it is relative easy to make a perfect 50% square wave from almost any
input wave form
U1 could be any-- fast enough for the desired frequency--comparator or
a transistor pair similar to Charles Wenzel's circuit, R1 C1 is a long
time integrator,[ RxC >> 1/f of the incoming frequency] the voltage at
"A" is proportional with the duty cycle, U 2 is some high gain low
noise, low input offset voltage high input impedance amplifier, the
duty-cycle is set by R4/R5, fine tuning with R6, C2v removes the noise
Vr is well stabilized reference voltage,
To set up the circuit the output should be connected -- with DC
decoupling -- to a spectrum analyzer's input for watching the second
harmonic [a perfect 50% duty cycle square wave lacks of even harmonics
..] of the input frequency, which has to be adjusted to minimum with R6,
using the same stile resistors for ±0,1%, R4 and R5, with value 100
times of R6 a very good temperature stability could be achieved. for
better short time stability R2 's top could bealso connected to Vr,
If the drive capability of U1 is not enough for the load non-inverting
buffers could be inserted to U1's output, of course that circuit wil
contribute some phase noise/ jitter too.
73
KJ6UHN
Alex
On 7/25/2015 1:34 AM, tim...@timeok.it wrote:
bypassing the inverter you will improve phase noise. Yuo will probably
need a sine buffer at 10MHz to drive 50 ohms.
This separator con be the solution:
http://www.timeok.it/files/hp5065AoptH10v200.pdf
high input impedance, output 50Ohm, high power handling and low additive phase
noise.
But before measure using an oscilloscope the output of the GPS OCXO directly on
the output pin to verify if there is a sine-wave or square
Luciano
timeok
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