CA1225159A - Signal discriminator - Google Patents
Signal discriminatorInfo
- Publication number
- CA1225159A CA1225159A CA000224005A CA224005A CA1225159A CA 1225159 A CA1225159 A CA 1225159A CA 000224005 A CA000224005 A CA 000224005A CA 224005 A CA224005 A CA 224005A CA 1225159 A CA1225159 A CA 1225159A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- unanimity
- output signal
- log
- binary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/04—Details
- G01S3/043—Receivers
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Noise Elimination (AREA)
Abstract
ABSTRACT
A signal discriminator is disclosed for use with a listening array, for detecting the presence of a signal coming from a predetermined direction against a background of noise.
Signals from the receivers in the array applied to a unanimity circuit which detects the occurrence of unanimity, which is when all the signals are of the same sense. When a coherent signal is present the probability of unanimity occurring is greater than when it is absent. A computer is included which receives signals from the unanimity circuit and analyses them, preferably using sequential sampling technique, to determine whether or not unamity is occurring with a probability high enough to indicate the presence of a coherent signal, and indicates the presence or absence of a signal accordingly.
A signal discriminator is disclosed for use with a listening array, for detecting the presence of a signal coming from a predetermined direction against a background of noise.
Signals from the receivers in the array applied to a unanimity circuit which detects the occurrence of unanimity, which is when all the signals are of the same sense. When a coherent signal is present the probability of unanimity occurring is greater than when it is absent. A computer is included which receives signals from the unanimity circuit and analyses them, preferably using sequential sampling technique, to determine whether or not unamity is occurring with a probability high enough to indicate the presence of a coherent signal, and indicates the presence or absence of a signal accordingly.
Description
~22~S9 This invention relates to listening arrays for detecting a signal coming from a predetermined direction against a background of incoherent noise, and signal discriminators for use in connection with such arrays.
The principle of a listening array is that an array of receivers is provided which is arranged so that any signal coming from the required predetermined direction will be received by all the receivers in phase, whereas any signal coming from a substantially different direction will be received with a phase difference between different receivers. This may be achieved merely by suitably placing the receivers or by incorporating delaying means into the receivers. The receivers are connected to a signal discriminator which is constructed to detect a component of the total signal received by each of the receivers which is in phase at all of the receivers and to reject components which are not in phase at all of the receivers.
In some applications it is required to recover the signal in order to extract information from it and in other applications it is only necessary to detect whether there is a signal coming from the given direction. This invention is concerned with listening arrays suitable for use in the latter type of application.
An object of the present invention is to provide a listening array with improved directionality and/or noise rejection over listening arrays of conventional type. A further object is to provide a signal discriminator for use in a listening array using digital techniques.
According to the present invention there is provided a ok ~;22S~
signal discriminator suitable for use with a listening array comprising a unanimity circuit capable of receiving a plurality of input signals and constructed to derive a binary 1 output signal whenever the input signals are all simultaneously of the same sense and a binary O output signal whenever the input signals are not all simultaneously of the same sense, and computing means connected to receive as input the output signals of the unanimity circuit and constructed to derive an output signal indicating signal detection if the rate of occurrence of binary 1 signals is high enough to satisfy a predetermined statistical criterion and to derive an output signal indicating no signal detection if the said rate is not high enough to satisfy the said criterion.
The statistical criterion may be derived from sequential sampling technique according to statistical sampling theory.
The signal discriminator may be constructed to receive binary digital input signals in which case the unanimity circuit may be constructed to produce a binary 1 output signal when all the input signals are binary 1 signals and also when all the input signals are binary O signals and to produce a binary O output signal in all other cases. It may for instance comprise an AND
gate and a NOR gate each connected to receive as inputs the input signals, the outputs of the AND and NOR gates being connected as inputs to an OR gate so what if the input signals are denoted by Al, A .~. AN the Output signal is constructed according to Al, A I. AN
Alternatively the signal discriminator may be constructed to receive analog input signals in which case the unanimity circuit may be constructed to produce a binary 1 output 5~S~3 signal when all the input signals are positive and also when all the input signals are negative and to produce a binary 0 output signal in all other cases.
