Intrinsically switched multiplexing filter devices, systems, and methods

Abstract

An RF ISM filter is disclosed. The filter includes parallel filter channel circuits having first and second switches, a control input node connected to the first and second switches, first and second RF ports, first and second microstrip input transmission lines respectively connected to the first and second RF ports, and additional microstrip transmission lines connected to the first and second switches and connected to the first and second input transmission lines, where a conductivity state of the first and second switches is determined by the control signal, where, in response to the first and second switches having a first conductivity state, an RF signal transfer function between the first and second RF ports has a bandpass characteristic, and where, in response to the first and second switches having a second conductivity state, the RF signal transfer function between the first and second RF ports has an all stop characteristic.

Description

Docket No. QID241640 / 62306.201W001INTRINSICALLY SWITCHED MULTIPLEXING FILTER DEVICES, SYSTEMS, AND METHODSRELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application No. 63 / 727,301, filed December 03, 2024 and U.S. Provisional Application No. 63 / 759,843, filed January 18, 2025, which are incorporated herein by reference in their entireties.

[0002] The present application is related to U.S. Provisional Application No. 63 / 797,526, filed on April 30, 2025, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0003] The present disclosure relates generally to intrinsically switched multiplexing (ISM) filters, and in particular, relates to ISM filters which can be implemented in microstrip technology.BACKGROUND

[0004] Intrinsically switched multiplexer (ISM) filter devices can be used in a variety of applications. ISM filter devices may be used, for example, in communication devices, such as radios and cell phones, to filter analog signals. As another example, ISM filter devices may be used in electronic surveillance applications where high out-of-band rejection is useful to filter hostile jammers or friendly signals nearby in the local vicinity. A single ISM filter may include a number of filter channel circuits connected in parallel that can be selectively switched on and off. The ISM filters may be programmable to have a selectable transfer function. In order for ISM filters to suit intended applications, their sensitivity to noise and coupling should be minimized.SUMMARY

[0005] Embodiments of the present disclosure include ISM filter circuits and methods.

[0006] One inventive aspect is a radio frequency (RF) intrinsically switched multiplexing (ISM) filter including a plurality of parallel filter channel circuits, each filter channel circuit including first and second switches, a control input node connected to the first and second switches, and configured to receive a control signal, first and second RF ports, first and second microstrip input transmission lines respectively connected to the first and second RF ports, and a plurality of additional microstrip transmission lines connected to the first and second switches and connected to the first and second input transmission lines, where a conductivity state of the first and second switches is determinedDocket No. QID241640 / 62306.201W001by the control signal, where, in response to the first and second switches having a first conductivity state, an RF signal transfer function between the first and second RF ports has a bandpass characteristic, and where, in response to the first and second switches having a second conductivity state, the RF signal transfer function between the first and second RF ports has an all stop characteristic, where the bandpass characteristic of a first filter channel circuit is different from the bandpass characteristic of a second filter channel circuit.

[0007] In some implementations, the additional microstrip transmission lines include first and second microstrip grounded transmission lines (Zs) connected to a ground plane, and respectively connected to the first and second input transmission lines, first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines, and first and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.

[0008] In some implementations, the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, where the first via is electromagnetically isolated from the first coupling transmission line, where the second via is electromagnetically isolated from the second coupling transmission line, and where the first via is electromagnetically isolated from the second via.

[0009] In some implementations, the additional microstrip transmission lines include a microstrip resonator transmission line connected to each of the first and second microstrip coupling transmission lines.

[0010] In some implementations, the first and second grounded transmission lines have a first geometry, where the first and second coupling transmission lines have a second geometry, where the first and second geometries cause the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines, and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

[0011] In some implementations, the first and second coupling transmission lines have a first length, where the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and where the first and second vias are spaced apart by a distance greater than two times the first length.Docket No. QID241640 / 62306.201W001

[0012] In some implementations, at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and where at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

[0013] Another inventive aspect is a method of using a radio frequency (RF) intrinsically switched multiplexing (ISM) filter, the method including providing a plurality of control signals to a plurality of parallel filter channel circuits to select between a bandpass characteristic and an all block characteristic for each of the filter channel circuits, where the bandpass characteristic of a first filter channel circuit is different from the bandpass characteristic of a second filter channel circuit, and where each filter channel circuit includes first and second microstrip input transmission lines respectively connected to first and second RF ports, and a plurality of additional microstrip transmission lines connected to the first and second input transmission lines, and transmitting an RF signal from the first RF port to the second RF port through the filter channel circuits, where a frequency transfer function of the filter channel circuits is determined by the control signals.

[0014] In some implementations, the additional microstrip transmission lines include first and second microstrip grounded transmission lines connected to a ground plane, and respectively connected to the first and second input transmission lines, first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines, and first and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.

[0015] In some implementations, the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, where the first via is electromagnetically isolated from the first coupling transmission line, where the second via is electromagnetically isolated from the second coupling transmission line, and where the first via is electromagnetically isolated from the second via.

