RU2414042C2 - Method and device for filter-free frequency conversion - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: by means of 4 similar balance (double balance) mixers there formed in parallel are 4 products of quadratures of input and heterodyne signals: (cos_inp·cos_het); (sin_inp·sin_het); (sin_inp·cos_het); (cos_inp·sin_het). Both input signal and heterodyne signal is pre-split into quadrature components - cosine (advanced) and sine (retarded); each component of input signal is multiplied by each component of heterodyne and in compliance with trigonometry formulae for cosine and sine of sum and difference of two angles thee formed are cosine and sine quadrature signal components of intermediate frequency. Essence of the device consists in the fact that phase splitters of input signal and heterodyne signal into quadrature projections, cosine and sine ones, are introduced to it; four multipliers - balance mixers are used as mixer, which are loaded onto the first (R_H1) and the second (R_H2) load resistors and connections between them.

EFFECT: improving interference immunity and simplifying frequency division of GLONASS signals.

2 cl, 3 dwg

Description

The invention relates to the field of radio engineering.

All analog signal processing paths typically require frequency conversion.

The classic block diagram of a frequency converter is shown in figure 1 and described in (1).

Figure 1 is a classic block diagram of a frequency converter

The list of symbols in figure 1:

SM - mixer;

Get - heterodyne;

FPF - intermediate frequency filter.

The mixer SM must perform the operation of multiplying the input signal of frequency f _c with the signal of the local oscillator frequency f _g It is known that the product of two harmonic signals is equal to the half-sum of signals with difference (f _c - f _g ) - down conversion and the total frequency (f _c + f _g ) - up conversion.

It is also known that the closer the operation performed by the mixer to the product of two harmonic signals, the fewer conversion by-products at the mixer output. Currently, the so-called balanced mixer is widely used, the circuit of which is shown in figure 2 (2).

Figure 2 is a typical diagram of a balance mixer.

The current increments at Output 1 and Output 2 of the balanced mixer are proportional to the product of the signals supplied to Input 1 and Input 2, but have opposite signs. We call Vykh.1 - direct, and Vykh.2 - inverse. Even more strictly, the operation of multiplying the input signals is performed by a double balanced mixer, in which the penetration of the multiplied signals to the outputs is schematically compensated.

The need for the application of the PLL is the main disadvantage of the frequency converter circuit (Fig. 1). Typically, PLLs are multi-link (LC circuits, volume resonators, long line segments, SAW filters, etc.). This limits the possibilities for microminiaturization of electronic equipment. Currently known transistor filter circuits (the so-called gyrators), which allows you to embed them in the chip chip. However, the stability of their parameters (as filters) is low, the frequency especially depends on the temperature of the crystal. The devices for adjusting the parameters of the gyrator are quite complex and in the general case may require the use of additional hinged elements.

The main objective of the proposed method and device filterless frequency conversion is to eliminate these disadvantages of the prototype.

This problem is solved in that in the method of filterless frequency conversion, including the operation of multiplying the input signal with the local oscillator signal and isolating the desired conversion product into an intermediate frequency signal with the frequency difference of the input signal and the local oscillator, or with their sum, several operations are additionally introduced, namely, pre-split into quadrature projections and the input signal and the local oscillator signal - cosine (leading) and sine (lagging), each component of the input signal is multiplied with azhdoy component and LO according to trigonometry formulas for the cosine and sine of the sum and difference of two angles formed cosine and sine quadrature projections of the intermediate frequency signal.

