Exercise on RX and TX modules ERXTX

1
Exercise on RX and TX modulesERXTX

• Per Zetterberg
• Signal Processing
• Royal Institute of Technology

2
Goals

• To get some experience of RF-hardware.
• Insight into the operation of test-bed.
• Learning how to operate the FSH spectrum
  analyzer.
• Being able to fail-search the equipment if it
  doesnt work.

3
Preparations

• Read section 1.1-1.6, 1.9 of the report WIDELAB
  equipment base IR-S3-SB-0316.
• Find five errors in the equations (Latex errors
  doesnt count).
• Re-derive the equations of section 1.9 assuming a
  low-LO in both receiver and transmitter, using an
  NMT-450 filter in the transmitter.
• Install the software required for the spectrum
  analyzer (FSH-view), and read instructions so you
  know how to measure spectrums and download them
  to the computer.

4
Low-LO versus High-LO

• Assume frequency of present signal is w1,
• frequency of wanted signal is w2.
• Low-LO Multiply with signal of frequency w2-w1
• cos(w1t ) cos((w2-w1)t)cos(w2t)cos(/2w1-w2)t)
• High-LO Multiply with signal of frequency w2w1
• cos(w1t ) cos((w1w2)t)cos(w2t)cos((2w1w2)t)

5
Tasks with the equipment 1(4)

• In room Axxx one RX module is placed, together
  with FSH spectrum analyzer, two signal
  generators, a 69.990MHz oscillator and a
  tone-generator.
• In the following description numbers in quotes
  () refer to the numbering in Figure 1 of
  IR-S3-SB-0316 .
• Before doing anything else, mount a 10dB
  attenuator and a high-pass filter xxxx on the
  input of the FSH, as an extra safety precausion.
• Connect the inputs 5 and 6 to the TTL
  swicthing box put the switches in the state
  such that the step attenuator 20 has its
  minimum attenuation.
• Connect all DC signals according to the
  specifications in report IR-S3-SB-0316.
• Before connecting the 69.990MHz generator,
  connect it to the FSH and measure the spectrum
  and save it on the computer explain the result.
  Determine the appropriate amount of attenuation
  to achieve the required 7dBm LO level.
• Connect the 69.990MHz generator to the LO2 input
  of the RX module, including the appropriate
  attenuators to achieve 7dBm.
• Set-up a signal generator to be used as LO1 input
  with the correct amplitude and frequency using
  the low LO (see previous slide) principle. The
  input signal will be of 455.850 frequency.
• Generate a signal of 455.850 MHz frequency and
  -100dBm amplitude using a signal generator and
  connect to the input.
• Disconnect the filter labelled 12 (reffering to
  Figure 1 of IR-S3-SB-0316) in the receiver and
  measure the spectrum using the FSH. Log the
  spectrum using the spans 0-3GHz, 0.5-1GHz, and
  455.830MHz to 455.870MHz with 1kHz resolution
  bandwidth in the last case. Explain what you see
  including power levels.

6
Tasks with the equipment 2(4)

• Re-connect the filter 12.
• Disconnect the I output of the mixer 19.
  Measure the spectrum using spans 0-1GHz, and
  69.970MHz to 70.010MHz, in the latter case with
  1kHz resolution band-width. Explain what you se
  including power levels.
• Re-connect the output of the mixer 19.
• Disconnect the cable going to the R input of
  the mixer 24. Measure the spectrum as in point
  11 above, including power levels and comment on
  the reletaion to spectrum measured under point 2.
• Change the attenuator levels using the TTL
  switching box and measure the signal level again.
  Explain the results.
• Re-connect the cables going in to the mixer 24.
• Measure the base-band output signal on an
  oscilloscope. Estimate the frequency.
• Change the frequency of the input signal a kHz or
  so. Re-estimate the frequency of the base-band
  signal. Explain the result. Also try changing the
  amplitude of the input signal and watch results
  on the oscilloscope.

7
Tasks with the equipment 3(4)

• Change the amplitude and frequency of the
  input-signal back to the original value.
• Change the LO1 frequency according to the low-LO
  principle.
• Estimate the frequency of the base-band signal on
  the oscilloscope.
• Increase the frequency of the input signal one
  kHz. Re-estimate the frequency of the base-band
  signal on the oscilloscope. Explain the result.

8
Tasks with the equipment 4(4)

• Use the available to convert the module to a TX
  module, according to Section 1.2 of
  IR-S3-SB-0316.
• Use a tone-generator to generate a signal of 0.5v
  amplitude and 10kHz frequency (check with
  oscilloscope), connect it to a transmitter
  resistive matching box (Figure 9 of
  IR-S3-SB-0316).
• Use a low-lo setting for LO2.
• Measure the spectrum output from the mixer 24
  using the span 69.970MHz to 70.010MHz with
  resolution bandwidth 1kHz. Explain.
• Measure the spectrum of signal of the I input
  of the mixer 19 using the same settings.
  Explain the difference with the previous
  spectrum.
• Measure the output spectrum with span from 300 to
  500MHz, explain the result.
• Add the NMT450 filter. Measure the spectrum again
  with the same settings as in previous point.
  Explain the result.
• Re-connect the cables back to make the module an
  RX module. Check that it is working properly.
• Document all the spectrums and explanations in a
  report and send to perz_at_s3.kth.se.
• Done!