Instrument Function > Modulation > DME Modulation > DME Modulation Settings
DME Modulation Settings

Access:

 

Select "Modulation > config... > DME".

The "DME Modulation" dialog contains the channel, pulse pair and trigger parameters, and the parameters for setting the modulation. To measure the "Reply response", use an R&S NRP-Z81 Wideband Power Sensor.

The remote commands required to define the DME modulation settings are described in "SOURce:DME Subsystem".

State - DME Modulation

Activates the DME modulation

Note: Modulations PULSE, VOR, ILS-GS, ILS-LOC, MKR-BCN, ADF, AM, and internal FM/PhiM are automatically switched off when DME modulation is activated. Also, the pulse generator is automatically deactivated.

The DME modulation signal can be output at the LF connector.

Note: Automatic Level Control is deactivated with DME modulation.

When pulse modulation is activated, the R&S SMA deactivates ALC automatically ("ALC OFF", i.e. switches to "Sample & Hold" state).

The "Sample&Hold" state opens the ALC loop, and disables the automatic control of the output level. The level modulator is set directly.

However, to correct the output level, the R&S SMA executes a "Sample & Hold" measurement after each change of frequency or level settings.

The nominal level is ON for typically 3 ms to 5 ms after level or frequency setting, if:
  • No attenuator is fitted (frequency option R&S SMA-B103L/B106L)
  • "High Power" mode is enabled
  • "Auto" mode is enabled, and if the level is in the range of the high power, i.e. the mechanical relay bypass is switched.

The level is decreased by 30 dB during "Sample & Hold" measurement.

Remote command: 
 
Mode - DME Modulation

Selects the DME modulation mode. The mode determines the signal type that is simulated. The exact timing of the signal for each mode is determined by the selected channel (X or Y, see below).

The timing and shape of the pulses can be freely selected. By default these values are set according to the standard.

"DME Interrogation CH X/Y"

The interrogation signal of the airborne transmitter is simulated.

The following graph shows the interrogation signal of channel X.

DME interrogation CH X (Trigger = Auto)
1 = SYNC signal (pulse width 50 ns)
2 = VIDEO signal (active with 50 % pulse width of first DME pulse)
3 = LF Output signal (DME modulation signal)
4 = RF Output signal (measured with external detector)

"DME Reply CH X/Y"

The reply signal of the ground-based transponder is simulated. The trigger is automatically set to external and the default trigger delay either to 50 µs (channel X) or 56 µs (channel Y) depending on the selected channel. The trigger signal is input via the PULSE EXT connector.

The interval between the pulse pairs can be set to a fixed value (repetition rate) or to random generation (pulse squitter).

The following graph shows the reply signal of channel X (Trigger = External). In case of a trigger event, the reply pulse pair is generated after the set trigger delay.

DME reply CH X (Trigger = External)
1 = external TRIGGER signal (T: pulse width 50 ns)
2 = SYNC signal (pulse width 50 ns)
3 = VIDEO signal with a delay of 50 µs between external trigger and video signal (= range distance of 0 nm) (active with 50 % pulse width of first DME pulse)
4 = LF Output signal (DME modulation signal)
Remote command: 
 
Channel Mode - DME Modulation

Selects the channel that is simulated.

Standard compliant X and Y channels differ in the spacing between the two pulses of the pulse pair and the delay of the ground station (see table below). ICAO indicates the ICAO channel parameter below for selecting the ICAO channel.

Channel

Pulse spacing

interrogation mode

Pulse spacing

reply mode

Reply delay

1st pulse

Reply delay

2nd pulse

X

12 us

12 us

50 us

50 us

Y

36 us

30 us

56 us

50 us

Remote command: 
 
ICAO Channel - DME Modulation

Selects the ICAO channel, i.e., the DME transmitting frequency. The RF frequency is set to the value selected here.

The individual values in the table are:
  • Ch. No. = ICAO channel number
  • VOR freq. = VOR interrogation frequency (MHz)
  • DME interrog. freq. = DME interrogation frequency (MHz)
  • DME reply freq. = DME reply frequency (MHz)
Standardized DME transmitting frequencies (MHz) and the associated ICAO channels for interrogation and reply

Ch. No.

VOR freq.

DME interrog. freq.

DME reply freq.

 

Ch. No.

VOR freq.

DME interrog. freq.

DME reply freq.

 

Ch. No.

VOR freq.

