Radio site monitoring device

Abstract

A radio frequency (RF) monitoring apparatus (102), comprising: an RF forward input port (116) and corresponding reverse input port (118); a tunable filter (218); an RF detector (220); an electronic processor (202) comprising a tuning signal output (208), wherein the processor (202) is configured to selectively generate a tuning signal at the tuning signal output corresponding with one or more specified frequency sub-bands, to record RF power signals generated by the RF detector (220) corresponding with RF signals received at the forward and reverse input ports (116, 118) within the specified frequency sub-bands, and to provide monitoring signals determined from the recorded RF power signals.

Description

[0001] Radio Site Monitoring Device

[0002] Related Application

[0003] This application claims the benefit of the priority of Australian Provisional Patent Application No. 2024903312. The content of Australian Provisional Patent Application No. 2024903312 is incorporated by reference in its entirety.

[0004] Field of the invention

[0005] The present invention relates to apparatus for monitoring the performance and operation of radio frequency (RF) transmission systems, and in particular wireless transmission systems.

[0006] Background

[0007] Radio frequency (RF) transmission is used in a wide range of communications applications. Without limitation, these applications include terrestrial trunked radio (TETRA), Personal Communications System (PCS), 3G, AMPS, broadcast, CDMA, DCS, government, GPRS, GSM, industrial, microwave, military, paging, public safety, rail, UHF, utilities, VHF and W-CDMA.

[0008] Many of these systems involve the use of fixed transmitters and / or receivers, which may serve large numbers of users and operate at relatively high power levels. In some applications, eg public safety, high availability of the transmission system is essential.

[0009] Accordingly, for commercial, technical and safety reasons it is desirable to incorporate appropriate monitoring devices within these systems, to enable changes in performance and / or failures of equipment to be identified and rectified quickly and safely.

[0010] While most modern high-power transmitters include internal voltage standing wave ratio (VSWR) monitoring and protection, these facilities are not generally suitable for ongoing monitoring of the health of the transmission system which might enable changes in performance to be detected early when they can be prevented from developing into more serious faults. It is therefore generally desirable to incorporate external monitoring devices, such as VSWR meters, at appropriate points within an RF transmission system ( / e along cables and at antennas).

[0011] Preferably, such monitoring devices should be capable of measuring forward and reflected power, as well as VSWR and return loss. They should be capable of monitoring transmitter output power, and of generating alarms in response to low or high power levels. They should also be capable of generating alarms if an excessive VSWR is detected, which may indicate a cable or antenna failure. It is also desirable that they should be able to be operated remotely, for example via a data network or other communications link, and that current status information, including alarms and measured properties of the transmission system, should be available at a remote terminal.

[0012] Prior art monitoring devices such as, for example, the ACM series of antenna and cable monitors from Bird Technologies Group (www.bird-technologies.com) provide many of these features. However, such prior art devices monitor the transmitted RF signal in its entirety, and are not capable of monitoring individual frequency channels within the signal. Accordingly, they are unable to detect changes in the performance of individual channels within the transmitted RF spectrum. Furthermore, a separate monitoring apparatus is required for each individual cable or antenna at a transmitter site, even where these cover different frequency bands. This results in a relatively high expense of installing a complete monitoring solution at a particular transmitter site.

[0013] Additionally, it may be desirable to provide additional onsite system and receiver performance measurement, for example by monitoring the received signal power at receiving antennas located within the same site. Presently, this requires the installation of additional equipment, at an added cost.

[0014] Accordingly, it would be desirable to provide an improved monitoring solution that is able to monitor the performance of individual frequency channels, and to facilitate additional end-to-end and receiver performance monitoring.

[0015] Summary of the Invention

[0016] The present invention provides a radio frequency (RF) monitoring apparatus, comprising: an RF forward input port and corresponding reverse input port receiving, in use, forward-propagating and reflected fields respectively, of a transmitter, within a predetermined bandwidth; at least one tunable filter having at least one tuning signal input and being configured to provide at an RF filter output a selected frequency sub-band from within the predetermined bandwidth provided at an RF filter input which is coupled to at least one of the forward and reverse input ports; an RF detector having an RF input port coupled to the RF filter output and configured to generate at a detector output an electronic signal corresponding with RF power received at the RF input port; and an electronic processor comprising at least a tuning signal output coupled to the tuning signal input of the tunable filter, and a power signal input coupled to the detector output, wherein the processor is configured to selectively generate a tuning signal at the tuning signal output corresponding with one or more specified frequency sub-bands, to record RF power signals generated by the RF detector corresponding with RF signals received at the forward and reverse input ports within said specified frequency sub-bands, and to provide monitoring signals determined from said recorded RF power signals.

[0017] Accordingly, embodiments of the invention are able to provide monitoring of individual frequency channels in an RF signal band, by configuration of the electronic processor to operate the tunable filter to select desired channel sub-bands, whereby measurement of forward and / or reverse-propagating fields within the selected sub-bands may be performed and corresponding power levels recorded. These may be used to provide monitoring signals, such as measures of forward and reflected power, as well as VSWR, return loss, and / or indications or alarms if any of these quantities, associated with any one or more channels, falls outside a predetermined acceptable operating range.

[0018] The tunable filter has at least a tunable centre frequency, and may additionally have a tunable bandwidth.

[0019] In a particularly advantageous arrangement, the apparatus comprises only a single tunable filter and a first RF switch having a switching input coupled to a first switch control output port of the processor, and configured to selectively couple the RF filter input of the tunable filter to the forward input port or the reverse input port, responsive to a first switch control signal generated by the processor.

[0020] Advantageously, the ability of the processor to switch the filtered and measured signal between the forward and reverse input ports enables the power of RF fields propagating in both directions, and in individual channels, to be measured using a single filter and RF detector. In particular, the processor may first operate the RF switch to couple the forward-propagating field to the tunable filter and RF detector, perform a first power measurement, and then operate the first RF switch to couple the reverse-propagating field to the filter and detector, before taking a second power measurement. The forward and reverse power measurements may be output, and / or may be utilised in order to calculate further performance measures, such as VSWR or return loss. It is further preferred that the apparatus comprise a plurality of forward input ports and corresponding reverse input ports, and first and second RF couplers configured to combine fields received at the forward input ports and reverse input ports respectively. For example, a preferred embodiment of the invention described herein includes four forward input ports and four reverse input ports, each pair of which may be coupled to a separate transmission cable or antenna. At a typical transmission site, a number of antennas may be provided, each of which covers a differentfrequency band. By combining monitoringsignals from each antenna in such an arrangement within the monitoring apparatus, and prior to coupling of the combined signals into the tunable filter, a single monitoring apparatus may be shared amongst, for example, four antennas. Advantageously, this reduces the cost of installing appropriate monitoring within the transmitter site.

[0021] In a further advantageous implementation, the apparatus further comprises a receiver input port receiving in use, an RF field received by a receiving antenna, and a second RF switch having a switching input coupled to a second switch control output port of the processor, and configured to selectively couple the RF filter of the tunable filter to the receiver input port or to at least one of the forward and reverse input ports, responsive to a second switch control signal generated by the processor.

[0022] In this embodiment, the same single filter and RF detector may be selectively employed to monitor a received power signal, which may be either an active channel or a pilot tone intentionally injected into a corresponding transmitted signal for this purpose. This enables the overall system transmission performance and / orthe receiver performance to be monitored.

[0023] The apparatus may further comprise an RF synthesiser having an RF output providing a continuous-wave RF field at a frequency determined by a signal applied to a frequency control input, wherein the RF output is coupled to the RF reverse input port, and the frequency control input is coupled to a frequency control output of the processor. This arrangement enables the same single monitoring device to inject an RF pilot tone at a selected frequency, determined by the frequency control output generated by the processor, into the transmitted signal. This may be used, for example, in combination with the receiver input port described above, in order to perform end-to-end monitoring of the transmission system.

[0024] Generally speaking, the monitoring signals provided by the processor may include one or more alarm signals and / or channel status information signals. Channel status information signals may include one or more of transmitted forward channel power level, reflected channel power level, and channel VSWR. Alarm signals may include one or more of low channel-power alarms, high channel-power alarms, and excessive channel-VSWR alarms.

[0025] When the receiver input port is employed, the monitoring signals may further include one or more of a low received power alarms and received power level status information signals.

[0026] In an embodiment as described herein, the processor comprises: a microprocessor including, or operatively coupled to, at least one memory device; at least one input / output interface operatively coupled to the microprocessor; a tuning signal output operatively coupled to the microprocessor and the tuning signal input of the tunable filter; and an RF power input operatively coupled to the microprocessor and to the RF detector output, wherein the memory device comprises instructions executable by the microprocessor to cause the electronic processor to execute the steps of: generating a tuning signal output corresponding with a selected frequency sub-band; receiving an RF power input signal corresponding with RF power of at least one selected RF input signal within the selected frequency sub-band; computing at least one monitoring signal value based upon said RF power input signal; and generating at least one monitoring signal value output via the input / output interface.

[0027] In exemplary embodiments, the at least one input / output interface may include one or more of: indicator lamps or LEDs; a visual display panel; a network interface; a serial port interface; and an alarm signal interface.

[0028] Further preferred features and advantages of the invention will be apparent to those skilled in the art from the following description of a preferred embodiment of the invention, which should not be considered to be limiting of the scope of the invention as defined in any of the preceding statements, or in the claims appended hereto.

[0029] Brief Description of the Drawings

[0030] Embodiments of the invention are now described with reference to the accompanying drawings, in which like reference numerals indicate like features, and wherein:

[0031] Figure 1 illustrates a portion of a wireless RF transmission system embodying the present invention;

[0032] Figure 2 is a block diagram of an RF monitoring apparatus according to an embodiment of the invention;

[0033] Figure 3 is a flowchart illustrating a method of continuous monitoring according to a preferred embodiment of the invention;

[0034] Figure 4 is a high-level block diagram illustrating a portion of the architecture of the alternative monitoring apparatus.

