Determining delay in signal transmission along wired transmission medium

Abstract

To provide determination of a delay in signal transmission along a wired transmission medium.SOLUTION: An example system includes: a signal generator to output signals based on multiple carrier frequencies; a wired transmission medium for carrying the signals, where the wired transmission medium is configured to be open-ended to produce reflections on the wired transmission medium of the signals; and a signal analyzer to receive the reflections and to determine a transmission time of a signal along the wired transmission medium based on the reflections. The signal analyzer is configured to perform operations that include performing a search based on an estimated transmission time of the signal along the wired transmission medium and the reflections to determine the transmission time. The search is to determine which of multiple candidate transmission times to select for the transmission time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification describes an example implementation of a test system configured to determine a delay in signal transmission along a wired transmission medium. [Background technology]

[0002] A test system is configured to test the operation of a device. A device tested by a test system is called a device under test (DUT). A test system may include test equipment for transmitting test signals, such as radio frequency (RF) signals, and data over a wired transmission medium, such as a cable, to the DUT for testing. The DUT responds with a response signal. The test system expects the response signal to include certain values ​​and / or have certain timing. If the response signal has the proper values ​​and / or timing, the DUT passes the test. If the response signal does not have those values ​​and / or timing, the DUT may fail the test.

[0003] Wired transmission media, such as cables, introduce delays into a test system. For example, it takes time for the test signal and the response signal to propagate along the cable. This time, also known as the time of flight (TOF), is an example of a delay introduced by a cable during signal transmission. Delays can adversely affect testing. For example, when testing timing on a DUT, cable-related delays in signal transmission will affect the results.

[0004] Ultra-wideband (UWB) technology measures the time between two devices and converts it to distance. To get the most accurate distance, the delay of the cable between the test system and the DUT must be equal to the reported time / distance. Therefore, it can be important to know the actual delay of the cable. The same is true for over-the-air (OTA) measurements, where an antenna radiates a test signal to the DUT and the DUT responds. In some cases, the measured distance between the antenna and the DUT must be compensated for by an additional delay between the tester and the antenna. Summary of the Invention [Problem to be solved by the invention]

[0005] Thus, techniques have been implemented to determine the delay in signal transmission and factor this delay into the test process, for example, to calibrate the test system based on the delay. An exemplary technique for determining the delay in signal transmission includes incorporating a transmitting device and a measuring device at different ends of a cable. The measuring device measures the transmission time based on the time the transmitting device transmitted the signal. Such techniques can be labor intensive, requiring specialized equipment that must be set up and then removed, especially when there are multiple ports to connect to the DUT. Thus, for some types of DUTs, techniques such as these can be difficult to implement in some test contexts. [Means for solving the problem]

[0006] An exemplary system includes a signal generator that outputs a signal based on a plurality of carrier frequencies, a wired transmission medium for carrying the signal, the wired transmission medium configured as open ended to generate reflections on the wired transmission medium of the signal, and a signal analyzer that receives the reflections and determines a transmission time of the signal along the wired transmission medium based on the reflections. The signal analyzer is configured to perform operations including performing a search to determine the transmission time based on an estimated transmission time of the signal along the wired transmission medium and the reflections. The search is to determine which of a plurality of candidate transmission times to select for the transmission time. The plurality of candidate transmission times vary by a multiple of a step size. An exemplary system can include one or more of the following features, either alone or in combination.

[0007] The operations may include performing a coarse search based on the reflections to determine an estimated transmission time. The coarse search may be performed to determine which of a plurality of candidate transmission times to select for the estimated transmission time. The plurality of candidate transmission times used in the coarse search may vary by multiples of a first step size. The search based on the estimated transmission time may include a fine search. A step size in the fine search may be a second step size. The first step size may be greater than the second step size. The plurality of candidate transmission times used in the coarse search may include a first candidate transmission time, and the plurality of candidate transmission times used in the fine search may include a second candidate transmission time.

[0008] The coarse search may be insensitive to a magnitude and phase offset of a signal having a first candidate transmission time. The coarse search may include identifying a maximum correlation based on (i) the first candidate transmission time and (ii) a sum of reflections along the wired transmission medium, reflections at an open end of the wired transmission medium, and noise, where the maximum correlation may correspond to the estimated transmission time. The fine search may be sensitive to a magnitude and phase offset of a signal having a second candidate transmission time. At least two of the multiple carrier frequencies may be orthogonal.

[0009] The fine search may include determining a transmission time within a predetermined range of the estimated transmission time based on a difference between (i) a value based on the reflections and (ii) a value based on the second candidate transmission times. Determining the transmission time may include identifying one of the values ​​based on one of the second candidate transmission times that minimizes the difference. The predetermined range may be within a range of 200 picoseconds or greater.

