Phase shifted transmitter architecture for communication systems

• US 20040101065A1
• Filed: 11/21/2002
• Published: 05/27/2004
• Est. Priority Date: 11/21/2002
• Status: Active Grant

• Current Assignee: C. Andre T. Salama, Sotoudeh Hamedi Hagh
• Original Assignee: C. Andre T. Salama, Sotoudeh Hamedi Hagh
• Inventors: Hagh, Sotoudeh Hamedi, Salama, C. Andre T.
• Granted Patent: US 7,260,157 B2
• Time in Patent Office: Days
• US Class Current: 375/297
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H04L 27/362 Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence

Abstract

The phase shifted (PS) transmitter provides substantially linear amplification from two non-linear amplifiers by decomposing the original signal into two constant envelope signals with varying phases. The generation of the two constant envelope signals does not require the use of a signal component separator (SCS) or a reference signal generator. The phase shifted transmitter generates directly the required constant envelope, varying phase signals. This eliminates stringent requirements on the circuitry and allows the use of non-linear highly efficient power amplifiers in the transmitter. When the two above mentioned signals are combined, they constructively and destructively interfere to re-form an amplified form of the original signal, which is to be transmitted via an antenna.

Claims

1. A method of improving the linearity and efficiency of a communication system transmitter, comprising the steps of:

(a) utilizing a baseband operation to generate at least first and second voltages which are in conformity with an input transmission signal;

(b) using said first and second voltages to generate respective first and second component signals having substantially constant envelopes and varying phases;

(c) amplifying said first and second component signals separately; and

(d) combining said first and second component signals following amplification to produce an output signal.

2. The method of claim 1, wherein step (b) further comprises modifying appropriately said first and second voltages to generate the correct said first and second component signals.

3. The method of claim 1, wherein step (b) further comprises:

(i) using at least one LC network, consisting of at least one inductor and one capacitor, implementing a quarter-wavelength transmission line; and

(ii) cascading an even number of said quarter-wavelength transmission lines to implement a phase shifter.

4. The method of claim 1, wherein step (c) further comprises connecting at least one switching power transistor to an odd number of said LC networks to match a power amplifier to an antenna and combine said first and second component signals following amplification.

5. The method of claim 1, wherein the amplification of step (c) is implemented by using high efficiency non-linear power amplifiers.

6. The method of claim 1, wherein said output signal of step (d) could be transmitted through an antenna.

7. A system for improving the linearity and efficiency of a communication system transmitter, comprising of:

(a) means to generate at least first and second voltages which are in conformity with an input transmission signal;

(b) means to utilize said first and second voltages to generate respective first and second component signals having substantially constant envelopes and varying phases;

(c) means to amplify said first and second component signals separately; and

(d) means to combine said first and second component signals following amplification to produce an output signal.

8. The system of claim 7, wherein step (b) further comprises means to modify appropriately said first and second voltages to generate the correct said first and second component signals.

9. The system of claim 7, wherein the amplification of step (c) is implemented by using high efficiency non-linear power amplifiers.

10. The system of claim 7, wherein said output signal of step (d) could be transmitted through an antenna.

11. A method of increasing the frequency bandwidth, for which impedance matching is achieved, comprising the steps of:

(a) using at least one LC network, consisting of at least one inductor and one capacitor, implementing a quarter-wavelength transmission line;

(b) using 2K+1 cascades of said LC networks where K is an integer ≧

1; and

(c) decreasing reflection coefficients between two adjacent transformed impedances in the cascaded LC networks compared to a single LC network.