CA1337945C - Weighted channelized receiver - Google Patents
Weighted channelized receiverInfo
- Publication number
- CA1337945C CA1337945C CA 611460 CA611460A CA1337945C CA 1337945 C CA1337945 C CA 1337945C CA 611460 CA611460 CA 611460 CA 611460 A CA611460 A CA 611460A CA 1337945 C CA1337945 C CA 1337945C
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- signal
- signals
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- intermediate frequency
- separate
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/021—Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Mathematical Physics (AREA)
- Superheterodyne Receivers (AREA)
Abstract
An apparatus and a method of detecting simultaneously received separate frequency signals in an input signal comprising subjecting representations of the input signal separately to various time or amplitude weighting to exaggerate differences between various ones and others of the separate frequency signals, passing individual exaggerated difference various ones of the separate frequency signals through separate limiters to exaggerate one separate frequency signal relative to the others in each of the various separate frequency signals, and measuring the frequency of each exaggerated one frequency signal.
Description
01 This invention relates to a receiver for 02 separating or sorting simultaneously received signals.
03 Instantaneous frequency measurement (IFM) 04 receivers have been developed for use in electronic 05 warfare, to effect electronic support measures, 06 electronic counter measures, or electronic 07 intelligence applications. Instantaneous frequency 08 measurement receivers are variously known in the art 09 as Digital Instanteous Frequency Measurement (DIFM) receivers or Digital Frequency Discriminators (DFD).
11 DIFM receivers are typically required to operate in 12 dense and complex electromagnetic signal 13 environments. It is therefore desirable that the 14 receivers should be capable of separating individual ones of plural simultaneously received signals from 16 single or multiple emitters.
17 U.S. Patent 4,791,360 issued 18 December 13th, 1988 and assigned to Telemus Electronic 19 Systems Inc. describes prior art DIFM systems which use a discriminator to separate a signal from an input 21 signal and a delayed representation of the input 22 signal. However such prior art systems could only 23 provide the strongest one of simultaneous signals, and 24 in some circumstances, in the event a second signal arrives prior to completion of the frequency 26 measurement of a first signal and the second signal is 27 stronger than the first, there is a significant 28 likelihood of an erroneous output signal.
29 To overcome that problem in the invention described in that patent the received signals are 31 successively applied to respective signal modifying 32 circuits, each for isolating a predetermined one of 33 the received signals from the other one of the 34 signals, and an output signal is generated corresponding to the isolated one of the simultaneous 36 signals separated in time and frequency from the other 37 ones of the signals. Either similar amplitude ones of ,~
1 3~794~
_ 01 the separated signals are filtered and amplified, 02 while the others are attenuated, or time coincident 03 ones of the simultaneous signals are dispersively 04 delayed by predetermined lengths of time proportionate 05 to their respective frequencies. In such a system, 06 the successive application of the received signals to 07 respective ones of the plurality of signal modifying 08 means requires the use of a switching circuit.
09 For input signals which use pulse lengths longer than n times the switching circuit switching 11 time, and where the switch dwell period is long enough 12 for the frequency measurements to be made to the 13 desired accuracy, the patented system has been found 14 to be satisfactory, especially where there is a single received signal with multiple pulsed frequencies.
16 However it has been found that if the duration of the 17 input signal is short relative to the switching time, 18 or if there is a need to handle more than one received 19 signal at a time, the patented system can be improved. The present invention is an improved system 21 which can handle more than one received signal at a 22 time, and can operate successfully if the duration of 23 the received signal is short compared to the required 24 switching time of the patented system.
In accordance with the present invention, 26 the received signal is power divided into a plurality 27 of separate signals, each containing ~he simultaneous 28 signals. Each separate signal is passed through a 29 weighting means, each weighting means for receiving one of the separate signals and for translating it so 31 as to exaggerate differences between various ones and 32 others of the simultaneous signals. The weighting 33 means can be dispersive delay lines, filters, 34 amplifiers, channelizers, etc. Each of the weighting-biased translated signals is passed through 36 a limiter, which further exaggerates the maximum 37 amplitude one of the simultaneous signals relative to 1 33~945 01 the others. Each of the resulting signals is passed 02 through a frequency measurement circuit, such as a 03 discriminator, pulse counter or halver which selects 04 the maximum amplitude signal corresponding to its 05 channel. In the case of the frequency disciminator, 06 it is followed by an A/D converter or digitizer. In 07 the case of the pulse counter that output is in 08 digital format. The halver can be used prior to the 09 discriminator or pulse counter to prescale the signal frequency, but its operation as a threshold device 11 also helps to separate the strongest signal. The 12 outputs of the counters or A/D converter are applied 13 to a latch, or latches. The output signal, 14 representing the frequencies of the simultaneously received signals, are n bit words representing the 16 frequencies of the simultaneous signals, and are 17 preferably compared to data stored in a software 18 library to match the n bit latched words, and thereby 19 sort and identify the received signal and thus its emitter.
