1、 Report ITU-R SM.2125-1(06/2011)Parameters of and measurement procedures on H/V/UHF monitoring receiversand stationsSM SeriesSpectrum managementii Rep. ITU-R SM.2125-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-f
2、requency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radio
3、communication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of
4、patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Reports (Al
5、so available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related sa
6、tellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in
7、 English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R SM.2125-1 1 REPORT ITU-R SM.2125-1 P
8、arameters of and measurement procedures on H/V/UHF monitoring receivers and stations (2007-2011) Executive summary This Report describes the measurement procedures to determine the technical parameters of monitoring receivers and monitoring systems. This Report does not describe all possible solutio
9、ns and also not automatically always the best solution for determining a parameter. The Report describes in one section the verification of the key parameters of a monitoring receiver and in another section the verification of the technical parameters of monitoring stations and other integrated syst
10、ems like direction finders. Both sections can show an overlap in contents and even bear the same name. However these items should be treated as different parameters. The reason for splitting the specifications in key parameters and station parameters is the fact that monitoring receivers can be boug
11、ht either as separate devices, or as an integrated system where the separate receiver parameters sometimes cannot be determined. TABLE OF CONTENTS Page 1 Introduction 2 2 Key receiver parameters . 2 2.1 IP2/IP3. 2 2.2 Sensitivity . 3 2.3 Receiver noise figure 3 2.4 IF filter characteristics 4 2.5 Re
12、ceiver scanning speed . 5 2.6 Key parameters for DF receivers 5 3 Monitoring and DF station parameter measurement procedures 6 3.1 Monitoring and DF station IP2/IP3measurement . 6 3.2 Monitoring and DF station sensitivity measurement 8 3.3 Key parameters for DF stations 17 2 Rep. ITU-R SM.2125-1 1 I
13、ntroduction The ITU Handbook on Spectrum Monitoring (Edition 2011) contains typical specifications of monitoring receivers and direction-finder (DF)/monitoring stations but does not specify the measurement procedures to determine these specifications. The Handbook also does not take into account the
14、 specifications of complex systems like a complete monitoring/DF station built around the monitoring receiver. NOTE 1 The ITU Handbook on Spectrum Monitoring is not to set a standard but to try to give guidance on all aspects of spectrum monitoring. The present Report states the relevant key receive
15、r parameters and the station parameters. The discussed parameters can be determined either by the manufacturer or by the end user. 2 Key receiver parameters 2.1 IP2/IP3Monitoring receivers operate in an environment where strong and weak signals are present at the same time. An important property of
16、a receiver therefore is its capability to handle those signals at the same time without distortion. This property is referred to as the linearity of the receiver and a way to quantify this linearity is by the IP2and IP3values. Although the front-end of the receiver contributes most to the IP2and IP3
17、the IF amplifier filters in the case of a digital monitoring receiver and any other amplifiers influence the IP2and IP3. All these components therefore should be taken into account when an IP2and IP3measurement is performed. IP2and IP3measurements are performed by injecting two signals in the receiv
18、er input and measuring the response of the receiver. In the case of non-linearity, products of the two injected signals are generated, and the level of these products is a measure for the non-linearity of the receiver. Besides the linearity of the receiver component itself, the measured IP2and IP3va
19、lues also depend on the following parameters: the difference in frequency and level between the two test signals applied; the selected test frequencies. 2.1.1 Principle of second order intermodulation product calculation Two test signals of the same r.m.s. power (Pin) at frequencies f1and f2(f1 f2)
20、are inserted into the antenna input of the monitoring receiver. Due to non-linearities, two intermodulation products at frequencies f3and f4may appear: f3= f2 f1and f4= f2+ f1These frequencies can also be written using the f parameter (frequency difference). f depends on the type of measurement: f1=
21、 f3+ f and f2= 2 f3+ f, with f = 2 f1 f2The input second order intermodulation product shall then be calculated: IP2= Pin + a Rep. ITU-R SM.2125-1 3 with: IP2: second order intermodulation product at the input to the monitoring receiver under test Pin: r.m.s. power (dBm) of the two inserted test sig
22、nals a: difference (dB) between the level of the test signals and the level of the highest intermodulation product at the input. 2.1.2 Principle of third order intermodulation product calculation Two test signals of the same r.m.s. power (Pin) at frequencies F1and F2(F1 F2) are inserted into the ant
23、enna input of the monitoring receiver. Due to non-linearities, two intermodulation products at frequencies F3and F4may appear: f3= (2 f1) f2 and f4= (2 f2) f1. These frequencies can also be written using the f parameter (frequency difference), f depends on the type of measurement f1= f3+ f and f2= f
24、3+ 2 f, with f = f2 f1The third order intermodulation products shall then be calculated: IP3= Pin + a/2 with: IP3: third order intermodulation product at the input to the monitoring receiver under test Pin: r.m.s. power (dBm) of the two inserted test signals a: difference (dB) between the level of t
25、he inserted test signals and the level of the highest intermodulation products at the input. 2.2 Sensitivity The sensitivity of a spectrum monitoring receiver is defined as the minimum signal voltage (V) at the input of the monitoring receiver that allows demodulation and audible listening of the re
26、ceived signal. The minimum audible signal level can be determined using a signal-to-interference ratio including noise and distortion (SINAD) measurement. 2.3 Receiver noise figure The noise figure is one of the main specifications of a monitoring receiver. The noise figure is closely tied to the se
27、nsitivity of the monitoring receiver. The noise figure of a monitoring receiver is the factor by which the noise power delivered by the monitoring receiver increases when a reference noise is applied to it; the noise figure is measured on the input of the monitoring receiver. The noise figure of a m