[0035] Figure 5 is a block diagram of a plurality of RF transmitter input ports and a plurality of RF receiver input ports of an RF monitoring apparatus according to an alternative embodiment of the invention;

[0036] Figure 6 is a block diagram of a plurality of receivers of the RF monitoring apparatus of Figures 4 and 5;

[0037] Figure 7 is a block diagram of a system on module (SOM) of the RF monitoring apparatus of Figures 4 to 6;

[0038] Figure 8 comprises a block diagram of a transmitter / signal generator and a block diagram of a clock network of the RF monitoring apparatus of Figures 4 to 7;

[0039] Figure 9 is a block diagram of a power supply unit (PSU) and power supply regulators of the RF monitoring apparatus of Figures 4 to 8;

[0040] Figure 10 is a block diagram of a test port of the RF monitoring apparatus of Figures 4 to 9;

[0041] Figure 11 is an illustration of software stackof the RF monitoringapparatus of Figures 4 to 10;

[0042] Figure 12 is an illustration of the RF monitoring apparatus of Figures 4 to 11 ;

[0043] Figure 13 is an illustration of the RF monitoring apparatus of Figures 4 to 12 as implemented with an antenna line coupler and other components of a RF wireless system; and Figure 14 is a table setting out the technical specification of the RF monitoring apparatus of Figures 4 to 13.

[0044] Detailed Description of Embodiments

[0045] Figure 1 is a block diagram illustrating a portion of an RF wireless transmission system 100 incorporating a monitoring apparatus 102 embodyingthe present invention.

[0046] The system 100 includes one or more transmitting antenna units, eg 104, 106. The exemplary system 100 also includes a receiving antenna unit 108. Each transmitting antenna unit 104 typically includes a transmitter combiner 110 which combines a plurality of transmitted channels having different carrier frequencies for transmission via a single antenna 112. To facilitate monitoring of the transmitted signal by the apparatus 102, a directional coupler 114 is installed at the antenna 112 for monitoring both forwardpropagating and reflected RF fields. Each forward-propagating coupler output is connected to a corresponding forward input port 116 of the monitoring apparatus 102, while each reflected field monitoring port is connected to a corresponding reverse input port 118. That is, the directional couplers of each transmitting antenna unit 104, 106 are connected to a corresponding pair of forward and reverse input ports of the monitoring apparatus 102.

[0047] The receiving antenna unit 108 includes a receiving antenna 120 and a receiver multicoupler 122. A plurality of outputs 123 of the multi-coupler 122 are connected to corresponding receivers (not shown) for detecting and demodulating separate received RF channels. A further output port 124 of the multi-coupler 122 is connected to a corresponding receiver input port 126 of the monitoring apparatus 102.

[0048] Further features of the exemplary apparatus 102, which may or may not be present in particular embodiments, include a set of indicator lamps or LEDs 128, a display panel 130, an alarm output port 132, a computer peripheral interface port 134 (such as a USB port), and a network interface port 136 (such as an Ethernet or other LAN port, eg an RJ45 connector). A variety of alternative input / output or data communications ports, such as would be well-known to persons skilled in the art, may also be provided.

[0049] A block diagram illustrating the internal circuitry of an exemplary monitoring apparatus 102 is shown in Figure 2.

[0050] In particular, the monitor 102 includes an electronic processor202, which comprises a central processing unit (CPU) 204 and an associated memory device 206. The CPU 204 and memory 206 may be integrated into a single microcontroller device, or may be separate components operatively coupled together in a conventional manner. The memory 206 may comprise volatile memory locations, non-volatile memory locations, or more generally a combination of both, for storing both static and transient data and program instructions associated with the operation of the processor 202. In particular, the memory 206 at least includes program instructions executable by the CPU 204 in order to implement relevant features of the monitoring apparatus 102 via programmatic means, as described in greater detail herein.

[0051] The processor 202 further comprises a number of electronic control and data lines, comprising a bus 208 connected to various other components of the monitoring apparatus 102, as shown in Figure 2 and further described below. A plurality of further digital output signals 210 are connected to corresponding front panel indicator LEDs 128. A set of alarm signals 212 is also provided from the processor 202 to a back panel alarm signal port 132, which may include a standard connector, such as a D15 connector. A network interface connection 216 is also provided between the processor 202 and a corresponding network port 136, which may comprise, for example, an RJ45 connector. A further local communications signal line 214, which may comprise, for example, a USB peripheral interface, is also provided between the processor 202 and a corresponding back panel connector 134.

[0052] The monitoring apparatus 102 incorporates a tunable filter 218. As described in greater detail below, the function of the tunable filter 218 is to receive selected signals from the input ports 116, 118, 126, and to select specified frequency sub-bands which are output to RF detector 220. The detector 220 measures the power in the signal provided from the tunable filter 218 at its RF input port, and generates a corresponding output signal corresponding with the detected power that is received by the processor 102 via the signal bus 208.

[0053] Advantageously, the monitoring apparatus 102 is configured such that a single tunable filter 218 may be shared between multiple input ports. In particular, a first RF switch 222 is provided which has a switching input controllable via the signal bus 208 of the processor 202. The switch 222 selects between forward input ports 116 and reverse input ports 118. Accordingly, the output of RF switch 222 is a signal, or combination of signals, comprising samples of either forward-propagating fields of the antennas 112 or reverse-propagating ( / e reflected) fields. Accordingly, the processor 202 is able to switch between measurements of forward and reflected fields. A second RF switch 224 is provided which is configured to switch between the transmitted field ports 116, 118 and the receiver monitoring port 126. The second switch 224 is also controllable by the processor 202 via the signal bus 208. Accordingly, by appropriate operation of the first and second switches 222, 224, the processor 202 is able to select any one of the forward transmitted field 116, reflected transmitted field 118, and received signal 126 input ports, signals from which are applied to the input of the tunable filter 218.

[0054] Tuning of the tunable filter 218 is performed under control of the processor 202 via the signal bus 208, based upon a reference oscillator 225 and two computer-controlled RF synthesisers 228, 236 that are referenced to the oscillator 225.

[0055] More particularly, the tunable filter 218 includes a first fixed RF filter 226 having a predetermined centre frequency and bandwidth corresponding with the frequency band within which the RF transmission system 100 operates. Thus the first RF filter 226, which may be, for example, a helical bandpass filter, rejects any signals outside this predetermined operating bandwidth.

[0056] An RF synthesiser 228 generates a continuous-wave (CW) RF signal having a frequency determined under control of the processor 202. This CW signal is mixed with the output of the first filter 226 in RF mixer 230, resulting in down conversion of the filter input signal to an intermediate frequency (IF) band. A narrower bandpass filter 232 corresponding with a frequency sub-band (eg a single-channel bandwidth, or a plurality of channel bandwidths) within the IF band selects a corresponding sub-band from the IF signal. Accordingly, by appropriate selection of the output signal from the RF synthesiser 228, a sub-band at any desired frequency within the filter input can de selected. A second RF mixer 234 mixes the selected sub-band signal with the CW output of the synthesiser 228, resulting in an RF signal that now includes only the selected sub-band.

[0057] As will be appreciated, therefore, the synthesiser 228, mixers 230, 234 and the bandpass filter 232 (which may be, for example, a crystal filter) enable the selection of any sub-band, such as an individual frequency channel, from the complete received signal band. While this signal could be input directly to an RF detector, in order to measure its corresponding power, it is generally desirable to provide additional amplification and / or other signal conditioning in order to ensure that the input to the RF detector 220 lies within an optimum operating range. In the exemplary embodiment 102, amplifiers 237, 239 are provided for this purpose, and a further narrowband filter 240, such as another crystal bandpass filter, is provided in order to reject unwanted noise introduced by the amplifiers. The filter 240 has a fixed centre frequency, while the output from the mixer 234 has a variable centre frequency, depending upon the selected sub-band, and a second RF synthesiser 236 and corresponding mixer 238 are provided in order to down-convert the selected RF signal to a fixed IF signal frequency corresponding with the bandpass filter 240. In order to achieve this, the output frequency of the RF synthesiser 236 is referenced to the same oscillator 225 as the first synthesiser 228, and is also operated under control of the processor 202 via the signal bus 208.

[0058] The second IF bandpass filter 240 may have the same, or different, bandwidth and centre frequency to those of the first IF filter 232. In an advantageous arrangement, the bandwidth of both IF filters 232, 240 is greater than the narrowest channel bandwidth of interest. By selecting different frequencies for the RF synthesisers 228, 236, each of the IF filters will effective cover a different sub-band of the overall RF spectrum. Selectively overlapping these sub-bands enables the two IF filters 232, 240 to provide a variable-width “sliding window” within the frequency domain. In this way, the tunable filter 218 is tunable in both centre frequency and bandwidth.

[0059] To recap, the processor 202 is able to control which of the input signals ( / e transmitted forward or reverse fields 116, 118 or received signal 126) are input to the tunable filter 218, and which sub-band, or individual frequency channel is output from the filter 218 to the RF detector 220. In other words, the processor 202 has full control over the measurement of power in any individual frequency channel, or other sub-band, monitored at any of the transmitter units 104, 106 or at the receiver unit 108.

[0060] In one exemplary embodiment for use in the 746-870 MHz band, the helical filters 226, 246 have a centre frequency of 808 Mhz, and a bandwidth of 124 MHz, while the crystal filters 232, 240 have a centre frequency of 90 MHz and a bandwidth of 20 kHz. It will be understood, however, that these component values may be changed in order to suit other applications.

