electromagnetic compatibility tests of atcrbs… · electromagnetic compatibility ......

Electromagnetic Compatibility Tests of ATCRBS/TCAS/MODE S to CardionTM Distance Measuring Equipment Beacon

Wayne Bell

Edw~rd Lind

February 1987

DOT /FAA/CT-TN86/60

Document is on file at the Technical Center Library, Atlantic City Airport, N.J. 08405

u.s. Department ot TransportatiOn

Federal Aviation Adn*Wstratlon

Technical Center Atlantic City International Airport, N.J. 08405

NOTICE

This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for the contents or use thereof.

The United States Government does not endorse products or manufacturers. Trade or manufacturer's names appear herein solely because they are considered essential to the object of this report.

1. Report No. 2. GoYornmont Accossoon No.

DOT/FAA/CT-TN86/60

... Title ond Subtitle

ELECTROMAGNETIC COMPATIBILITY TESTS OF ATCRBS/TCAS/MODE S TO CARDION• DME BEACON

Technical Report Documentation Page

3. Recipient" a Cotalo9 No.

5. Report Oato

February 1987 6. Porfonoune Oreonizotion Code

h~--"'!""':"---------------------------i I. Porfo,...ine Oreonizotion Report No. 7. Author' sl

Wayne E. Bell and Edward N. Lind 9. Porfo,...ine Oreonizatian N-• ond Adclrou

Federal Aviation Administration Technical Center Atlantic City International Airport, New Jersey 08405

~-----------------------------~-----------------~ 12. S~t-sorine Aeo,.cy N-• ond Addrou

U.S. Department of Transportation Federal Aviation Administration Technical Center Atlantic City International Airport. New Jersev 08405

DOT/FAA/CT-TN86/60

10. Work Unit No. CTRAIS)

11. Contract or Gront No.

Fl8-04B 13. Typo of Ro~tort oncl Period Covorod

Technical Note

1... ._sorin9 Avoncy Coclo

'The purpose of these tests was to investigate and collect sufficient data to aid the Federal Aviation Administration (FAA) in determining whether the existing tactical air navigation (TACAN)/distance measuring equipment (DME) guardbands are adequate to protect the Cardion• DME 9783 from Air Traffic Contr·ol Radar Beacon System (ATCRBS)/Traffic Alert and Collision Avoidance System (TCAS)/Mode S interference. Tests were conducted at the National Airspace System (NAS) Spectrum Engineering Support Electromagnetic Compatibility Laboratory located at the FAA Technical Center. The tests were designed to measure the ability of the Card ion DME receiver to maintain a 70-percent reply efficiency for a desired signal loading in the presence of varying ATCRBS, TCAS, and/or Mode S interrogation rates.

Test results with the TCAS/Mode S at 1030 megahertz (MHz) and the DME tuned to channel 8X (receive, 1032 MHz) indicated that (1) reply efficiency decreased approximately 8 percent with a traffic loading of 2, 700 pulse pairs per second and radio frequency level below echo trigger threshold level combined with the TCAS/Mode S waveforms, and (2) a maximum change of reply efficiency of 7 percent with DME operating in normal mode and with TCAS/Mode S waveforms. The maximum change in signal level required to maintain a 70-percent reply efficiency was approximately 1 decibel from the no-load condition.

Test results with the DME tuned to channel 62 (receive, ATCRBS/Mode S at 1090 MHz indicated a maximum increase in DME approximately 6 decibels was required to maintain a 70-percent

17. Kay Words

1086 MHz) and the signal level of

reply efficiency.

Air Traffic Control Radar Beacon System (ATCRBS) Distance Measuring Equipment (DME) Hode S

Document is on file at the Technical Center Library, Atlantic City International Airport, New Jersey 08405

Traffic Alert and Collision Avoidance Syste~ (TCAS) 19. Security Clauil. (of this report) 20. Security Clouif. (of thia paeo) 21. No. af Paves 22. Proco

Unclassified Unclassified 30

Form DOT F 1700.7 IB-721 Reproduction of complotocl pa9o authorized

EXECUTIVE SUMMARY

INTRODUCTION

Purpose Background Equipment Description Mode S

TABLE OF CONTENTS

Traffic Alert and Collision Avoidance System Mode S and ATCRBS Fruit Generator TACAN/DME Beacon Simulator

TEST DESIGN

Approach Test Procedures

TEST RESULTS

TCAS/Mode S (1030 MHz) Interference Test Results ATCRBS/Mode S (1090 MHz) Interference Test Results

CONCLUSIONS

iii

Page

vii

1

1 1 1 3 3 3 4

4

4 5

7

7 8

9

LIST OF ILLUSTRATIONS

Figure Page

1 DME System Block Diagram 11

2 Simplified Block Diagram of Mode S/TCAS Fruit 12 Generator (1030 MH.z)

3 Simplified Block Diagram of ATCRBS and Mode S 13 Fruit Generators (1090 MH.z)

4 Mode S Fruit, Frequency Spectrum 14

5 ATCRBS Fruit, Frequency Spectrum 14

6 Reply Efficiency vs. Signal Level, Channel 8X (3 sheets) 15

7 Reply Efficiency vs. Signa 1 Level, Comparison of 18 Channels 8X and 8Y

8 Reply Efficiency vs. Signal Level, Comparison of 19 Channels lOX and lOY

9 Reply Efficiency v~. Signal Level, Comparison of 20 Channels 17X and l7Y

10 Reply Efficiency vs. Signal Level, Channel 62X 21



13 Reply Efficiency vs. Signal Level, Channel 59 X 22

14 Reply Efficiency vs. Signal Level, Channel sax 23


16 Reply Efficiency vs. Signal Level, Channel 56 X 24

17 Reply Efficiency vs. Signal Level, Channel 5SX 24

v

Table

1

2

3

4

LIST OF TABLES

Channel Assignment for TACAN/DME Frequencies

Tablulation of Fruit Rate Combinations for 1030-MHz Effects Tests

Tabulations of Fruit Rate Combinations for 1090-MHz Effects

Indicated Signal Level Required for a 70-Percent Reply Efficiency Reading

vi

Page

2

6

7

9

EXECUTIVE SUMMARY

The Federal Aviation Administration (FAA) plans to deploy the Mode S System as a replacement for the present Air Traffic Control Radar Beacon System (ATCRBS). The FAA is also developing a prototype of the Traffic Alert and Collis ion Avoidance System (TCAS). The Mode S frequencies will be the same as the present ATCRBS; i.e., 1030 megahertz (MHz) uplink and 1090 MHz downlink. The TCAS frequencies are 1030 MHz transmit and 1090 MHz receive. The FAA previously investigated the effects of ATCRBS/TCAS/Mode S waveforms on tactical air navigation (TACAN)/distance measuring equipment (DME) beacons and interrogations. The Cardionm DME Model 9783 was investigated in this study to determine if the existing guardbands are adequate to protect it from ATCRBS/TCAS/Mode S transmissions. The Cardion DME 9783 is currently being used at some FAA very high frequency omnidirectional radio range (VOR)/DME facilities.

vii

INTRODUCTION

PURPOSE.

