Wave transmission lines and networks – Coupling networks – Delay lines including a lumped parameter
Patent
1997-05-30
1998-10-20
Pascal, Robert J.
Wave transmission lines and networks
Coupling networks
Delay lines including a lumped parameter
333 81R, H03H 720
Patent
active
058252614
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
PRIOR ART
The present invention relates to a phase shifting and attenuating device for processing electric signals in the fields of radio communication, telecommunications, radar, sonar and signal processing.
In a signal processing or transmission chain the device transmits, at its output, each spectral component of the signal applied to its input, after imparting thereto a phase rotation or shift .phi. and an attenuation .alpha. defined by digital control signals applied to the device.
The phase shifting and attenuating device, also known as a weighting device, ensures, within an extensive frequency band, the generation of a wave the phases and amplitudes of the spectral components of which, in relation to those of a wave that is applied thereto, are adjustable and uniquely defined for the entire operating frequency band.
In practice, the attenuating operation is not selective, that is to say it can be carried out without modifying the commands over an extensive frequency band.
On the other hand, a phase shifting operation is necessarily selective, and, with the usual passive electric circuits, the commands have to be modified as a function of frequency.
To produce a passive device, ensuring the phase shifting function over an extensive frequency band, it is necessary to implement special circuits.
Present weighting devices fall into two categories.
In a first category, the weighting device is passive and separates the phase shifting and attenuation functions. It can, for example, be constituted by the use of sections of lines of variable lengths switched according to the frequency in order to obtain the desired phase shift, or by phase shifting circuits formed by assembling capacitors, inductors and resistors adjusted according to the frequency, in order to obtain the desired phase shift, and by an attenuator.
The devices in this first category are known as narrow band devices owing to the fact that an adjustment of the phase shift is valid only over a small extent of the frequency range. In addition, they necessitate the adjustment of the values of passive elements, often obtained by switching elements of different values.
In a second category, the weighting device is active, and can combine the phase shifting function and the attenuating function. It then uses either balanced modulators or frequency changers, or equivalent electronic systems. These devices introduce considerable electric noise, which makes them impossible to use when it is necessary to process weak signals; in addition, they are sensitive to the effects of intermodulation in the presence of signals of great amplitude such as, for example, interference signals in reception systems.
SUMMARY OF THE INVENTION
The present invention aims to provide a weighting device that remedies the aforementioned drawbacks, particularly by improving, by comparison with existing systems, the pass band, performance with regard to thermal noise and performance with regard to intermodulation defects, while, at the same time, cutting the manufacturing cost thanks to the use of components that are relatively simple and inexpensive.
For this purpose, a weighting device generating, from an input signal, an output signal, the spectral components of which are phase shifted and attenuated by given amounts in relation to the input signal, is characterised in that it includes:
A matching circuit which receives the input signal at its input in such a way as to deliver, at two outputs, output 1 and output 2, of the matching circuit, two output signals that are images of the input signal, in phase or in phase opposition with the input signal and having equal amplitudes that are constantly related to that of the input signal;
Two transfer channels, called transfer channel 1 and transfer channel 2, transfer channel 1 receiving the signal produced by output 1 of the matching circuit and transfer channel 2 receiving the signal produced by output 2 of the matching circuit.
Each of the channels includes: thereto, changes or does not change, t
REFERENCES:
patent: 4558291 (1985-12-01), Nichols
patent: 4581595 (1986-04-01), Silagi
patent: 4806888 (1989-02-01), Salvage et al.
patent: 4977382 (1990-12-01), Podell et al.
Budzyn Ludomir A.
Casella Anthony J.
Compagnie D'Etudes, de Realisations et D'Installations de System
Ham Seungsook
Hespos Gerald E.
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