Setting up a TEDS Measurement

This topic provides information to connect your signal to an 89600 VSA software and successfully demodulate TEDS signals. A typical measurement includes the following measurement setup procedure (each step is discussed in the following text):

Connect Your Signal to the VSA
Configure Measurement Setup and Input Parameters
Configure the Demodulator
Run the Measurement

TEDS Measurement Setup Information

Connect Your Signal to the VSA
- Single channel connection
  
  Connect the signal to the Channel 1 on the measurement hardware.
  
  Click Input > Channels and select 1 Channel. Multiple channels can be selected but the demodulator will only use Channel 1.
- I+jQ connection
  
  Connect the I and Q signals to the measurement hardware. To configure the VSA, select Input > Channels > I + jQ.
  Notes for I+jQ input:
  - Selecting an I+jQ configuration enables DC coupling.
  - Use User Correction to correct for any offset or gain imbalance between the I and Q signals.
  - Range is set independently for the I and Q inputs, but can be coupled by selecting the Couple Paired Channels parameter.
- Recorded signal
  
  Recall the recorded signal by selecting File > Recall > Recall Recording
  
  The center frequency and input range will be set by the recording.
For more information about your specific measurement hardware, see the Measurement Hardware book.
Configure Measurement Setup and Input Parameters
1. Set the Center Frequency
  
  The 89600 VSA's center frequency must be set to within approximately 10 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second). of the signal's carrier frequency for the demodulator to lock to the signal.
2. Set the Frequency Span
  
  When selecting a frequency span, select the narrowest span that includes all of your signal components (a span that is slightly larger than the bandwidth of your signal). When making ACP Adjacent Channel Power: The power from a modulated communications channel that leaks into an adjacent channel. This leakage is usually specified as a ratio to the power in the main channel, but is sometimes an absolute power. PvT measurements, be sure to include the ACP channel. If you select a span that is too narrow, your measurement may have excessive errors or the VSA may lose carrier lock. Using the Preset to Standard configuration settings will select a default span that should work well.
  
  See the Span topic for details on setting the frequency span.
3. Configure the Input Range
  
  The input range must be set correctly to obtain accurate measurements. Input ranges that are too low overload the measurement hardware's ADC Analog-to-Digital Converter. Input ranges that are too high increase noise, which increases errors reported in error summary data, such as EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format..
4. Set up triggering
  
  The default triggering mode is set to FreeRun. However, a different type of triggering can be configured using the parameters on the Input > Trigger tab.
5. Verify the input signal and initial parameter settings
  
  View the signal in the frequency domain (Spectrum trace) to verify the parameters set.
Configure the Demodulator
1. Set the demodulator to TEDS
  
  Select MeasSetup > Measurement Type > Other standard formats > TEDS (TETRA2) to enable the TEDS demodulator properties and measurement parameters. You can then access the TEDS parameters using MeasSetup > TEDS (TETRA2) Demod Properties.
2. Set the Channel Bandwidth
  
  Your choices are: 25kHz, 50kHz, 100kHz, and 150kHz. This must be selected before the Preset to Standard button can be used.
3. Preset to Standard
  
  You can manually configure the demodulator parameters or you can use the Preset to Standard parameter. Preset to Standard automatically sets up the demodulator parameters, including frequency span, ACP Offset, and ACP Bandwidth, to one of the provided standard defaults. The presets are based on the channel BW that is selected.
4. Select the Slot Format
  
  The VSA demodulates Normal Uplink, Normal Downlink, Random Access, and Control Uplink signals. Therefore you must select the desired Uplink or Downlink direction. Downlink refers to the fixed network equipment transmitted signal and Uplink refers to subscriber transmitted signal.
  
  If Preset to Standard was used, the Slot Format was selected in that process.
5. Set the Modulation Type
  
  Your choices are M-4QAM (QPSK Quadrature phase shift keying), M-16QAM, and M-64QAM.
6. Set the Search Length
  
  Enter the length of the captured signal you want to use for searching for particular signal characteristics. The Search Length minimum is 14.167mSec for Normal Downlink and Normal Uplink and minimum 7.083mSec for Random Access and Control Uplink. The minimum is dependant on the Slot Format and the PvT Off Analysis Time. Note that increasing Search Length decreases the measurement update rate.
7. Set Mirror Frequency Spectrum (when necessary)
  
  The TEDS demodulation provides a feature that lets you configure the demodulator to conjugate the complex time-domain waveform. This has the effect of flipping the spectrum around the VSA's center frequency. This feature is useful when the TEDS signal is inverted, or flipped due to an IF down-conversion.
Run the Measurement

Observe results using (for example) Trace > Channel 1 Overlaid > IQ Meas Time (Constellation diagram). If you experience difficulties, see Troubleshooting.