Parameter encoder architecture

A channelized receiver having multiple sectors wherein each antenna of said receiver system is electronically connectable to any combination of sectors to improve the flexibility of said receiver. The bandwidth of each sector is electronically selectable adding further flexibility to the receiver mission. The signal characteristics of time of arrival, pulse amplitude and time of departure are processed digitally in real time and false pulses are eliminated through arbitration in real time. Remaining pulse calculations such as angle of arrival, frequency, pulse width and pulse repetition interval and environment filtering are not calculated in real time.

FIELD OF THE INVENTION 
This invention relates to the architecture of an RF channelized receiver 
capable of detecting multiple RF pulses of varying amplitude and frequency 
in multiple bandwidths and sectors. The configuration of the sectors is 
programmable so that one sector can have 24, 48, 72 or 96 individual 
channels to cover a programmable bandwidth. 
CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to U.S. Ser. No. 08/109,804, filed on Aug. 20, 
1993 entitled "Instantaneous Parameter Measuring Receiver", now U.S. Pat. 
No. 5,451,956 issued Sep. 19, 1995; U.S. Ser. No. 08/443,174 filed May 3, 
1995 entitled "Advanced Parameter Encoder with Dual Integrated Pulse 
Present Detection and Channel/Sector Arbitration", which is a 
continuation-in-part application of Ser. No. 08/154,906 filed Nov. 19, 
1993, now abandoned; U.S. Ser. No. 08/478,155 filed Jun. 7, 1995 entitled 
"Advanced Parameter Encoder with Pulse-On-Pulse Detection and Pulse 
Fragment Reconstruction" which is a continuation-in-part of U.S. patent 
application Ser. No. 08/154,908, filed Nov. 19, 1993, now abandoned; and 
U.S. Ser. No. 08/154,907 filed Nov. 19, 1993 entitled "Advanced Parameter 
Encoder with Environmental Filter Capability", now U.S. Pat. No. 5,477,227 
issued Dec. 19, 1995, all of which are hereby incorporated by reference. 
BACKGROUND OF THE INVENTION 
Electronic warfare systems are used on modern military aircraft as part of 
their offensive and defensive capabilities. These electronic warfare 
systems emit RF signals that travel through space. Radar systems use RF 
emissions to locate and track opposing aircraft and some radar systems are 
incorporated within missiles to assist in the self-guided propulsion of a 
missile to its target. An electronic warfare search receiver is used 
defensively to detect those RF emissions. The receiver searches the range 
of frequencies (the RF spectrum) in which the RF emissions are likely to 
occur. The receiver then detects and analyzes the nature of the RF 
signals. By determining the characteristics of the signals received, the 
defender will know the nature of the threat and, for example, will know if 
a radar guided missile has "locked on" to the defenders aircraft. These 
systems are used in friendly as well as unfriendly aircraft. In a tactical 
or strategic environment, the number of aircraft and the density and 
diversity of the emissions in the RF spectrum is quite large and is 
expected to increase. Existing and future aircraft and other platforms 
need advanced capability avionics in order to successfully perform and 
survive on future missions. There will be more electromagnetic emitters 
from friendly, allied and enemy sources and all of these sources must be 
detected, analyzed and sorted. These RF receivers need to be more 
available (longer mean time between failure) then ever before so that the 
equipment will perform on every mission because success can only be 
achieved if the aircraft has operating equipment. 
Channelized receivers are recognized as a preferred solution to provide 
very high probability of intercept even in extremely high density 
environments. They provide wide instantaneous bandwidth while maintaining 
dynamic range, high frequency resolution and direction finding 
capabilities. The channelized receiver achieves this performance by 
paralleling many narrow bandwidth receivers together into a coherent 
whole. However, true channelized receivers (processing the entire 
instantaneous bandwidth simultaneously) have generally been impractical to 
date. The RF and digital circuitry required to process 100 "receivers" is 
too large and heavy and consumes too much power. 
