Low noise Gilbert Multiplier Cells and quadrature modulators

• US 5,847,623 A
• Filed: 09/08/1997
• Issued: 12/08/1998
• Est. Priority Date: 09/08/1997
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Hadjichristos, Aristotle
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US08/925,572
• Time in Patent Office: 456 Days
• Field of Search: 332/103, 332/105, 332/178, 332/159, 327/116, 327/119, 327/356, 327/357, 327/359, 455/333, 375/261, 375/298
• US Class Current: 332/105
• CPC Class Codes: H03C 1/02 Details
• CPC Class Codes: H03C 1/545 using bipolar transistors
• CPC Class Codes: H03C 2200/0012 Emitter or source coupled transistor pairs or long tail pairs
• CPC Class Codes: H03C 2200/002 Filters with particular characteristics
• CPC Class Codes: H03C 2200/0025 Gilbert multipliers
• CPC Class Codes: H03C 2200/0058 Quadrature arrangements
• CPC Class Codes: H03C 3/40 using two signal paths the outputs of which have a predetermined phase difference and at least one output being amplitude-modulated

Abstract

A Gilbert Multiplier Cell includes an emitter-coupled transistor pair and a pair of cross-coupled emitter-coupled transistor pairs. A filter couples the emitter-coupled transistor pair to the pair of the cross-coupled emitter-coupled transistor pairs. The filter may include a pair of inductors or resistors, a respective one of which serially couples a respective one of the emitter-coupled transistor pair to a respective one of the pair of cross-coupled emitter-coupled transistor pairs, and a capacitor connected between the pair of inductors or resistors. A local oscillator is coupled to the pair of cross-coupled emitter-coupled transistor pairs and a data input is coupled to the emitter-coupled transistor pair. By low pass filtering the output of the emitter-coupled transistor pair that is applied to the pair of cross-coupled emitter-coupled transistor pairs, low noise floor Gilbert Multiplier Cells and quadraphase modulators may be provided.

Claims

1. A Gilbert Multiplier Cell comprising:

an emitter-coupled transistor pair;

a pair of cross-coupled emitter-coupled transistor pairs; and

a filter that couples the emitter-coupled transistor pair to the pair of cross-coupled emitter-coupled transistor pairs.

2. Gilbert Multiplier Cell according to claim 1 wherein the filter comprises:

a pair of inductors or resistors, a respective one of which serially couples a respective one of the emitter-coupled transistor pair to a respective one of the pair of cross-coupled emitter-coupled transistor pairs; and

a capacitor connected between the pair of inductors or resistors.

3. A Gilbert Multiplier Cell according to claim 2 further comprising an integrated circuit substrate;

wherein the emitter-coupled transistor pair and the pair of cross-coupled emitter-coupled transistor pairs are included in the integrated circuit substrate;

wherein the pair of inductors or resistors are included in the integrated circuit substrate; and

wherein the capacitor is a discrete capacitor that is not included in the integrated circuit substrate.

4. A Gilbert Multiplier Cell according to claim 3 wherein the pair of inductors are a pair of integrated circuit spiral inductors.

5. A Gilbert Multiplier Cell according to claim 1 further comprising:

a local oscillator that is coupled to the pair of cross-coupled emitter-coupled transistor pairs; and

a data input that is coupled to the emitter-coupled transistor pair.

6. A Gilbert Multiplier Cell according to claim 1 wherein the filter is a low pass filter having a cutoff frequency that filters frequencies above the cutoff frequency.

7. A Gilbert Multiplier Cell according to claim 5 wherein the local oscillator oscillates at mobile radiotelephone frequencies and wherein the data input is a mobile radiotelephone data input.

8. A quadraphase modulator comprising:

a quadrature splitter; and

a pair of Gilbert Multiplier Cells coupled to the quadrature splitter, each of the Gilbert Multiplier Cells comprising;

an emitter-coupled transistor pair;

a pair of cross-coupled emitter-coupled transistor pairs; and

a filter that couples the emitter-coupled transistor pair to the pair of cross-coupled emitter-coupled transistor pairs.

9. A quadraphase modulator according to claim 8 wherein the filter comprises:

a pair of inductors or resistors, a respective one of which serially couples a respective one of the emitter-coupled transistor pair to a respective one of the pair of cross-coupled emitter-coupled transistor pairs; and

a capacitor connected between the pair of inductors or resistors.

10. A quadraphase modulator according to claim 9 further comprising an integrated circuit substrate;

wherein the emitter-coupled transistor pair and the pair of cross-coupled emitter-coupled transistor pairs of each of the Gilbert Multiplier Cells are included in the integrated circuit substrate;

wherein the pair of inductors or resistors of each of the Gilbert Multiplier Cells are included in the integrated circuit substrate; and

wherein the capacitor of each of the Gilbert Multiplier Cells is a discrete capacitor which is not included in the integrated circuit substrate.

11. A quadraphase modulator according to claim 10 wherein the pair of inductors of each of the Gilbert Multiplier Cells are a pair of integrated circuit spiral inductors.

12. A quadraphase modulator according to claim 8 further comprising:

a local oscillator that is coupled to the quadrature splitter;

the quadrature splitter generating a pair of phase shifted outputs, a respective one of which is coupled to the pair of cross-coupled emitter-coupled transistor pairs in a respective one of the pair of Gilbert Multiplier Cells; and

I and Q data inputs, a respective one of which is coupled to a respective one of the emitter-coupled transistor pairs in a respective one of the pair of Gilbert Multiplier Cells.

13. A quadraphase modulator according to claim 8 wherein each of the filters is a low pass filter having a cutoff frequency that filters frequencies above the cutoff frequency.

14. A quadraphase modulator according to claim 8 wherein the pairs of cross-coupled transistor pairs in each of the Gilbert Multiplier Cells are coupled together to provide an IQ modulated output.

15. A quadraphase modulator according to claim 12 wherein the local oscillator oscillates at mobile radiotelephone frequencies and wherein the I and Q data inputs are mobile radiotelephone data inputs.

16. A method of reducing noise in a Gilbert Multiplier Cell, the Gilbert Multiplier Cell comprising an emitter-coupled transistor pair, the output of which is coupled to a pair of cross-coupled emitter-coupled transistor pairs, the noise reducing method comprising the step of:

filtering the output of the emitter-coupled transistor pair that is applied to the pair of cross-coupled emitter-coupled transistor pairs.

17. A method according to claim 16 wherein the filtering step comprises the step of low pass filtering the output of the emitter-coupled transistor pair, to filter frequencies above a cutoff frequency.

18. A method according to claim 17 wherein the low pass filtering step comprises the steps of:

serially coupling an inductor or resistor between the emitter-coupled transistor pair and each of the pair of cross-coupled emitter-coupled transistor pairs; and

coupling a capacitor between the inductors or resistors.

19. A method according to claim 16 further comprising the steps of:

coupling a data input to the emitter-coupled transistor pair; and

coupling a local oscillator to the pair of cross-coupled transistor pairs.

20. A method according to claim 19 wherein the local oscillator is a mobile radiotelephone local oscillator and wherein the data input is a mobile radiotelephone data input.