The purpose of the electromagnetic compatibility testing was to investigate and collect data which would aid the Federal Aviation Administration (FAA) ~n determining whether the existing guardbands for the Card ion"' distance measuring equipment (DME) 9783 are adequate to protect the beacons from Air Traffic Control Radar Beacon System (ATCRBS)/Traffic Alert and Collision Avoidance System (TCAS)/ Mode S transmissions and, if not, to provide the FAA with sufficient data to establish new guardband requirements.

BACKGROUND.

The FAA plans to deploy the Mode S system as a replacement for the present ATCRBS. The FAA is developing a prototype and encouraging implementation of TCAS. The Mode S frequencies will be the same as the present ATCRBS and TCAS; i.e., 1030 megahertz (MH.z) uplink and 1090 MHz downlink. The TCAS frequencies are also 1030 MHz transmit and 1090 MHz receive.

The National Airspace System (NAS) also provides a ground-based beacon for aircraft navigation referred to as tactical air navigation (TACAN) and DME. The TACAN system provides both magnetic bearing and slant distance range between beacon and aircraft when interrogated by TACAN or DME airborne units.

DME systems provide only distance information. The TACAN/DME systems operate on carrier frequencies between 960-1215 MHz, employing a 1-MHz channel separation. The FAA has previously investigated the effects of ATCRBS/TCAS/Mode S signals on tube-type TACAN/DME beacons and interrogations. The results of those tests are documented in report DOT/FAA/CT-TN83/02 entitled ''Mode S/TCAS to TACAN/DME Uplink Compatibility Tests" and report CT-82-100-80LR entitled ''Mode S/TCAS to TACAN, DME Downlink Compatibility Test."

At the present time, the FAA is in the process of replacing the tube-type TACAN/DME ground equipment (the same type of equipment evaluated in the ATCRBS/TCAS/Mode S to TACAN/DME compatibility tests) with new solid-state equipment referred to as second generation very high frequency omnidirectional radio range (VOR), TACAN type FAA-996, and Card ion• DME, type 9783, equipment. In support of this replacement program, the Spectrum Engineering Division, AES-500, requested validation tests be conducted to ascertain that the guardband requirements established for the tubetype equipment are valid for the new solid-state TACAN/DME equipment. This task was assigned to the FAA Technical Center. Test results utilizing a Cardion DME, model FA 9783, are presented in this report.

EQUIPMENT DESCRIPTION.

A Cardion"' DME, Model FA 9783, was the ground DME system that was subjected to the Mode S/TCAS 1030-MHz and ATCRBS/Mode S 1090-MHz waveforms. The Cardion ~s representative of the state-of-the-art DME equipment presently being used in the NAS by the FAA.

1

All DME systems provide identification and distance information to properly equipped aircraft. Identification information or1g1nates in the transponder beacon, however, the distance information is furnished to aircraft only on demand. Each aircraft must interrogate the ground DME facility by means of the coded interrogation pulse pairs before the transponder beacon can generate and transmit distance information. Figure 1 is a simplified block diagram of a DME system. (Note: Figures have been placed at the end of the report, after the Conclusions.)

The DME system operates on carrier frequencies between 960 and 1215 MHz employing a 1-MHz channel plan. These frequencies are designated on aeronautical charts by channel numbers 1 to 126 (called X channels). In addition, pulse position modulation is used for another 126 channels (Y channels) on the same frequencies but with different pulse spacings. Any given channel, either X or Y, uses two frequencies, one for interrogation and one for reply, separated from each other by exactly 63 MHz. DME channels that are designated X mode use pulse pair spacing of 12 microseconds for both the ground-to-air (G/A) and the air-to-ground (A/G) frequencies. Channels that are designated Y mode use a G/A pulse pair space of 30 microseconds and A/G pulse pair space of 36 microseconds.

TACAN/DME channels 17 to 59 and 70 to 126 are designated for use in the NAS. Most of these channels are used by the FAA to provide air navigation services. TACAN/ DME channels 1 to 16 and 60 to 69 are designated for the military services for tactical use and are not used in the NAS. Table 1 is a channel assignment chart for TACAN/DME frequencies.

TABLE 1. CHANNEL ASSIGNMENT FOR TACAN/DME FREQUENCIES

AIRCRAFT NO. OF FREQUENCY (MHZ) VORTAC/ILS USER CHANNEL FREQUENCIES G/A A/G FREQUENCY (MHZ)

MILITARY lX- 16X 16 962- 977 1025-1040 N/A

lY- 16Y 16 1088-1103 1025-1040 112.35-117.95

CIVIL 17X- 59 X 43 978-1020 1041-1083 108.00-112.20

17Y- 59Y 43 1104-1146 1041-1083 108.05-112.20

60X- 63X 4 1021-1024 1084-1087 N/A

MILITARY 60Y- 63Y 4 1147-1150 1084-1087 N/A

64X- 69X 6 1151-1156 1088-1093 N/A

64Y- 69Y 6 1025-1030 1088-1093 N/A

CIVIL 70X-126X 57 1157-1213 1094-1150 112. 30-11 7 . 90

70Y-126Y 57 1031-1087 1094-1150 112 • 3 5-11 7 . 9 5

2

MODE S.

Mode S ~s a discrete address beacon system (DABS) that provides improved air traffic surveillance data and an integral ground-air-ground digital communications data link. Mode S is fully compatible with the present ATCRBS.