21 More particularly, an embodiment of the 22 invention is a method of detecting simultaneously 23 received separate frequency signals in an input signal 24 comprising subjecting representations of the input signal separately to various time or amplitude 26 weighting to exaggerate differences between various 27 ones and others of the separate frequency signals, 28 passing individual exaggerated difference various ones 29 of the separate frequency signals through separate limiters to exaggerate one separate frequency signal 31 relative to the others in each of the various separate 32 frequency signals, and measuring the frequency of each 33 exaggerated one frequency signal.
34 Another embodiment of the invention is a signal detection apparatus comprising apparatus for 36 receiving an input signal comprised of a plurality of 37 simultaneous signals of different frequencies, a power 01 divider for dividing the input signal into a plurality 02 of separate signals each containing the simultaneous 03 signals, a plurality of weighting means each for 04 receiving one of the separated signals and for 05 translating it so as to exaggerate differences between 06 various ones of the simultaneous signals, a plurality 07 of limiting apparatus each for receiving one of the 08 translated signals and for further exaggerating the 09 amplitude of a maximum amplitude one of the simultaneous signals relative to the others, and 11 frequency measurement means for receiving the further 12 exaggerated signals for distinguishing each of the 13 maximum amplitude signal signals.
14 A better understanding of the invention will be obtained by reference to the detailed 16 description below, with reference to the following 17 drawings, in which:
18 Figure 1 is a block schematic of a system 19 in accordance with an embodiment of the present invention, 21 Fiqure 2 is a block schematic of a portion 22 of the circuit of Figure 1 modified in accordance with 23 another embodiment, and 24 Figure 3 is a block schematic of a portion of the circuit of Figure 1 modified in accordance with 26 another embodiment of the invention.
27 Turning to Figure 1, an input signal is 28 received at input 1 where it is applied to an n-way 29 power divider 2. The outputs of the power divider define various channels. The input signal is 31 comprised of several simultaneous signals of different 32 frequencies, as shown on the graph 3, which 33 illustrates the signals as vertical bars on a set of 34 axes having an abscissa f representing frequency and an ordinate a representing amplitude.
36 The separate signals resulting from power 37 division of the input signal are each applied in a 01 corresponding channel to a weighting means 4A, 02 4B, . . . 4 (N-2), 4 (N-l ) and 4N. The weighting means 03 perform different weighting functions to the separate 04 signals. Each of the weighting means can be an 05 amplitude vs frequency weighting filter, or a time vs 06 frequency weighting filter, such as a dispersive delay 07 line.
08 Representative translation characteristics 09 of the weighting means are shown within the blocks 4A-4N. Representatives of the resulting weighted 11 signals are shown at the outputs of the blocks 4A-4N, 12 and it can be seen that there has been exaggeration of 13 the amplitudes of different frequency signals in 14 accordance with the weighting functions. It is the purpose of the weighting means to exaggerate 16 differences between various ones and others of the 17 simultaneous signals in each of the channels defined 18 by the outputs of the power divider 2.
19 The weighted signals in each channel are 20 applied to a corresponding limiter, or limiting 21 amplifier 5A-5N. AS iS known in the art, the limiting 22 amplifier further exaggerates the amplitude of the 23 highest amplitude one of the simultaneous signals 24 applied to it relative to the others. The result is shown in the amplitude vs frequency graphs at the 26 output of limiting amplifiers 5A-5N. One signal at 27 one frequency in each channel is of significantly 28 higher amplitude than the remaining ones.
29 The further exaggerated signals in each channel are applied to a corresponding discriminator 31 or pulse counter 6A-6N, where the highest amplitude 32 one of the further exaggerated signals is selected, 33 providing an output in each channel to a corresponding 34 A/D converter 7A-7N if discriminators are used. The discriminators and pulse counters constitute a 36 frequency measurement unit 8, which can be in the form 37 of a digital frequency discriminator and counter as 1 3~7945 01 described above, or other apparatus to measure the 02 frequency of the highest amplitude separate frequency 03 component of the output signal of the limiting 04 amplifier in each channel.
