KR0123396B1 - Output power detector - Google Patents

Abstract

An output power detector for multi-channel system using linear amplifier is disclosed, which is suitable to measure output level of a specific channel in a multi-channel system such as mobile and satellite communication. The detector comprises a directional coupler for sampling a part of transmitting signal in order to detect signal level of each channel; an 1/n separator for separating the signal as per the numbers(n) coupled at the input of linear amplifier; a mixer for down converting the corresponding RF signal into an intermediate frequency; a local frequency oscillator for generating a local frequency as per the command of a controller; a filter for passing the RF signal within the converted multiple signals; a power level detector for providing the controller with an analog voltage converted from the filtered RF signal level; and a controller for transmitting a specific information data to the local frequency oscillator so as to generate a local frequency based on the received information on the final output level of the RF signal.

Description

Output Power Detector

1 is a circuit diagram of a multi-channel system to which the present invention is applied.

2 is a diagram showing a frequency spectrum of a signal for each first point.

* Explanation of symbols for main parts of the drawings

1a, lb,... , 1n,; 7a, 7b,... 7n: mixer,

2a, 2b,... , 2n; 50a, 50b,... , 50n: local frequency generating circuit,

8a, 8b,... , 8n; Intermediate frequency filter, 9a, 9b,... , 9n; Power level detector,

10a, 10b,... , 10n; Upconverter, 20; Linear amplifier,

30; Directional coupler, 40: 1: 1 n separator,

60a, 60b,... , 60n; Output power measurement unit, 70a, 70b,... , 70n; Controller.

The present invention relates to an output power measuring apparatus, and more particularly, to an output power measuring apparatus in a multi-channel system using a linear amplifier.

When amplifying channels in a multi-channel system, a recent trend is to use a linear amplifier with good intermodulation characteristics.

Unlike the conventional method of amplifying each channel using non-linear amplifiers and then using a channel combiner, amplifying the combined signal using one linear amplifier after combining each channel before amplifying the signal, in particular an analog mobile communication system. Advanced Mobile Phone System (AMPS) has begun to use linear amplifiers due to the loss of channel combiners, and linear amplifiers will be used in multi-channel CDMA systems, which are being developed in Korea. to be.

However, in the case of the linear amplifier, there is an advantage that the intermodulation does not occur, but it is very difficult to measure the output power of each channel because each channel is input after being combined.

To solve this drawback, we can think of how to use the variable bandpass filter to filter only the desired channel and then measure the power.It is difficult to make narrowband bandpass filter at high transmission frequency and whenever the channel frequency of the system changes The disadvantage is that you have to adjust the center frequency of the filter manually.

Accordingly, an object of the present invention is to provide an output power measuring apparatus having a simple structure, easy to implement, and capable of automatically responding to a change in frequency of a channel.

In order to achieve the above object, the present invention includes a directional coupler for extracting a portion of the signal to be transmitted to know the signal magnitude of each channel; Separating the signal by the number n of the combined signal at the input of the linear amplifier 1; n separator; A mixer for downconverting the corresponding RF signal of the combined RF signal to an intermediate frequency; A local frequency generator circuit for generating a local frequency in response to a controller command; A filter for filtering only a corresponding RF signal among multiple signals converted to an intermediate frequency; A power level detector for converting the magnitude of the RF signal filtered by the filter into an analog voltage and sending it to a controller; And a controller for transmitting predetermined information to the local frequency generating circuit so as to receive local information about the final output level of the corresponding RF signal to create a local frequency.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention. 1 is a circuit diagram of a multi-channel system using a linear amplifier, wherein reference numerals 1a, 1b,. , 1n, 7a, 7b,... , 7n is a mixer, 2a, 2b,... , 2n, 50a, 50b,... , 50n is a local frequency generating circuit, 8a, 8b,... 8n is an intermediate frequency filter, 9a, 9b,... , 9n is a power level detector, 10a, 10b,... 10n is an up-converter, 20 is a linear amplifier, 30 is a directional coupler, 40 is a 1: n separator, 60a, 60b,... , 60n denotes the output power measurement unit, 70a, 70b,... And 70n represent controllers, respectively.

Looking at the configuration and operation with reference to Figure 1 as follows.

The plurality of up-converters 10a, 10b, ..., 10n receive the commands of the controllers 70a, 70b, ..., 70n to generate the corresponding local frequency (LO # 1 to LO #n). 2b, ..., 2n) and a mixer (1a, 1b, ..., ln) which converts a transmission signal having an intermediate frequency (IF) into an allocated RF (Radio Frequency) signal by mixing with the local frequency. The frequency of the signal to be transmitted is upconverted into the assigned RF signals RF # 1 to RF #n. Here, the local frequency generating circuits 2a, 2b, ..., 2n and the local frequency generating circuits 50a, 50b, ..., 50n, which will be described later, are all made of the same hardware. Generate. The linear amplifier 20 amplifies the multiplexed signals (RF # 1 + RF # 2 + RF # n) combined with the RF signals without intermodulation.

