Method and apparatus for multiple band transmission

• US 6,389,269 B1
• Filed: 06/15/2000
• Issued: 05/14/2002
• Est. Priority Date: 06/15/2000
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Xiang, Li, Midlock, Eric, Nanni, Peter
• Primary Examiner(s): Chang, Vivian
• Assistant Examiner(s): Lee, John J
• Application Number:
  US09/594,395
• Time in Patent Office: 698 Days
• Field of Search: 455/127, 455/126, 455/103, 455/552, 455/553, 455/93, 455/89, 455/39, 455/114, 333/124, 333/125, 333/126, 333/127, 333/32
• US Class Current: 455/93
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/006 using switches for selecting the desired band H04B1/0057 takes precedence
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

A method and apparatus for transmitting in multiple radio frequency (RF) bands from a single device is described. The device includes a transmitter (128) for transmitting RF communication signals. The transmitter is comprised of a power amplifier (200) for amplifying the RF communication signal in either a first RF band or a second RF band. The transmitter has a complex transformer (202) for partially transforming the impedance of the RF communication signal in a first RF band, and completely transforming the impedance of the RF communication signal to the characteristic impedance in a second RF band. The transmitter also includes a first path (204) for transmitting the RF communication signal in the first RF band and a second path (206) for transmitting the RF communication signal in the second RF band. The first path completes the impedance transformation of the RF communication signal when the system is operating in the first RF band and the second path operates at the characteristic impedance when the system is operating in the second RF band.

Claims

1. A transmitter for transmitting a radio frequency (RF) communication signal in a first RF band and in a second RF band comprising:

A power amplifier (PA), having a PA output, said PA for amplifying said RF communication signal, in said first RF band and in said second RF band;

a first transformer comprising a first node, a second node, a first transmission line coupled between said PA output and said first node, and a first parallel capacitor coupled between said first node and said second node, said first transformer for fully transforming the impedance of said RF communication signal in said second RF band to a first fully transformed impedance at said first node, and said first transformer for partially transforming the impedance of said second RF communication signal in said first RF band to a second partially transformed impedance at said first node;

a first path having a third node, a fourth node and a fifth node, a second transmission line coupled between said first node and said third node, a second parallel capacitor coupled between said third node and said second node, a third transmission line coupled between said third node and said fourth node, a third parallel capacitor coupled between said fourth node and said second node, and a first filter coupled between said fourth node and said fifth node for passing only said communication signal in said first RF band; and

a second path having a sixth node, a seventh node, a third filter coupled between said first node and said sixth node, a fourth transmission line coupled between said sixth node and said seventh node, a fourth parallel capacitor coupled between said seventh node and said second node and a second filter coupled between said seventh node and said fifth node, for passing only said second RF communication in said second RF band.

2. The transmitter as in claim 1, wherein said first filter is a low pass filter,

wherein said second filter is a low pass filter, and

wherein said third filter is an LC tank filter.

3. The transmitter as in claim 1, wherein said first transmission line has a first impedance, said second transmission line has a second impedance, said third transmission line has a third impedance, and said fourth transmission line has a fourth impedance.

4. The transmitter as in claim 1, wherein said first RF band is in accordance with the Advanced Mobile Phone System (AMPS) and the time division multiple access (TDMA) 800 MHz system, and said second RF band is in accordance with said TDMA 1900 MHz system.

5. The transmitter as in claim 2, wherein said LC tank filter further comprises a fifth parallel capacitor and an inductor in parallel coupled in series between said first node and said sixth node,

wherein said fifth parallel capacitor is series resonant when said RF communication signal is in said second RF band,

wherein said LC tank filter forms an open circuit when said RF communication signal is in said first RF band, and

wherein said LC tank filter has an effective parallel resistance at least ten times greater than second first partially transformed impedance when said communication signal is in said first RF band.

6. The transmitter as in claim 1, wherein said second node is a common ground.

7. The transmitter as in claim 1, wherein said first path transforms said second impedance to said third impedance between said first node and said fourth node.

8. The transmitter as in claim 1, wherein said third parallel capacitor is series resonant when said RF communication signal is in said second RF band.

9. A method for transmitting radio frequency (RF) communication signals in a first RF band and a second RF band comprising the steps of:

amplifying said RF communication signal with a power amplifier;

transforming the impedance of said RF communication signal partially to a first partially transformed impedance when said RF communication signal is in a first RF band;

transmitting said first transformed RF communication signal having a frequency within said first RF band through a first transmission path;

transforming the impedance of said RF communication signal completely to a second fully transformed impedance when said RF communication signal is in said second band; and

transmitting said second transformed RF communication signal having a frequency within said second band through a second transmission path.

10. The method of claim 9 further comprising the step of amplifying said RF communication signal in said first and said second RF band with only one said PA.

11. The method of claim 9 further comprising the step of completing the impedance transformation of said first partially transformed impedance of said RF communication signal to said second impedance with said first transmission path.

12. The method of claim 9 further comprising the step of passing said RF communication signal through said second transmission path when said RF communication signal is in said second RF band with an LC tank filter, and creating a parallel resonant circuit with said LC tank filter when said RF communication filter is in said first RF band preventing said RF communication signal from passing through said second transmission path.

13. The method of claim 9 further comprising the step of generating an effective parallel resistance with said LC tank filter such that said parallel resistance is at least ten times greater than said first partially transformed impedance when said communication signal is in said first RF band.