Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
  • G06F17/10—Complex mathematical operations
  • G06F17/18—Complex mathematical operations for evaluating statistical data, e.g. average values, frequency distributions, probability functions, regression analysis

Definitions

• the present invention relates to real-time devices, and more specifically to real-time devices for calculating an average of values represented by a signal.
• Mobile radio (electronic) devices often are required to adapt to changes in their environment or to vary the output which they are to produce in a nearly instantaneous manner. This has led to an increased reliance upon real-time
• Real-time here refers to the fact that the evaluation is performed at essentially the same time as the data is acquired. Real-time systems typically require very rapid processing of data as that data is obtained. Non-real-time evaluation occurs at some time long after the data is obtained. For example, when a mobile unit is requesting a service, a response from
• the system to the mobile unit takes a long time; the time lag in processing the data can cause the results to be obsolete by the time those results are obtained.
• the mobile telephones are often themselves in motion. This motion leads to changes in the strength of the signals received by the mobile unit.
• Cellular telephone networks attempt to maintain an acceptable signal level at each site, and switch the signal to a new cell when the average signal received from the mobile unit becomes weak, i.e. below the acceptable level. This switching may be accomplished by comparing the intensity of the average value of the signals from different cells and selecting that signal which is strongest.
• Determination of the average value is presently accomplished in the following manner.
• the receiver measures the signal intensity at a number of points, for example twenty, and stores these values in a memory.
• the values are then added and the sum is divided by the number of stored values. This yields the mean (average) value of the signal intensity.
• the next average is obtained by discarding the oldest stored value, replacing it with a new value, and performing the averaging computations just described. This leads to a smoother transition of the computed average over time, and utilizes a fixed memory capacity.
• This method is not ideal for real-time operations such as are used in cellular telephone systems. It requires memory devices for storing these values to be averaged. This complicates the hardware of the system and slows the averaging process. More importantly, it yields the average value as of the moment that is halfway between the newest and the oldest data value. In the example given above, the average value represents the value at the time midway between the 10th and 11th data value. Thus if instantaneous data were being sampled once every second, the average obtained is actually the average value as of a point in time ten seconds prior to the most recent data value measured. This does not include the delay caused by actually performing the calculations themselves.
• the present invention comprises a real-time signal averaging circuit.
• the averaging circuit includes clock means for generating timing signals.
• the averaging circuit also includes signal input means for receiving an input signal.
• the input signal represents a value x,, which is to be averaged by the averaging circuit.
• the averaging circuit further includes register means for temporarily storing and updating a previous average value s ⁇ which was output from the averaging circuit
• Averaging means are connected to the clock means, the signal input means and the register means.
• the averaging means provides in response to the timing signals a weighted average value a,, of the value x n represented by the input signal and of the previous average value a p stored in the register means.
• the average value a tons is defined as the sum ((M-l)a p + x divided by M, where M is a predetermined positive number greater than 1.
• the averaging means provides to the register means the average value z__.
• the circuit includes output signalling means for generating an output signal representing the average value a,,.
• the output signalling means is connected to said averaging means.
• the register means is a digital data register, and in which the value is represented by an analog amplitude, wherein the register means is a sample and hold device.
• the previous value a p is the immediately previous average value a ll . 1 .
• the present invention also includes a method of producing an average value of a signal in real-time.
• the method includes obtaining timing signals from a clock means. Next a previous average value a Brl is input into a register means. An input signal representing a value x,, to be averaged is then received. Then a weighted average value a,, of the previous average value a,,., and the value x n represented by said input signal is provided in response to the timing signals.
• the weighted average value a, is defined as the sum ((M-l)a,.. ⁇ + x n )) divided by M, where M is a predetermined positive number greater than 1. Finally an output signal is generated representing the weighted average value a,..
• the value may be represented digitally, in which case the register means is again a digital register, or an analog magnitude device.
• Figure 1 illustrates a signal being sampled at discrete points separated by uniform time intervals.
• Figure 2 is a flow chart illustrating the preferred implementation of the method of the present invention.
• Figure 3 is a block diagram representation of an implementation of an averaging circuit according to the present invention.
• Figure 4 is a schematic diagram of a circuit according to the present invention for averaging digital signals.
• Figure 5 is a schematic diagram of a circuit according to the present invention for averaging analog signals.
• Figure 6 is a block diagram representation of a comparison circuit according to the present invention.
• Figure 7 is a schematic diagram of a circuit according to the present invention for comparing the averaging values of a plurality of digital signals.
