background image

 

 
 

TN_IDA_1068_E_IQ_data 

4 / 8 

Subject to change 

Figure 5: Simplified block diagram of NRA and IDA for 

recovering the IQ data. From the A/D converter 

onwards, it corresponds to the receiver structure 

shown in figure 3 

Table 1: IQ data handling facilities of NRA and IDA 

                                                                                  cos(

ω

ν

t + 

φ

ν

 
 
 
 
                                                            A 
                                                                 D 
 
                                     cos(

ω

0

t) 

 
 
                                                                                  -sin(

ω

ν

t + 

φ

ν

Recovering the IQ data: How it is done in NRA and IDA 

 
NRA and IDA combine analog and digital techniques for signal analysis: 
a classic heterodyne receiver for pre-selection is followed by a digital 
analyzer for fine selection and further processing. To help you 
understand IQ data recovery, the block diagram can be simplified as 
follows: 
 
 
 
 
 
 
 
 
 
 
 
 
Following pre-selection, frequency conversion, and A/D conversion, the 
received signal is mixed down to a base band and split into its in phase 
and quadrature components in the process. The subsequent filters limit 
the bandwidth. It should be noted here that the frequency of the IQ 
demodulator can only be roughly selected because the exact signal 
frequency is unknown; the phase is initially arbitrary. Generally, too, the 
selection filter does not correspond to that used in the correct receiver, 
as the filter parameters are also not known at this point in time. The 
parameter settings merely serve to allow the part of the spectrum of 
interest to be saved as IQ data. 
 
There are basically two modes for storing the IQ data: block mode and 
streaming mode. 
 
A maximum 250,000 points per block are available in 

block mode

. The 

maximum bandwidth here is 32 MHz. NRA and IDA capture the data 
block by block, i.e. take sections from the time signal. Time gaps in the 
recording thus occur between the blocks. The advantage of block mode 
is the high bandwidth. 
 
In 

streaming mode

, the NRA captures the data continuously and 

outputs them without interruption via one of the interfaces. The 
maximum bandwidth is 400 kHz. The advantage of streaming mode is 
that the data are without time interruptions. The limitation of the 
bandwidth to 400 kHz is a disadvantage. 

 

D

isplay 

Demo

dulate

 

Store intern

al

ly / 

SD c

ard 

Block m

ode

 

Streaming m

ode

 

IDA 

• •

 

1)

 

 

– 

NRA 

2) 

 

 

 

 

 

1)

 Export using IDA-Tools or on SD card 

2)

 With NRA demo program 

Summary of Contents for NRA Series

Page 1: ...ms To transmit data wirelessly it must be modulated onto a suitable usually high frequency carrier signal This gives a basic setup as shown in figure 1 The demodulator must perform exactly the opposite function to the modulator The receiver must also be able to cope with the impairments to the modulated signal that are added as it passes through the communications channel The type of modulation ha...

Page 2: ...acilities for recording the unknown signal in the form of IQ data so that it can subsequently be subjected to a more precise investigation IQ data Generally speaking the IQ data consists of pairs of data describing an instantaneous time signal in the complex plane as shown in figure 2 I stands for the in phase component which has a phase angle of 0 relative to the converted carrier and which there...

Page 3: ... and converts it into the transmission frequency band After addition of the I and Q components the real band limited signal can be transmitted in a radio channel The received signal together with any captured interference is converted back to the base band again and band limited by the IQ demodulator in the receiver so that the original payload signal or data stream together with the interference ...

Page 4: ...ause the exact signal frequency is unknown the phase is initially arbitrary Generally too the selection filter does not correspond to that used in the correct receiver as the filter parameters are also not known at this point in time The parameter settings merely serve to allow the part of the spectrum of interest to be saved as IQ data There are basically two modes for storing the IQ data block m...

Page 5: ...pe mode using Extras Go to The IDA uses the same settings made in Spectrum mode for this The Time Span and Channel Bandwidth CBW settings need to be made depending on whether you want to view or store the signal The CBW has to be set such that the Nyquist Shannon sampling theorem is at least fulfilled if the signal is to be displayed and further processed This means that the CBW must be at least t...

Page 6: ...e entire communication and evaluation into your own application You can see from figure 8 that each IQ block must be requested individually by the PC in block mode In streaming mode the NRA communicates with the PC via a remote link and sends the IQ data as a stream over a stream link Both links are via a single physical interface Once started the NRA transmits IQ data continuously over the stream...

Page 7: ...hows only those values that correspond to the line digit rate and which form the constellation diagram It should be noted that you cannot discern which of the four states 0 90 180 or 270 corresponds to the actual phase This information can be obtained for example by synchronization to IQ sequences known to the receiver that are intended for this purpose If this information is also known the states...

Page 8: ... 2013 Narda Safety Test Solutions GmbH The name and logo are registered trademarks of Narda Safety Test Solutions GmbH and L 3 Communications Holdings Inc Trade names are the trademarks of their respective owners Abbreviations AM Amplitude modulation FM Frequency modulation PM Phase modulation Frequency and phase modulation are forms of angle modulation ASK Amplitude shift keying FSK Frequency shi...

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