[0016] In some implementations, the additional microstrip transmission lines include a microstrip resonator transmission line connected to each of the first and second microstrip coupling transmission lines.

[0017] In some implementations, the first and second grounded transmission lines have a first geometry, where the first and second coupling transmission lines have a second geometry, where the first and second geometries cause the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines,Docket No. QID241640 / 62306.201W001and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

[0018] In some implementations, the first and second coupling transmission lines have a first length, where the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and where the first and second vias are spaced apart by a distance greater than two times the first length.

[0019] In some implementations, at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and where at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

[0020] Another inventive aspect is a wireless device including first and second radio frequency (RF) circuits, an intrinsically switched multiplexing (ISM) filter configured to receive an RF signal from the first RF circuit, and to transmit a filtered RF signal to the second RF circuit, the ISM filter including a plurality of parallel filter channel circuits, each filter channel circuit including first and second switches, a control input node connected to the first and second switches, and configured to receive a control signal, first and second RF ports, first and second microstrip input transmission lines respectively connected to the first and second RF ports, and a plurality of additional microstrip transmission lines connected to the first and second switches and connected to the first and second input transmission lines, where a conductivity state of the first and second switches is determined by the control signal, where, in response to the first and second switches having a first conductivity state, an RF signal transfer function between the first and second RF ports has a bandpass characteristic, and where, in response to the first and second switches having a second conductivity state, the RF signal transfer function between the first and second RF ports has an all stop characteristic, where the bandpass characteristic of a first filter channel circuit is different from the bandpass characteristic of a second filter channel circuit.

[0021] In some implementations, the additional microstrip transmission lines include first and second microstrip grounded transmission lines (Zs) connected to a ground plane, and respectively connected to the first and second input transmission lines, first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines, and first and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.

[0022] In some implementations, the first and second grounded transmission lines are respectivelyDocket No. QID241640 / 62306.201W001connected to the ground plane by first and second vias, where the first via is electromagnetically isolated from the first coupling transmission line, where the second via is electromagnetically isolated from the second coupling transmission line, and where the first via is electromagnetically isolated from the second via.

[0023] In some implementations, the first and second grounded transmission lines have a first geometry, where the first and second coupling transmission lines have a second geometry, where the first and second geometries cause the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines, and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

[0024] In some implementations, the first and second coupling transmission lines have a first length, where the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and where the first and second vias are spaced apart by a distance greater than two times the first length.

[0025] In some implementations, at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and where at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

[0026] Additional aspects, embodiments, implementations, features, and advantages of the present disclosure will become apparent from the following detailed description.

[0027]

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0030] Figure 1 illustrates a schematic representation of a wireless device having an ISM filter, according to aspects of the present disclosure.

[0031] Figure 2 illustrates a schematic representation of a programmable ISM filter channel, according to aspects of the present disclosure.

[0032] Figure 3 illustrates a schematic representation of a programmable ISM filter channel, according to aspects of the present disclosure.

[0033] Figure 4A illustrates a schematic representation of a portion of the programmable ISM filter channel of figure 2, according to aspects of the present disclosure.

[0034] Figure 4B illustrates a schematic representation of a portion of the programmable ISMDocket No. QID241640 / 62306.201W001filter channel of figure 3, according to aspects of the present disclosure.

[0035] Figure 5A illustrates a schematic representation of a portion of the programmable ISM filter channel of figure 2, according to aspects of the present disclosure.

[0036] Figure 5B illustrates a schematic representation of a portion of the programmable ISM filter channel of figure 3, according to aspects of the present disclosure.

[0037] Figure 6 illustrates a graph of absolute difference between y-parameters of the portion of the programmable ISM filter channel of figure 2 and corresponding y-parameters of the portion of the programmable ISM filter channel of figure 3.

[0038] Figure 7 illustrates a layout diagram of a programmable ISM filter channel, according to aspects of the present disclosure.

[0039] Figure 8 illustrates a layout diagram of a programmable ISM filter, according to aspects of the present disclosure.

[0040]

[0041] DETAILED DESCRIPTION

[0042] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one embodiment may be combined with the features, components, and / or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0043] Previous ISM Filter designs require a homogenous stripline implementation to achieve an acceptable level of out of band rejection. Some embodiments may be advantageously implemented as Monolithic Microwave Integrated Circuits (MMICs), for example, having an inhomogeneous stripline medium using a GaAs MMIC with a backside ground and front side copper (Cu) pillars. The MMIC may be flipped on and mounted to a gold plated CuMo TAB package, where bumps act as standoffs producing, for example, a ~ 90 micron airgap between the TAB ground plane and the active side of the MMIC. The TAB may, for example, have a CuMo plate with flatness and plating consistent with vacuum reflow solder attach that is sized slightly larger than the MMIC being attached.Docket No. QID241640 / 62306.201W001

[0044] These implementations may have good filter rejection characteristics. Alternative embodiments may be used for improved production testability, reduced physical size, and reduced cost. These embodiments may be implemented with flip chip mounting with or without underfill. These embodiments may be manufactured as production released and tested upright microstrip MMICs. However, the flipped chip mounting on TAB approach may not be manufacturable and in many cases is not reliable. This is likely the case even with underfill, for example, at least for some sizes of MMICs. Embodiments discussed herein allow for upright mounting and hence the realization of a manufacturable, testable, reliable, and sellable product.