[0010] The reflection-based value can be based on a magnitude and a phase of the reflection. The second candidate transmit time-based value can be based on a magnitude and a phase of a signal having a different transmit time. The different transmit times may vary by a single digit picosecond.

[0011] The signal generator and the signal analyzer may be part of a single hardware device connected to a wired transmission medium. The single hardware device may be or include a tester or test system. The tester or test system may include one or more processing devices programmed to perform the search. The multiple carrier frequencies may be upconverted based on a direct current (DC) signal. The multiple carrier frequencies may be non-upconverted carrier signals.

[0012] An exemplary method includes operations including outputting a signal on a wired transmission medium based on a plurality of carrier frequencies, the wired transmission medium being configured as open ended to generate reflections on the wired transmission medium of the signal, and determining a transmission time of the signal along the wired transmission medium based on the reflections. Determining the transmission time includes performing a search based on an estimated transmission time of the signal along the wired transmission medium and reflections to determine the transmission time. The search is performed to determine which of a plurality of candidate transmission times to select for the transmission time. The plurality of candidate transmission times vary by a multiple of a step size. An exemplary method can include one or more of the following features, either alone or in combination.

[0013] Determining the transmission time may include performing a coarse search based on the reflections to determine an estimated transmission time. The coarse search may be performed to determine which of a plurality of candidate transmission times to select for the estimated transmission time. The plurality of candidate transmission times used in the coarse search may vary by multiples of a first step size. The search based on the estimated transmission time may include a fine search. The step size in the fine search may be a second step size. The first step size may be greater than the second step size. The plurality of candidate transmission times used in the coarse search may include a first candidate transmission time, and the plurality of candidate transmission times used in the fine search may include a second candidate transmission time.

[0014] The coarse search may be insensitive to the magnitude and phase offset of the signal having the first candidate transmission time. The coarse search may include identifying a maximum correlation based on (i) the first candidate transmission time and (ii) a sum of reflections along the wired transmission medium, reflections at an open end of the wired transmission medium, and noise. The maximum correlation may correspond to the estimated transmission time.

[0015] The fine search may be sensitive to a magnitude and a phase offset of a signal having a second candidate transmission time. At least two of the multiple carrier frequencies may be orthogonal.

[0016] The fine search may include determining a transmission time within a predetermined range of the estimated transmission time based on a difference between (i) a value based on the reflections and (ii) a value based on the second candidate transmission times. Determining the transmission time may include identifying one of the values ​​based on one of the second candidate transmission times that minimizes the difference. The predetermined range may be within a range of 200 picoseconds or greater.

[0017] The reflection-based value may be based on a magnitude and a phase of the reflection. The second candidate transmit time-based value may be based on a magnitude and a phase of a signal having a different transmit time. The different transmit times may vary by a single digit picosecond. The multiple carrier frequencies may be upconverted based on a direct current (DC) signal. The multiple carrier frequencies may be non-upconverted carrier signals.

[0018] Any two or more of the features described herein, including in this Summary section, may be combined to form implementations not specifically described herein.

[0019] At least some of the devices, systems, techniques, and processes described herein may be configured or controlled by executing instructions stored in one or more non-transitory machine-readable storage media on one or more processing devices. Examples of non-transitory machine-readable storage media include read-only memory, optical disk drives, memory disk drives, and random access memories. At least some of the devices, systems, techniques, and processes described herein may be configured or controlled using a computing system that includes one or more processing devices and a memory that stores instructions executable by the one or more processing devices to perform various control operations. The devices, systems, techniques, and processes described herein may be configured, for example, by designing, building, composing, configuring, arranging, programming, operating, activating, deactivating, and / or controlling.

[0020] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0021] [Figure 1] 1 is a block diagram illustrating an example signal reflection along a wired transmission medium having an open end. [Diagram 2] 1 is a block diagram of components of an exemplary test system including an open-ended wired transmission medium; [Diagram 3] 4 is an operational block diagram of an exemplary process for determining a delay in signal transmission along a wired transmission medium having an open end. [Figure 4] 1 is an example graph illustrating an example of delay in signal transmission along a wired transmission medium determined using different processes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Like reference numbers in the different drawings indicate like elements.

[0023] Described herein are example implementations of processes for determining a delay in signal transmission associated with a wired transmission medium, such as a cable, and example systems configured to implement those processes. The example process includes connecting a signal transceiver to one end of the cable and leaving the other end of the cable open-ended, e.g., not connected to a device under test (DUT). The "cable" in this example can include any fixtures, such as connectors, that connect the cable to the signal transceiver and to the DUT.