DME interrog. freq.

DME reply freq.

1X

1Y

 

1025

1025

962

1088

 

43X

43Y

110.60

110.65

1067

1067

1004

1130

 

85X

85Y

113.80

113.85

1109

1109

1172

1046

2X

2Y

 

1026

1026

963

1089

 

44X

44Y

110.70

110.75

1068

1068

1005

1131

 

86X

86Y

113.90

113.95

1110

1110

1173

1047

3X

3Y

 

1027

1027

964

1090

 

45X

45Y

110.80

110.85

1069

1069

1106

1132

 

87X

87Y

114.00

114.05

1111

1111

1174

1048

4X

4Y

 

1028

1028

965

1091

 

46X

46Y

110.90

110.95

1070

1070

1007

1133

 

88X

88Y

114.10

114.15

1112

1112

1175

1049

5X

5Y

 

1029

1029

966

1092

 

47X

47Y

111.00

111.05

1071

1071

1008

1134

 

89X

89Y

114.20

114.25

1113

1113

1176

1050

6X

6Y

 

1030

1030

967

1093

 

48X

48Y

111.10

111.15

1072

1072

1009

1135

 

90X

90Y

114.30

114.35

1114

1114

1177

1051

7X

7Y

 

1031

1031

968

1094

 

49X

49Y

111.20

111.25

1073

1073

1010

1136

 

91X

91Y

114.40

114.45

1115

1115

1178

1052

8X

8Y

 

1032

1032

969

1095

 

50X

50Y

111.30

111.35

1074

1074

1011

1137

 

92X

92Y

114.50

114.55

1116

1116

1179

1053

9X

9Y

 

1033

1033

970

1096

 

51X

51Y

111.40

111.45

1075

1075

1012

1138

 

93X

93Y

114.60

114.65

1117

1117

1180

1054

10X

10Y

 

1034

1034

971

1097

 

52X

52Y

111.50

111.55

1076

1076

1013

1139

 

94X

94Y

114.70

114.75

1118

1118

1181

1055

11X

11Y

 

1035

1035

972

1098

 

53X

53Y

111.60

111.65

1077

1077

1014

1140

 

95X

95Y

114.80

114.85

1119

1119

1182

1056

12X

12Y

 

1036

1036

973

1099

 

54X

54Y

111.70

111.75

1078

1078

1015

1141

 

96X

96Y

114.90

114.95

1120

1120

1183

1057

13X

13Y

 

1037

1037

974

1100

 

55X

55Y

111.80

111.85

1079

1079

1016

1142

 

97X

97Y

115.00

115.05

1121

1121

1184

1058

14X

14Y

 

1038

1038

975

1101

 

56X

56Y

111.90

111.95

1080

1080

1017

1143

 

98X

98Y

115.10

115.15

1122

1122

1185

1059

15X

15Y

 

1039

1039

976

1102

 

57X

57Y

112.00

112.05

1081

1081

1018

1144

 

99X

99Y

115.20

115.25

1123

1123

1186

1060

16X

16Y

 

1040

1040

977

1103

 

58X

58Y

112.10

112.15

1082

1082

1019

1145

 

100X

100Y

115.30

115.35

1124

1124

1187

1061

17X

17Y

108.00

108.05

1041

1041

978

1104

 

59X

59Y

112.20

112.25

1083

1083

1020

1146

 

101X

101Y

115.40

115.45

1125

1125

1188

1062

18X

18Y

108.10

108.15

1042

1042

979

1105

 

60X

60Y

 

1084

1084

1021

1147

 

102X

102Y

115.50

115.55

1126

1126

1189

1063

19X

19Y

108.20

108.25

1043

1043

980

1106

 

61X

61Y

 

1085

1085

1022

1148

 

103X

103Y

115.60

115.65

1127

1127

1190

1064

20X

20Y

108.30

108.35

1044

1044

981

1107

 

62X

62Y

 

1086

1086

1023

1149

 

104X

104Y

115.70

115.75

1128

1128

1191

1065

21X

21Y

108.40

108.45

1045

1045

982

1108

 

63X

63Y

 

1087

1087

1024

1150

 

105X

105Y

115.80

115.85

1129

1129

1192

1066

22X

22Y

108.50

108.55

1046

1046

983

1109

 

64X

64Y

 

1088

1088

1151

1025

 

