Communications: directive radio wave systems and devices (e.g. – With particular circuit
Reexamination Certificate
2000-03-02
2001-08-28
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
With particular circuit
C342S202000, C342S203000
Reexamination Certificate
active
06281835
ABSTRACT:
The invention relates to a modular solid-state radar transmitter, comprising a control unit for the supply of RF steer pulses and logical control signals, a preamplifier, a power splitter for splitting the preamplified steer pulses into N RF input signals, N solid-state amplifier modules and a power combiner for combining the output signals of the amplifier modules authorized by the control signals.
A modular solid-state transmitter of this type is known from patent specification EP-A-0.622.638. In this known transmitter, individual solid-state amplifier modules are, in a manner predefined, switched on and subsequently switched off by means of the logical control signals for generating a transmitter pulse with a desired amplitude modulation.
In the solid-state transmitter according to the invention, the logical control signals are used for enabling all amplifier modules at least substantially simultaneously such that an RF steer pulse can be amplified to yield a transmitter pulse. It however appears that a tapering of the RF steer pulse, applied to restrict the frequency spectrum of the transmitter pulse, is hardly noticeable in the transmitter pulse. The present invention has for its object to restrict the frequency spectrum of the transmitter pulse in an alternative manner by controlling the gain of all amplifier modules with only one control signal and is characterized in that one additional logical control signal is provided that controls all N amplifier modules and that switches during the occurrence of RF steer pulses.
An advantageous embodiment of the invention which can be easily implemented from a hardware point of view is characterized in that an amplifier module comprises a single first amplifier stage to which the additional control signal is connected. In this embodiment, the first amplifier stage is preferably an RF transistor in a grounded base circuit where a collector is connected to a supply voltage.
A very advantageous embodiment of the invention is characterized in that the collector can be connected to the supply voltage through a first switching element and to earth potential through a second switching element and that the additional control signal controls both switching elements at least substantially simultaneously such that the collector is connected to earth potential before the RF steer pulse has ended.
A further advantageous embodiment of the invention in which a tapering of the transmitter pulse is at least substantially independent of a tapering of the additional control signal is characterized in that the collector is furthermore connected to a capacitor, whose capacity value is selected to be such that, in combination with an internal impedance of the switching elements, the supply voltage on the collector has a decay time of 0.1-1 microsecond.
In view of the constant endeavour to take optimal advantage of the entire RF steer pulse, another advantageous embodiment of the invention is characterized in that means are provided for adjusting a time delay for the additional logical control signal, which means may be incorporated in the control unit, preferably in a central position.
An alternative advantageous embodiment of the invention which is also quite simple to implement, is based on a deliberately introduced statistical spread on the switching off of the individual amplifier modules. This embodiment is characterized in that the additional logical control signal is provided with means for adjusting a time delay and that these means are incorporated in at least substantially each amplifier module. A tapering of the transmitter pulse can then simply be obtained by adjusting the amplifier modules with a 0.1-1 microsecond spread on the time delays.
REFERENCES:
patent: 4064464 (1977-12-01), Morse
patent: 5136300 (1992-08-01), Clarke et al.
patent: 5325099 (1994-06-01), Nemit et al.
patent: 5561397 (1996-10-01), Kumar et al.
patent: 5781066 (1998-07-01), Parisi et al.
Mast Ingen Adri
Wieringa Koenraad
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sotomayor John B.
Thales Nederland B.V.
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