[0024] The signal transceiver outputs signals to the cable across multiple carrier frequencies. Each signal output to the cable may be a carrier signal. The examples shown below describe a carrier signal having a selected carrier frequency that is upconverted using a DC signal, referred to herein as a DC upconverted signal. However, other types of carrier signals are used, including signals having different frequencies that are generated to have different amplitudes without undergoing DC upconversion. A DC signal is used because it does not introduce additional complications, such as additional phases. Upconversion, in some examples, involves modifying the amplitude of a carrier signal by multiplying it with a DC signal, i.e., essentially, amplitude modulation of the carrier signal using a DC signal. In some examples, at least two of the carrier signals have different frequencies that are orthogonal.

[0025] The DC upconverted signal transmitted over the cable may reflect back to the signal transceiver from the open end of the cable. The DC upconverted signal transmitted over the cable may also reflect from mismatches or anomalies along the path of the cable. The mismatches or anomalies may include, for example, impedance mismatches, structural anomalies within the cable, and / or connectors along the cable.

[0026] Examples of these reflections are shown in Figure 1. More specifically, in Figure 1, a signal transceiver 10 outputs a DC upconverted signal 11 onto a cable 12. The cable has mismatches 16, 17 and an open end 19. Reflections 20, 21, and 22 of the DC upconverted signal occur at the mismatches 16, 17, and the open end 19, respectively. Although three reflections are shown, in some examples there may be dozens or hundreds or more. The signal transceiver 10 receives these reflections and organizes them into a vector / array, with each element for a separate different carrier frequency.

[0027] The exemplary process is to estimate the transmission time t of a signal over cable 12. T(粗) The coarse search includes performing a coarse search based on the reflections to determine t t , which in this example is a coarse search that determines which of a number of candidate transmission times to select for the estimated transmission time based on correlation with elements in the vector / array. The candidate transmission times vary by multiples of a predetermined step size, which in the example of the coarse search may be tens or hundreds of picoseconds (ps) or less, or more. The candidate transmission time with the highest correlation with the elements of the vector / array is determined to be the estimated transmission time t t , of the signal over the length of cable 12 as determined by the coarse search. T(粗) and the transmission time t T is used in subsequent or fine search operations to further refine

[0028] The fine search is performed for the estimated transmission time t T(粗) For example, the range defined by the value "d" in this example can be selected based on the carrier frequency and the cable length. d can be, for example, but not limited to, greater than or less than 800 ps, ​​such as 200 ps, ​​300 ps, ​​400 ps, ​​etc., as the case may be. The fine search is performed over a period of time t T For t T(粗) -d to t T(粗)+d. An optimization is performed to determine which of multiple candidate transmit times within the range of d to select. The candidate transmit times in the fine search are different from those used in the coarse search and vary by a multiple of a predetermined step size. In the fine search phase, the predetermined step size may be single digit picoseconds, such as 10 ps or less, or tens of picoseconds or less, such as 100 ps or less, or in some examples less or more.

[0029] The optimization performed in the fine search is sensitive to signal phase and offsets in signal phase, which is not necessarily the case for the correlation performed in the coarse search. In this example, the offset indicates that the phases of the reflections are not the same, which may be due to, for example, different reflection points along the cable. As a result, the fine search may allow for a more accurate determination of the transmission time than the coarse search. In some implementations, the fine search may be performed independently of the coarse search by using ranges determined based on the test settings and attributes of the cable, such as, but not limited to, cable length, cable composition, and cable geometry.

[0030] FIG. 2 is a block diagram illustrating an arrangement of components of an example test system 25 configured to implement the example processes described herein.

[0031] Test system 25 includes one or more test instruments 43. The test instruments may be hardware devices that may include one or more processing devices and / or other processing circuitry (not shown). The test instruments may be configured (e.g., programmed) to output test signals via signal transceiver 26 to a test DUT (not shown) connected to a wired transmission medium, such as cable 32. The test signals for testing the DUT may be or include instructions, commands, data, parameters, variables, test patterns, and / or any other information designed to elicit a response from the DUT. One or more, e.g., all, of the test instruments may be configured to receive responses from the DUT (via signal transceiver 26) to the test signals transmitted from the test instruments to the DUT. The test instruments may be configured to analyze the responses to determine whether the DUT passes or fails a test. For example, the timing of the responses may be analyzed, the data that the responses represent may be analyzed, etc. The test equipment may include, but is not limited to, radio frequency (RF) equipment for testing RF signals, digital test equipment for testing digital signals, analog test equipment which may include pin electronics and / or parametric measurement units (PMUs), and the like.

