U2794B_08 Datasheet, PDF (12/15 Pages) ATMEL Corporation – 1000-MHz Quadrature Demodulator

7. Description of the Evaluation Board
Board material: epoxy; εr = 4.8, thickness = 0.5 mm, transmission lines: Z_O = 50Ω
The board offers the following functions:
• Test circuit for the U2794B:
– The supply voltage and the control inputs GC, PC, and PU are connected via a plug
strip. The control input voltages can be generated via external potentiometers; then
the inputs should be AC-grounded (time requirements in burst mode for power up
have to be considered).
– The outputs I, IX, Q, QX are DC coupled via an plug strip or can be AC-connected
via SMB plugs for high frequency tests e.g. noise figure or s-parameter
measurement. The Pins II, IIX, QQ, QQX allow user-definable filtering with 2
external capacitors CII, CQQ.
– The offsets of both channels can be adjusted with two potentiometers or resistors.
– The LO and the RF-inputs are AC-coupled and connected via SMB plugs. If
transmission line T3 is connected to the RF-input and AC-grounded at the other end,
gain and noise performance can be improved (input matching to 50Ω).
– The complementary RF-input is AC-coupled to GND (CRFX = 1 nF), the same
appears to the complementary LO input (CNLO = 1 nF).
• A calibration part which allows to calibrate an s-parameter analyzer directly to the in- and
output- signal ports of the U2794B.
• For single-ended measurements at the demodulator outputs, two OPs (e.g., AD620 or other)
can be configured with programmable gain; together with an output-divider network
RD = 450Ω to RL = 50Ω, direct measurements with 50Ω load impedances are possible at
frequencies t < 100 kHz.
12 U2794B
4653F–CELL–11/08