• Figure 8 is a schematic diagram of a circuit according to the present invention for comparing the averaging values of a plurality of analog signals.
• a signal to be averaged is sampled at regular intervals.
• the times at which these samples were obtained are referred to as to, t t , ... t tone, where there are n+1 data points sampled.
• the values of these data points are denoted as Q , X U ... Xm. While these signal values are said to represent the values to be averaged, this does not mean that there must be an encoding of external data into signal form.
• the signal may be inherently characterized by the values to be averaged.
• FIG. 1 illustrates an example of how such a sampling is undertaken.
• a signal 1 is shown plotted on a graph, where vertical distance represents the value of the signal and the horizontal distance represents time.
• the labelled circles represent the signal values X Q , x l5 ... sampled at the times to, trez .... A specified number of these values are added and the sum is divided by that number of values.
• the mean is equal to (x,, + Xj + ... + x 14 ) / 15.
• these n+1 values are stored in a memory device.
• the next subsequent mean would be obtained by discarding x ⁇ and replacing it with x ⁇ ,.
• the summation would then be performed by summing the values Xj to x, ⁇ ,.
• This allows for summation using a continuing adding process using an adder and with a memory for storing the n+1 most recent values.
• Such a procedure, utilized for each time sampled acts to smooth out the values of the means thus obtained. This helps eliminate noise and minimizes the possibility of dramatic swings in the average values obtained by the procedure.
• memory is used herein to describe devices for storage of values which are to be statically maintained during the calculation of several average value. In the specific example given above each memory location retains its value for 15 average value calculations. This is where the data itself is stored.
• register is used herein to describe devices for storage of values which are to be maintained only until used a single time, and then are replaced with a new value. Registers would be used to temporarily store data until it is utilized and replaced during the next average value calculation.
• FIG. 1 A first set 4 of 15 data points which are averaged at time t 14 is shown. Also, a second set 5 of 15 data points which are averaged at time t 15 . Since the processor only looks at n+1 points out of many that have been taken, it is said that the processor is looking at a "window" of values- This refers to the fact that this appears to be a slice on a graph of time plotted against sampled values. The n+1 points move on the graph in the direction of increasing time. Hence set 4 is to the left of the later set 5. This is known as “sliding" the "window".
• the mean does not provide an accurate representation of the average at the time t ban- Instead, it actually represents the average value at the time t- ⁇ ,, which is the time halfway between t o and t,.. Using the example in Figure 1, the mean is actually effective as of time t,, not t 14 .
• the present invention reveals a different method of generating an average, one which minimizes the need for memory and which provides an average which can be effective at a time far later than that of the prior art.
• the present invention provides a running average of the signal value.
• Each subsequent average is a weighted average of the new data point and the previous data points.
• the new average value a is generated by the following formula:
• the weight of the previous values of the signal depends solely upon the choice of M and the time interval between the time when the average is performed ( and the time when that value was sampled, (t ⁇ ). As M gets smaller, more recent points are weighted more heavily. As the weights accorded to recent values are increased, the effective time of the average becomes closer to the time t,,-
• the method of the present invention does not require a memory device, since in the preferred embodiment only a register is required to hold the previous value of the average, a n . 1 . This can lead to a significant decrease in the complexity of the hardware necessary to obtain the average over the prior art.
• a ⁇ replaces a,,- ! .
• the average value may be calculated based upon some time interval which is an integer i times the sampling time. This may be desired in cases where the sampling occurs faster than the circuit can produce the average. In such cases the undesired samples may be neglected while every i m sample is averaged.
• the previous average value may then be denoted as a p , to prevent confusing the indices of the average and the samples x ⁇ .
• the method of the present invention provides an effective average which is effectively closer in time to the time when the averaging is performed than the methods of the prior art.
• a significant decrease in hardware complexity can be achieved.
• the method may be implemented as follows.
• the most recent value of the average, ---- botanical, is retrieved at 14.
• the average value may be temporarily stored in a register separate from the arithmetic unit, or may be stored in the arithmetic unit itself.
• the value (M-I is computed by the arithmetic unit at 16.
• the counter n is then incremented at 18.
• the next value of the input signal, xicide, is read at 20.
• the value xicide is then summed at 22 with the output of step 16. It should be noted that the value of n has been incremented, and therefore the result obtained at 16 is actually (M-l)aont. ⁇ . Hence the result of step 22 is (M-l)..-,.. ! + -
• Figure 3 is a block diagram of an implementation of an averaging circuit according to the present invention.
