Dis-engaging test point

A test point circuit includes a main RF signal path (e.g., transmission line, lumped-element network, etc.), a test point RF signal circuit, a test point structure having a center conductor and corresponding grounded sleeve and being configured for connecting to a test probe for monitoring the RF signal carried through the main RF signal path, and a switch between the main RF signal path and the test point RF signal circuit. In the open position of the switch, the signal in the main RF signal path is prevented from propagating to the center conductor of the test point structure. In the closed position of the switch, the RF signal can propagate from the main RF signal path to the center conductor of the test point structure. The test probe mated to the test point structure can then measure or monitor the RF signal carried through the main RF signal path.

TECHNICAL FIELD

The present subject matter relates to electronic Radio Frequency (RF) signal path test point circuitry for cable television equipment that is capable of being disengaged from the RF signal path when not in use.

BACKGROUND

Broadband and hybrid fiber coax (HFC) equipment commonly employ RF test points for monitoring signals propagated through an RF signal path. RF test points are typically connected to a directional coupler that is connected to the main RF signal path. The main RF signal path may be a transmission line, lumped-element network, etc. A directional coupler is normally used to (i) direct most of the signal power to the main RF signal path, and (ii) direct a limited amount of the signal power to the RF test point (or any another circuit). A user can monitor the limited power version of the RF output signal by connecting measuring equipment via a probe to the test point.

The signal power directed to the main RF signal path incurs an undesired amount of loss as a result of the directional coupler. This undesirable loss associated with the directional coupler is incurred at all times during operation of the equipment despite the fact that the RF test point may be used infrequently (e.g., annually). It would be desirable to minimize the amount of loss incurred in the main RF signal path while providing a user the capability to monitor the main RF signal path using the RF test point.

SUMMARY

An example of a test point circuit includes a main RF signal path for carrying an RF signal, an electronic or electro-mechanical or mechanical switch coupled to the main RF signal path and coupled to a test point circuit, a test point circuit, and a test point structure having a center conductor and corresponding grounded sleeve and being configured for connecting to a test probe for monitoring the RF signal carried through main RF signal path. In the open position of the switch, the RF signal from the main RF signal path is prevented from being carried to the center conductor of the test point structure, and, in a closed position of the switch, the RF signal from the main RF signal path propagates to the test point center conductor such that the test probe mated to the test point structure can monitor the signal carried through the main RF signal path.

Another example of a dis-engaging test point circuit includes a main RF signal path, a main RF signal path for carrying an RF signal, and a test point structure having a center conductor and corresponding grounded sleeve which is configured for connecting to a test probe for monitoring the RF signal carried through the main RF signal path, a switch coupled to the main RF signal path and coupled to a test point circuit, and a test point structure. In an open position of the switch, the RF signal is prevented from being carried from the main RF signal path to the test point center conductor, and, in a closed position of the switch, the RF signal propagates from the main RF signal path to the test point center conductor such that the test probe connected to the test point center conductor can monitor the RF signal carried through the main RF signal path. Means for detecting the presence of the test probe are mounted to the test point structure. The detecting means transmits a control signal to the switch, and wherein the control signal is configured to close the switch when the detecting means detects the presence of the test probe being mated to the test point structure.

Another example of a dis-engaging test point circuit provides a method of monitoring an RF signal carried through a main RF signal path using a test point structure that is connected to the main RF signal path through a switch and test point circuit. The method includes detecting the presence of a test probe mated to the test point structure; and upon detection, controlling the state of a switch in a test point circuit from an open state to a closed state, which connects the main RF signal path to the center conductor of the test point structure, thereby directing the RF signal from the main RF signal path through the test point circuit and to the test point center conductor.

It should be understood that the features inFIGS. 3-10are shown schematically, and features which would be ordinarily obscured by other features are still shown.

DETAILED DESCRIPTION

FIG. 1depicts a conventional circuit100incorporating a directional coupler and two RF test points. More particularly, the conventional circuit100generally includes a power amplifier102that amplifies a 52 MHz to 1000 MHz forward path signal into a highband “H” port106of a diplex filter104. The diplex filter104outputs the forward path signal into a main RF signal path108.

