Front end and high frequency receiver having quadrature low noise amplifier
View Patent ↗A front end and a high frequency receiver provided therewith are described, which front end comprises a quadrature low noise amplifier as a low noise amplifier. A high isolation between local oscillators and quadrature mixers is achieved thereby, reducing a DC offset at mixer outputs. The quadrature low noise amplifier may be implemented as a differential class AB cascode arrangement of MOST or FET semiconductors. A low distortion receiver having a high linearity is the result.
1. A high frequency receiver which is provided with a front end comprising:
a first quadrature low noise amplifier;
a second quadrature low noise amplifier;
first and second quadrature mixers coupled to respective ones of the first and second low noise amplifiers;
first and second quadrature choppers respectively coupled between respective outputs of the respective ones of the first and second quadrature low noise amplifiers, and respective inputs of respective ones of the first and second mixers, the outputs of the first and second mixers being demodulated by a quadrature demodulator, said choppers respectively switching in-phase and quadrature signals.
2. A high frequency receiver according to claim 1 , wherein quadrature paths of the first and second quadrature low noise amplifiers are implemented differentially.
3. The high frequency receiver according to claim 2 , wherein the differential first and second quadrature low amplifiers are constructed as a class AB operating circuits.
4. The high frequency receiver according to claim 2 , wherein each of said first and second quadrature low noise amplifiers comprises a cascode arrangement of semiconductors.
5. The high frequency receiver according to claim 4 , wherein each of said first and second semiconductors are of the type MOST.
6. A high frequency receiver according to claim 4 , wherein across the cascode arrangement of semiconductors there is connected a capacitor (C).
7. The receiver according to claim 6 , wherein said cascode arrangement comprises two parallel legs of said semiconductors, both legs being in parallel with said capacitor.
8. The receiver according to claim 6 , wherein said cascode arrangement comprises a differential cascode arrangement.
9. The high frequency receiver according to claim 1 , wherein the quadrature choppers and quadrature mixers are combined to passive quadrature choppers/mixers.
10. The receiver according to claim 1 , wherein the first and second quadrature mixers are in a receive circuit of said receiver.
11. The receiver according to claim 10 , wherein output of said first and second mixers comprises a signal that has been down-converted by said receive circuit.
12. The receiver according to claim 1 , wherein each of said choppers switches its respective outputs for coupling with the outputs of the other of said choppers.
13. A high frequency receiver which is provided with a front end comprising:
a first quadrature low noise amplifier;
a second quadrature low noise amplifier;
first and second quadrature mixers coupled to respective ones of the first and second low noise amplifiers;
first and second quadrature choppers respectively coupled between respective outputs of the respective ones of the first and second quadrature low noise amplifier, and respective inputs of respective ones of the first and second quadrature mixers, the outputs of the first and second mixers being demodulated by a quadrature demodulator, wherein each of said choppers switches its respective outputs for coupling with the outputs of the other of said choppers.