• a clock 110 is provided for generating timing signals which control the timing of the operations accomplished by the circuit. These signals may be such that different signals operate to control different elements of the circuit, or all elements may be controlled by the same signal. The signal only need be utilized to control some element of the circuit.
• a signal input port 112 receives on input line 130 an input signal which is to be averaged.
• the input signal represents a value x,-. which is to be averaged by said averaging circuit, where the subscript n indicates a measure of the time at which the signal is received.
• the representation may be accomplished in a variety of manners know to the art, including but not limited to digital representation and amplitude modulation. The choice of representation schemes is then matched to the hardware which implements the averaging. This will be discussed in greater detail below.
• input port 112 responds to timing signals on input port clock control line 150 to transmit the signal value at discrete time intervals corresponding to integer values of n as described above. These signals x terme are transmitted on input port transmission line 132 to the averaging circuit 120.
• Averaging circuit 120 is connected to clock 110 and is responsive to timing signals transmitted on timing lines 152, 154 and 158, as discussed below.
• Averaging circuit 120 generates an average value a réelle from the value xicide and the previous average value a,,. ! - The previous average value a,. ⁇ is received from previous average retrieval line 138 which is connected to an output port setting line 136.
• Averaging circuit 120 acts to add x n to (M-l) times the previous average value a fertiliz. ⁇ -, and then divides the sum by M to yield the average value a,,.
• M may be set in the multiplier 122 and the divider 126 by a setting device 140. The role of the weighting factor M is discussed in greater detail above.
• averaging circuit 120 receives the previous average value a,,- ! from previous average input line 138 and stores it temporarily in multiplying circuit element 122.
• Multiplying circuit element 122 acts in response to timing signals on timing line 158 to generate a signal which represents the value (M-l)a,..j.
• the output signal from multiplying circuit element 122 is transmitted on multiplier output line 142 to adding circuit element 124.
• Adding circuit element 124 acts in response to timing signals on timing line 152 to generate a signal representing the sum of the value corresponding to the output of multiplying circuit element 122 ((M-l)a,..,) and that of the input signal value x n .
• the output of adding circuit element 124 is transmitted via adder output line 134 to dividing circuit element 126.
• Dividing circuit element 126 acts in response to timing signals on timing line 154 to generate a signal representing the value obtained by dividing the value represented by the output of adding circuit element 124 by M. The value thus obtained is the average value a-..
• the resulting signal representing the average acken is then transmitted on output port transmission line 136 to an output port 114.
• Output port 114 is connected to output line 148 to allow the average a,, to be accessed by external circuits.
• Initialization circuit 118 responds to timing signals from clock 110 on initialization timing line 160 to read the value x ⁇ M into memory 116 at time t ⁇ The value x ⁇ /M is then transmitted to previous average input line 138 and output port setting line 136.
• the input signal is a digital signal, wherein several individual binary voltage values together comprise a signal. This signal represents the value ⁇ .
• a clock 210 generates timing signals which control the timing of the operations accomplished by the circuit. As noted above, these signals may be such that different signals operate to control different elements of the circuit, or all elements may be controlled by the same signal. In addition, not every signal need be utilized to control some element of the circuit
• a signal input port 212 receives on input line 230 a digital input signal which is to be averaged.
• Signal input port may be implemented as a digital buffer.
• the input signal represents a value x sacrificed by the averaging circuit, as described above.
• Input port 212 responds to timing signals on input port clock control line 250 to transmit the signal value at discrete time intervals as described above. These signals x terme are transmitted on input port transmission line 232 to the averaging circuit 220. Averaging circuit 220 is connected to clock 210 and is responsive to timing signals transmitted on timing lines 252, 254 and 258, as discussed below.
• Averaging circuit 220 generates an average value a réelle from the value x,. and the previous average value a,,.,.
• the previous average value ⁇ is received from previous average retrieval line 238 which is connected to an output port setting line 236.
• the previous average value may be stored in a standard digital register, as described below.
• Averaging circuit 220 acts to add xicide to (M-l) times the previous average value a,,.,, and then divides the sum by M to yield the average value a,..
• the role of the weighting factor M is discussed in greater detail above.
• Averaging circuit 220 receives the previous average value from previous average retrieval line 238 and stores it temporarily in multiplying circuit element 222.