Forward and return path signals are transmitted through the main RF signal path108. The forward path signals are propagated in a downstream direction (e.g., from device120to device109), whereas the return path signals are propagated in an upstream direction (e.g., from device109to device120).

The 5 MHz to 42 MHz return path signals travel from the main RF signal path108into the diplex filter104. The diplex filter104is configured to output the return path signals through the lowband “L” port116. A power amplifier118amplifies the return path signals output through the lowband “L” port116and into a line119connected to upstream device120.

A directional coupler110is coupled to the main RF signal path108. A forward path test point112is coupled to one port of the directional coupler110, and a return path test point114is coupled to another port of the directional coupler110. A user can monitor the forward path signal transmitted through the main RF signal path108using the forward path test point112. A user can also inject a signal or tone through the return path test point114, which is transmitted in an upstream direction into the diplex filter104and the line119toward the upstream device120. The signal or tone is monitored at a location upstream of the diplex filter104.

As discussed in the Background section, the signal power directed through the forward path of the main RF signal path108incurs an undesired amount of loss, e.g., on the order of 1 dB, as a result of the splitting effect of the directional coupler110. This undesirable loss is incurred at all times during operation of the equipment due to the circuitry of the directional coupler even though the forward path test point112may be used infrequently. In various applications a constant 1 dB loss is highly undesirable.

FIG. 2depicts a circuit200incorporating a standard directional coupler test point150, and a dis-engaging test point144. In contrast to the circuit100comprising the directional coupler110, the circuit200ofFIG. 2is configured to minimize the amount of loss incurred in the forward path of the main RF signal path108while providing a user the capability to monitor the forward and return path signals propagated through the main RF signal path using RF test points.

The primary differences between the circuits100and200are that the directional coupler110is replaced by a test point circuit130, and a directional coupler132is added to the return path line134upstream of the diplex filter104.

The test point circuit130is coupled to the main RF signal path108at a location downstream of the diplex filter104(as viewed in the forward path direction). The test point circuit130includes electrical lines, three impedance blocks136,140and142in a T or Y configuration coupled to the electrical lines, and a switch138coupled at the intersection of the impedance blocks136,140and142. The first impedance block136is coupled to the main RF signal path108. The second impedance block140is coupled to a forward path test point144. The third impedance block142is coupled to ground. The impedance blocks136,140and142may be resistors, for example.

In the open position (shown) of the switch138, the forward path signal in line108is prevented from reaching the test point144. In the closed position of the switch138, the forward path signal in line108propagates through the closed switch138to the test point144. A user can monitor the forward path signal propagated through the main RF signal path108by inserting a test probe into the test point144. The switch138is only closed when a user desires to monitor the forward path signal propagated through the main RF signal path108using the test point144. When the test point144is not in use, the switch138remains open, thereby averting a constant 1 dB loss (approximate) (as compared with the directional coupler110of the circuit100).

Thus, the switch138is maintained in the open position in normal operation; and, the switch138is only moved to the closed position when a user desires to monitor the forward path signal propagated through the main RF signal path108. It is noted that the loss incurred by the circuit130may only be 0.1 dB, for example, which is significantly less than the 1 dB loss incurred by the directional coupler110of the circuit100. The circuitry that controls the switch138is not shown inFIG. 2, however, it will be described with reference toFIG. 3(according to one example) andFIG. 7(according to another example).

The directional coupler132is coupled to the return path line134at a location downstream of the diplex filter104(as viewed in the return path direction, see arrow on line134). A return path test point150is coupled to the directional coupler132. A user can inject a signal or tone through the return path test point150through the main RF signal path134toward the upstream device120. The signal or tone is monitored at a location downstream of the directional coupler132(as viewed in the return path direction).

It should be understood that the downstream device109, upstream device120, the diplex filter104, the power amplifiers102and118, and the directional coupler132are optional components of the circuit200.

