JPH0234546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a burst control circuit for a time division multiple access communication system. In particular, the present invention relates to a burst control circuit with good carrier wave suppression characteristics during burst pause periods.

[Description of prior art]

When switching a burst signal with a constant envelope using a burst control signal, the frequency range is instantaneously spread by turning the carrier wave on and off, causing interference with other stations' frequency bands and the own station's receiver. A disturbance occurs. In order to prevent this, a circuit is known that controls the rise and fall of the burst signal so that they do not change suddenly. For example PSK
Like the envelope of the (Phase Shift Keying) method,
A burst control circuit that smoothly controls the rise and fall characteristics in a burst signal section is generally used.

FIG. 1 is a conventional circuit configuration diagram for this purpose.
A high frequency input signal applied to the input terminal 1 is supplied to the power amplifier circuit 3 via the gain control circuit 2,
The power is amplified and sent to the output terminal 4. At this time, this output is detected by a detection circuit 5, and compared with a reference waveform generated by a reference waveform generation circuit 7 in response to a control signal applied to a terminal 6 by a comparison circuit 8 to obtain an error signal. This error signal controls the amplification gain of the gain control circuit.

In this circuit, for a control signal as shown in FIG. 2a, the output signal waveform is as shown in FIG. 2b. In other words, the amplitude of the output signal is controlled by the loop gain, so its rise and fall are gentle, but
There is carrier wave leakage in the burst pause period. This leakage amount is approximately -45 dB in time division multiple access communication system.
Although it is necessary to do the following, the amount of leakage is determined by the amount of carrier wave suppression in the gain control circuit 2.

For this reason, a circuit is known in which a switching circuit in which a large number of PI diodes are connected in series is connected in cascade to the gain control circuit 2 in order to obtain a large suppression effect, but this switching circuit itself has losses and becomes inefficient. There are drawbacks.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks, has no carrier wave leakage in the burst pause period, and uses a C class amplifier as the amplifier of the gain control circuit.
It is an object of the present invention to provide a burst control circuit that can increase efficiency and does not require the use of a lossy switching circuit in a high frequency range.

[Features of the invention]

The present invention provides a modulation circuit that inputs an intermediate frequency carrier signal and a modulation signal to obtain a modulated output, a frequency conversion circuit that converts the output frequency of this modulation circuit to a transmission frequency, and an output signal of this frequency conversion circuit that converts the output frequency of the modulation circuit into a transmission frequency. A gain control circuit to pass through, a power amplifier circuit that amplifies the output of this gain control circuit, a detection circuit that branches the output signal of this amplifier circuit and detects its amplitude, and uses the output of this detection circuit as one input. and a comparison circuit whose other input is a control signal of the burst signal, and the output of the comparison circuit is configured to control the gain of the signal passing through the gain control circuit. A switch circuit controlled by the control signal is provided in the path of the intermediate frequency signal, and the circuit is simple and inexpensive, has low power consumption, and is capable of suppressing the carrier wave in the burst pause period.

[Explanation based on examples]

Embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram of a burst control circuit according to an embodiment of the present invention. In FIG. 3, the same parts as in FIG. 1 are designated by the same reference numerals. An input terminal 1 into which a high frequency signal is input is connected to a gain control circuit 2,
A gain-controlled signal from the gain control circuit 2 is connected to the power amplifier circuit 3. A burst signal d amplified to a required transmission power from the power amplification circuit 3 is connected to an output terminal 4, and is branched and connected to a detection circuit 5. The detection circuit 5 is a circuit that detects the amplitude of a signal. A control signal terminal 6 to which the burst control signal a is input is connected to a reference waveform generation circuit 7.
A reference waveform signal serving as a reference for the envelope from the reference waveform generation circuit 7 and an envelope detection signal from the detection circuit 5 are connected to the comparison circuit 8 . An error signal from the comparison circuit 8 is connected to the gain control circuit 2.

Here, the feature of the present invention lies in the modulation portion surrounded by a dashed line. That is, the burst control signal a is branched from the control signal terminal 6 and connected to the modulation circuit 9, and the modulation output signal is switched. The modulation circuit 9 is a circuit that performs modulation using an intermediate frequency carrier input applied to an input terminal 11 and a modulation signal input applied to an input terminal 12, and its modulated output signal is converted to a transmission carrier frequency by a frequency conversion circuit 10. Its output is connected to input terminal 1. That is, in the circuit of the present invention,
Switching is also used at the intermediate frequency stage before frequency conversion, making it extremely efficient. In this example, a diode switch circuit is provided in the carrier wave signal path of the modulation circuit 9, and is configured to be opened and closed by a control signal.

FIG. 4 is an operational waveform diagram of this embodiment circuit.
Since the operation of the modulation circuit 9 is controlled according to the control signal a at the terminal 6, the input carrier wave C at the input terminal 1 becomes an intermittent wave as shown in FIG. 4c. Loop gain control is used to smooth the rise and fall to prevent frequency spread.

Generally, the lower the operating frequency of a switching circuit, the smaller the leakage when it is not conducting, and the smaller the loss when it is conducting. In other words, if a diode switch circuit is configured for the output frequency of the time division multiple access communication system as in the conventional example, there will be signal leakage due to capacitance between electrodes even when non-conducting, so many diodes must be connected in series. It won't happen. However, in order to perform switching at a low signal frequency stage before frequency conversion, as in this embodiment, even if diodes with the same interelectrode capacitance are used, the leakage during non-conduction is sufficiently reduced. be able to. Therefore, the number of diodes to be connected may be small (one in this example), and the loss during conduction can be reduced. Since the diodes used can be inexpensive for low frequencies, the cost of the switching circuit is significantly reduced.

Although the above example shows an example in which an intermediate frequency signal is switched in a modulation circuit, the present invention can also be applied to switching an intermediate frequency signal at a stage before the input of the modulation circuit or at a stage after the output of the modulation circuit. can be carried out.

〔Effect of the invention〕

As explained above, the present invention is provided with a modulation circuit that performs switching in the intermediate frequency band using a burst control signal, thereby making the circuit simple and inexpensive, reducing power consumption, and suppressing the carrier wave in the burst pause period. It has excellent effects.
Further, since the power amplifier circuit does not require a particularly large suppression characteristic, the use of a C class amplifier reduces the constant loss of the power amplifier, which is easy to design, and has the advantage of increasing the efficiency of power usage.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional burst control circuit. Figure 2 is a diagram of the electrical signal waveform. FIG. 3 is a block diagram of a burst control circuit according to an embodiment of the present invention. FIG. 4 is a diagram of the electrical signal waveform. 1, 11, 12...Input terminal, 2...Gain control circuit, 3...Power amplifier circuit, 4...Output terminal, 5
...Detection circuit, 6...Control signal terminal, 7...Reference waveform generation circuit, 8...Comparison circuit, 9...Modulation circuit, 10...Frequency conversion circuit, a...Burst control signal, b, d... ...Burst signal, C...Output signal.

Claims (1)

[Claims] 1. A modulation circuit that inputs an intermediate frequency carrier signal and a modulation signal to obtain a modulated output; a frequency conversion circuit that converts the output frequency of this modulation circuit to a transmission frequency; A gain control circuit through which the output signal passes; a power amplifier circuit that amplifies the output of this gain control circuit; a detection circuit that branches the output signal of this amplifier circuit and detects its amplitude; a comparison circuit having one input as an input and a control signal of the burst signal as the other input, and configured such that the passing signal gain of the gain control circuit is controlled by the output of the comparison circuit, A burst control circuit characterized in that a switch circuit controlled by the control signal is provided in a path of an intermediate frequency signal passing through a modulation circuit.