A small, lightweight, low power channelized receiver is needed to meet the 
needs of future tactical aircraft, helicopters and surveillance platforms. 
Also, a small channelized receiver is crucial for upgrading the electronic 
warfare (EW) capabilities of existing aircraft. 
It is unlikely that a single receiver type will be capable of meeting all 
offensive or defensive threat detection and analysis requirements dictated 
by the future electronic warfare environment. Instead a set of search and 
analysis receivers of complimentary capabilities are likely to be required 
to meet future demands. Trade offs between probability of intercept, 
bandwidth, simultaneous signal resolution, sensitivity, receiver 
complexity and power consumption are necessary. It would be advantageous 
to have a small lightweight, low power channelized receiver. Such a 
receiver could process signals digitally in real time and have the 
flexibility of being programmable so that various portions of the 
channelized receiver can be used for multiple purposes. In such a receiver 
it would useful to have the ability to eliminate all spurious signals 
while maintaining a high probability of intercepting real signals. 
SUMMARY OF THE INVENTION 
The invention is a method and architecture for building a small, 
lightweight and low power channelized receiver in which the analog RF 
information is converted to digital signals before processing. Analog 
sections of the channelized receiver such as an IF switch, the tuners and 
the channelizers are digitally controllable so that they can be 
electronically reconfigured to cover multiple sectors with electronically 
selectable bandwidth. The overall system is capable of measuring the 
signal parameters of RF pulses including frequency, time of arrival, pulse 
width, pulse amplitude and angle of arrival. To assist in identifying 
these pulse parameters, the present invention employs real time conversion 
of the log video signal to a digital signal which detects time of arrival 
(TOA), pulse amplitude (PA) and time of departure (TOD) of a pulse in real 
time. The receiver also has the capability of arbitrating between 
frequency channels and sectors in real time so that spurious signals can 
be eliminated in real time before pulse calculations such as angle of 
arrival, (AOA), frequency (F), pulse width (PW) and pulse repetition 
interval (PRI) can be calculated in non-real time. There are, for example, 
a total of 96 separate programmable channels in the system so that each 
channel in the channelized receiver has the capability of simultaneously 
processing individual signals in each channel and determining TOA, PA and 
TOD for each received signal. This aspect of the invention is accomplished 
by employing digital techniques that require low power consumption and 
more importantly that are programmable so that the function of the 
receiver can be changed electronically to meet the challenge of different 
mission requirements. The programmable nature of the receiver gives each 
channel the ability to look at a selectable bandwidth in addition to the 
ability to look for multiple types of pulses. In the spatial domain a 
receiver system may, for example, have four antennas each covering one 
sector or quadrant of space. However, because the sectors of the receivers 
are programmable, they can be electronically reconfigured so that the 
entire bandwidth capabilities of the receiver could be connected to one 
antenna giving that sector a large bandwidth coverage. 
Therefore, it is an object of the present invention to provide a 
channelized receiver, with a capability of detecting and differentiating 
between RF pulses, that is small, lightweight and has low power 
consumption. It is another object of the present invention to be able to 
digitally process the log video signals so that TOA, PA and TOD can be 
calculated in real time. It is another object of the invention to provide 
a receiver architecture employing channel and sector arbitration so that 
spurious signals can be eliminated from the data stream in real time 
thereby greatly reducing the amount of information upon which the 
calculations of AOA, F, PW and PRI are calculated. It is another object of 
the invention to provide modular expandability so that additional 
bandwidth (channels) and/or spatial coverage (sectors) can be added 
without altering the basic architecture of the receiver system. It is a 
further object of the present invention to provide a receiver architecture 
in which the sectors and bandwidth of the receiver are electronically 
programmable which will greatly increase receiver flexibility to meet 
varying mission requirements. 
