Tower Mounted Low Noise Amplifier DLNA900 GSM or NMT/CDMA


DLNA 900  

GSM Antenna Diplexer 
(Sponsored by Westel 900 GSM Rt.) 

Table of contents:
1. General Description 
2. Structure 
3. Technical Description 
3.1. Outdoor Container 
3.2. Power Supply and     Indicator Cabinet 
3.3. Indoor DC Separator 
4. Technical Parameters 

1. General Description

The DLNA 900 GSM antenna diplexer is used on the base stations of the GSM 900 mobile telephone system. It extends the receiving sensitivity of the base station that uses the same transceiver antenna. This way the signal coverage area is enlarged. At the same time, within the GSM cell, the connection between the subscriber and the base station will be more stable.

The DLNA 900 antenna diplexer is placed near the antenna, between the coax connection cable coming from the base station (BTS) and the antenna connection (ANT). The diplexer separates the transmitter and receiver signals coming from both the antenna (ANT) and the base station (BST) as per the signal's direction. At the same time a low noise preamplifier (VLNA 900) is placed in the way of the receiver signal(s) coming from the antenna. The amplified signal(s) are then sent to the shared cable connection (BTS). In the transmission direction the transmitter signals are sent to the antenna connection (ANT) via a low attenuation transmitter filter. The high selectivity receiver filters of the diplexer make sure that the high level transmission signals do not get into the receiver branch amplifier thus causing over-control or intermodulation mixture. In case the active circuit (low noise pre amplifier) breaks down, or there is power shortage, the bypass operation mode will start. This means that the signal route goes around the amplifiers via relays but the connection will stay alive. In other words there is no service outage, only the connection's parameters are deterred until the problem is fixed.

The local alarm circuit of the indoor power supply and the indicator cabinet, as part of the system, visually show the normal operation (green LED) or alarm (red LED) status of the system. At the same time this information is taken to Morse relay contacts that can be connected to the remote management system of the station. One, fully configured cabinet is able to manage the unified signals from 6 transmitters/receivers.

The outdoor unit containing the diplexer and the low noise preamplifier is in a hermetically closed weatherproof container protecting the unit against climate changes. The basic configuration enables connection to both horizontal and vertical masts. Summarizing the above, the DLNA 900 diplexer is offering the following functions and advantages to the user:

  •  enables the use of the same antenna for both the transmitter and the receiver.

  • the low noise amplifier added to the receiving branch, as part of the system, disables cable attenuation thus increasing receiver sensitivity, which equals the enlargement of the BTS coverage area

  • in transmission direction the low attenuation with high selectivity filter added in the path of the transmitter signal lowers the emitted signal level only, while providing enough attenuation on the receiving frequency not to absorb any of the receiving signal.

  •  the receiver filters of the diplexer, besides the low passband attenuation, have a significant closing band attenuation to the nearby transmission signal. This way the highest allowed level transmission signals  cannot cause a disturbing signal comparable with the level of the possible useful receiver signal (neither directly nor in a mixture format.)

  • any alarm of the amplifier or power shortage make the bypass mode come on, this way there is no drop in the connection.

  • local display, system operation status and remote management information is available

  • the system is easy to install. The outdoor container can be connected to either horizontal or vertical masts. The indoor power supply and indicator cabinet can be installed on the wall (or a vertical pane).

2. Structure

Figure 1. shows the layout structure of the system and how the DLNA 900 GSM system can be connected to an existing base station.The outdoor container with the antenna diplexer is fixed to a mast holding the station's antenna assembly. A short jumper cable connects one of the 7/16(-) connectors of the container to the shared transceiver antenna while the coax cable connecting the outdoor and indoor units of the equipment is connected to another similar 7/16(-) connector (BTS). (These coax cables are already part of the base station).
There is a power supply separator installed on the unified RF output of the base station (BTS). The separator ensures that the necessary 7/16 type RF connectors have negative/positive (female/male) outlets this way the existing cables can be used without alterations and the DC connection spot is obvious. The +15V nominal voltage DC shielded cable has to be connected to the XLR connectors. The other end of the +15V cable is connected to the power supply cabinet.
The -48V primary power supply of the equipment is connected to the power supply and indicator cabinet. The XLR DC connectors and the D-SUB connector containing the contact outlets for the remote management are on the shared lower connector panel. (For better viewing Figure 1. shows outlets supplying only one transceiver.)

