Abstract:
Apparatus having corresponding methods and non-transitory computer-readable media comprise: a wireless local-area network (WLAN) module comprising a receiver configured to receive a WLAN signal into the WLAN module; a transmitter; and a loopback controller configured to selectively loop back the WLAN signal to the transmitter, wherein the transmitter is configured to transmit the looped-back WLAN signal from the WLAN module.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This disclosure claims the benefit of U.S. Provisional Patent Application Ser. No. 61/289,933, entitled “Using Radio Frequency [RF] Module Loopback for WLAN SoCs ATE Test,” filed on Dec. 23, 2009, the disclosure thereof incorporated by reference herein in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to integrated circuit testing. More particularly, the present disclosure relates to testing wireless local-area network (WLAN) integrated circuits. 
     BACKGROUND 
     Wireless communication networks are enjoying unprecedented popularity. Especially popular is the wireless local-area network (WLAN). In WLANs, each device includes a WLAN module for communicating over the WLAN. Each WLAN module generally includes an analog section and a digital section, and can be implemented as one or more integrated circuits. 
     To ensure quality, each WLAN module is tested as a unit before release. The WLAN module is generally sold as a unit, rather than as its constituent integrated circuits. Chip-level testing is generally limited to enabling and checking functional blocks on the silicon, and is mostly limited to the digital section. Therefore chip-level tests cannot cover all use cases for the entire WLAN module. In contrast, module-level testing involves using all of the functional blocks together to transmit and receive waveforms, and therefore extends into the analog section, including the radio-frequency modules. In order to avoid field returns of modules that fail module-level tests, it is desirable to test the entire WLAN module as a unit. 
       FIG. 1  shows a conventional WLAN module test system  100 . Referring to  FIG. 1 , test system  100  includes automated test equipment (ATE)  102  in communication with the WLAN module device under test (DUT)  104 . Each DUT  104  includes a test interface  106  that allows ATE  102  to configure DUT  104  for testing, and to extract test data from DUT  104 . For example, test interface  106  is often implemented as a Joint Test Action Group (JTAG) interface. 
     During the test, DUT  104  and ATE  102  communicate over an RF interface  108 . RF interface  108  can be an air interface, but is generally implemented as a cable to eliminate interference from sources outside the test. 
     Testing WLAN modules in the manner shown in  FIG. 1  is an expensive and time-consuming process. Considerable time is required due to the complex set up for ATE  102 , long processing time, and extra post-processing of the test data for data analysis. In addition, the tests are confined to the limits of ATE  102 , which is generally supplied by a third-party vendor. 
     SUMMARY 
     In general, in one aspect, an embodiment features an apparatus comprising: a wireless local-area network (WLAN) module comprising a receiver configured to receive a WLAN signal into the WLAN module; a transmitter; and a loopback controller configured to selectively loop back the WLAN signal to the transmitter, wherein the transmitter is configured to transmit the looped-back WLAN signal from the WLAN module. 
     Embodiments of the apparatus can include one or more of the following features. Some embodiments comprise a signal modifier configured to modify the looped-back WLAN signal; wherein the transmitter is further configured to transmit the modified looped-back WLAN signal. In some embodiments, the receiver is further configured to provide a radio-frequency signal based on the WLAN signal; the loopback controller is further configured to selectively provide the radio-frequency signal to the transmitter; and the looped-back WLAN signal transmitted by the transmitter represents the radio-frequency signal. Some embodiments comprise a downconverter configured to provide a baseband analog signal based on the WLAN signal; and an upconverter, wherein the loopback controller is further configured to selectively provide the baseband analog signal to the upconverter; wherein the looped-back WLAN signal transmitted by the transmitter represents the baseband analog signal. Some embodiments comprise a digital signal processor configured to receive a digital signal, wherein the digital signal represents the WLAN signal; wherein the loopback controller is further configured to cause the digital signal processor to selectively loop back the digital signal; and wherein the looped-back WLAN signal transmitted by the transmitter represents the looped-back digital signal. Some embodiments comprise a signal modifier configured to modify the digital signal; wherein the looped-back WLAN signal transmitted by the transmitter represents the modified digital signal. In some embodiments, the WLAN signal is a first WLAN signal, and the apparatus further comprises: a data generator configured to generate predetermined data; wherein the transmitter is further configured to transmit a second WLAN signal from the transmitter of the WLAN module, wherein the second WLAN signal represents the predetermined data. Some embodiments comprise an error checker configured to compare predetermined data with data represented by the WLAN signal. In some embodiments, the WLAN module is a first WLAN module, and the apparatus further comprises: a second WLAN module configured to transmit the WLAN signal. Some embodiments comprise automated test equipment; wherein the first WLAN module comprises a first test interface configured to communicate with the automated test equipment; and wherein the second WLAN module comprises a second test interface configured to communicate with the automated test equipment. 
