JPH01208943A - Receiver - Google Patents

Abstract

PURPOSE:To obtain a synchronizing detection recovered carrier while making a local oscillation frequency stable with a simple circuit constitution by adopting the constitution of PLL such that a phase difference between a received intermediate frequency signal and a signal from a reference oscillator is detected and its error voltage is fed back to a VCO(voltage controlled oscillator) being a local oscillation frequency source. CONSTITUTION:In the case of the reception of a modulation wave FR to a reception input 11, a mixer 12 mixes it with a local oscillation signal (FL+ or -FR) from a VCO 17 to obtain an intermediate frequency signal (¦FR-FL+ or -DELTAFL¦). The intermediate frequency signal is given to a synchronizing detector 13 and the phase is compared with a signal (FIF+ or -DELTAFIF) from a reference oscillator 15 at a PD(phase comparator) 14 to produce a phase error voltage. The phase error voltage is subjected to the elimination of noise and modulation component by an LPF 16 and the result is fed to the frequency control terminal of the VCO 17, then the PLL circuit is constituted to control te VCO 17 so as to obtain the relation of ¦FL+ or -DELTAFL¦=FIF+ or -DELTAFIF. Thus, the reference oscillation signal is equivalent to a reception carrier and fed to the synchronizing detector 13 and used as the synchronizing detection recovered carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a receiving device used in digital wireless communications and the like.

Conventional technology Conventionally, in this type of receiving device, a synchronous detection car has been used in the detection circuit, and the typical technologies for regenerating the carrier wave required for synchronous detection are (1) multiplier, (2) reverse A modulation method, (3) Costas method, etc. are known.

Here, as a typical example of a conventional 4PS system using a multiplier,
The K receiving device will be described.

FIG. 2 shows the configuration of a 4PSK receiving apparatus using a conventional multiplier. In FIG. 2, reference numeral 21 is a reception input terminal connected to a mixer 22.

The output of local oscillator 23 is connected to mixer 22 .

The output of the mixer 22 is a quadruple multiplier 24 and a synchronous detection circuit 2.
5. The output of the quadruple multiplier 24 is connected to a bandpass filter 26, and the output of the bandpass filter 26 is connected to a phase comparator (called PhascDetector).
It is connected to 27. On the other hand, 28 is a voltage controlled oscillator (μ
Lower V CO: Voltage Control 1
edOscillator), and its output is connected to a synchronous detection circuit 25 and a quadrupler 29.

Also, 30 is a low frequency door filter (hereinafter referred to as LPF: Low Pa
5s Filter) and is connected to the output terminal of PD27 and the frequency control terminal of VC028. Next, the operation of the above conventional example will be explained. In FIG. 2, when a 4PSK signal is received, it is mixed with a signal from a local oscillator 23 in a mixer 22, and an intermediate frequency signal F
get. In the case of a JPSK wave, 0 expressed as Fif, when this Fif is multiplied by 4 in the 4 multiplier 24, F=c
os(4ωcj+(2+1)π)=cos 4ωct
get. The carrier wave cos from which modulation components are removed by passing this signal through a bandpass filter 26 centered at 4ωC
4ωc1 is obtained. Phase comparator (PD) 2
7, a phase-locked circuit (μ
Lower PLL: A reference carrier wave with excellent four characteristics can be obtained from VC028 using Phase Locked Loop, and can be used as a reference carrier wave for synchronous detection.

By using a multiplier in such a conventional receiving device, a reference carrier wave for coherent detection can be obtained.

Problems to be Solved by the Invention However, the above-mentioned conventional receiving device requires a multiplier circuit, which results in a complex and large circuit and high power consumption.

2. The influence of the oscillation frequency deviation of the local oscillation circuit is large. For example, if the frequency deviation of a local oscillation circuit is ±1 at 900 MHz,
If it is 0 ppm, it will cause a frequency deviation of +9 kHz,
There was a problem in that reception performance deteriorated because synchronous detection was performed at an intermediate frequency shifted by +9 kHz.

The present invention solves the above conventional problems, and provides an excellent receiving device that has a simple circuit configuration and can obtain a regenerated carrier wave for synchronous detection while stabilizing the local oscillation frequency. The purpose is to

Means for Solving the Problems In order to achieve the above objects, the present invention provides a reference oscillator that has vCO as a local oscillation frequency source and has an oscillation frequency approximately equal to a nominal intermediate frequency, a reference oscillator output signal, and a receiver. A phase comparator (
PD) and an LPF that removes noise and modulation components,
CO1 reference oscillator.

PD, LPF (Phase Locke)
d Loop) circuit.