05 The outputs of the frequency measurement 06 unit 8, each constituting an n-bit word designating 07 the frequency of the highest amplitude signal, are 08 applied to a latch 9. The total latched data word is 09 preferably applied to a memory 10 for access by a processor 11 which can control the comparison of the 11 latched or stored word with another word stored in 12 memory, thus to identify the input signal.
13 It should be noted that each of the 14 channels can be gated into the latch all at once, or sequentially, depending on the preference of the 16 designer for its application (sequentially, in the 17 time vs frequency weighted case), and either the word 18 representing the channel data, or the complete data 19 word representing all the channels, compared with data stored in the memory.
21 Since the above-described system does not 22 use a switch, as is required in the system described 23 in the aforenoted patent, the problem of the time 24 differences between the leading edge of individual pulses of different signals being smaller than the 26 switching time of the switch has been substantially 27 eliminated. In addition, plural signals, rather than 28 only a single one as in earlier types of systems, can 29 be distinguished by frequency.
In addition, the problem in prior art 31 systems being unable to distinguish signals due to the 32 shadow time (the time between the presence of the 33 signal and the time of determining the presence of 34 that signal, at which time the signal to be determined may already be absent) is substantially reduced.
36 In case there is a problem with standing 37 waves between the power divider and the weighting 1 3~9~
01 means 4A-4N, for example for signals between 2 and 4 02 GHz, a variation of the system shown in Figure l can 03 be used, as illustrated in Figure 2. In this 04 instance, between the power divider 2 and each 05 weighting means 4A-4N an isolator 12A-12N is 06 connected. Preferably in the case of a pulse form of 07 input signal a bandpass filter or isolation filter 08 13A-13N is connected between each isolator and each 09 output of the power divider 2. The filter and isolator substantially decrease the VSWR, thus 11 substantially decreasing or eliminating reflected 12 signals. The remainder of the system is as described 13 with respect to Figure l.
14 Figure 3 illustrates another embodiment of the system shown in Figure 1, in which the signals 16 applied to the weighting means are at intermediate 17 frequencies, and therefore may be referred to as the 18 superheterodyne version of the present invention. An 19 input signal at input 14 is applied to a mixer 15 with an output signal from a first local oscillator 16.
21 The resulting up or down-converted intermediate 22 frequency band signal is applied to an intermediate 23 frequency amplifier 17, the output of which is applied 24 as the input signal at input 1 to the power divider 2. The divided separate output signals, which are 26 within the first intermediate frequency band are 27 applied to corresponding second mixers 18A-18N to 28 which individual second local oscillator signals LO
29 are applied. The resulting up or down-converted output signals from local oscillators 18A-18N are 31 applied to the corresponding weighting means 4A-4N in 32 the individual channels. If desired, narrow bandwidth 33 bandpass filters can be connected between the outputs 34 of the mixers 18A-18N and the weighting means 4A-4N.
The local oscillator 16, which can be a 36 switched local oscillator, can be varied for coarse 37 frequency adjustment. Either separately or in unison 01 each of the second local oscillator signals can be 02 varied for fine frequency adjustment. This can allow 03 adjustment of the input signals to the weighting means 04 so that the maximum output of a particular frequency 05 signal can be obtained, and in particular the input 06 signals can be positioned relative to the weighting 07 means for maximum efficiency. Indeed, the local 08 oscillator signals could be fast switched relative to 09 the weighting filters' transfer functions so as to improve the probability of distinguishing particular 11 signals.
12 In this embodiment the intermediate 13 frequency bandwidth can be narrower than in the 14 previously described embodiments. This allows the use of narrow bandpass filters between the mixers 18A-18N
16 and the weighting means, thus improving the 17 performance against simultaneous signals which are 18 close together in frequency and phase, as well as 19 reducing the noise floor by modifying kTP, where K is Boltsman constant, T is temperature in degrees Kelvin, 21 and B is the bandwith. With the use of narrow 22 bandpass filters, the weighting means can have high 23 transfer function slopes, and narrow bandwidth, which 24 decreases the effective noise bandwidth, and increases the signal to noise ratio. An additional advantage of 26 this embodiment is a relatively low cost of lower 27 frequency components which would be used to process 28 the lower down converted second intermediate frequency 29 signal.
