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Recent content by Ghost Tweaker

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    Impedance matching on-chip

    Hi all, I was wondering if someone could explain me why it is often mentioned that impedance matching is not required onchip. What I currently uderstand is that: - impedance matching does lead to maximum power transfer but not to maximum voltage transfer. - for max. voltage transfer, zero...
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    Circuit equivalent to 4557D

    4557d Hi everyone, I'm designing a distortion pedal. In the schematic there's a dual opamp labelled 4557D. However, I can't find information on this device on the web. Does anyone know the complete name of this device or a possible replacement? Thanx in advance for the help Ghostea
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    Receiver gain planning for spread spectrum/low SNR system

    Hi everone, I was wondering how one defines the required gain for a receiver when the signal SNR is negative, which is the case for example for spread spectrum coms. My current understanding is that knowing the system bandwidth, one can determine the noise power at the system input. Then...
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    analg implementation of raised cosine filter

    Hi everyone, I want to drive a VCO with some digital data in order to implement FSK modulation. To do so I first need to apply some filtering to the data, ideally with a raised cosine filter. I'm in the analog discrete world though? any recommendation of which filter type and order I should...
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    FilterGroup delay impact on binary-offset-carrier modulation

    Binary offset carrier (BOC) modulation is equivalent to taking a standard modulation (BPSK, BFSK, ...) and apply a second FSK-like modualtion. Now i was wondering about the impact of the group delay introduced by the front-end filters on the receiver's performances? Indeed if the two lobes of...
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    complexe conjugate vs "bridging" impedance matchin

    Re: complexe conjugate vs "bridging" impedance mat Yes biff I do agree with you, I'm trying to get some more input on the subject. I think a general rule of thumb may be that when the distance between components is short as compared to the signal wavelength, we can switch from conjugate...
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    complexe conjugate vs "bridging" impedance matchin

    Hi everyone, I was wondering if someone has a good explanation or article about when we should use complexe conjugate or bridging impedance matching (bridging is used for low output impedance seeing a high impedance to maximize voltage transfer). Regards Ghost
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    Model for finger touching a microstrip

    Thanks rfmw, so the model would be to add a capapcitor to ground at the contact point. Do you agree?
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    Model for finger touching a microstrip

    No I don't mean to debug. What I mean is that I have a transmission line opened at one end and it behaves as a capacitor whose value is controlled by design. Now I'm wondering what is the equivalent circuit of this same line once a finger touches it? Thanks for your help
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    Model for finger touching a microstrip

    Hi everyone, I would like to know how you guys would model a microstrip with a finger touching the microstrip? The microstrip is connected at one end to a circuit and serves as a variable C/L. The variation occrs when a finger touches the strip. To model this, should I consider the strip is...
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    VCO requirement in the GPS system?

    GPS is spread spectrum modulation (there's no bands, just one common band with all the signals on top of each other) so you just design for a fixed frequency which ensures downconversion of the GPS signal to the IF you have chosen.
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    noise floor measurement using spectrum analyzer

    noise floor of a spectrum analyzer In the case of 1Hz RBW you have the power spectral density or equivalently the power in 1Hz. In the 1.5MHz case you are integrating the power spectral density over 1.5MHz which is equivalent to adding 10*log(1.5e6) = 60dB gain Also when making such...
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    Question about system gain planning in a wireless receiver

    Re: IP3 question Bolin, I fully understand that they are not the same but which one should I use in this case? Should I consider each stage's IIP3 individually with the signals present at its input or can simply consider the receiver's IIP3 with the signals present at the input of the receiver...
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    Question about system gain planning in a wireless receiver

    Re: IP3 queation Thank you vfone this was helpfull. I have one last question: is the IIP3 value found the IIP3 of the first component of the receiver or that of the complete system? Thanks for your help
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    Determine system's required IP3 from interference mask

    I'm not confident with the two following points: 1) the margin is quite large probably 3dB would be sufficient. 2) Is there a direct relation between the interference mask and the system's P1dB or IP3? My approach would be to say that: inband: the system's input P1dB should be higher than...
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