Circuit arrangement for a wideband mixer with predistortion and high linearity
View Patent ↗Circuit arrangement for a wideband mixer ( 1, 101, 201 ) with a multiplicative mixing stage ( 2 ) which exhibits a carrier frequency input ( 3, 4 ) for coupling in a differential carrier frequency signal (LOP, LON), a mixing stage input ( 5, 6 ) for coupling in a predistorted differential input signal (LFPD, LFND), and an output ( 9, 10 ) for coupling out a differential output signal (OUTP, OUTN) which is generated from the differential carrier frequency signal (LOP, LON) and the predistorted differential input signal (LFPD, LFND) by multiplicative mixing, the predistorted differential input signal (LFPD, LFND) being generated from a differential input signal (LFP, LFN) by means of a quadratic predistortion and a linear predistortion.
1. A circuit arrangement for a wideband mixer, comprising:
a multiplicative mixing stage having a carrier frequency input, a differential signal input, and a differential mixing state output;
a predistortion circuit coupled to the differential signal input, and further configured to receive at least a part of a differential input signal, the predistortion circuit configured to generate a differential output signal using quadratic predistortion and linear predistortion, the predistortion circuit operable to provide the differential output signal to the differential signal input of the multiplicative mixing stage.
2. The circuit arrangement as claimed in claim 1 , wherein the predistortion circuit further includes a first predistortion section having a first input terminal configured to receive a first component of the differential input signal and a second predistortion section having a second input terminal configured to receive a second component of the differential signal.
3. The circuit arrangement as claimed in claim 2 , wherein the first predistortion section includes a first resistor coupled between a first supply voltage potential and the first input terminal, and the second predistortion section includes a second resistor coupled between the second input terminal and the first supply voltage potential.
4. The circuit arrangement as claimed in claim 3 , wherein at least the first resistor comprises an adjustable resistor.
5. The circuit arrangement as claimed in claim 3 , wherein the first predistortion section further comprises a plurality of resistors including the first resistor, each of the plurality of resistors being switchably connected in parallel between the first supply voltage terminal and the first input terminal.
6. The circuit arrangement as claimed in claim 2 , wherein the predistortion circuit includes a first transistor having a controlled path connected between the first input terminal and a first supply voltage potential, and a second transistor having a controlled path connected between the second input terminal and the first supply voltage potential, and the first and second transistors having gate terminals connected to one another and connected to a distortion potential.
7. The circuit arrangement as claimed in claim 6 , wherein the distortion potential is the first supply voltage potential.
8. The circuit arrangement as claimed in claim 1 , wherein the predistortion circuit further includes at least one diode configured to generate the quadratic predistortion.
9. The circuit arrangement as claimed in claim 1 , wherein the wherein the multiplicative mixing stage comprises a Gilbert cell.
10. The circuit arrangement as claimed in claim 4 , further comprising a predistortion control circuit, the predistortion control circuit including:
a test signal output configured to provide a test signal to the first input terminal and the second input terminal;
a test signal input coupled to the differential mixing state output; and
at least one control output configured to provide adjustment control signals to the adjustable first resistor.
11. The circuit arrangement as claimed in claim 1 , wherein the circuit arrangement is constructed in MOS technology.
12. The circuit arrangement as claimed in claim 1 , wherein the linear predistortion is selected in such a manner that the spurious-interference-free dynamic range of an output signal of the multiplicative mixing stage is maximum for a differential input signal having a predetermined frequency.
13. The circuit arrangement as claimed in claim 1 , wherein the multiplicative mixing stage comprises a single-sideband mixing stage.
14. The circuit arrangement as claimed in claim 1 , wherein the linear predistortion is selected such that, over a predetermined range of carrier frequencies, the signal energy of an output signal is equal to the signal energy of a third harmonic of the differential input signal within the output signal at the frequency of the carrier frequency signal.
15. A method for mixing a carrier frequency signal and an input signal, comprising:
(a) effecting linear predistortion and quadratic predistortion of the input signal in order to generate a predistorted input signal; and
(b) mixing the predistorted input signal with the carrier frequency signal to form an output signal.
16. The method as claimed in claim 15 , wherein the linear component of the predistortion is selected in such a manner that the spurious-interference-free dynamic range of the output signal is maximum with an input signal which exhibits a predetermined frequency.
17. The method as claimed in claim 15 , wherein step a) further comprises effecting linear distortion at least in part using a resistive circuit having at least one resistor and a circuit resistance.
18. The method as claimed in claim 17 , wherein step a) further comprises effecting linear distortion using a resistive circuit having an adjustable circuit resistance.
19. A circuit arrangement for a wideband mixer, comprising:
a mixing stage having a carrier frequency input, a differential signal input, and a differential mixing state output;
a predistortion circuit coupled to the differential signal input, and further configured to receive at least a part of a differential input signal, the predistortion circuit configured to generate a differential output signal using quadratic predistortion and linear predistortion, the predistortion circuit including a resistive circuit having a resistance value to generate the linear predistortion, the predistortion circuit operable to provide the differential output signal to the differential signal input of the mixing stage.
20. The circuit arrangement according to claim 19 , wherein the predistortion circuit further comprises a nonlinear circuit configured to generate the quadratic predistortion, the nonlinear circuit comprising at least one of the group consisting of a transistor and a diode.