[0045] Some embodiments benefit from separation of connection vias that do not couple or minimally couple for sufficient out-of-band rejection. Some embodiments are manufactured with standard released semiconductor manufacturing flows. Some embodiments are compatible with known reliable mounting techniques for the next level assembly. Some embodiments are manufactured with on-wafer RF test compatibility such that the filters and filter channels can be tested and screened prior to being integrated with other devices.

[0046] Figure 1 illustrates a schematic representation of a wireless device 105 having an ISM filter 100 connected to RF circuits 110 and 120 by manifolds 115 and 125, according to aspects of the present disclosure. ISM filter 100 is configured to receive an RF signal from RF circuit 110 at manifold 115, and to transmit a filtered RF signal to RF circuit 120 via manifold 125. ISM filter 100 includes a number (N) of programmable ISM filter channels 130 having characteristics similar or identical to those of programmable ISM filter channels discussed elsewhere herein. As illustrated, the programmable ISM filter channels 130 are connected in parallel to RF ports RF through manifolds 115 and 125. Manifolds 115 and 125 are designed in conjunction with ISM filter channels 130 so that ISM filter 100 achieves the desired composite frequency response. In some embodiments, the RF ports RF have 50-ohm termination.

[0047] In some embodiments, one or more of the programmable ISM filter channels 130 a selectable filter response. For example, one or more of the programmable ISM filter channels 130 may have either a bandpass filter response or an all stop filter response, according to their programmed states. In some embodiments, one or more of the programmable ISM filter channels 130 have a selectable bandpass filter response which is different from a bandpass filter response of one or more others of the programmable ISM filter channels 130. Because the parallel configured programmable ISM filter channels 130 are individually programmable, the filter response of ISM filter 200 is programmable, and is described by the combination of programmed filter response states of the individual program programmable ISM filter channels 130.

[0048] In embodiments having N programmable ISM filter channels, 2N different filter responsesDocket No. QID241640 / 62306.201W001can be realized through programming by activating or deactivating the individual channels with control voltages VC.

[0049] Figure 2 illustrates a schematic representation of a programmable ISM filter channel 200, according to aspects of the present disclosure. Programmable ISM filter channel 200 includes switches Q1, control input VC, Resistors R, RF ports RF, input transmission lines Z1 having parameters Zo1 and q1, edge coupled transmission lines Z2 having parameters Ze, Zo, and q, resonator transmission line Z3 having parameters Zr and qr, and capacitors C1, C2, and C3. As indicated, identified coupling sections 210 include capacitors C1, and coupled transmission lines Z2.

[0050] Programmable ISM filter channel 200 is schematically symmetric. In some embodiments, programmable ISM filter channel 200 is physically symmetric. In some embodiments, programmable ISM filter channel 200 is not physically symmetric. In some embodiments, like components have geometric characteristics which are designed to be the same as corresponding geometric characteristics of corresponding components.

[0051] As illustrated, programmable ISM filter channel 200 includes first and second sets of components coupled by resonator transmission line Z3. As illustrated, the first and second sets of components are schematically symmetric. In some embodiments, the first and second sets of components are physically symmetric. In some embodiments, the first and second sets of components are not physically symmetric. In some embodiments, the first set of components have geometric characteristics which are designed to be the same as corresponding geometric characteristics of the second set of components.

[0052] Programmable ISM filter channel 200 is bidirectional, and is configured to receive an RF signal from one of the RF ports RF and transmit a corresponding filtered RF signal to the other of the RF ports RF. In addition, programmable ISM filter channel 200 is configured to perform a selected one of multiple filtering functions.

[0053] Capacitors C3 are configured to couple an input RF signal between the RF ports RF and the input transmission lines Zl.

[0054] Input transmission lines Zl transmit RF signals to or from capacitors C2 and edge coupled transmission lines Z2.

[0055] Edge coupled transmission lines Z2 are proximally positioned so as to have a desired edge coupling. Capacitors C2 also provide additional coupling between edge coupled transmission lines Z2.

[0056] The transmission line lengths q(f) = qo(f / fo) correspond with design frequency, where the specified value qo is the electrical length at reference frequency fo.Docket No. QID241640 / 62306.201W001

[0057] Switches coupled to control input VC by resistors R. In operation, when switches QI are biased “OFF,’-for example, if the voltage of control input VC is less than a threshold, switches QI behave like small value shunt capacitors and the circuit realizes an effective 3-pole bandpass response. In contrast, when switches QI are biased “ON,” for example, if the voltage of control input VC is greater than a threshold, the circuit behaves like an all stop filter. For example, the circuit may have over 40 dB of rejection wideband.

