Dual space fed parallel plate lens antenna beamforming system

• US 4,595,926 A
• Filed: 12/01/1983
• Issued: 06/17/1986
• Est. Priority Date: 12/01/1983
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Kobus, Joseph P., Ringer, Kenneth A.
• Primary Examiner(s): Blum, Theodore M.
• Assistant Examiner(s): Issing, Gregory C.
• Application Number:
  US06/557,014
• Time in Patent Office: 929 Days
• Field of Search: 343/427, 343/371, 343/374, 343/376, 343/754, 343/756, 343/368, 343/777, 343/778, 343/911 R
• US Class Current: 342/368
• CPC Class Codes: H01Q 21/0031 Parallel-plate fed arrays; Lens-fed arrays multibeam arrays H01Q25/008
• CPC Class Codes: H01Q 25/02 providing sum and difference patterns H01Q25/04 takes precedence
• CPC Class Codes: H01Q 3/38 the phase-shifters being digital

Abstract

A beamforming system for a linear phased array antenna system which can besed in a monopulse transceiver, comprising a pair of series connected parallel plate constrained unfocused lenses which provide a suitable amplitude taper for the linear array to yield a low sidelobe radiation pattern. Digital phase shifters are used for beam steering purposes and the unfocused lenses decorrelate the quantization errors caused by the use of such phase shifters.

Claims

1. A beamforming system for a linear phased array of antenna radiators, comprising:

first and second series connected parallel plate constrained unfocused lenses, each of said lenses including a pair of parallel plates in the form of isosceles trapezoids having inputs along the shorter parallel ends and outputs along the longer parallel ends and a spacing between said parallel plates of less than one half a wavelength at the highest operating frequency, the first of said lenses being smaller than the second of said lenses, said first lens having a single input and a plurality of output ports, said second lens having a like plurality of input ports said single input port being arranged to space feed said first lens output ports, said input ports of said second lens forming a linear array for space feeding the output ports of said second lens and the radiators of said array, an interlens coupling system including a first plurality of waveguides connecting said output ports of said first lens to said input ports of said second lens including a phase shifter and a circulator in each of said waveguides, and wherein said lenses apply a desired amplitude distribution to said linear phased array whereby a low sidelobe antenna pattern will result.

2. The system of claim 1 wherein the sloping non-parallel sides of said lenses are lined with microwave absorbing material, and including a second plurality of waveguides connecting the outputs of the second of said lenses to said radiators.

3. The system of claim 2 wherein said first plurality of waveguides are double ridged H-plane waveguides, and a second plurality of double ridged H-plane waveguides connect the output ports of said second lens to the radiators of said linear phased array antenna, each of said second waveguides including a digital phase shifter therein for steering the beam of said antenna.

4. The system of claim 3 wherein the ridges of said first double ridged waveguides gradually taper into the parallel plates of said first and second lenses to form a gradual transition between said waveguides and said lenses.

5. A monopulse transceiver comprising, a transmitter connected to the single input of a small, unfocused, parallel plate constrained transmit lens, said transmit lens having eight outputs, means to connect said eight outputs to the eight inputs. of a larger, unfocused, parallel plate constrained lens via a waveguide system including sectoral horns and H-plane double ridged waveguides with phase shifters and circulators in each of said waveguides, a linear phased array of radiators connected to the output ports of said larger lens via waveguides which comprise beam steering phase shifters, said circulators designed to direct received signals to a receiver comprising a sum and difference manifold, said receiver comprising eight limiters and eight low noise amplifiers for receiving signals from said eight circulators, power dividers connected to the outputs of said low noise amplifiers, said power dividers splitting the received signals between a sum channel and a difference channel, said sum channel comprising eight phase shifters connected to one output of each of said power dividers, the outputs of said last-named phase shifters being applied to the eight input ports of a receive small lens which is identical to said small transmit lens, the single output of said small receive lens being connected through a variable attenuator to a sum channel down converter wherein said sum channel signals are converted to an intermediate frequency, and wherein said difference channel comprises eight phase shifters connected to the other of the outputs of said power dividers with variable attenuators connected to each of said last-named shifters, the outputs of said eight attenuators being combined by means of six split-tee power dividers and a 180 degree hybrid to form a difference signal which is applied to a difference channel down converter to form the difference signal intermediate frequency.