FIG. 3schematically depicts the interconnection between the test point144and the test point circuit130of the circuit200ofFIG. 2, according to one example.FIG. 4depicts a cross-sectional view of the test point144ofFIG. 3, which is shown schematically.

The test point144comprises a center conductor152, an annular sleeve154surrounding the center conductor152, and a conductive and resilient curved spring156that is positioned within a slot158defined in the sleeve154. The center conductor152is electrically coupled to the second impedance block140of the circuit130by the line153. The bottom end of the spring156is electrically coupled to switch control logic160by line157. The line157may be a ground trace. The switch control logic160, which may be considered as a relay switch circuit, is coupled to and controls the switch138. The switch control logic160may also be referred to herein as a linkage. The linkage may be electrical, electromechanical, or a mechanical circuit, for example. The spring156is at least partially positioned within the interior of the annular sleeve154. The center conductor152and the spring156of the test point144are each configured to interact with a standard RF test probe180, as will be described hereinafter.

The circuit200, or portions thereof, is bodily incorporated onto the printed circuit board161, and the circuit200is electrically coupled to both the conductor152and the spring156, as is shown inFIG. 3. The center conductor152and the spring156are mounted to separate traces on the board161. The center conductor152and the spring156are configured to interact with a standard RF test probe180, as will be described hereinafter.

FIG. 5depicts a connector180prior to mating with the test point144ofFIG. 3, andFIG. 6depicts the connector180mated with the RF test point ofFIG. 3. In operation, a user inserts the test probe180into the sleeve154of the test point144to monitor the forward path signal propagated through the main RF signal path108.

Prior to inserting the test probe180(as shown inFIG. 5), the switch control logic160senses that the spring156is not coupled to ground because the test probe180has not been inserted into the test point144and the logic160has not received a ground signal via line157. Accordingly, the switch control logic160maintains the switch138in the open position (as shown). In the open position (shown) of the switch138, the forward path signal in line108is prevented from reaching the center conductor152of the test point144, thereby averting a constant 1 dB loss (approximate) (as compared with the directional coupler110of the circuit100). This is the normal state of the test point144and the circuit200.

Upon inserting the test probe180into the sleeve154(as shown inFIG. 6), the spring clip182that is mounted to the exterior of the test probe180physically contacts and pushes outward the spring156, thereby electrically connecting the spring156to ground. Additionally, upon insertion of the test probe180, the center conductor152of the test point144physically connects to a female spring contact (not shown) embedded within the test probe180. When the switch control logic160senses that the spring156is grounded (i.e., when it receives a ground signal from line157), the switch control logic160closes the switch138(which is shown open inFIG. 3). In the closed position of the switch138, the forward path signal in line108propagates through the closed switch138to the center conductor152of the test point144via line153. The test probe180then receives the forward path signal in line108via the connection between the male center conductor152and the female spring contact in the test probe180. The test probe180is connected to equipment (not shown) for monitoring the forward path signal in line108.

FIG. 7depicts the interconnection between a test point structure202and the test point circuit130of the circuit200ofFIG. 2, according to another example.FIG. 8depicts a cross-sectional view of the test point structure202ofFIG. 7, which is shown schematically. The test point structure202is similar to the test point structure144ofFIG. 4and only the differences therebetween will be described.

The test point structure202is mounted to a circuit board210. The test point structure202generally comprises the center conductor152, an annular sleeve206having a continuous and solid wall surrounding the center conductor152, and a grounding pad208that is positioned at the base of the cylindrical interior of the sleeve206. The bottom end of the sleeve206may include an opening such that the grounding pad208can be both (i) directly connected to a conductive pad on the circuit board210, and (ii) positioned within the cylindrical interior of the sleeve206.

The center conductor152is electrically coupled to the second impedance block140of the circuit130by the line153. The grounding pad208is electrically coupled to the switch control logic160by the line209. The line209may be a ground trace. The grounding pad208may be directly mounted to a conductive pad on a surface of the circuit board210(the conductive pad being connected to the line209). Alternatively, the grounding pad208may be indirectly mounted to the conductive pad by a lead or wire, for example.

