JPS60183855A - Orthogonal modulating device of digital processing type - Google Patents

Abstract

PURPOSE:To simplify the constitution and make a device inexpensive by connecting successively the first and the second filters which are connected to a base band signal and are operated with sampling phases different from each other, a circuit which scans outputs of these filters in time division and switches them, a D/A converter, and a BPF. CONSTITUTION:Digital LPFs 5-1 and 5-2 sample input signals (a) and (b) by sampling pulses (c) and (d) different in phase from each other to send out outputs (e) and (f). A switching circuit 6 switches and scans these outputs (e) and (f) in time division to generate an output (g). The output (g) is subjected to D/A conversion and is modulated orthogonally by a BPF8. In this case, a period T of pulses (c) and (d) is set to the reciprocal of a carrier frequency fc, and they have a phase difference T/4. Consequently, the switching circuit 6 outputs the output (e) for a time reference E and outputs the output (f) for a period F and outputs the output of a no-signal level for periods G AND H.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an improvement in a digitally processed quadrature modulation device.

(Prior art) Conventionally, a digital processing type quadrature modulation device that band-limits two different types of baseband signals using digital low-pass filters, amplitude-modulates them using mutually orthogonal carrier waves, and adds them is shown in Fig. 1. The configuration was as shown.

FIG. 1 is a block diagram showing an example of the configuration of this type of device that has been well known in the past, including a digital rono, a Sfilk 1-1, 1-2, a power N circuit 2-+, ? -2, an adder circuit 3, and a sine wave oscillator 4 that generates two orthogonal outputs, in other words mutually orthogonal carrier waves, and outputs them to the multiplier circuits 2-1 and 2-2.

However, the conventional configuration as shown in FIG. 1 requires a large amount of circuitry including a multiplier circuit, an adder circuit, and a sine wave oscillator. There was a problem.

(Objective of the Invention) The present invention has been made in consideration of the above points, and is constructed without using conventional multiplier circuits, adder circuits, sine wave oscillators, etc., and is inexpensive and miniaturized. An object of the present invention is to provide a digitally processed quadrature modulation device.

(Structure of the Invention) In other words, the present invention provides a device of this type that includes first and second filters that are connected to a baseband signal and operate at different sandal phases, and that outputs of the two filters are transmitted in a time-sharing manner. A scanning and switching circuit, a digital/analog converter, and a pantograph 9 motherboard are connected in sequence, and this configuration achieves the above object. The present invention will be explained below using the drawings.

(Embodiment of the Invention) FIG. 2 is a block diagram showing an embodiment of the differential processing type quadrature modulation device according to the present invention, in which the digital low/4' filters 5-1, 5-2 are each , receives input signals (a) and (b), samples them by driving sandals (C) and (d) with different phases, and sends out outputs (e) and (f). When the switching circuit 6 that performs switching scanning in a divided manner receives the outputs (e) and (f), it creates and sends out an output (g) according to the switching scanning.This output (g) is a digital analog converter 7
The digital signal is converted to an analog signal and sends an output (h), which is then converted into an analog band signal.
The output (i) signal is orthogonally modulated by the filter 8 and sent out as an output (i) signal.

FIG. 3 is a time chart illustrating the operation of the digitally processed orthogonal modulator described above, and (S) in the figure is a time reference for the purpose of explanation. Also, digital low/4'
Sample pulses (C), (d
) is chosen as the reciprocal of the carrier frequency fc, and T=1
/7c. This sample pulse (c),
(d) has a phase difference of T/4 here, so in the switching circuit 6, the output (e) is output when the time base is (a), and the output (f) is output when the time base is (b). ), when the time reference is met, and (d), the output (g), which outputs a no-signal level output, is obtained, in other words, the output (h) is obtained.

FIG. 4 is an explanatory diagram of the operation of the digital processing type quadrature modulation device having the above configuration using a frequency overlap tram. In the figure (
e) and (f) indicate the frequency overlapping trams of the digital rono and filter output, respectively, and (e)'' and (f)
' is a vector indicating the phase of the carrier wave. Also, (i)'
shows the transmission characteristics of an analog pandonoss filter, and (
j) The spectral diagram of the i-sentence modulated signal by the U analog punt pass filter is shown.

Here, as shown in FIG. 4, the present invention provides two orthogonal
Samples with different phases to obtain two carrier waves/4
'Rus is clearly used, and will be explained below.

The signals (e) and (f) are expressed by the following equations (1) and (
It can be shown in two ways.

=(a■p)・(1+cmωct+cos2ωct
−1−=== )・・・・・・(1) ・・・・・・(2) The above is clear if you pay attention to the second term in parentheses in equations (1) and (2). In this way, the two carrier waves are orthogonal. FIG. 4 shows this diagrammatically.

Incidentally, in the above equation, ■ simply represents the convolution integral, and p is the impulse response of the digital low-pass filter.

(Effects of the Invention) As detailed above, according to the present invention, in this type of device, two types of different sample phases are prepared, a digital low-pass filter is driven, and the output is obtained by switching. Therefore, there is no need for conventional multiplier circuits, adder circuits, and sine wave oscillators.Therefore, we have created a digitally processed quadrature modulation device that is inexpensive and can be miniaturized, and does not impair the required characteristics. You can expect the excellent effects it can provide.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing an example of the configuration of a conventional digital processing quadrature modulation device, and FIG. 2 is a block diagram showing an embodiment of a digital processing quadrature modulation device according to the present invention. , 3rd
The figure is a time chart explaining the operation of the device shown in FIG. 2, and FIG. 4 is an explanatory diagram using a cover tram. 7-1.1-2.5-1.5-2 is Dino Tarro ie
3 is an adder circuit, 4 is a sine wave oscillator, 6 is a switching circuit, 7 is a digital-to-analog converter, and 8 is a bandpass filter. Patent applicant: Oki Electric Industry Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] A digital processing quadrature modulation device that amplitude-modulates a baseband signal using mutually orthogonal carrier waves and adds the amplitude modulation device, comprising: a first and a second baseband signal connected to the baseband signal and operating at different sample phases; The present invention is characterized in that it is configured by sequentially connecting a digital low-speed filter, a circuit that time-divisionally scans and switches the outputs of both filters, a digital-to-analog converter, and a band-to-low speed filter. Deinotal processing type quadrature modulation device.