The use of digital signals has the advantage that if it is required to make a listening array electronically steerable by using delay techniques this can be done more easily with digital signals than with analog signals by means of electronic switches.
If there are N receivers in an array and each receives incoherent noise signals only so that the probability that the signal received by a given receiver is positive is 1/~2 and the probability that it is negative is 1/2 then the probability that a given instant all of the receivers receive a positive signal is
The principle of a listening array is that an array of receivers is provided which is arranged so that any signal coming from the required predetermined direction will be received by all the receivers in phase, whereas any signal coming from a substantially different direction will be received with a phase difference between different receivers. This may be achieved merely by suitably placing the receivers or by incorporating delaying means into the receivers. The receivers are connected to a signal discriminator which is constructed to detect a component of the total signal received by each of the receivers which is in phase at all of the receivers and to reject components which are not in phase at all of the receivers.
In some applications it is required to recover the signal in order to extract information from it and in other applications it is only necessary to detect whether there is a signal coming from the given direction. This invention is concerned with listening arrays suitable for use in the latter type of application.
An object of the present invention is to provide a listening array with improved directionality and/or noise rejection over listening arrays of conventional type. A further object is to provide a signal discriminator for use in a listening array using digital techniques.
According to the present invention there is provided a ok ~;22S~
signal discriminator suitable for use with a listening array comprising a unanimity circuit capable of receiving a plurality of input signals and constructed to derive a binary 1 output signal whenever the input signals are all simultaneously of the same sense and a binary O output signal whenever the input signals are not all simultaneously of the same sense, and computing means connected to receive as input the output signals of the unanimity circuit and constructed to derive an output signal indicating signal detection if the rate of occurrence of binary 1 signals is high enough to satisfy a predetermined statistical criterion and to derive an output signal indicating no signal detection if the said rate is not high enough to satisfy the said criterion.
The statistical criterion may be derived from sequential sampling technique according to statistical sampling theory.
The signal discriminator may be constructed to receive binary digital input signals in which case the unanimity circuit may be constructed to produce a binary 1 output signal when all the input signals are binary 1 signals and also when all the input signals are binary O signals and to produce a binary O output signal in all other cases. It may for instance comprise an AND
gate and a NOR gate each connected to receive as inputs the input signals, the outputs of the AND and NOR gates being connected as inputs to an OR gate so what if the input signals are denoted by Al, A .~. AN the Output signal is constructed according to Al, A I. AN
Alternatively the signal discriminator may be constructed to receive analog input signals in which case the unanimity circuit may be constructed to produce a binary 1 output 5~S~3 signal when all the input signals are positive and also when all the input signals are negative and to produce a binary 0 output signal in all other cases.
The use of digital signals has the advantage that if it is required to make a listening array electronically steerable by using delay techniques this can be done more easily with digital signals than with analog signals by means of electronic switches.
If there are N receivers in an array and each receives incoherent noise signals only so that the probability that the signal received by a given receiver is positive is 1/~2 and the probability that it is negative is 1/2 then the probability that a given instant all of the receivers receive a positive signal is
2-N and the probability that they will all receive a negative signal is also 2 N. The probability of unanimity, that is to say the probability that the receivers will all receive signals of the same sense, is therefore 2 (N 1). If in addition to the incoherent noise signals each of the receivers also ; receives a signal S which is the same for all receivers the probability that the signal received by a given receiver has the same sense as S is increased and the probability that it has the opposite sense is decreased. There are still statistical fluctuations due to the noise and these are still independent, so if the probability that a receiver receives a positive signal is P
the probability of unanimity is now Pus = pun + (l-P) . Pus has its minimum value for P = 1/2 so the effect of a coherent signal S is to increase Pus If N is made large Pus becomes small but on the other hand the proportional effect on Pus of a
the probability of unanimity is now Pus = pun + (l-P) . Pus has its minimum value for P = 1/2 so the effect of a coherent signal S is to increase Pus If N is made large Pus becomes small but on the other hand the proportional effect on Pus of a
- 3 -so given change of P becomes greater The principle of the present invention is to detect the signal S by using statistical techniques to detect a change in Pus In any given application there will be a specified level of sensitivity and freedom from error. For example it may be required that the discriminator should be able to detect a signal when the signal to noise ratio has a specified low value with a given level of confidence. In other words when there is a signal present and the signal to noise ratio has the specified value it is required that the discriminator should detect the signal and the probability that it should fail to do so should not be greater than a specified probability 3 . It will also be required that when there is no signal present the probability of a spurious indication of the presence of a signal should be less than a specified probability . It will now be shown how the discriminator can meet requirements such as these by a suitable choice of statistical technique. The number N of receivers is assumed to be given.
