Analog base band unit for a RF receiver and method for using the same

• US 7,065,336 B2
• Filed: 06/19/2002
• Issued: 06/20/2006
• Est. Priority Date: 06/19/2001
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America), U-Blox AG (u-blox Holding AG)
• Original Assignee: U-Blox AG (u-blox Holding AG)
• Inventors: Spiegel, Solon
• Primary Examiner(s): LE, LANA N
• Application Number:
  US10/173,875
• Publication Number:
  US 20030017815A1
• Time in Patent Office: 1,462 Days
• Field of Search: 455/232.1, 455/234.1, 455/234.2, 455/241.1, 455/126, 455/296, 455/244.1, 455/181.1, 330/280, 330/281, 330/282
• US Class Current: 455/244.1
• CPC Class Codes: H03G 1/04 Modifications of control circuit to reduce distortion caused by control modifications to reduce influence of variations of internal impedance of amplifying elements caused by control H03F1/08
• CPC Class Codes: H03G 3/30 in amplifiers having semiconductor devices
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence

Abstract

A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit (2) controlled by a gain control signal and a reverse path unit (6) comprising a filter unit (8) with variable time constant. A control unit (13) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances (12) and capacitances (10) in such a way that the time constant of the filter unit (8) varies essentially proportionally with the gain of the variable amplifier unit (2). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain. As the reverse path control signal (S) can be produced from different inputs selectable by selectors (20a, 20b) in the control unit (13) and due to the adaptability of the reverse path unit (6) and other features the analog base band unit is suited for the processing of signals of various types, e.g. signals pertaining to GPS and mobile telecommunication systems.

Claims

1. An analog base band unit for an RF receiver with a feedback circuit, comprising:

a variable gain amplifier unit configured to have a gain depending on a gain control signal derived from an output signal of the variable gain amplifier unit;

a reverse path unit configured to connect an output of the variable gain amplifier unit with an input of the variable gain amplifier unit; and

a control unit separate from the reverse path unit and configured to control at least one time constant of the reverse path unit dependent on the variable gain of the variable gain amplifier unit.

2. The analog base band unit according to claim 1, wherein the at least one time constant is controllable in such a way that the at least one time constant varies approximately proportionally with the gain.

3. The analog base band unit according to claim 1, wherein the variable gain amplifier unit is a variable gain amplifier chain including Gilbert cells or amplification cells comprising operational amplifiers and switching networks.

4. The analog base band unit according to claim 1, wherein the reverse path unit comprises a filter network defining the at least one time constant of the reverse path unit.

5. The analog base band unit according to claim 4, wherein the filter network comprises at least one variable resistance controllable by the control unit.

6. The analog base band unit according to claim 5, wherein the variable resistance comprises resistors, at least part of them each in series with at least one switch controllable by the control unit.

7. The analog base band unit according to claim 4, wherein the filter network comprises at least one variable capacitance controllable by the control unit.

8. The analog base band unit according to claim 7, wherein the at least one variable capacitance comprises capacitors, at least part of them in series each with at least one switch controllable by the control unit.

9. The analog base band unit according to claim 7, wherein the variable capacitance is part of a local feedback loop comprising an operational amplifier.

10. The analog base band unit according to claim 7, further comprising:

at least one switch configured to be controlled by a burst control signal to shut off the at least one variable capacitance in the reverse path unit.

11. The analog base band unit according to claim 1, wherein the control unit comprises:

a quantizer configured to compare an input signal voltage (V_c) with several reference voltages (V_r1—

V_r4) and to provide digital output signals(A₁—

A₄), each reflecting the result of one of the voltage comparisons; and

a decoder configured to process the said digital signals to provide at least part of a reverse path control signal configured to control the time constant of the reverse path unit.

12. The analog base band unit according to claim 1, wherein the control unit comprises an integrator.

13. The analog base band unit according to claim 12, wherein the integrator has a speed-up input configured to receive a speed-up signal.

14. The analog base band unit according to claim 1, further comprising:

a selector configured to connect one of a plurality of inputs of the control unit to components of the control unit.

15. The analog base band unit according to claim 14, further comprising:

a first monitoring unit connected between the output of the variable gain amplifier unit and a first input of the selector.

16. The analog base band unit according to claim 14, further comprising:

an A/D converter configured to convert the output signal of the variable gain amplifier unit to a digital signal; and

a second monitoring unit connected between the output of the A/D converter and a second input of the selector.

17. The analog base band unit according to claim 16, wherein the second monitoring unit comprises a D/A converter or a logic control unit.

18. The analog base band unit according to claim 15, wherein the first monitoring unit is a synchronous AM detector.

19. The analog base band unit according to claim 1, further comprising:

an A/D converter configured to convert the output signal of the variable gain amplifier unit to a digital signal.

20. The analog base band unit according to claim 1, further comprising:

a low pass filter unit preceding the variable gain amplifier unit.

21. A method for using an analog base band unit to process a GPS signal, the analog base band unit including

a variable gain amplifier unit configured to have a gain depending on a gain control signal derived from an output signal of the variable gain amplifier unit,

a reverse path unit configured to connect an output of the variable gain amplifier unit with an input of the variable gain amplifier unit;

and

a control unit configured to control at least one time constant of the reverse path unit dependent on the variable gain of the variable gain amplifier unit,

the method comprising;

processing the GPS signal with an acquisition bandwidth during a signal acquisition phase and with a larger tracking bandwidth during a subsequent signal tracking phase.

22. The method according to claim 21, wherein the tracking bandwidth is at least twice the acquisition bandwidth.