Uplink interrogations are on a frequency of 1030 MHz. The interrogations are two basic types consisting of (1) the present pulse amplitude modulation (PAM) Mode 3 and Mode C ATCRBS waveforms with the addition of a P4 pulse after the normal P3 pulse (ATCRBS/Mode S all-call), and (2) a discrete interrogation consisting of PAM Pl and P2 pulses followed by a data field time duration of 16.25 or 30.25 microseconds. The information in the data field is in the form of differential phase-shift keying (DPSK) modulation at a 4-megabit pulse-per-second data rate. Downlink replies are on a frequency of 1090 MHz. The replies are either the present PAM ATCRBS reply waveforms or the discrete address waveforms. The ATCRBS replies are the normal 12-bit reply field; the Mode S replies consist of a PAM 4-pulse preamble followed by a data field time duration of 56 or 112 microseconds in length. The information in the data field are in the pulse position modulation format at a 1-megabit pulse-per-second data rate.

TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM (TCAS).

TCAS is an airborne collision avoidance system which operates ~n both the ATCRBS and Mode S mode.

This system transmits at 1030 MHz and has the two basic types of interrogations: (1) the present ~AM Mode C ATCRBS waveform with the addition of a P4 pulse after the normal P3 pulse, and (2) a discrete interrogation consisting of PAM Pl and P2 pulses followed by a data field time duration of 16.25 or 30.25 microseconds. The information in the data field is in the form of DPSK modulation at a 4-megabit pulse-per-second data rate.

MODE S AND ATCRBS FRUIT GENERATOR.

The Mode S and ATCRBS fruit generators were developed and fabricated at the FAA Technical Center to provide a simulated fruit environment to be used in the testing of ATCRBS and Mode S processors. Figure 2 is a simplified block diagram of the Mode S/TCAS fruit generator (1030 MHz). Simulator A generates omnidirectional TCAS interrogations from 55 aircraft while simulator B generates those of 28 aircraft. Simulator B also provides interrogations that represent 40 percent of maximum interrogation rates as found in the Mode S national standard. Simulator C is identical in capability to Mode S sensor portion of simulator B and generates 60 percent of the Mode S national standard. Figure 3 is a simplified block diagram of the ATCRBS and Mode S fruit generators (1090 MHz). Figures 4 and 5 show the relative amplitudes of radio frequency (RF) energy contained in the sidebands of the Mode S and ATCRBS fruit sources.

Each of the four ATCRBS fruit generators is capable of generating nominal fruit rates up to 20,000 replies per second for a combined total of 80,000 fruit replies per second. The t~m~ng control provides additional pseudo-random t~m~ng

distribution about the nominal fruit rate. The nominal fruit rate is selectable in

3

increments to 20 fruit replies per second v~a keyboard entry. The amplitude distribution of the generated fruit is "burned" into a programable read only memory (PROM) and cannot be readily modified without generating a new PROM with different parameters. The amplitude distribution is stored in 256 values in the PROM which is addressed by a pseudo-random number generator. The selected value for each fruit reply is then used to control an attenuator to establish the appropriate level for that reply. The total range of possible fruit reply amplitudes is 32 decibels (dB).

Four code generators are used to generate the total fruit output with each supplying one-fourth of the total. Three of the code generators can each produce four different altitude codes (the fourth code generator duplicates the altitude codes of one of the other generators) for a total of 12 different altitude values.

The four sets of altitude code data for each generator are stored in PROM's and are selected sequentially when generating fruit. Alternately, speci fie altitude codes can be selected via a keyboard entry.

The Mode S fruit generator is capable of generating Mode S fruit rates up to 2,000 replies per second with the rate selectable in increments of four fruit replies per second via keyboard entry. The fruit generator contains two independent fruit control and reply generator units, each of which contributes up to one-half of the total fruit output. These tests use only the Mode S reply generator whose output amplitude is pseudo-randomly varied.

TACAN/DME BEACON SIMULATOR.

A Republic TACAN/DME interrogator simulator was used in these tests as a source of normal DME interrogation loading to the Cardion• DME system. The Republic test set has the capability of generating either X-mode or Y-mode squitter signals with Gaussian-shaped pulse pairs at rates of up to 10,000 pulse pairs per second. The RF frequency of the squitter signals is selectable from 960 to 1215 MHz in 1-MHz increments, and the output amplitude is continuously adjustable between -10 and -110 decibels above 1 milliwatt (dBm).

TEST DESIGN

APPROACH.

The Cardion DME was configured in the NAS Spectrum Engineering Support Laboratory located at the FAA Technical Center and that is where all DME Electromagnetic Compatibility (EMC) testing was accomplished. The first series of tests involved the overall performance tests as specified by the manufacturer of the DME system to assure system operation. Engineering tests were then conducted to determine the effects of ATCRBS/TCAS/Mode S (1030/1090 MHz) waveforms on DME performance.

DME beacon tests were conducted to determine the ability of the beacon receiver to maintain a given reply efficiency for a specified desired signal loading in the presence of various TCAS and/or ATCRBS/Mode S signal parameters; i.e., power levels or interrogation loading to the beacon under test. The TCAS/Mode S (1030 MHz) and ATCRBS/Mode S (1090 MHz) were used as sources of interference. ~oth normal interrogations and interference sources were injected into the beacons at the RF

4

level v~a circulators and directional couplers. The effect on the TCAS/Mode S (1030 MHz) signals on the DME was recorded first, and then the ATCRBS/Mode S (1090 MHz) data were recorded. Before each data run, the frequency of each fruit signal generator was adjusted to the desired frequency (1030 or 1090 MHz) +200 KHz. Then the DME system was checked for normal operation as per FAA standards, Maintenance of TACAN/DME Equipment, Order 7680.3A. When normal DME system operating tolerances could not be achieved, system alignment procedures, as per manufacturer's instruction book, TI 6780.4, DME Ground Station Equipment, were performed. After completing a complete set of interference data, the DME was tuned to the next channel. The fruit source signal generators were adjusted to either 1030 or 1090 MHz during the test program.

The following beacon performance parameters were recorded throughout the tests (reply efficiency is the ratio of the number of valid beacon replies to the number of interrogations expressed in percent):

1. Number of desired interrogations (used to determine beacon reply efficiency).

2. Number of valid replies (used to determine beacon reply efficiency).

3. Number of echo suppression gates.

TEST PROCEDURES.

Initially, the monitor's interrogation signal generator was set at -60 dBm and at 100 interrogations per secon4. An average of ten, 1-second samples of replies to the 100 interrogarions per second was recorded. Then the monitor signal generator level was decreased in 5-dB increments with 100 interrogations per second, with an average of ten, 1-second samples of replies being recorded for each signal generator setting. This information represents the no-load beacon performances.

