On-chip directional coupler

Abstract

The on-chip directional coupler (300) includes a first linear conductive trace (306), a second linear conductive trace (308), and a conductive loop (305). The first linear conductive trace (306) includes an end (306A) and a coupled port (304A). The second linear conductive trace (308) is spaced apart from and parallel to the first linear conductive trace (306). The second linear conductive trace (308) includes an end (308A) and an isolated port (304B). The conductive loop (305) includes a first end (318B) conductively coupled to the end (306A) of the first linear conductive trace (306) and a second end (316B) conductively coupled to the end (308A) of the second linear conductive trace (308).

Description

[Technical field]

[0001] A directional coupler is a device that detects the power of a signal being transmitted in a particular direction. Directional couplers are used to detect signals in a wide variety of radio frequency circuits. A directional coupler includes four ports. The first port is an input port that receives a transmit signal from a source. The second port is an output port that provides the transmit signal to a destination. As the signal propagates from the first port to the second port, a portion of the signal is coupled into a third port. The third port is a coupled port, which outputs a signal that is coupled from the transmit signal. The fourth port is an isolated port. Preferably, no signal is coupled into the fourth port. The output of the third port may be applied to measure or control the power of the transmit signal or to determine a parameter of the transmit signal path. Summary of the Invention

[0002] Described herein is a directional coupler that provides independent control of magnetic and capacitive coupling. In one example, an on-chip directional coupler includes a first linear conductive trace, a second linear conductive trace, a first curved conductive trace, and a second curved conductive trace. The first linear conductive trace is formed in a first metal layer and includes an end and a coupled port. The second linear conductive trace is formed in the first metal layer and is spaced apart from and parallel to the first linear conductive trace. The second linear conductive trace includes an end and an isolated port. The first curved conductive trace is formed in a second metal layer and includes a first end and a second end. The first end is conductively coupled to the end of the first linear conductive trace. The second curved conductive trace is formed in the first metal layer and includes a first end and a second end. A first end of the second curved conductive trace is conductively coupled to a second end of the first curved conductive trace. A second end of the second curved conductive trace is conductively coupled to an end of the second linear conductive trace.

[0003] In another example, an on-chip directional coupler includes a first linear conductive trace, a second linear conductive trace, and a conductive loop. The first linear conductive trace includes an end and a coupled port. The second linear conductive trace is spaced from and parallel to the first linear conductive trace. The second linear conductive trace includes an end and an isolated port. The conductive loop includes a first end conductively coupled to the end of the first linear conductive trace and a second end conductively coupled to the end of the second linear conductive trace.

[0004] In a further example, an integrated circuit includes a transmit power amplifier, a transmit conductor, a transmit terminal, and a directional coupler. The transmit power amplifier includes an output. The transmit conductor includes a first end and a second end. The first end of the transmit conductor is conductively coupled to the output of the transmit power amplifier. The transmit terminal is conductively coupled to the second end of the transmit conductor. The directional coupler is configured to detect a signal in the transmit conductor and includes a first linear conductive trace, a second linear conductive trace, and a conductive loop. The first linear conductive trace is formed in a first metal layer and includes an end and a coupled port. The second linear conductive trace is formed in the first metal layer and is spaced apart from and parallel to the first conductive trace. The second linear conductive trace includes an end and an isolated port. The conductive loop is formed in the first metal layer and the second metal layer and includes a first end and a second end. A first end of the conductive loop is conductively coupled to an end of the first linear conductive trace, and a second end of the conductive loop is conductively coupled to an end of the second linear conductive trace. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a diagram of a conventional directional coupler.

[0006] [Diagram 2] 2 is a schematic diagram of an equivalent circuit for a portion of the directional coupler of FIG. 1.

[0007] [Diagram 3] FIG. 2 is a diagram of a first directional coupler that provides independent control of magnetic and capacitive coupling.

[0008] [Figure 4] 4 is a graph showing the performance of the directional coupler of FIG. 3.

[0009] [Diagram 5] FIG. 13 is a diagram of a second directional coupler that provides independent control of magnetic and capacitive coupling.

[0010] [Figure 6] 6 is a graph showing the performance of the directional coupler of FIG. 5.

[0011] [Figure 7] FIG. 13 is a diagram of a third directional coupler that provides independent control of magnetic and capacitive coupling.

