Measuring apparatus and method therefor

#The present invention relates to a measuring apparatus of the type used, for example, to measure power of a carrier signal constituting a Radio Frequency (RF) channel, such as a transmit channel of an RF communications systems. The present invention also relates to a method of measuring power, for example, of the carrier signal.

#Manufacturers of receiver amplifiers for use in spread-spectrum communications systems have a requirement to test outputs of the amplifiers during development and quality control processes associated with manufacture of the amplifiers. In this respect, it is necessary to test for correct amplification of carrier signals by a given amplifier and the effect of amplified carrier signals on adjacent, or other, carrier signals. One test for correct amplification of the input carrier signals involves measurement of power, within a predetermined band of frequencies, of amplified carrier signals and predetermined spaces absent of the amplified carrier signals generated by the given amplifier.

#A first known measurement is an Adjacent Channel Power (ACP) measurement; a measure of absolute power leakage from a given transmit channel to adjacent transmit channels. However, the ACP measurement is only made with respect to a single carrier signal, and where more than one channel exists, the absolute power is only measured with respect to a main carrier signal.

#At least one embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

#FIG. 1 is a schematic diagram of an apparatus constituting an embodiment of the invention;

#FIG. 2 is a flow diagram of a method of measuring power for the apparatus of FIG. 1;

#Referring to FIG. 1, a spectrum analyser 100 comprises a microprocessor 102 coupled to an output device, for example a Cathode Ray Tube (CRT) 104 and an input device, for example a keypad 106. The microprocessor 102 is also coupled to a first storage device, for example a volatile memory, such as a Random Access Memory (RAM) 108, and a second storage device, for example a non-volatile memory, such as a Read Only Memory (ROM) 109. It should, of course, be appreciated that other storage means can be employed in place of, or in addition to, the RAM 108 and/or the ROM 109. The spectrum analyser 100 provides an input port 110 to which a cable 112 can be connected, the cable constituting a propagation medium through which an input signal 111 to be measured can propagate to the input port 110. The input port 110 is coupled to the microprocessor 102.

#The keypad 106 comprises an array of numeric keys 114; navigation keys, for example “soft” keys 116 disposed adjacent a rectangular graphical menu 400 (FIG. 4) displayed at a right hand side of the CRT 104; and an “enter” key 118 to confirm certain inputs.

#In operation (FIG. 2), a user powers up (step 200) the spectrum analyser 100. Upon power-up, an option to carry out an MCP measurement appears in a panel (not shown) of the rectangular graphical menu 400, the option being selectable by depressing one of the soft keys 116 that is adjacent the panel (hereinafter referred to as the “MCP measurement key”). Subsequently, one end of the cable 112 is attached to the input port 110, another end of the cable 112 being coupled to a source of the input signal 111, for example a multi-carrier amplifier. In this example, the input signal is a spread spectrum signal comprising four carrier signals, each separated by a space. A space is an absence of a carrier signal. In a given radio standard, for example W-CDMA, a number of potential positions is provided within a predetermined band of frequencies, the positions being spectrally separated by a predetermined spectral spacing. At each of the number of locations, a carrier signal can either be present or absent, an absence of the carrier signal power being known as the “space”.