7
Explanation of Test Points
All measurements were taken using the “Continuous
Transmit” or “Continuous Receive” features of the PTU
diagnostic software. Unless otherwise noted, spectrum
measurements included in this section were obtained using
a Hewlett-Packard 54006A 500
Ω
probe and 11742A coaxial
blocking capacitor and do not indicate the actual amplitude
of the signal owing to losses associated with the probe.
Unless noted, 11Mbps CCK modulation was employed.
Many of the signals are differential (i.e., balanced with
respect to ground). These are denoted by + (plus) and
- (minus) symbols following the signal name (e.g., RX I+ and
RX I-).
Test Points A- A1, and B-B1
Transmit I and Q:
NOTE: BPSK mode is used for the plots in this figure. Therefore, I
and Q are identical.
The I and Q are both differential signals and, as such,
consist of I+, I-, Q+, and Q- respectively. As these are
balanced signals, data is measured using a Tektronix P6247
Differential Probe. For example in the measurement of the I
signal, the probe is bridged between Test Points A (I+) and
A1 (I-).
Transmit In-phase and Quadrature (I+ and Q+) signals are
the spread baseband single-bit I and Q digital data that are
outputted at the programmed chip rate (N).
Test Points C and D
IF Transmit Signal:
The intermediate frequency (IF) transmit signal is a spread
spectrum signal centered at 374MHz with a 17MHz
bandwidth.
The SAW filter is used to shape the sidelobes.
Test point C is at the input of the SAW Filter whereas D is at
the output.
FIGURE 4. TRANSMIT I AND Q SIGNALS AT THE OUTPUT
OF THE HFA3861 (TEST POINTS A-A1 AND B-B1)
FIGURE 5. IF TRANSMIT SIGNAL BEFORE SAW FILTER
(TEST POINT C)
FIGURE 6. IF TRANSMIT SIGNAL AFTER THE SAW FILTER
(TEST POINT D)
Application Note 9864