[0058] Maintaining high out-of-band rejection is advantageous to the operation of ISM Filter channel 200. In some physical implementations, edge coupled transmission lines Z2 are connected to a ground or a ground plane using vias V. In some physical implementations, the vias V each radiate according to the signal being transmitted, where the electromagnetic radiation coupled from a first via V to the other via V is significant, and reduces, for example, out-of-band rejection. In some embodiments, simulations with and without the electromagnetic via coupling showed that the electromagnetic via coupling can degrade out-of-band rejection by, for example more than 25 dB.

[0059] In some embodiments, “Via Fences” may be added between the vias V to provide shielding. However, for a microstrip realization, much of the electromagnetic coupling occurs outside the MMIC, for example, in the air above the MMIC. A homogenous stripline realization may not have the same electromagnetic via coupling because a second ground or ground plane provides shielding which places the circuit in waveguide cutoff, such that little propagation can occur above or below the surface of the MMIC.

[0060] In a microstrip realization, radiating vias could, in principle, be separated enough to reduce the coupling to an acceptable level (e.g., > 35dB isolation). However, physical proximity of the edge coupled transmission lines Z2, and / or other practical considerations limit where the vias can be effectively placed and limit achievable separation of the vias V.

[0061] Figure 3 illustrates a schematic representation of an alternative programmable ISM filter channel 300, according to aspects of the present disclosure. Programmable ISM filter channel 300 includes switches Q1, control input VC, Resistors R, RF ports RF, input transmission lines Z1 having parameters Zo1 and q1, grounded transmission lines Z2 having parameters Zs and qs, coupling transmission lines Z3 having parameters Zc and qc, resonator transmission line Z4 having parameters Zr and qr, and capacitors C1, C2, and C3. Programmable ISM filter channel 300 also includes capacitances Cc, which are additional capacitances to be added to capacitor C2, as discussed in further detail below. As indicated, identified coupling sections 310 each include one of each of capacitors C1, grounded transmission lines Z2, coupling transmission lines Z3, and capacitances Cc. Alternative embodiments omit capacitors C1, and switches Q1 are connected to capacitors C2, capacitances Cc, and coupling transmission lines Z3.Docket No. QID241640 / 62306.201W001

[0062] In some embodiments, ISM filter channel 300 is implemented with microstrip technology. For example, any or all of input transmission lines Zl, grounded transmission lines Z2, coupling transmission lines Z3, and resonator transmission line Z4 may be implemented as microstrip transmission lines.

[0063] Programmable ISM filter channel 300 is schematically symmetric. In some embodiments, programmable ISM filter channel 300 is physically symmetric, In some embodiments, programmable ISM filter channel 300 is not physically symmetric. In some embodiments, like components have geometric characteristics which are designed to be the same as corresponding geometric characteristics of corresponding components.

[0064] As illustrated, programmable ISM filter channel 300 includes first and second sets of components coupled by resonator transmission line Z4. As illustrated, the first and second sets of components are schematically symmetric. In some embodiments, the first and second sets of components are physically symmetric. In some embodiments, the first and second sets of components are not physically symmetric. In some embodiments, the first set of components have geometric characteristics which are designed to be the same as corresponding geometric characteristics of the second set of components.

[0065] Programmable ISM filter channel 300 is bidirectional, and is configured to receive an RF signal from one of the RF ports RF and transmit a corresponding filtered RF signal to the other of the RF ports RF. In addition, programmable ISM filter channel 300 is configured to perform a selected one of multiple filtering functions.

[0066] Capacitors C3 are configured to couple RF signals between the RF ports RF and the input transmission lines Zl.

[0067] Input transmission lines Zl transmit RF signals to or from capacitors C2 and coupling grounded transmission lines Z3.

[0068] Coupling transmission lines Z3 and grounded transmission lines Z2 may be physically positioned so as to have a desired minimum or more electromagnetic isolation. In addition, coupling transmission lines Z3 and grounded transmission lines Z2 may be physically positioned such that the vias of grounded transmission lines Z2 have a desired minimum electromagnetic isolation. In some embodiments, the electromagnetic isolation is greater than about 30 dB, 35 dB, 40 dB, 45 dB, 50 dB, or another value. In addition, grounded transmission lines Z2 are physically positioned such that the vias of grounded transmission lines Z2 have a desired minimum electromagnetic isolation from resonator transmission line Z4. In some embodiments, the electromagnetic isolation is greater than about 30 dB, 35 dB, 40 dB, 45 dB, 50 dB, or another value.

[0069] Capacitors C2 provide coupling between grounded transmission lines Z2 and couplingDocket No. QID241640 / 62306.201W001transmission lines Z3.

[0070] The transmission line lengths q(f) = qo(f / fo) correspond with design frequency, where the specified value qo is the electrical length at reference frequency fo.