[0032] The test system 25 includes a control system 45. The control system may be or may include a computing system comprised of one or more processing devices 46 (e.g., microprocessors) and memory 47 for storage. In one example, the control system 45 may be configured to execute instructions (e.g., computer code) 49 stored in the memory 47 to control the test equipment 43 to perform tests on the DUT, for example, to send the test equipment test programs to execute to generate test signals, or to send test signals to the test equipment for processing and / or forwarding to the DUT. The control system 45 may also be configured to execute instructions to control the signal transceiver 26, described below, and / or to perform all or part of the coarse search process and fine search process described with respect to FIG. 3. The dashed lines 44 indicate wired or wireless connections between the components shown in FIG. 2 through which analog, digital, and / or RF communications between the components may pass.

[0033] The signal transceiver 26 includes a signal generator 28 and a signal analyzer 29, or the functionality of each of these components in one, two, or more hardware devices. In some implementations, the signal generator 28 is configured to operate as a carrier signal generator, and in this capacity is configured to generate and output a delay test signal that is used to test delays along a wired transmission medium, such as a cable 32. The formation and timing of the delay test signal may be defined (e.g., directed, set, and / or controlled) by a control system 45 and / or one or more test instruments 43. In this example, the delay test signal is a DC up-converted signal. Although a DC up-converted signal is used in the following examples, an alternating current (AC) signal, a complex signal, or other types of signals may be used as the delay test signal.

[0034] The signal generator 28 is configured to generate multiple carrier frequencies to generate the DC upconverted signal based on one or more DC signals. The DC signal used to generate the DC upconverted signal may be provided to or generated by the signal generator 28. The number of carrier frequencies and the actual frequency used may be defined by the control system 45 and / or by one or more test instruments 43. The carrier frequencies may be in a range such as, but not limited to, 4 gigahertz (GHz) to 12 GHz, or in some examples greater than 12 GHz. In some examples, there may be dozens or hundreds of carrier frequencies that are upconverted by (e.g., based on) the DC signal, and these carrier frequencies may vary, for example, by being incremented at regular intervals. In a non-limiting example, the carrier frequency may start at 4 GHz and be incremented by 0.1 GHz to 6 GHz. In another non-limiting example, the carrier frequency may start at 5 GHz and be incremented by 0.01 GHz to 9 GHz. Any suitable increments and / or frequency ranges may be used, not just those listed here.

[0035] The test system 25 also includes a wired transmission medium 32, such as, but not limited to, a cable (e.g., a coaxial cable), a transmission line, and / or any other type of electrical conductor. The following example describes the use of a cable 32 as a wired transmission medium. The cable may include fixtures 34, 35, such as connectors, in this example, at respective ends 36, 37 of the cable. The processes described herein, in some implementations, account for the presence of these fixtures and the delays caused by these fixtures. Thus, in some implementations, references to a cable and / or wired transmission medium include any conductive medium over which signals are transmitted with fixtures at or along its length.

[0036] As mentioned above, in the test system 25, the cable 32 is open ended. For example, one end 35 / 37 of the cable 32 is not connected to a DUT or other device to receive signals from the cable. However, in some examples, an RF probe (not shown) may be connected to the end 35 of the cable 32. The RF probe may monitor signals on the cable. The cable may include multiple sections. For example, as shown in FIG. 2, the cable 32 may include individual cables, such as cables 32a, 32b, that are connected via a connector 40. The connector 40 may create impedance mismatches that cause reflections (see, e.g., FIG. 1). The cable 32 may also include one or more anomalies 41, caused by manufacturing defects or damage, that may result in impedance mismatches along the length of the cable and cause reflections (see, e.g., FIG. 1).

[0037] The signal generator 28 is configured to output DC upconverted signals, such as signal 11 of FIG. 1, onto the cable 32, which are generated based on a number of different carrier frequencies. Because a number of DC upconverted signals are output, there are consequently a number of reflections on the cable, e.g., one or more reflections for each DC upconverted signal. In the example of FIG. 2, the DC upconverted signals based on the various carrier frequencies reflect from the open ends 35 / 37 of the cable 32, from anomalies 41, and from impedance mismatches 40. These reflections are directed back along the cable towards the signal transceiver 26. The reflections are out of phase with each other and travel along different lengths of the cable, as described with respect to FIG. 1. This is due, at least in part, to the use of different frequencies, reflections that do not occur at the same location along the cable, and reflections that do not occur at regular or known intervals corresponding to the phase of the DC upconverted signals.

[0038] The signal analyzer 29 is configured to receive the reflection of the DC upconverted signal and measure the reflection. Referring to FIG. 1, the measured reflection is x(t i For example, the signal analyzer may includei In some implementations, the signal analyzer 29 measures the value of the reflected signal x at the transmission time t T 1 and 2, t T is the time of flight of the signal from the open end 19, 35 / 37 back to the signal transceiver 26, i.e., the time along the entire length of the cable.

