Integrated switching element and programmable filter

Abstract

Integrated circuit element (500) which features: a first conductive winding (510) on a first layer in a first direction, wherein the first winding has an intermediate tap (450), and a second conductive winding (520) on a second layer in a second direction, wherein one terminal of the second winding is electrically connected to the intermediate tap (450).

Description

TECHNICAL AREA

[0001] This application concerns the field of signal filtering and in particular a programmable filter. BACKGROUND

[0002] In electronics design, the reactive impedance of inductors and capacitors is used to create filters, including low-pass, high-pass, band-pass, and band-stop filters. The cutoff frequency of a low-pass or high-pass filter, the passband of a band-pass filter, and the stopband of a band-stop filter depend on the values ​​of capacitors and inductors, which are selected according to principles well known in the art. However, filters do not provide perfect linear cutoff at their passbands, stopbands, and cutoff frequencies. Instead, they exhibit a roll-off rate, expressed in decibels per decade on a logarithmic scale. For example, the characteristic roll-off for a first-order filter is generally about -20 dB / decade.The roll-off rate can be significantly increased by adding further stages to the filter to create a higher-order filter. For example, a fifth-order filter can achieve a roll-off rate of approximately -100 dB / decade.

[0003] US 2012 / 0314811 A1 discloses devices and methods for manufacturing a broadband RF mixer. The mixer has an input, an output, and an input for a local oscillator. A variable impedance is arranged in an input signal path between the input terminal and the mixer, and a variable impedance is arranged in an output signal path between the output and the mixer. The impedances of the variable impedances are controllable for a specific operating frequency by one or more digital or analog control signals.

[0004] DE 699 730 594 T2 discloses a programmable filter bank with an input for receiving an input signal, an output for sending a filtered output signal, and a group of interconnected, individually selectable filter elements, each filter element providing a predefined fixed frequency response. A control unit is connected to the filter elements and allows a user to select one or more filter elements to generate a desired overall frequency response.

[0005] US 8,422,977 B2 discloses a programmable filter for an RF receiver, wherein the filter has an input, a filtered output, and a plurality of filter paths arranged in parallel between the input and the output. Each filter path has a buffer arranged between an input and multiphase filters, and each filter path is individually selectable.

[0006] US patent 7,259,643 B2 discloses an adjustable wide-range bandpass filter that can digitally modify the center frequency and bandwidth of a signal being filtered. The filter incorporates multiple switched capacitor banks and inductors to convert the signal portion into a digital signal according to the filter's center frequency and bandwidth. These elements can be integrated on a single chip.

[0007] US 7,598,838 B2 discloses that an integrated variable inductor is achieved by placing a secondary closed-loop inductor directly above or below a primary inductor. The configuration of the second closed-loop inductor can be interrupted on the chip in various ways, including the use of a transistor to selectively short-circuit both ends of the secondary inductor.

[0008] US 7,460,001 B2 shows that a variable inductor can be formed on an integrated circuit with a primary conductor, a secondary conductor, and a switch. The primary conductor forms an inductor and can be configured in various patterns. The secondary conductor forms a loop close to the primary conductor. The switch is connected in series with the secondary conductor and opens or closes the loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure is best understood with the aid of the following detailed description, when read in conjunction with the accompanying figures. It is emphasized that, in accordance with industry practice, various features are not drawn to scale and are used for illustrative purposes only. In fact, the dimensions of various features may be enlarged or reduced as desired for the sake of clarity of discussion. Fig. Figure 1 is a block diagram of an example integrated circuit with a programmable filter. Fig. Figure 2 is an electrical circuit diagram of a programmable fifth-order differential filter with variable inductors and capacitors. Fig. Figure 3 is an electrical circuit diagram of an example network with variable capacitance. The Fig.4A-4E are electrical circuit diagrams of an exemplary network with variable inductance in different states. Fig. Figure 5 is a view of a variable inductance network suitable for use in an integrated circuit. DETAILED DESCRIPTION OF THE EXECUTION FORMS OVERVIEW

[0010] In an exemplary embodiment, a variable inductor is disclosed, comprising a primary inductor with a first terminal, a second terminal, and an intermediate tap; a secondary inductor with a first terminal connected to the intermediate tap of the primary inductor and a second terminal; a first switch connected between the first terminal of the primary inductor and the second terminal of the secondary inductor, and a second switch connected between the second terminal of the primary inductor and the second terminal of the secondary inductor, whereby the total inductance can be varied by opening one or both switches, and the variable inductor can be bypassed by closing both switches.

