Wireless transmitter having a modified translation loop architecture

• US 20030139148A1
• Filed: 02/24/2003
• Published: 07/24/2003
• Est. Priority Date: 09/14/1999
• Status: Active Grant

• Current Assignee: Morten Damgaard, Rahul Magoon
• Original Assignee: Morten Damgaard, Rahul Magoon
• Inventors: Magoon, Rahul, Damgaard, Morten
• Granted Patent: US 6,952,569 B2
• Time in Patent Office: Days
• US Class Current: 455/86
• CPC Class Codes: H03C 3/0966 modulating the reference clock
• CPC Class Codes: H03C 3/0983 containing in the loop a mixer other than for phase detection
• CPC Class Codes: H03L 7/1806 the frequency divider comprising a phase accumulator generating the frequency divided signal
• CPC Class Codes: H03L 7/185 using a mixer in the loop H03L7/187 - H03L7/195 take precedence
• CPC Class Codes: H04L 2027/0016 Stabilisation of local oscillators
• CPC Class Codes: H04L 2027/0018 Arrangements at the transmitter end

Abstract

A transmitter for a wireless handset having a modified translation loop architecture. The transmitter includes a VCO that generates a modulated transmit signal having a frequency f_Tx, and a modulated signal source that generates a modulated LO signal with a frequency f_LO. A mixer mixes the transmit signal with the LO signal to produce an IF signal having a frequency f_IF. A first divider divides the LO signal frequency f_LO by an integer M to generate a first comparison signal having a frequency f_CF. A second divider divides the IF signal frequency f_IF, after it is multiplied by an integer K, by an integer N to generate a second comparison signal having a frequency f_CF. The transmit and LO signal frequencies have the relationship $f_{\mathrm{Tx}}=f_{\mathrm{LO}}\frac{\mathrm{KM}\pm N}{M}.$

A phase detector coupled to the first and second comparison signals compares the phases of the signals and outputs a control voltage to the VCO proportional to any phase differences between the signals.

Claims

1. A transmitter comprising:

a voltage-controlled oscillator (VCO) that generates a transmit signal having a frequency f_Tx;

a modulated signal source that generates an LO signal modulated with audio or data information, the modulated signal having a frequency f_LO;

a mixer that mixes the transmit signal with the LO signal to produce an IF signal having a frequency f_IF,

a first divider that divides the LO signal frequency f_LO;

by an integer M to generate a first comparison signal having a frequency f_CF;

a second divider that divides the IF signal frequency f_IF;

by an integer N to generate a second comparison signal having a frequency f_CF; and

a phase detector coupled to the first and second comparison signals that compares the phases of the signals and outputs a control voltage to the VCO proportional to any phase differences between the signals.

2. A transmitter as claimed in claim 1, wherein the modulated signal source is a direct digital synthesizer (DDS).

3. A transmitter as claimed in claim 1, wherein the modulated signal source is a sigma-delta synthesizer.

4. A transmitter as claimed in claim 1, and further comprising a multiplier that multiplies the LO signal by an integer K before the LO signal is supplied to the mixer.

5. A transmitter as claimed in claim 4, wherein when f_LO>

f_Tx, the relationship between the transmit and LO signal frequency is expressed as

6. A transmitter as claimed in claim 4, wherein M is in the range of 5-15, N is in the range of 1-5, and K is in the range of 1-4.

7. A transmitter as claimed in claim 1, and further comprising a low pass filter that is coupled between the mixer and the second divider to attenuate high frequency spurs and mixing products.

8. A transmitter as claimed in claim 1, and further comprising a charge pump coupled to the phase detector that generates a control current based on the control voltage output by the phase detector, and a loop filter that receives the control current and develops a control signal that is applied to the VCO.

9. A wireless communication system in which a geographical area is divided into a plurality of cells, and a base station is provided within each of the cells for serving mobile wireless communication devices within the cell, wherein at least one of the mobile communication devices within the system incorporates a transmitter as claimed in claim 1.

10. A wireless communication system in which a geographical area is divided into a plurality of cells, and a base station is provided within each of the cells for serving wireless communication devices of the type claimed in claim 9.

11. A wireless communication device comprising:

a processor that directs the overall operation of the communication device;

a microphone for capturing audio acoustic signals and converting the acoustic signals into electric signals;

a speaker for converting electric signals into audible acoustic signals;

an antenna for wireless transmission and reception of acoustic or data signals;

a receiver for receiving audio or data information from the antenna; and

a transmitter for transmitting audio or data information over the antenna, wherein the transmitter has a modified translation loop architecture and comprises;

a voltage-controlled oscillator (VCO) that generates a transmit signal having a frequency f_Tx;

a modulated signal source that generates an LO signal having a frequency f_LO that is modulated with audio or data information;

a mixer that mixes the transmit signal with the LO signal to produce an IF signal having a frequency f_IF,

a first divider that divides the LO signal frequency f_LO by an integer M to generate a first comparison signal having a frequency f_CF,

a second divider that divides the IF signal frequency f_IF by an integer N to generate a second comparison signal having a frcquency f_CF; and

a phase detector coupled to the first and second comparison signals that compares the phases of the signals and outputs a control voltage to the VCO proportional to any phase differences between the signals.

12. A method for transmitting a modulated signal comprising the following steps:

(a) generating a modulated LO signal having a frequency f_LO;

(b) generating a modulated transmit signal having a frequency f_Tx=f_LO·

y;

(c) dividing the frequency f_LO of the LO signal by an integer M to generate a first comparison signal;

(d) mixing the LO signal with the transmit signal to generate an IF signal;

(e) dividing the frequency of the IF signal by an integer N to generate a second comparison signal;

(f) comparing the phases of the first and second comparison signals; and

(g) adjusting the frequency f_Tx of the transmit signal if necessary to correct any detected phase differences between the first and second comparison signals.

13. A method as claimed in claim 12, wherein in step (a), the LO signal is generated by a DDS or by a sigma-delta synthesizer.

14. A method as claimed in claim 12, and comprising the additional step of multiplying the LO signal by an integer K before it is mixed with the transmit signal.

15. A method as claimed in claim 12, wherein in step (b), when

16. A method for selecting a transmit frequency channel f_Tx comprising the following steps:

(a) selecting an initial transmit frequency channel f_Tx

(b) providing a multiplication factory y;

(c) selecting an LO signal having a frequency f_LO such that f_Tx=f_Loy;

(d) generating a transmit signal on the frequency channel f_Tx; and

(e) repeating step (c) to change the frequency channel, and repeating step (d) to keep the same frequency channel.

17. A method as claimed in claim 16, wherein step (b) is repeated to change the frequency channel.