參數(shù)資料
型號: MRFIC1859
廠商: Motorola, Inc.
英文描述: Dual-Band GSM 3.6V Integrated RF Power Amplifier(GSM 3.6V集成式射頻功放)
中文描述: 雙頻GSM 3.6V的集成RF功率放大器(手機3.6V的集成式射頻功放)
文件頁數(shù): 12/15頁
文件大?。?/td> 180K
代理商: MRFIC1859
MRFIC1859
12
MOTOROLA WIRELESS SEMICONDUCTOR
SOLUTIONS – RF AND IF DEVICE DATA
PIN FUNCTION DESCRIPTION
(continued)
Pin No.
Functionality
Description
I/O
Symbol
32
VSS
O
Negative Voltage
A buffer amplifier is designed to produce the required negative voltage, based on
RF signal amplification with a two stages wide band amplifier and rectification of the
resulting signal. An external zener diode is used to regulate this voltage and
provide to the gates a stabilized biasing voltage. VSS is also used to switch off the
unused amplifier. Refer to Bias Pins 1, 18 and 15, 24.
Exposed
Pad
Gnd
I
Main Gnd
The bottom pad of the TQFP–32EP package is used for electrical/RF grounding
and thermal dissipation. The PCB pattern where it fits has to be tailored for good
ground and thermal continuity (with many ground via holes).
Tuning Methodology
The following section gives the user some guidelines and
hints to tune and optimize the MRFIC1859 operation inside
their own radio PCB. First of all, one must keep in mind that
negative and positive voltage generation is based on RF
carrier rectification. This means that RF input signal must
always be present when running the part as a standalone
solution. Therefore, in order to ease the tuning phase, it is
recommended to apply the negative voltage externally in
order to avoid any damage to the large RF MESFET
transistors. This is particularly true if one uses the complete
application with MC33170 (product of On Semiconductor) as
control IC to do the optimization. In that case, both negative
and positive voltage should be provided externally.
The RF decoupling capacitors have been selected as 47
pF for GSM band (C17, C14, C22, C9. C1, and C8) and 22 pF
or 12 pF for DCS band (C10, C15, and C13). But those can
be optimized depending on their size and source, for
example 12 pF were used at some places for DCS to provide
better decoupling of the harmonics too, thus providing some
extra performance.
The recommended tuning procedure consists of several
steps that need to be performed in sequential order. Several
interations can be performed if appropriate. Due to low
interaction between line–ups, each band can be tuned
independently.
Optimize the buffer operation using D1B (T8 line) and D2B
matching (L3 inductor). Simultaneously, tune GSM or DCS
input matching using L1, C21 or L2, T10, respectively.
Check the margin on Pin to generate VSS and VP (those
voltages should still meet their specification with a 5.0 dB
reduction in Pin). A small shunt capacitor can be placed on
VP to maximize that voltage.
Optimize RF line up linear gain using D1G, D2G matching
(T9 line) or D1D, D2D, G2D matching (T7 line, C8) for GSM
or DCS line–up, respectively. The goal is to maximize and
center small signal gain. Pin has to be reduced for this
exercise, hence the negative voltage needs to be applied
externally. A broad band measurement is helpful to
visualize the frequency response. Linear gain should peak
at around 40 dB for GSM and 32 dB for DCS. The input
matching has to be checked again and eventually refined
during this step.
Optimize output matching using T4, C3, T1, C4 and T2 for
GSM or T6, C2, T5, C6, T3 for DCS, respectively. Those
elements set the Pout/PAE trade–off and harmonics
rejection performance.
Finally, one can iterate some of the above steps to fine tune
RF behavior and also to find the best configuration for
Cross–Talk and Harmonics content reduction. For
example, D2B inductor L3 and VSS decoupling capacitor
C11 have a small influence on the GSM second harmonic
leaking through the DCS output.
The nominal impedance seen from the IPA package pins
have been measured on the demoboard (after removing the
MRFIC1859) and are listed in the following table. They can
be taken as a starting point for the optimization. Also this
gives the equivalent lumped element if one uses a lumped
element instead of microstrip line.
Impedance on the different GSM I/Os:
(expressed in
at
900 MHz)
– InG = 16.2 + j83.5
– OutG = 1.9 – j2.3
– D2G = close to 0 since decoupled as short as possible
– D1G = 1 + j19.8 (3.5 nH)
– D1B = 1.2 + j28.7 (5.0 nH)
– D2B = infinite since 56 nH behaves as choke
Impedance on the different DCS I/Os:
(expressed in
at
1750 MHz)
– InD = 12.5 + j36.5
– OutD = 3.6 – j4.4
– D2D = close to 0 since decoupled as short as possible
– G2D = 0.9 + j6.8 (0.64 nH)
– D1D = 1.1 + j20.8 (1.9 nH)
– D1B = 8.8 + j84.7 (7.6 nH)
– D2B = infinite since 56 nH behaves as choke
One should note that except for RFin/RFout impedance, all
others should be ”in theory” pure reactive shunt elements.
The fact that their resistive part is not zero is linked to the
finite quality factor of the equivalent inductor and also to the
limited accuracy of the measurement (when close to the
Smith chart border).
Control Considerations
The MRFIC1859 application uses drain control technique
developed for our generations of GaAs IPAs. This method
relies on the fact that for an RF power amplifier operating in
saturation mode, the RF output power is proportional to the
square of the Amplifier drain voltage: Pout (Watt) = k * VD (V)
* VD (V).
A dedicated control IC MC33170 has been designed to
manage all those control, biasing and band selection
functions. When the emitting order is sent (TxEn = High), the
MC33170 activates the power supply VDbuf of the negative
voltage generator NVG (VDbuf = Vbat), involving the presence
of Vneg as well as a positive VP of about 9.0 V. Once Vneg
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