Using an assumed noise amplitude distribution and an assumed signal amplitude distribution it is possible to compute the probability Pi that the output of the unanimity circuit will be a binary 1 wren there is a signal present and the signal to noise ratio has the specified value. The probability PO that the output of the unanimity circuit is 1 when no signal is present -(N-l) is simply 2 . What is required is that if binary 1 output signals from the unanimity circuit are occurring with a probability not less than Pi then the presence of a signal should be indicated with a probability of error of not more than 25~
and that if they are occurring with a probability as low as PO
then the absence of a signal should be indicated with a probability of error of not more than . This can be achieved by sampling the output of the unanimity circuit at successive instants and making signal or no-signal indications according to which of the following inequalities is satisfied first No log (Plop) - No log [(l-po)/(l-pl~ > log E ]
No log (Plop) - No log [(l-Po)/(l Pluck g E ]
where No is the number of samples which have been binary 1 signals and No is the number of samples which have been binary O
signals.
Successive samples are taken until one or other of these inequalities is satisfied. If inequality (1) is satisfied first an indication ox signal detection it made and if inequality (2) is satisfied first an indication of no signal detection is made. A
new series of samples can then be started. The time between successive instants when samples are taken must be long enough so that the noise signals at successive instants are substantially uncorrelated.
This form of sequential sampling technique is used in quality control applications. Its main advantage is that the number of samples which need to be taken in order to reach a decision varies, so that if there is a strong signal present and the signal to noise ratio is much greater than the specified value inequality (1) will be satisfied after comparatively few samples have been taken, whereas if the signal to noise ratio is just equal to the specified value more samples are necessary in order to achieve the desired degree of certainty.
~2~5~
An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings of which Figure 1 is a circuit diagram showing a unanimity circuit and Figure 2 is a logical flow diagram for computing means suitable for use in the invention.
Figure 1 shows a unanimity circuit constructed to receive analog input signals at the points marked Al, A ' AN. The analog input signals are applied as inputs to comparators lay lb ... lo each of which is constructed to produce a signal corresponding to a logical "O" when the corresponding analog input signal it positive and to produce a signal corresponding to a logical "1" when the corresponding input signal is negative. The outputs of the comparators 1 are applied as inputs to an AND gate 2 which produces an output corresponding to a logical "1" if all of its inputs correspond to a logical "1" and an output corresponding to a logical "O" in all other cases. The outputs of the comparators 1 are also applied as inputs to a NOR
gate 3 which produces an output corresponding to a logical "1" if all of its inputs correspond to a logical "O" and an output corresponding to a logical "O" in all other cases. Hence if all the analog input signals A are positive the output of the NOR
gate 3 will correspond to a logical "1" and if all the analog input signals A are negative the output of the AND gate 2 will correspond to a logical "1", but if the analog inputs A are not all of the same sense the outputs of the AND gate 2 and the NOR
gate 3 will both correspond to a logical "O". The outputs of the ,, 5g AND gate 2 and the NOR gate 3 are applied as inputs Jo an OR gate
Using an assumed noise amplitude distribution and an assumed signal amplitude distribution it is possible to compute the probability Pi that the output of the unanimity circuit will be a binary 1 wren there is a signal present and the signal to noise ratio has the specified value. The probability PO that the output of the unanimity circuit is 1 when no signal is present -(N-l) is simply 2 . What is required is that if binary 1 output signals from the unanimity circuit are occurring with a probability not less than Pi then the presence of a signal should be indicated with a probability of error of not more than 25~
and that if they are occurring with a probability as low as PO
then the absence of a signal should be indicated with a probability of error of not more than . This can be achieved by sampling the output of the unanimity circuit at successive instants and making signal or no-signal indications according to which of the following inequalities is satisfied first No log (Plop) - No log [(l-po)/(l-pl~ > log E ]
No log (Plop) - No log [(l-Po)/(l Pluck g E ]
where No is the number of samples which have been binary 1 signals and No is the number of samples which have been binary O
signals.