It should be noted that the frequency band 31 to be sorted can be expanded, e.g. from 2-4 GHZ to 32 2-18 GHZ by connecting a mixer 15 in series with a 33 linear amplifier 17 in series with the input 1, as 34 shown to the left of the vertical dashed line in Figure 2. A local oscillator 16 provides a local 36 oscillator signal to mixer 1, which receives the input 37 signal. The converted signal is applied to the input 01 of power divider 2. A switch 20 bypasses the mixer 02 and linear amplifier to allow the input signal to pass 03 straight into the power divider 2. With the switch 04 open, various bands (e.g. 4-6 GHZ etc.) can be 05 down-converted into the frequency ranges of the 06 filters 13A-13N, or weighting means 4A-4N.
07 While the frequency band of the 08 intermediate frequency signal in one embodiment should 09 span the same frequency band as the weighting means, in another embodiment, it can overlap the frequency 11 band of the weighting means, and be subject to 12 variation or rapid change, in order to fit the 13 received signals best to the weighting means, or to 14 facilitate identification or sorting thereof. The filters and isolators can be dispensed with, if VSWR
16 is not a problem or if pulse signals are not to be 17 received, as in the embodiment of Figure 1.
18 The present invention can provide 19 intrapulse frequency measurement so that discrete and integrated frequency measurement can be made. The 21 combination of these two parameters, especially on 22 complex input signals, is believed to be a powerful 23 signal sorting and identification tool. It should 24 also be noted that since various weighting means are used having differing slopes or delays, multiple 26 simultaneous signals from one or more sources can be 27 measured.
28 Numerous other applications and other 29 embodiments may now occur to a person skilled in the art understanding this invention. All such 31 modifications and embodiments falling within the scope 32 of the claims are considered to be part of the present 33 invention.
34 _ 9 _
03 Instantaneous frequency measurement (IFM) 04 receivers have been developed for use in electronic 05 warfare, to effect electronic support measures, 06 electronic counter measures, or electronic 07 intelligence applications. Instantaneous frequency 08 measurement receivers are variously known in the art 09 as Digital Instanteous Frequency Measurement (DIFM) receivers or Digital Frequency Discriminators (DFD).
11 DIFM receivers are typically required to operate in 12 dense and complex electromagnetic signal 13 environments. It is therefore desirable that the 14 receivers should be capable of separating individual ones of plural simultaneously received signals from 16 single or multiple emitters.
17 U.S. Patent 4,791,360 issued 18 December 13th, 1988 and assigned to Telemus Electronic 19 Systems Inc. describes prior art DIFM systems which use a discriminator to separate a signal from an input 21 signal and a delayed representation of the input 22 signal. However such prior art systems could only 23 provide the strongest one of simultaneous signals, and 24 in some circumstances, in the event a second signal arrives prior to completion of the frequency 26 measurement of a first signal and the second signal is 27 stronger than the first, there is a significant 28 likelihood of an erroneous output signal.
29 To overcome that problem in the invention described in that patent the received signals are 31 successively applied to respective signal modifying 32 circuits, each for isolating a predetermined one of 33 the received signals from the other one of the 34 signals, and an output signal is generated corresponding to the isolated one of the simultaneous 36 signals separated in time and frequency from the other 37 ones of the signals. Either similar amplitude ones of ,~
1 3~794~
_ 01 the separated signals are filtered and amplified, 02 while the others are attenuated, or time coincident 03 ones of the simultaneous signals are dispersively 04 delayed by predetermined lengths of time proportionate 05 to their respective frequencies. In such a system, 06 the successive application of the received signals to 07 respective ones of the plurality of signal modifying 08 means requires the use of a switching circuit.
09 For input signals which use pulse lengths longer than n times the switching circuit switching 11 time, and where the switch dwell period is long enough 12 for the frequency measurements to be made to the 13 desired accuracy, the patented system has been found 14 to be satisfactory, especially where there is a single received signal with multiple pulsed frequencies.
16 However it has been found that if the duration of the 17 input signal is short relative to the switching time, 18 or if there is a need to handle more than one received 19 signal at a time, the patented system can be improved. The present invention is an improved system 21 which can handle more than one received signal at a 22 time, and can operate successfully if the duration of 23 the received signal is short compared to the required 24 switching time of the patented system.
