Signal processing of an amplitude-modulated and/or phase-modulated high frequency signal

• US 20040046524A1
• Filed: 07/15/2003
• Published: 03/11/2004
• Est. Priority Date: 01/16/2001
• Status: Active Grant

• Current Assignee: Interessengemeinschaft FÜR Runfunkschutzrechte GmbH Schutzrechtsverwertung & Company KG
• Original Assignee: Interessengemeinschaft FÜR Runfunkschutzrechte GmbH Schutzrechtsverwertung & Company KG
• Inventors: Zschunke, Willmut
• Granted Patent: US 7,139,535 B2
• Time in Patent Office: Days
• US Class Current: 318/723
• CPC Class Codes: H04L 27/20 Modulator circuits; Transmitter circuits

Abstract

The invention indicates a method for signal processing of an amplitude-modulated and/or phase-modulated high-frequency signal (RF signal), in which the RF signal is broken down into two signals (FM1 and FM2) by relative phase displacement by an angle +β and −β and the signals are amplified before they are added to form a transmission signal, and to a circuit arrangement in which the pure phase-modulated RF signal is multiplied in a first branch by cos β and in a second branch by sin β and the two signals (FM1, FM2) are obtained by respective summation and subtraction of the multiplied signals.

Claims

1. Method of signal processing of an amplitude-modulated and/or phase-modulated high-frequency signal (RF signal), in which the RF signal is broken down into two signals (FM1 and FM2) by relative phase displacement by an angle of +β

and −

β and

the signals are amplified before they are added to form a transmission signal, characterised in that the phase-modulated RF signal with constant envelope curve is multiplied in a first branch by cos β and

in a second branch by sin β and

the two signals FM1, FM2, are obtained by respective summation and subtraction of the multiplied signals.

2. Method according to claim 1, characterised in that the multiplication by cos β

in the first branch is omitted and the RF signal is applied directly.

3. Method according to claim 1 or 2, characterised in that the RF signal is an orthogonal phase-modulated signal with constant or varying envelope curve.

4. Method according to claim 1, 2 or 3, characterised in that the RF signal is obtained from two amplitude-modulated and phase-modulated input signals (x₁(t), x₂(t)) by quadrature modulation, wherein the individual signals after modulation by a sine and a cosine are added.

5. Method according to one of claims 1, 2 and 3, characterised in that the RF signal is formed from two orthogonal phase-modulated input signals (x₁(t), x₂(t)) which after modulation by a sine or cosine are subtracted from one another.

6. Method according to claim 4 or 5, characterised in that the input signals (x₁(t) and x₂(t)) are scanning values.

7. Method according to one of claims 4 and 6, characterised in that one of the two input signals is zero when the method is used for a pure amplitude-modulated signal.

8. Method according to claim 6 or 7, characterised in that the modulation is carried out on the basis of carrier frequency and that the carrier frequency is a quarter of the scanning frequency.

9. Method according to one of claims 4 to 6 or 8, characterised in that the phase-modulated orthogonal signal which is multiplied by sin β

and/or by cos β

is divided by the envelope curve signal (A(t)) determined from the two input signals (x₁, x₂) by means of amount detection.

10. Method according to claim 6 or 9, characterised in that in the case of approach of the scanning values of the input signals (x₁ and x₂) towards or through zero or when the envelope curve signal (A(t)) goes towards or through zero the received signals (x₁, x₂) are replaced by input signals modified by means of subtraction of adjacent scanning values.

11. Method according to claim 10, characterised in that the calculation of the scanning values of the modified input signals is carried out in a digital signal processor.

12. Method according to claim 10 or 11, characterised in that the scanning values of the input signals and the associated modified input signals are filed in a table and the modified input scanning values are read out of the table as substitute value when a specific predetermined threshold of the amplitude value is formed below.

13. Method according to one of the preceding claims, characterised in that the signals after separate amplification are added to form a common signal and subtracted from one another.

14. Method according to claim 13, characterised in that the upper harmonic waves of the fundamental oscillations of the amplified signal are suppressed by filtering.

15. Method according to one of the preceding claims, characterised in that the modulated RF signal is buffered.

16. Circuit arrangement for carrying out the method according to claim 1, characterised by a signal splitting circuit which splits the RF signals into two signals (FM1 and FM2) and by two downstream non-linear amplifiers (1, 2), the outputs of which are connected with inputs of an adder (3) or a subtracter (11), at the output of which the desired signal can be tapped, wherein in the signal splitting circuit a multiplier (4) is contained in the first branch and multiplies the RF signal by cos β

and a multiplier (5) is present in the second branch and multiplies the RF signal by sin β and

that the inputs of an adder (6) and a subtracter (7) arranged parallel thereto are respectively connected with the outputs of the multipliers (4, 5), the outputs of the adder and subtracter being connected with the non-linear amplifiers (1, 2).

17. Method according to claim 16 in connection with a method according to claim 4, characterised in that the RF input signal is formed from two input signals (x₁(t) and x₂(t)), that provided in the first branch of the first input signal (x₁(t)) is a multiplier, to one input of which the first input signal (x₁(t)) is applied and to the second input of which a sin ω

₀t signal is applied as multiplicant, that the output signal is applied to an input of adder (8), that the second input signal (x₂(t)) in the second branch is applied to one input of a multiplier (4), to the second input of which a cos ω

₀t signal is applied as multiplicant, that the output of the multiplier (4) is connected with the second input of the adder and that the FM signal (A(t) cos(ω

₀t+Φ

(t)) can be tapped at the output, which signal is applied to the input of the downstream adder (6) and subtracter (7), respectively.

18. Circuit arrangement according to claim 16 in connection with performance of the method according to claim 4, characterised in that two input signals are applied to two inputs of a further circuit arrangement and are formed substantially by division of the input signals (x₂(t) and x₁(t)) by the amount value A(t)), that in one branch there is provided a multiplier (5) in which the division signal derived from the input signal (x₂(t)) is multiplied by the multiplicant sinω

₀t and the output of which is connected with the input (+) of a subtracter (8), that in the second branch there is provided a multiplier (4) which multiplies the division signal derived from the input signal (x₁(t)) by the multiplicant cos ω

₀t and the output of which is connected with the second input (−

) of the subtracter (8), and that the RF signal (A(t) sin(ω

₀t+Φ

(t)) can be tapped at the output of the subtracter.

19. Circuit arrangement according to claim 17 and 18, characterised in that the two circuits are coupled together by way of adder (6) and subtracter (7), from the outputs of which the signals (FM1 and FM2) can be tapped.

20. Circuit arrangement according to one of claims 16 to 19, characterised in that the amplifiers (1, 2) for the signals (FM1 and FM2) are push-pull end stages (9, 10, 11) which operate in class C operation, that the input FM signals are two signals which are equal, but differ in sign, and that an output difference signal, which is applied to the respective input of the adder or subtracter, can be tapped at the output of the amplifier.

21. Circuit arrangement according to claim 20, characterised in that the push-pull end stage (9, 10, 11) comprises an output transformer (11) which is coupled with a filter, which suppresses the harmonics of the fundamental oscillation of the amplified signals.

22. Circuit arrangement according to claim 20, characterised in that the push-pull end stage (9, 10, 11) operates in pure switching mode.