The next series of measurements were performed to determine DME system performance when operating at various traffic loads. The same monitor signal generator test levels were repeated with the Republic test set adjusted for DME loads of 2, 700 pulse pairs per second and then 5,000 pulse pairs per second. The 2, 700 pulsepairs-per-second load represents a DME operating at approximately a 50-percent load and 5,000 pulse pairs per second is the maximum traffic load.

Another parameter in the DME receiver affecting reply efficiency ~s the long-distance echo circuit. This circuit was called the Retriggerable Blanking Gate (RTBG) in the earlier model TACAN/DME systems. A long-range echo is defined as any echo occurring 60 milliseconds after the valid interrogations. When this type echo problem occurs, it is necessary to generate an extended dead-time gate to cover any long-range echos. The echo suppression gate circuit in the receiver will trigger a suppression gate each time an interrogation exceeds a predetermined threshold level.

Tests were performed with the DME system operating with interrogations that exceeded the echo circuit threshold level (high-level interrogation) and then the same measurements were repeated with an interrogation level below the threshold level (low-level interrogation). The Republic test set was adjusted for DME loads of 2,700 and 5,000 pulse pairs per second at a level above and below echo threshold, and reply efficiency versus monitor signal level data were recorded.

5

Data collected to this point are baseline DME performance information. The final series of measurements were performed to determine DME performance when Mode S/TCAS signals were added to each of the above load conditions. The reply efficiency versus monitor signal level data provide information on the effect of the undesired signals (1030/1090 MHz fruit) on the internal workings of the beacon/receiver and the internal effects of the undesired signals on the desired signals. Test measurements were performed with the DME operating in both X and Y modes with an echo trigger level of -70 dBm, echo suppression gate of 150 milliseconds, dead-time gate of SO milliseconds, and receiver sensitivity of -93.5 dBm. Table 2 tabulates the various combinations of Mode S/TCAS fruit rates used during the tests. Data were collected with the DME tuned to channels 8, 10, and 17X and 8, 10, and 17Y. Plots of the 8X and 8Y data are included as part of this report. Data plots for all Mode S/TCAS ( 1030 MHz) measurements are on file at the FAA Technical Center. After completing the 1030-MHz interference test measurements, the DME was tuned to the closest 1090-MHz receiver frequency. This was channel 62X (1086 MHz). The same procedure/sequence used for the 1030-MH.z interference test measurements was repeated utilizing the 1090-MH.z fruit source. Table 3 is a tabulation of the various combinations of ATCRBS/Mode S fruit rates for the 1090-MHz effects tests. Interference data were collected on channels 55 through 62X.

TABLE 2. TABULATION OF FRUIT RATE COMBINATIONS FOR 1030-MHz EFFECTS TESTS

NO LOAD TCAS MODE-S TCAS/MODE-S

NO LOAD X X X X 2,700 pulse pairs per HIGH X X X X second from test set LOW X X X X 5,000 pulse pairs per HIGH X X X X second from test set LOW X X X X

HIGH - RF level from test set is above echo trigger threshold leve 1.

LOW RF level from test set 1s below echo trigger threshold level.

6

TABLE 3. TABULATION OF FRUIT RATE COMBINATIONS FOR 1090-MHz EFFECTS TESTS

ATCRBS

OFF lK lOK 20K 30K 40K 80K OFF X X

NO LOAD X X X X X X (TEST SET OFF) X X X X X X

X X X X X X H X X

2,700 7 X I X pulse a X X X X X X X pairs per 1 X X X X X X X second a X X X X X X from 1 X X X X X X test set }I X X X X X X

L X X X X X X }I X X X X X X L"" X X X X X X

H X X 5,000 "I:"" X X pulse ~ X X X X X X X pairs per r--t- X X X X X X X second r--w- X X X X X X from ~ X X X X X X test set ~ X X X X X X r-y- X X X X X X

~ X X X X X X r--t- X X X X X X

H - RF level from test set above echo trigger threshold level. L - RF level from test set below echo trigger threshold level.

TEST RESULTS

TCAS/MODE S (1030 MHz) INTERFERENCE TEST RESULTS.

MODE-S

400 750

X X

I I

X

I X

I X X

X X

X X

lK

X

X X

X X

The closest receiver frequency (A/G) to 1030 MH.z that the Cardion"' DME could be tuned to was channel 8X (receiver frequency of 1032 MH.z).

Figure 6 plots the channel 8X data. The plot shows the change in reply efficiency as a function of desired signal level for various test conditions. A dotted line through the 70-percent reply efficiency value is used as a reference to show DME performance.

7

The largest decrease in reply efficiency occurs when the DME traffic load, supplied by the test set, is at an RF leve 1 greater than the echo trigger threshold leve 1. The decrease in reply efficiency caused by DME traffic loading results from the large dead-time created by the long-distance echo suppression circuit (see figure 6, sheet 1). Tests show that a combination of high traffic loads and Mode S/TCAS fruit will result in reply efficiency readings greater than those recorded with only high traffic loads. This result is caused by the echo suppression circuit and is shown in figure 6, sheet 2 and 3.

Maximum change in reply efficiency was recorded when the Mode S/TCAS waveforms were combined with 2, 700 pulse-pairs-per-second load from the test set at an RF level below echo threshold. The maximum change from normal was a reduction of approximately 8 percent in reply efficiency. This is shown in figure 6, sheet 2.

Figures 7, 8, and 9 are plots of the data recorded when the DME was tuned to channels 8, 10, and 17X and 8, 10, and 17Y. The plots show DME performance when operating in a normal mode (no-traffic load) versus operating when Mode S/TCAS signals are applied. Test results show a maximum change in reply efficiency was recorded when the DME was tuned to channels 8X and 8Y (receive frequency 1032 MHz) with the addition of Mode S/TCAS waveforms. This combination resulted in a 7-percent reduction in reply efficiency (see figure 7). The maximum change in signal level required for a 70-percent reply efficiency reading was approximately 1 dB from the no-load condition. This is shown in figure 7, channel 8Y.

ATCRBS/MODE S (1090 MHz) INTERFERENCE TEST RESULTS.