[0071] Switches coupled to control input VC by resistors R. In operation, when switches QI are biased “OFF,” for example, if the voltage of control input VC is less than a threshold, switches QI behave like small value shunt capacitors and the circuit realizes an effective 3-pole bandpass response. In contrast, when switches QI are biased “ON,” for example, if the voltage of control input VC is greater than a threshold, the circuit behaves like an all stop fdter. For example, the circuit may have over 40 dB of rejection wideband.

[0072]

[0073] ISM filter channel 200 circuit of figure 2 has advantageous filtering characteristics and functionality, and, in some implementations, suffers from electromagnetic via coupling. ISM filter channel 300 circuit is equivalent to ISM filter channel 200 circuit, as shown below, and can be implemented with significantly better electromagnetic via isolation.

[0074] Edge coupled microstrip lines generally take advantage of the capacitive coupling of one line to the other. In ISM filter channel 200, edge coupled transmission lines Z2 are edge coupled, and capacitors C2 provide additional capacitive coupling over what is realized by the edge coupling. In contrast, in some embodiments of ISM filter channel 300, grounded transmission lines Z2 are not coupled or not significantly or not predominantly coupled to coupling transmission lines Z3 through edge coupling. Instead, in some embodiments of ISM filter channel 300, grounded transmission lines Z2 and coupling transmission lines Z3 are predominantly coupled by capacitances C2 and Cc.

[0075] Because grounded transmission lines Z2 and coupling transmission lines Z3 are not coupled or not significantly coupled or not predominantly coupled through edge coupling, grounded transmission lines Z2 can be physically implemented with significant physical separation of the vias V to improve electromagnetic isolation and out-of-band rejection. Furthermore, without the geometric constraints imposed by an edge coupling configuration, layout area can be reduced, for example, by generating serpentined or coiled transmission lines. In addition, the grounded transmission lines Z2 and coupling transmission lines Z3 of ISM filter channel 300 have higher impedances Zs and Zc than the edge coupled transmission lines Z3 of ISM filter channel 200, and can therefore be implemented with narrower widths than edge coupled transmission lines Z3 of ISM filter channel 200, further reducing layout area of ISM filter channel 300 when compared with ISM filter channel 200.

[0076] Figure 4A illustrates a schematic representation of the coupling section 210 of the programmable ISM filter channel 200, according to aspects of the present disclosure. Figure 4BDocket No. QID241640 / 62306.201W001illustrates a schematic representation of the coupling section 310 of the programmable ISM filter channel 300, according to aspects of the present disclosure. The remaining portions of ISM filter channel 200 and ISM filter channel 300 outside the coupling sections 210 and 310 are identical. Accordingly, showing equivalence of the differing coupling sections 210 and 310 illustrated in figures 4A and 4B, shows equivalence of ISM filter channel 200 circuit and ISM filter channel 300 circuit.

[0077] In figures 4A and 4B, capacitance C is the series combination of C l and the OFF-state capacitance of the switch QI in both of ISM filter channel 200 and ISM filter channel 300. Capacitance C is common to both coupling sections 210 and 310 circuits. Capacitance Cc is the additional capacitance to be added to C2 in the coupling section 310 to account for the edge coupling capacitance of the edge coupled transmission lines Z2 in ISM filter channel 200, and to achieve equivalence. The parameters Zc, qc, Zs, qs, and Cc are determined so that coupling section 310 is functionally equivalent to coupling section 210.

[0078] Coupling sections 210 and 310 are analyzed below to show equivalence.

[0079] Starting with coupling section 210, with V4 = 0 and 13 = -jwCV3, the y-parameter matrix is expanded:

[0080]

[0081] I1= y11V1+ y21V2+ y31V3(1a)

[0082]

[0083] I2= y21V1+ y11V2+ y23V3(1b)

[0084]

[0085] I3= y31V1+ y23V2+ y11V3= -jωCV3(1c)

[0086]

[0087] Solving equation (1c) for V3, substituting and rearranging one can reduce the problem to a 2-port y-parameter matrix,

[0088] y211+jωCy11-y231y21y11+jωCy21-y23y31V1

[0089] AlA. y2i >'11 +7CJCy2 i-y^sysi yji+7fr> Cyn-yz3 V21yn+ja>c yn + / o> C

[0090] where

[0091] y11= -j / 2(Yoecot θe+ Yoocot θo),

[0092] y31= -j / 2(Yoecot θe- Yoocot θo),

[0093] y21=j / 2(Yoecsc θe- Yoocsc θo),Docket No. QID241640 / 62306.201W001

[0094] y23=j / 2(Yoecsc θe+ Yoocsc θo),

[0095] where Yoe, Yoo,qe and qo are the even and odd mode characteristic admittances and electrical length for the edge coupled lines of coupling section 210.

