Apparatus for setting the tuning voltage of tunable resonant circuits

• US 6,424,824 B1
• Filed: 04/21/2000
• Issued: 07/23/2002
• Est. Priority Date: 04/21/1999
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Infineon Technologies AG
• Inventors: Stepp, Richard, Kröbel, Hans-Eberhard
• Primary Examiner(s): TO, DORIS HA
• Application Number:
  US09/556,480
• Time in Patent Office: 823 Days
• Field of Search: 455/191.1, 455/193.2, 455/178.1, 455/180.3, 455/180.4, 455/195.1, 455/196.1, 455/197.3, 455/182.1, 455/192.1, 455/290, 455/260, 455/265, 455/340, 455/339, 348/725, 348/731, 348/733, 375/316, 375/327, 375/376
• US Class Current: 455/197.3
• CPC Class Codes: H03J 1/0033 for voltage synthesis with a D/A converter
• CPC Class Codes: H03J 3/08 by varying a second parameter simultaneously with the tuning, e.g. coupling bandpass filter
• CPC Class Codes: H03J 3/32 Arrangements for ensuring tracking with variable capacitors

Abstract

A setting apparatus for setting the tuning voltage of a tunable resonant circuit has an amplification device which amplifies an oscillator tuning voltage, output by a phase locked loop, nonlinearly to produce the tuning voltage. The gain of the amplification device can be set by a digital gain control signal. The signal resolution of the setting apparatus can be controlled in different ways as a function of the gain by using two differently driven digital/analog converters.

Claims

1. In combination with a tunable resonant circuit connected to a phase locked loop, a setting apparatus for setting a tuning voltage for the tunable resonant circuit, comprising:

an amplification device receiving a digital gain control signal for setting a gain, said amplification device having a signal resolution differing as a function of the gain;

said amplification device generating the tuning voltage by nonlinearly amplifying an oscillator tuning voltage being output by the phase locked loop;

said amplification device having a first digital/analog converter and a second digital/analog converter, said first and second digital/analog converters respectively having an input for receiving analog voltages and respectively being controllable by a digital control signal;

said input of said first digital/analog converter being supplied with an analog voltage in dependence of the oscillator tuning voltage; and

said input of said second digital/analog converter being supplied with a further analog voltage provided by a constant signal.

2. The setting apparatus according to claim 1, wherein said amplification device is configured such that, as a function of the digital gain control signal, the signal resolution increases as the gain decreases.

3. The setting apparatus according to claim 2, wherein said amplification device includes an offset device, said offset device contains said second digital/analog converter and amplifies a reference voltage linearly for producing an offset voltage, the reference voltage being derived from the constant signal.

4. The setting apparatus according to claim 3, wherein said amplification device is configured such that the tuning voltage is displaceable by the offset voltage.

5. The setting apparatus according to claim 3, wherein said offset device is controllable by a digital offset control signal.

6. The setting apparatus according to claim 1, wherein said amplification device includes a voltage/current converter for converting the oscillator tuning voltage into a tuning current and a current amplification device containing the first digital/analog converter and amplifying the tuning current.

7. The setting apparatus according to claim 1, wherein said offset device includes a voltage/current converter and a current amplification device, said voltage/current converter converts a reference voltage, derived from the constant signal, into a constant current, said current amplification device amplifies the constant current for providing an amplified constant current.

8. The setting apparatus according to claim 7, wherein said amplification device includes:

a further voltage/current converter for converting the oscillator tuning voltage into a tuning current;

a further current amplification device, connected to said further voltage/current converter, containing the first digital/analog converter, and amplifying the tuning current for providing an amplified tuning current; and

a summed current node connected to said further current amplification device for summing the amplified tuning current and the amplified constant current and producing a summed current.

9. The setting apparatus according to claim 8, wherein said amplification device includes a current/voltage converter for converting the summed current and producing a tuning summed voltage as the tuning voltage.

10. The setting apparatus according to claim 1, wherein the tunable resonant circuit includes a control element having a nonlinear characteristic, said amplification device controls the control element with the tuning voltage.

11. The setting apparatus according to claim 10, wherein the control element is a variable-capacitance varactor diode, said amplification device controls the variable-capacitance varactor diode with the tuning voltage.