Matching network for switchable segmented ultrasonic transducers

• US 4,181,864 A
• Filed: 06/22/1978
• Issued: 01/01/1980
• Est. Priority Date: 06/22/1978
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Etzold, Karl-Friedrich
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/917,890
• Time in Patent Office: 558 Days
• Field of Search: 310/314, 310/316, 310/317, 310/319, 310/366
• US Class Current: 310/314
• CPC Class Codes: B06B 1/0207 Driving circuits specially adapted for particular applications, see the relevant subclass, e.g. G01; circuits for steering transducer arrays G10K11/34; basic circuits H03
• CPC Class Codes: B06B 2201/20 Application to multi-element transducer
• CPC Class Codes: B06B 2201/55 Piezoelectric transducer

Abstract

Special low inductance switchable coupling means are provided to permit selective matching of the various segments of the ultrasonic transducer.

Claims

1. In combination:

(a) an ultrasonic transducer unit having a given operating frequency bandwidth, said transducer unit including a piezoelectric medium having a common electrode on one side thereof and segmented first and second electrodes on the other side thereof, a first area of said transducer unit defined by said first electrode and said common electrode exhibiting a first clamped capacitance and first acoustic impedance over said given operating frequency bandwidth and a second area of said transducer unit defined by said second electrode and said common electrode exhibiting a second clamped capacitance and a second acoustic impedance over said given operating bandwidth,

(b) a first matching network effective for matching solely said first acoustic impedance to a predetermined electrical impedance over said given frequency operating bandwidth only when said first matching network is coupled therebetween,

(c) a second matching network for matching said first and second acoustic impedances in parallel to said predetermined electrical impedance over said given frequency operating bandwidth only when said second matching network is coupled therebetween, and

(d) switchable coupling means for selectively rendering effective said first matching network, or, alternatively, said second matching network without ever introducing an inductance sufficient to resonate with or total capacitance equal to the sum of said first and second clamped capacitances at a frequency within said operating frequency bandwidth;

wherein said segmented first and second electrodes comprise a center-electrode surrounded by an annular electrode, said first area of said transducer unit exhibiting a relatively small first clamped capacitance and a relatively high first acoustic impedance over said given operating frequency bandwidth compared to the respective sizes of said second capacitance and second acoustic impedance of said second area;

wherein said switchable coupling means includes first coupling means connecting said center electrode solely to one end of said first matching network, second coupling means connecting said annular electrode solely to one end of said second matching network, a low-inductance slidable first switch for selectively bridging said center and annular electrodes, and a double-throw second switch for selectively connecting solely the other end of either the first matching network or alternatively the second matching network to said predetermined electrical impedance, and

wherein said first switch comprises a slidable electrically-conducting member including first and second spaced contacts, said first switch further including means for situating said member so that both said first and second contacts engage said first switch or for alternatively situating said member so that said first contacts engage said center electrode and said second contacts engage said annular electrode in a second switch position of said first switch.

2. In combination:

(a) an ultrasonic transducer unit having a given operating frequency bandwidth, said transducer unit including a piezoelectric medium having a common electrode on one side thereof and segmented first and second electrodes on the other side thereof, a first area of said transducer unit defined by said first electrode and said common electrode exhibiting a first clamped capacitance and first acoustic impedance over said given operating frequency bandwidth and a second area of said transducer unit defined by said second electrode and said common electrode exhibiting a second clamped capacitance and a second acoustic impedance over said given operating bandwidth,

(b) a first matching network effective for matching solely said first acoustic impedance to a predetermined electrical impedance over said given frequency operating bandwidth only when said first matching network is coupled therebetween,

(c) a second matching network for matching said first and second acoustic impedances in parallel to said predetermined electrical impedance over said given frequency operating bandwidth only when said second matching network is coupled therebetween, and

(d) switchable coupling means for selectively rendering effective said first matching network, or, alternatively, said second matching network without ever introducing an inductance equal to the sum of said first and second clamped capacitances at a frequency within said operating frequency bandwidth;

wherein said segmented first and second electrodes comprise a center-electrode surrounded by an annular electrode, said first area of said transducer unit exhibiting a relatively small first clamped capacitance and a relatively high first acoustic impedance over said given operating frequency bandwidth compared to the respective sizes of said second capacitance and second acoustic impedance of said second area, and

wherein said center electrode is coupled solely to one end of said first matching network and wherein said second matching network comprises both said first matching network and a third matching network, said annular electrode being connected to one end of said third matching network, and wherein said switchable coupling means comprises a splitter having first, second and third terminals for splitting electrical power at said third terminal thereof between said first and second terminals thereof in the same proportion as that of the respective sizes of said first and second areas of said transducer, a double-throw switch for selectively connecting the other end of said first matching network to said predetermined electrical impedance in a first switch position thereof or alternatively to said first terminal of said splitter in a second switch position thereof, the other end of said third matching network being connected to said second terminal of said splitter and said third terminal of said splitter being connectable to said predetermined electrical impedance.