106X

106Y

115.90

115.95

1130

1130

1193

1067

23X

23Y

108.60

108.65

1047

1047

984

1110

 

65X

65Y

 

1089

1089

1152

1026

 

107X

107Y

116.00

116.05

1131

1131

1194

1068

24X

24Y

108.70

108.75

1048

1048

985

1111

 

66X

66Y

 

1090

1090

1153

1027

 

108X

108Y

116.10

116.15

1132

1132

1195

1069

25X

25Y

108.80

108.85

1049

1049

986

1112

 

67X

67Y

 

1091

1091

1154

1028

 

109X

109Y

116.20

116.25

1133

1133

1196

1070

26X

26Y

108.90

108.95

1050

1050

987

1113

 

68X

68Y

 

1092

1092

1155

1029

 

110X

110Y

116.30

116.35

1134

1134

1197

1071

27X

27Y

109.00

109.05

1051

1051

988

1114

 

69X

69Y

 

1093

1093

1156

1030

 

111X

111Y

116.40

116.45

1135

1135

1198

1072

28X

28Y

109.10

109.15

1052

1052

989

1115

 

70X

70Y

112.30

112.35

1094

1094

1157

1031

 

112X

112Y

116.50

116.55

1136

1136

1199

1073

29X

29Y

109.20

109.25

1053

1053

990

1116

 

71X

71Y

112.40

112.45

1095

1095

1158

1032

 

113X

113Y

116.60

116.65

1137

1137

1200

1074

30X

30Y

109.30

109.35

1054

1054

991

1117

 

72X

72Y

112.50

112.55

1096

1096

1159

1033

 

114X

114Y

116.70

116.75

1138

1138

1201

1075

31X

31Y

109.40

109.45

1055

1055

992

1118

 

73X

73Y

112.60

112.65

1097

1097

1160

1034

 

115X

115Y

116.80

116.85

1139

1139

1202

1076

32X

32Y

109.50

109.55

1056

1056

993

1119

 

74X

74Y

112.70

112.75

1098

1098

1161

1035

 

116X

116Y

116.90

116.95

1140

1140

1203

1077

33X

33Y

109.60

109.65

1057

1057

994

1120

 

75X

75Y

112.80

112.85

1099

1099

1162

1036

 

117X

117Y

117.00

117.05

1141

1141

1204

1078

34X

34Y

109.70

109.75

1058

1058

995

1121

 

76X

76Y

112.90

112.95

1100

1100

1163

1037

 

118X

118Y

117.10

117.15

1142

1142

1205

1079

35X

35Y

109.80

109.85

1059

1059

996

1122

 

77X

77Y

113.00

113.05

1101

1101

1164

1038

 

119X

119Y

117.20

117.25

1143

1143

1206

1080

36X

36Y

109.90

109.95

1060

1060

997

1123

 

78X

78Y

113.10

113.15

1102

1102

1165

1039

 

120X

120Y

117.30

117.35

1144

1144

1207

1081

37X

37Y

110.00

110.05

1061

1061

998

1124

 

79X

79Y

113.20

113.25

1103

1103

1166

1040

 

121X

121Y

117.40

117.45

1145

1145

1208

1082

38X

38Y

110.10

110.15

1062

1062

999

1125

 

80X

80Y

113.30

113.35

1104

1104

1167

1041

 

122X

122Y

117.50

117.55

1146

1146

1209

1083

39X

39Y

110.20

110.25

1063

1063

1000

1126

 

81X

81Y

113.40

113.45

1105

1105

1168

1042

 

123X

123Y

117.60

117.65

1147

1147

1210

1084

40X

40Y

110.30

110.35

1064

1064

1001

1127

 

82X

82Y

113.50

113.55

1106

1106

1169

1043

 

124X

124Y

117.70

117.75

1148

1148

1211

1085

41X

41Y

110.40

110.45

1065

1065

1002

1128

 

83X

83Y

113.60

113.65

1107

1107

1170

1044

 

125X

125Y

117.80

117.85

1149

1149

1212

1086

42X

42Y

110.50

110.55

1066

1066

1003

1129

 

84X

84Y

113.70

113.75

1108

1108

1171

1045

 

126X

126Y

117.90

117.95

1150

1150

1213

1087

Remote command: 
 
Range Distance - DME Modulation

("Reply Mode" only)

Sets the simulated distance between interrogator and transponder for reply mode. The distance is given in nautic miles (nm). 1 nm is 1852.01 meters and corresponds to a run time of 12.359 µs.