The foregoing objects and advantages of the invention together with the 
structure and characteristics thereof, briefly summarized in the foregoing 
passages, become more apparent to those skilled in the art upon reading 
the detailed description of the preferred embodiment taken together with 
the following illustrations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is the architecture of a channelized receiver that 
converts a log video RF signal to digital information that is used to 
detect received RF pulses and to discriminate between real and spurious 
signals occurring in both the frequency and space domain. The processing 
of the pulses is all done digitally in real time for TOA, PA and TOD. 
Discriminating between real and spurious signals is also performed in real 
time. These features allow processing of information from 96 separate 
receiver channels each of which is responsible for monitoring its assigned 
bandwidth in its sector. 
FIG. 1 is an overall block diagram of a channelized receiver that would be 
employed in an aircraft to receive, detect and analyze RF signals from a 
variety of possible emission sources including enemy aircraft, enemy 
missiles and fixed radar locations. 
Turning now to FIG. 1, FIG. 1 is a block diagram of a channelized receiver 
in which the present invention can be used. This is an illustration of the 
type of receiver that would be suitable for the present invention although 
the present invention can be used in other types of receivers such as 
narrow band single-channel and interferometer receivers. Antennas 20, 22, 
24 and 26 represent the four antennas that would typically be used to 
cover 360.degree. of spatial domain surrounding an aircraft. Each antenna 
receives signals from approximately 90.degree. of azimuth air space to 
cover the entire 360.degree. range. The receivers 30 are identical and 
receive the signals intercepted by antennas 20-26. The receivers 30 are 
typically wide band, front end low noise amplifiers that are placed close 
to the antennas to minimize noise interference that could be introduced 
through long cable connections. Bus 40 is a command and control bus that 
is used to coordinate, control and reconfigure the overall function of the 
channelized receiver. Each output of the receiver is connected to an IF 
matrix switch 31 and then to a tuner 34. Local oscillator 32 is connected 
to each of the tuners 34 to provide the tuners with the ability to select 
IF frequency bands and down convert a bandwidth from, for instance, 6 to 7 
gigahertz for an individual receiver to 0.5-1.5 gigahertz. The output 
bandwidth of each tuner 34 is connected to one of the four channelizers 
36. The channelizers 36 consist of a number of adjacent band-pass filters 
that are used to discriminate between signals that may be contained in 
various frequencies across the spectrum selected by the IF tuner. Each of 
these band-pass filters can cover a frequency range of from, for example, 
20 to 100 MHz and typically will have a crossover with its adjacent filter 
at -1 dB of attenuation. The outputs of the channelizers are connected to 
the parameter encoder module 38 which is ultimately responsible for 
producing a pulse descriptor word for each separate signal that has been 
received across the frequency spectrum. The pulse descriptor word (PDW) 
which is a long digital word describing the individual characteristics of 
each received signal is transferred to an emitter identification processor 
46 that determines the nature and possible significance of any signal that 
is received. The emitter identification processor 46 then transfers 
information concerning the received signal to a cockpit display 48, for 
instance, or via line 50 to an aircraft controller. FIG. 1 is intended to 
identify an overall system in which the present invention is useful. 
FIG. 2 shows airplane 140 having antennas 142, 144, 146 and 148. Antenna 
142 has reception zone 150 which corresponds to one quadrant or sector. 
This sector is referred to as Sector A. Similarly, antennas 144, 146 and 
148 have reception zones 152, 154 and 156 respectively. These reception 
zones are respectively referred to Sectors B, C and D. Sector A has a -6 
dB crossover point with its neighboring sectors D and B identified as -6 
dB crossover points 164 and 158. In a similar manner, Sector B has -6 dB 
crossover points with its neighboring Sectors A and C. These are crossover 
points 158 and 160. Sector C has -6 dB crossover points 160 and 162 with 
its respective neighboring Sectors B and D and Sector D has -6 dB 
crossover points 162 and 164 with its neighboring Sectors C and A. With 
the antennas arranged in this manner, the airplane can detect incoming RF 
signals in a 360.degree. range. The antennas 142, 144, 146 and 148 
correspond to the antennas 20, 22, 24 and 26 respectively shown in FIG. 1. 