[0061] Additional components which facilitate this operation include the couplers 242, 244, and the bandpass filter 246. In particular, the two couplers 242, 244 combine the forward and reverse fields, respectively, sampled at each transmit antenna unit, eg 104, 106. Assuming that each transmitter operates within a different frequency range within the overall system bandwidth, no additional filtering is required. On the receiving side, however, a filter 246, which may be a further helical bandpass filter, is used to reject frequencies outside the operating system bandwidth, such as noise and unwanted signals that may be picked up by the receive antenna 120.

[0062] The final substantive functional component of the apparatus 102 is a further RF synthesiser 248, also operable by the processor 202 via the signal bus 208. This RF synthesiser generates a CW signal referenced to the oscillator 225 that is injected via the coupler 244 (operating in reverse as a splitter) to the transmit antennas, eg 112. This CW signal is therefore transmitted, and may be received at a remote site, via a corresponding receiving antenna unit 108. Accordingly, the processor 202 is able to select a pilot tone frequency, which may be any unused frequency within the system bandwidth, which is then transmitted and can be used at a similar monitoring apparatus 102 at the receiving end in order to monitor the end-to-end performance of the transmission system at the pilot tone frequency.

[0063] It will therefore be understood that the apparatus 102 provides a number of significant advantages over prior art monitoring devices. Firstly, it is highly flexible and can be used to monitor individual frequency channels, without requiring the installation of multiple monitoring devices. Furthermore, it is able to provide such monitoringfor multiple transmit antennas simultaneously. It is also able to monitor received signal power, in one or more active channels, and / or end-to-end transmission performance via a CW tone that may be injected at any desired frequency within the operating bandwidth of the system 100. The apparatus shares a single tunable filter 218 and RF detector 220 within a single unit between multiple transmit antenna units and a receive antenna unit at each site. All of this is able to be achieved under software control via a programmable processor 202, which also provides a variety of convenient interfaces for accessing monitoring signals, including alarm signals and / or channel status information signals. For example, channel status information signals may include transmitted forward channel power levels, reflected channel power levels, and channel VSWR. These may be monitored over time, in order to detect changes or degradation in channel performance. Alarm signals may include signals such as low channel-power alarms, high channel-power alarms, and excessive channel-VSWR alarms.

[0064] One exemplary continuous monitoring operation that the processor 202 may be configured to perform will now be described with reference to the flowchart 300 shown in Figure 3.

[0065] The purpose of the exemplary process 300 is to perform continuous monitoring of a number of transmitted frequency channels, and one received frequency channel. The exemplary nature of this process 300 must be emphasised, however, since the processor 202 may be programmed to perform any desired sequence measurements. Thus it should be appreciated, for example, that any number of received signal channels may be monitored, or that selected subsets of transmitted channels may be monitored, or that any of the monitoring functions described in the process 300 may optionally be included or omitted. Additionally, the order in which various operations are performed within the exemplary process 300 may be changed, and the particular sequence of steps described herein should not be taken as limiting.

[0066] At step 302, the processor operates the second switch 224 in order to select the forward or reverse port signals output from the first switch 222. That is, the processor 202 selects measurement of transmitted signals. Subsequent steps 304 to 320 thus represent the measurement of signals present at the transmit antenna units, eg 104, 106.

[0067] At step 304, the processor 202 selects the forward input ports output from coupler 242 via the first RF switch 222. The processor 202 then selects a desired frequency subband or channel via the tunable filter 218, at step 306. At step 308 the processor 202 samples the power output signal from the RF detector 220, thereby measuring the corresponding channel forward power at the transmit antenna. Typically, this power measurement will then be stored in memory 206.

[0068] At step 310, the processor 202 operates the first switch 222 to select the reflected fields output from the coupler 244. The processor 202 then again samples the output of the RF detector 220, thereby obtaining a measurement of the reflected power in the selected channel at the transmit antenna. Again, this measured power value may be stored in memory 206.

[0069] At step 314, appropriate monitoring signal values, such as forward power, reverse power, VSWR, and so forth, are computed. These may be stored in memory 206, which preferably has sufficient capacity to retain a number of historical values for ongoing performance monitoring purposes.

[0070] At decision step 316 the computed monitoring signal values are compared with relevant alarm limits. For example, the forward power may be compared with a minimum acceptable transmitted power level, while the reverse power may be compared with a maximum acceptable reflected power value. Alternatively or additionally the VSWR may be compared with a maximum acceptable value. If any relevant alarm levels that may be set have been exceeded, control passes to step 318, at which the processor 202 activates the relevant alarm signals. This may include lighting one or more of the LEDs 128, as well as activating corresponding alarm lines at the alarm interface 132. Additionally, the existence of the alarm conditions may be recorded within the memory 206, along with the computed monitoring signal values.

[0071] At step 320 the processor 202 determines whether there are additional transmitted channel frequencies to be monitored. If so, then a new frequency is selected, and control returns to step 304, at which the transmitter monitoring process recommences, this time selecting the new frequency channel at step 306. Once all channels have been monitored on the transmit side, control passes to step 322.

[0072] At this step, the processor 222 operates the second RF switch 224 in order to select the receiving input port signal output from the bandpass filter 246. At step 324, the processor 202 operates the tunable filter 218 in order to select a desired frequency subband or channel atthe receiver. The corresponding received signal power is detected bythe RF detector 220, the output of which is sampled by the processor 202 thereby measuring the received channel power.

[0073] At step 328, relevant receiver monitoring signal values are computed. In one exemplary application, the processor 202 at a remote transmitting station operates the RF synthesiser 248 in order to select an output CW signal tone to be used for end-to-end performance monitoring. It is then possible at the receiving end to compute a receiver monitoring signal value comprising a total system transmission loss at this monitoring frequency. Alternatively, or additionally, the power in one or more active received channels may be monitored.

[0074] In addition to the monitoring functions exemplified by the foregoing description, the monitoring apparatus 102 may provide a number of additional features via the interface ports 132, 134, 136.

[0075] Forexample, a conventional personal computer(PC), or a portable computingdevice (such as a notebook or tablet PC) may be connected to the apparatus 102 via the USB port 134. The connected PC may thereby communicate with the processor 202, and in particular may request current and / or historical monitoring data that has been stored in the processor memory 206. Once uploaded to the PC, this data may be presented to a user, for example via a “dashboard” display which may show current monitored power levels, VSWR values, alarm indications, and / or other information. Historical values may be shown, for example in the form of graphs over time. Alternatively or additionally, uploaded data may be stored to a file on the PC, for subsequent review and processing, such as by a spreadsheet application or similar program.

[0076] Additionally, the USB interface 134 may be used to provide software updates to the processor 202. Accordingly, new functionality may be implemented within the monitoring apparatus 102, and / or any bugs fixed, via software upgrades.

[0077] The network interface 136 may be used to provide remote access, for example via the Internet, to the monitoring apparatus 102. Features provided via remote access may include one or more of the local features available via the USB port. Additionally or alternatively, the processor 202 may be programmed to implement a web server application enabling access to the apparatus 102 via a conventional web browser, such as Internet Explorer, Firefox, Safari, or Google Chrome. The processor202 may therefore be configured to provide current and / or historical information by serving corresponding web pages to the remote browser application. Such a web interface may also allow download of data via a browser interface, and / or the installation of software upgrades within the processor 202.

[0078] The alarm interface 132 provides simple and direct access to a number of alarm signals. As shown in Figure 2, these include a summary fault alarm, a receiver RF level alarm, a forward RF level alarm, and a VSWR summary alarm. Activation of any of these alarms may indicate a potential safety issue, or the possibility of damage to equipment at the transmitter site. Certainly, activation of an alarm may require prompt operator intervention.

[0079] Accordingly, the alarm signals available at the alarm port 132 may be used to activate external alarm or warning indicators, including visual indicators (such as lamps), or audible indicators such as buzzers or sirens.

[0080] Additionally, or alternatively, alarm signals available from the alarm interface port 132 may be used to activate appropriate safety interlock systems, for example disabling transmitters in the event that the VSWR summary alarm is activated, which may indicate a potentially hazardous or damaging fault.

[0081] According to a further variation of the monitoring apparatus 102, actual receiver sensitivity measurements may be made at a site, which could be used to show up any degradation in ongoing site performance due to the presence of noise or interference. Instead of injecting a constant, fixed level CW signal into the transmit antenna, a modulated signal with variable output power is injected instead, and picked up via the receiver port 126. A receiver built into the apparatus 102 demodulates the signal, and can be used to measure the 12 dB SINAD (analogue) or 5% BER (digital) signal level thresholds. Any degradation over time would indicate the presence of noise or interference.

[0082] An alternative exemplary monitoring apparatus 802 is shown in Figures 4 to 14. As will be explained in more detail below, this alternative monitoring apparatus 802 shares many of the same elements that are used by the monitoring apparatus 102 of Figure 2. For example, like with the monitoring apparatus 102 of Figure 2, the RF monitoring apparatus 802 has external inputs and relay outputs. More specifically, the RF monitoring apparatus 802 has an external I / O controller 506 with four external inputs and four relay outputs, where the first input is a dedicated 0-5 V DC analogue input particularly suited to temperature sensors (which may be inside a site hut or equipment racks) and the three remaining analogue inputs have a range of + / - 60 V DC, and the four relay outputs are used as alarm units. As will be explained in more detail below, additional dedicated I / O modules can be connected to the I / O controller 506 to expand the number of inputs and outputs.