The range distance and the external trigger delay are interdependent according to:

"Range Distance" = ("Trigger Delay" – X/Y mode delay) / 12.359 µs/nm,

where:

X mode delay = 50 µs, Y mode delay = 56 µs

Changing one value automatically changes the other value.

Remote command: 
 
Pulse Squitter - DME Modulation

The average repetition rate is 2700 pp/s. The pulse spacing is distributed randomly in the range of 60 µs to about 1500 µs according to EUROCAE EN-54 6.2.12.

The squitter pulses are constantly sent by the ground station in order to ensure proper operation and in order to ease synchronization of the aircraft interrogator to the ground station.

Remote command: 
 
Pulse Repetition Rate - DME Modulation
  • In "Interrogation mode"
    Sets the pulse repetition rate for trigger setting "Auto" or "Ext Gated".
  • In "Reply Mode"
    Indicates the mean pulse repetition rate in squitter mode.
Remote command: 
 
Reply Efficiency - DME Modulation

("Reply Mode" only)

Sets the relation between reply pulse pairs and received trigger signals. E.g. with a set efficiency of 50 % only every second trigger event leads to the generation of a reply pulse pair.

Remote command: 
 
Trigger - DME Modulation

Accesses the dialog for setting the trigger parameters (see "Trigger Settings for DME").

ID Settings - DME Modulation

("Reply Mode" only)

Accesses the dialog for setting the DME ID signal parameters (see "ID Settings for DME Reply Mode").

Pulse Shape - DME Modulation

Selects the pulse shape.

"Cos^2"

The falling and the rising edge of the pulse are cos^2 shaped.

"Cos Cos^2"

The rising edge is cos shaped and the falling edge is cos^2 shaped.

"Linear"

The falling and the rising edge of the pulse are shaped linear.

Remote command: 
 
Pulse Rise - DME Modulation

Sets the rise time of the pulse (10 % to 90 % of peak voltage).

Remote command: 
 
Pulse Width - DME Modulation

Sets the pulse width (50 % to 50 % of peak voltage).

Remote command: 
 
Pulse Fall - DME Modulation

Sets the fall time of the pulse (90 % to 10 % of peak voltage).

Remote command: 
 
Pulse Spacing - DME Modulation

Sets the spacing between the first and second pulse of a pulse pair. I.e. the time between half-voltage points on the leading edge of each pulse.

Remote command: 
 
Single Pulse - DME Modulation

Activates generation of a single test pulse.

Remote command: 
 
Echo Pulse - DME Modulation

("Pulse Squitter > Off" only)

Activates an echo pulse pair. The echo pulses have the same shape and timing as the original pulses.

You can determine the delay and attenuation of the echo pulses, see "Echo Delay - DME Modulation", and "Echo Attenuation - DME Modulation".

Remote command: 
 
Echo Delay - DME Modulation

("Echo Pulse > On" only)

Sets the delay from the first original pulse to the first echo pulse.

Remote command: 
 
Echo Attenuation - DME Modulation

("Echo Pulse > On" only)

Sets the attenuation of the echo pulses compared to the original pulses. A positive attenuation leads to echo pulses with reduced amplitude compared to the original pulses. A negative attenuation leads to echo pulses with increased amplitude compared to the original pulses.

Remote command: 
 
Low Spectral Emission - DME Modulation

Activates the generation of a DME signal with higher spectral purity but less dynamic compared to the default mode. The ON/OFF ratio of the pulses is reduced from >100 dB to 35 dB typically.

Remote command: 
 
Composite AM... - DME Modulation

("Reply Mode" only)

Accesses the dialog for defining the two-tone signals that can be additionally superimposed on the pulses (see "DME Composite AM Settings").

DME Analysis - DME Modulation

(Only if an R&S NRP-Z81 power sensor is connected to the R&S SMA sensor connector)

Accesses the dialog for setting the "DME Analysis" (see "DME Analysis").

Set To Default - DME Modulation

Sets a default DME signal (interrogation mode channel X).

Selects the default settings for the pulse parameters according to standard (EUROCAE ED57/ED54 and ICAO ANNEX 10 to the convention of international civil aviation).

This button does not impact the modulation state.

Remote command: 
 
Adjust DME Pulse Slope

Activates internal adjustment of the DME pulse slope for best linearity.

Remote command: 
 

 


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