In accordance with the present invention, 26 the received signal is power divided into a plurality 27 of separate signals, each containing ~he simultaneous 28 signals. Each separate signal is passed through a 29 weighting means, each weighting means for receiving one of the separate signals and for translating it so 31 as to exaggerate differences between various ones and 32 others of the simultaneous signals. The weighting 33 means can be dispersive delay lines, filters, 34 amplifiers, channelizers, etc. Each of the weighting-biased translated signals is passed through 36 a limiter, which further exaggerates the maximum 37 amplitude one of the simultaneous signals relative to 1 33~945 01 the others. Each of the resulting signals is passed 02 through a frequency measurement circuit, such as a 03 discriminator, pulse counter or halver which selects 04 the maximum amplitude signal corresponding to its 05 channel. In the case of the frequency disciminator, 06 it is followed by an A/D converter or digitizer. In 07 the case of the pulse counter that output is in 08 digital format. The halver can be used prior to the 09 discriminator or pulse counter to prescale the signal frequency, but its operation as a threshold device 11 also helps to separate the strongest signal. The 12 outputs of the counters or A/D converter are applied 13 to a latch, or latches. The output signal, 14 representing the frequencies of the simultaneously received signals, are n bit words representing the 16 frequencies of the simultaneous signals, and are 17 preferably compared to data stored in a software 18 library to match the n bit latched words, and thereby 19 sort and identify the received signal and thus its emitter.
21 More particularly, an embodiment of the 22 invention is a method of detecting simultaneously 23 received separate frequency signals in an input signal 24 comprising subjecting representations of the input signal separately to various time or amplitude 26 weighting to exaggerate differences between various 27 ones and others of the separate frequency signals, 28 passing individual exaggerated difference various ones 29 of the separate frequency signals through separate limiters to exaggerate one separate frequency signal 31 relative to the others in each of the various separate 32 frequency signals, and measuring the frequency of each 33 exaggerated one frequency signal.
34 Another embodiment of the invention is a signal detection apparatus comprising apparatus for 36 receiving an input signal comprised of a plurality of 37 simultaneous signals of different frequencies, a power 01 divider for dividing the input signal into a plurality 02 of separate signals each containing the simultaneous 03 signals, a plurality of weighting means each for 04 receiving one of the separated signals and for 05 translating it so as to exaggerate differences between 06 various ones of the simultaneous signals, a plurality 07 of limiting apparatus each for receiving one of the 08 translated signals and for further exaggerating the 09 amplitude of a maximum amplitude one of the simultaneous signals relative to the others, and 11 frequency measurement means for receiving the further 12 exaggerated signals for distinguishing each of the 13 maximum amplitude signal signals.
14 A better understanding of the invention will be obtained by reference to the detailed 16 description below, with reference to the following 17 drawings, in which:
18 Figure 1 is a block schematic of a system 19 in accordance with an embodiment of the present invention, 21 Fiqure 2 is a block schematic of a portion 22 of the circuit of Figure 1 modified in accordance with 23 another embodiment, and 24 Figure 3 is a block schematic of a portion of the circuit of Figure 1 modified in accordance with 26 another embodiment of the invention.
27 Turning to Figure 1, an input signal is 28 received at input 1 where it is applied to an n-way 29 power divider 2. The outputs of the power divider define various channels. The input signal is 31 comprised of several simultaneous signals of different 32 frequencies, as shown on the graph 3, which 33 illustrates the signals as vertical bars on a set of 34 axes having an abscissa f representing frequency and an ordinate a representing amplitude.
36 The separate signals resulting from power 37 division of the input signal are each applied in a 01 corresponding channel to a weighting means 4A, 02 4B, . . . 4 (N-2), 4 (N-l ) and 4N. The weighting means 03 perform different weighting functions to the separate 04 signals. Each of the weighting means can be an 05 amplitude vs frequency weighting filter, or a time vs 06 frequency weighting filter, such as a dispersive delay 07 line.
08 Representative translation characteristics 09 of the weighting means are shown within the blocks 4A-4N. Representatives of the resulting weighted 11 signals are shown at the outputs of the blocks 4A-4N, 12 and it can be seen that there has been exaggeration of 13 the amplitudes of different frequency signals in 14 accordance with the weighting functions. It is the purpose of the weighting means to exaggerate 16 differences between various ones and others of the 17 simultaneous signals in each of the channels defined 18 by the outputs of the power divider 2.