[0011] In another exemplary embodiment, a programmable filter is disclosed comprising a variable-capacitance network having a plurality of capacitors and a capacitance switch for selecting between at least two available capacitances; a variable-inductance network having a plurality of inductors and an inductance switch for selecting between at least two available inductances, whereby a passband can be selected by choosing an available capacitance and an available inductance.

[0012] In yet another exemplary embodiment, an integrated circuit element is disclosed which has a first conductive winding on a first layer in a first direction, wherein the first winding has an intermediate tap; a second conductive winding on a second layer in a second direction, wherein a terminal of the second winding is electrically connected to the intermediate tap. DESCRIPTION OF EXAMPLE FORMS OF EXECUTION

[0013] The present disclosure provides numerous different embodiments, or examples, for realizing various features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Furthermore, reference numerals and / or letters may be repeated in the various examples in the present disclosure. This repetition serves the purpose of simplicity and clarity and is not intended to imply any relationship between the various embodiments and / or configurations discussed. Different embodiments may have different advantages, and no specific advantage is necessarily required for any particular embodiment.

[0014] In an exemplary embodiment, this description discloses a filter with a programmable passband. Programmability is achieved by providing a network of variable capacitors and variable inductors. The variable inductors can be implemented as part of an integrated circuit and can comprise a plurality of inductors with known inductances in a Y-configuration. Solid-state switches can be provided to selectively bypass certain inductors or to change their mutual inductances. In an example with three inductors controlled by two switches, each variable inductor is provided with three discrete inductances and a bypass mode.This configuration can be realized in silicon by, for example, providing a primary winding with several turns and a relatively narrow trace line, and a secondary winding at an intermediate tap of the primary winding, where the secondary winding is wider and has only one turn.

[0015] Fig. Figure 1 is a block diagram of an exemplary integrated circuit (IC) 100, which is only one of numerous circuit types that can be constructed according to the present description. The IC 100 includes a digital-to-analog converter (DAC) 130 configured to receive a digital input signal and output a corresponding analog signal. In one exemplary embodiment, the DAC 130 supplies an analog output signal 132 to the modulator 120, which may, for example, be part of a data transmission circuit.

[0016] In the exemplary integrated circuit 100, the modulator 120 does not generate a DC current, but instead presents a high-impedance load. A differential resistor 124 is placed across the input terminals as a filter termination, but does not affect the DC current. Therefore, the current through resistor 150-1 is generated exclusively by the DC current 132 (midrange) from the DAW 130, in this exemplary case 10 mA through a 50 Ω resistor 150-1, which results in 0.5 V across resistor 150-1, flowing to ground 190.

[0017] The DAW 130 generates a complementary output current 132, 134 between 0 mA and 20 mA, with a common-mode current (mid-range) of 10 mA. This common-mode current generates a common-mode voltage Vcm through the series resistors 150. In this case, the 10 mA current through the 50 Ω resistors 150 generates a common-mode voltage of 0.5 V. The modulator 120 presents a high-impedance input, so the differential resistor 124 terminates the output of the filter 110 without affecting the DC current or voltage.

[0018] In some cases, it is desirable to program the programmable low-pass filter 110 with a variety of selectable passbands. For example, in this embodiment, if the DAW 130 has selectable sampling rates for different signal bandwidths in data transmission or other similar applications, programmable cutoff frequencies can be used.

[0019] Fig. Figure 2 is an electrical circuit diagram of an exemplary embodiment of a programmable differential low-pass filter 110. It should be noted that, although a low-pass filter is disclosed as an exemplary embodiment, similar techniques can be used to design other filter types, such as high-pass filters, band-pass filters, and band-stop filters. In this embodiment, the programmable low-pass filter 110 provides a fifth-order low-pass filter with a classic symmetrical conductor topology, except that the capacitors C1, C2, C3, C4, C5, and C6, along with the inductors L1, L2, L3, and L4, can all be variable. In this exemplary embodiment, the variable capacitors C and the variable inductors L are discretely variable rather than continuously, with discrete values ​​controlled by switches, as also shown in the Fig. 3 and Fig.4 is disclosed. In an exemplary embodiment, C1 and C4 are coupled to a common controller such that they have an equivalent value, as described in more detail below. Similarly, C2 can be coupled to C5, and C3 can be coupled to C6.