[0012] [Figure 8] FIG. 1 is a block diagram for a circuit including a directional coupler that provides independent control of magnetic and capacitive coupling. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Radio frequency (RF) integrated circuits, such as automotive radar integrated circuits, include built-in self-test systems that use on-chip directional couplers to verify signal path components and connections. Conventional on-chip directional couplers suffer from parameter interdependencies that result in performance compromises, such as large circuit area or poor directivity. FIG. 1 is a diagram of a conventional directional coupler 100. The conventional directional coupler 100 includes a conductive signal trace 102, a conductive coupling trace 108, ground planes 114 and 116, and a load trace segment 118. The conductive signal trace 102 and the conductive coupling trace 108 are disposed on the same metal layer of the integrated circuit. The conductive signal trace 102 includes an input port 104 and an output port 106. The conductive coupling trace 108 includes a coupled port 110 and an isolated port 112. A signal enters the conductive signal trace 102 at the input port 104 and exits the conductive signal trace 102 at the output port 106. As a signal propagates through the conductive signal trace 102, a portion of the signal becomes magnetically and / or capacitively coupled to the conductive coupling trace 108. The coupled signal is provided at a coupled port 110.

[0014] Ground plane 114 and ground plane 116 isolate conductive signal traces 102 and conductive coupling traces 108 from noise sources within the integrated circuit. Ground plane 114 and ground plane 116 may be formed on the same metal layer as conductive signal traces 102 and conductive coupling traces 108 and / or on a metal layer other than the metal layer of conductive signal traces 102 and conductive coupling traces 108.

[0015] The load trace segments 118 are disposed on a metal layer of the integrated circuit other than the metal layer of the conductive signal traces 102 and the conductive coupling traces 108. The load trace segments 118 load the conductive signal traces 102 and the conductive coupling traces 108 to help control parasitic capacitance.

[0016] 2 is a schematic diagram of an equivalent circuit 200 for segment 120 (shown in FIG. 1) of conventional directional coupler 100. Segment 120 includes inductors 202 and 204 (where L is the inductance and k is the magnetic coupling between the inductors), coupling capacitors 206 and 208 (where C c ), and a parasitic capacitor 212 (parasitic capacitance C P ), 214, 216, and 218. In the equivalent circuit 200, k, C P , C c That is, varying the physical parameters of the segments 120 (e.g., the width or spacing of the conductive signal traces 102 and the conductive coupling traces 108) can affect the values ​​of k, C P , or C c Instead of varying k, C P , or C c This interdependence limits the performance of the conventional directional coupler 100. In the equivalent circuit 200, the characteristic impedance (Z o ) is as follows: TIFF2024524152000002.tif618, where Z e is the even mode impedance, Z o is the odd-mode impedance.

[0017] The even mode impedance is: TIFF2024524152000003.tif1125

[0018] The odd mode impedance is: TIFF2024524152000004.tif1125

[0019] The ratio of even mode impedance to odd mode impedance is: TIFF2024524152000005.tif1031

[0020] Even mode propagation constant (βe The ratio of the odd-mode propagation constant (β0) to the odd-mode propagation constant (β0) is: TIFF2024524152000006.tif1031

[0021] In equations (2) to (5), k, C P , C c Because the even and odd mode impedances and propagation constants are not independent, the even and odd mode impedances and propagation constants cannot be set independently to achieve low coupling and high directivity. FIG. 3 is a diagram of a directional coupler 300 that provides independent control of magnetic and capacitive coupling. The directional coupler 300 can be formed on an integrated circuit, a packaging substrate, a printed circuit board, etc. With independent control of magnetic and capacitive coupling, the directional coupler 300 allows the even and odd mode impedances and propagation constants to be set independently, thereby enabling improved directivity.

[0022] Directional coupler 300 includes a signal conductor 302 and a coupled conductor 304. Signal conductor 302 includes an input port 302A and an output port 302B. Coupled conductor 304 includes a coupled port 304A and an isolated port 304B. A signal introduced into signal conductor 302 via input port 302A exits signal conductor 302 at output port 302B. As a signal passes through signal conductor 302, a portion of the signal is magnetically and / or capacitively coupled into coupled conductor 304 and exits coupled conductor 304 via coupled port 304A.

