RF Transceiver Design

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  • .

    Anil Kumar Pandey

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    Application Design Scope and Objective

    This flow demonstrates the usage of multiple technologies based on different PDKs , LTCC, Packaging, 3DConnector and RF board defined in separate libraries along with ADS standard libraries to realize the completedesign transceiver layout for EM simulation.

    The transceiver system that has been designed consists ofmainly Seven major technologies:1. SPDT : Based on not-linear demo kit2. LNA : Based on non-linear MT kit3. Power Amplifier : X-parameter file of MMIC power

    amplifier4. LTCC BPF : 3 pole low pass filter based on 6 layer LTCC

    technology5. Connector from EMPro as OA library : 3D SMA

    Connecter modeled in EMPro6. QFN Package : Standard QFN package for LNA and SPDT

    switch packaging7. Antenna : single layer C-band microstrip patch antenna

    The LNA and SPDT are designed using two different PDKs having different technologies defined in two separatelibraries whereas as Antenna and PA are designed using ADS standard libraries. Layer stack and material propertiesin these two PDKs are same but naming of components and color code is different. LTCC Low pass filter is designusing LTCC technology . The complete transceiver circuit is realized in layout using side by side nested technology .FEM simulation is carried out without active components in layout for complete system. The design is thensimulated for S-Parameter in schematic with EM model along with active components .

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    Transceiver and its Applications

    PA

    LNA

    T/R Module

    SW

    PA

    LNA

    T/R Module

    SW

    PA

    LNA

    T/R Module

    SW

    PhaseShifter

    PhaseShifter

    Antenna Linear Array

    PD

    Antenna Linear Array

    Antenna Linear ArrayPhaseShifter

    PD

    Pow

    er D

    ivid

    er/

    Com

    bin

    er N

    etw

    ork

    A transceiver is a device comprising both a transmitter and a receiver which arecombined and share common circuitry or a single housing. When no circuitry iscommon between transmit and receive functions, the device is a transmitter-receiver

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    Transmit/Receive chain at C-Band (5 GHz)

    Technologies:

    AntennaPA LNA SPDT

    PDK1

    MMICs

    PDK2

    BPF

    LTCC Microstrip

    LNA

    PA

    SPDT Switch

    BPF

    Receiver

    Transmitter

    Switch Control

    AntennaTransceiver

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    Transceiver System: Cross section view

    PackagedPower Amp

    PTH

    DC LinesMicrostrip Ground Plane

    Patch Antenna

    MMIC

    LNA Filip Chip

    QFN Package

    MMIC

    SPDT Filip Chip

    QFN Package

    LTCC LPF

    SMA Connector

    MMIC LNA

    PA

    MMIC SPDT

    LTCC LPF

    Backside Microstrip Patch

    Antenna

    SMA ConnectorDC Bias lines

    Transceiver System Design in ADS

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    Transceiver Design flow in ADS

    Component specifications

    Choice of topology Choice of the active device

    Active device characterization-DC IV bias point

    Tuning / optimization / design centering

    Designing with Foundry / DK elements Re Optimization

    Linear simulation for insertion loss and isolation

    Generation of Layout (LVS feature)

    Schematic generation

    Linear simulation for insertion loss and isolation.

    Transient /Envelop simulation

    Incorporate pre-simulated PA data file as database component

    Design of C-band microstrip antenna on Alumina

    Prepare Antenna for nested Technology

    RF board design with all components as nested technology

    Optimization and RF board for better performance

    FEM- Simulation of complete RF board

    Circuit simulation of complete Transceivers in schematic along wit h active components

    MMIC Chip Design (LNA & SPDT)

