JPS60228970A - System for measuring carrier wave power/noise power ratio - Google Patents

Abstract

PURPOSE:To measure a carrier wave power/noise power ratio (C/N), by calculating the power ratio of outputs of two filters different in a pass band width. CONSTITUTION:The band width B2 of second BPF3 is set narrowly in a range imparting no strain to a passing signal component and the band width B1 of first BPF2 is set in a range receiving no influence of the other signal so as to be made wider than the band width B2. Then, an input signal 1 is allowed to pass through first BPF2 and only the noise of the input signal 1 receives band restriction. The output signal 5 of first BPF2 passes through second BPF3 and only the noise of the signal 5 receives band restriction. Next, powers of the output signal 5 of first BPF2 and the output signal 4 of second BPF3 are respectively measured by power measuring instruments 6, 7 and measured values 8, 9 are guided to a C/N operation circuit 10 to receive operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for measuring carrier power to noise power ratio on the receiving side of a wireless communication system.

(Background Art) In a wireless communication system, knowing the carrier wave power to noise power ratio (hereinafter referred to as rc/NJ) of a received wave is useful for monitoring the quality of the received signal and also for transmitters making up the communication system.
This is important for monitoring the operating status of receivers, repeaters, etc. In particular, in order to guarantee the line quality specified in the line design, it is desirable that the C/N can be measured and monitored at all times or at any time on the receiving side.

Conventionally, the commonly used C/N measurement method is to measure the noise power within the reception frequency slot when no radio waves are being emitted, such as when setting up a line, and then measure the noise power within the receiving frequency slot after the radio waves have been emitted. , (carrier plus noise) power is measured, and the C/N is calculated from the two measurement results. Although this measurement method has high measurement accuracy, it is not possible to continuously measure C/N during communication.

A C/N measurement method that improves this point is 5CPC (Singl
This can be seen in eChannel per Carrier (eChannel per Carrier) systems and TDMA systems.

For example, in a 5CPC system, a frequency slot is provided for noise measurement, the noise power is measured using the empty slot, the (carrier wave + noise) power is measured in the target slot, and the C/N is determined by calculation. There is.

However, this method has the drawback that if there is a difference in noise density NO between the slot in which the noise power is measured and the target slot, the reliability of the measurement result will be low.

In addition, in the TDMA system, the C7N
(Mizuno et al., “CN ratio measurement method for TDMA satellite communication,” Institute of Electronics and Communication Engineers, IEICE Technical Report C382-73, 19
82, 10). However, with this method, since the unmodulated portion included in one burst is small, it takes a long time to obtain a sufficient number of samples for processing, and measurement accuracy decreases if the signal level fluctuates during this time. . In order to perform measurements in a short period of time, a method of setting unmodulated time slots for noise measurement may be considered, but in this case, the transmission efficiency decreases. Furthermore, these methods have the disadvantage that they can only be measured after carrier phase synchronization has been established, and that they can only be applied to digitally modulated waves.

As described above, the prior art has drawbacks such as requiring special measurement conditions and low measurement accuracy. (Objective of the Invention) The present invention solves the drawbacks of the prior art described above.
Applicable to both analog and digital systems, signal (
The C/C/C
The purpose is to provide a method for measuring N.

The present invention will be described in detail below using the drawings.

(Structure and operation of the invention) A feature of the present invention is that two filters having different passband widths are used, and the C/N ratio is measured from the difference in the output power values of the respective filters.

FIG. 1 shows one embodiment of the present invention, and assumes that the two filters are band pass filters (BPF). In the figure, 2 is a first BPF having a bandwidth B, and 3 is a second BPF having a bandwidth B2.

6.7 is a power measuring device, 10 is a C/N calculation circuit, 11 is a demodulator, and other symbols indicate signals. Here, the band l@B2 of the second BPF is set to be narrow (for example, about the occupied frequency bandwidth of the received wave) within a range that does not cause distortion to the signal components passing through, and the band l@B2 of the first BPF is , is set wider than B2 within a range that is not affected by other signals.

The input signal 1 is an RF multiplied signal or an IF multiplied signal obtained by converting the frequency of the RF multiplied signal, and is a signal in which noise is added to a carrier wave. By passing this input signal 1 through the first BPF 2, only the noise of the input signal 1 is band-limited. The output signal 5 of the 10th BPF 2 is passed through the second BPF 3, so that only the noise of the signal 5 is further band-limited. The output signal 5 of the first BPF 2 and the output signal 40 of the second BPF 3 are measured by power measuring devices 6 and 7, respectively, and the measurement 1 signals 8 and 9 are guided to the C/N calculation circuit 10. .

Here, if the carrier power of the input signal 1 is C1, noise power concealment is No, the output power of the first BPF 2 with i is Pl, and the output power of the second BPF 3 is P2, then PI.

P2 is expressed as follows: P 1'' C+ No Bl... (1) P 2-=
C1No B2 − (2) Furthermore, equations (11, (2
), C/No is determined by the following formula.

