User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–10
IFD Wide Dynamic Range Parameters
Channel separation: 20.00 dB, 0.0 deg
Maximum deviation : 0.50 dB, 5.0 deg
Overlap/Interpolate interval: 30.00 dB
The Channel Separation and Overlap/Interpolate Interval should be determined
from the Pr printout described below. Sweep a SigGen across the shared power
region of the two channels to determine a representative channel separation, along
with the size of the overlap region at the top of the HiGain channel within which that
separation remains steady and constant, i.e., unaffected by eventually approaching the
noise floor of the LoGain channel.
The RVP8 continually measures and updates the complex channel separation during
normal operation. Ratios of echoes that fall within the overlap/interpolate interval
are averaged over several minutes, thereby tracking gain and phase variations that
occur with temperature changes and component aging. If the channel separation ever
exceeds the specified maximum deviation, the GI4S_IFDCHANERR bit (11) will be
set in GPARM Immediate Status Word #4.
TAG bits to invert AZ:0000 EL:0000
TAG scale factors AZ:1.0000 EL:1.0000
TAG offsets (degrees) AZ:0.00 EL:0.00
The incoming TAG input bits may be selectively inverted via each of the 16-bit
words. The values are displayed in Hex. Setting a bit will cause the corresponding
AZ (bits 0–15) or EL (bits 16–31) lines to be inverted. Note that the SOPRM
command also specifies TAG bits to invert. Both specifications are XOR’ed together
to yield the net inversion for each TAG line.
The overall operations are performed in the order listed. Incoming bits are first
inverted according to the two 16-bit XOR masks. This yields an unsigned 16-bit
integer value which is then multiplied by the signed scale factor. The result is
interpreted as a 16-bit binary angle (in the low sixteen bits), to which the offset angle
is finally added.
As an example, suppose that the elevation angle input to the RVP8 was in an
awkward form such as unsigned integer tenths of degrees, i.e., 0x0000 for zero
degrees, 0x000a for one degree, 0x0e06 for minus one degree, etc. If we apply a
scale factor of 65536/3600 = 18.2044 to these units, we will get 16-bit binary angles
in the standard format. If we further suppose that the input angle rotated
“backwards”, we could take care of this too using a multiplier of –18.2044.
Interference Filter – 0:None, Alg.1, Alg.2, Alg.3: 1
Threshold parameter C1: 10.00 dB
Threshold parameter C2: 12.00 dB
The RVP8 can optionally apply an interference filter to remove impulsive-type noise
from the demodulated (I,Q) data stream. See Section 5.1.5 for a complete description
of this family of algorithms.