     In general, in one aspect, an embodiment features a method comprising: receiving a wireless local-area network (WLAN) signal into a receiver of a WLAN module; selectively looping back the WLAN signal to a transmitter of the WLAN module; and transmitting the looped-back WLAN signal from the transmitter of the WLAN module. 
     Embodiments of the method can include one or more of the following features. Some embodiments comprise modifying the looped-back WLAN signal; and transmitting the modified looped-back WLAN signal from the transmitter of the WLAN module. In some embodiments, the WLAN signal is a first WLAN signal, and the method further comprises: generating predetermined data; and transmitting a second WLAN signal from the transmitter of the WLAN module, wherein the second WLAN signal represents the predetermined data. Some embodiments comprise comparing predetermined data with data represented by the WLAN signal. In some embodiments, the WLAN module is a first WLAN module, and the method further comprises: transmitting the WLAN signal from a second WLAN module. 
     In general, in one aspect, an embodiment features non-transitory computer-readable media embodying instructions executable by automated test equipment to perform functions comprising: causing a first wireless local-area network (WLAN) module to transmit a WLAN signal; causing a second WLAN module to selectively loop back the WLAN signal to a transmitter of the second WLAN module; and causing the second WLAN module to transmit the looped-back WLAN signal from the transmitter of the second WLAN module. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a conventional WLAN module test system. 
         FIG. 2  shows elements of a WLAN module test system according to one embodiment. 
         FIG. 3  shows elements of the golden unit of  FIG. 2  according to one embodiment. 
         FIG. 4  shows a process for the test system of  FIG. 2  to test the DUT using golden unit in loopback mode according to one embodiment. 
         FIG. 5  shows a process for the test system of  FIG. 2  to test the DUT using golden unit in data generator mode according to one embodiment. 
     
    
    
     The leading digit(s) of each reference numeral used in this specification indicates the number of the drawing in which the reference numeral first appears. 
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure provide elements of systems for testing modules such as wireless local-area network (WLAN) modules. According to these embodiments, a selected WLAN module is employed as a “golden unit” to test other WLAN modules, also referred to herein as devices under test (DUTs). The golden unit can be selected from among a group of WLAN modules based on traditional testing and the like. The described test method is more realistic than conventional testing methods because WLAN modules are tested through communication with a similar WLAN module, rather than with automated test equipment. In addition, multiple WLAN modules can be tested contemporaneously, thereby conserving test time and resources. For example, a ping-pong technique can be used where one golden unit tests multiple DUTs simultaneously by receiving from one DUT while transmitting to another DUT. 
     In a loopback mode, the golden unit can transmit WLAN signals received from the device under test (DUT) back to the DUT. The golden unit can loop back the signal at different “depths” within the golden unit. For example, the WLAN signal can be looped back in the analog or digital section of the golden unit. The golden unit can modify the signals before retransmission, for example, to add a tag to the signals, to employ a different modulation scheme, to shift the phase or frequency of the signal, and the like. 