[0039] In some implementations, the signal analyzer 29 uses process 50 of FIG. 3 to determine the transmission time t of the DC upconverted signal along the entire length of the cable based on the reflections. T In some implementations, the signal analyzer 29 can be configured to provide its measurements to a control system 45, which can use process 50 of FIG. 3 to determine the transmission time t of the DC upconverted signal along the length of the cable based on the reflections. T In some implementations, the signal analyzer 29 may be configured to provide its measurements to one or more of the test instruments 43, which determine the transmission time t of the DC signal along the length of the cable based on reflections using process 50 of FIG. T In some implementations, the signal analyzer 29, the test equipment, and / or the control system 45 may be configured to determine the transmission time t of the DC upconverted signal along the length of the cable based on the reflections using the process 50 of FIG. T The signals may be configured to operate together to determine

[0040] 3, process 50 includes configuring (50a) a test system to determine a delay (e.g., time of flight “TOF”) in signal transmission along cable 32. In this example, the configuration operation may include disconnecting the DUT or other device from fixture 35, leaving end 37 of cable 32 open-ended, and leaving cable 32 connected to test system 25 via fixture 34.

[0041] The signal generator 28 transmits (50b) a plurality of different DC upconverted signals (or other signals, such as carrier signals, AC signals, complex signals, etc., as delayed test signals) to the cable 32 having the open end 37. As described above, the signal generator 28 can be controlled by the control system 45 and / or the test equipment 43 to output the DC upconverted signals. For example, the selection of the DC signal value(s) and the carrier frequency used to generate the plurality of DC upconverted signals may be performed by the control system 45 and / or the test equipment 43 based on programming in their components and / or user input. For example, in some implementations, the plurality of DC upconverted signals can be based on (e.g., formed using) a single DC value and a plurality of different carrier frequencies. For example, in some implementations, the plurality of DC upconverted signals can be based on (e.g., formed using) a plurality of different DC values ​​and a plurality of different carrier frequencies.

[0042] The DC upconverted signal reflects from the cable open end 37 and from various points along the cable, for example, as described with respect to FIG. 1. The signal analyzer 29 receives the reflected signal from the cable 32 (50c), i.e., the signal analyzer receives a reflection of the DC upconverted signal. The signal analyzer 29 measures the reflected signal (i.e., the reflection) (50d). For example, the signal analyzer 29 measures the magnitude and phase of the reflection "x" over time "t i " where the subscript "i" corresponds to different transit times.

[0043] In some implementations, the signal analyzer 29 measures (50d) a signal y based on the composite reflections, which in this example is a signal y fn y = [y f1 ,y f2 ,….], where “fn” is the frequency. f1 etc.) is x(t i ), x(t T ), and the noise n. x(t i ) is a vector defined as follows: x(t i )=[(x(t i ),f1),(x(t i ),f2)….], where x(t i ) is the travel time t i and a measure of the reflection from a signal path having frequency f, where x(t i )∈C K x(t i ) is measured for each x(t i ) can include the amplitude, frequency, phase, and timing (e.g., time of reception). T ) is the reflection from the cable open end 37 (e.g., the reflection from the entire length of the cable 32) that is the value being sought in y. T ) is x(t i ) where n is the random noise in the corresponding reflection, where n∈C K In some instances, only the signal y can actually be measured by the signal analyzer 29, and its components, i.e., x(t i ), x(t T ), and the noise n are not individually measurable by the signal analyzer.

[0044] Process 50 performs a coarse search process based on y to find x(t T(粗) ) is determined (50e), and x(t T(粗) ) is an estimate of the delay of signal transmission along the entire length of cable 32 obtained using a coarse search process. The coarse search process calculates t T(粗)To determine what the best estimate of the value of t is, the coarse search process T The estimate x(t T ) value to i Different candidate values ​​of y are tested, for example, as explained above and as shown in equation (1) below: T ) that matches the t value that is closest to y. T is the estimated delay of signal transmission along the entire length of cable 32 (t T(粗) ), which can be further refined using the fine-grained search process described below.

[0045] More specifically, the signal analyzer detects the target travel time t T , and receives reflections (i.e., reflected versions of the DC upconverted signal / delayed test signal) that define a vector y, defined as:

number

[0046] Target movement time t T Magnitude response of a t ∥ 2By assuming that t is maximal, the coarse search process uses the correlation process of equation (2) to find the t for the maximum correlation of * Ask for,

number

[0047] More specifically, the correlation process in equation (2) is T ), i.e., x(t * ) by selecting those x(t T ) that has the highest correlation with the values ​​in vector y. T Different candidates of t * The different candidate times used in the correlation process can vary by multiples of the step size. For example, t T Candidates for t * is a function of x(t * )~x(t *+step_size ), x(t *+step_sizex2 ), x(t *+step_sizex3 ) to the end value x(t *+step_sizex(n)(where n>3) ) by a step size ("step_size") of, for example, tens or hundreds of picoseconds (ps) or more or less. * ), where the superscript "x" means "multiplied by." The start value, end value, and step size may be based on the DUT being tested, the frequency used for testing, the length of the cable, and / or other factors. The choice of step size may be a trade-off between the resolution obtained (limited by noise) and the time required for processing. The smaller the step, the longer the processing time. Steps that are too small may be limited by noise and other minor impairments and may be filtered out in some implementations.