[0020] Fig. Figure 3 is an electrical circuit diagram of an exemplary embodiment of a network 300 with variable capacitance, which in some embodiments uses a variable capacitor C instead of each variable capacitor C. Fig.2. The variable-capacitance network 300 includes a positive terminal 302 and a negative terminal 304, where the designations "positive" and "negative" are arbitrary for bidirectional capacitors. In cases where directional capacitors such as electrolytic capacitors are used, the designations "positive" and "negative" may be prescriptive. Furthermore, although an input terminal 302 is conventionally shown as a "signal" voltage and an output terminal 304 is conventionally shown as a "ground" terminal, any two suitable terminals that provide a potential difference may be used.

[0021] It should be noted that although this exemplary circuit is revealed as a single-ended configuration, it can easily be replaced by a differential configuration.

[0022] This embodiment comprises three discrete stages 350. The first stage 350-1 includes two capacitors 320-1, 320-2 and two selector switches 310-1, 310-2. In this embodiment, the selector switches 310 are electronic semiconductor switches, such as MOSFETs, which can be implemented as part of an integrated circuit. However, it should be noted that in other embodiments, the selector switches 310 can be other types of switches, including micro-electromechanical switches, electromechanical relays, or manual mechanical switches. Furthermore, in this embodiment, the switches 310 are functionally coupled (paired) such that both are either selected or unselected, for example, because they receive a common input. This can be done, for example, to maintain a symmetrical arrangement in an integrated circuit.However, it should be noted that additional detail in the capacity control can be achieved by making the 320 selection switches independently selectable from each other.

[0023] In this embodiment, when the coupled selector switches 310-1 and 310-2 are open, the first stage 350-1 is bypassed. When the coupled selector switches 310-1 and 310-2 are closed, the first stage 350-1 provides a capacitance equal to the sum of capacitors 320-1 and 320-2.

[0024] Similarly, the second stage 350-2 is controlled by the coupled selector switches 310-3 and 310-4, which, when open, bypass the second stage 350-2, and, when closed, provide a capacitance equal to the sum of capacitors 320-3 and 320-4. The third stage 350-3 is controlled by the coupled selector switches 310-5 and 310-6, which, when open, bypass the third stage 350-3, and, when closed, provide a capacitance equal to the sum of capacitors 320-5 and 320-6.

[0025] Therefore, by actuating the three pairs of selector switches, up to seven discrete operating capacitances and one bypass mode (“000” when all three pairs of selector switches are open) are provided. If, on the other hand, the selector switches 310 are coded in a monotonic Gray code (000, 001, 011, 111), up to three discrete operating capacitances and one bypass mode are provided. If completely independent selector switches 310 are provided, up to 31 operating capacitances and one bypass mode are provided, or up to five operating capacitances and one bypass mode with a monotonic Gray code. In each case, the total capacitance provided by the variable-capacitance network 300 is the linear sum of all non-bypassed capacitors 320.It should be noted that other arrangements are also possible, in which case the total capacity can be regulated by a ratio other than a linear sum according to methods that are well known in the art.

[0026] Fig. Figure 4 is an electrical circuit diagram of an exemplary embodiment of a network 400 with variable inductance, which in some embodiments uses a variable inductor L instead of each variable inductor. Fig. 2 can be used. The network 400 with variable inductance includes three inductors 420, which are controlled by selector switches 410, which are of the same type as the selector switches 310 ( Fig.3) may be. In this embodiment, the first inductor 420-1 is placed in series with the second inductor 420-2, and a positive node 430 and a negative node 440 are shown. It should be noted that “positive” node and “negative node” can be arbitrary designations for a generic inductor, but may be prescriptive in certain arrangements of inductors where specific electromagnetic properties are desired.

[0027] The first inductor 420-1 and the second inductor 420-2 are connected at an intermediate tap 450. The intermediate tap 450 can represent a connection where terminals of two discrete inductors are joined, or it can represent a "true" center or a "true" intermediate tap of a single inductor, wherein the first inductor 420-1 and the second inductor 420-2 are formed from a single conductive winding that is "tapped" at an intermediate point, which may or may not be the mathematical or geometric center of the winding. A conductor may be electrically connected to the intermediate tap to provide a conductive path to other circuit elements. A third inductor 420-3, sometimes called a secondary or auxiliary inductor, also has a terminal connected to the intermediate tap 450, its second terminal being located at a node 460.The first selection switch 410-1 is connected between the input nodes 430 and the nodes 460, while the second selection switch 410-2 is connected between the output nodes 440 and the nodes 460.

