Analog Devices AD9273, AD9272 Using The Integrated Crosspoint Switch Cw Doppler Mode, UG-001

UG-001

Adjusting the Amplitude of the Input Signal

Next, adjust the amplitude of the input signal for each channel as follows:

1.Adjust the amplitude of the input signal so that the fundamental is at the desired level. (Examine the Fund Power reading in the left panel of the VisualAnalog FFT window.) If the gain pin voltage is too low, it is not possible to reach full scale without distortion. Use a higher gain setting or a lower input level to avoid distortion. This also depends on the PGA gain setting, which can be 30 dB,

27 dB, 24 dB, or 21dB. See Figure 15 and Figure 16.

07782-026

Figure 15. VisualAnalog, Graph Window

07782-027

Figure 16. VisualAnalog, Formatted FFT Plot

2.Repeat this procedure for the other seven channels.

3.Click the disk icon within the Graph window to save the performance plot. See Figure 17 for an example.

Evaluation Board User Guide

	0
					fIN = 3.5MHz @ –1dBFS
	–10
					LNA = 6×
	–20				VGAIN = 1V
	–30				FILTER TUNED
					HPF = 700kHz
(dBFS)	–40
	–50
AMPLITUDE	–60
	–70
	–80
	–90
	–100
	–110							-07782119
	–120
	–130
		5	10	15		20	25
	0

FREQUENCY (MHz)

Figure 17. Typical FFT, AD9272/AD9273

USING THE INTEGRATED CROSSPOINT SWITCH (CW DOPPLER MODE)

To examine the spectrum of the CW Doppler integrated crosspoint switch output, use the following procedure:

1.Complete the steps in the Configuring the Board and Using the Software for Testing sections to ensure that the board is set up correctly.

2.Optionally, remove the voltage source from the gain pin. It does not affect the CW Doppler output.

3.Connect the dc voltage source to P601, connecting the −5 V pin, the 0 V ground pin, and the +5 V pin as shown in Figure 1. These benchtop linear supplies should each have 100 mA of current capability.

4.Place jumpers on the top pin pairs of P606 or P607 to connect CWD2+/CWD2− to CWD5+/CWD5− to the IOP/ION buses. This directs each of these connections to the output amplifier for display.

Note that the CWD0±/CWD1±/CWD6±/CWD7± outputs are configured and biased to interface with the AD8339 evaluation board. The AD9272/AD9273 is specially designed to snap onto the AD8339 evaluation board to allow the user to evaluate a larger portion of this common signal chain. For detailed instructions about enabling this function, send an email to highspeed.converters@analog.com.

5.Use a 1 m, shielded, RG-58, 50 Ω coaxial cable to connect the spectrum analyzer to J402 (labeled AOUT on the evaluation board).

6.In the ADCBase 0 tab of the SPI Controller, find the MODES(8) box. Select the CW Mode option (see Figure 18).

Rev. 0 Page 10 of 24