Table 4 contains-- the data collected under various test conditions. Data were collected with the DME receiver frequency and the ATCRBS/Mode S fruit frequency (1090 MHz) separated by 3 to 8 MHz (channels 55 to 62X). The receiver sensitivity reference of the DME in the absence of fruit was -93. 5 dBm. The data listed in table 4 show the signal level required for a 70-percent reply efficiency reading. The 70-percent reply efficiency level is used as a reference for DME system performance. Test results show that when the DME was tuned to channel 62X (receiver frequency 1086 MHz), the signal level required for a 70-percent reply efficiency was -92.6 dBm. A signal level of -86.1 dBm (6.5 dB increase in signal) was required to maintain a 70-percent reply efficiency when the ATCRBS fruit rate was increased to 80,000. Comparing the same data points with the DME tuned to channel 55X (receiver frequency 1079 MHz) resulted in a change of 2. 3 dB in the signal level for a 70-percent reply efficiency reading.

8

RCV'D DME DME

CHANNEL FREQ. X (MHz)

62 1086

61 1085

60 1084

59 1083

58 1082

57 1081

56 1080

55 1079

*No data recorded.

TABLE 4. INDICATED SIGNAL LEVEL REQUIRED FOR A 70-PERCENT REPLY EFFICIENCY READING

SIGNAL LEVEL (-dBm) ATCRBS FRUIT RATE

1 K 10 K 20 K 30 K 40 K

92.6 91.7 90.7 89.0 87.9

91.1 90.7 89.8 * *

92.6 92.6 92.1 91.6 91.3

92.0 91.8 91.6 91.6 91.3

91.7 91.7 91.6 91.5 91.3

92.7 92.6 92.5 92.4 92.2

93.1 92.9 92.9 93.0 92.7

93.1 92.9 92.9 92.6 92.4

80 K

86.1

*

88.6

88.7

90.0

90.3

90.8

90.8

Figures 10 through 17 are plots of the data collected when the DME was tuned to channels 55 through 62X. The plots show the change in reply efficiency as a function of desired signal level for various test conditions. The data shown here were recorded with the Mode S fruit rate held constant at 1,000 replies per second. The test sequence/procedures used for the 1030-MHz interference measurements tests were repeated for these tests. Test data were also recorded with the DME tuned to channels 61 and 62Y. The 61 and 62Y test results were similar to the 61 and 62X test results; therefore, due to time constraints, the Y-mode testing was discontinued. Plots of the 1090-MHz data are on file at the Technical Center. The maximum change in signal level measured at the 70-percent reply efficiency point was 3.5 dB (see figure 10).

CONCLUSIONS

Based on test results contained in this report, it is concluded that:

1. The 1030-MHz Traffic Alert and Collision Avoidance System (TCAS)/Mode S signals have little effect on the Cardion"' distance measuring equipment (DME) reply efficiency measurements.

2. The 1090-MHz Air Traffic Control Radar Beacon System (ATCRBS) /Mode S signals cause a decrease in reply efficiency when the DME is tuned to channel 62X (receiver frequency 1086 MHz) at all fruit rates.

9

3. A 1090-MHz ATCRBS/Mode S fruit rate environment of lk to 80k causes a measurable reduction in DME reply efficiency for all channels measured ( 55-62: 1079-1086 MHz). At high (40-80k) fruit rates, an approximate 6-decibel increase in signal is required to maintain a 70-percent reply efficiency for channel 62.

4. The largest decrease in reply efficiency is caused by DME traffic loading which results in a large dead-time created by the echo suppression circuit.

RECOMMENDATION

In areas where high fruit rates are anticipated, assignments to channel 62 should be avoided.

10

TRANS~ITTER

DELAY

:SO~a

RECEIVER

AN

8T.

1:

1

1 SYSTEM

: TRANSPONDER

OIIINIDIR!CTIONAL ANT£NNA

RECEIVER t------.

TitANS• IIITTER

RANGE CIRCUIT

FIGURE 1. DME SYSTEM BLOCK DIAGRAM

II

r-----..., I a I 1 I I I "IC I

-N

IIUULATOR A

UlliiC -PAll =IIATIOM I TCAS IDPSKDATA ~ II AIRCRAfT AMPU DATA

PIOGRAMIIABII

.. ~., PAM I TCAS INTIUOIAliONS (Rf)

MODULATOR

cw .. ATTINUATOR 1-IIULTI LIVEL. aP SIGNAL

* --SIMULATOR I 'leAl LOGIC IIAIRCUJT MODIIIDI108 ~. NATDIAL

DPSK DATA - UU/ *RF Combiner

STANDARD ..,:.~lOR I 1CAS/UOO~~~ONI (Rf) ...., IHTERR-

PAM INfORMATION IIIIUIUOI DATA

I ~PIIOIRAIIIIAILI t-' ATT!NUATQR I ~TI LIVIL cw~---..., -RJf SIGNAL

SIUULATOI C

11001 S IDISORt-"D-.PS~K-..,;;M;;,;;;:t~•;._ ____ __.

IOOJo NAnOIIAL PAU D*'ORMAnON OPSK/

PAM

-* --

STANDARD AMPUTUDI DATA I ... IIOOULA"RRa I MODE I INTERROGATIONS (Rf)

PROGRAMMABL£ ,._I -•-f_. ATTDfUATOR ~

cw----.a.;li.. 1 ~uLTI LEVEL RF &IGNAl.

FIGURE 2. SIMPLIFIED BLOCK DIAGRAM OF MODE S/TCAS FRUIT GENERATOR (1030 MHz)

10 VICTIM

-

A TCABS FRUIT GEN 1

RF PUl.SI VOL UGI

SOURCE ~ AMfl CONTROL

MOD ATTEN

t t TIMING COD I AMfl

1----GEN CONTROL CONTROL

A TCR8S FAUlT GIN 2

UDINTICAL TO A TCR8S FAUlT GIN 1)

ATCR8S FRUIT GEN 3 "'-"' CIOINTICAL TO ATCAIS FRUIT GIN 1) n "'

COM81NIA u FRUIT A TCA8S FRUIT GIN 4

OUTPUT

UOINTICAL TO A TCR8S FRUIT QEN 1 ) ,.-

MODI S FRUIT GIN 1

"' PUL.SI VO&.TAGI

AMP CONTROL SOURCE MOO ATT!N

t l TIMING RIPI.Y AMP

CONTROl. GIN CONTROl.