[0028] With the help of Fig. Figure 4A provides an alternative embodiment in which the selector switches 410 are shown as mechanical switches. It should be noted that numerous other switch types can be used. Fig. 4B provides the equivalent circuit for the variable-inductance network 400 when both selector switches 410 are open. In this case, the third inductor 420-3 is "floating," and its inductance therefore does not contribute to the network. The total inductance of the network is the linear sum of inductors 420-1 and 420-2, plus any mutual inductance between them, as indicated by the dotted lines.

[0029] In Fig. 4C provides the equivalent circuit for the network 400 with variable inductance when the first selector switch 410-1 is open and the second selector switch 410-2 is closed. In this case, the third inductor 420-3 is connected in parallel with the second inductor 420-2 and in series with the first inductor 420-1. The total inductance of the network can then be described by the following equation: Leq1=Lnom−(L2+k12L1L2−k13L1L3−k23L2L3)2L2+L3−2k23L2L3

[0030] Where L nom the nominal inductance of the path L1 - L2, with L3 open. Lnom=L1+L2+2k12L1L2.

[0031] In Fig.4D provides the equivalent circuit for the network 400 with variable inductance when the first selector switch 410-1 and the second selector switch 410-2 are closed. In this case, the first inductor 420-1 and the third inductor 420-3 are connected in parallel and in series with the second inductor 420-2. The total inductance of the network can then be described by the following equation: Leq2=Lnom−(L1+k12L1L2+k13L1L3+k23L2L3)2L1+L3+2k13L1L3

[0032] From these equations, based on the desired L1, L2 and L3, as well as k, it is possible to calculate 12 , k 13 and k 23 An inductor geometry is developed that offers three different effective inductance values ​​(L). nom , L eq1 and L eq2 ).

[0033] In Fig.4E provides the equivalent circuit for the network 400 with variable inductance when both selector switches 410 are closed. In this case, the inductors are completely bypassed, so the equivalent inductance is zero.

[0034] Fig. Figure 5 is a top view of an exemplary integrated circuit element 500, through which the network 400 with variable inductance consists of Fig.4 is realized. The integrated circuit element 500 can be realized according to techniques known in the prior art, for example, using conventional silicon-based processes. In this embodiment, two windings are disclosed; the first winding 510 forms the first inductor 420-1 and the second inductor 420-2, while the second winding 520 forms the third inductor 420-3. In this embodiment, the first winding 510 has a plurality of turns, while the second winding 520 has a single turn. The first winding 510 and the second winding 520 can be located on separate layers of the inter-metal dielectric, so that the windings do not short-circuit electrically.

[0035] In this embodiment, the first winding 510 winds in a clockwise direction from the input node 430 to the output node 440. The output node 440 can be formed on a layer separate from the layer for the first winding 510 to prevent a short circuit with the first winding 510. This layer can be the same or a different layer than the layer for the second winding 520.

[0036] The second winding 520 is formed on a layer separate from the layer for the first winding 510 and, in this embodiment, is essentially concentric with the first winding 510. Since it is simpler for practical reasons to limit the second winding 520 to a single turn, the outer diameter of the second winding 520 can be significantly larger than that of the first winding 510, thus generating a greater inductance from a single turn. In this case, however, mutual coupling can be reduced because the two windings are physically further separated. In this embodiment, the second winding 520 winds in a counterclockwise direction from the node 460 to the intermediate tap 450, which can be formed, for example, by a via connection between the two layers. It should be noted that in the Fig.In the exemplary embodiment disclosed in Figure 5, the magnetic coupling between the third inductor 420-3 and the first inductor 420-1 is stronger than the magnetic coupling between the third inductor 420-3 and the second inductor 420-2. This is because, in this embodiment, the second winding 520 follows the outer section of the first winding 510 at a closer distance than the inner section. However, in another design, where a strong magnetic coupling of the second inductor 420-2 with the third inductor 420-3 is more desirable, the second winding 520 can be wound more closely around the inner section of the first winding 510.

[0037] It should be noted that some capacitive coupling, along with other forms of undesirable parasitism, may occur between the first winding 510 and the second winding 520. In some embodiments, additional design work may be required to compensate for such parasitism.

[0038] In some embodiments, the integrated circuit element 500 may be only one part of a much larger integrated circuit that includes both analog and digital components, such as the integrated circuit 100. Since analog components are relatively large, it is desirable to minimize the number of individual analog components. Therefore, for example, when constructing a network of selectable inductors, it may be desirable to use a compact integrated circuit element such as the integrated circuit element 500 instead of three separately connected inductors for each variable inductor L. Fig.2 to build.

