin copy of LTspice. If you have problems,
pleae let me know.

You can download LTspice at http://www.linear.com/designtools/software/

It is free.

Mike

Here is the circuit file:

Version 4
SHEET 1 880 680
WIRE 416 32 272 32
WIRE 464 32 416 32
WIRE 512 32 464 32
WIRE 512 48 512 32
WIRE 272 64 272 32
WIRE 416 96 416 32
WIRE -16 144 -32 144
WIRE 64 144 -16 144
WIRE 192 144 144 144
WIRE 272 144 272 128
WIRE 272 144 192 144
WIRE -32 160 -32 144
WIRE 512 160 512 128
WIRE 512 176 512 160
WIRE 272 192 272 144
WIRE -32 256 -32 240
WIRE 272 272 272 256
WIRE 416 272 416 160
WIRE 416 272 272 272
WIRE 512 272 512 256
WIRE 512 272 416 272
WIRE 416 304 416 272
FLAG 416 304 0
FLAG -32 256 0
FLAG -16 144 Vin
FLAG 192 144 R1D1
FLAG 464 32 Tank
FLAG 512 160 L1R2
SYMBOL varactor 256 64 R0
SYMATTR InstName D1
SYMATTR Value KV1471
SYMBOL cap 400 96 R0
SYMATTR InstName C1
SYMATTR Value 1000p
SYMBOL ind2 496 32 R0
SYMATTR InstName L1
SYMATTR Value 10µ
SYMATTR Type ind
SYMBOL res 48 160 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 100
SYMBOL voltage -32 144 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value SINE(5 10 3e6 1u)
SYMBOL res 496 160 R0
SYMATTR InstName R2
SYMATTR Value 5R
SYMBOL schottky 288 256 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D2
SYMATTR Value BAT54
SYMATTR Description Diode
SYMATTR Type diode
TEXT 88 0 Left 2 !.tran 0 30u 25u 10n
TEXT 88 -24 Left 2 ;'Hobbs Halver Improved MRM

Here is the plot file:

[Transient Analysis]
{
   Npanes: 4
   {
      traces: 1 {524291,0,"V(tank)"}
      X: ('µ',1,0,5e-007,5e-006)
      Y[0]: (' ',1,-1,0.2,1)
      Y[1]: ('_',0,1e+308,0,-1e+308)
      Volts: (' ',0,0,1,-1,0.2,1)
      Log: 0 0 0
      GridStyle: 1
   },
   {
      traces: 2 {524290,0,"V(vin)"} {524294,0,"V(r1d1)"}
      X: ('µ',1,0,5e-007,5e-006)
      Y[0]: (' ',0,-6,2,16)
      Y[1]: ('_',0,1e+308,0,-1e+308)
      Volts: (' ',0,0,0,-6,2,16)
      Log: 0 0 0
      GridStyle: 1
   },
   {
      traces: 1 {34603013,0,"I(D2)"}
      X: ('µ',1,0,5e-007,5e-006)
      Y[0]: ('m',0,-0.005,0.005,0.05)
      Y[1]: ('_',0,1e+308,0,-1e+308)
      Amps: ('m',0,0,0,-0.005,0.005,0.05)
      Log: 0 0 0
      GridStyle: 1
   },
   {
      traces: 2 {34603012,0,"I(D1)"} {34603015,0,"I(L1)"}
      X: ('µ',1,0,5e-007,5e-006)
      Y[0]: ('m',0,-0.028,0.004,0.016)
      Y[1]: ('_',0,1e+308,0,-1e+308)
      Amps: ('m',0,0,0,-0.028,0.004,0.016)
      Log: 0 0 0
      GridStyle: 1
   }
}


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