28、onitoring receiver can be measured by several methods: gain method; “Y-factor” method (noise diode method); sensitivity method. 4 Rep. ITU-R SM.2125-1 2.4 IF filter characteristics For most monitoring and measurement applications both the shape, the bandwidth and the quality of the various IF filter
29、s are important. Basically four parameters are used to describe the IF filter characteristics. 2.4.1 IF bandwidth This is the bandwidth specified as the distance between the 3 dB and 6 dB points of the IF filter of the receiver. 2.4.2 IF filter passband ripple and asymmetry The way ripple in the pas
30、sband is specified depends on the manufacturer. Mainly there are two ways, and each has its advantage for either digital or analogue filtering. For analogue filters the peak-to-peak value is used because no notches are present and the distribution of ripples is not uniform. For digital filters a pea
31、k-to-average value is used because of the notches present and the uniform distribution of ripples (see Fig. 1). FIGURE 1 Examples of filter passband ripple Rap 2125-01Example of ripple of digital filter Example of ripple of analogue filter2.4.3 IF filter passband curve and out-of-band suppression Ou
32、t-of-band suppression is the suppression of signals far from the edges of the filter specified on a certain distance from the centre of the filter. Dependent on the construction of the filter but also on its mounting and termination, different values can be found for various receivers offered. This
33、parameter is especially important for receivers with digital filters where out-of-band suppression is dependent on the used A-D converters. This suppression can be dependent on the actual measurement distance from the centre frequency of the filter because of anomalies caused by improper termination
34、 of the filter. 2.4.4 IF filter shape factor The shape factor is defined as the ratio between the n dB bandwidth and the 6 dB bandwidth. The factor n has to be specified, e.g. n = 60 dB or n = 50 dB. It should be specified for each filter (see Fig. 2). 2.4.5 IF filter group delay Group delay is the
35、mutual difference in time it takes for a number of signals to travel through the IF filter of a receiver. In an ideal filter all signals applied at different frequency positions inside the IF filter travel with the same delay, so the phase difference between the signals at the input is the same as t
36、he phase difference between the signals at the output of the filter. Group delay can also be called phase linearity of the filter. Rep. ITU-R SM.2125-1 5 FIGURE 2 Some IF filter parameters Rap 2125-02Bandwidth3 levels of out of band suppressionPassbandrippleAnomalies caused by improper termination o
37、f the filterA high group delay exhibits itself mainly near the edges of the passband of the filter, but in high order filters is also prominent inside the passband. As a rule of thumb, we can say that narrow filters and filters with a low shape factor (steep filter edges) have a higher group delay y
38、ielding lower performance. In this aspect there is basically no difference between digital and analogue filters. What does this mean for the user of a monitoring receiver? These wideband steep-edged filters are used in receivers for demodulating digital signals and particularly phase demodulators su
39、ffer in performance if filter group delay is too high. Also aural monitoring can be a tiring exercise if the group delay of the filter is very high. The signals sound distorted and noisy. In a general-purpose monitoring receiver filter group delay should be within certain limits for each IF filter.
40、A way to measure filter group delay is to use a network analyser and sweep through the passband of the filter, and record the changes in phase/frequency behaviour. Group delay is expressed in time (microseconds, nanoseconds). 2.5 Receiver scanning speed Scanning speed (sometimes called sweep speed)
41、is a measure of how quickly a receiver can provide signal level values on a number of frequencies within a given frequency band. It is measured in MHz per second. Scanning speed shall include the effect of any band switching time, end-of-sweep retrace time, local oscillator settling time and any com
42、putation time. In other words, the scanning speed parameter can be used to compute the revisit period. Optionally, the individual elements that affect scanning speed can be listed separately, so users can determine the revisit time for any arbitrary frequency range. 2.6 Key parameters for DF receive
43、rs Depending on the parameters to be measured, the DF receiver shall be considered as a monitoring receiver or a DF station reception chain, and the corresponding parameters measurement shall apply. 6 Rep. ITU-R SM.2125-1 3 Monitoring and DF station parameter measurement procedures The typical block
44、 diagram of a spectrum-monitoring station (as well as a direction-finding station) is given in Fig. 3. Several measurements points can be defined to characterize the antenna (P1), the reception chain (P2) or the receiver (P3). FIGURE 3 Block diagram of an H/V/UHF monitoring/direction finding station
45、 Rap 2125-03P2 = Reception chain m easurementP1 = Antenna measurementD.F.MeasurementAntenna(active/passive)AntennaswitchReceiver ProcessingP3 = Receiver measurementThe antenna is generally made up of a number of elementary antennas (dipoles or other). These elementary antennas can contain switchable
46、 amplifiers, adaptation cells, etc. These components shall be integral parts of the antenna if they are associated with a single elementary antenna. On the other hand, the antenna switches used to select several elementary antennas (direction-finding or monitoring) shall not be considered as an inte
47、gral parts of the antenna but as the reception chain antenna switch. Similarly, amplifiers, filters common to several elementary antennas, as well as frequency change or transposition components shall not be considered as part of the antenna, but as part of the receiving chain. This section describe
48、s the antenna (P1) and receiving chain (P2) measurements; monitoring receiver (P3) measurements are described in 2. The cables implementing the station (and the reception chain) shall be representative of an operational station: for a mobile station, the cables used for the tests shall be 10 m; for
49、a fixed station, the cables used for the tests shall be 20 m. 3.1 Monitoring and DF station IP2/IP3measurement Intermodulation measurements are dependent on the conditions in which they are made. So that end customers can compare monitoring receivers and spectrum monitoring and DF stations performances it is therefore important to specify the procedures for measuring second order (IP2) and third order (IP3) intermodulation products. Second and third order intermodulation products are generated at all the levels of a spectrum-moni
