JPH0414320A - Transmission power amplifier circuit - Google Patents

Abstract

PURPOSE:To decrease output power fluctuation even to a burst signal by providing a sample-and-hold circuit between a DC amplifier and a variable attenuator so as to suppress the transient characteristic of a leading of a control voltage. CONSTITUTION:A sample-and-hold circuit 6 is provided between a DC amplifier 5 and a variable attenuator 6. The circuit 6 outputs its input signal as it is when a sampling pulse (f) is at an H level and latches and outputs a voltage just before the input gets to an L level when the sampling pulse (f) is at an L level. When an input signal (a) is inputted, an output waveform l of an amplifier 5 is a waveform with voltage fluctuation and since the signal l is held by the circuit 6 by using the pulse (f), a control voltage (g) of an attenuator (electronic attenuator) 1 is almost a constant voltage. Since a control voltage just before the intermittent part is kept even to the input having large voltage fluctuation in existence therein, a voltage change to be controlled in following to a new voltage is decreased, the transient phenomenon of the leading is suppessed and an output signal (h) with less output voltage fluctuation is outputted.

Description

Detailed Description of the Invention (Technical Field to Which the Invention Pertains) The present invention relates to a transmitter that transmits intermittently in the form of a transmission output or burst signal, such as a frequency hopping transmitter, in which the transmission output is cut off when switching frequencies. The present invention relates to a transmission power amplification circuit for a transmitter that performs communication using a time division multiplexing multiple access method or a transmitter that performs communication using a time division multiplexing multiple access method.

(Prior art and its problems) FIG. 1 is a block diagram of a normal transmission power amplification circuit.

In FIG. 1, 1 is a variable attenuator (electronic attenuator) whose attenuation varies depending on the control voltage, 2 is a high frequency power amplifier, 3 is a directional coupler, 4 is a detector, and 5 is a DC amplifier.

An input signal passes through an electronic attenuator 1 and is amplified by a high frequency power amplifier 2 to become an output signal. At this time, a part of the output signal is taken out by the directional coupler 3 and detected by the detector 4, thereby obtaining a DC voltage corresponding to the output signal level. This DC voltage is amplified and used as a control voltage for the electronic attenuator 1. In this way, a feedback loop controlled by the attenuation amount or output level of the electronic attenuator 1 is constructed, and the transmission power can be controlled to be kept constant.

FIG. 2 shows the waveforms of various parts when a burst signal wave is input to this circuit as an input signal. In Figure 2, a
is the input signal, b is the control voltage of the electronic attenuator, and C is the output signal. If the waveform shown in a is input,
Due to the time constants of the wave detector 4 and the DC amplifier 5, the control voltage of the electronic attenuator 1 has a waveform with a sharp peak at the rising edge, as shown in b. For this reason, the output signal also becomes a signal in which the transient characteristics of the output power fluctuate greatly during the rising portion, as shown in C.

Is it possible to reduce the fluctuation in output power during this rising portion by lengthening the time constants of the detector 4 and DC amplifier 5? In this case, since the output voltage changes slowly during the rising portion, the specified output power The drawback is that it takes a long time to reach this point, so it cannot be used as a power amplifier for burst signals.

(Object of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a transmission power amplification circuit for burst signals with small output power fluctuations even for burst signals.

(Structure and operation of the invention) The present invention provides a sample-and-hold circuit between the DC amplifier 5 and the variable attenuator 1 of the conventional circuit to suppress the transient characteristics of the rising portion of the control voltage and reduce the output fluctuation with respect to the burst signal. This is what I did.

FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG.
The figure is a waveform diagram of each part. In FIG. 3, an electronic attenuator 1 whose attenuation varies depending on the control voltage, a high frequency power amplifier 2. Directional coupler 3. Detector 4. The DC amplifier 5 is the same as the conventional circuit, and 6 is a sample-and-hold circuit.

In FIG. 4, a shows the input signal, e shows the output waveform of the DC amplifier 5, f shows the sampling pulse, g shows the output waveform of the sample-and-hold circuit 6, and h shows the output signal.

The sample-and-hold circuit 6 outputs the input as it is when the sampling pulse f is H, and holds and outputs the voltage just before it becomes L during the L period (i in FIG. 4).

When the input signal shown in FIG. 4a is input, the DC amplifier 5
The output waveform of is a waveform with voltage fluctuations as shown in e. Since this signal is held by the sampling pulse f in the sample-and-hold circuit 6, the control voltage of the electronic attenuator 1 becomes a substantially constant voltage as shown by g.

In this way, even for inputs with large voltage fluctuations such as burst signals, the control voltage immediately before the intermittent part is held, so the voltage change that is controlled to follow the new output voltage becomes smaller and the rise Transient phenomena are suppressed, and an output signal with small output voltage fluctuations can be obtained as shown in h.

The electronic attenuator l can be easily realized using a diode or the like. Further, this may be replaced with a variable gain amplifier circuit.

In this way, according to the present invention, it is possible to realize a transmission power increasing circuit with little power fluctuation even for burst input signals.

(Effects of the Invention) By implementing the present invention, it is possible to realize a transmission power control circuit with little power fluctuation for burst signals where the transmission output is intermittent. This method has a remarkable effect as a transmission power amplification circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional transmission power amplification circuit, FIG. 2 is a waveform diagram of each part of FIG. 1, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. It is a waveform diagram of each part. 1... Variable attenuator, 2... High frequency power amplifier, 3
...Directional coupler, 4. Detector, 5. DC amplifier, 6. Sample and hold circuit. Fig. 2 Fig. 3 Fig. 4 Fig. 4■

Claims (1)

[Claims] A burst high-frequency signal is input to a variable attenuator and a transmission power amplifier that are connected in series, and a detection signal corresponding to the transmission output sent out from the transmission power amplifier is detected and sent to a DC amplifier. A transmission power amplifier circuit that controls the variable attenuator so as to be amplified and compared with a predetermined voltage, and when different from the predetermined voltage, to apply a control voltage to the variable attenuator to suppress fluctuations in the transmission output, It is connected between the DC amplifier and the variable attenuator to output the inputted control voltage as is when there is a sampling pulse in order to reduce the rising transient phenomenon of the burst-like high frequency signal. A transmission power amplification circuit comprising a sample-and-hold circuit that outputs the input control voltage as a control voltage held at the previous value when the control voltage is not present.