This problem is also solved by the fact that in the device that implements the method and includes a mixer and a local oscillator, phase splitters of the input real signal and the local oscillator signal into quadrature components, cosine and sine, are added as a mixer, four identical multipliers are used - balanced mixers, loaded on the first and second resistors (R _H1 first and second R _H2), wherein the first output (cosine) fazorasschepitelya input connected to the first inputs of the first and second multiply spruce - balanced mixers, the second output (sinus) of this phase splitter is connected to the first inputs of the third and fourth multipliers - balanced mixers, the first output of the heterodyne phase splitter (cosine) is connected to the second inputs of the first and third multipliers - balanced mixers, the second output of this phase splitter is with the second the inputs of the second and fourth multipliers - balanced mixers; to convert the frequency down, the first load resistor (R _Н1 ) is connected to the first outputs of the first and fourth multipliers - balanced mixers, the second load resistor (R _Н2 ) with the first output of the third multiplier-balanced mixer and the second output of the second multiplier-balanced mixer, for frequency conversion up the first load resistor (R _H1) connected to the first output of the first multiplier-balanced mixer, a second load resistor (R _N2) to a first output of the third and the first output of the second re nozhiteley - balanced mixers.

This is achieved by somewhat complicating the transistor part of the converter using the quadrature components of both the input signal (and output) and the local oscillator. The complication associated with the use of quadratures of both the input signals and the output signal of the converter is not a drawback, since a single splitting of the input signals into quadrature projections expands the functionality of further processing of radio signals. At low input signal frequencies (up to hundreds of MHz), the input real signal is split into quadratures using the well-known RC bridge, where the phase difference at its outputs is maintained (≈90 °) in a fairly wide frequency band of the input modulated signal (up to 20%). At higher frequencies (GHz), the well-known waveguide microstrip ring phase splitting bridge made on a foil dielectric is also used for the same purposes. Additionally, such a bridge performs the function of an input signal preselector filter.

To split the unmodulated local oscillator signal into quadratures, you can use the well-known phase-shifting RLC, a chain (± 90 °) or form quadratures during digital synthesis of the local oscillator frequency.

In any case, the phase splitters of the actual signal into quadrature components have one input and two outputs. For definiteness, we will call their outputs: leading (cosine) Out 1, delayed (sinus) Out 2.

The essence of the proposed method is that using four identical balanced mixers (double balanced) in parallel form 4 products of the quadratures of the input and heterodyne signals:

(cos _in · cos _get ); (sin _bx sin _get ); (sin _bx sin _get ); (cos _in · sin _get ).

Here, the leading quadrature components of the input signal and the local oscillator are arbitrarily designated through cos _in and cos _get , lagging through sin _in and sin _get, respectively.

Further, in strict accordance with the trigonometry formulas, the algebraic sums of these products are formed:

Here, also to shorten the notation is indicated:

cos _Δ is the leading (cosine) component of the intermediate frequency signal equal to f _c -f _g ;

- опережающая (косинусная) составляющая сигнала промежуточной частоты, равной f_c+f_г;cos

- leading (cosine) component of the intermediate frequency signal equal to f _c + f _g ;

sin _Δ - delayed (sine) component of the intermediate frequency signal equal to f _c -f _g ;

- запаздывающая (синусная) составляющая сигнала промежуточной частоты, равной f_c+f_г.sin

- delayed (sine) component of the intermediate frequency signal equal to f _c + f _g .

A device that implements this method consists of a local oscillator, two phase splitters (input and heterodyne signals), four balanced-multiplier (double balanced) mixers, and two load resistors. Its block diagram is shown in FIG. 3.

Figure 3 - block diagram of the device.

The method and apparatus of a filterless frequency conversion contains the following blocks:

1-4 - multipliers - balanced (double balanced) mixers;

5 - phase splitter of the input signal;

6 - phase splitter of the local oscillator signal;

7 - local oscillator;

8, 9 (R _H1 , R _H2 ) - load resistors.

The device operates as follows. The connection of the quadratures of the input signal (output 1 and 2 of block 5) and the local oscillator (outputs 1 and 2 of block 6) shown in Fig. 3 provide the formation of the following works in the same multipliers - balanced mixers, as shown in the table.

