Based on the discovery of an extremely
power efficient, low component count (DAC low pass filters are unnecessary), low
distortion, current mode method of DAC RF upconversion/transmission, the company's
flagship products, the CRF2100 and CRF2101 are specifically designed to operate
within the compliance limits of industry standard, current mode Digital to Analog
Converters (see Primary Application).
With their low headroom capability, these mixers
can operate within the output compliance limits of current mode Digital to Analog
Converters and directly reuse DAC output currents for RF upconversion, thus reusing
analog signal current and saving overall system power. Also, if properly configured,
use of the CRF2100 and CRF2101 with the choice of an appropriate Zero IF or Homodyne
frequency plan (contact CurrentRF for more details), can allow DSP and converter
chips to run at lower clock rates, thus cutting the dynamic power these chips would
draw if they were clocked at higher clock rates. This lowering of system clock rates
also serves to enhance the dynamic performance of the Converter chips used in these
systems, in that lower clock rates give converters longer to settle, thus enhanced
The only filtering necessary when using
the CRF2100/CRF2101 upconversion solution is an output bandpass filter, which can
be realized as standard industry SAW, Ceramic, or lumped element filters.
The CRF2100 and CRF2101 may also be used in demanding
receive mode/downconversion applications. With the use of an appropriate current
mode LNA or a standard LNA with an output transconductance cell, these mixers, used
in a Zero IF fashion, can serve to efficiently downconvert incoming RF to baseband
signals. Again, as with the transmit solution, CRF2100 or the CRF2101 mixers may
be stacked between supply rails with the current mode LNA or standard LNA with an
output transconductance cell for maximum system power efficiency.
With an appropriate baseband VGA amplification and
low pass filtering, these baseband signals may be digitized by any industry standard
Analog to Digital Converter for further digital processing.
The transmit/receive solutions described above,
may be combined into an efficient transceiver solution that utilizes only one CRF2100
or CRF2101 mixer. With an appropriate current mode switching solution at the output
of the CRF2100 or CRF2101 mixer, the current source inputs of the CRF2100 or CRF2101
may be current multiplexed from the transmit DAC during transmit mode or the transconductance
cell of an LNA during receive mode. Current steering from the mixer outputs into
the appropriate balun/filter for transmit/receive modes is the only additional component
necessary to complete this system.