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# TRF3705: Maximum bandwidth of the IQ modulator output RF signal

Part Number: TRF3705
Other Parts Discussed in Thread: TRF370417

Hi Team,

The TRF3705 IQ modulator datasheet states that its 1-dB input frequency bandwidth is 1000MHz. Does this IQ modulator output RF signal with a bandwidth of up to 2000MHz?

Thanks,

Annie

• Hi Annie,

1000MHz is the total bandwidth covered and supported by the TRF3705 overall. It is also known as the complex quadrature bandwidth (I and Q signal supporting 1000MHz).

• Hi Hsia,

The data sheet of TRF370417 IQ modulator also states that its 1-dB input frequency bandwidth is 1000MHz. However, in section 7.3 of the data sheet, it is stated that a 2GHz bandwidth RF signal can be generated using the full baseband bandwidth. Customer would like to know how to understand it?

Thanks,

Annie

• Hi Annie,

Please allow us to double check this internally.

• Yes, the TRF3705 supports a baseband bandwidth of 1 GHz corresponding to an RF BW of 2 GHz.  The baseband I/Q (in-phase and quadrature-phase) paths each support ~0Hz to 1 GHz.  When those paths are combined in the modulator and up-converted by the LO, you will get double the baseband bandwidth.  The output RF spectrum will be LO +/- 1 GHz for a composite 2 GHz total bandwidth.

--RJH

• Hi RJH,

Does the baseband I/Q path support negative frequencies? For example -500MHz to 500MHz band, the center frequency is 0Hz?

Thanks,

Annie

• Hi Annie,

TRF3705 and TRF370417 are complex quadrature modulators and can support 0Hz center IF (i.e. direct zero IF upconversion).

• Hi RJH,

May I ask how the baseband I/Q of TRF3705 is combined, and can double the baseband bandwidth when upconverted by the LO? Or is the output RF bandwidth of the IQ modulator always 2x the I/Q baseband bandwidth?

Thanks,

Annie

• Hi Annie,

Typically, with the direct upconversion with message signal m(t) and Hilbert transform mh(t) of bandwidth B, your final upconverted signal will have 2*B of total bandwidth. Below is the generic equation for most of the I/Q modulators.