• Multiplying circuit element 222 acts in response to timing signals on timing line 258 to generate a signal which represents the value (M- ⁇ a,..,. If (M-l) is known to always be a power of two, then the multiplying circuit may be implemented as a single digital shift register, considerably simplifying hardware implementation. It may otherwise include a standard digital register and a digital multiplier. Such multipliers are well known in the art.
• the output signal from multiplying circuit element 222 is transmitted on multiplier output line 242 to adding circuit element 224.
• Adding circuit element 224 acts to generate a signal representing the sum of the value corresponding to the output of multiplying circuit element 222 ((M- ⁇ a-,.,) and that of the input signal value x.
• the output of adding circuit element 224 is transmitted via adder output line 234 to dividing circuit element 226.
• Dividing circuit element 226 acts in response to timing signals on timing line 254 to generate a signal representing the value obtained by dividing the value represented by the output of adding circuit element 224 by M. If M is known to always be a power of two, then dividing element 226 may be implemented as a single digital shift register. It may otherwise include a standard digital register and a digital divider. Such dividers are well known in the ait. The value thus obtained is the average value aont. The resulting signal representing the average a bland is then transmitted on output port transmission line 236 to an output port 214.
• Output port 214 may be implemented as a digital output buffer. Output port 214 is connected to output line 248 to allow the average a,, to be accessed by external circuits.
• Initialization circuit 218 responds to timing signals from clock 210 on initiahzation timing line 260 to read the value XQ M into memory
• the input signal is an analog signal, wherein the voltage value of the signal represents the value nie.
• a clock 310 generates timing signals which control the timing of the operations accomplished by the circuit. As noted above, these signals may be such that different signals operate to control different elements of the circuit, or all elements may be controlled by the same signal. Li addition, not every signal need be utilized to control some element of the circuit.
• a signal input port 312 receives on input line 330 an analog input signal which is to be averaged.
• Signal input port may be implemented as an analog sample-and-hold circuit.
• the instantaneous voltage value of the input signal represents a value X j ⁇ which is to be averaged by the averaging circuit, as described above.
• Input port 312 responds to timing signals on input port clock control line 350 to transmit the signal value at discrete time intervals as described above. These signals x, are transmitted on input port transmission line 332 to the averaging circuit 320.
• Averaging circuit 320 is connected to clock 310 and is responsive to timing signals transmitted on timing lines 352, 354 and 358, as discussed below.
• Averaging circuit 320 generates an average value a,, from the value xicide and the previous average value is received from memory output line 340 which is connected to a sample-and-hold (S/H) device 316.
• S H device 316 may be a standard sample-and-hold circuit.
• Averaging circuit 320 acts to add x n to (M-l) times the previous average value a ⁇ , and then divides the sum by M to yield the average value a chorus. The role of the weighting factor M is discussed in greater detail above.
• Averaging circuit 320 receives the previous average value a,.., from
• Multiplying circuit 322 acts to generate in response to timing signals on timing line 356 a signal which represents the value (M- l ⁇ j .
• Multiplying circuit 322 may be implemented as a standard op-amp with a gain of M-l, as shown.
• the gain of op-amp 370 is set by the ratio of resistors 372 and 374, i.e. (M-2)R 4 / R 4 , or (M-2).
• the gain of such an op-amp is the ratio of the resistances plus one. Hence the gain is (M-l).
• Op-amp 370 acts to multiply the amplitude of the signal.
• the output signal from multiplying circuit 322 is transmitted on multiplier output line 342 to adding circuit 324.
• Adding circuit 324 acts to generate a voltage representing the sum of the output voltage multiplying circuit 322 ((M-l)a,. . j ) and that of the input signal value x n on input port transmission line 332.
• the value on input port transmission line 332 is changed in response to timing signals on timing line 250 to S/H device 312.
• Adding circuit 324 may use resistors 376 and 378 to average the voltage between the inputs. The average is an arithmetic mean as the values of resistors 376 and 378 is the same, e.g. Rj.
• the op-amp 380 has a gain of two because the ratio of the resistances between resistors 382 and 384 is R 2 / R 2 or 1, and the gain of such an op-amp is the ratio of the resistances plus one.
• the output of op-amp 380 is a pure sum of the voltages, as twice the mean average of two values is the sum of those values.
• op-amp 380 acts as a driver for subsequent stages.
• Dividing circuit element 326 acts to divide the voltage representing the value obtained by dividing the value represented by the output of adding circuit 324 by M.