MODI S FRUIT GEN 2

RF PUI.S! FIXED AMP

SOURCE MOO ATT!N

_! TIMING REPLY

CONTROL GEN

FIGURE 3. SIMPLIFIED BLOCK DIAGRAM OF ATCRBS AND HODES FRUIT GENERATORS (1090 HHz)

13

hp MI<R lla&&. iii4

-S4.e~

~ ~ I 'I} I i I

~rt I

~, rf I I ! 1---+---+---+---..-·-··r---·-+---1 I I

~-~____.__~l. _ _L_.___I L __ i CENTER lla!iiGI. laG! MM2 ~ J f'l ~~~~"''- SP~N 3GI. !ala MM:

RES SW 3GIGI MMa VSW lla MM2 SWP 21a •••

1075 1078 1081 1084 1087 1090 1093 1096 1099 ll02 llOS ERitiUENCl( ~ /'1HZ ---....-

FIGURE 4. MODE S FRUIT, FREQUENCY SPECTRUM

91al< ~TC~SS F~~s~ / Ge~ ~l - ~4 MI<R 1121S!il.94 MM: -es. '~ .:e ... h p ~EF - 5~. Ia .:e... ~ TTEN Ia .:&

I ,.-

I I I !

I j

I I i

I I I I

4.ll~ I

I I I -~-·~~, I

I I ! -~ . i

i ~J J I ~I 1 ~~~~-r~ ·~ AA .. ,

~\d· '' : I I 1· 111 r . ...,.... '11-....

. I I

I CENTER 1 ~9121. 1211a ,..,...,. I 3M H~'''~· __.

~ES ew 301a "'"'"' vsw 11a "'"'"'

I

I

Si"~N 3~. ~121 ~o<~-tz

$WI=' 2121 •••

1075 1078 1011 1084 1087 1090 1093 1096 1099 ~:c2 ::o: ~INMIIZ---

FIGURE 5. ATCRBS FRUIT, FREQUENCY SPECTRUM

14

CARDION DHE HODEL FAS7a3/3, CHANNEL ax

---NO LORD ------ 2788 LORD tLOWl ---- 2788 LORD tHIGH)

Ill ~--~~~~~~~--------------------------------~

>-u z I.&J .... u .... ~ ~ I.&J

>-..J a. I.&J ~

1-z I.&J u ~ I.&J a.

>-u z I.&J .... u .... ~ ~ I.&J

>-..J a. I.&J IX

.... z I.&J u IX I.&J a.

FIGURE 6.

911

811

711

611

511

411

311

-=~-·~------------------------\ ------\ ----------,,

L' -\ \ ... , ..--------------\-' I \.. _.,..._________ -----· '

- ---------- ------ ~-- ' - ....... _,~ ' ' '

ECHO SUPPRESSION '\ \

' ' \ I

\ I

' ' \ ' ' \ • • \

21 ~~~~--~ .. ~~~~~~~~~~~~--~~~~~~ -u.. -63.51 -s7.. -71.51 -74.3 -77.51 ...... -14.51 ...... -91.58 ~ ... SIGNRL LEV~ <dba)

:CARDION DME HODEL FAS7a3/3, CHANNEL ax

---NO LORD ------ 5111111 LORD tLOWl

IIIII ---- 511118 LORD (HIGH)

911

811

71

611

511

411

311

·---------,,-------r---------, \ ------------- --',- - - - - :.:...-~-~ ........... ~-\ '~ ' '

' ' ' ' ' L' \ L_ \

--~ ' --~------------_._----------------, \ .._ I

CHO SUPPRESSION \ ~

'"'I \ I \ I

\ ~ ' ' ' ' ' 211 ~~~~--~.-~~~~~~~~~~~~ .. ~~~~~~

-61.. -63.51 -67.. -71.51 -74.. -77.51 -11.. -14.51 ...... -91.51 -!5.88 SIGNAL LEVEL (dbal

REPLY EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 8X (Sheet 1 of 3)

15

> u z 1.&.1 -u -Ls.. Ls.. 1.&.1

> ...J a. 1.&.1 ~

.... z

~

CARDION DME MODEL FA97a3/3, CHANNEL ax

---2788 LOAD <LOWl ------ 2700 LOW PULSE MODE S

• • • • • • 2700 LDW PULSE TCAS/MODE S ---- 2788 LOW TCAS 181 ~-------------------------,

98 l 88

78

__ _...... . . . ···4"", .. ~-: . . . . -------- ------=---.="'. ..... ,.--............ -~---------.:...:..:...:..:..... . -- ... --- ······ _f _____ .... _.:_·...:..:.:_i(\ \

- - - 6:p;;ce-;:;-;ed:7tio:I;' J - - - - ~\1 Reply Efficiency \

68 \

58

48

38

28~~~~~~~~~~~~~~~~~~~~~~~~~

-11.. -ll.SI -17.. -71.51 ·74.. -17.51 -11.. -14.51 -11.. -91.51 -15.11 SIGNAL LEVEL (db•>

CARDION D~E MODEL FA97a3/3, CHANNEL ax

---2788 LOAD <HJGHl

Ill ----2781 HIGH TCAS

------ 2788 HIGH MODE S

• · · · · · 2788 HI TCAS/MODE S

98

81

71 ---------r.~-~~-.~~---------~-~-~--------.... _______ .. ·~----J ---68

51

48

31

28 ~~~~ .... ~~~~~~~~~~~~~~ .. ~~~~~· -u.• -13.51 -11.• -71.51 -74.• -77.51 -11.• -14.51 -aa.u -sa.s1 -ss.•

SIGNAL LEVEL <db•>

FIGURE 6. REPLY EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 8X (Sheet 2 of 3)

16

>-u z &AI .... u .... I.A. I.A. &AI

>-_J 11.. &AI Di:

1-z &AI u Di: &AI 11..

>-u z w .... u .... I.A. I.A. &AI

>-_J 11.. w Di:

1-z w u Di: w 11..

CARDION DME MODEL FA97a3/3, CHANNEL ax

---5888 LORD <LOW)

Ill ---- 5111 LOW TCRS

91

Bl

78

&I

58

41

38

------ 5881 LOW ttODE S

· • · · • · 5881 LOW TCRS/ttODE S

21~~~~~~ .. ~~ .. ~~~~~~~~~~ .. ~ .. ~~~ -u.. -63.51 -57.. -71.51 -74.. -77.51 -11.. -84.51 ...... -91.51 -!5.11

SIGNAL LEVEL (dbm)

~ CARDION DHE MODEL FA97a3/3, CHANNEL ax

---5811 LORD CHIQU

Ill---- 5811 HIQt TCRS

------ SBBI HIGH ttODE S

· · · · · • 5888 HI TCRS/MODE S

91

II

71

&I

58 ...

