Abstract:
A test system for testing operability of integrated circuits includes: a first IC, for modulating a first signal to generate a first modulated signal and transmitting the first modulated signal, and for receiving a second modulated signal and demodulating the second modulated signal to generate a second signal; a first loop antenna, coupled to the first IC, for receiving the first modulated signal and sending the first modulated signal back to the first IC as the second modulated signal; and a tester circuit coupled to the first IC, for generating the first signal to the first IC, receiving the second signal from the first IC, and comparing the first signal and the second signal to determine the operability of the first IC.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to IC testing, and particularly relates to a loop-back method of testing ICs. 
   2. Description of the Prior Art 
   The invention of the integrated circuit, or chip, was one of the most important developments in electronics. Integrated circuits (ICs) are present in almost all modern electrical devices from cellular phones to refrigerators. Communication systems, transport systems, manufacturing and computing all depend on the existence of ICs. Integrated circuits are also an integral part of modern transceivers. 
   Transceivers are electronic devices that have a combined receiver and transmitter. In general, a significant amount of circuitry is shared between the receiver and transmitter. As the receiving and transmitting parts of the transceiver still have some individual circuitry, it is possible for the receiving part to have functionality when the transmitting part does not (and vice versa). Therefore, to determine operability of an IC, both receiving and transmitting functions need to be tested. 
   In conventional systems, testing of transmission quality and receiving quality is performed separately. Please refer to  FIG. 1 .  FIG. 1  is a diagram of a conventional test system  100  for testing transmitting operability of an IC. The test system  100  comprises: an HF RFID IC  150 , comprising a digital processor  140 , a transmitter  130  and a receiver  120 ; a loop antenna  160 ; and a high cost tester  170 . The IC  150  will transmit a signal to the loop antenna  160 , which then passes the signal to the high cost tester  170  for monitoring the waveform of the signal. The high cost tester  170  has to perform sophisticated analysis on the transmitted signal in order to determine operability of the HF RFID IC  150 . 
   Please refer to  FIG. 2 .  FIG. 2  is a diagram of a conventional test system  200  for testing receiving operability of an IC. Components having the same function as those shown in  FIG. 1  are given the same numerals. The system  200  also includes a responder  270 , which may be a tag or a near field communication (NFC) device, and can transmit data to the IC  150  directly (active mode) or respond to a command (passive mode). The IC  150  will receive, demodulate and decode the data from the responder  270 , and if a bit error rate of the data is higher than certain thresholds, the chip will be determined to be a bad chip. 
   In both testing cases, high quality circuitry is required for confirming the accuracy of the IC. Therefore, the testing process is both time-consuming and expensive. 
   SUMMARY OF THE INVENTION 
   It is therefore an objective of the present invention to provide a method and apparatus for testing ICs that can test for transmission and receiving processes together, and requires less expensive circuitry than the related art. 
   A test system for testing operability of integrated circuits according to an exemplary embodiment of the present invention comprises: a first IC, for modulating a first signal to generate a first modulated signal and transmitting the first modulated signal, and for receiving a second modulated signal and demodulating the second modulated signal to generate a second signal; a first loop antenna, coupled to the first IC, for receiving the first modulated signal and sending the first modulated signal back to the first IC as the second modulated signal; and a tester circuit coupled to the first IC, for generating the first signal to the first IC, receiving the second signal from the first IC, and comparing the first signal and the second signal to determine the operability of the first IC. The first signal can also be sent to a second IC, modulated and transmitted to a second loop antenna, and sent back to the second IC and compared with the first signal to determine operability of the second IC. 
   A method according to the exemplary embodiment of the present invention is also provided. The method comprises: generating a first signal and sending the first signal to a first IC; utilizing the first IC to modulate the first signal to generate a first modulated signal; transmitting the first modulated signal to a first loop antenna; utilizing the first loop antenna to send the first modulated signal back to the first IC as a second modulated signal; utilizing the first IC to demodulate the second modulated signal to generate a second signal; and comparing the first signal and the second signal to determine operability of the first IC. The method can further comprise sending the first signal to a second IC; modulating the signal and sending the modulated signal to a second loop antenna; sending the signal back to the second IC; and comparing the signal with the first signal to determine operability of the second IC. 
   These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram of a conventional test system for determining transmitting operability of an IC. 
       FIG. 2  is a diagram of a conventional test system for determining receiving operability of an IC. 
       FIG. 3  is a diagram of a test system for determining operability of an IC according to an exemplary embodiment of the present invention. 
       FIG. 4  is a flowchart detailing steps of determining operability of an IC according to the exemplary embodiment of the present invention shown in  FIG. 3 . 
   

   DETAILED DESCRIPTION 
   The present invention utilizes a test system that can test for transmission and receiving quality of an IC at the same time. 
   Please refer to  FIG. 3 .  FIG. 3  is a diagram of a test system  300  according to an exemplary embodiment of the present invention. The test system  300  can be utilized for testing one IC each time or two or more ICs at the same time. This embodiment shows the case when two ICs are being tested at the same time, but is not meant to limit the scope of the invention. The test system  300  comprises: a first IC  350  and a second IC  450 , a first loop antenna  360  coupled to the first IC  350 , a second loop antenna  460  coupled to the second IC  450 , and a tester circuit  310  coupled to the first IC  350  and the second IC  450 . As in the conventional test systems  100 ,  200  the ICs  350 ,  450  are HF RFID ICs, and respectively comprise a digital processor  340 ,  440 , a transmitting circuit  330 ,  430 , and a receiving circuit  320 ,  420 . 