Effects The present invention has the following effects due to the above configuration. That is, when a modulated wave is received (here, it is assumed that the reception frequency FR is accurate), it is mixed with vCO to obtain an intermediate frequency signal. The intermediate frequency signal is phase-compared with a reference oscillator output signal at the PD to generate a phase error voltage.

The phase error voltage is applied to the frequency control terminal of the VCO after noise and modulation components are removed by the LPF. By configuring the PLL circuit in this manner and appropriately selecting the constant of the LPF, the phases and frequencies of the received intermediate frequency signal and the reference oscillator match, and the reference oscillator output signal becomes equivalent to the received carrier wave.

2. Set the reception frequency to FR1, set the local oscillation frequency (VCO frequency) to FL±ΔFL, and set the reference oscillator frequency to FIF ΔFI.
When F, the reception intermediate frequency becomes IFR-FL±ΔFL1. Since this becomes equal to the reference oscillation frequency by the PI and L circuits, 1F'R, PL ± ΔFt, 1 = Ftp ± ΔFIF, and l FR - FL I = FIF, so ΔFL
=ΔFIF.

Here, for example, Ft = 900MHz, PIF =
45 MHz, △F IF "450Hz (when the frequency deviation of the reference oscillator is ±10 ppm), ΔF
L = 450 Hz, and the local oscillation frequency stability is isometrically △Ft, /Ft, = 0.5 ppm, ±
Using a reference oscillator with a frequency stability of 1 oppm, a receive frequency stability of ±0.5 ppm can be obtained isometrically.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 11 is a reception input terminal, which is connected to a mixer 12. The output of the mixer 12 is connected to a synchronous detector 13 and a PD 14. 15 is a reference oscillator;
Its output is connected to the other terminals of the synchronous detector 13 and PD 14.

The output of the PD 14 is input to the LPF 16, and the output of the LPF 16 is connected to the frequency control terminal of the VCO 17.

18 is a demodulation output terminal.

Next, the operation of the above embodiment will be explained. In the above embodiment, when the receiver 11 receives the modulated wave FR, the mixer 12 outputs the local oscillation signal (Ft, ±ΔFt) from the VCO 17.
, ) and mixed with the intermediate frequency signal (IFR~FL±ΔFt
l) is obtained.

This intermediate frequency signal is input to the synchronous detector 13, and the signal from the reference oscillator 15 (F
Ip±ΔFIF) and the phase is compared to produce a phase error voltage. This phase error voltage is applied to the frequency control terminal of the VCO 17 after noise and modulation components are removed by the LPF 16, forming a PLL circuit, IFR~FL±ΔFL1=FI
vCO17 is controlled so that F±ΔFIF. Therefore, the reference oscillation signal becomes equivalent to the received carrier wave, is added to the synchronous detector 13, and is used as a recovered carrier wave for synchronous detection. Also, l FR−Ft, i:FLl = PIF±Δ
It becomes FIF and stabilizes the local oscillation frequency.

Effects of the Invention As is clear from the above embodiments, the present invention has the effects shown below.

The phase difference between the received intermediate frequency signal and the reference oscillator is detected, and the error voltage is fed back to vCO, which is the local oscillation frequency source, and P
Because it constitutes LL.

(1) A regenerated carrier wave for synchronous detection can be obtained with a simpler circuit configuration than the conventional one.

(2) It is possible to obtain an isometric and highly stable local oscillation frequency.

[Brief explanation of the drawing]

FIG. 1 shows a receiving device 11 in an embodiment of the present invention.
・Reception input terminal, 12...Mixer, 13...Synchronized detection circuit, 14...PD, 15...Reference oscillator,
16... LPF, 17... VCo, 18... Demodulation output, 21... Input terminal, 22... Mixer, 23...
...Local oscillator, 24... Multiplier circuit, 25... Synchronous detection circuit, 26... Bandpass filter, 27...
P D, 28, , VCo, 29 ・4T multiplier circuit, 30, , LPF. Name of agent: Patent attorney Toshio Nakao and one other person
+ ≧ 1v

Claims (1)

[Claims] a voltage controlled oscillator whose oscillation frequency is controlled by an external control voltage; a mixer that uses the output of the voltage controlled oscillator as a local oscillation signal source for a receiver and converts the receiving signal into an intermediate frequency signal; a reference oscillator that generates a frequency approximately equal to the nominal intermediate frequency of the machine, and detecting a phase difference between the intermediate frequency signal and the output of the reference oscillator;
A phase comparator that converts this phase difference into a voltage, and a low-pass filter that removes noise and modulation components from the output of the phase comparator are provided, and the output of the low-pass filter is set to the frequency of the voltage controlled oscillator. A receiving device comprising a synchronous detector that feeds back the intermediate frequency signal to a control terminal and synchronously detects the intermediate frequency signal using the output of the reference oscillator as a reference carrier wave.