[0023] The coupling conductor 304 includes a linear conductive trace 306, a linear conductive trace 308, and a conductive loop 305. A first end of the linear conductive trace 306 is conductively coupled to the coupled port 304A, and a second end 306A of the linear conductive trace 306 is conductively coupled to the conductive loop 305. A first end of the linear conductive trace 308 is conductively coupled to the isolated port 304B, and a second end 308A of the linear conductive trace 306 is conductively coupled to the conductive loop 305. The linear conductive trace 306, the linear conductive trace 308, and the conductive loop 305 are spaced apart from one another over the length (d p ) versus the diameter (d m 3, the diameter of conductive loop 305 is measured along centerline 319. Conductive loop 305 reverses the direction of current flow, such that the current flow in conductive loop 305 is in the opposite direction to the direction of current flow in linear conductive trace 306 and linear conductive trace 308, and the polarity of the magnetic flux in conductive loop 305 is opposite to the polarity of the magnetic flux between linear conductive trace 306 and linear conductive trace 308.

[0024] The linear conductive trace 306 and the linear conductive trace 308 are formed in the same metal layer of the integrated circuit. A first portion of the conductive loop 305 is formed in the same (first) metal layer as the linear conductive trace 306 and the linear conductive trace 308, and a second portion of the conductive loop 305 is formed in a different (second) metal layer of the integrated circuit. The conductive loop 305 includes a first curved conductive trace 316 and a second curved conductive trace 318. The second curved conductive trace 318 is formed in the same metal layer (first metal layer) as the linear conductive trace 306 and the linear conductive trace 308. The first curved conductive trace 316 is formed in a different metal layer (second metal layer) than the second curved conductive trace 318. The first curved conductive trace 316 includes a first end 316A and a second end 316B. The second curved conductive trace 318 includes a first end 318A and a second end 318B. A first end 316A of the first curved conductive trace 316 is coupled to a first end 318A of the second curved conductive trace 318 by a via 310 connecting the metal layers of the first curved conductive trace 316 and the second curved conductive trace 318. Similarly, a second end 316B of the first curved conductive trace 316 is coupled to a second end 308A of the linear conductive trace 308 by a via 312 connecting the metal layers of the first curved conductive trace 316 and the linear conductive trace 308. A second end 318B of the second curved conductive trace 318 is coupled to a second end 306A of the linear conductive trace 306.

[0025] The first curved conductive trace 316 includes a conductive trace segment 320, which may be coupled to and perpendicular to the linear conductive trace 306 and the linear conductive trace 308. The second curved conductive trace 318 includes a conductive trace segment 322, a conductive trace segment 324, and a conductive trace segment 326. The conductive trace segment 322 may be perpendicular to the linear conductive trace 306 and the linear conductive trace 308. The conductive trace segment 326 may be coupled to and perpendicular to the conductive trace segment 322. The conductive trace segment 324 may be coupled to and perpendicular to the conductive trace segment 326.

[0026] The signal conductor 302 may be formed on the same metal layer as the first curved conductive trace 316, the same metal layer as the second curved conductive trace 318, or a different metal layer. The coupling capacitance between the signal conductor 302 and the coupling conductor 304 may be reduced by placing the signal conductor 302 on a different metal layer than the linear conductive trace 306 and the linear conductive trace 308. A ground plane 328 separates the signal conductor 302 and the coupling conductor 304 from other circuitry of the integrated circuit.

[0027] By providing independent control of magnetic coupling, directional coupler 300 provides improved directivity (e.g., 3 decibel (dB) improvement) in an area significantly smaller (e.g., 60% smaller) than conventional directional couplers. FIG. 4 is a graph showing s-parameters of an implementation of directional coupler 300. FIG. 4 shows that the implementation of directional coupler 300 provides -16 dB coupling (S31), approximately 34 dB isolation (S41), 17-18 dB directivity (Dl, D2) with an 80 gigahertz (GHz) input signal, and less than 0.48 dB loss (S21) from the input port to the output port.

[0028] 5 is a diagram of another directional coupler 500 that provides independent control of magnetic and capacitive coupling. Directional coupler 500 is an implementation of directional coupler 300 that includes an additional linear conductive trace segment 502 disposed orthogonally to signal conductor 302. Linear conductive trace segment 502 may be coupled to ground plane 328. Linear conductive trace segment 502 periodically loads signal conductor 302 to reduce the parasitic capacitance (C p 5 shows that ports 302A, 302B, 304A, and 304B of directional coupler 500 can be routed in different directions as desired to facilitate connection of directional coupler 500 to other circuit elements of an integrated circuit.