19 The weighted signals in each channel are 20 applied to a corresponding limiter, or limiting 21 amplifier 5A-5N. AS iS known in the art, the limiting 22 amplifier further exaggerates the amplitude of the 23 highest amplitude one of the simultaneous signals 24 applied to it relative to the others. The result is shown in the amplitude vs frequency graphs at the 26 output of limiting amplifiers 5A-5N. One signal at 27 one frequency in each channel is of significantly 28 higher amplitude than the remaining ones.
29 The further exaggerated signals in each channel are applied to a corresponding discriminator 31 or pulse counter 6A-6N, where the highest amplitude 32 one of the further exaggerated signals is selected, 33 providing an output in each channel to a corresponding 34 A/D converter 7A-7N if discriminators are used. The discriminators and pulse counters constitute a 36 frequency measurement unit 8, which can be in the form 37 of a digital frequency discriminator and counter as 1 3~7945 01 described above, or other apparatus to measure the 02 frequency of the highest amplitude separate frequency 03 component of the output signal of the limiting 04 amplifier in each channel.
05 The outputs of the frequency measurement 06 unit 8, each constituting an n-bit word designating 07 the frequency of the highest amplitude signal, are 08 applied to a latch 9. The total latched data word is 09 preferably applied to a memory 10 for access by a processor 11 which can control the comparison of the 11 latched or stored word with another word stored in 12 memory, thus to identify the input signal.
13 It should be noted that each of the 14 channels can be gated into the latch all at once, or sequentially, depending on the preference of the 16 designer for its application (sequentially, in the 17 time vs frequency weighted case), and either the word 18 representing the channel data, or the complete data 19 word representing all the channels, compared with data stored in the memory.
21 Since the above-described system does not 22 use a switch, as is required in the system described 23 in the aforenoted patent, the problem of the time 24 differences between the leading edge of individual pulses of different signals being smaller than the 26 switching time of the switch has been substantially 27 eliminated. In addition, plural signals, rather than 28 only a single one as in earlier types of systems, can 29 be distinguished by frequency.
In addition, the problem in prior art 31 systems being unable to distinguish signals due to the 32 shadow time (the time between the presence of the 33 signal and the time of determining the presence of 34 that signal, at which time the signal to be determined may already be absent) is substantially reduced.
36 In case there is a problem with standing 37 waves between the power divider and the weighting 1 3~9~
01 means 4A-4N, for example for signals between 2 and 4 02 GHz, a variation of the system shown in Figure l can 03 be used, as illustrated in Figure 2. In this 04 instance, between the power divider 2 and each 05 weighting means 4A-4N an isolator 12A-12N is 06 connected. Preferably in the case of a pulse form of 07 input signal a bandpass filter or isolation filter 08 13A-13N is connected between each isolator and each 09 output of the power divider 2. The filter and isolator substantially decrease the VSWR, thus 11 substantially decreasing or eliminating reflected 12 signals. The remainder of the system is as described 13 with respect to Figure l.
14 Figure 3 illustrates another embodiment of the system shown in Figure 1, in which the signals 16 applied to the weighting means are at intermediate 17 frequencies, and therefore may be referred to as the 18 superheterodyne version of the present invention. An 19 input signal at input 14 is applied to a mixer 15 with an output signal from a first local oscillator 16.
21 The resulting up or down-converted intermediate 22 frequency band signal is applied to an intermediate 23 frequency amplifier 17, the output of which is applied 24 as the input signal at input 1 to the power divider 2. The divided separate output signals, which are 26 within the first intermediate frequency band are 27 applied to corresponding second mixers 18A-18N to 28 which individual second local oscillator signals LO
29 are applied. The resulting up or down-converted output signals from local oscillators 18A-18N are 31 applied to the corresponding weighting means 4A-4N in 32 the individual channels. If desired, narrow bandwidth 33 bandpass filters can be connected between the outputs 34 of the mixers 18A-18N and the weighting means 4A-4N.
The local oscillator 16, which can be a 36 switched local oscillator, can be varied for coarse 37 frequency adjustment. Either separately or in unison 01 each of the second local oscillator signals can be 02 varied for fine frequency adjustment. This can allow 03 adjustment of the input signals to the weighting means 04 so that the maximum output of a particular frequency 05 signal can be obtained, and in particular the input 06 signals can be positioned relative to the weighting 07 means for maximum efficiency. Indeed, the local 08 oscillator signals could be fast switched relative to 09 the weighting filters' transfer functions so as to improve the probability of distinguishing particular 11 signals.
