The new solution accelerates the verification of the UWB Physical Layer

Ultra-Wideband Wireless Technology is favored by more and more emerging wireless technologies due to its high transmission rate, low power, and small scale features. However, its very high modulation bandwidth (usually higher than 500 MHz) and relative bandwidth (> 20%) pose many challenges to the development and testing of the ultra-wideband product. The traditional general testing method is insufficient in the face of the physical layer characteristics of UWB.
First, signal reception and analysis: the traditional spectrum analyzer is a narrowband receiver, which cannot measure the real-time spectrum of Ultra-Wideband signals, you can only obtain the spectrum envelope of a MB-OFDM signal using a function of the maximum hold class.
The real-time analysis bandwidth of the vector signal analyzer generally does not exceed 120 MHz. It can only barely measure the modulation domain characteristics of some low-speed signals at a specific time, and cannot fully meet the requirements of the MB-OFDM physical layer verification.
In the signal generation, MB-OFDM also has a high requirement. A common test method is to use a vector signal source. However, the popular vector signal source built-in IQ baseband generator generally only generate dozens of megabytes of modulation bandwidth capacity, for the MB-OFDM at least 528 MHz, more than GHz demand is inevitably unable to do. Therefore, the feasible solution is the combination of high-performance vector signal sources and high-performance arbitrary waveform generators.
In terms of the probe method, all the basic components of MAC/PHY tested (see figure 3) are generally encapsulated in one chip due to high integration. Different from general software radio systems, verification testers may no longer be able to have corresponding test points on baseband, intermediate frequency, and RF-and RF antennas become the only feasible test port for interoperability verification.
Finally, wireless devices are different from popular wired applications (such as high-speed serial devices ). Therefore, it is also an important consideration for consumer electronics developers to use existing tools and improve the utilization of instruments.

A new physical layer verification Solution
In view of the challenges in the test of MB-OFDM system, the company proposed a verification test scheme: In the receiver, using the wide band receiver-oscilloscope in the universal instrument as the signal collection equipment, with specially designed for the MB-OFDM signaling demodulation software TDSUWBWiMedia V2 for Signal Analysis; transmitter, a band can use the latest AWG7102 directly generate, the signal of a higher frequency band can be obtained using a dual-channel AWG7000 series arbitrary waveform generator in combination with the modulation. These hardware testing devices are also widely used in R & D and testing of high-speed serial signals, so they can improve device utilization and maximize resource efficiency.
The configuration and working principle of this general testing system are shown in Figure 1.

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: Function diagram of the RF chip

In this system, the selection of oscilloscope is very important. In a common wired test, the oscilloscope is generally used to follow the rule of "Three to five harmonic waves of captured signals. When the oscilloscope is used as the RF signal receiver, we have the "75% bandwidth principle": the frequency response of the ordinary oscilloscope (including the amplitude-frequency characteristics and phase-frequency characteristics ), from DC to 75% of the calibration bandwidth is ideal, that is, the flat amplitude-frequency characteristics and linear phase response are close to the ideal. Therefore, when selecting an oscilloscope to verify the MB-OFDM signal, you need to use the upper limit of the frequency band divided by 0.75, to obtain the minimum bandwidth requirements of the oscilloscope. For example, if the maximum carrier frequency of BG5 is 10.56 GHz, the bandwidth of the oscilloscope as the receiver should be (10.56 GHz/0.75 = 14.08 GHz); the lowest BG1 band (the highest carrier frequency is about 4.75 GHz) the signal receiver also needs at least GHz bandwidth. The DPO, DSA71604, and DPO/DSA72004 of tech are the most powerful options for this type of application oscilloscope in the market. They have a real analog bandwidth over 16 GHz and can meet the needs of all ultra-wideband band groups, it also covers the Ku band and the following general applications, while taking into account the next generation of Serial Standards (such as pcie ii, sata iii, 2x XAUI, FBD, XFI, etc) three to five harmonic or above; in addition, the burst transmission time in MB-OFDM signaling is generally longer (such as BeaconSlotLength is 85us ), the oscilloscope must have a long storage depth to capture rich waveform information for analysis and use, the DPO/DSA70000 series comes standard with 10 M, and an optional M high-speed memory. It can easily capture up to 8 ms signals at a sampling rate of 50 Gs/s, this capability far exceeds the capture length of 50 US Under the 40GS/s sampling rate of similar solutions of other vendors. Of course, sufficient information also ensures the tester's confidence in the analysis results.

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: Green representatives of available frequencies in various regions are available)

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Function diagram of RF chip

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A general closed-loop test system that can meet the requirements of MB-OFDM Signal Verification and high-speed serial signal testing

TDSUWB WiMedia V2 is the first professional automatic analysis software in the industry. It can complete "one-click" Verification measurement. For a specified data packet or all captured data packets, it can implement the following functions: Automatic Identification of frequency groups; automatic identification of time frequency Codes (TFC ); the system automatically analyzes the modulation mode, modulation rate, and performs demodulation. It displays the constellation chart, RMS and peak value (EVM) for calculating the vector amplitude error ); all the analyzed data (including the analysis time, signal source, and all the above analysis results) can be archived (see figure 5 ). At the same time, the software also has a common real-time spectrum analysis function, can analyze the spectrum characteristics of the MB-OFDM, automatically apply the PSD (power spectrum density) template for spectrum consistency test (see Figure 6 ); it can also analyze the time-frequency characteristics of RF signals with time changes, such as linear frequency modulation signals (see figure 7 ).

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Analysis of MB-OFDM Signaling

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PSD template consistency test (Band 2)

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The real-time spectrum analysis function of the TDSUWB package makes the Chirp signal abnormal and clear at a glance.
In terms of signal sources, the new AWG7000 series provided a sampling rate of up to 20 GB and an output bandwidth of GHz, which can directly generate a signal (8) in band 1 ).

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BG1 signal directly captured by the oscilloscope by AWG7102
For signals in higher frequency bands, the two-channel models in the AWG7000 series can output 2.5 Gbit/s (4 times oversampling rate) of the baseband for modulation of I and Q, this allows you to easily meet the ultra-high modulation bandwidth requirements of UWB systems, including mb-ofdm, DS, and pulse. Of course, the features of AWG7000 also determine that AWG7000 has many advantages in generating signals that are hard to achieve by traditional signal sources such as high-speed pre-weighting/deweighting, pulse amplitude modulation (PAM), and disks, it is a well-balanced signal source solution.

It is worth mentioning that the AWG7000 sampling rate and the output bandwidth of GHz can completely reproduce the signals collected by the popular oscilloscope-now you can use the oscilloscope to collect "standard" signals, then, various other signal elements are added as needed, and the AWG7000 series are used for playback to implement a complete closed-loop test system.
Summary
With the development of technology, more and more semiconductor and consumer electronics vendors will face challenges from ultra-broadband radio.
Good testing and verification devices can help developers solve problems quickly, shorten the time to push products to the market, and increase profits. The test solution provided by tech can efficiently verify the physical layer of the MB-OFDM system. The test project is complete, the operation is simple, and the results are intuitive, this allows users to easily meet the challenges without increasing their investment.