[0029] 6 is a graph illustrating the performance of directional coupler 500. Loading signal conductor 302 with linear conductive trace segment 502 provides approximately 5 dB improvement in directivity compared to conventional directional couplers. In FIG. 6, one implementation of directional coupler 500 provides better than 20 dB directivity (D1, D2), less than 0.35 dB loss (S21), better than 16 dB coupling (S31), and better than 37 dB isolation (S41).

[0030] 7 is a diagram of another directional coupler 700 that provides independent control of magnetic and capacitive coupling. Directional coupler 700 is an implementation of directional coupler 300 or directional coupler 500 and includes a signal conductor 702 and a coupling conductor 704. Coupling conductor 704 includes a conductive loop 705 that corresponds to conductive loop 305 of directional coupler 300. In directional coupler 700, the width of conductive loop 705 is increased (relative to the spacing between linear conductive traces 306 and 308), and the width of signal conductor 702 around conductive loop 705 is correspondingly increased.

[0031] The conductive loop 705 may be provided in a variety of shapes. For example, the conductive loop 705 may be rectangular, octagonal, circular, etc. Similarly, the shape of the signal conductor 702 surrounding the conductive loop 705 may be provided in a variety of shapes (e.g., rectangular, octagonal, circular, etc.). The shape of the signal conductor 702 surrounding the conductive loop 705 may be the same as or different from the shape of the conductive loop 705.

[0032] FIG. 8 is a block diagram for an integrated circuit 800 including a directional coupler 804 that provides independent control of magnetic and capacitive coupling. The integrated circuit 800 may be a communication system integrated circuit, a radar sensor integrated circuit, or other integrated circuit. The directional coupler 804 may be an implementation of the directional coupler 300 or the directional coupler 500. The integrated circuit 800 includes a transmit power amplifier 802, a transmit conductor 806, and a transmit terminal 808. The transmit power amplifier 802 receives and amplifies a signal to be transmitted. The transmit power amplifier 802 includes an output 802A coupled to an end 806A of the transmit conductor 806. The transmit conductor 806 may effectively act as a signal conductor for the directional coupler 804. An end 806B of the transmit conductor 806 is coupled to the transmit terminal 808. The transmit terminal 808 may be an output of the integrated circuit 800 for connecting the integrated circuit 800 to a package. Directional coupler 804 detects the signal in transmission conductor 806 and provides the combined signal to circuit elements of integrated circuit 800 for analysis and control.

[0033] In some implementations of integrated circuit 800, directional coupler 804 is designed in conjunction with the packaging of integrated circuit 800 such that the package capacitance is included in the design of the directional coupler. By including the package capacitance in the parasitic capacitance of directional coupler 804, transmit signal loss may be reduced compared to designs that use shunt stubs to resonate the package capacitance.

[0034] The term "couple" is used throughout this specification. This term may encompass a connection, communication, or signal path that enables a functional relationship consistent with the description of this disclosure. For example, in a first example, device A is coupled to device B if device A generates a signal to control device B to perform an action, or in a second example, device A is coupled to device B via an intervening component C such that device B is controlled by device A via a control signal generated by device A, where the intervening component C does not substantially change the functional relationship between devices A and B.

[0035] Modifications may be made to the exemplary embodiments described, and other embodiments are possible, within the scope of the invention.

Claims

1. A directional coupler comprising: a first linear conductive trace in a first metal layer, the first linear conductive trace including an end and a port to be coupled; a second linear conductive trace in the first metal layer spaced from the first linear conductive trace and parallel to the first linear conductive trace, the second linear conductive trace including an end and an insulated port; a first curved conductive trace in a second metal layer, the first curved conductive trace including a first end conductively coupled to an end of the second linear conductive trace and a second end; a second curved conductive trace in the first metal layer, the second curved conductive trace including a first end conductively coupled to the second end of the first curved conductive trace and a second end conductively coupled to an end of the second linear conductive trace; and a directional coupler including the same.

2. The directional coupler according to claim 1, further comprising: a first via connecting an end of the second linear conductive trace and a first end of the first curved conductive trace; a second via connecting a second end of the first curved conductive trace and a first end of the second curved conductive trace; and a directional coupler including the same.