[0096] Withqe ~ qo = q, the y-parameter matrix reduces to:y211+jωCy11-y231jωCy21V1y11+jωC y11+jωCjωCy21y211+jωCy11-y223V2y11+jωC y11+jωC (2)~^ (yoe + Koo) cot0

[0098] 711 =(3a)- (Yoe - Koo) cot0

[0099] y31“ (3b) j (Yne- Yoo) esc 0

[0100] 3 / 21“ (3c)^ (Yoe + Y00) CSC 0 [oioi]3 / 23“ (3d)

[0102]

[0103] Analysis of coupling section 310 may be done using a chain matrix approach. The chain matrix for coupling section 310 is shown below.AeB

[0104] e®TT] M4CeDe_

[0105]

[0106] Chain matrices for the p-section (Zs, Cc, and C) and the series transmission line Zc are -A fi] 1 +7- B4

[0107] GC[7mC -j (l + ^) n cot0sC4D4_ cos0cjZcsm0cJYcsin0ccos0c

[0108]

[0109] Performing the matrix multiplication

[0110] Ae= AπA4+ BπC4=1 / ωC[ω(Cc+ C)cosθc+ Ycsinθc]

[0111] Be= AπB4+ BπD4=j / ωC[ω(Cc+ C)Zcsinθc— cosθc]

[0112] Ce= CπA4+ DπC4= j[ωC - (1 + C / Cc)Yscot θs]cosθc+ jYc(1 - Yscotθs / ωCc)sinθc

[0113] De= CπB4+ DπD4= -Zc(ωC - (1 + C / Cc)Yscotθs)sinθc+ (1 - Yscotθs / ωCc)cosθcDocket No. QID241640 / 62306.201W001

[0114]

[0115] Converting to y-parameters for coupling section 310,rni w e °e. <j>[< DCcc-(c+cc)yscot0s]-(<uQ-yscott?s)yccot0c7n—Be~ J < D(cc+c)-yccot0cP P-1 (i> CcYccsc9c

[0117] = - =

[0118] yj, = — = -I ^c^c~>v^o rs^JBeJa)(Cc+C)-Yccot0c

[0119]

[0120] Substituting equations 3a-3d into equation 2, yields the y-parameter matrix for coupling section 210.. 2YoeYoocot23-a)C(Yoe+Yoo)cot3

[0121] - V7i111=J / - 2a)C—(Yoe+Yoo')cot3_ _. OiC(Yoe-Yoo)csc0

[0122] 721 - 712 - J 2cDC—(Yoe+Yoo~)cot9wc(yoe+yoo) cote+-(Yoe+Yooy

[0123] 7,7= — i - - -J2wc-(yoe+yoo)cot6>

[0124]

[0125] The y-parameters for the coupled line circuit and equivalent circuit have the same basic functional form.

[0126] Figure 5A illustrates a schematic representation of a portion 520 of the edge coupled programmable ISM filter channel 200 of figure 2, according to aspects of the present disclosure. Figure 5B illustrates a schematic representation of a portion 530 of the programmable ISM filter channel 300 of figure 3, according to aspects of the present disclosure.

[0127] In figures 5 A and 5B, capacitance C is the series combination of Cl and the OFF-state capacitance of the switch QI in both of ISM filter channel 200 and ISM filter channel 300. Capacitance C is common to both coupling sections 210 and 310 circuits. Capacitance Cc is the additional capacitance to be added to C2 in the coupling section 310 to account for the edge coupling capacitance of the edge coupled transmission lines Z2 in ISM filter channel 200, and to achieve equivalence. The parameters Zc, qc, Zs, qs, and Cc are determined so that coupling section 310 is functionally equivalent to coupling section 210.

[0128] Numerical analysis performed with computer simulation shows functional equivalence of portion 520 of the programmable ISM filter channel 200 and portion 530 of the programmable ISM filter channel 300. For example, an example of portion 520 of the edge coupled programmable ISM filter channel 200 having edge coupled transmission lines Z22 with parameters Zoe, Zoo, and q was simulated. The example had two 6 mm thick coupled transmission lines on a 100mm thick GaAs substrate. The transmission lines were each 100mm wide, and were separated by 100mm. TheDocket No. QID241640 / 62306.201W001example edge coupled circuit had the following parameters: Zoe = 46.42 W, Zoo = 36.07W and q = 30°. Using C = 0.3pF for both portion 520 of the edge coupled programmable ISM filter channel 200 and portion 530 of the edge coupled programmable ISM filter channel 300, the parameters for portion 530 of the edge coupled programmable ISM filter channel 300 found to result in equivalence with portion 520 of the edge coupled programmable ISM filter channel 200 are: Zc = 44.3W, qc = 25.87°, Zs = 56.69W, qs = 21.81°, andCc = 0.0382pF. The reference frequency for the transmission lines is fo = 10GHz. Note that portions 520 and 530 are symmetric, meaning that yl 1 = y22 and y21 = yl2.