[0083] As will be explained in relation to Figures 4 to 14, there are some significant differences between the RF monitoring apparatus 802 and the monitoring apparatus 102 of Figure 2. Instead of using a pair of analogue filters connected in series to create a sliding filter window for channelizing an incoming spectrum to make channel-specific signal level measurements, this alternative monitoring apparatus 802 converts the incoming spectrum to the digital domain, after the digital spectrum is channelized using one or more digital filters 5020, 5022 that is implemented using an FPGA.

[0084] Figure 4 is a high-level block diagram illustrating a portion of the architecture of the RF monitoring apparatus 802. As illustrated in Figure 4, the FPGA is located on a system on module (SOM) 502 within which the digital channelizing filters 5020, 5022 are implemented. The alternative monitoring apparatus 802 also comprises two receivers 300, 400 each from which I & Q outputs of dual ADCs 310, 410 are each decimated to a 20 MHz band of spectrum from which the channelising digital filters 5020, 5022 extract up to 15 channels of data which is saved to memory via direct memory access. The data is then used to measure individual channel signal levels in the digital domain. In this embodiment, ADC samples are also saved to memory for enabling further analysis. This analysis includes but is not limited to detection of timeslot information in TDMA modulation schemes, data enabling spectrum analysis studies, and detection of specific symbols which may be used for (but not limited to): increased accuracy in received signal strength measurements; • error vector magnitude (EVM) and modulation fidelity measurements of radios or base stations; and

[0085] • decoding of data to identify timeslot IDs, calculate bit error rate (BER) to perform sensitivity measurements, identify different types of data packets or timeslots, and identify particular radio IDs.

[0086] Thus, the RF monitoring apparatus 802, as illustrated in Figures 4 to 14, has a different architecture to that of the monitoring apparatus 102 of Figure 2. For example, the alternative RF monitoring apparatus 802 also includes an in-built database to log and store measurements, alarms, etc. such that the amount of data that can be processed by the alternative RF monitoring apparatus 802 can be greater compared to what can be achieved with the monitoring apparatus 102 of Figure 2. A person skilled in the art would also appreciate that the alternative monitoring apparatus 802 of Figures 4 to 12 can also be advantageous when compared to the monitoring apparatus 102 of Figure 2 in that:

[0087] • more data can be processed and stored due to the inbuilt database, as indicated above;

[0088] • processing speed (potentially 28 times faster) can be higher;

[0089] • processing can be asynchronous;

[0090] • for TDMA networks (DMR, TETRA, APCO 25 Phase 2 etc.), timeslots can be detected allowing discrete calculations for each time slot;

[0091] • broadband operation supporting 132 - 960 MHz, as opposed to requiring four different models to cover this band;

[0092] • advanced cyber security features can be implemented;

[0093] • connectivity with external network operations centre monitoring software (such as software used by public safety network operations centres) can be improved;

[0094] • aggregation of time series measurement data can be supported at a server level;

[0095] • a modern graphic user interface allowing for a much-improved user experience can be provided; and

[0096] • Third parties can access the database to craft their own dashboards and customize their own reports.

[0097] As will be described in further details in Figures 4 to 14, the RF monitoring apparatus

[0098] 802 is configured to monitor parameters of and / or derived from signals on a plurality of RF channels of a radio network protocol, comprising a main printed circuit (PC) board which in turn comprises: an RF forward input port 116 and corresponding reverse input port 118 receiving, in use, forward-propagating and reverse-propagating (or reflected) fields respectively, of a transmitter 104, within the operational bandwidth of the apparatus 802; and a first high performance low-noise receiver 300 and a second high performance low- noise receiver 400, wherein signals corresponding to the forward-propagating and the reflected fields output from the RF forward input port 116 and the reverse input port 118 are selectively switched by a first switch 312 and a second switch 412 such that a RF forward signal received at the transmitter 104 is switched to one of the first receiver 300 and the second receiver 400 and a corresponding reverse signal received at the transmitter 104 is switched to the other one of the first receiver 300 and the second receiver 400, in order to allow simultaneous measurements (such as power levels, and signal strength) of the RF forward signal and the corresponding reverse signal.

[0099] A person skilled in the art would appreciate that the simultaneous measurements of the RF forward signal and the corresponding reverse signal is advantageous in that the measurements can be made significantly faster when compared to first measuring one of the RF forward signal and the corresponding reverse signal and then subsequently measuring the other one of the RF forward signal and the corresponding reverse signal. Because the forward and reverse signals are correlated, the accuracy of any VSWR and / or return loss measurements may be optimised.

[0100] As illustrated in Figure 6, the RF forward and corresponding reverse signals are each demodulated in the first and second receivers 300,400 respectively to an (IF) in-phase (I) signal and an IF quadrature (Q) signals 11, 1 Q, 2I, 2Q using a quadrature demodulator 302, 402. In this implementation, 65MHz is the filter cut-off frequency, and the IF is typically 30 MHz but may vary depending on RF channel frequency bands of interest. In each of the first and second receivers 300,400, the I & Q signals 11, 1 Q, 2I, 2Q are then low-pass filtered 304, 404 to remove upper image frequencies, and the low-pass filtered signals 11F A, 11F B, 2IF A, 2IF B are then amplified using dual, digitally variable gain, amplifiers (DVGA) 306, 406. The outputs OUT A, OUT B of the amplifiers 306, 406 are again low-pass filtered 308, 408, and the again low-pass filtered signals INA, INB are then converted to digital signals using dual analogue to digital converters (ADCs) 310, 410 operating with a sampling rate of 125 MBPS (Megabit / second). As illustrated in Figure 6, the RF monitoring apparatus 802 also comprises the SOM 502 that interfaces with the main PC board. The digital I & Q output streams are fed to the FPGA located on the SOM 502. The FPGA is controlled by a microprocessorto decimate the output streams down to a 20 MHz band of spectrum. Up to 15 separate channels within this 20 MHz band of spectrum can then be digitally filtered out simultaneously using the FPGA, with the individual digital filter passband profiles being able to be set according to the radio network protocol of the channels being monitored. The individual signal strength of each of the 15 channels can then be measured in the digital domain.

[0101] Accordingly, embodiments of the invention are able to provide monitoring of individual frequency channels in the operational bandwidth of the apparatus 802, by configuration of the FPGA by the microprocessor to operate the digital filters 5020, 5022 to select desired channels, whereby measurement of forward and / or reverse-propagating signals for each channel may be performed and corresponding power levels recorded. These may be used to provide monitoring signals, such as measures of forward and reflected power, as well as VSWR, return loss, and / or indications or alarms if any of these quantities, associated with any one or more channels, falls outside a predetermined acceptable operating range.

[0102] As indicated above, in a particularly advantageous arrangement, the apparatus 802 may comprise a first and second high-performance, low-noise receiver 300, 400 and a first and second RF switch 312, 412 having switching inputs coupled to a first and second set of switch control output ports of the microprocessor, and configured to selectively couple the RF inputs of the first and second low-noise receivers 300, 400 to a forward input port 116 or a reverse input port 118, responsive to a first and second set of switch control signals generated by the microprocessor.

[0103] Advantageously, the ability of the apparatus to simultaneously measure the digital- filtered signal from both the forward and reverse input ports 116, 118 enables the power of RF fields propagating in both directions, and in individual channels, to be calculated. The forward and reverse power measurements may be output, and / or may be utilised in order to calculate further performance measures, such as VSWR or return loss.

[0104] It is further preferred that the apparatus comprise a plurality of forward input ports 116 and corresponding reverse input ports 118, with the first and second RF switches 312, 412 configured to couple the RF inputs of the first and second low-noise receivers 300, 400 to any of the forward input ports 116 and reverse input ports 118 respectively. For example, a preferred embodiment of the invention described herein includes three forward input ports 116 and three reverse input ports 118, each pair 116, 118 of which may be coupled to a separate transmission cable or antenna. At a typical transmission site, a number of antennas may be provided, each of which covers a different frequency band. By combining monitoring signals from each antenna in such an arrangement within the monitoring apparatus, a single monitoring apparatus may be shared amongst, for example, three antennas. Advantageously, this reduces the cost of installing appropriate monitoring within the transmitter site.

[0105] In a further advantageous implementation, the apparatus further comprises a receiver input port 126 receiving in use, an RF signal received by a receiving antenna, coupled to the first and second RF switches 312, 412 having switching inputs coupled to a first and second set of switch control signals generated by the microprocessor, and configured to selectively couple the RF input of the first or second low-noise receiver 300, 400 to a receiver input port 126, responsive to a first and second set of switch control signals generated by the microprocessor.

[0106] It is further preferred that the apparatus comprise a plurality of receiver input ports 126, with the first and second RF switches 312, 412 configured to couple the RF inputs of the first and second low-noise receivers (300, 400) to any of the receiver input ports 126 respectively. For example, a preferred embodiment of the invention described herein includes three receiver input ports 126, each of which may be coupled to a separate receiving antenna.

[0107] In this embodiment, the apparatus may be selectively employed to monitor a received power signal, which may be either an active channel or a pilot tone intentionally injected into a corresponding transmitted signal for this purpose. This enables the overall system transmission performance and / or the receiver performance to be monitored.

[0108] The apparatus may further comprise an RF synthesiser 906 having an RF output providing a continuous-wave RF signal at a frequency determined by a signal applied to a frequency control input, wherein the RF output is coupled to an RF reverse input port 118, and the frequency control input is coupled to a frequency control output of the microprocessor. This arrangement enables the same single monitoring device 802 to inject an RF pilot tone at a selected frequency, determined by the frequency control output generated by the microprocessor, into the transmitted signal. This may be used, for example, in combination with the receiver input port 126 described above, in order to perform end-to-end monitoring of the transmission system.

[0109] Generally speaking, the monitoring signals provided by the microprocessor may include one or more alarm signals and / or channel status information signals. Channel status information signals may include one or more of transmitted forward channel power level, reflected channel power level, and channel VSWR. Alarm signals may include one or more of low channel-power alarms, high channel-power alarms, and excessive channel- VSWR alarms.

