Transmitter for transmitting signals over radio channels and method for transmitting signals over radio channels

• US 7,423,958 B2
• Filed: 12/16/2000
• Issued: 09/09/2008
• Est. Priority Date: 12/23/1999
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Hentati, Nabil, Lochau, Mirko, Schrader, Marc, Harms, Lars
• Primary Examiner(s): Orgad; Edan
• Assistant Examiner(s): HO, CHUONG T
• Application Number:
  US10/168,894
• Publication Number:
  US 20030156657A1
• Time in Patent Office: 2,824 Days
• Field of Search: 370/216, 370/242, 370/249, 370/332, 370/206, 370/204, 370/205, 375/297, 375/267, 375/295, 375/296, 375/298, 375/308, 375/260, 375/261, 330/151, 330/149, 455/114.3
• US Class Current: 370/204
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A transmitter for sending signals over wireless channels and a method of sending signals over wireless channels are described. The transmitter and the method are used to determine a transfer characteristic of an amplifier (8) in the transmitter. Symbols in the OFDM signals to be transmitted are multiplied by test signals at predefined points in time to compare the OFDM symbol, which has been multiplied by the test signal, upstream and downstream from the amplifier to determine the transfer characteristic of the amplifier (8). This transfer characteristic of the amplifier (8) is used by a predistorter (4) to predistort the signals according to this transfer characteristic. The test signal, which is generated by a signal generator (13), is input into a symbol of the fast information channel, the test signal having an amplitude which drives the multiplied symbol into the saturation range of the amplifier (8) with regard to its amplitude.

Claims

1. A transmitter for sending signals over wireless channels, comprising:

a modulator for modulating signals to be sent and for distributing modulated signals among a plurality of subcarriers;

a predistorter for predistorting the signals distributed among the plurality of subcarriers;

a signal generator for generating a test signal;

a multiplier for multiplying the test signal by at least one of the distributed signals and the predistorted signals at predefined time intervals;

a mixer for converting at least one of the multiplied signals and the predistorted signals from a baseband into an intermediate frequency;

an amplifier for amplifying the converted signals;

an antenna for sending a first portion of the amplified signals;

a mixer for mixing a second portion of the amplified signals down from the intermediate frequency to the baseband; and

a measuring module for comparing the mixed-down signals with the at least one of the multiplied signals and the predistorted signals to determine transfer properties of the amplifier and to notify the predistorter of the transfer properties of the amplifier, wherein the measuring module is configured to compare a test signal in the mixed-down signals with a test signal in the at least one of the multiplied signals and the predistorted signals to obtain the transfer properties of the amplifier, and wherein the predistorter is configured to predistort the signals distributed among the various subcarriers according to the transfer properties of the amplifier.

2. The transmitter according to claim 1, wherein the multiplier multiplies the test signal upstream from the predistorter by the distributed signals at the predefined time intervals.

3. The transmitter according to claim 1, wherein the modulator performs a differential phase modulation.

4. The transmitter according to claim 3, wherein the modulator performs a differential quadrature phase shift keying.

5. The transmitter according to claim 1, wherein the signal generator generates the test signal as a d.c. voltage signal in the predefined intervals, an amplitude of the d.c. voltage signal driving the amplifier into saturation.

6. The transmitter according to claim 5, wherein the multiplier multiplies the test signal by a predetermined symbol in the at least one of the distributed signals and the predistorted signals.

7. A method of sending signals over wireless channels, comprising:

modulating the signals to be sent;

distributing the modulated signals among subcarriers;

predistorting the distributed signals according to transfer properties of an amplifier;

converting the predistorted signals from a baseband into an intermediate frequency;

amplifying the converted signals;

sending a first portion of the amplified signals over the wireless channels;

converting a second portion of the amplified signals from the intermediate frequency to the baseband;

comparing the predistorted signals with the signals converted to the baseband to determine the transfer properties of the amplifier; and

sending information regarding the transfer properties of the amplifier to a predistorter;

wherein in determining the transfer properties of the amplifier, test signals are generated and multiplied by at least one of the distributed signals and the predistorted signals, and a test signal in at least one of the multiplied signals and the predistorted signals is compared with a test signal of the signals amplified and converted to the baseband.

8. The method according to claim 7, wherein the test signals are multiplied by the distributed signals upstream from the predistorter.

9. The method according to claim 7, wherein the test signals include a test signal having an amplitude such that the amplifier is at least fully driven by the test signal.

10. The method according to claim 9, wherein the test signal is multiplied by a fast information channel symbol.