[0039] In an exemplary embodiment, a fifth-order low-pass filter is used according to the schematic representation. Fig. 2 constructed, using the variable capacitors from Fig. 3 and the variable inductors from Fig. 4. In this example, a binary code is used to choose between three passbands as follows: Cutoff frequency mode Capacitor Vausw Inductor Vausw bypass 0 000 11 500 MHz 1 001 10 300 MHz 2 011 01 225 MHz 3 111 00

[0040] In this example, capacitor networks are selected according to a monotonic Gray code, and an inductance mode is assigned to each capacitance mode. A bypass mode is provided when all capacitor selector switches are open and both inductor selector switches are closed. Suitable capacitance and inductance values ​​for each capacitor 320 and each inductor 420 can be chosen to achieve these exemplary passbands. For example, a Chebyshev low-pass filter with 0.25 dB ripple in a 100-ohm system can be constructed with Y1 = 10 pF, Z2 = 93 nH, Y3 = 16 pF, Z4 = 93 nH, and Y5 = 10 pF, where "Zn" and "Yn" represent the five reactive impedance and susceptive admittance elements of a classical Chebyshev filter, respectively. In this embodiment, Y1, Y3, and Y5 are capacitors, while Z2 and Z4 are inductors.This provides a cutoff frequency at 225 MHz with a roll-off of approximately -100 dB / decade.

[0041] In the foregoing, various embodiments have been highlighted to enable those skilled in the art to better understand the aspects of this disclosure. Those skilled in the art should note that they can easily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or obtain the same advantages as the embodiments introduced herein. They should also recognize that such equivalent designs do not deviate from the meaning and scope of this disclosure, and that they can make various changes, substitutions, and modifications to them without deviating from the meaning and scope of this disclosure.

[0042] In discussing the foregoing embodiments, all of the capacitors, buffers, graphic elements, interconnect boards, clock generators, sensors, dividers, inductors, resistors, amplifiers, switches, digital cores, transistors, and / or other components can be easily replaced, exchanged, or otherwise modified to meet specific circuit design needs. Furthermore, it should be noted that the use of complementary electronic devices, hardware, non-volatile software, etc., provides an equally viable option for realizing the teachings of this disclosure.

[0043] In one exemplary embodiment, any number of electrical circuits from the FIGURES can be implemented on a circuit board of an associated electronic device. The circuit board can be a conventional printed circuit board (PCB) that incorporates various components of the electronic device's internal electronic system and can also provide connections for other peripherals. More precisely, the circuit board can provide the electrical connections by which the other components of the system can communicate electrically with one another. Any suitable processors (including digital signal processors, microprocessors, supporting chipsets, etc.), memory elements, etc., can be appropriately connected to the circuit board based on specific configuration needs, processing requirements, computer designs, etc.Other components, such as external storage, additional sensors, audio / video playback controllers, and peripherals, can be connected to the circuit board as plug-in cards, via cables, or integrated into the board itself. In another exemplary embodiment, the electrical circuits shown in the figures can be implemented as standalone modules (e.g., a device with associated components and circuits configured to perform a specific application or function) or as plug-in modules for application-specific hardware of electronic devices.

[0044] It should be noted that in the numerous examples presented here, an interaction may be described in relation to two, three, four, or more electrical components. However, this was done solely for the purpose of clarity and illustration. It should be noted that the system can be consolidated in any suitable manner. Within the framework of similar design alternatives, any of the illustrated components, modules, and elements from the FIGURES can be combined in various possible configurations, all of which clearly fall within the broad scope of this description. In certain cases, it may be simpler to describe one or more of the functionalities of a given set of processes by referring only to a limited number of electrical elements.It should be noted that the electrical circuits from the FIGURES and their teachings are easily scalable and can be adapted to a large number of components as well as more complex / demanding arrangements and configurations. Consequently, the examples given are not intended to limit the scope of protection or hinder the far-reaching teachings of the electrical circuits as they can potentially be applied to countless other architectures.

[0045] Numerous other modifications, substitutions, variations, alterations, and modifications may be ascertainable by those skilled in the art, and it is intended that the present disclosure shall include all such modifications, substitutions, variations, alterations, and modifications as falling within the scope of protection of the appended claims. To assist the United States Patent and Trademark Office (USPTO) and, moreover, all readers of any patent granted on this application in interpreting the claims appended herein, the applicant wishes to state that the applicant: (a) does not intend that any of the appended claims shall violate paragraph six(6) of 35 USCSection 112 is claimed as it exists on the date of filing this document, unless the terms “means for / to” or “steps for / to” are expressly used in the specific claims, and (b) is not intended by any statement in the description to limit this disclosure in any way that is not also expressed in the attached claims.