[0048] Figure 4 shows the time t *5 shows an example graph illustrating an example correlation 56 obtained using equation (2) for different values ​​of x(t) 57 over a range of t 58. As shown, in this example, the maximum correlation occurs at a time of about t 460 ps. * The value 55 is the estimate (t T(粗) ) for the transmission time along the cable 32. More specifically, as described above, the fine search process 50 may use t T(粗) -d to t T(粗) An optimization is performed to determine which of multiple candidate transmit times within the range of +d to select. The candidate transmit times used in the fine search process may vary by, but are not limited to, a multiple of a step size of single or double digit picoseconds, or more, in some examples. In the fine search phase, an exemplary predetermined step size may be, but is not limited to, single digit picoseconds, such as 10 ps or less, in some examples.

[0049] The correlation in equation (2) is based on the phase offset (i.e., e jθ x(t T )), where θ is the time constant x(t T(粗) ) phase and magnitude a T As a result, the correlation of equation (2) may be subject to reflection travel path interference because different reflected signals (i.e., reflections) along the cable 32 are not correlated. This is because the maximum correlation at value 55 (FIG. 4) determined by equation (2) occurs at the target point: t * ≠t T This means that the interference pattern can be influenced by T(粗) That is, the maximum correlation due to the interference pattern is t T The fine search (50f) performed by process 50 is sensitive to phase offset and magnitude response in this example. This sensitivity is due to the fact that it is much faster than the coarse search process. T provides better resolution of t T(粗)This can reduce the effect of interference patterns caused by reflections on the estimate of .

[0050] The fine search process (50f), also referred to herein as the null space process, uses some of the same nomenclature and variables as the coarse search process, and therefore will not be described again here. t* Vector to ya * x(t * ) is minimized by the projection of vector a * x(t * ) to explore the vector space S t is the sum of all possible magnitude responses, e.g., {a m x(t * )} over a travel time t along the entire length of the cable 32, where "m" is an integer greater than 1. The following describes how the optimization used in performing the fine search is determined.

[0051] a for m=1,2,... m Listing all possible magnitude responses of reflection "x" as follows produces the following vector set: X t =[a1 x(t),a2 x(t),...]

[0052] The eigenvalue decomposition produces:

number

number

[0053] The first L (L>1) largest eigenvalues ​​corresponding to the eigenvectors are t The remaining eigenvalues ​​are then retained to construct the vector space St are so small that they have little effect on the S t =span{q1,q2,...q L}

[0054] Construction S t When enumerating all possible magnitude responses to , the magnitude offset used is S since any offset only contributes to the eigenvalues. t has little or no effect on the eigenvectors and the space S t remains the same. Thus, when enumerating all possible magnitude responses, only the "shape" of frequency versus magnitude is important.

[0055] The optimization shown in the following formula (3) is * is used to identify the optimization maximum by varying t * The value of t T It is determined that the delay is t * For different values ​​of a * x(t * ) is performed. Thus, in this fine search process, * ) that gives the maximum value of Eq. (3) is searched. * x(t * ) values ​​are y and a * x(t * ) corresponds to the value of t (the delay along the cable 32) that minimizes the difference between

number

[0056] t used in Eq. (3) * At different times (t T The candidates for t can vary by multiples of the step size. For example, * The different times are along the continuum between the two frequencies, for example in the range from 4 GHz to 12 GHz, * x(t* )~a * x(t *+step_size ), a * x(t *+step_sizex2 ), a * x(t *+step_sizex3 ) to the end value a * x(t *+step_sizex(n)(where n>3) ), for example, by a step size ("step_size") of tens of picoseconds (ps), single digit picoseconds or more. * x(t * ), where the superscript "x" means "multiplied by." In some examples, the start and end values ​​can correspond to a * x(t T(粗) -d) and a * x(t T(粗) +d), t T(粗) -d and t T(粗) +d is determined in time using a coarse search process 50. In some examples, the start and end values ​​may be pre-programmed into the test system and may not be based on a coarse search process (e.g., if the coarse search process is not performed). The step size may be based on the DUT being tested, the frequency used for testing, the length of the cable, and / or other factors.

