User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–20
Burst Freq Estimator– Length: 1.33 usec, Start: 0.00 usec
This estimator is mostly used with the Pb (plotting commands) and can be referenced
in Section 4.3.2.
FIR-Filter prototype passband width: 0.503 MHz
This is the passband width of the ideal lowpass filter that is used to design the
matched FIR bandpass filter. The actual bandwidth of the final FIR filter will depend
on 1) the filter’s impulse response length, and 2) the design window used in the
process. The actual 3dB bandwidth will be:
S Larger than the ideal bandwidth if that bandwidth is narrow and the FIR length is
too short to realize that degree of frequency discrimination. In these cases it may
be reasonable to increase the filter length.
S Smaller than the ideal bandwidth if the FIR length easily resolves the frequency
band. This is because of the interaction within the filter’s transition band of the
ideal filter and the particular design window being used. For example, for a
Hamming window and sufficiently long filter length, the ideal bandwidth is an
approximation of the 6dB (not 3dB) attenuation point. Hence, the 3dB width is
narrower than the ideal prototype width.
This parameter should be tuned using the TTY output and interactive visual plot from
the “Ps” command. The actual 3dB bandwidth is shown there, so that it can be
compared with the ideal prototype bandwidth.
Limits: 0.05 to 10.0 MHz.
Output control 4–bit pattern: 0001
These are the hardware control bits for this pulsewidth. The bits are the 4-bit binary
pattern that is output on PWBW0:3
Bit Limits: 0 to 15 (input must be typed in decimal)
Current noise level: –75.00 dBm
Powerup noise level: –75.00 dBm
–or–
Current noise levels – PriRx: –75.00 dBm, SecRx: –75.00 dBm
Powerup noise levels – PriRx: –75.00 dBm, SecRx: –75.00 dBm
These questions allow you to set the current value and the power-up value of the
receiver noise level for either a single or dual receiver system. The noise level(s) are
shown in dBm, and you may alter either one from the TTY. The power-up level(s)
are assigned by default when the RVP8 first starts up, and whenever the RESET
opcode is issued with Bit #8 set. Likewise, the current noise level is revised
whenever the SNOISE opcode is issued. These setup questions are intended for
applications in which the RVP8 must operate with a reasonable default value, up until
the time that an SNOISE command is actually received. They may also be used to
compare the receiver noise levels during normal operation, which serves as a check
that each FIR filter is behaving as expected when presented with thermal noise.