atr0797-6cph ATMEL Corporation, atr0797-6cph Datasheet - Page 3

• Manufacturer Part Number: atr0797-6cph
• Description: 65-300 Mhz Sige If Receiver Demodulator - Atmel Corporation
• Manufacturer: ATMEL Corporation

Product Description
4665D–SIGE–08/04
Atmel’s ATR0797 is a variable gain I-Q demodulator designed for use in receiver IF sec-
tions, that are typically existing in superheterodyne RF architectures.
The ATR0797 has two gain stages that are independent of each other. These gain
stages are broadband differential amplifiers each with a digital control pin to set the
gain. Since the amplifiers have approximately the same gain, setting GC1 high and GC2
low results in approximately the same gain as setting GC1 low and GC2 high. Former
setting offers better noise figures.
The IF input is a differential input that has internal bias circuitry to set the common mode
voltage. The use of blocking capacitors to facilitate AC coupling is highly recommended
to avoid changing the common mode voltage. Either input may be driven single ended if
the other input is connected to ground through an AC short such as a 1000 pF capacitor.
This typically results in slightly lower input P1dB.
The two matched mixers are configured with the quadrature LO generator to provide in-
phase and quadrature baseband outputs.
The LO and IF ports offer a differential 50 Ω impedance. The passives at these ports
(parallel L-R network) and the package itself adds inductance that tends to degrade
return loss.
The ATR0797 features immunity from changes in LO power. The gain features change
by less than 0.6 dB over a 6 dB range of LO power. Also note the excellent I/Q balance,
which typically falls within 0.1 dB and 1 degree from 65 MHz to 300 MHz, and varies
less than 0.05 dB and 0.5 degree over temperature (-40°C to +85°C).
The frequency response of the IF and LO ports is dominated by the L-R network on the
input. When de-embedded, the gain and P1dB response is within 0.5 dB from 65 MHz to
300 MHz.
The figures in the datasheet illustrate a typical ATR0797’s performance with respect to
temperature. Note that these numbers include the effect of the R-L network in the IF
port.
Evaluation board design and equipment constraints:
Please take into account that the evaluation board uses baluns on the I/Q outputs, and
these baluns limit the low frequency response of the device. For true baseband opera-
tion, the baluns should be removed, and the differential signals used directly.
The 27 pF capacitor on the evaluation board is appropriate for lower frequencies.
ATR0797
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