[0129] Figure 6 illustrates a graph of absolute difference between y-parameters of the portion 520 of the programmable ISM filter channel 200 of figure 2 and corresponding y-parameters of the portion 530 of the programmable ISM filter channel 300 of figure 3. Curve Mag yl 1 shows the magnitude of the yll parameter over frequency. Curve Mag y21 shows the magnitude of the y21 parameter over frequency. Curve Angle yll shows the phase angle of the yll parameter over frequency. Curve Angle y21 shows the phase angle of the y21 parameter over frequency.

[0130] As illustrated, the y-parameters of portions 520 and 530 are effectively identical. The simulations show that portions 520 and 530 are equivalent to at least 3 decimal places.

[0131] As understood by those of skill in the art, the accuracy of numerical analysis techniques is limited, and accordingly yield estimates. As used herein, the term equivalent may apply to circuits whose numerically analyzed performance differences are dominated by accuracy limitations of numerical analysis. Similarly, the accuracy of performance measurement techniques is limited, and accordingly yield estimates. Therefore, as used herein, the term equivalent may apply to circuits whose measured performance differences are dominated by accuracy limitations of measurement techniques. As used herein, the term equivalent may apply to circuits whose performance is the same to at least 2, 3, 4, or more decimal places.

[0132] Figure 7 illustrates a diagram 700 of a layout implementation of programmable ISM filter channel 300, according to aspects of the present disclosure. In this embodiment, programmable ISM filter channel 300 includes switches QI, Vds bias resistors Rb, control input VC, Resistors R, RF ports RF, input transmission lines Zl, grounded transmission lines Z2, coupling transmission lines Z3, resonator transmission line Z4, and capacitors Cl, C2+Cc, and C3. Alternative embodiments omit capacitor Cl.

[0133] In the illustrated embodiment, switches QI are each implemented in two parallel sections, each section being connected to capacitor Cl and ground, and each section being connected to control input VC through a separate resistor R. Alternative embodiments omit capacitor Cl, and the two parallel sections of QI are connected by a conductor. Vds bias resistors Rb may have relativelyDocket No. QID241640 / 62306.201W001large values (e.g., ~10kohm) and are connected between the source and drain of the switches QI, and are configured to bias the Vds of switches QI to 0 V.

[0134] Grounded transmission lines Z2 are connected to ground with Vias V. Because the grounded transmission lines Z2 are not constrained to be edge coupled to other transmission lines, the vias V can be isolated, as illustrated, by having a significant gap therebetween. As illustrated, the coupling transmission lines Z3 have a length, and the vias V are spaced apart by a distance greater than two times the length of coupling transmission lines Z3. Furthermore, in this embodiment, the vias V are spaced apart by a distance greater than two times the length of coupling transmission lines Z3 plus a length of the transmission line Z4.

[0135] Figure 8 illustrates a layout diagram of a programmable ISM filter 800, according to aspects of the present disclosure. ISM filter 800 is a layout implementation of ISM filter 100. ISM filter 800 has six instantiations of ISM filter channel 300, each having a different frequency. The six instantiations of ISM filter channel 300 illustrate beneficial variations in layout features and aspects. The size of this MMIC is 4.0mm x 2.1mm = 8.4 mm2, a more than 2.2x reduction in die area when compared with an ISM filter having equivalent ISM filter channels with edge coupled transmission lines, such as ISM filter channel 100.

[0136] Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly, and in a manner consistent with the present disclosure.

Claims

Docket No. QID241640 / 62306.201W001CLAIMS1. A radio frequency (RF) intrinsically switched multiplexing (ISM) filter, comprising:a plurality of parallel filter channel circuits, each filter channel circuit comprising: first and second switches;a control input node connected to the first and second switches, and configured to receive a control signal;first and second RF ports;first and second microstrip input transmission lines respectively connected to the first and second RF ports; anda plurality of additional microstrip transmission lines connected to the first and second switches and connected to the first and second input transmission lines, wherein a conductivity state of the first and second switches is determined by the control signal,wherein, in response to the first and second switches having a first conductivity state, an RF signal transfer function between the first and second RF ports has a bandpass characteristic, andwherein, in response to the first and second switches having a second conductivity state, the RF signal transfer function between the first and second RF ports has an all stop characteristic,wherein the bandpass characteristic of a first filter channel circuit is different from the bandpass characteristic of a second filter channel circuit.

2. The filter of claim 1, wherein the additional microstrip transmission lines comprise:first and second microstrip grounded transmission lines (Zs) connected to a ground plane, and respectively connected to the first and second input transmission lines;first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines; andfirst and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.Docket No. QID241640 / 62306.201W0013. The filter of claim 2, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, wherein the first via is electromagnetically isolated from the first coupling transmission line, wherein the second via is electromagnetically isolated from the second coupling transmission line, and wherein the first via is electromagnetically isolated from the second via.

4. The filter of claim 2, wherein the additional microstrip transmission lines comprise a microstrip resonator transmission line connected to each of the first and second microstrip coupling transmission lines.