[0110] When the receiver input port 126 is employed, the monitoring signals may further include one or more of a low received power alarms and received power level status information signals. In an embodimentas described herein, the microprocessor comprises: a microprocessor including, or operatively coupled to, at least one memory device; at least one input / output interface operatively coupled to the microprocessor; a low-noise receiver output operatively coupled to the microprocessor; and a digitally-filtered signal operatively coupled to the microprocessor and to the digital RF detector output.

[0111] Turning now to Figure 5, there is illustrated a block diagram of a plurality of pairs of RF transmitter input ports 116, 118 and a plurality of RF receiver input ports 126 of an RF monitoring apparatus 802 according to an alternative embodiment of the invention. Beginning first with the pairs of RF transmitter input ports 116, 118, each pair of RF transmitter input ports 116, 118 comprises a RFforward input port 116 and a corresponding RF reverse input port 118.

[0112] Each RF forward input port 116 comprises a first attenuator 1160, a first RF switch 1162, a coupler 1164, a second attenuator 1166, and a second RF switch 1168. The first attenuator 1160 is a fixed 12 dB Pi attenuator used to reduce the input signal level for the components that follow so as to be within their safe operating levels. The value of the attenuation has been based on the peak instantaneous power (PIP) level produced by a worst-case site scenario of a transmitter combiner 110’ with up to 12 x 100 W APCO 25 Phase 2 modulated transmitter carriers feeding a single transmitter antenna 104’, 106’.

[0113] The first RF switch 1162 is a high isolation, low insertion loss CMOS switch designed for RF applications and covering 10 - 3000 MHz. The switch 1162 either routes a signal at the output of the 12 dB attenuator 1160 through to the following coupler stage 1164 or isolates the signal when measurements of signals present at the forward port 116 are not being made. The latter mode provides further isolation of unwanted signals at the receivers 300, 400 when a measurement of a wanted signal is taking place.

[0114] The coupler 1164 is a wideband low insertion loss directional coupler covering 5 - 1000 MHz with 13 dB coupling and up to 18 dB directivity. This allows a sample of a signal present at the RF forward input port 116, reduced in level by a total of 25 dB (that is, 12 dB attenuator 1160 plus 13 dB coupled level), to be routed through to the test port 8000 where it can ultimately be conveniently viewed using a spectrum analyser for non-intrusive analysis when required. The second attenuator 1166 is a fixed 12 dB Pi attenuator used to further reduce the input signal level for the components that follow so as to be within their safe operating levels. The second RF switch 1168 is a high isolation, low insertion loss CMOS switch designed for RF applications and covering 10 - 3000 MHz. The switch 1168 steers a signal to be measured to either a first receiver 300 or a second receiver 400.

[0115] Like with each RF forward input port 116, each RF reverse input port 118 comprises a first attenuator 1180, a first RF switch 1182, a coupler 1184, a second attenuator 1186, and a second RF switch 1188. Like with the first attenuator 1160 of each RF forward input port 116, the first attenuator 1180 of each RF reverse input port 118 is a fixed 12 dB Pi attenuator used to reduce the input signal level for the components that follow so as to be within their safe operating levels. The value of the attenuation for each RF reverse input port 118 is identical to that in each RF forward input port 116 such that the same resistors can be used which may be advantageous from a cost and component stocking aspect.

[0116] Like with the first RF switch 1162 of each RF forward input port 116, the first RF switch 1182 of each RF reverse input port 118 is a high isolation, low insertion loss CMOS switch designed for RF applications and covering 10 - 3000 MHz. The RF reverse input port 118 is a convenient point to inject a signal into an antenna coaxial feeder cable for antenna isolation measurements, so the switch 1182 is connected such that it either routes the signal at the output of the 12 dB attenuator 1180 through to the following coupler stage 1184 or passes the signal being fed from the signal generator 600 through to the 12 dB attenuator 1180 to be fed back to the RF reverse input port 118 and on to the antenna coaxial feeder cable.

[0117] Like with the coupler 1164 of each RF forward input port 116, the coupler 1184 of each RF reverse input port 118 is a wideband low insertion loss directional coupler covering 5 - 1000 MHz with 13 dB coupling and up to 18 dB directivity, which allows a sample of a signal present at the RF reverse input port 118, reduced in level by a total of 25 dB (that is, 12 dB attenuator 1180 plus 13 dB coupled level), to be routed through to the test port 8000 where it can ultimately be conveniently viewed using a spectrum analyser for non-intrusive analysis when required.

[0118] Like with the second attenuator 1166 of each RF forward input port 116, the second attenuator 1186 of each RF reverse input port 118 is a fixed 12 dB Pi attenuator used to further reduce the input signal level for the components that follow so as to be within their safe operating levels. Like with the second RF switch 1168 of each RF forward input port 116, the second RF switch 1188 of each RF reverse input port 118 is a high isolation, low insertion loss CMOS switch designed for RF applications and covering 10 - 3000 MHz, which steers a signal to be measured to either the first receiver 300 or the second receiver 400.

[0119] Turning now to the plurality of RF receiver input ports 126, each RF receiver input port 126 comprises a first coupler 1260, a second coupler 1262, an attenuator 1264, a power detector 1266, and a RF switch 1268.

[0120] Like with the coupler 1164 of each RF forward input port 116 and coupler 1184 of each RF reverse input port 118, the first coupler 1260 of each RF receiver input port 126 is a wideband low insertion loss directional coupler covering 5 - 1000 MHz with 13 dB coupling and up to 18 dB directivity, which allows a sample of a signal present at the RF receiver input port 126, adjusted in level by an amplification stage and 13 dB of coupling loss, to be routed through to the test port 8000 where it can ultimately be conveniently viewed using a spectrum analyserfor non-intrusive analysis when required.

[0121] The second coupler 1262 is also a wideband low insertion loss directional coupler covering 5 - 1000 MHz with 13 dB coupling and up to 18 dB directivity. This second coupler 1262 allows a sample of a signal present at the RF receiver port 126, adjusted in level by three amplification stages and 13 dB of coupling loss, to be routed through to the attenuation stage 1264 which is fixed 3 dB Pi attenuator used to reduce the coupled signal level for the components that follow so as to be within their safe operating levels.

[0122] The power detector 1266 is a logarithmic RMS power detector with 45 dB dynamic range and an operational bandwidth of 50 - 8000 MHz, which provides an analogue output voltage that is linearly related to the signal level at the output of the attenuator 1264. This output voltage is thus linearly related to the composite receiver (Rx) signal level at the respective RF receiver input port 126. This is a composite power measurement to alarm and guard against receiver overload conditions arising from rogue signals that are on frequencies other than those that are monitored and measured by the first and second receivers 300 and 400. The analogue output voltage level is converted to a digital signal by ADCs in 501 within the SOM and digital control block500 for processing by the SOM 502 and reporting via a graphical user interface.

[0123] Like with first RF switch 1162 and the second RF switch 1168 of each RF forward input port 116 and first RF switch 1182 the second RF switch 1188 of each RF reverse input port 118, the RF switch 1268 of each RF receiver input port 126 is a high isolation, low insertion loss CMOS switch designed for RF applications and covering 10 - 3000 MHz. As illustrated in figure 5, there is a main line signal for each RF receiver input port 126, specifically, through the two directional couplers 1260 and 1262 where a RF receiver input signal is adjusted in level by two amplification stages. The RF switch 1268 steers the main line output signal of the second coupler 1262 to either the first receiver 300 or the second receiver 400 for measurement.

[0124] Figure 6 is a block diagram of the receivers 300, 400 of the RF monitoring apparatus 802 of Figure 5. As indicated in the figure, each of the receivers 300, 400 is a high IF receiver comprisingan attenuator 301 , 401 in connection with a demodulator 302, 402 in connection with a potentiometer 303, 403. The demodulator 302, 402is connected with three filters 304, 305, 404, 405, two 304, 404 of which are connected to an amplifier 306, 406. Each receiver 300, 400 also comprises two additional filters 308, 408 connecting the amplifier 306, 406 to a dual analogue to digital converter (ADC) 310, 410.

[0125] The attenuator 301 , 401 is controller by the SOM 502 and is a 7-bit RF digital step attenuator (DSA) providing an attenuation range of 31 .75 dB in switchable steps of 0.25 dB. This device is used to adjust the level of an input signal to the demodulator 302, 402 to ensure that a mixer within the demodulator 302, 402 is not saturated. The demodulator 302, 402 is a direct conversion IQ demodulator with DC offset and second order input intercept point (I I P2) control. Like with the attenuator 301 , 401 , the potentiometer 303, 403 is SOM 502 controlled. The potentiometer 303, 403 is a digitally variable analogue potentiometer used to provide four analogue control voltages that interface with the quadrature demodulator 302, 402 to optimise its DC offset correction and 11 P2 performance.

[0126] Two 304, 404 of the three filters 304, 305, 404, 405 connected to the demodulator 302, 402 are low pass filters each with a 65 MHz cut-off frequency and filters out higher order harmonics produced by the mixing process within the quadrature demodulator 302, 402. The remaining filter 305, 405 is a low pass filter with a 1 GHz cut-off frequency to filter out noise and any higher order harmonic components in the local oscillator signal that drives the quadrature demodulator 302, 402. The amplifier 306, 406 is controlled by the SOM 502 and comprises dual high- performance digitally controlled variable gain amplifiers (DVGAs) used to optimise signal levels of the demodulated and filtered IQ signals priorto processing by the dual analogue to digital converters (ADCs) 310, 410. This is to ensure that the signal levels do not saturate the ADCs 310, 410.