Successive samples are taken until one or other of these inequalities is satisfied. If inequality (1) is satisfied first an indication ox signal detection it made and if inequality (2) is satisfied first an indication of no signal detection is made. A
new series of samples can then be started. The time between successive instants when samples are taken must be long enough so that the noise signals at successive instants are substantially uncorrelated.
This form of sequential sampling technique is used in quality control applications. Its main advantage is that the number of samples which need to be taken in order to reach a decision varies, so that if there is a strong signal present and the signal to noise ratio is much greater than the specified value inequality (1) will be satisfied after comparatively few samples have been taken, whereas if the signal to noise ratio is just equal to the specified value more samples are necessary in order to achieve the desired degree of certainty.
~2~5~
An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings of which Figure 1 is a circuit diagram showing a unanimity circuit and Figure 2 is a logical flow diagram for computing means suitable for use in the invention.
Figure 1 shows a unanimity circuit constructed to receive analog input signals at the points marked Al, A ' AN. The analog input signals are applied as inputs to comparators lay lb ... lo each of which is constructed to produce a signal corresponding to a logical "O" when the corresponding analog input signal it positive and to produce a signal corresponding to a logical "1" when the corresponding input signal is negative. The outputs of the comparators 1 are applied as inputs to an AND gate 2 which produces an output corresponding to a logical "1" if all of its inputs correspond to a logical "1" and an output corresponding to a logical "O" in all other cases. The outputs of the comparators 1 are also applied as inputs to a NOR
gate 3 which produces an output corresponding to a logical "1" if all of its inputs correspond to a logical "O" and an output corresponding to a logical "O" in all other cases. Hence if all the analog input signals A are positive the output of the NOR
gate 3 will correspond to a logical "1" and if all the analog input signals A are negative the output of the AND gate 2 will correspond to a logical "1", but if the analog inputs A are not all of the same sense the outputs of the AND gate 2 and the NOR
gate 3 will both correspond to a logical "O". The outputs of the ,, 5g AND gate 2 and the NOR gate 3 are applied as inputs Jo an OR gate
4. The output of the OR gate 4 corresponds to a logical "1"
whenever all of the analog input signals A are of the same sense and to a logical "O" if they are not.
Figure 2 is a logical flow diagram of a programmer for a computing means for analyzing the output of the unanimity circuit by sequential sampling. The programmer is based on a rewriting of the inequalities (1) and I to enable integer arithmetic to be used. If we divide both sides of the inequalities (1) and (2) by d = log lo / (l-Pl)~ which, being approximately equal to (Plop) log e where e is the basis of natural logarithms, is small and positive, we obtain J No No Lo and J No - No -Lo where J = log (Plop / d Lo = log [(1 and ; 20 Lo = log I Ed The constants J Lo and Lo are positive and large compared with unity, so there will be only a small error introduced in rounding them to the nearest integer. We therefore define positive integer constants NJ~J, Null and MAX Ll+L2. The inequality corresponding to (1) can then be written, using the variable N =
NO No - NJ No, as N O .. (3) and that corresponding to (2) _ _ _ can be written N MAX ... (4). In the programmer illustrated in Figure 2 N is the only variable.
us - At the start of the programmer N is set equal to NO. The output of the unanimity circuit is then examined and if the output is 1 N is decreased by NJ. If N is negative inequality (3) is satisfied so thy response 'IDES'' indicating signal detection is given and a new series of samples is started. If N is not negative the output of the unanimity circuit is examined again.