Arrow 166 represents an incoming RF signal that will impact Sector A at 
the zero dB point or bore sight. Arrow 168 also represents an incoming RF 
signal that will impact Sectors A and B at the -6 dB crossover point 158 
resulting in identical signals received in Sectors A and B. When the RF 
signal represented by arrow 166 is received by Sector A, a portion of the 
energy from that RF signal will also be received by Sectors D, B and C. 
Since there is only one signal, an arbitration must take place to 
determine which signal is the best signal to report. Similarly, when an RF 
signal is being received from a point represented by arrow 168, the system 
should only report one signal instead of reporting two. Discriminating 
between RF signals received in the various sectors is accomplished through 
sector arbitration which is done digitally in real time. 
Sectors A, B, C and D shown in FIG. 2 are also represented in FIG. 3 by the 
cylindrical diagram which has been divided into sectors with each sector 
having 24 channels, for example, the Sectors A, B, C and D in FIG. 3 
correspond to the Sectors A, B, C and D in FIG. 2. As shown in FIG. 3, 
Sector A numbered 134 has 24 channels. Sector B numbered 136 has 24 
channels as do Sectors C and D respectively numbered 138 and 132. As shown 
in diagram 170 in FIG. 3, each of the channels in Sectors A, B, C and D is 
responsible for detecting signals in a selected frequency band. Therefore, 
each of the Sectors A, B, C and D is capable of listening to 24 individual 
frequency bands. Three of those frequency bands are shown in breakaway 
sections 172, 174 and 176 which correspond to the three channels 5, 6 and 
7. Each of these channels have the same circuitry which includes a 
band-pass filter, a log video detection amplifier, an AD converter, pulse 
detection, arbitration and pulse measurement. In total there are 96 
channels or 24 channels in each sector. When a signal is received by 
channel A.sub.6, rabbit-ear signals will also be received in channels 
A.sub.5 and A.sub.7 which are adjacent in frequency to channel A.sub.6. 
The rabbit-ear signals received in channels A.sub.5 and A.sub.7 are not 
true signals and are rejected by employing arbitrations between channels 
A.sub.6 and A.sub.7 and A.sub.6 and A.sub.5. The arbitration involves 
integrating the amplitude of a predetermined number of amplitude samples 
occurring after the arrival of the pulses and then comparing those 
amplitude samples to the samples in the adjacent channels. The signal with 
the largest amplitude wins and the other signals are rejected and not 
reported in a PDW. This is accomplished in real time and allows the 
receiver to eliminate a great deal of spurious information before the 
steps of calculating the AOA, PW, F and PRI of a true signal. The ability 
to arbitrate between channel A.sub.6 and A.sub.5 and A.sub.7 in real time 
is a result of digital processing techniques. It would not be feasible to 
perform these arbitrations simultaneously in real time in 96 channels if 
the log video RF signal was not first converted to digital information. A 
similar arbitration is also performed between each of the sectors A.sub.6, 
B.sub.6, C.sub.6 and D,. Sector arbitration is accomplished in the same 
way as channel arbitration except that sector arbitration takes place 
between each of the sectors instead of just with adjacent neighbors as in 
channel arbitration. The specific method of accomplishing this arbitration 
is disclosed in the application "Advanced Parameter Encoder with Dual 
Integrated Pulse Present Detection and Channel/Sector Arbitration" which 
has been incorporated herein by reference. A further aspect of the present 
invention will now be described with reference to FIGS. 4 and 5. 
In FIG. 4, Sector A has been numbered 62 and Sector B has been numbered 64. 