48

38

21~~~~~._ .... ~~~~~~~~~~~ .. ~~~~~~ -61.• -il.sa -67.• -71.51 -74.• -77.51 -11.• -&4.51 -u.• -91.51 -55.88

SIGNAL LEVEL (dbml

FIGURE 6. REPLY EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 8X (Sheet 3 of 3)

17

>-u ~ .... u .... .... .... w >-~ Ill:

~ tt Gl:

~

>-u z w .... u .... I.£. I.£. 1.&.1

>-it w Gl:

1-z 1.&.1 u Gl: w a.

FIGURE 7.

CARDION DHE HODEL fA9783/3: CHANNEL BX

---NO LORD

Ill ----TCRS

------ t10DE S

TCRS/t10DE S

91

II

71

&I

51

41

-------------~~~~r~~~~~~........... ' --------- --,__________ ·_:.:..:... ............ ' ..... ______ ..... 7-Percent Reduction In t

Reply Efficiency

-------------

31~~~~~~~~--~~~~~ .. --~~~~~~~~~ ..... -13.51 -n.• -71.51 -74.. -77.51 ...... -14.51 ..... -91.51 -35 ••

SIGNAL LEVEL Cdbal

CARDION DHE FA 9783/3, CHANNEL BY

---NO LORD

Ill ---- TCRS

II

71

&I

51

48

38

------ MODE S • · · · · · TCRS/ttODE S.

7-Percent Reduction In Reply Efficiency ------1

1-dB Change In Signal Level

21~~~~ .... ~~~~~~~~~~~~~~ .. ~~~~~ -il.. -il.SI -i'l.. -71.51 -74.. -77.51 -11.. -14.51 -11.. -!1.51 -11 ••

SIGNAL LEVEL (db•)

REPLY EFFICIENCY VERSUS SIGNAL LEVEL, COMPARISON OF CHANNELS 8X AND 8Y

18

FIGURE 8.

> u z l£J M u M ..... ..... l£J

> ..J Q.

~ ... z l£J u a: l£J Q.

> u z l£J M u M ..... ..... w > ..J Q. l£J a: ... z w u a: l£J a..

CARDION DME MODEL FA9783/3, CHANNEL 10X

---NO LORD

I B8 ---- TCAS

41

31

------ HOD£ S

· · · · · · TCRS/HODE S

21 ~~~~~ ...... ~~~~~~~~~~~~~~~~~~ ;a.• -n.sa ;1.• -71.51 -7•.• -77.58 -at.• -&4.51 -aa.• -91.51 -ti.lll

SIGNAL LEVEL (db•l

CARDION DME MODEL FA 9783/3, CHANNEL 10Y

---NOL.ORD

I Bl ---- TCAS

91

II

71

&I

51

41

31

------ HOD£ S · · · · · · TCRS/HODE S

21~~~_. ...... --~~~~~~~~----~ ...... ~~~~ -61.. -il.SI -i7.. -71.51 -74.. -77.51 -81.. -84.51 -88.. -91.58 -!5.18

SIGNAL LEVEL (dbal

REPLY EFFICIENCY VERSUS SIGNAL LEVEL, COMPARISON OF CHANNELS lOX AND lOY

19

FIGURE 9.

>u z L.J .... u .... L&. L&. L.J

>-~ L.J a:: .... z L.J u a:: ~

>-u z L.J .... u .... L&. L&. L.J

>-..J Q. L.J a:: .... z L.J u a:: L.J Q.

CARDION DHE HODEL rA9783/3, CHANNEL 17X

--- NOLOAD ------ HODE S

IU;----~-T~~~S~----------·-·-·-··-·~T~~~~H~O~D~E~S~-~

-..._,__~ --~------ ... 91

81

71

61

51

41

31

21~~~~~~~~~~~~~~~~~~~~~~~~~ -u.. ;3.51 ;7.. -11.51 -74.. -17.51 -11.. -14.51 -u.. -91.51 -!15 .• SIGNAL LEVEL (db~l

CARDION DHE HODEL FA9783/3, CHANNEL 17Y

---NO LOAD

IU ----T~. ------ HODE S

T~DES

91 ..,_o:, _____________ - --~~ ••.•...• -~~ ....

'-.....'

81

71

61

51

41

31

I I I I I I I

21~~~~~~~~~~~~~~~~~~~~~~~~~ -u.. ;3.51 ;7.. -71.SI -74.. -17.51 -11.. -14.SI -Ill.. -!11.51 -55 .• SIGNAL LEVEL (db•)

REPLY EFFICIENCY VERSUS SIGNAL LEVEL, COMPARISON OF CHANNELS 17X AND 17Y

20

>u z YJ ..... u ..... u.. u.. YJ

>....1 a.. YJ a:: ..... z YJ u a:: it

>u z YJ ..... u ..... L.. L.. YJ

>....1 a.. YJ a:: 1-z YJ u a:: YJ a..


---NOLOFID ------ NOLORD, ATCRBS 1EII<, HODE 5-lK

· · · · · · NOLOFID, ATCRBS 2EII<, MODE S-1K 1BB ----NOLOAD, ATCRBS lK, HOlE 5-1K

---- -- .. ~ .... ""'o:-',..,..,z:o::::.=r'6:":---------------.. ------~~~~---- ~ .... ---- "\. -- \

9B ~

-- \ ·. \ \ v . \ ' . \ I

711------------~·· ;...\-~

sa ~

68 ~

58 ~

3B ~

• I I 3. 5-dB Change · 1 •

In Signal Level · • I \ ·' ·' ~ J,,\

~ \ " 1

29 I I I I I I I I 1 l .;a.. -63.58 -67.81 -78.58 -74.. -77.51 -81.. -14.51 4.. -91.58 -95 ••

SIGNAL LEVEL Cdbm)

FIGURE 10. REPLY,EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 62X


---NOLOFID

lBS ----RTCRB 1K,MODE 5-lK

------ RTCRB 1SK,HODE S-lK

· · · · · · RTCRB 2BK,MODE S-lK

99 .... . ...• ~~~~--.:~:==:==--:::-------- -• 0 ••••• 0. .......... --...._ --....... ...........__ ...

