Optimized EVM Testing for IEEE 802.11a/n RF ICs

2011 Sixteenth IEEE European Test Symposium

Verhelst

et al. 2011

Error Vector Magnitude (EVM) is a system-level parameter that is specified for most advanced communication standards. EVM measurement often takes extensive test development efforts, tester resources, and long test times. Since EVM is analytically related to system impairments, which are typically measured in a production test environment, it can be eliminated from the test list if the relations between EVM and system impairments are derived in a manner that is independent of the circuit implementation and manufacturing process. In this paper, we focus on the WLAN standard, and derive the relations between EVM and three of the most detrimental impairments for QAM/OFDM based systems: IQ imbalance, non-linearity, and noise. Simulations and hardware experiments show that the accuracy of the analytical models is in par with a direct EVM measurement with a reasonable test time.

Section: Prior Workmentioning

confidence: 99%

“…The complete receive operation needs to be duplicated by the test engineer and incorporated into the test program. This operation requires complex procedures [4], [5] and add considerable test time. Moreover, EVM measurement places a burden on the computational resources [6], and generates a bottleneck in increasing the multi-site ratio.…”

Section: Introductionmentioning

confidence: 99%

Extraction of EVM from Transmitter System Parameters

2011 Sixteenth IEEE European Test Symposium

Verhelst

et al. 2011

“…An optimization method for EVM measurement that reduces the overall test time for EVM characterization is presented in [2]. The goal is to limit the number of symbols that need to be transmitted/received within one frame as dictated by the normal operation mode.…”

Section: Introductionmentioning

confidence: 99%

Built-in EVM measurement for OFDM transceivers using all-digital DFT

Yılmaz

2009 International Test Conference

et al. 2009

In this paper, we present a technique to enable accurate built-in measurement of EVM for OFDM transceivers. This measurement technique only relies on the decoded bit pattern, and does not require any additional test equipment. In order to accurately predict EVM without using analog signal analysis, we intentionally code more symbols into the bit pattern in test mode, which enables the decoding of IQ signals in finer granularity. We present an innovative DFT technique to measure EVM on-chip with very little overhead. We also provide an analytical framework to determine how the DFT technique needs to be implemented. Experimental results using MATLAB simulations and hardware measurements confirm the accuracy of the proposed technique.

“…The goal in [2] is to limit the number of symbols that need to be transmitted/received within one frame as dictated by the normal operation mode. The complete receive operation is duplicated and conducted at the tester using a golden receiver on the load board.…”

mentioning

confidence: 99%

“…Some of the steps of the receive operation require compute-intensive algorithms, sometimes requiring multiple passes through the IQ samples [2]. This computational overhead imposes a bottleneck in increasing the multi-site ratio during EVM testing.…”

mentioning

confidence: 99%

Built-In EVM Measurement With Negligible Hardware Overhead

Yılmaz¹,

2014

IEEE Des. Test

h BECAUSE OF ITS soft capacity and frequency diversity, orthogonal frequency division multiplexing (OFDM) has become the prevailing modulation scheme for modern RF transceiver systems. Modulation accuracy, specified in terms of error vector magnitude (EVM), is one of the most important transmitter parameters specified for OFDM transceivers. EVM encapsulates many nonidealities of the transmitter, including inter symbol interference, mismatches, nonlinearity, phase noise and spurs, and carrier leakage [1]. It is typically one of the few parameters specified for the transmitter and needs to be guaranteed.Recently, several researchers have proposed techniques for simplified EVM measurements. The goal in [2] is to limit the number of symbols that need to be transmitted/received within one frame as dictated by the normal operation mode. The complete receive operation is duplicated and conducted at the tester using a golden receiver on the load board. In [3], the authors propose an EVM measurement method that requires less number of symbols by increasing the sensitivity of EVM to transceiver system noise. A computationally efficient EVM measurement method for phase-only modulation schemes is presented in [4]. EVM test sequence is reduced in [5] by selecting sensitive corner cases into the test vector to shrink the test sequence.While there has been significant progress in reducing the overhead of EVM measurements, important challenges still remain, especially when it comes to multi-site testing. Multi-site environments typically share high-frequency channels that complicate board design and limit the number of parallel tested devices. Moreover, characterization of EVM requires sending many symbols spread over multiple frames and conducting the overall receive operation including the channel characterization and synchronization. The I and Q signals need to be captured and analyzed at the tester requiring access to these signals. Moreover, the complete receive operation needs to be duplicated by the test engineer and incorporated into the test program. This operation requires complex procedures to synchronize the transmitted and received frames and to estimate the channel characteristics. These steps complicate the test development process and may result in long test development times.The need to analyze the IQ signals, rather than the bit pattern, also puts a high burden on the tester. The IQ signals are typically digitized with a resolution of 8-12 bits [6]. This means that measuring EVM requires 16 to 24 bits of digital bandwidth between the tester and the device under test (DUT) just for Editor's notes: This article presents an all-digital, built-in method for measuring EVM that alleviates the need for sophisticated external test equipment and speeds up test application time.VHaralampos Stratigopoulos, TIMA Laboratory