12 In this embodiment the intermediate 13 frequency bandwidth can be narrower than in the 14 previously described embodiments. This allows the use of narrow bandpass filters between the mixers 18A-18N
16 and the weighting means, thus improving the 17 performance against simultaneous signals which are 18 close together in frequency and phase, as well as 19 reducing the noise floor by modifying kTP, where K is Boltsman constant, T is temperature in degrees Kelvin, 21 and B is the bandwith. With the use of narrow 22 bandpass filters, the weighting means can have high 23 transfer function slopes, and narrow bandwidth, which 24 decreases the effective noise bandwidth, and increases the signal to noise ratio. An additional advantage of 26 this embodiment is a relatively low cost of lower 27 frequency components which would be used to process 28 the lower down converted second intermediate frequency 29 signal.
It should be noted that the frequency band 31 to be sorted can be expanded, e.g. from 2-4 GHZ to 32 2-18 GHZ by connecting a mixer 15 in series with a 33 linear amplifier 17 in series with the input 1, as 34 shown to the left of the vertical dashed line in Figure 2. A local oscillator 16 provides a local 36 oscillator signal to mixer 1, which receives the input 37 signal. The converted signal is applied to the input 01 of power divider 2. A switch 20 bypasses the mixer 02 and linear amplifier to allow the input signal to pass 03 straight into the power divider 2. With the switch 04 open, various bands (e.g. 4-6 GHZ etc.) can be 05 down-converted into the frequency ranges of the 06 filters 13A-13N, or weighting means 4A-4N.
07 While the frequency band of the 08 intermediate frequency signal in one embodiment should 09 span the same frequency band as the weighting means, in another embodiment, it can overlap the frequency 11 band of the weighting means, and be subject to 12 variation or rapid change, in order to fit the 13 received signals best to the weighting means, or to 14 facilitate identification or sorting thereof. The filters and isolators can be dispensed with, if VSWR
16 is not a problem or if pulse signals are not to be 17 received, as in the embodiment of Figure 1.
18 The present invention can provide 19 intrapulse frequency measurement so that discrete and integrated frequency measurement can be made. The 21 combination of these two parameters, especially on 22 complex input signals, is believed to be a powerful 23 signal sorting and identification tool. It should 24 also be noted that since various weighting means are used having differing slopes or delays, multiple 26 simultaneous signals from one or more sources can be 27 measured.
28 Numerous other applications and other 29 embodiments may now occur to a person skilled in the art understanding this invention. All such 31 modifications and embodiments falling within the scope 32 of the claims are considered to be part of the present 33 invention.
34 _ 9 _
Claims (19)
1. Signal detection means comprising:
(a) means for receiving an input signal comprised of a plurality of simultaneous signals of different frequencies, (b) a power divider for dividing the input signal into a plurality of separate signals each containing said simultaneous signals, (c) a plurality of weighting means each for simultaneously receiving one of the separate signals and for translating it so as to exaggerate differences between various ones of said simultaneous signals, (d) a plurality of limiting means each for receiving one of the translated signals and for further exaggerating the amplitude of a maximum amplitude one of said simultaneous signals relative to the others, and (e) frequency measurement means for receiving the further exaggerated signals for distinguishing each of the maximum amplitude signal signals.
(a) means for receiving an input signal comprised of a plurality of simultaneous signals of different frequencies, (b) a power divider for dividing the input signal into a plurality of separate signals each containing said simultaneous signals, (c) a plurality of weighting means each for simultaneously receiving one of the separate signals and for translating it so as to exaggerate differences between various ones of said simultaneous signals, (d) a plurality of limiting means each for receiving one of the translated signals and for further exaggerating the amplitude of a maximum amplitude one of said simultaneous signals relative to the others, and (e) frequency measurement means for receiving the further exaggerated signals for distinguishing each of the maximum amplitude signal signals.
2. Signal detection means as defined in claim 1 in which the weighting means is an amplitude vs frequency weighting filter.