[0127] Each of the two filters 308, 408 connecting the DVGAs 306, 406 to the ADCs 310, 410 is a low pass filter with 65 MHz cut-off frequency which filters out noise and any remaining higher order harmonics that may have been amplified by the DVGAs 306, 406. The ADCs 310, 410 are dual-channel analogue to digital converters (ADCs) with 14-bit precision and 125 Mega-bit per second (MBPS) sampling rate, which convert the filtered analogue IQ signal streams produced by the quadrature demodulator 302, 402 to signals in the digital domain which are then processed by the SOM 502.

[0128] Figure 7 is a block diagram of the SOM 502 of the RF monitoring apparatus 802 of Figures 4 and 5. As illustrated in Figure 7, a FPGA is located within the SOM 502 which in turn is part of a digital controller providing digital control for the RF monitoring apparatus 802. In addition to the SOM 502, the digital controller 500 comprises an ADC 501 , a power- on reset (PoR) facility 503, a first ethernet controller 510, a second ethernet controller 520, a serial port 530, and a number of alarm relay outputs and analogue input ports 506. Furthermore, the digital controller 500 comprises circuitry 504 including a number of level shifting, input / output (I / O) expanders, and user interface circuitry such as user interface circuits that interface the user I / Os comprising ethernet controllers 510, 520.

[0129] The ADC 501 is a four-input 12-bit ADC with an l2C-compatible output. Signal levels present at the three RF receiver input ports 126 are sampled via the couplers 1262 of the three RF receiver input ports 126, adjusted in gain by the amplifier and attenuator combinations 1264 of the three RE receiver input ports 126 respectively, and then measured by the logarithmic power detectors 1266 of the three RF receiver input ports 126 respectively, which provide for each RF receiver input port 126 an analogue output voltage that is linearly related to an incoming receiver signal level. The voltage levels are converted to signals in the digital domain by the ADC 501 and then sent to the SOM 502 via the I2C interface for processing and reporting via a graphical user interface.

[0130] The PoR facility 503 is connected to the SOM 502 such that various voltage rails associated with a central processing unit within the SOM 502 to be constantly monitored using voltage detector integrated circuits. The PoR facility 503 is configured to trigger a hardware reboot should a fault occur in one of the rails and will keep the central processing unit disabled until the voltage rails have stabilized. A manual reset button is also provided for servicing purposes.

[0131] As indicated, the circuitry 504 includes level shifting, I / O expanders, and user interface circuitry:

[0132] • Circuits for voltage level shifting between 1 .8 V DC and 3.3 V DC voltage rails to be carried out for signals that control various devices (such as attenuators and RF switches of the receivers 300, 400) depending on different operating voltages that such various devices (which need to interface with each other) may need.

[0133] • I / O expanders with 16-bit capacity and high-speed serial peripheral interfaces (SPIs) that can be used to provide additional I / O port capacity over and above that provided by the central processing unit of the SOM 502.

[0134] • User interface circuits that interface the user I / Os such as the ethernet controllers 510, 520, a serial port 530, the alarm relay output ports / analogue input ports 506, and a SD card 508. The analogue input ports 506 are connected to a four-channel ADC with 16-bit precision and I2C interface. The analogue input voltages are converted to signals in the digital domain by the ADC and then sent to the SOM 502 via the I2C interface for processing and reporting via a graphical user interface.

[0135] The alarm relay outputs and analogue input ports 506 provide four clean relay contacts which may be programmed to energise under certain alarm conditions. These contacts may be utilised by a radio site network controller to integrate the alarm indications with other network parameters. As indicated above, four analogue inputs are also provided which may be used with external devices at a radio site such as temperature sensors, door sensors, and / or connected directly to back-up batteries, for example, to monitor their voltage. As illustrated in Figure 7, a secure digital (SD) card 508, which can be read or written to, can be used to provide a secondary facility for a user to save historical data to or to perhaps upload software updates in future. A person skilled in the art would appreciate that such a SD card 508 may not be needed and so is optional as a peripheral device.

[0136] The first ethernet controller 510 comprises an ethernet physical layer transceiver, and transformers to connect the transceiver to a RJ45 twisted pair media. The transceiver interfaces directly to the MAC layer and provides precision clock synchronization and a synchronous ethernet clock output. The first ethernet controller 510 also comprises a dedicated 25 MHz crystal oscillator that provides the stimulus for the transceiver’s internal reference clock.

[0137] Like with the first ethernet controller 510, the second ethernet controller 520 comprises an ethernet physical layer transceiver and transformers to connect the transceiver to a RJ45 twisted pair media, and the transceiver interfaces directly to the MAC layer and provides precision clock synchronization and a synchronous ethernet clock output. For the second ethernet controller 520, a 25 MHz clock generated by a clock network 900 provides the stimulus for the transceiver’s internal reference clock. The use of this external clock enables synchronous ethernet capability across a multi-site network comprising multiple RF monitoring apparatuses 802. This may enable features such as geolocation of interfering transmission sources by examining time of arrival delta of occurrence of an interfering transmission at each site of a multi-site network.

[0138] The serial port 530 is provided for connection to any legacy devices such as any accessory to the RF monitoring apparatus 802 including any site alarm modules (SAMs) that can extend the number of analogue and digital alarm inputs.

[0139] Figure 8 comprises a block diagram of a transmitter / signal generator 600 of the alternative RF monitoring apparatus 802 and a clock network 900 of the RF monitoring apparatus 802.

[0140] Beginning first with the transmitter / signal generator 600, which is an inbuilt signal generator that is configured to provide an antenna isolation measurement functionality, the transmitter / signal generator 600 comprises a signal generator output port to which a signal generator output can also be steered to provide the functionality of a signal generator which is normally broughtto site as a standalone piece of test equipment. In this embodiment, the signal generator 600 is configured to generate an unmodulated continuous wave (CW) signal. However, it is envisaged that alternative embodiments of the RF monitoring apparatus 802 may be implemented with a transmitter / signal generator 600 that is configured to generate modulated signals using different modulation schemes including, but not limited to, APCO P25 Phase 1 & 2, TETRA, and DMR. In this respect, a person skilled in the art would appreciate that such modulated signals can then be used to implement a receiver sensitivity measurement capability.

[0141] Components of the transmitter / signal generator 600 include dual low power digital to analogue converters (DACs) 602 with 14-bit precision and 125 Mega-bit per second (MBPS) sampling rate. The DACs 602 are configured to convert signals in the digital domain from the SOM 502 to analogue IQ signal streams, that is, differential baseband I and Q signals that can be used to modulate an RF carrier.

[0142] The transmitter / signal generator 600 also comprises two filters 604, a modulator 606, a first attenuator 608, a second attenuator 610, a switchable modulator filter 612, and a RF switch 614. The two low pass filters 604 are filters with 10 MHz cut-off frequency for filtering out noise and any higher order harmonics in the baseband I and Q signal streams that may have been produced by the dual DACs 602. The modulator 606 is a direct conversion low power IQ modulator configured to direct modulate the differential baseband I and Q signals on an RF carrier such that the frequency of the RF carrier so produced is determined bythe frequency of the local oscillatorsignal inputto the modulator 606. As will be described below, the local oscillator signal is generated by the clock network 900.

[0143] The first attenuator 608 is a fixed 3 dB Pi attenuator that can be used to mitigate the possibility of over-driving the following linear amplification stages. The second attenuator 610 is 7-bit RF digital step attenuator (DSA) that is controlled by the SOM 502, providing an attenuation range of 31 .75 dB in switchable steps of 0.25 dB. This device is used to adjust the level of the output signal of the signal generator 600, which can be set via a graphical user interface. The switchable modulator filter 612 comprises a series of low-pass or bandpass filters with differing cutoff frequencies covering a range of 120 - 3500 MHz, one of which is selected via a pair of electronic RF multi-throw switches and placed in series with the modulated RF carrierto filter out any noise and unwanted harmonics in the output of the signal generator 600. The multi-throw switches are controlled by the SOM 502, and filter choice is determined by RF carrier frequency selection. The multi-throw switches are high isolation, low insertion loss, single pole 12-throw RF signal routing CMOS devices. For each of the multi-throw switches, 4-bit control outputs are produced by an I / O expander with 16- bit capacity and high-speed serial peripheral Interface (SPI) that is controlled by the SOM 502 via the SPI.

[0144] The RF switch 614 is a single pole 6-throw, high isolation, low insertion loss RF signal routing CMOS switch for selecting the port to which the output of the signal generator 600 is routed.

[0145] Turning now to the clock network 900 illustrated in Figure 8, the clock network 900 is an oscillator network that is configured to generate a variety of clock signals that are used by a number of devices of the RF monitoring apparatus 802, and comprises a primary oscillator that can be calibrated against an external 10 MHz reference signal if one is available on the radio site at which the RF monitoring apparatus 802 is installed.

[0146] The clock network 900 also comprises a generator 908, a RF synthesizer 906, a number of attenuators 904 and a number of filters 902. The generator 908 is an ultra-low jitter clock generator with a temperature compensated crystal oscillator (TCXO) which sets the prime oscillator input frequency at 24.576 MHz. The clock generator 908 provides up to eight clock outputs with up to six different clock frequencies.

[0147] The RF synthesizer 906 is a high performance wideband RF synthesizer with integrated VCO that supports an RF output frequency range from 20 MHz to 5.5 GHz. The synthesizer 906 has a high-speed serial peripheral interface (SPI) through which the synthesizer 906 is controlled by the SOM 520. The output of the synthesizer 906 is a local oscillator signal that in this case is used by the quadrature demodulator in receiver 300.