[0057] The search performed using the optimization equation (3) is sensitive to the magnitude and phase offset of the reflections. To illustrate this, assume that the signal analyzer 29 receives a signal y that contains a target signal a·x. When performing the optimization of equation (3) using a random phase or magnitude offset, the target signal is subtracted ya * x(t * ) is not completely removed after the candidate a * x(t * ) in a * and x is a unique * and is not equal to the actual value of x. The remaining signal is in the subspace S t , which results in a lower value than that produced by equation (3).* When optimizing equation (3) using * x(t * ) is completely removed after the remaining signal S t The projection onto is minimized, which leads to the maximum of equation (3).

[0058] Figure 4 shows a * x(t * ) using equation (3) for different values ​​of t T(粗) -d and t T(粗) Included is an exemplary curve showing the optimization 56 obtained over t + d. As shown, in this example, the optimization maximum occurs at a value 60 of approximately 456.5 ps, which corresponds to t T , i.e., the delay along the entire length of the cable 32, and t T(粗) Similarly, due to reduced interference effects, the envelope 61 generated using the fine search process is smaller, e.g., shorter in duration, than the envelope 62 generated using the coarse search process.

[0059] Referring back to FIG. 3, the process 50 includes: T The control system can then provide a value of travel time t along the cable 32 during the DUT test to the control system 45. T The test system can be calibrated (50h) to take into account and / or eliminate the effects of

[0060] All or part of the testing systems and processes described herein and various modifications thereof may be configured or controlled at least in part by one or more computers, such as the control system 45 and / or the test equipment 43, using one or more computer programs tangibly embodied in one or more information carriers, such as one or more non-transitory machine-readable storage media. The computer programs may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a stand-alone program or as a module, portion, subroutine, or other unit suitable for use in a computing environment. The computer programs may be deployed to be executed on one computer, or on multiple computers at one site, or distributed across multiple sites and interconnected by a network.

[0061] Operations associated with configuring or controlling the test systems and processes described herein may be performed by one or more programmable processors executing one or more computer programs to control or perform all or a portion of the operations described herein. All or a portion of the test systems and processes may be configured or controlled by dedicated logic circuitry such as FPGAs (field programmable gate arrays) and / or ASICs (application specific integrated circuits) or embedded microprocessors localized in the instrument hardware.

[0062] Processors suitable for the execution of a computer program include, by way of example, both general purpose and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from a read-only or random access memory area, or both. Elements of a computer include one or more processors for executing instructions and one or more storage devices for storing instructions and data. Generally, a computer also includes or is operatively coupled to receive data from or transfer data to one or more machine-readable storage media, such as mass storage devices for storing data, such as magnetic, magneto-optical, or optical disks, or both. Non-transitory machine-readable storage media suitable for embodying computer program instructions and data include all forms of non-volatile storage including, by way of example, EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), and flash storage devices, magnetic disks such as internal hard disks or removable disks, magneto-optical disks, and semiconductor storage devices such as CD-ROM (compact disc read-only memory), DVD-ROM (digital versatile disc read-only memory), and the like.

[0063] In the description and claims provided herein, the adjectives "first," "second," "third," etc. do not designate a priority or order. Instead, these adjectives are used only to distinguish the nouns they modify.

[0064] Any mechanical or electrical connection herein may include a direct physical connection or an indirect connection involving intervening components.

[0065] Elements of different implementations described may be combined to form other implementations not specifically described above. Elements may be omitted from the systems described above without adversely affecting their operation or the operation of the system in general. Additionally, various separate elements may be combined into one or more individual elements to perform the functions described herein.

[0066] Other implementations not specifically described herein are within the scope of the following claims. [Explanation of symbols]

[0067] 11 signals 19 Open end 20 reflections 21 reflection 28 Signal generator 29 Signal Analyzer 32 Wired transmission media 35 Open end 37 Open end 56 Correlation

Claims

1. 1. A system comprising: a signal generator that outputs signals based on a plurality of carrier frequencies; a wired transmission medium for carrying said signal, said wired transmission medium being configured as open ended to generate reflections on said wired transmission medium of said signal; a signal analyzer for receiving the reflections and determining, based on the reflections, a transmission time of a signal along the wired transmission medium; Including, The signal analyzer includes:

2. A system configured to perform operations including: performing a search based on an estimated transmission time of the signal along the wired transmission medium and the reflections to determine the transmission time, the search being to determine which of a plurality of candidate transmission times to select for the transmission time, the plurality of candidate transmission times varying by a multiple of a step size.

