voltage control oscillator

Plastonek's "RF Oscillator Circuit Analysis and Design with Breadboard Experiments" has something very similar to this, but it's probably impossible to get ahold of anymore. Wes Hayward's "Introduction to Radio Frequency Design" has enough information to get you going as well...

A 40MHz deviation on a 137MHz carrier is huge, though -- do you really need it? I don't think there's any reasonably simple way to get such a huge deciation using "simple" VCOs... you'd be much better off getting 40MHz deviation at, e.g., 800MHz and then mixing the result down to a center of

137MHz.

On a sunny day (Thu, 24 Jan 2008 20:13:45 -0800 (PST)) it happened javvad wrote in :

varicap LC have transistor connect ;-)

Okay, good luck with your endeavor.

As Joel Koltner says, this is a large frequency deviation for a 137MHz varactor tuned oscillator.

It would probably be a lot easier - if rather more expensive - to buy one of the faster Analog Devices direct digital synthesis (DDS) chips, such as the AD9911

and an analog to digital converter, then digitise your voltage and use the digital output to set the output frequency.

This won't work if this is a homework problem or a design for high volume production, but for a lot of real life applications it offers the quickest and most reliable route to the frequency range you are asking for.

Analog Devices have a lot of DDS chips aimed at a variety of application - the AD9911 was just the cheapest one on the list that could get up to 174MHz.

-- Bill Sloman, Nijmegen

-- Bill Sloman, Nijmegen

ble

d

ok but 800mhz is near to microwave range there are orter problems at microwave range 1st how i will see these 2nd help me what you advice me what are the techiniques to control deviation thanks

800Mhz is no where near microwave! Its UHF. 3Ghz is microwave.

--
Best Regards:
                     Baron.

American Heritage dictionary defines microwave as 1 mm to 1 m in length. 800 MHz is .375 m, so it would qualify. Merriam-Webster also says "between about one millimeter and one meter". The Wikipedia article "microwave" agrees - 300 MHz to 300 GHz.

I think the article you cited intends to include UHF in microwaves. The sentence is a little unclear: "Radio waves whose frequency is above the UHF band fall into the SHF (Super high frequency) and EHF (Extremely high frequency) bands; all of which fall into the Microwave frequency range."

However, there are other dictionaries show different limits... Encarta dictionary says "1 mm to 30 cm" Compact Oxford English Dictionary says "0.001-0.3 m". That would be a lower limit of 1 GHz, which would put 800 MHz pretty close.

--
John

Minicircuits has a nice selection of inexpensive VCO modules, as well as RF mixers, you can use to solve your problem,

The definition implies sub definitions of microwaves.

Mmmm. My ARRL Handbook sites UHF from 300 to 3000 Mhz and VHF 30 to 300 Mhz Page 4:14 Without stating microwaves.

But I do agree that it isn't very clear, and I haven't found anything more definitive.

I suspect that like you, I have taken ( U micro ) to mean 1000th part of, and in that context we must agree.

As a ham... 3Ghz plus is microwaves. 10 & 24 Ghz is plumbing. ;-)

--
Best Regards:
                     Baron.

--
The 1000th part is \'milli\', while the one-millionth part is \'micro\'.

Ooo Hangs head in shame. ;-) Thanks for the correction.

--
Best Regards:
                     Baron.

Does anyone have a clue about what the OP is building?

40 MHz. Bandwidth at 137 MHz. seems a bit out of scale. Around 137 MHz is, if I recall correctly, where some of the satellite weather maps are transmitted, and a 40 kHz bandwidth would be approriate.

40MHz is only out of scale if he is building a radio. Lots of other things require frequencies as high as radios but are doing very different things with them. For all we know he may be making a new version of the "Russian woodpecker".

ble

d

can u see this data sheet for me

and give the advice can i do this with this device thanks

First, you said you wanted 117 to 157MHz, right? This part with its 148 to 174MHz range, misses on having the right frequency, and with only 26MHz of span, or 15% of Fmax, it misses on that account as well - you asked for 25% span. Also, did you notice its tuning sensitivity changing from 16 to 11 MHz/V across the span? That's tuning nonlinearity.

This MiniCircuits VCO is pretty representative of what's feasible in VCO design, and shows why Joel suggested that you mix the outputs of two high-frequency oscillators, like 800MHz. First, you can get enough deviation, and second, you can select a high enough frequency so that you can use say the bottom 30 to 40% of the tuning range and thereby get better linearity. Go look at those high frequency MiniCircuits VCOs.

ssible

ncy

need

ge

of

what is the theory of vco well if i apply the message signal at input like ramp and initial frequency is let suppose 125MHZ and final frequency is 200MHZ weather it will change the frequency of VCO or not from 125MHZ to 200MHZ

2nd does frequency of message signal can be greater then carrier frequency? thanks

ssible

ncy

need

ge

of

can u see this for me

?name=3D744-1057-= ND or this

25-0200.pdf or advise me for direction

I think it's time you told us what you're trying to do.

.

i m designing frequency jammer and i have to generate band 137MHZ to

177MHZ for this porpuse i see the BP.lathi book page 230 there a method given for wide band fm but my circuitry is too large with this then i think to make vco for this to vary the input signal and output sig frequency very with this and i can cover whole band i want to know that weather i m going right way or can u guid me in this whole work