[0148] Each of the attenuators 904 is a fixed 3 dB Pi attenuator used to mitigate the possibility of over-driving the following linear input stages that the local oscillator signal connects to. Each of the filters 902 is a low pass filter with 1 GHz cut-off frequency to filter out noise and any higher order harmonic components in the local oscillator signal that drives the quadrature demodulator 302 of the RF receiver 300, the quadrature demodulator 402 of the RF receiver 400, and the quadrature modulator 606 of the transmitter / signal generator 600.

[0149] Figure 9 is a block diagram of a power supply unit (PSU) 700 and power supply regulators 790 of the RF monitoring apparatus 802. The PSU 700 is an isolated PSU with the following input and outputs:

[0150] • Input: o 12 - 60 V DC

[0151] • Output: o 1 x 5.0 V DC 5.5 A Rail o 1 x 5.0 V DC 2.0 A Rail o 1 x 6.0 V DC 3.3 A Rail

[0152] The isolated PSU 700 comprises input circuitry 720 for inrush current control with current limiting and power dissipation control of series pass N-channel MOSFET devices ensuring they operate within their safe operating area (SOA). In this respect, it is envisaged that PoE may not be implemented in alternative embodiments of the RF monitoring apparatus 102 and so components related to PoE may not be fitted. However, this embodiment of the RF monitoring apparatus 802 does include some PoE provision circuitry

[0153] 760.

[0154] The isolated PSU 700 also includes circuitry 780forthe above-mentioned output rails which are shielded from the input circuitry in 720, and further conditioned to be noise-free. Precision power consumption monitors with I2C interfaces are included on each rail. The monitors report current, bus voltage, power consumption and temperature back to the SOM 502 over the I2C interface for alarm monitoring purposes.

[0155] As illustrated in Figures 4 to 9, the RF monitoring apparatus 802 also comprises a number of low noise low-Dropout (LDO) voltage regulators 790 that are scattered throughout the circuits of the RF monitoring apparatus 802 to provide localized low voltage rails for various chipsets that are used to implement the chipsets. These voltage regulators provide 3.3 and 1 .8 V DC rails from the main 5.0 V DC rails, and additional 5.0 and 3.3 V DC rails from the main 6.0 V DC rail.

[0156] Figure 10 is a block diagram of a test port 8000 of the RF monitoring apparatus 802. The test port 8000 is bidirectional with switching, attenuator and amplifier gain settings controlled by the SOM 502. Components within the test port 8000 include a RF switch 8120, and a number of switches 8122 corresponding to the RF transmitter input ports 116, 118 and the RF receiver input ports 126. Each of the switches 8122 is a high isolation, low insertion loss CMOS switch designed for RF applications, covering 10 - 3000 MHz.

[0157] For a switch in relation to a RF forward input port 116, the switch 8122 either routes the signal at the coupled output of the coupler 1164 of the RF forward input port 116 through to the following switch input of the RF switch 8120 or to an open circuit. The latter mode provides additional isolation of this signal when the test port 8000 is configured to output / input a different signal.

[0158] The RF switch 8120 is a high isolation, single pole 12-throw, low insertion loss RF signal routing CMOS switch with an operational bandwidth of 10 - 8000 MHz. This switch 8120 is controlled by the SOM 502. The RF switch 8120 is configured to select input ports 8116, 8118, 8126 or 8300 when the test port 8000 is used as an output port, and an auxiliary output port 8200 when the test port 800 is used as an input port, for example, for connection to an external test antenna or signal generator.

[0159] The test port output port 8200 connects to an RF switch feeding into the first receiver 300. This carries a signal injected into the test port 8000 when the test port 8000 is used as an input port. The input port 8300 is a signal generator input port that connects to the RF switch 614 of and carries a signal generated by the transmitter / signal generator module 600. This signal is then available at the test port 8000 for testing purposes.

[0160] Figure 11 is an illustration of software stack of the RF monitoring apparatus 802. Figure 12 is an illustration of the RF monitoring apparatus 802 (“Site Vantage”). Figure 13 is an illustration of the RF monitoring apparatus 802 as implemented with an antenna line coupler and other components of a RF wireless system. Figure 14 is a table setting out the technical specification of the RF monitoring apparatus 802

[0161] As illustrated in Figures 12 and 13, the architecture of the RF monitoring apparatus 802 features both hardware and software. As indicated above, the RF monitoring apparatus 802 is configured to support new innovative RF monitoring capabilities including, but not limited to, fast monitoring of forward and reflected transmitted power per channel, measuring transmitter (Tx) to receiver (Rx) antenna isolation, and monitoring Rx RSSI levels for up to 80 channels. It is envisaged that the RF monitoring apparatus 802 can be implemented to provide broadband monitoring capability, allowingfor RF monitoring in dual or multiband sites using a single device.

[0162] The RF monitoring apparatus 802 is implemented with three separate forward and reflected paired power inputs 116, 118, as well as three separate receive monitoring inputs 126, and so allows monitoring of multiple transmit combiners and antennas, while also supporting Rx diversity systems or a standalone monitoring antenna, all within one device. Also, it would be apparent to a person skilled in the art that the RF monitoring apparatus 802 is not merely compatible with an existing site alarm module (SAM) but also features onboard analogue and digital Inputs as well as alarm outputs.

[0163] Finally, it is envisaged that RF tests may be available on both the RF monitoring apparatus 102 of Figure 2 and the RF monitoring apparatus 802 of Figures 4 to 14. In a typical radio site, a transmitter multi-coupler may serve to combine multiple transmitters to a single transmit antenna. The transmitter multi-coupler may also used for “transmitter noise suppression” to also filter out noise that emanates from the transmitter at receive frequencies using mechanical coaxial resonator filters, as the noise may cause receiver desensitisation if not controlled and filtered out to levels below the baseline receiver sensitivity.

[0164] At the receiver side, a receive antenna connects to a mechanical resonator preselector filter forming part of a receiver multi-coupler, which has a passband that is wide enough to pass all of receive frequencies at the site but heavily attenuates the transmitter frequencies. This filter provides “transmitter carrier suppression”, such that high carrier levels, that would otherwise block the receivers and cause receiver desensitisation, are controlled and suppressed.

[0165] The RF tests that may be available on both the RF monitoring apparatus 102 of Figure

[0166] 2 and the RF monitoring apparatus 802 of Figures 4 to 14 include: o Antenna Isolation - A test signal at a known level is generated by the internal signal generator 600, on a frequency that lies within a receiver preselector frequency band, and is sent to a transmit antenna 104, 106 via a RF reverse coupled port 119 on the receiver multi-coupler. This test signal is then picked by a receive antenna 108 and the signal level at the corresponding RF receive port 126 is measured from which a transmit to receive antenna isolation is calculated, such that the parameter may then be used to assist in the mitigation of receiver desensitisation. o Transmitter Carrier Rejection - Activity on a RF forward port 116 of the transmitter multi-coupler is monitored, and channel signal levels are measured. At the same time, the same transmit channel frequencies are measured at a RF receiver port 126. The signal levels are then compared and isolation is then calculated. The level of isolation corresponds to the level of transmitter carrier suppression provided by a combination of antenna isolation and RF preselector filtering at the site. The performance of the filtering can then be ascertained given the previous antenna isolation measurement result.

[0167] As will be appreciated from the foregoing description, the configuration of the monitoring apparatus 102, 802, and in particular the provision of programmable processor 202, 502, provides for a very high degree of flexibility and adaptability, particularly through software modifications in order to implement desired new features from time-to-time. For example, it is envisaged that advanced software features, enabling automated periodic RF site maintenance and facilitating remote troubleshooting and fault finding, may be implemented. Examples of such advanced features include:

[0168] • Receiver desensitization detection (this occurs on a site when a radio base station receiver’s sensitivity is reduced due to inadequate filtering of transmitter noise and carrier levels, or rogue transmissions)

[0169] • Spectrum analysis • Fleet configuration management and diagnostics

[0170] • Automated reporting

[0171] • Illegal transmitter carrier detection

[0172] • Illegal transmitter carrier location determination via triangulation (where a network has multiple transmission sites each fitted with the RF monitoring apparatus 802)

[0173] • Receiver sensitivity baseline measurement

[0174] • Passive Intermodulation (PIM) discovery

[0175] • Al-based fault diagnosis and prediction

[0176] • Complex signal modulation schemes for the in-built signal generator (APCO

[0177] 25 Phase 1 & 2, DMR, TETRA, etc.)

[0178] Accordingly, it will be appreciated that the particular exemplary features and functions described herein are not intended to be exhaustive of all possible functionality provided within various embodiments of the invention. It will be understood that many variations of the present invention are possible, and the overall scope is as defined in the claims appended hereto.

