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Power Amplifier Module

 

Introduction 

 

In order to deploy test networks for the demonstration and teaching innovative ideas through experimentation in a realistic radio propagation and application scenario, we have developped a  Power Amplifier Module, which can be connected to our RF boards (PLATON, cardbus MIMO I, agileRF). With the Power Amplifier Module the network deployed around the Eurecom buildings comprises a BTS (range 500m, Power = +34 dBm, frequency range : 1880-1920 MHz) and several mobile terminals. Both BTS and terminal are PC based (high-end servers for the base Stations and laptops for mobile terminal). On the BTS side, the antennas are put on the roof of the Eurecom building and are connected to a  Power Amplifier Module (one per antenna) which amplifies the signal both at the reception side and the transmission side. This  Power Amplifier Module is connected to the rest of the system (located in the buildings) through RF cables.

 

 

 

installation of the Power Amplifier Module on the roof of the Eurecom building

 

 

General overview

 

On a functional point of view, a Power Amplifier Module comprises of:

  • A power amplifier on the transmitter part;
  • A RX/TX switch;
  • A pass band filter;
  • A Low Noise Amplifier (LNA) for the receiver part.

 

Moreover, the Power Amplifier Module is interfaced with:

  • The RF front-end located in the buildings;
  • The antennas located near the high power box one a pylon.

 

 

 Hardware implementation

The hardware implementation is depicted in the Figure below 

     Internal view of the module

 

 

      

   

Detailed view of the module

 

The power amplifier is a Linear LDMOS Amplifier MHL 19936 from Motorola. This PA has been originally designed for the US PCS band. It is a class A amplifier with a gain around 30 dB and an output power typically around 10 Watt. The Rx/Tx switch is a customized product from KPMC Microwave Components, Inc.

 

Originally designed for military applications, this switch has the following performance:

  • Insertion loss : 1 dB max
  • Switching speed : 750 n sec max
  • Power handling : 20 Watts
  • Attenuation : 42 dB min

 

The Low Noise Amplifier is a GaAs MMIC Amplifier from Agilent Technology (MAG 86563). Performances are the following:

  • Gain : 22 dB
  • Noise Figure : 1.6 dB
  • 1dB compression point : + 3 dBm

 

The filter is a cavity band pass filter with the following performances and features:

  • Center frequency : 1910 MHz
  • 1 dB pas band : 20 MHz
  • Handled power : 33 dBm
  • Insertion loss : 2 dB max
  • Attenuation outside the band : 50 dB at 1880 MHz, 30 dB at 1930 MHz
  • Number of sections : 6

 

In addition to the critical parts (PA, switch, filter and LAN), the box is also comprising:

  • A industrial 28 V power supply
  • A static relay : its role it to shutdown the 28 V power supply

 

Interfaces and command lines

As shown in the Figure 3-9 the high power box is interfaced with an antenna and a RF front end. On the antenna side, the connector is in a "N" factor form, and the antenna is connected through a "low loss" cable.

The antennas typically used are from Kathrein. This kind of antenna is typically used for a base station. The main features of our antenna are the following:

  • Frequency range : 1850-1990 MHz
  • Gain : 12 dBi
  • Half power beam width : horizontal 65° and vertical 30°
  • Max power : 150 Watt

 

 

Antenna on the roof of EURECOM's building

 

 

The interfaces with the RF front end are:

  • The transmitted signal from the RF front end that is amplified by the PA and transmitted through the antenna (labeled TX IN in Figure 3-9);
  • The received signal from the antenna that is amplified by the LNA and sent to the RF front end (labeled RX OUT in Figure 3-9);
  • Two command lines: one for the RX/TX switch (generated by the RF board, in TTL 5V) and one for the shutdown of the high power box (if the signal is in the "LOW" state, it shutdown all the active components through the static relay). Those command lines are gathered in a 6-wires cable labeled CONTROL in Figure 3-9.