3. Signal detection means as defined in claim 1 in which the weighting means is a time vs frequency weighting filer.
4. Signal detection means as defined in claim 1 in which the weighting means is a dispersive delay line.
5. Signal detection means as defined in claim 1, 2, 3 or 4 in which the frequency measurement means is comprised of a plurality of discriminators each for receiving a corresponding signal from a limiting amplifier and for providing a signal corresponding to the maximum exaggerated maximum amplitude one of the simultaneous signals applied thereto.
6. Signal detection means as defined in claim 1, in which the frequency measurement means is comprised of a plurality of discriminators each for receiving a corresponding signal from a limiting amplifier and for providing a signal corresponding to the maximum exaggerated maximum amplitude one of the simultaneous signals applied thereto, and a plurality of analog to digital converters connected to outputs of corresponding discriminators each for providing a digital word indicating the frequency of a corresponding discriminated signal.
7. Signal detection means as defined in claim 6, further including a latch connected to the outputs of the analog to digital converters for temporarily storing digital words representing each of the frequencies of the discriminated signals.
8. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising an isolator interposed between each output of the power divider and an input of a corresponding weighting means.
9. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising a filter in series with an isolator interposed between each output of the power divider and an input of a corresponding weighting means.
10. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising a first mixer for converting a first signal to a first intermediate frequency signal and for applying the first intermediate frequency signal as the input signal to the receiving means, and a plurality of second mixers interposed between the power divider and corresponding weighting means for converting the first signal to a plurality of second intermediate frequency signals for application to corresponding weighting means as said separate signals.
11. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising a first mixer for converting a first signal to a first intermediate frequency signal and for applying the first intermediate frequency signal as the input signal to the receiving means, and a plurality of second mixers interposed between the power divider and corresponding weighting means for converting the first signal to a plurality of second intermediate frequency signals for application to corresponding weighting means as said separate signals, separate local oscillator signals which are separately variable being applied to each of the second mixers.
12. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising a first mixer for converting a first signal to a first intermediate frequency signal and for applying the first intermediate frequency signal as the input signal to the receiving means, and a plurality of second mixers interposed between the power divider and corresponding weighting means for converting the first signal to a plurality of second intermediate frequency signals for application to corresponding weighting means, and means for applying separate local oscillator signals to each of the second mixers and rapidly varying the frequencies thereof.
13. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7 further comprising a first mixer for converting a first signal to a first intermediate frequency signal and for applying the first intermediate frequency signal as the input signal to the receiving means, and a plurality of second mixers interposed between the power divider and corresponding weighting means for converting the first signal to a plurality of second intermediate frequency signals for application to corresponding weighting means, local oscillator signals having similar frequencies being applied to each of the second mixers.
14. Signal detection means as defined in claim 1, 2, 3, 4, 6 or 7, further comprising a first mixer for receiving a local oscillator signal and converting a first signal to a first intermediate frequency signal and applying the first intermediate frequency signal as the input signal to the receiving means, the intermediate frequency signal spanning the same frequency band as the weighting means.
15. A method of detecting simultaneously received separate frequency signals in an input signal comprising subjecting representations of the input signal separately and simultaneously to various time or amplitude weighting to exaggerate differences between various ones and others of said separate frequency signals, passing individual exaggerated difference various ones of said separate frequency signals through separate limiters to exaggerate one separate frequency signal relative to the others in each of the various separate frequency signals, and measuring the frequency of each exaggerated one frequency signal.
16. A method as defined in claim 15, including the step of translating the input signal to intermediate frequency narrow band signals prior to subjection to said weighting.
17. A method as defined in claim 16, including the step of varying the intermediate frequency of the narrowband signals relative to a weighted frequency transfer function.
18. A method as defined in claim 15, including the step of translating the input signal to an intermediate frequency signal spanning the same frequency band as the weighting means.
19. A method as defined in claim 15 including the step of translating the input signal to an intermediate frequency signal overlapping the same frequency band as the weighting means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 611460 CA1337945C (en) | 1989-09-14 | 1989-09-14 | Weighted channelized receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 611460 CA1337945C (en) | 1989-09-14 | 1989-09-14 | Weighted channelized receiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1337945C true CA1337945C (en) | 1996-01-16 |
Family
ID=4140595
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 611460 Expired - Fee Related CA1337945C (en) | 1989-09-14 | 1989-09-14 | Weighted channelized receiver |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1337945C (en) |
-
1989
- 1989-09-14 CA CA 611460 patent/CA1337945C/en not_active Expired - Fee Related
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