Angle measurement device for amplitude monopulse receivers

• US 4,926,184 A
• Filed: 03/16/1988
• Issued: 05/15/1990
• Est. Priority Date: 10/29/1985
• Status: Expired due to Fees

• Current Assignee: Alenia Aeritalia & Selenia SpA (Leonardo S.p.A.)
• Original Assignee: Selenia-Industrie Elettroniche Associate SPA (Leonardo S.p.A.)
• Inventors: Jacovitti, Giovanni, Galati, Gaspare
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US07/170,055
• Time in Patent Office: 790 Days
• Field of Search: 342/37, 342/149, 342/152, 342/427
• US Class Current: 342/149
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing

Abstract

Device for angle measurement for inclusion within a monopulse amplitude comparison radar receiver for particular application within secondary radars. In essence it consists of a log (Σ) signal comparator (9) against a detection threshold, which is meant to enable further processing; of two-analog-numerical converters (10, 11), a codes (12), receiving outputs Σ and Δ from converters above, which provides the calculation of target azimuth.

Claims

1. An angle-measurement device in an amplitude-modulated monopulse radar receiver, comprising:

two logarithmic amplifiers connected to an antenna system and responsive to two antenna-pattern signals in the form of a sum and of a difference denoted as a sigma signal and a delta signal, respectively, for generating log sigma and log delta signals;

respective hard limiters connected to outputs of said logarithmic amplifiers and having respective outputs representing the phases of said sigma and delta signals;

a 90°

phase shifter connected to an output of one of said hard limiters to effect a 90°

phase shift of the signal outputted thereby;

a phase detector connected to an output of said 90°

phase shifter and the output of the other of said hard limiters for outputting a signal representing the cosine of the phase difference between said sigma and delta signals;

a first analog-to-digital converter connected to an output of said phase detector for digitalizing said cosine;

a subtractor connected to said outputs of said logarithmic amplifiers for outputting a signal representing the logarithm of the quotient of said sigma and delta signals;

a second analog-to-digital converter connected to an output of said subtractor for digitalizing said signal representing the logarithm of said quotient;

a first comparator connected with the output of one of said logarithmic amplifiers for comparing the respective log signal with a detection threshold to provide an enabling signal;

a second comparator connected with the output of said subtractor for comparing the logarithm of the quotient with another threshold to output a signal representing the existence of a predetermined condition; and

a third comparator connected with the output of said phase detector and having a zero input for generating a signal representing the sign of the cosine;

a decoder connected to said first and second analog-to-digital converters and to said first, second and third comparators and enabled by said enabling signal to provide angle measurement output selectively in accordance with the function;

space="preserve" listing-type="equation">θ

=SK.sub.m b.sup.-z (

     1),

and

space="preserve" listing-type="equation">θ

=CK.sub.m b.sup.-z (

     2),

where

θ

is the measured azimuth angle,

b is the logarithm base,

z is the logarithm of the quotient,

S is the sign of the cosine,

C is the cosine, and

K_m is a constant system parameter,

in accordance with the output of said second comparator.

2. An angle-measurement device in an amplitude-modulated monopulse radar receiver, comprising:

two logarithmic amplifiers connected to an antenna system and responsive to two antenna-pattern signals in the form of a sum and of a difference denoted as a sigma signal and a delta signal, respectively, for generating log sigma and log delta signals;

respective hard limiters connected to outputs of said logarithmic amplifiers and having respective outputs representing the phases of said sigma and delta signals;

a 90°

phase shifter connected to an output of one of said hard limiters to effect a 90°

phase shift of the signal outputted thereby;

a phase detector connected to an output of said 90°

phase shifter and the output of the other of said hard limiters for outputting a signal representing the cosine of the phase difference between said sigma and delta signals;

a first analog-to-digital converter connected to an output of said phase detector for digitalizing said cosine;

a subtractor connected to said outputs of said logarithmic amplifiers for outputting a signal representing the logarithm of the quotient of said sigma and delta signals;

a second analog-to-digital converter connected to an output of said subtractor for digitalizing said signal representing the logarithm of said quotient;

a comparator connected with the output of one of said logarithmic amplifiers for comparing the respective log signal with a detection threshold to provide an enabling signal; and

a decoder connected to said first and second analog-to-digital converters and to said comparator and enabled by said enabling signal to provide angle measurement output selectively in accordance with the function;

space="preserve" listing-type="equation">θ

=CK.sub.m b.sup.-z,

where

θ

is the measured azimuth angle,

b is the logarithm base,

z is the logarithm of the quotient,

C is the cosine, and

K_m is a constant system parameter.