5. The filter of claim 2, wherein the first and second grounded transmission lines have a first geometry, wherein the first and second coupling transmission lines have a second geometry, wherein the first and second geometries cause:the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines, and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

6. The filter of claim 2, wherein the first and second coupling transmission lines have a first length, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and wherein the first and second vias are spaced apart by a distance greater than two times the first length.

7. The filter of claim 2, wherein at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and wherein at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

8. A method of using a radio frequency (RF) intrinsically switched multiplexing (ISM) filter, the method comprising:providing a plurality of control signals to a plurality of parallel filter channel circuits to select between a bandpass characteristic and an all block characteristic for each of the filter channel circuits, wherein the bandpass characteristic of a first filter channel circuit is differentDocket No. QID241640 / 62306.201W001from the bandpass characteristic of a second filter channel circuit, and wherein each filter channel circuit comprises:first and second microstrip input transmission lines respectively connected to first and second RF ports, anda plurality of additional microstrip transmission lines connected to the first and second input transmission lines; andtransmitting an RF signal from the first RF port to the second RF port through the filter channel circuits, wherein a frequency transfer function of the filter channel circuits is determined by the control signals.

9. The method of claim 8, wherein the additional microstrip transmission lines comprise:first and second microstrip grounded transmission lines connected to a ground plane, and respectively connected to the first and second input transmission lines;first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines; andfirst and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.

10. The method of claim 9, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, wherein the first via is electromagnetically isolated from the first coupling transmission line, wherein the second via is electromagnetically isolated from the second coupling transmission line, and wherein the first via is electromagnetically isolated from the second via.

11. The method of claim 9, wherein the additional microstrip transmission lines comprise a microstrip resonator transmission line connected to each of the first and second microstrip coupling transmission lines.

12. The method of claim 11, wherein the first and second grounded transmission lines have a first geometry, wherein the first and second coupling transmission lines have a second geometry, wherein the first and second geometries cause:Docket No. QID241640 / 62306.201WO01the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines, and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

13. The method of claim 10, wherein the first and second coupling transmission lines have a first length, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and wherein the first and second vias are spaced apart by a distance greater than two times the first length.

14. The method of claim 9, wherein at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and wherein at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

15. A wireless device, comprising:first and second radio frequency (RF) circuits;an intrinsically switched multiplexing (ISM) filter configured to receive an RF signal from the first RF circuit, and to transmit a filtered RF signal to the second RF circuit, the ISM filter comprising:a plurality of parallel filter channel circuits, each filter channel circuit comprising:first and second switches;a control input node connected to the first and second switches, and configured to receive a control signal;first and second RF ports;first and second microstrip input transmission lines respectively connected to the first and second RF ports; anda plurality of additional microstrip transmission lines connected to the first and second switches and connected to the first and second input transmission lines,Docket No. QID241640 / 62306.201WO01wherein a conductivity state of the first and second switches is determined by the control signal,wherein, in response to the first and second switches having a first conductivity state, an RF signal transfer function between the first and second RF ports has a bandpass characteristic, andwherein, in response to the first and second switches having a second conductivity state, the RF signal transfer function between the first and second RF ports has an all stop characteristic,wherein the bandpass characteristic of a first filter channel circuit is different from the bandpass characteristic of a second filter channel circuit.

16. The wireless device of claim 15, wherein the additional microstrip transmission lines comprise:first and second microstrip grounded transmission lines (Zs) connected to a ground plane, and respectively connected to the first and second input transmission lines;first and second coupling capacitances respectively connected to the first and second input transmission lines and respectively connected to the first and second grounded transmission lines; andfirst and second microstrip coupling transmission lines respectively connected to the first and second input transmission lines by the first and second coupling capacitances, and respectively connected to the first and second grounded transmission lines by the first and second coupling capacitances.

17. The wireless device of claim 16, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, wherein the first via is electromagnetically isolated from the first coupling transmission line, wherein the second via is electromagnetically isolated from the second coupling transmission line, and wherein the first via is electromagnetically isolated from the second via.

18. The wireless device of claim 16, wherein the first and second grounded transmission lines have a first geometry, wherein the first and second coupling transmission lines have a second geometry, wherein the first and second geometries cause:Docket No. QID241640 / 62306.201WO01the first grounded transmission line, a portion of the first coupling capacitance, and the first coupling transmission line to form a first equivalent circuit which is functionally equivalent to a reference circuit having first and second coupled transmission lines, and the second grounded transmission line, a portion of the second coupling capacitance, and the second coupling transmission line to form a second equivalent circuit which is functionally equivalent to the reference circuit.

19. The wireless device of claim 16, wherein the first and second coupling transmission lines have a first length, wherein the first and second grounded transmission lines are respectively connected to the ground plane by first and second vias, and wherein the first and second vias are spaced apart by a distance greater than two times the first length.

20. The wireless device of claim 16, wherein at least a portion of the first grounded transmission line is perpendicular to the first coupling transmission line, and wherein at least a portion of the second grounded transmission line is perpendicular to the second coupling transmission line.

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