A suitable grounding pad is sold by W.L Gore and Associates, Inc. of Newark Del., and described in U.S. Pat. Nos. 6,255,581 and 7,129,421, each of which is incorporated by reference herein in its entirety.

The circuit200, or portions thereof, is bodily incorporated onto the printed circuit board210, and the circuit200is electrically coupled to both the conductor152and the grounding pad208, as is shown inFIG. 7. The center conductor152and the grounding pad208are mounted to separate traces on the board210. The center conductor152and the grounding pad208are configured to interact with a standard RF test probe180, as will be described hereinafter.

Prior to inserting the test probe180(as shown inFIG. 9), the switch control logic160(FIG. 7) senses that the grounding pad208is not coupled to ground because the test probe180has not been inserted into the test point structure202and the switch control logic160has not received a ground signal via line209. Accordingly, the switch control logic160maintains the switch138in the open position (as shown). In the open position (shown) of the switch138, the forward path signal in line108is prevented from reaching the center conductor152of the test point structure202, thereby averting a constant 1 dB loss (approximate) (as compared with the directional coupler110of the circuit100). This is the normal state of the test point structure202and the circuit200.

Upon inserting the test probe180into the sleeve206(as shown inFIG. 10), the flat distal end187of the test probe180physically contacts and compresses the grounding pad208, thereby connecting the grounding pad208to ground. Additionally, upon insertion of the test probe180, the center conductor152of the test point structure202connects to a female spring contact (not shown) embedded within the test probe180. When the switch control logic160senses that the grounding pad208is coupled to ground via line209(i.e., when logic160receives a ground signal via line209), the switch control logic160closes the switch138(which is shown open inFIG. 7). In the closed position of the switch138, the forward path signal in line108is directed through the closed switch138to the center conductor152of the test point structure202via line153. The test probe180then receives the forward path signal in line108via the connection between the male center conductor152and the female spring contact in the test probe180. The test probe180is connected to equipment (not shown) for monitoring the forward path signal in line108.

The grounding pad208and the spring156may be considered, in a general sense, as a means for detecting the presence of the test probe mated to a test point structure. The grounding pad208and the spring156are only two examples of the means for detecting the presence of the test probe mated to a test point structure. Those skilled in the art will recognize that other examples exist, such as, for example, a mechanical sensor, an optical detector (photocell, laser, passive, charged coupled device, infrared), a magnetic detector, a fiber optic sensor, a proximity sensor, a capacitive sensor, an inductive sensor, a Hall effect sensor, and so forth.

FIG. 11depicts a block diagram showing, at its most basic level, a method of monitoring an RF signal carried through a main RF signal path108using a test point144or202that is connected to the main RF signal path108. The method comprises the first step301of detecting the presence of a test probe180mated to the test point structure144or202; and the second step302of changing the state of a switch138in a test point circuit line130, which electrically connects the main RF signal path108to a center conductor152of the test point structure144or202, from an open state to a closed state, thereby directing the RF signal from the main RF signal path108through the test point circuit130and to the center conductor152. The method may also include the step of returning the switch138back to the open state when step301has ended (i.e., when the presence of the test probe180mated to the test point structure144or202is no longer detected). The detecting step302may comprise detecting when a spring156mounted to the test point structure144is contacted by a surface of the grounding body of test probe180. Alternatively, the detecting step302may comprise detecting when a grounding pad208mounted to the test point structure202is contacted by a surface of the grounding body of the test probe180.

It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions.

The terms “comprises,” “comprising,” “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “a” or “an” does not, without further constraints, preclude the existence of additional identical or similar elements in the process, method, article, or apparatus that comprises the element.

The term “coupled” as used herein refers to any logical, physical or electrical connection, link or the like by which signals produced by one system element are imparted to another “coupled” element. Unless described otherwise, coupled elements or devices are not necessarily directly connected to one another and may be separated by intermediate components, elements or communication media that may modify, manipulate or carry the signals. Each of the various couplings may be considered a separate communications channel.