1、 Rep. ITU-R BT.2138 1 REPORT ITU-R BT.2138 Radiation pattern characteristics of UHF*television receiving antennas (2008) 1 Introduction This Report describes measurements of the radiation pattern characteristics of UHF television receiving antennas. The measurements were made to determine the perfor
2、mance of twelve UHF antennas used for TV reception. Though all antennas tested were designed for multiband operation, the antennas tested covered, inter alia, the frequency range of TV channels 40 to 60 for 8 MHz channel plans and TV channels 41 to 65 for 7 MHz plans. These frequency ranges are exte
3、nsively used for terrestrial television broadcasting services by most ITU administrations. 2 Background Many administrations currently operate digital and/or analogue broadcasting services in the UHF band. Recommendation ITU-R BT.419-3 contains a mask for receiving antenna directivity to be used in
4、the planning of terrestrial television services. This does not constitute a design specification for receiving antennas, but is an assumption about their directivity which affects the calculation of potential interference from other services into the broadcasting service. As part of its work in the
5、study period 2003-2007 in ITU-R, Australia provided representative data for the off-axis performance of UHF receiving antennas (in the elevation plane), noting that the performance may vary with the polarization of the receiving antenna. The results are in Annex 1. Within this study it is clear that
6、 a number of antennas fit well within the Recommendation ITU-R BT.419 mask, while others do not due to their broader patterns and lower gain. This is particularly evident at the lower frequencies. 3 Factors for consideration 3.1 Existing antenna population Statistics from antenna manufacturers indic
7、ate that the antenna types tested in this study represent a high percentage of antenna used in one administration. If these figures were extrapolated for a 10-year period (the estimated notional usable lifetime of a TV antenna) then, given the general commonality of TV antenna designs around the wor
8、ld, the characteristics found in Annex 1 may represent performance characteristics that are also valid for other administrations. * The terrestrial television broadcasting service is found in the UHF frequency range of 470 to 890 MHz (refer Article 5 of the Radio Regulations). Performance of the tel
9、evision receiving antennas in upper portion of the UHF band was the subject under study. 2 Rep. ITU-R BT.2138 3.2 Impulsive noise This Report states in Annex 1 that “a certain AUT (antenna under test) was susceptible to noise generated by the measurement rotator during a swept frequency measurement
10、using a broadband detector. Turning off the motor eliminated the noise so all further swept frequency measurements were conducted when the measurement rotator was turned off”. Impulse noise immunity is an important consideration for receiver performance and reception signal quality for both analogue
11、 and particularly for digital television reception. Interference being received via the antenna may consume level and quality margins. Impulse noise rejection is, amongst other things, dependent upon correct cable terminations and matching cables to the antenna. Annex 1 1 Antennas measured The anten
12、nas measured are listed in Table 1: TABLE 1 Antennas measured Antenna number Antenna design Antenna description Band Mounting location Feed connection 1 Yagi 9 elements IV/V Centre Saddle 2 Yagi 12 elements IV/V Centre F connector 3 Phased array 4 elements IV/V Rear Saddle 4 Phased array 4 elements
13、IV/V Rear Saddle 5 Yagi 18 elements IV/V Rear F connector 6 Yagi 20 elements IV/V Centre F connector 7 Combination UHF 8 elements VHF 4 elements I/II/III/IV/V Centre F connector 8 Combination UHF 10 elements VHF 4 elements IV/V(1)Centre F connector 9 Combination UHF 18 elements VHF 8 elements III/IV
14、/V Centre F connector 10 Combination UHF 10 elements VHF 6 elements III/IV/V Centre F connector 11 Cross-polarized UHF 10 elements VHF 6 elements I/II/III/IV/V(2)Centre Saddle 12 Cross-polarized UHF 10 elements VHF 6 elements I/II/III/IV/V(3)Centre F connector (1)Tuneable UHF frequency range of 526-
15、750 MHz. (2)Tuneable UHF frequency range of 526-750 MHz. (3)Tuneable UHF frequency range of 526-750 MHz. Rep. ITU-R BT.2138 3 2 Measurements undertaken For all antennas listed above the following system parameters were measured: 360 radiation patterns in the azimuth plane at two frequencies, 620 MHz
16、 and 790 MHz within the tunable UHF frequency range. Four radiation pattern cuts at = 0, 45, 90 and 135 were measured at each frequency. Gain-normalized1swept-frequency measurements over the range of 620 MHz to 790 MHz within the tunable UHF frequency range. 3 Measurement description The radiation p
17、atterns were measured on the CSIRO 40 metre outdoor antenna test range in Sydney, Australia, using an Agilent E4407B spectrum analyser as the receiver. The measurement system was set up with a standard gain horn (SGH) as the transmit horn allowing the gain of the antenna-under-test (AUT) to be calcu
18、lated. A linear-polarized WR1150 rectangular pyramidal horn, with a nominal gain of 16.4 dBi, was used for the SGH. Two 6 m RG6 quad-shield 75 cables were used to connect the AUTs to the measurement system. For the AUTs with an F-type balun input a cable with connectors at both ends was used. For th
19、e AUTs with saddle-type balun input a modified cable with one connector removed was used. These cables were then connected to a minimum loss pad used to match impedances between the 75 AUT and the measurement 50 system. The measurement procedure, listed below, was identical for each AUT at both meas
20、urement frequencies. Step 1: The SGH and the AUT were mounted to provide a vertical E-field vector (i.e. an H-plane cut) and the corresponding orientation nominated as 0. Figure 1 shows the orientation of the E-field vector of the AUT and the SGH at each of the four nominated polarizations. Step 2:
21、With both the SGH and AUT mounted 6 m above ground, a quiet-zone test was performed to establish the range length that introduced the minimum ripple from reflections. A range length of 12 m was the quietest distance that satisfied the far-field distance requirement for both the AUT and SGH. The quie
22、t-zone test was done for E vector vertical only at both the upper and lower frequencies for all AUTs. Step 3: The AUT was scanned in azimuth through 360 to obtain a co-polar pattern with samples recorded every 1. 1The antenna gain is obtained through a series of measurements and Friis free-space equ
23、ation. As such the antenna gain has been normalized to the gain of the SGH and is distinct from a direct gain measurement. 4 Rep. ITU-R BT.2138 Step 4: Both the AUT and SGH were then rotated to the next orientation angle. Step 5: The AUT was again scanned in azimuth through 360 to obtain a co-polar
24、pattern with samples recorded every 1. Step 6: Steps 4 and 5 were repeated for the remaining orientation angles. The gain-normalized swept-frequency measurements of the antennas were measured on boresight at 0 orientation for frequencies between 620 MHz and 790 MHz. The measurements were conducted w
25、ith a HP 8757D scalar network analyser and confirmed by measurements at discreet frequencies with an Agilent E4407B spectrum analyser. Two 1.5 m RG6 quad shield cables were used in the measurements; one with F type connectors for connection to antennas with F type balun inputs, and another with no c
26、onnector on one end for connection to antennas with saddle type balun inputs. Both cables were measured with a HP 8510C vector network analyser as well as a minimum loss pad that was used to match impedances between the 75 AUT to the 50 system. The measurement procedure listed below was followed for
27、 each antenna tested. The SGH was modelled with mode-matching software to accurately predict its gain. The range length was set to 12 m and the AUT and the SGH were mounted in the vertical plane (H-plane) nominated as 0 orientation. A HP 8757D scalar network analyser was set up to sweep 620-790 MHz
28、with the detector calibrated for absolute power measurement. The transmit power into the SGH was measured, via a 20 dB directional coupler, and the data saved to file. The received power at the AUT was measured at the output of the 75 to 50 minimum loss pad was measured and the data saved to file. O
29、wing to the risk of other signals being picked up by the wide band detector used on the scalar network analyser, an Agilent E4407B spectrum analyser was used to confirm the measured power levels at several discrete frequencies in the swept band. At each frequency the corrected gain was calculated fr
30、om the ratio of transmitted and received powers after taking into account the losses in the measurement system (i.e. coupling factors, path loss, and the minimum loss pad) and the gain of the SGH. Care is taken with the measurement of each parameter to ensure that errors are minimized, but neverthel
31、ess, uncertainties remain. A number of factors contribute to the level of uncertainty in the measurements. These include errors in the measurement accuracy of the spectrum and scalar analysers, and the impact of range reflections on the measured levels. The estimated on-axis gain accuracy for these
32、measurements is 1 dB. At different azimuth angles the accuracy in the level of the measured pattern may degrade due reflected signals; and will vary differently depending on frequency and polarization of the measured signal. Finally, the antennas with a centre mounting location required a small offs
33、et bracket to facilitate 135 of rotation, this bracket is shown in Fig. 2 along with a general overview of the measurement range shown in Figs. 3 and 4. Rep. ITU-R BT.2138 5 6 Rep. ITU-R BT.2138 4 Results Table 2 summarizes the gain normalized measurements, and lists the plots for the pattern cuts a
34、nd swept responses. The discrete points on the swept response plots refer to the narrow-band spectrum analyser measurements used to confirm the gain. Rep. ITU-R BT.2138 7 TABLE 2 Antenna measurement results Antenna number Polarization (degrees) Frequency (MHz) Gain (dBi) Plot number 0, 45, 90, 135 6
35、20 7.1 1 0, 45, 90, 135 790 11.4 2 1 0 620-790 25 0, 45, 90, 135 620 9.2 3 0, 45, 90, 135 790 9.2 4 2 0 620-790 26 0, 45, 90, 135 620 10.2 5 0, 45, 90, 135 790 13.8 6 3 0 620-790 27 0, 45, 90, 135 620 13.4 7 0, 45, 90, 135 790 15.0 8 4 620-790 28 0, 45, 90, 135 620 11.1 9 0, 45, 90, 135 790 12.0 10
36、5 620-790 29 0, 45, 90, 135 620 11.3 11 0, 45, 90, 135 790 12.5 12 6 620-790 30 0, 45, 90, 135 620 8.6 13 0, 45, 90, 135 790 8.6 14 7 620-790 31 0, 45, 90, 135 620 7.9 15 0, 45, 90, 135 757 0.8 16 8(1)620-790 620-790 32 0, 45, 90, 135 620 9.7 17 0, 45, 90, 135 790 5.9 18 9 620-790 620-790 33 0, 45,
37、90, 135 620 8.4 19 0, 45, 90, 135 790 8.0 20 10 620-790 620-790 34 0, 45, 90, 135 620 7.1 21 0, 45, 90, 135 687 7.0 22 11(2)620-790 620-790 35 0, 45, 90, 135 620 9.5 23 0, 45, 90, 135 687 5.0 24 12(3)620-790 620-790 36 (1)Tuneable UHF frequency range of 526-750 MHz. (2)Tuneable UHF frequency range o
38、f 526-750 MHz. (3)Tuneable UHF frequency range of 526-750 MHz. 8 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 9 10 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 11 12 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 13 14 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 15 16 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 17 18 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 19 20 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 21 22 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 23 24 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 25 26 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 27 28 Rep. ITU-R BT.2138 Rep. ITU-R BT.2138 29 30 Rep. ITU-R BT.2138
