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Variable impedance load for a variable gain radio frequency amplifier

A technology of impedance load and amplifier, which is applied in the field of wireless communication devices, can solve the problems of reducing filter gain flatness, influence, and degradation of in-band and out-of-band characteristics of transmitting filters, etc.

Inactive Publication Date: 2010-05-26
QUALCOMM INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Impedance mismatch also adversely affects the operation of the transmit filter 14, resulting in degradation of the transmit filter's in-band and out-of-band characteristics
This mismatch can lead to increased filter insertion loss, reduced filter gain flatness, and degraded out-of-band filter rejection

Method used

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  • Variable impedance load for a variable gain radio frequency amplifier
  • Variable impedance load for a variable gain radio frequency amplifier
  • Variable impedance load for a variable gain radio frequency amplifier

Examples

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Embodiment Construction

[0022] The present invention provides a variable impedance load whose input impedance varies according to the gain of a variable gain RF driver amplifier.

[0023] An exemplary embodiment of the present invention is shown in system 100 as figure 2 The functional block diagram is shown. RF driver amplifier 102 has a gain control input. In an exemplary embodiment, RF driver amplifier 102 has a variable gain of approximately 20-40 decibels (dB). Those skilled in the art will appreciate that the output impedance of RF driver amplifier 102 varies significantly as a function of the gain of the amplifier. Specifically, as the gain of the amplifier increases, the output current of the RF driver amplifier 102 increases, while the output impedance decreases. Conversely, as the gain of the RF driver amplifier 102 decreases, the output current of the RF driver amplifier decreases and the output impedance increases. Thus, output impedance varies inversely with gain (and output current...

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Abstract

A variable impedance load (104) is provided at the output of a radio frequency (RF) driver amplifier (102) having a variable gain. In an exemplary embodiment, the variable load (104) comprises a resistor (R) in series with a semiconductor device (M1). The semiconductor device (M1) has an impedance level determined by a drive current. The value of the drive current is related to the gain of the RFdriver amplifier (102).

Description

technical field [0001] The present invention is directed generally to wireless communication devices, and more particularly to variable impedance loads for variable gain radio frequency amplifiers used in the output stages of wireless communication devices. Background technique [0002] Wireless communication devices are widely used in applications such as wireless telephony. The output stage of a wireless communication device includes a radio frequency (RF) amplifier. This is true for most wireless communication devices, regardless of the modulation form, such as AM, FM, etc. A typical output stage 10 for a wireless communication device is shown in figure 1 , and includes RF driver amplifier 12, transmit filter 14 and RF power amplifier 16. The output port of RF driver amplifier 12 is coupled to the input port of transmit filter 14 . Similarly, the output port of transmit filter 14 is coupled to the input port of RF power amplifier 16 . [0003] The input 18 of the RF ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03F1/56H03G3/30H03H11/30
CPCH03H11/30H03G3/3042
Inventor K·巴尼特
Owner QUALCOMM INC