Column Control DTX

Tips for Querying CW and Average Power

애플리케이션 노트

Introduction

This application note applies to the following products from Keysight Technologies

  • N1913/14A EPM power meter
  • E4416/17A EPM-P power meter
  • N1911/12A P-Series power meter
  • U2020 X-Series USB Peak and average power sensor
  • U2000A Series USB average power sensor
  • U8480A USB Thermocouple USB power sensor
  • Keysight power sensors

This application brief demonstrates the capabilities Keysight Technologies, Inc. power meters and power sensors have for measuring CW and average power signals. It also explains the advantages and disadvantages of selecting SCPI commands and settings for Keysight power meters and power sensors, illustrating how to these items to improve power measurement speed without compromising measurement accuracy.

Table of Content

  • Power measurements
  • Querying tips
  • Power sensor measurement speed
  • Test configuration and SCPI commands

Power measurements

There are many ways to analyze a modulated signal. The power-versus-time measurement is a very useful method for examining power level changes due to pulsed or burst carriers.

Average, pulse, and peak envelope power measurements provide different types of information about the signal.

Pulse power is determined by measuring the average power of the pulse and then dividing the result by the pulse duty cycle. This is a mathematical representation of the pulse power rather than an actual measurement and assumes constant pulse power. Pulse power measurement averages out any aberrations in the pulse, such as overshoot or ringing. For this reason, it is called pulse power and not peak power or peak envelope power. To ensure accurate pulse power readings, the modulating signal must be a rectangular pulse with a constant duty cycle. Other pulse shapes such as triangular or Gaussian will cause erroneous results. This technique is not applicable for digital modulation systems, where the duty cycle is not constant, and the pulse amplitude and shape vary.

When the power pulse becomes non-rectangular and the pulse-power measurement equations become inaccurate, using peak envelop power measurements is a better measurement method. This technique is the most suitable for modern digital communication systems with variable duty cycles and pulse widths.

Unlike measuring a pulsed signal that has a pulse repetition period and a constant duty cycle, burst signal measurement is considerably more challenging. Measuring a burst signal with an unpredictable burst length that lacks a constant duty cycle requires time-gated functionality (independent measurement gates). This can be accomplished using high-performance power meters and power sensors.

Keysight power meters and power sensors offer the ability to measure CW and average power. The following example provides some tips for using power meters and power sensors to acquire accurate power without increasing the test time.

Querying tips

Measurement query method

There are three different methods that can be used to query a measurement from the power meter or power sensor. It is beneficial to understand the basic differences between these three commands in order to fully optimize measurement speed.

MEASure?

This command is compound command consisting of ABORt, CONFigure, and READ?. It is the simplest of the query commands because it relies on the power meter to select the best settings for the requested configuration and immediately perform the measurement. One drawback to this command is that its use results in a longer test time and overrides some of the power meter’s settings, such as switching the meter from Free Run to Single Shot mode or changing the average count set to the ON state.

READ?

The READ? command is another compound command that is equivalent to an ABORt followed by an INITiate and FETCH?. The READ? query is similar to MEAS? in that it causes the meter to perform initializations and auto-configuration. However, READ? gives users the flexibility to change certain settings such as the average count. The READ? command allows the user to manipulate the settings in order to optimize the measurement speed, resulting in a shorter test time than that realized using the MEAS? command.

FETCH?

This command retrieves a reading upon measurement completion and puts it in the output buffer. The FETCH? command allows users to manipulate settings such as the average count. However, this command requires additional settling time to complete the average count process, or else FETCH? will return invalid data.

×

판매 문의 부탁드립니다.

선호하는 연락방법을 선택해 주십시오. *필수입력항목
Preferred method of communication? 이메일 변경하기
Preferred method of communication?

체크 박스를 클릭하시면 이메일, 전화 및 문자 광고성 정보 수신동의를 의미합니다. 참고 : 이미 수신 동의를 한 경우 광고성 정보를 계속 받을 수 있으며, 만약 수신 거부를 원하는 경우 https://www.keysight.com/key/privacy에서 신청할 수 있습니다.
[키사이트 개인정보 수집 및 이용]

  1. 개인정보 수집 및 이용 동의
  2. 키사이트 파트너 업무 위탁 동의
  3. 키사이트 해외 본사 및 지사 제공 동의
양식을 작성하여 제출하시면 개인정보 수집 및 이용에 동의한 것으로 간주합니다. 보다 자세한 내용은 개인정보보호정책을 참조하시기 바랍니다.

감사합니다!

A sales representative will contact you soon.

Column Control DTX