2. The operation includes: performing a coarse search based on the reflections to determine the estimated transmission time, the coarse search being to determine which of a plurality of candidate transmission times to select for the estimated transmission time, the plurality of candidate transmission times used in the coarse search varying by multiples of a first step size; the search based on the estimated transmission time includes a fine search, the step size in the fine search is a second step size, and the first step size is greater than the second step size; The system of claim 1 , wherein the plurality of candidate transmission times used in the coarse search includes a first candidate transmission time, and the plurality of candidate transmission times used in the fine search includes a second candidate transmission time.

3. The system of claim 2 , wherein the coarse search is insensitive to magnitude and phase offset of a signal having the first candidate transmission time.

4. 3. The system of claim 2, wherein the coarse search includes identifying a maximum correlation based on (i) the first candidate transmission time and (ii) a sum of reflections along the wired transmission medium, reflections at an open end of the wired transmission medium, and noise, the maximum correlation corresponding to the estimated transmission time.

5. the fine search is sensitive to a magnitude and a phase offset of a signal having the second candidate transmission time; The system of claim 2 , wherein at least two of the plurality of carrier frequencies are orthogonal.

6. 3. The system of claim 2, wherein the fine search includes determining the transmission time within a predetermined range of the estimated transmission time based on a difference between (i) a value based on the reflections and (ii) a value based on the second candidate transmission time.

7. The system of claim 6 , wherein determining the transmission time includes identifying one of the values ​​based on one of the second candidate transmission times that minimizes the difference.

8. the value based on the reflection is based on a magnitude and a phase of the reflection; The system of claim 7 , wherein the value based on the second candidate transmit time is based on a magnitude and a phase of a signal having a different transmit time.

9. The system of claim 8 , wherein the different transmission times vary by single digit picoseconds.

10. The system of claim 6 , wherein the predetermined range is in the range of 200 picoseconds or greater.

11. 2. The system of claim 1, wherein the signal generator and the signal analyzer are part of a single hardware device connected to the wired transmission medium, the single hardware device comprising a tester, the tester comprising one or more processing devices programmed to perform the search.

12. The multiple carrier frequencies are up-converted based on a direct current (DC) signal; or The system of claim 1 , wherein the multiple carrier frequencies include non-upconverted carrier signals.

13. 1. A method comprising: outputting signals over a wired transmission medium based on a plurality of carrier frequencies, the wired transmission medium being configured as open ended to generate reflections on the wired transmission medium of the signals; determining a transmission time of a signal along the wired transmission medium based on the reflections; Including, Determining the transmission time includes: performing a search based on an estimated transmission time of the signal along the wired transmission medium and the reflections to determine the transmission time, the search being to determine which of a plurality of candidate transmission times to select for the transmission time, the plurality of candidate transmission times varying by a multiple of a step size.

14. Determining the transmission time includes: performing a coarse search based on the reflections to determine the estimated transmission time, the coarse search being to determine which of a plurality of candidate transmission times to select for the estimated transmission time, the plurality of candidate transmission times used in the coarse search varying by multiples of a first step size; the search based on the estimated transmission time includes a fine search, the step size in the fine search is a second step size, and the first step size is greater than the second step size; The method of claim 13 , wherein the plurality of candidate transmission times used in the coarse search includes a first candidate transmission time, and the plurality of candidate transmission times used in the fine search includes a second candidate transmission time.

15. The method of claim 13 , wherein the coarse search is insensitive to magnitude and phase offset of a signal having the first candidate transmission time.

16. 14. The method of claim 13, wherein the coarse search includes identifying a maximum correlation based on (i) the first candidate transmission time and (ii) a sum of reflections along the wired transmission medium, reflections at an open end of the wired transmission medium, and noise, the maximum correlation corresponding to the estimated transmission time.

17. the fine search is sensitive to a magnitude and a phase offset of a signal having the second candidate transmission time; The method of claim 13 , wherein at least two of the plurality of carrier frequencies are orthogonal.

18. 14. The method of claim 13, wherein the fine search includes determining the transmission time within a predetermined range of the estimated transmission time based on a difference between (i) a value based on the reflections and (ii) a value based on the second candidate transmission time.

19. 20. The method of claim 18, wherein determining the transmission time includes identifying one of the values ​​based on one of the second candidate transmission times that minimizes the difference.

20. the value based on the reflection is based on a magnitude and a phase of the reflection; 20. The method of claim 19, wherein the value based on the second candidate transmission time is based on a magnitude and a phase of a signal having a different transmission time.

21. 21. The method of claim 20, wherein the different transmission times vary by single digit picoseconds.

22. 20. The method of claim 18, wherein the predetermined range is in the range of 200 picoseconds or greater.

23. The multiple carrier frequencies are up-converted based on a direct current (DC) signal; or The method of claim 13 , wherein the multiple carrier frequencies include non-upconverted carrier signals.

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