[0179] It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission thatthe prior art forms a part of the common general knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

CLAIMS1 . A radio frequency (RF) monitoring apparatus (802) for monitoring parameters of and / or derived from signals on a plurality of RF channels of a radio network protocol, comprising: a plurality of pairs of RF transmitter input ports (116, 118), each pair of RF transmitter input ports (116, 118) corresponding to a respective one of the plurality of RF channels and comprising a RF forward input port (116) and a corresponding plurality of RF reverse input port (118) receiving, in use, forward-propagating and reverse-propagating fields respectively, of a RF transmitter (104), within an operational bandwidth of the RF monitoring apparatus (802); a first RF channel switch (312) comprising a plurality of first switch input ports (1 FWD1 SW, 1 FWD2 SW, 1 FWD3 SW, 1 REV1 SW, 1 REV2 SW, 1 REV3 SW), and a second RF channel switch (412) comprising a plurality of second switch input ports (2FWD1 SW, 2FWD2 SW, 2FWD3 SW, 2REV1 SW, 2REV2 SW, 2REV3 SW), each switch input port (1 FWD1 SW, 1 FWD2 SW, 1 FWD3 SW, 1 REV1 SW, 1 REV2 SW, 1 REV3 SW, 2FWD1 SW, 2FWD2 SW, 2FWD3 SW, 2REV1 SW, 2REV2 SW, 2REV3 SW) corresponding to one of the RF transmitter input ports (116, 118); a first receiver (300) comprising a first receiver RF input port (Rx PATH 1) and a first digital output port, and a second receiver (400) comprising a second receiver RF input port (Rx PATH 2) and a second digital output port; and a microprocessor configured to generate a plurality of control signals for transmission from a plurality of control output ports (SW_FWD1 , SW_FWD2, SW_FWD3, SW.REV1 , SW_REV2, SW_REV3, 1SW12_RX_V1 , 1SW12_RX_V2, 1SW12_RX_V3, 1SW12_RX_V4, 2SW12_RX_V1, 2SW12_RX_V2, 2SW12_RX_V3, 2SW12_RX_V4) respectively, to selectively couple the first receiver RF input port (Rx PATH 1 ) and the second receiver RF input port (Rx PATH 2) to a RF forward input port (116) and a corresponding RF reverse input port (118), such that (a) a RF forward signal corresponding to a forwardpropagating field is switched to one of the first receiver (300) and the second receiver (400) at or around the same time (b) a corresponding RF reverse signal corresponding to the reverse-propagating field corresponding to the forward-propagating field is switched to the other one of the first receiver (300) and the second receiver (400),wherein the first receiver (300) is configured to generate a first digital signal for transmission from the first digital output port and the second receiver (400) is configured to generate a second digital signal for transmission from the second digital output port, such that at least one electronic signal corresponding to the RF forward signal and the corresponding RF reverse signal can be generated by the microprocessor based on the first digital signal and the second digital signal for output by the apparatus (802) to monitor at least one parameter of and / or derived from at least one signal on at least one of the plurality of RF channels on the radio network protocol.

2. The apparatus of claim 1 , wherein each RF transmitter input port (116, 118) comprises a RF transmitter input port switch (1168, 1188).

3. The apparatus of claim 2, wherein the plurality of control signals comprises a plurality of RF transmitter control signals (SW_FWD1 , SW_FWD2, SW_FWD3, SW_REV1 , SW_REV2, SW_REV3), and wherein the RF transmitter input port switch (1168, 1188) of each RF transmitter input port (116, 118) is controlled by one of the RF transmitter control signals (SW_FWD1 , SW_FWD2, SW_FWD3, SW_REV1 , SW_REV2, SW_REV3) to selectively couple the RF transmitter input port (116, 118) to one of the first RF channel switch (312) and the second RF channel switch (412).

4. The apparatus of claim 3, wherein the plurality of RF transmitter control signals (SW_FWD1 , SW_FWD2, SW_FWD3, SW_REV1 , SW_REV2, SW_REV3) comprises a plurality of RF forward control signals (SW_FWD1 , SW_FWD2, SW_FWD3) and a corresponding plurality of RF reverse control signals (SW_REV1 , SW_REV2, SW_REV3), wherein the RF transmitter input port switch (1168) of each RF forward input port (116) is controlled by one of the RF forward control signals (SW_FWD1 , SW_FWD2, SW_FWD3) to selectively couple the RF forward input port (116) to one of the first RF channel switch (312) and the second RF channel switch (412), and wherein the RF transmitter input port switch (1188) of a RF reverse input port (118) corresponding to the RF forward input port (116) is controlled by a corresponding one of the RF reverse control signals (SW_REV1 , SW_REV2, SW_REV3) to selectively couple the RFreverse input port (118) to the other one of the first RF channel switch (312) and the second RF channel switch (412).

5. The apparatus of any one of claims 1 to 4, wherein the plurality of control signals comprises a set of first RF channel switch control signals (1SW12_RX_V2, 1SW12_RX_V3, 1SW12_RX_V4) and a set of second RF channel switch control signals (2SW12_RX_V1 , 2SW12_RX_V2, 2SW12_RX_V3, 2SW12_RX_V4), and wherein at least one of the set of first RF channel switch control signals (1 SW12_RX_V2, 1 SW12_RX_V3, 1 SW12_RX_V4) is transmitted to the first RF channel switch (312) and at least one of the set of second RF channel switch control signals (2SW12_RX_V1 , 2SW12_RX_V2, 2SW12_RX_V3, 2SW12_RX_V4) is transmitted to the second RF channel switch (412).

6. The apparatus of claim 5, wherein the first RF channel switch (312) is controlled by the at least one of the set of first control signals (1SW12_RX_V1 , 1SW12_RX_V2, 1 SW12_RX_V3, 1 SW12_RX_V4) to selectively couple one of the plurality of first switch input ports (1 FWD1 SW, 1 FWD2 SW, 1 FWD3 SW, 1 REV1 SW, 1 REV2 SW, 1 REV3 SW) to the first receiver (300), and wherein the second RF channel switch (412) is controlled by the at least one of the set of second control signals (2SW12_RX_V1 , 2SW12_RX_V2, 2SW12_RX_V3, 2SW12_RX_V4) to selectively couple one of the plurality of second switch input ports (2FWD1 SW, 2FWD2 SW, 2FWD3 SW, 2REV1 SW, 2REV2 SW, 2REV3 SW) to the second receiver (400).

7. The apparatus of any one of claims 1 to 6, wherein each one of the first receiver (300) and the second receiver (400) comprises a quadrature demodulator (302, 402), a digital variable gain amplifier (DVGA) (306, 406), and dual analogue to digital converters (ADCs) (310, 410) each operating with a sampling rate of 125 Megabits per second (MBPS).

8. The apparatus of claim 7, wherein the quadrature demodulator (302, 402) of each of the first receiver (300) and to the second receiver (400) is coupled to a digital potentiometer (303, 403),wherein the digital potentiometer (303) of the first receiver (300) is configured to optimize the quadrature demodulator (302) of the first receiver (300) to demodulate one of the RF forward signal and the corresponding RF reverse signal to an in-phase (11) signal and a separate quadrature (1 Q) signal, and wherein the digital potentiometer (403) of the second receiver (400) is configured to optimize the quadrature demodulator (402) of the second receiver (400) to demodulate the other one of the RF forward signal and the corresponding RF reverse signal to an in-phase (2I) signal and a separate quadrature (2Q) signal.

9. The apparatus of claim 7 or 8, wherein each quadrature demodulator (302, 402) is configured to demodulate one of the RF forward signal and the corresponding RF reverse signal to an Intermediate Frequency (IF).

10. The apparatus of claim 9, wherein for each one of the first receiver (300) and the second receiver (400), the in-phase (11, 2I) signal and the quadrature (1 Q, 2Q) signal are filtered by two separate low-pass filters (304, 404) to remove any upper image frequencies.

11. The apparatus of claim 10, wherein the filtered signals (1 IF A, 11F B) are amplified by the digital variable gain amplifier (DVGA) (306, 406), and the amplified signals (OUT A, OUT B) are then filtered again by another two separate low-pass filters (308, 408).

12. The apparatus of claim 11 , wherein the twice low-pass filtered signals (INA, INB) are separately converted by the dual analogue to digital converters (ADCs) (310, 410) to a digital signal for transmission.

13. The apparatus of claim 12, wherein the digital signal for transmission comprises a digital in-phase (I) output stream and a separate digital quadrature (Q) output stream.

14. The apparatus of any one of claims 1 to 13, wherein the microprocessor is part of a digital controller (500) comprising a system on module (SOM) (502) on which a field programmable gate array (FPGA) is located.

15. The apparatus of claim 14 when dependent on claim 13, wherein the microprocessor is configured to control the field programmable gate array (FPGA) to decimate the digital in-phase (I) output stream and the separate digital quadrature (Q) output stream to a 20 MHz band of RF spectrum.

16. The apparatus of claim 15, wherein the microprocessor is configured to control the field programmable gate array (FPGA) to digitally filter out the at least one of the plurality of RF channels from the decimated streams, such that RF power of each one of the at least one digitally filtered out RF channels can be measured.

17. The apparatus of any one of claims 1 to 16, wherein each pair of RF transmitter input ports (116, 118) is coupled to a respective one of a plurality of signal transmitting cables or antennas.

18. The apparatus of any one of claims 1 to 17, further comprising a plurality of RF receiver input ports (126) each corresponding to one of the plurality of RF channels.

19. The apparatus of any one of claims 18, wherein each RF receiver input port (126) is coupled to a respective one of a plurality of signal receiving cables or antennas.

20. A method of monitoring parameters of and / or derived from signals on a plurality of RF channels of a radio network protocol, comprising: providing a plurality of pairs of RF transmitter input ports (116, 118) for receiving forward-propagating and reverse-propagating fields respectively, of a RF transmitter (104), within an operational bandwidth, each pair of RF transmitter input ports (116, 118) corresponding to a respective one of the plurality of RF channels and comprising a RF forward input port (116) and a corresponding plurality of RF reverse input port (118); selectively coupling a first receiver (300) and a second receiver (400) to a RF forward input port (116) and a corresponding RF reverse input port (118), such that (a) a RF forward signal corresponding to a forward-propagating field is switched to one of the first receiver (300) and the second receiver (400) at or around the same time (b) a corresponding RF reverse signal correspondingto the reverse-propagating field correspondingto the forward-propagating field is switched to the other one of the first receiver (300) and the second receiver (400); and generating a first digital signal for transmission from the first receiver (300) and a second digital signal for transmission from the second receiver (400), such that at least one electronic signal corresponding to the RF forward signal and the corresponding RF reverse signal can be generated based on the first digital signal and the second digital signal for output to monitor at least one parameter of and / or derived from at least one signal on at least one of the plurality of RF channels on the radio network protocol.

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