3. The directional coupler according to claim 1, further comprising: a signal trace around the first linear conductive trace, the second linear conductive trace, the first curved conductive trace, and the second curved conductive trace, the signal trace including an input port and an output port.

4. The directional coupler according to claim 3, wherein the signal trace is in the second metal layer.

5. The directional coupler according to claim 3, further comprising a plurality of linear conductive trace segments, each of the plurality of linear conductive trace segments being on a metal layer different from the signal trace and orthogonal to the signal trace.

6. The directional coupler according to claim 1, wherein the first curved conductive trace further includes a first conductive trace segment perpendicular to the first linear conductive trace and the second linear conductive trace, and the second curved conductive trace further includes a second conductive trace segment perpendicular to the first linear conductive trace and the second linear conductive trace.

7. The directional coupler according to claim 6, wherein the second curved conductive trace further includes a third conductive trace segment electrically connected to the second conductive trace segment and perpendicular to the second conductive trace segment.

8. The directional coupler according to claim 7, wherein the second curved conductive trace further includes a fourth conductive trace segment electrically connected to the third conductive trace segment and perpendicular to the third conductive trace segment.

9. A directional coupler, a first linear conductive trace including an end portion and a port to be coupled, a second linear conductive trace spaced apart from the first linear conductive trace and parallel to the first linear conductive trace, the second linear conductive trace including an end portion and an insulated port, first and second vias, a conductive loop, A first curved conductive trace having a first end conductively coupled to an end of the second linear conductive trace via the first via, A second curved conductive trace having a first end conductively coupled to a second end of the first curved conductive trace and a second end conductively coupled to an end of the first linear conductive trace, The conductive loop including the above, A directional coupler including the above.

10. The directional coupler according to claim 9, The directional coupler, wherein the first linear conductive trace and the second linear conductive trace are within a first metal layer.

11. The directional coupler according to claim 10, The directional coupler, wherein the first curved conductive trace is in a second metal layer and the second curved conductive trace is in the first metal layer.

12. The directional coupler according to claim 9, The directional coupler further including a signal trace around the first linear conductive trace, the second linear conductive trace, and the conductive loop, the signal trace including an input port and an output port.

13. The directional coupler according to claim 12, The directional coupler further including a plurality of linear conductive trace segments configured to periodically load the signal trace.

14. The directional coupler according to claim 9, In the on-chip directional coupler, the magnetic coupling is a function of the ratio of the diameter of the conductive loop to the length of the first linear conductive trace and the second linear conductive trace, The directional coupler, wherein the diameter of the conductive loop is measured along a center line of the conductive loop parallel to the first linear conductive trace and the second linear conductive trace.

15. An integrated circuit comprising: A transmission power amplifier including an output; A transmission conductor including a first end conductively coupled to the output of the transmission power amplifier and a second end; A transmission terminal conductively coupled to the second end of the transmission conductor; A directional coupler configured to detect a signal within the transmission conductor, A first linear conductive trace in a first metal layer, the first linear conductive trace including an end and a port to be coupled; A second linear conductive trace in the first metal layer spaced apart from the first linear conductive trace and parallel to the first linear conductive trace, the second linear conductive trace including an end and an insulated port; A conductive loop in the first metal layer and a second metal layer, the conductive loop including a first end conductively coupled to the end of the first linear conductive trace and a second end conductively coupled to the end of the second linear conductive trace; The directional coupler including; An integrated circuit including.

16. The integrated circuit according to claim 15, wherein the directional coupler further includes a signal trace as a part of the transmission conductor around the first linear conductive trace, the second linear conductive trace, and the conductive loop.

17. The integrated circuit according to claim 15, further including a plurality of linear conductive trace segments, each of the linear conductive trace segments being on a metal layer different from the signal trace and orthogonal to the signal trace.

18. The integrated circuit according to claim 15, An integrated circuit, wherein the first linear conductive trace is configured to supply current to the conductive loop, and the second linear conductive trace is configured to supply current from the conductive loop. Claim 19 The integrated circuit according to claim 15, wherein the magnetic coupling in the directional coupler is a function of a ratio of a diameter of the conductive loop to lengths of the first linear conductive trace and the second linear conductive trace, and the diameter of the conductive loop is measured along a center line of the conductive loop parallel to the first linear conductive trace and the second linear conductive trace.

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