Claims

[1] Integrated circuit element (500) comprising: a first conductive winding (510) on a first layer in a first direction, the first winding having an intermediate tap (450), and a second conductive winding (520) on a second layer in a second direction, wherein a terminal of the second winding is electrically connected to the intermediate tap (450). [2] The integrated circuit element of claim 1, wherein the first winding (510) and the second winding (520) are substantially concentric with each other. [3] Integrated circuit element according to claim 1 or 2, wherein the second winding has only a single turn. [4] Integrated circuit element according to one of claims 1 to 3, wherein the second direction is opposite to the first direction. [5] Integrated circuit element according to one of claims 1 to 4, wherein: the first winding (510) further comprises a first terminal (430) and a second terminal (440), the second winding (520) further comprises a second terminal (460), and also comprising: a first switch (410-1) connected between the first terminal of the first winding and the second terminal of the second winding, and a second switch (410-2) connected between the second terminal of the first winding and the second terminal of the second winding, whereby a first inductance is selectable by opening both switches, a second inductance is selectable by closing only the first switch, a third inductance is selectable by closing only the second switch, and a bypass mode is selectable by closing both switches. [6] An integrated circuit comprising a programmable filter in which the integrated circuit element according to claim 5 is incorporated as a variable inductor. [7] The integrated circuit of claim 6, further comprising a variable capacitor. [8] Programmable filter (110) comprising: a variable capacitance network (300) comprising a plurality of capacitors (320) and a capacitance switch (310) for selecting between at least two available capacitances; a variable inductance network (400) comprising a plurality of inductors (420) and an inductance switch (410) for selecting between at least two available inductances, the variable inductance network (400) comprising an integrated circuit element (500) according to any one of claims 1 to 5, wherein a first inductor (420-1) of the plurality of inductors (420) is formed by the first conductive winding (510) and a second inductor (420-2) of the plurality of inductors (420) is formed by the second conductive winding (520), whereby a passband can be selected by selecting an available capacitance and an available inductance. [9] A programmable filter according to claim 8, wherein the variable capacity network (300) comprises: three variable capacitor stages (350), each variable capacitor stage having: a first capacitor (320-1) and a first capacitance switch (310-2), connected in parallel with a second capacitor (320-2) and a second capacitance switch (310-1), wherein the first and second capacitance switches are coupled to each other, whereby a capacitance can be selected by closing the first and second capacitance switches according to a monotonic Gray code. [10] A programmable filter according to claim 8 or 9, wherein the variable inductance network (400) comprises: the first inductor (420-1) having a first terminal and a second terminal; the second inductor (420-2) having said first terminal and a second terminal, wherein the second terminal of the first inductor and the first terminal of the second inductor are connected to the intermediate tap (450); a third inductor (420-3) having a first terminal and a second terminal connected to the intermediate tap (450) and an inductance switch (410-1) connected between the second terminal of the third inductor and the first terminal of the first inductor, whereby a first inductance is selectable by closing the inductance switch, and a second inductance is selectable by opening the inductance switch. [11] The programmable filter of claim 10, wherein the variable inductance network (400) further comprises a second inductance switch (410-2) connected between the second terminal of the third inductor and the second terminal of the second inductor, whereby a third inductance is selectable by closing only the second inductance switch and a fourth inductance is selectable by closing both inductance switches. [12] A programmable filter according to claim 8, wherein the programmable filter is implemented in an integrated circuit and further comprises: a second and third variable capacity network, each capacity network having a first and second terminal (302, 304); a second, third and fourth variable inductance network, each variable inductance network having a first and second terminal (430, 440); where: the first terminal of the first capacitance network is connected to the first terminal of the first inductance network, and the second terminal of the first capacitance network is connected to the first terminal of the second inductance network; the first terminal of the second capacitance network is connected to the second terminal of the first inductance network and the first terminal of the third inductance network, and the second terminal of the second capacitance network is connected to the second terminal of the second inductance network and the first terminal of the fourth inductance network, and the first terminal of the third capacitance network is connected to the second terminal of the third inductance network and the second terminal of the third capacitance network is connected to the second terminal of the fourth inductance network.

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