If the output of the unanimity circuit is O when it is examined N
is increased by unity If N is equal to MAX inequality (4) is satisfied so the response "NO" indicating no signal detection is given and a new series of samples is started. If N its not equal to MAX the output of the unanimity circuit is examined again.
There is no provision for automatically stopping the programmer illustrated in Figure 2. Such a provision may simply be written into the programmer or alternatively the programmer may be interrupted manually when it is required to stop it.
If the number of receivers is large so that Plop is large and Pi and PO are small, and if the statistical confidence requirements are not too strict, so that and are not too small, it may happen that NJ is greater than or equal to MAX. In that case the programmer may be simplified since whenever the output of the unanimity circuit is found to be 1 the inequality (3) will always be satisfied. The programmer may then be set to examine the output of the unanimity circuit MAX times and to give the response "NO" if no samples equal to 1 are found, but to abandon the current series of samples and to give the response "YES" immediately if and when the output of the unanimity circuit is found to be 1. A number of variations on the embodiment described in this specification will be apparent to a Lo person skilled in the relevant art, for example one discriminator may be made to work for several listening arrays by using a multiplexing technique. Alternatively one computing means may be used in conjunction with several unanimity circuits. The discriminator may be incorporated into a listening array or alternatively the listening array and the discriminator may be physically separate and connected by, for example, a radio link.
It is also possible to incorporate the unanimity circuit in the listening array and to have a separate computing means.
whenever all of the analog input signals A are of the same sense and to a logical "O" if they are not.
Figure 2 is a logical flow diagram of a programmer for a computing means for analyzing the output of the unanimity circuit by sequential sampling. The programmer is based on a rewriting of the inequalities (1) and I to enable integer arithmetic to be used. If we divide both sides of the inequalities (1) and (2) by d = log lo / (l-Pl)~ which, being approximately equal to (Plop) log e where e is the basis of natural logarithms, is small and positive, we obtain J No No Lo and J No - No -Lo where J = log (Plop / d Lo = log [(1 and ; 20 Lo = log I Ed The constants J Lo and Lo are positive and large compared with unity, so there will be only a small error introduced in rounding them to the nearest integer. We therefore define positive integer constants NJ~J, Null and MAX Ll+L2. The inequality corresponding to (1) can then be written, using the variable N =
NO No - NJ No, as N O .. (3) and that corresponding to (2) _ _ _ can be written N MAX ... (4). In the programmer illustrated in Figure 2 N is the only variable.
us - At the start of the programmer N is set equal to NO. The output of the unanimity circuit is then examined and if the output is 1 N is decreased by NJ. If N is negative inequality (3) is satisfied so thy response 'IDES'' indicating signal detection is given and a new series of samples is started. If N is not negative the output of the unanimity circuit is examined again.
If the output of the unanimity circuit is O when it is examined N
is increased by unity If N is equal to MAX inequality (4) is satisfied so the response "NO" indicating no signal detection is given and a new series of samples is started. If N its not equal to MAX the output of the unanimity circuit is examined again.
There is no provision for automatically stopping the programmer illustrated in Figure 2. Such a provision may simply be written into the programmer or alternatively the programmer may be interrupted manually when it is required to stop it.
If the number of receivers is large so that Plop is large and Pi and PO are small, and if the statistical confidence requirements are not too strict, so that and are not too small, it may happen that NJ is greater than or equal to MAX. In that case the programmer may be simplified since whenever the output of the unanimity circuit is found to be 1 the inequality (3) will always be satisfied. The programmer may then be set to examine the output of the unanimity circuit MAX times and to give the response "NO" if no samples equal to 1 are found, but to abandon the current series of samples and to give the response "YES" immediately if and when the output of the unanimity circuit is found to be 1. A number of variations on the embodiment described in this specification will be apparent to a Lo person skilled in the relevant art, for example one discriminator may be made to work for several listening arrays by using a multiplexing technique. Alternatively one computing means may be used in conjunction with several unanimity circuits. The discriminator may be incorporated into a listening array or alternatively the listening array and the discriminator may be physically separate and connected by, for example, a radio link.
