Communication unit with analog test unit

Abstract

Various devices and techniques for testing an analog portion of communication devices are disclosed. Such devices may include a communication unit and an analog test unit. The analog test unit may be configured to test analog portions of the communication unit and communicate information regarding testing to an external test unit. The analog test unit may also be configured to perform an analysis of a test signal that is output by a transmitter portion, looped back to a receiver portion, and subsequently received by the analog test unit. The analog test unit may also be configured to calibrate a DC offset of a receiver chain of the communication unit. The analog test unit may also be configured to perform a nonlinearity test on one or more ADCs and/or DACs of the communication unit.

1 . An apparatus, comprising:
 a device on a single integrated circuit, wherein the device includes:   a communication unit configured to perform communication via an analog external interface, wherein the communication unit includes a receiver chain; and   an analog test unit having a DC offset calibration unit that is configured to calibrate a DC offset of the receiver chain by measuring a residual DC offset of the receiver chain and providing an offset value to the receiver chain that causes the receiver chain to reduce the DC offset.   
     
     
         2 . The apparatus of  claim 1 , wherein the analog test unit is configured to convey the offset value to a test unit external to the device. 
     
     
         3 . The apparatus of  claim 1 , wherein the receiver chain includes a digital to analog converter (DAC), wherein the DC offset calibration unit is configured to provide the offset value to the DAC, causing an adjustment of the DC offset of the receiver chain in the analog domain. 
     
     
         4 . The apparatus of  claim 3 , wherein the analog test unit includes an additional DC offset unit that is configured to adjust a DC offset of a digital version of a signal processed by the receiver chain. 
     
     
         5 . The apparatus of  claim 1 , wherein the DC offset calibration unit is configured to select the offset value based on a gain setting of the receiver chain. 
     
     
         6 . The apparatus of  claim 1 , wherein the communication unit includes one or more additional receiver chains, and wherein the DC offset calibration unit is configured to calibrate DC offsets of the receiver chain and the one or more additional receiver chains in parallel. 
     
     
         7 . A device, comprising:
 an analog external interface;   a digital external interface;   a communication unit configured to perform communication via the analog external interface, wherein the communication unit includes an analog to digital converter (ADC); and   an analog test unit configured to perform a nonlinearity test on the ADC by:
 receiving a low-frequency signal from the ADC; 
 filtering the low-frequency signal with a high pass filter to produce a set of high frequencies; 
 measuring a strength of the set of high frequencies; and 
 providing information indicative of the measured strength to a test unit external to the device, wherein the external test unit is configured to determine whether nonlinearity is present in the ADC based on the measured strength; 
   wherein the device is a single integrated circuit.   
     
     
         8 . The device of  claim 7 , wherein the analog test unit includes a low-frequency tone generator that is configured to provide the low-frequency signal to the ADC to be processed. 
     
     
         9 . The device of  claim 7 , wherein the external test unit is configured to provide the low-frequency signal to the ADC to be processed. 
     
     
         10 . The device of  claim 7 , wherein for a received frequency signal that has also been processed by a digital to analog converter (DAC) of the communication unit, the external test unit is configured to determine whether nonlinearity is present in the DAC based on the measured strength. 
     
     
         11 . The device of  claim 7 , wherein the analog test unit is configured to perform the nonlinearity test on a plurality of ADCs located in different receiver chains of the communication unit in parallel. 
     
     
         12 . A method, comprising:
 providing a device on a single integrated circuit including a communication unit configured to perform communication via an analog external interface, wherein the communication unit includes a receiver chain, and an analog test unit having a DC offset calibration unit;   calibrating a DC offset of the receiver chain by measuring a residual DC offset of the receiver chain; and   providing an offset value to the receiver chain that causes the receiver chain to reduce the DC offset.   
     
     
         13 . The method of  claim 12 , further comprising conveying the offset value to a test unit external to the device. 
     
     
         14 . The method of  claim 12 , wherein the receiver chain includes a digital to analog converter (DAC), further comprising providing the offset value to the DAC with the DC offset calibration unit and adjusting the DC offset of the receiver chain in the analog domain. 
     
     
         15 . The method of  claim 14 , wherein the analog test unit includes an additional DC offset unit, further comprising adjusting a DC offset of a digital version of a signal processed by the receiver chain. 
     
     
         16 . The method of  claim 12 , comprising selecting the offset value based on a gain setting of the receiver chain. 
     
     
         17 . The method of  claim 12 , wherein the communication unit includes one or more additional receiver chains, further comprising calibrating DC offsets of the receiver chain and the one or more additional receiver chains in parallel. 
     
     
         18 . A method, comprising:
 providing a device on a single integrated circuit including an analog external interface, a digital external interface, a communication unit configured to perform communication via the analog external interface, wherein the communication unit includes an analog to digital converter (ADC), and an analog test unit configured to perform a nonlinearity test on the ADC;   receiving a low-frequency signal from the ADC;   filtering the low-frequency signal with a high pass filter to produce a set of high frequencies;   measuring a strength of the set of high frequencies;   providing information indicative of the measured strength to a test unit external to the device; and   determining whether nonlinearity is present in the ADC based on the measured strength with the external test unit.   
     
     
         19 . The method of  claim 18 , wherein the analog test unit includes a low-frequency tone generator, further comprising providing the low-frequency signal to the ADC to be processed with the low-frequency tone generator. 
     
     
         20 . The method of  claim 18 , wherein the external test unit is configured to provide the low-frequency signal to the ADC to be processed. 
     
     
         21 . The method of  claim 18 , further comprising determining whether nonlinearity is present in the ADC based on the measured strength with the external test unit for a received frequency signal that has also been processed by a digital to analog converter (DAC) of the communication unit. 
     
     
         22 . The method of  claim 18 , further comprising determining whether nonlinearity is present on a plurality of ADCs located in different receiver chains of the communication unit in parallel.