Block 1 Out 1

Out 2

Block 2 Out 1

Out 2

Block 3 Out 1

Out 2

Block 4 Out 1

Out 2

For the selected frequency conversion option (up or down), the necessary algebraic sums of products in accordance with formulas (1) and the table are formed on common load resistors 1 and 2 (R _Н1 and R _Н2 ). An advanced quadrature projection (cosine) of the intermediate frequency signal is formed on R _Н1 , and a delayed (sinus) projection on R _Н2 .

The load resistors shown in figure 3, provide the formation of an intermediate frequency signal on R _H1 equal to cos2 _tg (f _c -f _g ) t, on R _H2 equal to sin2 _tg (f _c -f _g ) t. Load resistors R _H1 connected to the outputs. 1 multiplier - balanced mixer 1 and Out. 2 multipliers - balanced mixer 4, a R _H2 to Out. 1 multiplier - balanced mixer 3 and Out. 1 multiplier - balanced mixer 2, form a signal of the total intermediate frequency (f _c + f _g ). Free inputs of the multipliers - balanced mixers are connected to the power bus U _n .

These method and apparatus for filterless frequency conversion can be implemented in receivers and combined receivers of satellite navigation using direct conversion, and also simplify the frequency separation of GLONASS signals.

Information sources

1. Design of radio receivers. / Edited by A.P. Sivers. Moscow, Soviet Radio, 1976

2. Radio receivers. 3rd ed., Authors: Fomin N.N., Buga N.N. Publishing Hotline - Telecom, 2007

Claims (2)

1. A method of filterless frequency conversion, including the operations of multiplying the input signal and the local oscillator signal and isolating the desired conversion product into an intermediate frequency signal with the frequency difference of the input signal and the local oscillator or with their sum, characterized in that both the input signal and the local oscillator signal are preliminarily split into quadrature components, cosine and sine, each component of the input signal is multiplied with each component of the local oscillator, the product of the cosine quadrature composition is summed input signal and the local oscillator with the product of their sine components and get the cosine quadrature component of the intermediate frequency equal to the frequency difference of the input signal and the local oscillator, summarize the product of the cosine components of the input signal with the inverted product of their sine components and get the cosine quadrature component of the intermediate frequency signal equal to the sum of the frequencies of the input signal and the local oscillator, summarize the product of the cosine component of the input signal with sine of the local oscillator and the product of the sine component of the input signal with the cosine component of the local oscillator and get the sine quadrature component of the intermediate frequency signal equal to the sum of the frequencies of the input signal and the local oscillator, summarize the product of the cosine component of the input signal with the sine component of the local oscillator and the inverse product of the sine component of the input signal from the cosine component of the input signal from the cosine component and get the sine quadrature component of the intermediate frequency signal equal to the frequency difference of the input signal and the local oscillator. 2. A device that implements the method according to claim 1, comprising a mixer and a local oscillator, characterized in that phase splitter of the input signal and the local oscillator signal into quadrature, cosine and sine projections are additionally introduced into it, four multiplier-balanced mixers are used as a mixer, which load to the first (R _n1 ) and second (R _n2 ) load resistors, the first output (cosine) of the input phase splitter connected to the first inputs of the first and second multiplier-balanced mixers, the second output (blue clear) of this input signal phase splitter is connected to the first inputs of the third and fourth balanced-mixer multipliers, the first output of the local oscillator phase splitter (cosine) is connected to the second inputs of the first and third balanced-multiplier mixers, and the second output of this heterodyne signal phase splitter is to the second inputs of the second and the fourth multiplier-balanced mixers; to convert the frequency down, the first load resistor (R _n1 ) is connected to the first outputs of the first and fourth multiplier-balanced mixers, the second load resistor (R _n2 ) with the first output of the third multiplier-balanced mixer and the second output of the second multiplier-balanced mixer, for frequency conversion up the first load resistor (K _n1 ) is connected to the first output of the first multiplier-balanced mixer, the second load resistor (R _n2 ) is the first output of the third and first second multipliers -balanced mixers.

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