As shown in FIG. 4, each of the Sectors A and B now has 48 adjacent 
channels to cover the frequency spectrum. This realignment of the 
reception ability of the receiver is accomplished electronically in IF 
switch 31 shown in FIG. 1. In this instance, antenna 20 could be 
electronically connected through IF switch 31 to two of the tuners 34 and 
another antenna 22 could be electronically connected to the remaining two 
tuners 34. The tuners 34 would then select the contiguous frequency 
bandwidths which would be transmitted to the 48 receiver channels 
available to each antenna. In this instance, if it was known that a 
particular threat would be on the right side of the aircraft, Sectors A 
and B could cover 180.degree. on the right side of the aircraft with a 
drastically increased frequency detection bandwidth. Again, this ability 
to switch bandwidth and receiver channels between sectors greatly adds to 
the receiver flexibility and mission capability of the present invention. 
In FIG. 5, Sector A has been numbered 60 and represents channels 1-96. In 
this instance, antenna 20 has been electrically connected through IF 
switch 31 to all four of the tuners 34. The tuners 34 select the 
contiguous frequency bands of interest and then down convert. All 96 
channels of the receiver are connected to one antenna. This allows the 
airplane to monitor a vast frequency spectrum in one quadrant which could 
be useful in situations such as detection of frequency agile signals. The 
receiver can be just as easily switched back to a 360.degree. reception 
mode by electrically manipulating the connections in IF switch 31. 
FIG. 6 is a detailed block diagram showing the novel architecture of the 
present invention and its implementation in a channelized receiver. 
Antennas 66, 68, 70 and 72 are connected respectively to the wide band, 
front-end, frequency converters 74, 76, 78 and 80 respectively. Attempts 
are made to keep a short distance between the inputs of the amplifiers 74, 
76, 78 and 80 and their respective antennas 66, 68, 60 and 72 to eliminate 
noise problems that may occur due to long cable connections. This has the 
effect of reducing the noise floor and increasing receiver sensitivity. 
The outputs of the amplifiers 74, 76, 78 and 80 are connected to an 
electronically programmable IF switch 82. The output of the IF switch 82 
is connected to electronically programmable tuners 84, 86, 88 and 90. 
Local oscillators 92 are connected to each of the tuners 84, 86, 88 and 90 
for allowing the tuners to select the IF frequency and down convert the 
bandwidth of interest to the final IF center frequency. Each of the 
front-ends 74, 76, 78 and 80 can be connected to any combination of tuners 
84, 86, 88 and 90. This is an important aspect of the invention because 
each of the tuners 84, 86, 88 and 90 correspond to one sector of the 
channelized receiver. Each of the sectors as previously discussed has 24 
channels each of which has its own bandwidth which represents 1/24th of 
the bandwidth output of its associated tuner. Therefore, antenna 66 and 
its associated front-end can be connected to any combination of sectors. 
In this manner, sector bandwidth can be programmably controlled as desired 
for the particular mission involved. For instance, one quadrant of the 
airplane can be connected to 24 channels, 48 channels, 72 channels or 96 
channels. Other options include connecting each of two adjacent sectors to 
48 channels which could be used to give one side of the plane superior 
bandwidth over a 180.degree. range. 
All outputs of the channelizers 94, 96, 98 and 100 are connected to 
logrithmic amplifier detectors 101. At this point it is important to note 
that the channelizers convert the bandwidth of the tuners from I channel 
to 24 separate channels that equally divide the bandwidth output of the 
tuners. Therefore, there are 96 logrithmic amplifier detectors 101 which 
are connected to channelizers 94, 96, 98 and 100. Similarly, there are 96 
A/D converters 102 and 96 pulse detectors 104. There are also 96 
arbitration modules 106 which are used to arbitrate between both channels 
and sectors. Both channel and sector arbitration was discussed with 
reference to FIG. 3. The digital approach allows arbitrations to take 
place between neighboring channels and between each of the sectors. The 
sector arbitration is spatially oriented and the channel arbitration is 
frequency oriented. The channel arbitration is designed to eliminate 
rabbit-ears and noise induced signals and the sector arbitration is 
designed to eliminate backlobe problems as well as spill-over energy from 
a signal that is received in more than one sector. Since there is only one 
emitter source, only one pulse will be selected after the arbitration is 
complete. 
