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1-30MHz upconverting mixer

Hello AD, which mixer solution would you suggest for upconverting 1-30MHz or if possible 1-70MHz by approx. 120MHz to approx. 121-190MHz (analog to analog)? I can only find AD8343, an older generation part which has not been characterised at these frequencies with performance data. The AD8342 seems to be specified as downconverter only, and possibly not down to 1MHz. Are there any other AD options to consider?

  • Hello,

    The AD8343 can use as up converter as well, please take a look at the data sheet pages 13 & 14.

    Here is another option if you want to use an active mixer ADL5801.

    You can also use a passive mixer as the ADL5350

    Thank you,

    Assaf

  • Hi, Bernard,

        The AD8342 has an IF bandwidth of about 500 MHz, and it can be used as upconverter for any frequency within this range using the characterization circuit shown in Fig. 38 on the datasheet (p. 13), without additional matching.  Performance such as conversion gain and IP3, etc., will be similar to the downconversion case (e.g., Flatness shown in Fig. 6, on p. 8).

        If the mixer is located far away (> 0.1 wavelength) from the load, then it would be best to back-terminate the mixer output with a 100 ohm resistor to eliminate reflections.  IN this case the conversion gain will be lower by 6 dB.

    Benjamin

  • Hello Assaf, my second-to-last sentence was referring to the AD8342. Your other part suggestions do not seem to be specified for the desired RF Frequency Range (starting at 1MHz).

  • Hello Benjamin, thanks for your reply. For the AD8342 used as upconverter, it seems that the RF port should still be the input (as opposed to the IF port, which is suggested for some mixers in such upconverter applications).

    Would you suggest the AD8342 above the AD8343 for this application? Does the AD8342 really require no matching with inputs down to 1MHz? Other options at this stage include the LTC5510 and LT5560; these need input matching at the low frequencies.

    We now want to use IN=1-180MHz and LO=220MHz.

  • Hi, Bernard,

        All those mixers have DC coupled RF & IF ports, and therefore will work for you frequency range.  They are designed differently, and the relative merits depend on the details of your application needs.

    The AD8342 is the most general-purposed mixer, with high input impedance that can be (need to be) terminated with almost any impedance.  It has reasonable input common-mode rejection, and is double-balanced, leading to good leakage specs below 2 GHz.

    The ADL5350 uses the least power (3V, 19 mA), but without any balancing, and the large RF and LO signals must be filtered from the IF output.  It's a passive mixer, so it will give you the lowest noise figure, roughly equal to its insertion loss.

    The ADL5801 has a wide frequency range (6 GHz) and high dynamic range, also double-balanced, and is probably our top-of-the-line active mixer.  It takes more supply current than the other parts.  There is an internal differential termination resistance of 250 ohm.

    The AD8343 is a small double-balance mixer, that requires less supply current than the 8342.  The inputs have a low differential impedance 95.6 ohm), so series termination will generally be needed. There is no input common-mode rejection, and a balun is needed at the input.

    I would suggest to start with the AD8342, but should also check to see if you need the benefits from the other mixers instead.

    One word of caution about your frequency range: the LO leakage (220 MHz) will be very close to your upconverted IF output (221-400 MHz?).  A mixer with low LO leakage plus good IF filtering may be important to prevent LO leakage and mixer spurs from interfering with your desired output.

    Benjamin

  • Hi, Bernard,

    Regarding the AD8343, I meant to say that

        "The inputs have a low differential impedance of 5.6 ohms"

    Benjamin

  • Hello Benjamin, if output spurs levels are a priotity, we should be preferring the ADL5801 out of the list, do you agree?

    Based on your reply I conclude that the specified RF Frequency Range minimum of 10MHz for the ADL5801 therefore pertains more to the input impedance. Would it be possible to suggest input matching circuits for our stated frequencies?

    PS. According to this thread, the ADL5801 is not rated down to DC: ADL5801   Up Convertion mode with DC-50 MHz RF input

    ???

  • Hi, Bernard,

        I  wasn't very clear about the ADL5801:

        The ADL5801 will operate down to DC on the RF input. The input is DC coupled with a 50-ohm differential termination. The gain does drop starting below about 4MHz by about 3dB. It then levels out down to DC with a gain of -1dB.  The output impedance is 230 ohm differentially.

        If you can live with the gain change below 4 MHz then the ADL5801 will be good.  The AD8342 does stay flat to DC (flatness determined by DC blocking caps, etc.), but needs an external input termination resistor.

        For many of the RF parts, we do not usually characterize them below 10 MHz, mostly because the baluns we use on the characterization boards start to roll off below 10 MHz.

    Benjamin

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    EZ Admin