measurement receivers with quasi-peak...

Measurement receivers with quasi-peak detector

Martin HudličkaCzech metrology institute

[email protected]

Workshop on characterization of pulse generators, 24. 5. 2017, INTA 1

• Introduction• Specifications• Pulse measurements• Conclusion

Contents


Introduction

• quasi-peak (QP) detector originally designed as an indication of a subjective disturbing feeling of listeners of radio broadcasting (sharp pulses in time-domain)

• dependence of the pulse frequency on the listener’s comfort• detector designed in order to imitate this dependence

• today QP detector also used in other frequency bands and for different applications

• useful tool for description of a wideband radio disturbance



Contents


Specifications

• specifications in EN 55016-1-1 ed. 3

band E (1-18 GHz) -> other than QP detectors used

band A B C Dfreq. range {9 - 150} kHz {0.15 - 30} MHz {30 - 300} MHz {300 - 1000} MHz

B -6dB 200 Hz 9 kHz 120 kHz 120 kHzτ charge 45 ms 1 ms 1 ms 1 ms

τ discharge 500 ms 160 ms 550 ms 550 msτ indicator 160 ms 160 ms 100 ms 100 ms

overload factor of circuits preceding

the detector24 dB 30 dB 43.5 dB 43.5 dB

overload factor of the DC amplifier

between detector and indicator

6 dB 12 dB 6 dB 6 dB


Specifications

• EN 55016-1-1 ed. 3 uses term measuring receiver as a general instrument fulfilling the requirements in the above table– selective voltmeter– EMI receiver– spectrum analyzer– FFT-based instrument


Specifications

• in the manufacturer specifications, there should be an information in which frequency range the instrument fulfills EN 550160-1-1 (CISPR 16-1-1)

• the main difference between a measuring receiver and a spectrum analyzer is the presence of pre-selection filters and pre-amplifier (limiting the spectrum of signals entering the receiver, otherwise its input circuits might be overloaded; increase of dynamic range)

• higher frequency bands -> very short pulses with high amplitude, risk of instrument damage

• also instruments without preselection may be used, but in a limited range of pulse repetition rates and with caution


Specifications

• FFT-based receivers – require a skilled operator (sweep-time settings, number of samples for the FFT, frequency resolution)


Specifications

input impedance

• nominal value 50 Ω (unbalanced)• VSWR < 2 (input attenuator 0 dB) or VSWR < 1.2 (input

attenuator 10 dB)• in the band 9 kHz to 30 MHz -> symmetrical measurements

permitted (input transformer needed, incorporated in an external artificial network or in the meas. receiver)

• recommended input impedance in the band 9 kHz -150 kHz is 600 Ω


Specifications

selectivity

• given by masks for bands A/B/C/D• overall selectivity (passband)

– variation with frequency of the amplitude of the input sine-voltage that produces a constant indication on the meas. receiver

• intermediate frequency rejection ratio 40 dB– ratio of the input sine-wave voltage at the IF/tuned frequency that

produces the same indication of the meas. receiver (if more than one IF exists, this requirement shall be met at each IF)

• image frequency rejection ratio 40 dB– ratio of the input sine-wave voltage at the image freq. / tuned freq.

• other spurious responses 40 dB– ratio of the input sine-wave voltage at all other frequencies / tuned freq.


Specifications

selectivity passband. band A


Specifications

selectivity passband. band B


Specifications

selectivity passband. bands C + D


Specifications

intermodulation distortion

• influence of intermodulation effects should be minimized• a method described in CISPR 16-1-1 to determine the

suitability of a measuring instrument


Specifications

sine-wave voltage accuracy

PK = QP = RMS = AV

• meas. receiver with QP detector shall measure the sine-wave with ±2 dB accuracy up to 1 GHz

• unmodulated sine-wave should give equal readings for all detectors for all bandwidths


Specifications

response to pulses (abs. calibration)

PK > QP > RMS > AV

• the response to a signal with defined impulse area and repetition rate, with uniform spectrum should be equal to the response to a sine-wave with 2 mV RMS (= 66 dBμV)

• valid for generators with 50 Ω output impedance working into open circuit

• max. error ±1.5 dB


Specifications

response to pulses (absolute calibration)

band A B C D

freq. range {9 - 150} kHz {0.15 - 30} MHz {30 - 300} MHz {300 - 1000} MHz

impulse area (open-circuit) 13.5 μVs 0.316 μVs 0.044 μVs 0.044 μVs

repetition rate 25 Hz 100 Hz 100 Hz 100 Hz


Specifications

response to pulses (relative calibration)

• the indication varies with the change of the pulse repetition rate in a defined way (the shape of pulses must not change)

repetition rate (Hz)

change of the input level with the change of repetition rate resulting in constant receiver indication (dB)

bandA

{9 - 150} kHzB

{0.15 - 30} MHzC

{30 - 300} MHzD

{300 - 1000} MHz1000 - -4.5 ± 1 -8 ± 1 -8 ± 1100 -4 ± 1 0 (ref) 0 (ref) 0 (ref)60 -3 ± 1 - - -25 0 (ref) - - -20 - 6.5 ± 1 9 ± 1 9 ± 110 4 ± 1 10 ± 1.5 14 ± 1.5 14 ± 1.55 7.5 ± 1 - - -2 13 ± 2 20.5 ± 2 26 ± 2 26 ± 21 17 ± 2 22.5 ± 2 28.5 ± 2 28.5 ± 2

single pulse 19 ± 2 23.5 ± 2 31.5 ± 2 31.5 ± 2


Specifications

response to pulses (relative calibration)

• tabular or graphical representation (see CISPR 16-1-1)

AB

C+DWorkshop on characterization of pulse generators, 24. 5. 2017, INTA 19

Specifications

other specifications

• meas. receiver should be immune against external EM fields and not produce disturbing signals (LO feedthrough, conducted and radiated emissions)

• instrument should contain an IF output and detector output, whereas connecting a load to these outputs should not influence the indication



Contents


Pulse measurements

• typical meas. receiver with QP detector

- in case of PC-based receiver, the mechanical time-constant is replaced by an electronic circuitry


Pulse measurements

• block diagram of an EMI receiver (simplified)


Pulse measurements

• notes to pulse measurements

- the shape of the spectrum envelope depends on the pulse shape in the time-domain


Pulse measurements

• notes to pulse measurements


Pulse measurements

• pulses with equal area produce equal IF output of the receiver


Pulse measurements

• EMI receiver is a band-pass filter


Pulse measurements



References

[1] Rohde & Schwarz: ESVN 40 Test Receiver Operating Manual[2] Rohde & Schwarz: ESPI EMI Test Receiver Service Manual


Thank you for attention

EMPIR project “15RPT01 Development of RF and microwave metrology capability”http://rfmw.cmi.cz/


measurement receivers with quasi-peak...

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