It is also possible to incorporate the unanimity circuit in the listening array and to have a separate computing means.
Claims (4)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A signal discriminator suitable for use with a listening array, comprising a unanimity circuit capable of receiving a plurality of input signals and constructed to derive a binary 1 output signal whenever the input signals are all simultaneously of the same sense and a binary 0 output signal whenever the input signals are not all simultaneously of the same sense, and computing means connected to receive as input the output signals of the unanimity circuit and constructed to derive an output signal indicating signal detection if the rate of occurrence of binary 1 signals is high enough to satisfy a predetermined statistical criterion and to derive an output signal indicating no signal detection if the said rate is not high enough to satisfy the said criterion.
2. A signal discriminator as claimed in claim 1 wherein the computing means is constructed to apply sequential sampling technique to the output signal of the unanimity circuity.
3. A signal discriminator as claimed in claim 2 wherein the computing means is constructed to sample the output signal of the unanimity circuit at successive instants and to derive an output signal indicating signal detection or no detection according to which of the inequalities N1 log (P1/P0) - N0 log [(1-P0)/(1-P1)] ? log [(1-.beta./.alpha.]
or N1 log (P1/P0) - N0 log [(1-P0)/(1-P1)] ? log [(1-.alpha.)/.beta.]
wherein .alpha., .beta., P0, P1, N0 and N1 have the meanings hereinbefore explained, is satisfied first.
or N1 log (P1/P0) - N0 log [(1-P0)/(1-P1)] ? log [(1-.alpha.)/.beta.]
wherein .alpha., .beta., P0, P1, N0 and N1 have the meanings hereinbefore explained, is satisfied first.
4. A signal discriminator as claimed in claim 3 wherein the computing means is constructed to perform the steps of:
a. at the start of a series of samples, setting a variable integer N equal to a predetermined constant NL, b. sampling the output signal of the unanimity circuit, continuing with step (e) if the signal is a binary 1 but with step (c) if the signal is a binary 0, c. increasing the value of the variable integer N by unity, continuing with step (d) if the value of the resulting integer N
is equal to a predetermined integer NMAX but otherwise returning to step (b), d. deriving an output signal indicating no signal detection and returning to step (a), e. reducing the value of the variable integer N by a predetermined integer NJ, continuing with step (f) if the value of the resulting integer N is negative but otherwise returning to step (b), f. deriving an output signal indicating signal detection and returning to step (a).
a. at the start of a series of samples, setting a variable integer N equal to a predetermined constant NL, b. sampling the output signal of the unanimity circuit, continuing with step (e) if the signal is a binary 1 but with step (c) if the signal is a binary 0, c. increasing the value of the variable integer N by unity, continuing with step (d) if the value of the resulting integer N
is equal to a predetermined integer NMAX but otherwise returning to step (b), d. deriving an output signal indicating no signal detection and returning to step (a), e. reducing the value of the variable integer N by a predetermined integer NJ, continuing with step (f) if the value of the resulting integer N is negative but otherwise returning to step (b), f. deriving an output signal indicating signal detection and returning to step (a).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1578674A GB1501111A (en) | 1974-04-09 | 1974-04-09 | Signal discriminator |
| GB15786/74 | 1974-04-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1225159A true CA1225159A (en) | 1987-08-04 |
Family
ID=10065445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000224005A Expired CA1225159A (en) | 1974-04-09 | 1975-04-08 | Signal discriminator |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1225159A (en) |
| GB (1) | GB1501111A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9203587D0 (en) * | 1992-02-20 | 1992-04-08 | Motorola Inc | Bus format detector |
| CN112255618B (en) * | 2020-09-29 | 2024-01-05 | 中国兵器工业集团第二一四研究所苏州研发中心 | Pixel-level moment identification circuit |
-
1974
- 1974-04-09 GB GB1578674A patent/GB1501111A/en not_active Expired
-
1975
- 1975-04-08 CA CA000224005A patent/CA1225159A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1501111A (en) | 1978-02-15 |
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