The directional coupler 30 extracts a portion of the signal to be transmitted to know each signal size of the multiple RF channel signal amplified by the linear amplifier 20. And 1: n separator 40 separates the signal by the number n of the combined signal at the input of linear amplifier 20. The multiple RF channel signals separated in this way are input to the respective output power measuring units 60a, 60b, ... 60n so that only a desired channel signal passes and a filter for removing other RF channel signals is required.

However, in the RF band, it is not only difficult to fabricate an RF channel filter with a good cut-off characteristic enough to remove other RF channel signals that are close in frequency, but even if manufactured, the RF of the channel allocated to the system If the frequency is changed, it is difficult to readjust the passband frequency of the filter.

On the other hand, each of the output power measuring units 60a, 60b, ..., 60n as described above includes mixers 7a, 7b, ..., 7n, intermediate frequency filter 8a, 8b, ..., 8n, power level detectors 9a, 9b, ..., 9n). The mixers 7a, 7b, ..., 7n down convert the corresponding RF channel signal of the combined RF channel signal to an intermediate frequency. The intermediate frequency filter (8a, 8b, ..., 8n) is a bandpass filter having the same characteristics, the intermediate frequency is the center frequency of the filter, and filters the corresponding RF channel signal plate among the multiple RF channel signals converted to the intermediate frequency. . The power level detectors 9a, 9b, 9n convert the magnitudes of the RF channel signals filtered by the intermediate frequency filter into analog voltages and send them to the controllers 70a, 70b, 70n.

A plurality of local frequency generating circuits 50a, 50b, ..., 50n not in the upconverter receive the commands of the controllers 70a, 70b, ..., 70n to receive local frequencies LO # 1-L0 #n. To the mixers 7a, 7b, ..., 7n. By using the local frequency generating circuits 50a, 50b, ..., 50n in this manner, it is not necessary to supplement the circuit for measuring the power level even if the channel frequency of the system is changed. The local frequency at this time is the same as the local frequency used by the upconverters 10a, 10b, ..., 10n of the RF channel for which the output power is to be measured. That is, for example, the local frequency of the local frequency generation circuit 2a in the upconverter 10a connected to the controller 70a and the local frequency of the local frequency generation circuit 50a connected to the controller 70a are the same.

Accordingly, for example, when the output power of the RF # 1 is to be measured, the local frequency of the output power measuring unit 60a may output a signal such as the local frequency signal LO # 1 used in the up-converter 10a. It can be used as a signal. In this case, the outputs of the mixers 7a, 7b, ..., 7n in each output power measurement unit are down-converted to the intermediate frequency IF of the channel to be measured by the measurement unit. The power level detectors 9a, 9b, ..., 9n are input through 8b, ..., 8n. As such, the relatively low frequency intermediate frequency is easier to manufacture than the high frequency RF filter and is much cheaper.

The controller 70a, 70b, ..., 70n receives the information on the final output level of the corresponding RF signal output from each of the power level detectors 9a, 9b, ..., 9n to generate a local frequency. The control command is sent to the generation circuits 2a, 2b, ..., 2n; 50a, 50b, ..., 50n.

As such, the present invention combines the signals at the front end of the linear amplifier in the multi-channel system using the linear amplifier, so that it is difficult to know the output level of each channel at the final output. The local frequency signal used in the converter was mixed again, down-converted to the intermediate frequency, passed through the middle band filter, and the power was measured.

Next, FIG. 2 is a diagram showing the frequency spectrum of each point a to o in FIG.

In FIG. 2, a is the spectrum of the intermediate frequency signal of the upconverter 10a, b is the spectrum upwardly adjusted to RF # 1 via the mixer 1a, and c is the spectrum of the intermediate frequency signal of the upconverter 10b. d is the spectrum up-adjusted to RF # 2 via mixer 1b, e is the spectrum of multiple signals combining the output signals of each upconverter, f is the spectrum of signals amplified by linear amplifier 20, and g is a signal spectrum that couples the amplified multiple signals using the directional coupler 30, h is a signal spectrum obtained by dividing the coupled signal by the number of signals, and i is a signal spectrum down-converted using a mixer. Spectrum, j is the signal spectrum of the up-converter l0a filtered out of the multiple signals, k is the output signal size of the up-converter 10a as an analog voltage through the power level detector 9a, 1 is a coupled signal The signal spectrum divided by the number of signals, m is the mixer (7b) Spectrum of the down-converted signal using n, n denotes the signal spectrum of the upconverter 10b filtered out of the multiple signals, and o denotes the output signal magnitude of the upconverter 10b as an analog voltage through the power level detector 9b. Drawing.