The present invention calculates the value of the above equation (3).

If the occupied bandwidth of the input signal 1 is Bw, the C/N within this bandwidth is determined by the following equation.

C/N = c/(No - Bw) - (4) In a communication system, the occupied bandwidth Bw is determined in advance based on line design. The C/N calculation circuit 1 performs the above calculations.
It is o. However, as is clear from the above description, in this embodiment, the unknown quantity in calculating c/N is Pl and P. Therefore, the C/N calculation circuit 11 can achieve this by reading out the digitalized value of PI r B2 from the ROM that stores the calculation result as an address. That is, the C/N arithmetic circuit 10 may be a conversion table in which Pl+P2 is a standard meter.

Here, a modification of this embodiment will be described.

In the demodulator 11, a baseband filter (
usually has a low-pass filter).

The signal power after passing through this baseband filter can be converted into the power P2 of the output signal of the second BPF 3. Therefore, if the power of the baseband filter output is obtained, it can be applied as the signal 9 to the C/N calculation circuit 11 and the second BPF 3 can be removed. however,
It is necessary to convert it into electric power P2 in advance or by the C/N calculation circuit 11.

Next, other embodiments of the present invention will be described.

This example uses AGC (Automatic Galn C
C/N is determined by controlling either Pl or B2 to a known constant value and measuring the other by using the above technology. Figure 2(a).

A configuration example is shown in (b). In both examples (, ) and (b), a power control circuit 12 is provided between the first BPF 2 and the second BPF 3 of the embodiment shown in FIG. The power control circuit 12 controls the signal power (
to carry out (goods).

In the example (a), C/N can be obtained by measuring Pl, and the principle thereof will be described below.

The carrier voltage after passing through the first BPF 2 is 01, the noise power density is N. shall be. Further, the carrier wave power after passing through the power control circuit 12 is C', and the noise power density is NO4.

If the power control circuit operates linearly, C and N
The ratio of o (C/No) is equal to the ratio of C' and NO4 (C'/No).If such a definition is made, the power P1
and B2 are as follows.

P l= C' + No' ・B l-(5) P 2
"=C'10No'.B2-(known) (6) The carrier-to-noise power ratio (C/No) in this case can be expressed as:

In equation (7), the only unknown quantity in determining C/No is pt. Conversion table 17 converts the measurement results of P into equations (4) and (7
) and can be configured in a ROM, for example.

On the other hand, in the example (b), the C/N can be reduced by measuring the unknown e P 2, and the principle is the same as in the example (a). Note that in this embodiment, in addition to the configuration in which power control is performed based on the input power of the second BPF 3 as shown in FIG. 2(b), control is performed based on the output power of the first BPF 2. Configuration is also possible. That is, the former is a feedback type, and the latter is a feedforward type.

The embodiment shown in Figures 2(,) and (b) includes a power control circuit as a component, but in a normal receiver, the demodulator is designed to operate normally even if the input signal level fluctuates. A power control circuit is pre-installed in the device. A first BPF is also usually incorporated for noise removal. Therefore, since it can be implemented using only the powerful port of the second BPF, it can be said to be a C/N method that is inexpensive and has a simple configuration. Furthermore, if a configuration is adopted in which the power after passing through the pace band filter of the demodulator described above is obtained and the power control circuit is operated based on it, a new advantage is added to the receiver configuration. There is no need to add extra calories.

(Effects of the Invention) As explained above, the C/N 111 constant method according to the present invention measures the C/N based on the power difference between two fill outputs having different passband widths. This method can be easily constructed by only having two filters, and still has the advantage of being able to constantly measure C/N in both di-notal and analog communication systems.

Furthermore, in the method that applies a power control circuit, as long as the control circuit is within the range that operates normally (linearly), the power at one point is measured regardless of the receiver input level.
, CZN value is obtained. When applying this method to a 5cpc system, two Bl
If it is made large, it will be influenced by the @ adjacent channel signal. Usually, a guard band is provided in the 5CPC system, so B should include this band.

Just set the value of . This also applies when this method is applied to a TDMA system, and it would be sufficient to adopt a configuration in which C measurement is performed only while each burst is being transmitted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a noise power ratio measuring device according to the present invention, and FIGS. 2(a) and 2(b) are block diagrams of another embodiment of the noise power ratio measuring device according to the present invention. 1... Carrier wave to which noise is added, 2... First BP
F. 3... Second BPF, 6, 7, 14, 16... Power measuring device, 10... C/N calculation circuit, 11... Demodulator, 12... Power control circuit, 17...・Conversion table, etc.・Various signals.

Claims (1)

[Claims] In the receiving system of the communication system, first
and a second filter, the passband width of the second filter is set to be narrow within a range that does not cause distortion to the received signal, and the passband width of the first filter is set to be narrower than the passband width of the second filter. A carrier wave power to noise power ratio measurement method characterized in that the carrier wave power to noise power ratio is set wider and the carrier wave power to noise power ratio is obtained from the relationship between the output power of the first filter and the output power of the second filter.