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  1. X

    How to FREQUENCY TUNING OF CRYSTAL OSCILLATORS ?

    Hello Luvu, Your request is practicaly inposible ~2.3% working frequency . It is too wide range for any type of quarz crystal units. You have to change your solutions with alternative like PLL or DDs are. XTASA
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    Help me make a substitute for CLC414

    CLC4141 replacement Hello, I have task to make substitute for CLC414 with the similar IC. My first attempt with OPA4684 are catastrofic I obtain only oscillation 1. Is any IC direct replacement 2. How to stop oscilation I have 6 IC in raw. Thank you very much in advance XTASA
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    Phase Noise Requirement in OFDM System!

    Dear Dopradar, You can find a lot of literature with a lot of mathematics to explain nature of problem you interested. My explanation is going from simple fact that you have demodulate/MIX signal than we have multiplying two signals (for beginning ideal source and non ideal carrier)and...
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    Phase Noise Requirement in OFDM System!

    RFSYSTEM, One very easy and clean expalnation starting from natural noise which is -174 dBm/SQR Hz For 1 Mhz bandwith is -174+10 log B=-114dBm minimum bandwith for 8 MHz bandwith OFDM TV is 10 MHz it is +10 dB which will give -104 dBm. for good receiving we have to S/N=12 dB + F(dB) of...
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    Nonlinear model for dual gate MOSFET BF996.. or similar

    dual gate mosfet spice Hello RF population, Where I can find nonlinear model for commercial dual gate MOS FET types like BF996,BF998....or similar. Thank you very much for help in advance ! XTASA
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    VCO & Start up Circuit

    Dear HRKHARI, I shall try to explain nature of your problems. When you turn ON OSC all C and L are empty. If we have condition that is Aβ>>1 OSC(no Aβ>=1 or little higher than 1 this is only in steady state ) oscillation will start slowly until it arrive to steady state oscillation. During...
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    Which architecture is the best for highly linear VCO?

    Re: highly linear vco Hello Sven, Your question is question general type or you have some specific frequency requirement. I made some extremely linear VCO voltage/frequency but is frequency depending solution. Gl XTASA
  8. X

    Pulling range for Crystal Oscillator?

    Hello Prakash, Pulling overtone oscillators are not good solution first and second range is very limited. Better crystal and oscillators are reducing pulling range. It is possible to increase pulling range but you have to sacrifice stability. What is your real task( frequency stability or...
  9. X

    Bias Circuit for Class-AB Microwave Amplifier

    Hello Snmeciut, Please check Polyfet site you will find circuit with diodes which working well . I test it with a lot RF LDMOS transistors and if you calculate elements correct it works really fine with temperature. GL XTASA
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    Linearity problem in designing VCO

    Hello somf0872, Your HB model with lumped element(spacial case of distributed elements) work maybe problem is that you use infinite Q for lumped elements ? If it is case you can try with real Q you can expect from distribudet elements around 20-80 max. Real Q have to give quite different...
  11. X

    RF power amplifier?????????

    Hello Willem, I think that your choice of BFG135A transistor as power amp for that levels is not good. Please specify your requirements and VCC /I which you can use in amp than we can suggest you a much better solution maybe:?:. GL XTASA
  12. X

    Help me design a Quagi antenna using 4 elements

    quagi antenna calculator Hello Weis Guy, Check www.cebik.com for all antenna problems ,you will find a lot of info. GL XTASA
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    What's the reasonable output power level for a CMOS VCO?

    Hello Sapphire, Your result for VCO output power is very good if you obtain 3.5dBm or 2.2mW from about 14mW input or 15% effiency. GL XTASA
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    How the "attenuation pad" smooth out impedance mis

    Re: How the "attenuation pad" smooth out impedance Hello Trashbox, If you putting Pi or Tee attenuator between two stages you will improve isolations between them . Bigger attenuation better isolation. Physical explanation is a very simple. ATT decrease useful signal but also unwanted...
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    Tuning range when varactor is placed parallel to a capacitor

    Re: Varactor tuning Hello Redhat, What is your question? XTASA
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    Polyphase Filter Buffer driver?

    Hi _RFIC_, Yes it is necessaryto have buffer between polyphase network and source Also it is importan that you have a high impadance load. Emitter follower is bad solution it have a limitted dinamic range. Best solution is to put some low comsuption OPAMP and that you put it in +1 follower...
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    How to design a VCO that has a good performance

    Re: Some VCO Questions Hello Redhat, The easy way to design VCO is to use your resonant circuits and amplifier at the loop with no real negative impedance amplifier . With elements you can adjust resonant frequency that is shift 0 or 180 degree or what is necessary it depends of amplifier...
  18. X

    Oscillator design problems

    Which model including package?? XTASA
  19. X

    Oscillator design problems

    Hello Helio 1972, If it is difference so big that the oscillation doesn't exist. Please check model given by NEC does it include packaking or not. Parasitic parameters are so important to reliable oscillation in GHz region and for good design of oscillators it is necessary to be included. GL XTASA
  20. X

    vhf uhf filter design problem

    uhf filter Hello Carrrier, Simple solution is that you have 2 bandpass filters at the input of MAR amplifier after separate antennas and after broadband amplifers combine its output with highpass and lowpass network to summing output port. Bandpass synthesis you can do in the Ansoft AD student...

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