• Dividing element 326 may be implemented as a resistor-based voltage divider circuit as shown, where the output voltage is based upon the values of resistors 386 and 388 and is (M-1)R 3 / ((M-1)R 3 + R 3 ), or M.
• the value thus obtained is the average value a chorus.
• Output Port 314 may be implemented as an analog sample-and-hold circuit. Output port 314 is connected to output line 348 to allow the average to be accessed by external circuits.
• the average value a amid is transmitted on input line 338 to memory 316, which responds to a timing signal from clock 310 transmitted on transmission line 356 to store the new average value n__.
• Figure 6 is a flow chart for a method of comparing the average values of j distinct signals in real-time. Timing signals are obtained from a clock, which controls the sequence of steps. The j average values of the j signals at every instant are obtained by the method described above for calculating the averages by the present invention. The j previous average values a k p , where 0 ⁇ k ⁇ j - 1 and p is the index of the immediate previous average value, are read into j memory devices at 610. An input signal representing a value x kn to be averaged is received at j input ports at 612.
• a weighted average value __ of the previous average value a kp and the value x k n represented by the corresponding input signal is provided at 614 in response to the timing signals.
• the weighted average value is defined as the sum ((m-l)a kp + x k n ) divided by M, where M is a predetermined positive number greater than 1.
• j output signals representing each of j said weighted average value a ⁇ are transmitted at 616 to a comparison device.
• the j weighted average values a kn are compared at 618.
• this method may include initialization steps such as those discussed above regarding Figure 2. This initialization would occur at step 610, as initialization essentially provides a prior average value. Such initialization may be less critical in cases such as this implementation, where the error of multiple averaging should not disrupt the comparison being provided.
• This method may be implemented in a circuit, as illustrated in Figure
• a comparison circuit for real-time comparison of j distinct signal values said comparison circuit would require a clock circuit 710 for generating timing signals.
• This circuit may be constructed from multiple clocks, and may appear as j individual circuit clocks.
• the circuit would include j real-time signal averaging circuits 700, each of said signal averaging circuits being represented by an positive number label k, 0 ⁇ k ⁇ - 1. These circuits would be identical to the circuit disclosed above.
• the k ⁇ signal averaging circuit 702 includes a k to signal input port 712 for receiving the I--" 1 one of the j input signals. The input signal received at k* signal input port
• the k" 1 memory 716 stores a previous average value a kp which was output from k ⁇ signal averaging circuit 702.
• the k" 1 averaging subcircuit 720 is connected to clock 710, k 0 * signal input port 712 and k memory 716.
• the k ,h averaging subcircuit 720 provides in response to the timing signals an average value a ⁇ .
• This average is defined as the sum ((M-l)a kp + xj divided by M, where M is a predetermined positive number greater than 1.
• average value a, y . is the weighted average of the value x ⁇ represented by the k m input signal received at k m signal input port 712 and of the previous average value a tp stored in k* memory 716.
• the k" 1 averaging subcircuit 720 provides to k" 1 memory 716 the average value a tn .
• * output port 714 is connected to k m averaging subcircuit 720 to generate on k" 1 averaging circuit output line 718 a k 01 one of j output signals, thereby representing the average value a ⁇ .
• the j output signals are then compared by an appropriate comparison subcircuit 770 connected to each of the j signal averaging circuits 702 by one of the j averaging circuit output lines 718.
• these j averaging subcircuits may be designed to include initialization circuitry.
• This comparison circuit may be implemented in a variety of manners corresponding to the variety of methods of representing signal values, as discloses above.
• the input signals may be digital signals representing the values x ⁇ ,,.
• the digital k" 1 averaging circuits 702 may be constructed as illustrated in Figure 4 and discussed above.
• the j output signals of these averaging circuits 702 would be digital signals representing the weighted average values a ⁇ .
• Memory 716 could be implemented as a digital data registers.
• Comparison subcircuit 770 may be implemented as a simple digital calculation circuit.
• the input signals may be analog signals whose amplitudes represent the values x k n .
• the analog k" 1 averaging circuits 702 may be constructed as illustrated in Figure 5 and discussed above.
• the j output signals of these averaging circuits 702 would be analog signals representing the weighted average values a k n .
• Memory 716 could be implemented as a sample-and- hold-circuit, and comparison subcircuit 770 may be implemented as a simple analog comparator.

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• 1992
  • 1992-09-28 WO PCT/US1992/008242 patent/WO1993011482A1/en not_active Application Discontinuation
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