Referring to FIG. 2, it will be described whether automatic response to the frequency change of the channel is as follows.

Considering only RF # 1 and RF # 2 in FIG. 1, the signal input to the linear amplifier 20 is represented by Equation (1). Here, the intermediate frequencies are all the same frequency, but are classified into IFl and IF2 for reference.

RF = RF # 1 + RF # 2 = (IF1 + IF2)... … … … … … … … … … Formula (1)

After the signals have passed through the linear amplifier 20, the directional coupler 30 and the 1: n separator 40, the frequency spectra of the signals reaching the points h and 1 of FIG. 1 are respectively (h), (1). Are the same spectrum.

However, the signals at points i: m after passing through the mixers 7a and 7b in Fig. 1 are the same as in Equations (2) and (3), respectively. The local frequency signal at this time uses the local frequency signal used by the up-converters 10a, 10b, ..., 10n of each signal as it is.

(Signal at point i) = IF1 + (IF1 + 2 * LO # 1) + (IF2 + LO # 2-LO # 1)

+ (1F2 + LO # 2 + LO # 1)… … … … … … … … … … … Formula (2)

(Signal at point m) = (IF1 + LO # 1-LO # 2) + (IF1 + LO # 1 + LO # 2) + IF2

+ (1F2 +2 * LO # 2)... … … … … … … … … … … … Formula (3)

In the above formulas (2) and (3), the second and fourth terms are negligible terms because the frequencies are far apart, and the frequency spectrum in such a case is the same as (i) and (m) in FIG. Referring to (i) of FIG. 2, the RF # 1 channel signal for which power is to be measured is down-converted to an intermediate frequency, and (m) of FIG. 2 shows that the RF # 2 channel signal is down-converted to an intermediate frequency.

The signals passing through the intermediate frequency filters 8a and 8b are shown in Equations (4) and (5), respectively, and the frequency spectrum is shown in (j) and (n) of FIG.

(Signal at point j) = IF1... … … … … … … … … … … … Formula (4)

(Signal at point n) = IF2... … … … … … … … … … … … Formula (5)

Since IF1 and IF2 are in the same frequency band, the passband of the intermediate band filter is irrelevant even if the RF channel frequency is changed. In other words, since all RF channels are identical, the intermediate frequency can be used to measure the power of all channels using one intermediate frequency filter, so there is no need to readjust the passband of the filter even if the RF channel frequency changes.

Therefore, if you want to measure the output power of any RF channel, you only need to input the local frequency signal that the RF channel used in the up-converter through the controller. If you configure a number of output power measurement unit and connect each local frequency signal, even if the RF channel frequency is changed, the changed local frequency signal is input through the controller, so it can respond automatically.

The present invention configured and operated as described above has an advantage that it can be easily implemented by reusing the intermediate frequency generator circuit used in the up-converter. In particular, the output of a specific channel in a system using multiple channels such as mobile communication and satellite communication There is an effect that can be applied when measuring the level.

In addition, the present invention can be applied to digital transmission and reception systems that are actively developed in various fields.

Claims (1)

Local frequency generator circuits 2a, 2b, ..., 2n for generating a local frequency under the command of the controllers 70a, 70b, ..., 70n and RF signals allocated by mixing a transmission signal that is an intermediate frequency with the local frequency Upconverters 10a and 10b, which are composed of mixers 1a, 1b, ..., 1n for converting into radio frequency signals, upconverting the frequency of a signal to be transmitted to a predetermined radio frequency (RF) signal. ,…, 10n); And a linear amplifier 20 configured to amplify the combined multiple signals without intermodulation, wherein the circuitry measures the output power of the multi-channel system, wherein a part of the signals to be transmitted to know the signal size of each channel is used. A directional coupler 30 for extracting; A 1: n separator 40 for separating the signal according to the number n of the combined signal at the input of the linear amplifier 20; A mixer (7a, 7b, ... 7n) for down-converting the corresponding RF signal of the combined RF signal to the intermediate frequency; Local frequency generator circuits 50a, 50b, ..., 50n for generating a local frequency in response to a controller command; Filters 8a, 8b, ..., 8n for filtering only a corresponding RF signal among multiple signals converted into intermediate frequencies; Power level detectors 9a, 9b, 9n for converting the magnitude of the RF signal filtered by the filters 8a, 8b, 8n into analog voltages and sending them to the controllers 70a, 70b, 70n, and The controller 70a for transmitting predetermined information to the local frequency generating circuits 2a, 2b, ..., 2n and 50a, 50b, ..., 50n so as to receive local information on the final output level of the corresponding RF signal. 70b,..., 70n).