    Layout Design EM sim

    EM co-simulation with FETs

    Tuning / optimization / design centering

    Using Stacked nested technology for Chip + Package

    EM simulation of Package + MMIC Chip

    EM co-simulation of Package + MMIC Chip along with FETs

    Design of Bandpass filter in schematic

    Realization of BPF in layout using LTCC technology

    Prepare LTCC BPF for nested Technology

    LTCC BPF design

    Microstrip Antenna Design

    PA Design

    RF board with Side by Side MTM

    Complete Systems with Connector

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    Board

    Chip

    ModuleDesign Components

    1. SPDT : Based on not-linear demo kit2. LNA : Based on non-linear MT kit3. Power Amplifier : X-parameter file of MMIC power amplifier4. LTCC BPF : 3 pole low pass filter based on 6 layer LTCC technology5. Connector from EMPro as OA library : 3D SMA Connecter

    modeled in EMPro6. QFN Package : Standard QFN package for LNA and SPDT switch

    packaging7. Antenna : single layer C-band microstrip patch antenna

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    Total 12 equivalent layer board 7 different technologies 2 stack up + 4 side by side technologies EMPro design as OA lib component 3 different layout units

    mm ( millimeter)

    mil

    um

    Side by Side MTM Substrate

    MMIC SPDT Substrate

    MMIC LNA Substrate

    SPDT + Package SubstrateLNA + Package Substrate

    Antenna Substrate

    LTCC LPF

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    Low-noise amplifiers (LNAs) are critical for extracting signals fromnoise in communications receivers. The Non-Linear MT versionof MMIC demo kit contains MESFETs with non-linear modelswhich can be used as basic LNA elements. In designing the LNA,the first step is to decide which profile provides the bestcombination of features and performance. The next step is tochoose device size. Device size will affect the LNA's bandwidth,DC power consumption, noise figure, and nonlinear performance.Here First LNA has been realized using ideal component isschematic then with demo kit components. From schematicdesign , a layout design is created for EM simulation. LAN isintegrated with QFN package using stacked nested technology.

    MMIC LNA DesignTechnology-1

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    LNA EM Cosimulation

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    LNA on QFN Package : EM simulation dataFEM Solver: DM64 ( RHEL5, 64, 72 GB box)

    Simulation Time 21 min

    Max Process Size 15.960 GB

    Max Unknowns 1.52 million

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    Single-Pole-Double-Throw (SPDT) switches are widely used inTransmit/Receive applications. MMIC SPDT switch has been designedusing standard series-shunt configuration . The Non-Linear MMIC demokit contains MESFETs with non-linear models which can be used as basicswitching elements. SPDT switch has one input and two output arms. RFpower is guided into one of the arms by switching ON the required armand switching OFF the other arm.

    Ideally, no power should be detected in the OFF arm. However, due tothe parasitic and coupling effects, RF power leaks into the OFF arm. Theleaked power is grounded by placing a shunt MESFET in ON state asshown in the following figure

    This reduces the power detected in the OFF arm and thus improves the isolation.

    RF-IN

    RF-OUT1

    RF-OUT2

    FET

    RF-IN

    RF-OUT1

    RF-OUT2

    FET

    ON

    ONOFF

    OFF

    MMIC SPDT Switch DesignTechnology-2

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    MMIC SPDT Switch Circuit and EM Cosimulation

    SPDT switch is design first using Ideal lumped elements. RF flows from Source to Drain when Gate is at 0 volt.Hence series FETs have input and output at Source and Drain respectively. Single DC bias is used to connect allON devices and another single DC bias is used to connect all OFF devices. After verifying the basic switchaction, idle components are replaced with MMIC demo-kit components in layout . Schematic circuit with demokit components are generated with option Schematic > Generate/Update Schematic .

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    SPDT + Package EM Cosimulation dataFEM Solver: DM64 ( RHEL5, 64, 72 GB box)

    Simulation Time 1 hour 6 min

    Max Process Size 30.2 GB

    Max Unknowns 2.71 million

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    LTCC LPF Filter

    Low Temperature Co-fired Ceramic (LTCC) is a multi-layer ceramic technology, which processes theability to embed the passive elements, such as resistors, capacitors and inductors into a ceramicinterconnect package while the active elements are mounted in the top layer. Up to 50 layers canbe constructed.

    In the design a 3 pole low pass filter up to 6 GHz has been designed by using spiralinductor and capacitor. The technology used in this example is LTCC. The basiccomponents spiral inductor and capacitor been designed with parameterized value. Filter has been optimize by varying parameters that changes value of L and C.

    Technology-3

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    Microstrip Patch Antenna Design along with Via Transition

    Antenna with LTCC Filter

    Antenna Gain Pattern

    Technology-4

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    QFN Package CharacterizationTechnology-5

    This is QFN package that uses standardpackaging substrate configuration. QFNpackage is chara