3. Technical Description

3.1. Outdoor Container
The theoretical operation of the outdoor container is shown on the following block scheme outline (Figure 2.). From transmission direction the incoming signal from the shared cable to the BTS connector goes through the DC separator to a shared resonator. From here the only way for the signal to go is in the transmission filter because the steep slope Receiver Filter 2 reflects the signal from the other input. The transmission signal is sent through the signal filter and the ANT side shared resonator to the ANT shared antenna connector. From the construction's point of view, the transmission filter includes 5 high quality inductive connection coax resonators. While having only 0,5 dB pass attenuation it also has significant reflection to the operational receiver band in the operational passband.
In receiving direction the signal coming from the antenna goes through the shared cavity to the Receiver Filter 1 from where it goes to the VLNA 900 low noise amplifier. The Receiver Filter 1 includes 7 high quality inductive connection coax resonators. The Receiver Filter 1 has to prevent high level transmission signals from getting into the low noise amplifier, this way the level of the intermodulation mixtures made up of the transmission signals and the transmission and receiver signals will be lower than the threshold of the useful receiver signal. Another two suction loops are included in the output resonator in order to achieve a higher depression of the third grade intermodulation product on the critical points of the receiver band (935-940 MHz).
The primary role of the VLNA 900 low noise preamplifier is to lower the derived noise factor of the entire receiver side. This is possible because the attenuation of the connecting coax cable is out of the noise scale due to its low noise factor and amplification. Even with shared antenna usage, the receiver direction hop attenuation is lowered by a value complying to the cable attenuation. Another requirement from the amplifier is that it have high IP3 (third grade intersection) value contrary to the transmission signals appearing on the shared connector and to the high level receiver signals mixture (which is allowed in the specification but in reality is very unlikely).
Should any alarm occur in the amplifier the connection will go down. There is a bypass in this case; when alarm occurs the Morse type relays at the amplifier input and output will open and the connection stays on through the route going around the active circuits even at 1 dB quality deterioration until the error is corrected.
Power is supplied to the amplifier by the DC separator which has a lower pass filter type high frequency conductor making sure that the RF signals cannot seep through to the amplifier neither galvanically nor through scattering. From the amplifier output the receiver signal goes to the output side Receiver Filter 2.
The difference is that for the protection of the amplifier outlet it is not necessary to have additional suction loops, as the 7 resonator filter provides enough protection against the BTS side transmission signals.
The mechanical structure of the outdoor container is shown by Figure 3.
The transmission filter and the two receiver filters are in a single cut-out block (diplexer). The amplifier (VLNA) is built in a separate shielded metal housing. The signal is sent to the receiver filters through the SMA connectors and semi rigid cables on the amplifier box. The cut block containing the filters and the amplifier are secured on the closing lid of the container.
One of them is the DC separator; as the amplifier gets the +15V DC voltage through its high frequency conductor.The rubber ring (not shown in the drawing) installed in the slot on the closing lid and one part of the mast support assembly can be initially fastened to the U-holder welded to the outdoor container. The other part of the support assembly has to be assembled to the mast during the on-site installation. The following drawings show how to secure the container to horizontal or vertical masts. The housing of the container is made of drawn aluminum. The outside is coated with oven baked fiber glass special compound. The outside connecting assemblies are made of corrosion proof material.