   For simplicity, the following example will refer to testing of the first IC  350  only. Please note that the testing method for the second IC  450  is identical. The tester circuit  310  generates a first signal and sends the first signal to the first IC  350 . The digital processor  340  modulates the first signal and sends the modulated signal to the first loop antenna  360  through the transmitting circuit  330 . The IC  350  is therefore acting as a transmitter at this point. The first signal is at a baseband frequency and modulation of the first signal converts the first signal up to radio frequency (RF). When the loop antenna  360  receives the first modulated signal (RF signal) it will send the modulated signal back to the first IC  350  as a second modulated signal. The first IC  350  receives the second modulated signal through the receiving circuit  320  and the digital processor  340  de-modulates the signal to convert the signal back down to baseband frequency (second signal). The IC  350  is therefore acting as a receiver at this point. 
   The de-modulated signal (second signal) is then sent to the tester circuit  310  where it can be compared with the first signal. As no other processes apart from modulation and de-modulation have been performed on the signals, the second signal should be the same as the first signal. Therefore, by comparing the two baseband signals with each other, the operability of the first IC  350  can be directly determined. As the comparison takes place between two signals at baseband frequency, the comparison operation is much less complicated than the signal analysis required by the prior art. Furthermore, as the signal has undergone both transmitting and receiving processes, a fault in the IC  350  can be instantly determined. As it is not necessary to know which function (receiving or transmitting) of the IC  350  is faulty, determination of inoperability can be performed more efficiently than in the related art. 
   As mentioned above, testing of the second IC  450  can be performed in exactly the same way. The tester circuit  310  will send the same first signal to the second IC  450 . Although the second IC  450  may have a different modulation index from the first IC  350 , once the signal is returned to the second IC  450  by the second loop antenna  460  and demodulated, the returned signal will be equivalent to the first signal originally generated by the tester circuit  310  (provided the second IC  450  is operable). For clarity of illustration, the returned signal from the second IC  450  has been annotated as fourth signal in  FIG. 3 . 
   Please refer to  FIG. 4 .  FIG. 4  is a flowchart of the operation of the test system. The steps are as follows: 
   Step  400 : Start; 
   Step  402 : Generate a first signal; 
   Step  404 : Utilize an IC to modulate the first signal to generate a first modulated signal; 
   Step  406 : Send the first modulated signal to a loop antenna; 
   Step  408 : Utilize the loop antenna to send the first modulated signal back to the IC as a second modulated signal; 
   Step  410 : Utilize the IC to demodulate the second modulated signal to generate a second signal; 
   Step  412 : Compare the first signal and the second signal; 
   Step  414 : Are the first signal and the second signal the same? If no go to Step  416 ; if yes go to Step  418 ; 
   Step  416 : IC is inoperable; 
   Step  418 : IC is operable. 
   As shown in  FIG. 3 , the test system  300  can test two ICs at the same time by using the single tester circuit  310 . The first signal is simultaneously input to the first IC  350  and the second IC  450 , and then modulated and respectively sent to the first loop antenna  360  and the second loop antenna  460  as a first modulated signal and third modulated signal respectively. If the first IC  350  and second IC  450  have different modulation indexes then the first modulated signal and third modulated signal will not be equivalent to each other. As mirror operations are performed on the first signal (i.e. modulation and de-modulation), however, it does not matter if these signals (first modulated signal and third modulated signal) are different as determination of operability depends on a comparison between signals (first signal vs. second signal and first signal vs. fourth signal) and not on the content of the signal itself. 
   The first loop antenna  360  and the second loop antenna  460  respectively send the first modulated signal and third modulated signal back to the first IC  350  and second IC  450  as a second modulated signal and a fourth modulated signal. The digital processor  340  and the digital processor  440  respectively demodulate the second modulated signal and fourth modulated signal to respectively generate a second signal and a fourth signal to be sent to the tester circuit  310 . The tester circuit  310  then compares the second signal and fourth signal (baseband signals) with the originally generated first (baseband) signal. If all signals are the same then it can be confirmed that the first IC  350  and second IC  450  are in working order. If either the second signal or the fourth signal is not the same as the first signal then either the transmission function of the corresponding IC is broken, the receiving function is broken, or both functions are broken. As an IC is unworkable if one function is broken, it is unnecessary to determine which particular function is broken. 
   The tester circuit  310  can determine the accuracy of the IC utilizing various methods. A preferred method is to count the transitions of the generated signal and the transitions of the received signal. It is also possible to compare the data, i.e. the waveforms, although this method will take longer than the aforementioned one. All methods of comparing the generated signal with the received signal in the testing circuit fall within the scope of the invention. One exemplary example of comparing the originally generated first (baseband) signal with either the second signal or the fourth signal (baseband signals) is to count the number of rising edges or falling edges of both of the baseband signals and then determine if the numbers are identical. If the number of rising/falling edges of the first signal is the same as that of the second or the fourth signal then the first signal is determined to be identical to the second signal or the fourth signal. 
   It should be noted that the method and circuit of the present invention can be utilized for all coding types of ICs, as the signal received by the IC  350 ,  450  is demodulated and then directly compared with the signal generated by the tester circuit  310 . 
   By combining testing of receiving and transmitting capability of an IC into a single testing step, the present invention is more efficient and less expensive than conventional testing methods. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.