. ................ ..., 0. ... .........

• " I • ' I

89 -

' . . . ', \ . I

7B ------------ __:_,.\t-\ -.I &

60 1-

59 1-

40 1-

30 ~

20 I I l I I I I

1 \ i l l

I .\:

"'u11 .,J.SI "'7 ·• -7a.sa -74.• -77 .sa -~n.• -t4.58 -aa.u -!lt.sa -!15.11J SIGNAL LEVEL (dbm)

, FIGURE 11. REPLY EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 61X

21

>u z UJ .... u .... I... I... UJ

>....J ~ UJ a:: ..... z UJ u a:: UJ ~

>-u z UJ .... u .... I... I... UJ

>-....J ~ UJ a:: ..... z UJ u a:: UJ ~

CADION DME MODEL FA9783/3, CHANNEL 60X

---NOLOAD ------ NOLOAD, ATCRBS lliiK, HODE 5-lK

· · · · · · NOLOAD, ATCRBS 21i1K, HODE 5-lK lEI!! ---- NOLOAD, ATCRBS lK, HODE 5-lK

:-. 0 ••• ~.,zo....:"L-.:-==-:.-.:~~~------------.... :-- ... --...... 1\. 98 1- . . ........ ----, \ ............. _ \

• 0 ....... __ \

BB 1- .... ·~\ •• 11

78 1--- - - - - - - - - - - - - ..:11-

··.\ ~~ 1 sa 1-

48 1-

38 -

':\ 1 1

28 I I I

:) -68.111 -63.51 .;7.111 -78.58 -74.111 -77.51 -41.111 -44.58 -18.£111 -91.51 ~ ••

SIGNAL LEVEL <dbm)

FIGURE 12. REPLY EFFICIENCY VERSUS SIGNAL LEVEL, CHANNEL 60X


---NOL.OAD

lEI!! ---- NOLORD, RTCRBS lK, HODE 5-lK

------ NOLOAD, ATCRBS lBK, HODE 5-lK · · · · · · NOI..ORD, RTCRBS 2BK, HODE 5-lK

......... -=-.:-,-:-----~ 98 •• 0. ·~----- ...

• 0 •• - ......... \,,

. . . \ ' . ' \

88 . -~\\ )~ ,I

78 ,I .,. ·}

68 \ sa \ 48 \

\ 38

\ 2B ~~~~~~~~~~~~~~~~~~~~~~~~~~ ;&.Ill .;3.58 .;7.111 -78.51 -74.111 -17.58 -11.111 -84.58 -18.111 -91.58 -95 ••

SIGNAL LEVEL (dbm)


22

>u z L&J -u -La.. La.. L&J

>..J a. w IX

1-z L&J u IX w a.

>-u z L&J -u -u.. u.. L.:.J

>-..J a. w IX

1-z w u IX w a.


----NOLORD

tee -----NOL.OAD, ATCRBS lK, MODE S-!K ------ NOLOAD, ATCRBS IBK, MODE 5-IK

· · · · · · NOLOAD, ATCRBS 2BK, MODE S-lK

.. ·-·----· . - ....... -~--... -.-.----,\

I I . ' .. '

~ \

"-'' ·'\ ·' ·~ I 70--------------,-

\ ~ 68 -

58 1-

48 r-

38 1-

28 I J

-68.88 -63.58 -67.88

\ \ \ \ '

I I I I J I I t 1 -78.58 -74.88 -n .sa -11.88 -a4.sa -aa.88 -s1.sa -ss.a

SIGNAL LEVEL (dbm)


CARDION DME MODEL FA9793.'3, CHANNEL 57X

- ---·- NOLOAD ------ NOLOAD, ATCRBS lDK, MODE 5-lK NOLOAD, ATCRBS 2at<, MODE S-1 K

~--.~~· ::-;· ·,;...· ·-=-:.:.:--:.;:-....,-.-...;-.;:;::::: ----·--·----,

----NOLOAD, ATCRBS IK, MODE 5-IK lBB ·-----·------------

98

88

70

6EI

50

4B

3EI

..... c:::---_;~~_.....::::----- I --......... =-=-=-=-=-,..-,~ I -~ .... \.... . . ·~' !

·~\ J ·'' •' j .. - - - - -.- -- -- -- -- -- -- -- ____... ·1 I ·-1, I .• \ I

\I J I

2a ~~~~~~~~~~~~~~~~~~~~~~~~~~ -&B.BB -63.58 -67.88 -78.58 -74.88 -77.58 -81.08 -84.58 -18.11 -91.58 -95.BB

SIGNAL LEVEL Cdbm)


23

>-u z w ..... u ..... I.&.. I.&.. w >-_, a.. w a:: ...... z w u a:: w a..

>u z w ..... u -I.&.. I.&.. w >_, a.. w a:: ...... z w u a:: w a..

CARDION DME MODEL FA9783/3, CHANNEL SGX

---NOLOAD ------ NOLOAD, ATCRBS lBK, MODE 5-1K

---- NOLOAD, RTCRBS 1K, MODE 5-1K · · · · · · NOLOAD 1 ATCRB5 20KI MODE 5-1K 100- ·-----------, .. r~ ,.,.,. ..... ~·. ·~. I

se

70

60

se

\ 40

30

20~~~~~-~~~~~~~~~~~~~~~~~~~~~

-&8.BB -&3.58 -&7.88 -78.58 -74.BB -77.58 -et.aa -&4.58 -ae.ee -91.58 -ss.aa SIGNAL LEVEL Cdbm)


CARDION DME MODEL FA9783/3, CHANNEL SSX

---NOLOAD ------ NOLOAD, ATCRBS 1BI< 1 MODE S-1K

---- NOLOAD ATCRBS I K MODE 5-1 K · · · · · · NOL.OAD, ATCRBS ZBI< 1 MODE 5-1 K

100 ----- I - • .. .. ------- --· I . _w~• -----....=:o=:....... ....,..uc__,.,--- ' I

90 -····Z7:~y~ i . \~ I.

sa

70

·'' \1

· .. ~~ I ·~ I -------------- --~l

~· t

·5: l ~ l U ~ I .l\ 1

·.~ '

40 :i\ I t :~ I

::L ......................................... , ... \1 -68.111 -63.58 -67 .BB -78.58 -7UII -77.58 -BUJIJ -84.59 -88.BB -9l.SB -!5.81!

SIGNAL LEVEL Cdbm)


24

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