Figure 3  

3.2. Power Supply and Indicator Cabinet

The cabinet can be installed on the wall or on any vertical panel, in its full configuration supplies +15V to six VLNA 900 low noise pre amplifiers from the outdoor containers in such a way that a printed circuit card serves two amplifiers  (Panels 1, 2 and 3). In its basic configuration two printed boards are installed in the cabinet. A shared DC/DC converter receives the incoming primary (battery) power.
The amplifiers have a built-in self- monitoring control system. It emits visual signals for the local control: normal operation mode is indicated by a green LED, the alarm mode is indicated by a red LED. The circuit evaluating the performance also controls a Morse relay. The relay contacts' outlets are on the connector panel and this way are available for the remote management system.
The connector panels on the bottom of the cabinet contains all connectors necessary for the user. Figure 6. shows the connector panel with connector positions. As it is shown, the ascending +15V power for each amplifier appears on the XLR connector that has to be cable connected to the similar connection type indoor DC separators (1A, ..., 3B).
The corresponding panels' remote management contact band outlets are on connectors CS1 ... CS3 D-SUB (often used in computer technology) as follows:
Amplifier Mark, Normal mode, Alarm Mode
A, 9-5: RZ  9-4: SZ, 9-4: RZ  9-5: SZ
B, 3-2: RZ  3-1: SZ, 3-1: RZ  3-2: SZ

The -48V primary power supply cable has to go through the "INPUT/-48V" clamp on the panel and the 6A fuse has to be inserted directly in the connecting bar of the DC/DC converter.
The power supply and indicator cabinet has a lockable door. The cabinet is supplied with a connection necessary for the protective grounding. In basic configuration the cabinet has 2 panels, the third panel can be installed on-site.


3.3. Indoor DC Separator

The indoor DC separator can be directly connected to the 7/16 unified transceiver outlet of the base station frame, while its connection to the ascending coax cable is similar to the frame outlet 7/16(-). The power supply (+15VDC) is connected through the XLR type connector.
The DC separator has to establish a power supply for the low noise amplifier through the inner conductor of the ascending coax cable with input side separation in such a way that the attenuation to be established RF signal route be the minimum, the reflective attenuation in both bands be the maximum and the RF seeping towards the power supply input be highly suppressed.
The structure DC separator without cover is shown in Figure 7. below. The serial C condensation established in the RF route to the BTS separates the DC. Towards the power supply the F throttle and the SZ through filter prevents the RF signal to exit towards the DC input. The D1 diode installed parallel on the DC input protects against overcharge (lightning). The RF transmission route can be tuned to minimal reflection in the entire transmission band by the tuning islands welded between the DC (not indicated on the drawing).


For more Photos on real installations go to services...

4. Technical Parameters
As per GSM 900
- Receiver 890 - 915 MHz
- Transmitter 935 - 960 MHz
-Transmitter Branch 
    (BTS to ANT) 
Passband Insertion  Loss 0.5 max. dB
In-Band Fluctuation +/- 0.1 max dB
Reflection Loss 16 max. dB
Transmitter Output Power 47 max. dBm
Group Delay Distortion 
  (BTS to ANT)
80 +/- 20 max. ns
Infinite VSWR No Damage
-Receiver Branch 
  (BTS to ANT) 
Pass-Band Fluctuation +/- 0.5 max dB
Noise Figure 
T=25 C  1.7 max. dB
T=65 C 2.1 max. dB
Third Order Intercept Point  27 min. dBm
Reflection Loss (ANT, BTS) 16 min. dB
Group Delay Distortion 120 +/- 25 max. ns
General Data of the Outdoor  
MTBF 150,000 h
Connector type coaxial, 50 Ohm
     -ANT port 7/16 (female)
     -BTS port 7/16 (male)
Mounting  Mast is preferred
Diameter of mast  110 max. mm
Position of mast vertical or horizontal
Temperature Range
        -operating status  -25 C to +55 C
        -storage -35 C to +65 C
Projection against lighting  As per IEC 1024
Machanical Construction of the Outdoor 
Weatherproof Container
INDOOR Unit Assembly     
DC By-Pass Adapter
Frequency Band  890 to 960 MHz
Insertion Loss 0.2 max. dB
Reflection Loss 25 min. dB
Max. allowed RF Power  50 dBm
DC to RF Isolation  110 min. dB
Current Load 2 max. A
Connector Type coaxial, 50 Ohm
             -BTS Port 7/16male
DLNA 900 Power Supply and                  
alarm Unit 
No. of Outdoor Units to drive  max. 6(3 PCB cards)
    Basic mounting  4(2 PCB cards)
Visual display of the operation  
          - normal operation green LED
          - alarm (by-pass or decoupled 
red LED
Remote Control Acces  relay contacts:
    -1 status  - short circuit
    -2 status - open circuit
Mechanical Construction Box to be mounted on the wall

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