circuit of frequency sweeping

[suribright]

Hi, please tell me how to design a circuit of frequency sweeping from 1MHz to 30MHz? I need actual circuit not theory. Thanks

 

[themaccabee]

If u are not looking for a discreet implementation ,what about using a DDS IC from analog devices..AD9850 like that..u can control the frequency using a micro controller..

 

[WimRFP]

There is some contradiction in your request. You ask us to tell you: "how to......", but you also state: "no theory". How can we tell you without theory?

Some other issues to consider: tuning/sweep speed, phase noise, linearity, harmonic and spurious content, etc.

 

[suribright]

yes we must know theory, WimRFP. what I mean is no coding program like matlab. I need a continuous sine wave sweeping from 1MHz to 30MHz. I think it is linear frequency modulated signal. Do you have any circuit to acknowledge me please?

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@themaccabee: I dont know which part of AD5930 can do. Please tell me more. Thanks

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I have searched internet and see this link may do my job http://www.circuitstoday.com/sweep-frequency-generator . Is there any one have this design? Thanks

 

[WimRFP]

In older times, HF sweep generators with large Fmax/Fmin were made based on a high frequency VCO (Voltage Controlled Oscillator, for example 170..200 MHz) and a second fixed frequency oscillator (for example 150 MHz). Both outputs are fed into a mixer (functionally a multiplier) and the difference frequency (here 0..30 MHz) is selected via a low pass filter.

Using such approach enables you to convert a sawtooth voltage (the control voltage for the VCO) into a continuous frequency sweep.

Why such an approach? You practically can't make a single sinusoidal RF oscillator with a relative tuning range of 30MHz/1 MHz = 30. By using the mixer approach, the tuning range is reduced.

Depending on the required linearity, linearizing circuits are required making the design more complex.

 

[ninju]

Use a FPGA, build a NCO, control the frequency, use a DAC and a filter to make it a continuous wave. Building a pure analog circuit with 1-30MHz is pretty complicated using discrete components alone. You might want to look for some FM generator circuits or a circuit that can generate chirp signals if you insist on analog alone.

In integrated circuit design, please use a current starved ring oscillator. I've used it with tuning ranges in GHz.

 

[phongphanp]

Analog and Digital can be the band selector , But only Digital memory use to store datum form practical circuit design by own or collection CD,DVD in market.

 

[suribright]

Hi WimRFP, ninju, phongphanp and all, Is there any one have a ready circuit in use or circuit I can change a bit? Thanks

 

[phongphanp]

IP protect by law, so I cann't show any. May you try search at https://patft.uspto.gov/ ?

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IP protect by law, so I cann't show any. May you try search at https://patft.uspto.gov/ ?

 

[suribright]

@phongphanp . Cant find what I need in that website.