     In a data generator mode, the golden unit can generate predetermined test data for transmission to the DUT. The DUT loops back the signal transmitted by the golden unit. The golden unit can compare the data represented by the looped-back signal with the test data generated by the data generator. The golden unit can observe payload data, packet numbers, packet error rates, and the like to judge whether the data is correct and the DUT is working correctly. 
       FIG. 2  shows elements of a WLAN module test system  200  according to one embodiment. Although in the described embodiments the elements of test system  200  are presented in one arrangement, other embodiments may feature other arrangements. For example, elements of test system  200  can be implemented in hardware, software, or combinations thereof. In some embodiments, elements of test system  200  are compliant with all or part of IEEE standard 802.11, including draft and approved amendments such as 802.11a, 802.11b, 802.11e, 802.11g, 802.11i, 802.11k, 802.11n, 802.11v, and 802.11w. 
     Referring to  FIG. 2 , test system  200  includes a golden unit  202 , a device under test (DUT)  204 , and automated test equipment (ATE)  206 . Golden unit  202  and DUT  204  include respective test interfaces  208 A and  208 B for communication with ATE  206 . In some embodiments, test interfaces  208  are implemented as Joint Test Action Group (JTAG) interfaces. During the test, golden unit  202  and DUT  204  communicate over an RF interface  210 . RF interface  210  can be implemented as an air interface, a cable, or the like. 
       FIG. 3  shows elements of golden unit  202  of  FIG. 2  according to one embodiment. Although in the described embodiments the elements of golden unit  202  are presented in one arrangement, other embodiments may feature other arrangements. For example, elements of golden unit  202  can be implemented in hardware, software, or combinations thereof. Elements of golden unit  202  can be implemented as one or more integrated circuits. For example, golden unit  202  can be implemented as a system-on-chip (SoC). 
     Referring to  FIG. 3 , golden unit  202  includes a receiver  302 , a transmitter  304 , a loopback controller  306 , a signal modifier  308 , a downconverter  310 , an upconverter  312 , a digital signal processor (DSP)  314 , a data generator  316 , an error checker  318 , an analog-to-digital converter (ADC)  320 , and a digital-to-analog converter (DAC)  322 , as well as test interface  208 A. Receiver  302  receives RF signals. Downconverter  310  downconverts the RF signals to baseband signals. ADC  320  converts the analog baseband signal to digital signals, which are processed by DSP  314 . DSP  314  provides digital signals to DAC  322 , which converts the digital signals to analog baseband signals. Upconverter  312  upconverts the baseband signals to RF signals, which are transmitted by transmitter  304 . 
     Under the control of ATE  206 , loopback controller  306  causes signals received by receiver  302  of golden unit  202  to be selectively looped back to transmitter  304 , which transmits the looped-back signals. Signal modifier  308  modifies the looped-back WLAN signals. Data generator  316  generates predetermined test data. Transmitter  304  transmits WLAN signals representing the predetermined test data. Error checker  318  compares the predetermined test data with data represented by WLAN signals received by receiver  302 . 
       FIG. 4  shows a process  400  for test system  200  of  FIG. 2  to test DUT  204  using golden unit  202  in loopback mode according to one embodiment. Although in the described embodiments the elements of process  400  are presented in one arrangement, other embodiments may feature other arrangements. For example, in various embodiments, some or all of the operations of process  400  can be executed in a different order, concurrently, and the like. 
     Referring to  FIG. 4 , at  402  ATE  206  causes DUT  204  to transmit a WLAN signal over RF interface  210 . At  404  receiver  302  of golden unit  202  receives the WLAN signal. At  406  ATE  206  causes golden unit  202  to selectively loop back the received WLAN signal. In particular, loopback controller  306  selectively loops back the received WLAN signal. 
     The WLAN signal can be looped back at different “depths” within golden unit  202 . For example, The WLAN signal can be looped back at RF. In particular, receiver  302  provides a RF signal based on the WLAN signal. Loopback controller  306  selectively provides the RF signal to transmitter  304 , which transmits a WLAN signal based on the RF signal. 