The A/D converter 102 converts pulse amplitude information to a digital 
signal which represents the instantaneous amplitude present in the 
channel. This instantaneous amplitude is sampled on a periodic basis such 
as every 20 nanoseconds or every 50 nanoseconds. The digital processing of 
these signals allows simultaneous digital arbitration which eliminates a 
great number of spurious signals and insures that reported pulse 
descriptor words will contain important information about real signals 
that have been received. After the arbitration is complete, the digital 
information representing the received pulse is transferred to the 
parameter measurement block 110. This block determines the TOA, PA and TOD 
of a particular signal. This determination is made in real time which 
allows accurate and consistent representation of those parameters. There 
are 96 of the parameter measurement modules 110. Parameter calculations 
such as AOA, F, PW and PRI are made in parameter calculator 112. In 
addition, each parameter calculator can perform an environment filter 
function. The environment filter screens output PDW's for signals of 
interest and rejects signals not of interest. At this stage in the 
architecture the 96 outputs of the parameter measurement modules 110 are 
combined in fours to produce, for example, 24 outputs. Eight of these 
outputs are combined together and there are three parameter calculation 
modules 112 each having eight inputs and one output. The parameter 
calculators are not required to calculate their pulse parameters in real 
time in order to reduce the number of resources thereby reducing cost, 
weight and power. The parameter calculators 112 connect in cascade either 
as a funnel or as a parameter calculator. When they are used as a 
calculator they are used to determine the AOA, F, PW and PRI of a pulse 
and to screen pulses by the environment filter. When they are used as a 
funnel, they are used to consolidate the outputs of the quad combined 
parameter measurement modules 110. Each of the parameter calculators 112 
has eight inputs and one output. The outputs of the 24 quad combined 
parameter measurement modules 110 are connected to three parameter 
calculators 112 each having eight inputs and one output. The outputs of 
the three parameter calculators 112 are connected to another parameter 
calculator 112. A way of consolidating the outputs of the pulse 
measurement modules 110 and parameter calculators 112 is shown in FIG. 7. 
FIG. 7 shows 12 of the A/D converts 102, the pulse detectors 104, the 
arbitration modules 106 and the pulse measurement modules 110. 
FIG. 7 shows the 96 parameter measurement modules 110 are consolidated into 
four parameter calculators 112. As stated before, the parameter 
calculators 112 can act either as a funnel or as a calculator. When they 
are acting as a funnel they are multiplexing the pulse information 
received from the pulse measurement modules 110 and consolidating it by 
multiplexing the information. Pulse calculations can occur at any and all 
levels of the system. The tradeoffs involved are that less bandwidth is 
involved at levels closer to the pulse measurement modules 110. This 
allows higher resolution for calibration of the parameter calculation 
functions. However, this method also requires significantly more data to 
be down-loaded at all levels increasing programming and change-over time 
for the system. 
The unique aspects of this receiver architecture are its all-digital 
processing of amplitude data and its ability to stack sectors with either 
24, 48, 72 or 96 channels. The other unique aspect of this architecture is 
the ability to separate real time calculations of TOA, PA and TOD from 
non-real time calculations of AOA, F, PW and PRI and environment 
filtering. The all-digital approach allows simultaneous arbitration in 
real time for all sectors and channels which greatly reduces the number of 
pulse descriptor words giving the receiver both a high probability of 
intercept and a low false alarm rate. 
It is believed that the foregoing description or the preferred embodiment 
of the invention is sufficient in detail to enable one skilled in the art 
to make and use the invention. However, it is expressly understood that 
the details of the elements that are presented are not intended to limit 
the scope of the invention inasmuch as equivalence to those elements and 
other modifications thereof all of which come within the scope of the 
invention, become apparent to those skilled in the art upon reading this 
specification. Thus, the invention is to be broadly construed within the 
full scope of the appended claims.