     As another example, the WLAN signal can be looped back at baseband. In particular, downconverter  310  provides a baseband analog signal based on the received WLAN signal. Loopback controller  306  selectively provides the baseband analog signal to upconverter  312 . Upconverter provides an RF signal to transmitter  304 , which transmits a WLAN signal based on that RF signal. 
     As another example, the WLAN signal can be looped back as a digital signal. In particular, DSP  314  receives a digital signal that represents the WLAN signal. Loopback controller  306  causes DSP  314  to selectively loop back the digital signal. Transmitter  304  transmits a WLAN signal based on based on the looped-back digital signal. 
     In some embodiments, at  408  ATE  206  causes golden unit  202  to modify the looped-back WLAN signal. For example, signal modifier  308  can add a tag to the looped-back WLAN signal to indicate that the signal has passed through golden unit  202 . As another example, signal modifier  308  can employ a different modulation scheme for transmitting the looped-back WLAN signal. Signal modifier  308  can also be employed to conduct negative testing by modifying the signal so as to stress DUT  204 , for example by modifying the signal to simulate errors in transmission, to shift the phase or frequency of the signal, and the like. 
     At  410  transmitter  304  transmits the looped-back signal over RF interface  210 . At  412  DUT  204  receives the looped-back WLAN signal. At  414  DUT processes the looped-back WLAN signal. At  416  ATE  206  extracts data from DUT  204  for analysis. 
       FIG. 5  shows a process  500  for test system  200  of  FIG. 2  to test DUT  204  using golden unit  202  in data generator mode according to one embodiment. Although in the described embodiments the elements of process  500  are presented in one arrangement, other embodiments may feature other arrangements. For example, in various embodiments, some or all of the operations of process  500  can be executed in a different order, concurrently, and the like. 
     Referring to  FIG. 5 , at  502  ATE  206  causes golden unit  202  to transmit a WLAN signal representing predetermined test data over RF interface  210 . In particular, data generator  316  generates predetermined test data, and transmitter  304  transmits a WLAN signal representing the predetermined test data over RF interface  210 . At  504  DUT receives the WLAN signal. 
     In some embodiments, at  506  DUT  204  processes the received WLAN signal, and at  508  ATE  206  extracts data from DUT  204  for analysis. In other embodiments, ATE  206  causes DUT  204  to loop back the received WLAN signal to golden unit  202  for error checking. In particular, at  510  DUT  204  loops back the received WLAN signal, and at  512  transmits the looped-back signal to RF interface  210 . DUT  204  can add a tag to indicate passage through DUT  204 . At  514  golden unit  202  receives the looped-back WLAN signal. At  516  error checker  318  compares the data represented by the looped-back WLAN signal with the predetermined test data generated by data generator  316 . At  518  ATE  206  extracts data from golden unit  202  for analysis. 
     In either mode, ATE  206  can characterize each tested DUT  204  by performance limits, and can bin the tested DUTs  204  according to the test data. In particular, the responses of DUTs  204  can vary according to factors such as clock accuracy, manufacturing process, frequency variation, power level variation, and the like. For example, DUTs  204  that work properly in only one frequency band can be packaged, priced, and sold as single-band units. 
     Various embodiments of the present disclosure can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof. Embodiments of the present disclosure can be implemented in a computer program product tangibly embodied in a computer-readable storage device for execution by a programmable processor. The described processes can be performed by a programmable processor executing a program of instructions to perform functions by operating on input data and generating output. Embodiments of the present disclosure can be implemented in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, processors receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer includes one or more mass storage devices for storing data files. Such devices include magnetic disks, such as internal hard disks and removable disks, magneto-optical disks; optical disks, and solid-state disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). 
     A number of implementations have been described. Nevertheless, various modifications may be made without departing from the scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.